guide to improving the effectiveness of cement-based ... · organo-metallics ... effectiveness of...

PORTLAND CEMENTASSOCIATION

Guide to Improving theEffectiveness of Cement-BasedStabilization/Solidification

Guide to Improving theEffectiveness of Cement-BasedStabilization/Solidification

Cr

Si

Pb

Al

Cr

Si

Pb

Al

Cu

mu

lati

ve %

Lea

ched

Cu

mu

lati

ve %

Lea

ched

pHpH

EB211

PCA Serial No. 2075

Guide to Improving the Effectiveness ofCement-BasedStabilization/Solidification

This engineering bulletin was authored by: Jesse R. ConnerConner Technologies214 Field Club Rd.Pittsburgh, PA 15238USA(412) 963-6358

Edited by:Charles M. Wilk, Program Manager, Waste Management,andNatalie C. Holz, Editorial/Administrative AssistantPublic Works Department,Portland Cement Association

Published by:Portland Cement Association5420 Old Orchard Rd.Skokie, IL 60077-1083USA(847) 966-6200

© 1997 Portland Cement AssociationAll rights reserved. No part of this publication may bereproduced in any form without permission in writingfrom the publisher, except by a reviewer who wishes toquote brief passages in a review written for inclusion ina magazine or newspaper.

Printed in the United States of America

This publication is intended SOLELY for use by PROFESSIONALPERSONNEL who are competent to evaluate the significance andlimitations of the information provided herein, and who will accepttotal responsibility for the application of this information. ThePortland Cement Association DISCLAIMS any and allRESPONSIBILITY and LIABILITY for the accuracy of and theapplication of the information contained in this publication to thefull extent permitted by law.

Caution: Contact with wet (unhardened) concrete, mortar,cement, or cement mixtures can cause SKIN IRRITATION,SEVERE CHEMICAL BURNS, or SERIOUS EYE DAMAGE.Wear waterproof gloves, a long-sleeved shirt, full-length trou-sers, and proper eye protection when working with thesematerials. If you have to stand in wet concrete, use waterproofboots that are high enough to keep concrete from flowing intothem. Wash wet concrete, mortar, cement, or cement mixturesfrom your skin immediately. Flush eyes with clean waterimmediately after contact. Indirect contact through clothingcan be as serious as direct contact, so promptly rinse out wetconcrete, mortar, cement, or cement mixtures from clothing.Seek immediate medical attention if you have persistent orsevere discomfort.

Cover photo courtesy of Geo-Con, Inc.

49

PCA EB211

Guide to Improving theEffectiveness of Cement-Based

Stabilization/Solidificationby Jesse R. Conner

© Portland Cement Association 1997ISBN 0-89312-176-2

50

Guide to Improving the Effectiveness of Cement-Based Stabilization/Solidification

51

PCA EB211

Contents

I. INTRODUCTION ................................................................................................................. 1

II. PROBLEMS IN SOLIDIFICATION AND PHYSICAL PROPERTYDEVELOPMENT ................................................................................................................. 3

Setting Problems ............................................................................................................................. 3Compressive Strength Development Problems ......................................................................... 6Permeability Development Problems ......................................................................................... 7Durability Problems ....................................................................................................................... 7

III. PROBLEMS IN TARGET CONSTITUENT STABILIZATION- CHEMICAL PROPERTIES ...............................................................................................7

Metals ............................................................................................................................................... 8Organics ......................................................................................................................................... 12Organo-Metallics .......................................................................................................................... 14Soluble Salts .................................................................................................................................. 14

IV. ADDITIVES USED IN CEMENT-BASED STABILIZATION/SOLIDIFICATION ...............................................................................................................15

Metal Stabilization ....................................................................................................................... 15Immobilization of Organic Constituents .................................................................................. 20Processing and Anti-Inhibition Aids ......................................................................................... 21

V. PHYSICAL/CHEMICAL TECHNIQUES USED IN CEMENT-BASEDSTABILIZATION/SOLIDIFICATION ................................................................................ 22

Anti-Inhibition Aids..................................................................................................................... 22Physical Property Development ................................................................................................ 22Processing Aids ............................................................................................................................ 22Mixing Techniques ....................................................................................................................... 23

VI. REFERENCES ...................................................................................................................24

1

PCA EB211

Guide to Improving theEffectiveness of Cement-Based

Stabilization/Solidificationby Jesse R. Conner

counter problems in solidification caused by the wasteitself. The purpose of this Guide is to explain theseadditives and techniques, the problems encounteredin S/S that may require their use, and how they areapplied in treatment operations. The Guide is in-tended to be a practical tool. It is not a discussion ofmechanisms and theory.

There are a number of standard types of portlandcement, categorized as ASTM Types I through V, withsub-types within some of these. While there has beensome investigation of the efficacy of using differentcement types in S/S, experience to date indicates thatthis is not a common practice, and there is often littledifference between the types for S/S work. Generally,Type I is used because it is readily available every-where and is often the least expensive. However, incertain geographical areas, Type II or other types maybe more available and/or cheaper, and therefore morepractical.

The American Society for Testing and Materials(ASTM) Designation C 150, Standard Specification forPortland Cement, provides for eight types of portlandcement as follows:

Type I normalType IA normal, air-entrainingType II moderate sulfate resistanceType IIA moderate sulfate resistance, air-

entrainingType III high early strengthType IIIA high early strength, air-entrainingType IV low heat of hydrationType V high sulfate resistance

© Portland Cement Association 1997

I. INTRODUCTION

Stabilization/solidification (S/S) is a very effectivetool in the treatment of various wastes, hazardous andnon-hazardous. These wastes are commonly gener-ated in ongoing commercial and industrial opera-tions, and are also encountered in remedial activitiesat old dump sites and other contaminated media.They are usually concentrated residuals from air orwater pollution control processes, direct processstreams, or contaminated media such as soil. Gener-ally, wastes selected for S/S have already been con-centrated to the maximum extent that is economicallyfeasible, and S/S technology is used to prepare thewaste for final land disposal. Such preparation re-quires transforming the waste into a physically ac-ceptable, mechanically stable form, and convertingtoxic constituents into minimally mobile species.

The United States Environmental ProtectionAgency (EPA) considers S/S an established treatmenttechnology (USEPA, 1995). For remediation (cleanup)sites, 29 percent of source control Records of Decision(RODs) signed from 1982 through 1994 in EPA'sSuperfund program include S/S as part of the selectedremedy (USEPA, 1995). This makes S/S the mostfrequently selected technology for treating the sourceof contamination. In the treatment of industrial haz-ardous wastes, the EPA has identified S/S as BestDemonstrated Available Technology (BDAT) for 57Resource Conservation & Recovery Act (RCRA) listedwastes (USEPA, 1993).

Portland cement* alone accomplishes these objec-tives to a high degree in many instances, but somesituations (because of the waste itself, the disposalscenario, and/or the regulatory requirements) requirethe use of additives or physical/chemical techniquesto provide improved properties in the waste form or to

ISBN 0-89312-176-2

* In this Guide, the term “cement” will refer to Type I PortlandCement, unless otherwise stated.

2


The use of cement in S/S has different require-ments than its common use in concrete and mortars —for example:

• S/S has much lower strength requirements thanconcrete - normally less than 100 psi vs thou-sands of psi;

• Fast set and high early strength are usually notrequired, and may not be desirable, in S/S;

• Long term physical durability - resistance to freeze/thaw and wet/dry cycling, and immersion in water- are not normally important, although they maybe required in some specifications;

• Physical properties, in general, usually are lessimportant in S/S work than are the system'sability to immobilize hazardous constituents inthe waste;

• Concrete chemistry is complex. The chemistryof waste-cement systems is even more so, due tothe very complex nature of most wastes.Many additives have been tried out in cement-

based S/S processes. A listing of the most important,most commonly encountered additive types is givenin Table 1 (pp 28-32). Many of these have been usedcommercially or at pilot scale; some have only beentested in the laboratory. There are also a number ofproprietary additives and formulations available com-mercially, but these are generally based on the genericcategories listed here. For this reason, and because thecomposition of the proprietary products is usually notgiven, these products are not discussed as such unlessno generic equivalent is available. In addition toadditives, various physical/chemical techniques arealso used for similar purposes. Table 2 lists thesetechniques.

The problems encountered in S/S can be broadlyclassified into solidification problems, i.e., obtainingthe required physical properties in the resultant wasteform; and stabilization problems, i.e., adequately im-mobilizing the waste constituents. To more effec-tively discuss the subject, this Guide is organized inthe following manner:1. Problems in Solidification and Physical Prop-

erty Development:Setting ProblemsCompressive Strength Development ProblemsPermeability Development ProblemsDurability ProblemsThe challenges described here are those of devel-

opment of physical properties in the solidified wasteform, and the term solidification is used to describe theprocess. Table 3 (pp 33-37) lists the additives andtechniques that are most important in solidification,or have been proven for this use in actual applications.Other possible solutions to these problems are dis-cussed and referenced in the text.2. Problems in Target Constituent Stabilization -

Chemical Properties:MetalsOrganicsOrgano-MetallicsSoluble SaltsThe challenges described here are those of devel-

opment of chemical properties, i.e., immobilization ofcertain species, in the stabilized waste form, and theterm stabilization is used to describe the process. Tables7 and 9 (pp 38-39, 43-44) list the more importantadditives and techniques used in stabilization, or thosethat have been proven for this use in actual applica-tions. Other possible solutions to these problems are

TECHNIQUE EFFECT RELATIVECOST

Aeration: Alteration of biological status; removal ofinterfering volatiles

Low

Temperature Control: Acceleration of reaction rate to counter retardingeffect; improvement of leaching characteristics

Low

Viscosity/PumpabilityAlteration:

Important for some applications where pumping oftreated waste before curing is necessary

Low to Moderate

Humidity Control: Prevention of excessive drying during curing LowDewatering: Removal of excess free water Low to ModerateAir Entrainment: Addition of air into the structure to provide better

freeze/thaw durabilityLow

Mixing Type and Degree:Ex-Situ Prevent over-mixing, assure adequate mixing LowIn-Situ Necessary for proper slurry-grout formulation Low to Moderate

Table 2. Physical/Chemical Techniques Used in Cement-based S/S

3

PCA EB211

discussed and referenced in the text.3. Additives Used in Cement-based Stabilization/

Solidification:Metal StabilizationImmobilization of Organic ConstituentsProcessing and Anti-Inhibition AidsAdditives of commercial importance are dis-

cussed individually, or by chemical type, in moredetail.4. Physical/Chemical Techniques Used in

Cement-based Stabilization/Solidification:Anti-Inhibition AidsPhysical Property DevelopmentProcessing AidsMixing TechniquesVarious physical/chemical techniques other than

the use of additives are discussed in more detail.A great deal of attention has been paid to “interfer-

ence mechanisms” in cement-based systems. Consider-able experimental work was done for the EPA at the U.S.Army Corps of Engineers Waterways Experiment Sta-tion (WES) on the causes, effects, and cures for thisproblem (United States Environmental ProtectionAgency, 1982; U.S. Army Corps of Engineers Water-ways Experiment Station, 1990; Battelle Columbus,1993). Conner (1990) describes the various additivesused in S/S and summarizes the chemical factors thataffect solidification. Other individual investigators andsummaries (Coté, 1986; Eaton et al., 1987; El-Korchi etal., 1990; Spence, 1992) have contributed to the knowl-edge base on this subject, and the reader is referred tothese sources for further detailed information.

II. PROBLEMS IN SOLIDIFICATIONAND PHYSICAL PROPERTYDEVELOPMENT

There are many factors which retard, inhibit andaccelerate the setting and curing of S/S systems.Some also affect the final strength, permeability andother physical properties of the fully cured S/S prod-uct. Others affect chemical properties, which will bediscussed in Section III, Problems in Target Constitu-ent Stabilization - Chemical Properties. Many of thecompounds, materials and factors which are known tohave such solidification effects were described byConner (1990), Battelle Columbus (1993), U.S. ArmyEngineer Waterways Experiment Station (1990), U.S.Army Engineer Waterways Experiment Station (1990),and Eaton et al. (1987); some are general knowledge inthe field of cement technology (Portland Cement As-sociation, 1979).

The effects are many and varied, but in spite of ourknowledge about them, these effects are not simple to

predict and sort out from knowledge of the composi-tion of the waste, even when that infomation is avail-able. Most often, a number of species are present in thewaste, sometimes with opposing effects. The samespecies may have opposite effects depending on con-centration. This latter phenomenon has been foundwith calcium chloride, calcium sulfates, sodium hy-droxide, sodium silicate, lead, copper and tin salts,amines and hexachlorobenzene. For example, ionexchange can inhibit or retard S/S reactions by remov-ing calcium from solution, preventing it from enteringinto the necessary cementitious reactions (Conner,1990). It can also accelerate the process by removinginterfering metal ions from solution. Which occursmay depend on the selectivity of the ion exchangematerial. Other examples are metals that may retardand inhibit the reactions by substituting for calcium inthe cementitious matrix, which may explain the effectof magnesium in dolomitic lime and lime products.Certain substances are natural or synthetic complexingagents which remove calcium from availability in thesetting and curing reactions. On the other hand,alcohols, amides and specific surfactants can aid inwetting solids and dispersing fine particulates and oilwhich interfere with reactions by coating the reactingsurfaces. Flocculants can also serve this purpose.Some of these materials and techniques are discussedin sections IV and V.

Specific problems and solutions which have beenused are discussed below. They are also summarizedand tabulated in Table 3.

Setting Problems

Will not set. Waste form remains non-solid even aftercuring for up to 28 days.Cause:

Fine particulates coating cement particles, pre-venting or slowing reaction: silt (Kitsugi, 1976)(Kitsuge and Kozeki, 1976), clay (Kitsugi, 1976)(Kitsuge and Kozeki, 1976), colloidal matter(Kitsugi, 1976) (Kitsuge and Kozeki, 1976)

Possible Solution:Use surface active agents: wetting agents(amides, alcohols), dispersants (carboxylic ac-ids, carbonyls, sulfonates), flocculants (amines,iron salts, magnesium salts, silica) to removeand coagulate fine particulates

Cause:Anaerobic conditions

Possible Solution:1. Aerate2. Add oxidizer3. Add lime, soluble silicate (Conner, 1990)

4


(Conner, 1974) (USEPA, 1982)4. Add biocide — commercial products are

availableCause:

Calcium removers in the waste: phosphatesPossible Solution:

Replace lost calcium

Sets, but does not harden. Waste form undergoes aninitial set, but does not harden further even aftercuring for up to 28 days.Cause:



Cause:Anaerobic conditions



availableCause:

Calcium removers in the waste: phosphates,glucose

Possible Solution:Replace lost calcium

Set is retarded. Waste form set and hardening areretarded, but both take place more or less normallyafter curing for up to 28 days. Set retardation may lastfor a week or more.Cause:



Cause:Presence of sugar, sugar derivatives (PortlandCement Association, 1979) (Kitsugi, 1976)(Kitsuge and Kozeki, 1976)

Possible Solution:1. Add more sugar - 0.2%; an optimum level of

sugar may be difficult to achieve. (PortlandCement Association, 1979)

2. Add a sorbent: clay, flyash, diatomaceousearth, carbon

3. Chemical oxidation with potassium perman-ganate, sodium persulfate, calcium orsodium hypochlorite

Cause:Presence of phosphates (Kitsugi, 1976) (Kitsugeand Kozeki, 1976)

Possible Solution:Add calcium ion in excess (cement kiln dust,hydrated lime)

Cause:Presence of sulfur (Battelle Columbus, 1993)

Possible Solution:None established

Cause:Presence of bicarbonates of sodium and potas-sium (Portland Cement Association, 1979)

Possible Solution:Pretreat with acidic material to decompose bi-carbonate

Cause:Presence of other chemical interference -inorganics, general (U.S. Army Engineer Water-ways Experiment Station, 1990) (Battelle Co-lumbus, 1993) (Cullinane et al., 1986) (Cullinaneet al., 1987); presence of certain inorganic salts(Cullinane et al., 1986) (Cullinane et al., 1987):salts of magnesium (Battelle Columbus, 1993),tin (Battelle Columbus, 1993), zinc (Battelle Co-lumbus, 1993) (ASTM, 1985) (Cullinane et al.,1987), arsenic (El-Korchi, 1990), chromium (El-Korchi, 1990), cadmium (El-Korchi, 1990), cop-per (Battelle Columbus, 1993) (Cullinane et al.,1987) and lead (Battelle Columbus, 1993) (El-Korchi, 1990) (Cullinane et al., 1987), sodiumiodate (Battelle Columbus, 1993), sodium phos-phate (Battelle Columbus, 1993), sodium arsen-ate (Battelle Columbus, 1993), sodium borate(Battelle Columbus, 1993), sodium sulfide(Battelle Columbus, 1993), sodium hydroxide(Cullinane et al., 1987), sodium sulfite (Cullinaneet al., 1987)

Possible Solution:Add sulfates (Kitsugi, 1976) (Harada et al., 1977),

5

PCA EB211

soluble silicates (Conner, 1990) (Conner, 1974)(USEPA, 1982), aluminates (Kitsuge and Kozeki,1976) (Harada et al., 1977), phosphates (Carlson,1987), hydroxylated organic acids (Bonnel andHevanee, 1972), glycols (U.S. Patent 3,642,503)(Harada et al., 1977), amines (Harada et al.,1977), iron compounds (for sulfides, tin lead,arsenates) (Conner, 1990) (Electric Power Re-search Institute, 1996), ASTM set accelerators(U.S. Army Engineer Waterways ExperimentStation, 1990), other organics.

Cause:Presence of other chemical interference - chelat-ing agents (Battelle Columbus, 1993) (U.S. ArmyEngineer Waterways Experiment Station, 1990):ethylenediaminetetracetic acid (EDTA),nitrilotriacetic acid (NTA), lignins, tannins, glu-cose, starch

Possible Solution:See possible solutions above under inorganics

Cause:Presence of other chemical interference - organ-ics, general: oil, grease, tars, resins, carbohy-drates, phenol, trichloroethylene,hexachlorobenzene, coal, lignite, general organ-ics (Cullinane et al., 1987) (El-Korchi, 1990)(Eaton, 1987) (Cullinane et al., 1986) (BattelleColumbus, 1993) (U.S. Army Engineer Water-ways Experiment Station, 1990)

Possible Solution:1. Add sorbent (cement kiln dust, clays, lime,

limestone, flyash, carbon)2. Evaporate VOCs3. Chemical oxidation with hydrogen

peroxide, potassium permanganate, sodiumpersulfate, calcium or sodium hypochlorite

4. See also possible solutions above underinorganics

Cause:Mild anaerobic conditions



availableCause:

Insufficient cure time

Possible Solution:Cure longer

Cause:General retardation of set

Possible Solution:Add calcium chloride (<2%) (Blake, 1975), so-dium silicate (Conner, 1990) (Conner, 1974), lime(Conner, 1990)

Supernatent liquid on surface, or softer surface layer,after setting. Large differences in specific gravitybetween the waste and the reagent result in a tendencytoward phase separation. Most reagents used in S/Shave particle specific gravities much larger than thewaste density as a whole: >2.0 versus 1.0 to 1.5 in mostsystems. Although reagent particle size is generallysmall, it is not usually sufficient to make up for thisdifference, and some settling will occur unless viscos-ity is sufficient to prevent phase separation until theinitial setting reaction can physically immobilize allcomponents in place. Alternatively, sufficient reagentcan be added to quickly take up all the free water, or aviscosity-increasing agent can be added. Rheologicalagents which accomplish the latter technique are avail-able, but add significantly to the cost of the process andsometimes can interfere with the reactions which mustsubsequently take place for proper curing. Gellantssuch as soluble silicates do this by causing an almostimmediate thickening or gelling reaction between freecalcium ion from the cement and the silicate, creatingan elastic silica gel which does not interfere withcement or pozzolanic reactions.Cause:

Set is too slowPossible Solution:

Add set accelerator: calcium chloride (<2%)(Blake, 1975) (U.S. Army Engineer WaterwaysExperiment Station, 1990); sulfates, soluble sili-cates (Conner, 1990) (Conner, 1974), aluminates(Kitsuge and Kozeki, 1976) (Harada et al., 1977),hydroxylated organic acids (Bonnel andHevanee, 1972), or glycols (U.S. Patent 3,642,503)(Harada et al., 1977); amines (Harada et al.,1977); other organics

Cause:Water content is too high

Possible Solution:1. Dewater. Decant water; filter raw waste2. Add sorbent3. Add bulking agent4. Add low-cost, reactive bulking agent:

cement kiln dust, flyash, blast furnace slag(Chudo et al., 1981)

Cause:Viscosity of system is too low

Possible Solution:Increase viscosity of system, using gelling agentor sorbent: soluble silicates, flyash, clay (dried or

6


expanded), organic sorbents (wood chips, corncob, etc.)

Sets too rapidly for satisfactory processing. Somewastes contain, or act as, cement setting accelerators,causing the set to be so rapid that the cement cannot beuniformly mixed into the waste in the desired treat-ment scheme, or the waste cannot be handled asrequired after mixing. The former problem is espe-cially important in ex-situ batch mixing, and in somein-situ processes.Cause:

Presence of accelerating agents: sulfates; solublesilicates, aluminates, phosphates; hydroxylatedorganic acids, glycols, other organics; ion ex-change material

Possible Solution:1. Use a proprietary, concrete set retarder2. Add zinc, copper or lead oxide/hydroxide;

calcium chloride (>4%); magnesium andtin salts; phosphates, chlorides, sugars(Metcalf and Ellers, 1980), clays

3. Lignosulfonic acid salts and derivatives,hydroxylated carboxylic acids, polyhydroxycompounds (ASTM C494, Types A and B)(U.S. Army Engineer Waterways Experi-ment Station, 1990)

Cause:Presence of carbonates and bicarbonates of so-dium and potassium (Portland Cement Associa-tion, 1979)

Possible Solution:Decompose or neutralize with acid or acidicadditive

Cause:Presence of sugar at high level (0.2% or more)(Portland Cement Association, 1979)

Possible Solution:1. Add a retarder (see above)2. Chemical oxidation with hydrogen


Compressive Strength DevelopmentProblems

Insufficient unconfined compressive strength. Thefinal waste form has insufficient unconfined compres-sive strength (ASTM D-2166, D-1633) for the intendeddisposal scenario, even after full curing.Cause:

Insufficient cement to develop desired strength

Possible Solution:Use more cement

Cause:Presence of salts of manganese, tin, zinc(Cullinane et al., 1987), copper (Cullinane et al.,1987) and lead (Portland Cement Association,1979) (Cullinane et al., 1987)

Possible Solution:Add sulfates (Kitsugi, 1976) (Harada et al., 1977),soluble silicates (Conner, 1990) (Conner, 1974),aluminates (Kitsuge and Kozeki, 1976) (Harada etal., 1977), phosphates (Carlson, 1987), hydroxy-lated organic acids (Bonnel and Hevanee, 1972),glycols (U.S. Patent 3,642,503) (Harada et al., 1977),amines (Harada et al., 1977), other organics.

Cause:Presence of sodium sulfide (Portland CementAssociation, 1979), sodium sulfite (Cullinane etal., 1987) and sodium hydroxide (high concen-trations) (Cullinane et al., 1987)

Possible Solution:1. Chemical oxidation with hydrogen


2. Neutralization (sodium hydroxide)3. Add iron salts: ferrous sulfate to immobilize

sulfide ionCause:

Presence of sugar (Portland Cement Associa-tion, 1979)

Possible Solution:Chemical oxidation with hydrogenperoxide, potassium permanganate, sodiumpersulfate, calcium or sodium hypochlorite

Cause:Presence of algae (Portland Cement Associa-tion, 1979)

Possible Solution:1. Add sorbent (clays, limestone, flyash,

carbon)2. Chemical oxidation with hydrogen


3. Add lime4. Add a biocide — commercial products are

availableCause:

Anaerobic conditionsPossible Solution:

1. Aerate2. Add oxidizer3. Add lime, soluble silicate (Conner, 1990)


available

7

PCA EB211

Cause:Presence of oils (Portland Cement Association,1979) and grease (Cullinane et al., 1987)

Possible Solution:1. Add sorbent: bentonite (Gilliam and Wiles,

1996, p. 584), limestone, flyash (Gilliam andWiles, 1996, p. 584), carbon

2. Evaporate VOCs3. Chemical oxidation with hydrogen


4. Add quicklime (CaO)5. Add phosphorus pentoxide and a stearate

(Takashita, 1979)Cause:

Water content is too highPossible Solution:

Dewater, use a water reducing agent (ASTM C-494 Types A, D, F and G) if applicable (U.S. ArmyEngineer Waterways Experiment Station, 1990)

Permeability Development Problems

High Permeability. Permeability of the final wasteform is too high (SW846, Method 9100).Cause:

Incomplete curing of waste formPossible Solution:

Cure for at least 28 days before testingCause:

Insufficient cement to develop the require ma-trix

Possible Solution:Use more cement

Cause:Waste has natural high permeability

Possible Solution:1. Add bentonite clay (Conner, 1990)2. Add hydrophobizing agent (Conner, 1986)3. Add a stearate (Portland Cement Associa-

tion, 1974)(Takashita, 1979)4. Add a pore filling and/or hydrophobic

organic polymer compatible with cement5. Develop better microstructure with flyash

((Gilliam and Wiles, 1996, p. 251), slag(Gilliam and Wiles, 1996, p. 251), silica fume(Gilliam and Wiles, 1996, p. 135)

Durability Problems

Poor durability, stability, or strength. Final wasteform has poor freeze-thaw or wet-dry durability

(ASTM D-4842-90, D-4843-88), poor immersion stabil-ity (10 CFR 61, Regulatory Guide, May 1983), or poorstrength (see Compressive Strength DevelopmentProblems Sections above).Cause:

Insufficient cementPossible Solution:

Add more cementCause:

Poor microstructurePossible Solution:

1. Add flyash ((Gilliam and Wiles, 1996,p. 251), slag (Gilliam and Wiles, 1996,p. 251), silica fume (Gilliam and Wiles, 1996,p. 135), etc. to improve microstructure

2. Air entrainment (U.S. Army EngineerWaterways Experiment Station, 1990)

Cause:Excessive porosity, due to non-optimum watercontent

Possible Solution:1. Modify water content by addition or

removal2. Add bulking agent or water absorber3. Add a pore filling and/or hydrophobic

organic polymer compatible with cement4. Add wood resins, proteinaceous materials,

synthetic detergents (ASTM C-260) (U.S.Army Engineer Waterways ExperimentStation, 1990)

Cause:Presence of large amounts of soluble salts: sul-fates, nitrates, chlorides

Possible Solution:For treatment of waste in saline or brackishenvironments, as near a coast, some projectshave specified Type II or Type V sulfate resistantcements

III. PROBLEMS IN TARGETCONSTITUENT STABILIZATION -CHEMICAL PROPERTIES

In contrast to solidification, there is only one basicproblem in stabilization — the degree of immobiliza-tion of the target constituents of concern: metals,organics, organo-metallics, and salts. In most cases,these are entities that are hazardous to human healthand the environment. The solutions to the problem,however, depend on the particular inorganic or or-ganic compound of interest. Therefore, discussion ofadditive use in stabilization is organized along thelines of particular chemical species.

8


Metals

The stabilization of metals in hazardous wastes hasbeen done at remedial operations and at fixed treat-ment sites in the U.S. for more than 20 years. Manyprivate companies have been running stabilizationoperations for metals at RCRA Treatment, Storageand Disposal Facilities (TSDFs) for decades, treatingliterally thousands of different waste streams. Gov-ernment and private research and testing laboratorieshave done tens of thousands of treatability studies todevelop formulations for all RCRA metals, as well asfor the more recent constituents of concern: copper,nickel, zinc, antimony, beryllium, and vanadium.

Table 4 is a list of metals which are regulated byfederal or state agencies in the United States. These arethe metals of primary concern in stabilization technol-ogy, and are commonly referred to as the “toxic met-als” or “RCRA metals.” Those marked with an aster-isk are the Toxicity Characteristic (TC) metals forwhich EPA established required treatment levels us-ing the Toxicity Characteristic Leaching Procedure(TCLP) (USEPA, 1990). The other metals have beencontrolled under the Land Disposal Restrictions (LDRs)(USEPA, 1985), the Universal Treatment Standards(UTS) (USEPA, 1994), or state regulatory systems.

Table 5 lists many of the types of metal com-pounds that may be found in waste streams. Theasterisk denotes the more common species. Thislisting does not include anions containing the toxicmetals themselves, or individual organic complexes.

More is known about metal stabilization thanabout the stabilization, destruction and immobiliza-tion of any other hazardous constituent group en-countered in stabilization technology. The mobility ofthese metals in a landfill situation, as measured byleaching tests such as the TCLP, is greatly reduced inthe vast majority of treatment scenarios by simplestabilization with cement-based S/S systems, with orwithout additives or special techniques. Some metalsand metal species may require more complex formu-lations or pre-treatment. Species that have been en-countered in actual wastes are listed in Table 6. Inaddition, non-additive methods such as temperatureadjustment (Vejmelka et al., 1985) and control of free

water may be used. Most of these special situationsrequire either changing the valence state of the metal,or dealing with metal complexes. Methods for reduc-ing mobility of these species are discussed under thefollowing individual metal headings, and are summa-

Table 4. Toxic Metals

Antimony Lead* VanadiumArsenic* Mercury* ZincBarium* NickelBeryllium Selenium*Cadmium* Silver*Chromium Thallium * TC Metals

Table 5. Metal Species

Acetates Ferrocyanides Phosphates*Bromides Fluorides Silicates*Carbonates* Hydroxides* Sulfates*Chlorides * Iodides Sulfides*Citrates Nitrates* Organic ComplexesCyanides OxalatesFerricyanides Oxides

Table 6. Potential Problem Metal Species

Arsenic trisulfide - As2S3 Organo-mercury compoundsTrivalent arsenic Nickel cyanide

compounds -As+3 Organo-nickel compoundsOrgano-arsenic compounds Hexavalent seleniumHexavalent chromium and its compounds - Se+6

and its compound - Cr+3 Finely divided elementalMetallic lead metalsOrgano-lead compoundsMetallic mercury

rized and tabulated in Table 7 (pp 38-39); metals ormetal species that are adequately stabilized by cementalone, and do not require additives, are shaded in thetable. Table 8 (pp 40-42) provides a general summaryof actual, commercial additive utilization for variousmetals and metal species. It should be noted thatflyash or bedash is often used in commercial pro-cesses, especially at TSDFs, for a variety of reasonsother than metal stabilization, but it is difficult toseparate out the actual purpose in most cases. Addi-tives per se will be discussed in Section IV. Followingare brief discussions of the various metals of concern,and their stabilization treatment.

Antimony. Antimony may exhibit a valence of -3,+3,or +5, and is classified as a non-metal or metalloid; thetrivalent state exhibits metallic characteristics. It formsa number of inorganic and organic compounds, manyof complex structure. Until the LDRs, antimony com-pounds in wastes were hazardous only under Califor-nia regulations, with a reasonably high allowableleaching level. Very little information is available onstabilization methods (although leachate analyses of-ten include antimony) and problems with antimonystabilization were rarely, if ever, encountered. An

9

PCA EB211

internal study at Chemical Waste Management (Chemi-cal Waste Management, 1992) on K061 waste (ElectricArc Furnace Dust) and soil spiked with antimony chlo-ride showed that simple stabilization with cement pro-vided excellent reduction in mobility, with leachinglevels below 0.11 mg/l, the Level of Quantification(LOQ) for analysis. Higher cement content (up to mixratios of 1.0 at least) did not increase leachability, indi-cating that antimony is not sensitive to over-treatment.

Arsenic. Arsenic is also classified chemically as anonmetal or metalloid, although it is grouped with themetals for most environmental purposes. Its principalvalence states are +3, +5 and -3. The compounds ofarsenic listed below are those commonly found inwaste materials.

Arsenic trioxide, As2O3Cacodylic Acid and Sodium CacodylateMetal Arsenates

Ca3(AsO4)4PbHAsO4 - acid lead arsenatePb4(PbOH)•(AsO4)3

•H2O - basic lead arsenateCu(CuOH)AsO45ZnO•2AsO5

•4H2ONa2HAsO4MnHAsO4

Metal ArsenitesSodium arsenite, NaAsO2Copper acetoarsenite,

(CH3CO2)2Cu•3Cu(AsO2)O3, or Paris greenArsenic Sulfides

Arsenic trisulfide, As2S3Arsenic sulfide, As4S4Arsenic pentasulfide, As2S5

The oxide is amphoteric and thus is soluble in bothacids and bases. Arsenites are often present as com-plexes such as Scheele’s green, CuHAsO3, and copperacetoarsenite described previously. Arsenates derivedfrom the arsenic acids are oxidizing agents. Arsenicforms the three sulfides described above. The trisulfideis soluble only in bases. It is often encountered in wastefrom phosphoric acid manufacture where it is precipi-tated from strong acid solution. This property is anunusual one for metal sulfides, which are usually de-composed by acids, but are stable and have low solubil-ity in bases.

Normally, traditional chemical stabilization pro-cesses are able to immobilize arsenic in contaminatedsoils, incinerator ashes and other wastes to well belowregulatory requirements (Conner and Lear, 1992). Cer-tain arsenical species—arsenic trisulfide and organicarsenicals, primarily—are very difficult to stabilize byconventional, chemical means. One solution to thisproblem has been the use of alkaline oxidation, hydro-

lyzing the sulfide and oxidizing As+3 to As+5 withsubsequent precipitation as calcium arsenate, a rela-tively insoluble species (Conner, 1993a). Another is theuse of ferrous sulfate as an additive (Electric PowerResearch Institute, 1996). Young (1979) reported im-proved resistance to arsenic leaching by the addition ofcalcium and manganese chlorides, sulfates, and ac-etates. The organic arsenical problem is discussedbelow in the section on Organo-Metallic Compounds.

Barium. Barium is classed as an alkaline earth metal(Group IIA of the periodic table), along with calciumwhose chemical behavior it resembles. Its valence stateis +2. Barium is present in many waste streams, and isalso easily stabilized to well below RCRA levels. Bariumleaching is not a problem in any experience to date.Even with extremely high barium wastes, it is suffi-cient to add sodium sulfate or gypsum to any standardstabilization formulation to precipitate barium as thesulfate. Very often, even drinking water standards canbe achieved in the leachate.

Beryllium. Beryllium, along with thallium and zinc,appeared in the RCRA Listed Waste K061 LDRs. Itrarely has been analyzed for in other non-wastewaterhazardous wastes, so there is little data on its stabiliza-tion. In one study (Chemical Waste Management,1992), K061 waste and soil spiked with beryllium wereeasily stabilized to below LOQ (<0.01 mg/l) with ce-ment alone, with greater than three orders of magni-tude reduction in TCLP leachability. Higher cementcontent (up to mix ratios of 1.0 at least) did not increaseleachability, indicating that beryllium is not sensitiveto over-treatment.

Cadmium. Cadmium is a Group IIB element, with onlyone valence state for all practical purposes (+2). Cad-mium compounds present in wastes may include:

Cadmium Arsenides, Antimonides, and Phos-phides

Cadmium BoratesCadmium CarbonateCadmium ComplexesCadmium HalidesCadmium HydroxideCadmium NitrateCadmium OxideCadmium Selenide and TellurideCadmium SulfateCadmium SulfideCadmium TungstateUnlike zinc, the cadmium ion is not very amphot-

eric and its hydroxide, Cd(OH)2, has quite low solubil-ity in an alkaline medium. In view of the low solubility

10


of most cadmium species in alkaline systems, and thenon-amphoteric nature of Cd, the primary treatmentmethod has been precipitation with nearly any alkali,including cement and lime. In the presence ofcomplexing agents, such as cyanide, the cadmium ionwill not precipitate (Weiner, 1967). It is then necessaryto destroy the cyanide complex, usually by alkalinechlorination, which precipitates the Cd as the hydrox-ide. Oxidation of cyanide by hydrogen peroxide is alsoreported to break the complex and precipitate CdO. Inmost cases, even the lowest LDR level can be met withstandard stabilization formulations, especially cement-based formulations. High pH caused by over treat-ment (excessive mix ratios) is not a problem withcadmium as it is with chromium and lead.

Chromium. Chromium belongs to Group VIB of theperiodic table. It has three valence states, +2, +3, and+6, but the latter two are the most common. Cr+6 isacidic, forming chromates (CrO4)

-2 and dichromates(Cr2O7)

-2, while the other valence states are basic. Themajor chromium compounds encountered in stabili-zation work are composed of Cr+3 and Cr+6 valencestates in the following compounds:

Pigments - lead chromate, chromium oxide greensChromium sulfateChromated copper arsenate (CCA)Chromium lignosulfonatesSodium or potassium dichromateChromic acidAmmonium dichromateChromic nitrateCr+6 compounds are usually reduced to the triva-

lent state and precipitated with bases. The resultantCr(OH)3 is the form in which the majority of chro-mium is encountered in stabilization treatment. Be-cause of its low solubility, fixation of chromium as thisspecies has not been a problem, even though chro-mium is nearly ubiquitous in waste streams. As longas chromium is speciated as Cr+3, stabilization of char-acteristic wastes to the Toxicity Characteristic level iseasy if the final leachate pH is maintained above 6.0. Inwastes, this generally requires cement mix ratios above0.2, or cement kiln dust above 0.5, the latter dependingheavily on the alkalinity of the dust.

The hexavalent form is encountered in a numberof wastes, either by mixing of untreated chromatesolutions with wastewater treatment sludge or be-cause it is intrinsic to the waste, as in some incineratorresidues and in wood-treating wastes. It is also amajor problem where soil has been contaminatedwith chromate or chromic acid solutions, a frequentsituation with old plating operations. The classicalway to manage Cr+6 has been a two-step process:

reduce the chromium to the trivalent state and thenprecipitate it as the hydroxide. However, especiallywhen the Cr+6 level is low, reducing agents such asferrous sulfate, sodium metabisulfite, or sodium hy-drosulfite may be added directly to the cement orcement kiln dust based stabilization system.

Chromium is amphoteric, and so exhibits mini-mum solubility at around pH 9, with increasing leach-ability at higher pH. However, empirical measure-ments in cement-based stabilization systems(Cote1986) have shown that leachability of Cr+3 compoundsdoes not increase substantially below pH 12+. There-fore, over-treatment is normally not a problem andhigh reductions in mobility of Cr+3 compounds can beachieved at almost any mix ratio.

Lead. Lead is a member of Group IVA of the periodictable. It has two valence states, +2 and +4, with the +2state being the most common. Pb+4 compounds areregarded as being covalent, while Pb+2 compounds areprimarily ionic. Lead is amphoteric and forms soluble,anionic plumbites and plumbates as well as bothcations. Lead compounds encountered in stabiliza-tion include:

HalidesOxidesSulfideSulfateNitrateAcetatesCarbonatesSilicatesOrganolead CompoundsIn lead stabilization, pH control is more impor-

tant than with most metals. Minimum lead leaching innearly all stabilization systems occurs when the pH ismaintained between about 8 and 10 in the leachate,but substantial reduction in leachability can be at-tained in most instances up to pH 12. In most wastes,lead is easily stabilized to the TC requirements, andleaching reductions of two or more orders of magni-tude are common in cement-based systems. Researchon stabilization of F006 and, especially, K061 wastes,has often focussed on lead, and as a result there arelarge data bases on lead stabilization. In some cases,remedial projects require the achievement of very lowlead levels, sometimes at the drinking water level.This may necessitate the use of additives such ascarbonates or sulfur compounds.

The use of calcium carbonate has become com-mon practice in treatability studies on lead-contami-nated soils and many other wastes. The function ofcarbonate is not clear. It may result in the formation oflead carbonate or basic lead carbonate

11

PCA EB211

[Pb3(CO3)2(OH)2], which are much less soluble thanlead hydroxide. It also buffers many systems to moremoderate pH, but simple buffering action does notexplain all of the effects of calcium carbonate. Be-cause they are inexpensive, cannot cause over-treat-ment, and are applicable to a very wide range of lead-contaminated wastes, cement-calcium carbonate for-mulations are often the best overall choice for lead-contaminated soil and debris treatment.

Mercury. Mercury salts exist in two valence states, +1and +2. Many mercury compounds are volatile; theyare also labile and easily decomposed by light, heat,and reducing agents, even weak reducing agentssuch as amines, aldehydes, and ketones. Because oftheir covalent nature and ability to form a variety oforganic complexes, mercury compounds have un-usually wide solubility. Compounds that may befound in wastes are:

Mercuric ChlorideMercuric OxideMercuric NitrateMercuric SulfateMercuric SulfideOrganomercury CompoundsMercury concentrations found in most wastes

are quite low, and substantial reduction in mercuryleachability is easily accomplished in most stabiliza-tion processes. Even at higher levels—100 mg/kg ormore—stabilization is very effective. If necessary,lower leachability—to the 0.01 mg/l level or below—can be attained by additions of inorganic or organicsulfides or elemental sulfur. The only area wherestabilization difficulty might be encountered is whereelemental mercury or organo-mercury compoundsare present, but this appears to be quite uncommon.

Nickel. Nickel is a Group VIII transition element,along with iron and cobalt. It forms compounds inwhich the nickel atom has the oxidation states of -1, 0,+1, +2, +3 and +4. The Ni+2 valence state, however,represents the majority of all nickel compounds.Nickel is not amphoteric, but the ease with which itforms coordination complexes at high pH gives it theappearance of being so. Ni(OH)2 has low watersolubility, which accounts for the adequate fixation ofnickel in most wastes by simple pH control. Nickelcompounds encountered in wastes include:

Nickel OxideNickel SulfateNickel NitrateNickel HalidesNickel CarbonateNickel Hydroxide

Nickel FluoroborateNickel CyanideNickel SulfamateNickel SulfideWhere proper pH control is exercised, there is

usually no difficulty in fixing nickel, but more recentLDR requirements sometimes are difficult to meetwithout additives. The simplest approach in thissituation is the addition of organo-sulfur compounds.The most common difficulties that are encounteredhave been caused by the presence of complexed nickel,either a cyanide complex or an organo-complex, espe-cially the latter (see organo-metallics below). Non-complexed nickel species do not appear to be sensitiveto over-treatment.

Selenium. Selenium is next to sulfur in group VIA,and between arsenic and bromine in period 4 of theperiodic table. It forms compounds, both inorganicand organic, similar to those of sulfur. Its valencestates are -2, 0, +4, and +6. The most importantcompounds of selenium are halides, oxides, oxyacids(H2SeO3 - selenious, and H2SeO4 - selenic), and se-lenides. Selenates, if known to be present at highlevels, would pose a potential leaching problem be-cause of their solubility. Possible treatment would beeither reduction to the selenite form, or precipitationwith strontium to produce the low solubility stron-tium selenate.

Rarely is selenium found in industrial wastes inappreciable amounts, and selenium leaching abovethe RCRA level of 1.0 mg/l, even from the untreatedwaste, is seldom encountered. In stabilization-treatedwastes, leaching is usually below detection limits,with substantial reductions in mobility. Selenium athigh levels or in some complex species that mightprove difficult to stabilize have not been reported inthe literature (Conner 1990). However, the selenateion appears to have been encountered in at least oneinstance (Conner, 1994). Ferrous sulfate, probably asa co-precipitant, is believed to be useful for selenates,and precipitation as strontium selenate has been pro-posed. In most instances, selenium stabilization withsimple cement or pozzolan systems appears to bestraightforward.

Silver. Silver is a noble metal with only one normalvalence state. Most of its compounds are relativelyinsoluble, especially the halides, cyanide, sulfide, andthiocyanate. Because of the value of silver, and theease with which most dissolved species can be pre-cipitated by chloride ion, fixation of silver in stabiliza-tion systems is rarely a problem since very little isnormally present. Leaching results are normally be-

12


low regulatory levels. If wastes with high silver levelsare encountered, very low leachabilities can be at-tained by the simple expedient of adding chloride ion,either as sodium chloride or hydrochloric acid. Thishas been done at TSDFs.

Thallium. Thallium is a member of group IIIA of theperiodic table with boron, aluminum, gallium, andindium (Cote, 1986). Unlike the others, it exists in bothmonovalent and trivalent forms, with the former beinggenerally the most stable. It is used in alloys and inelectrical applications. Virtually nothing appears inthe literature on stabilization treatment or stabilizationof thallium. In the treatability study referenced previ-ously (Chemical Waste Management, 1992), K061 wasteand soil spiked with thallium were stabilized to lessthan 1.0 mg/l with cement alone, or nearly two ordersof magnitude reduction in TCLP leachability. Thehigher the cement content (up to mix ratios of 1.0 atleast) the lower the leachability. This indicates thatthallium is not sensitive to over-treatment.

Vanadium. In the treatability study referenced previ-ously (Chemical Waste Management, 1992), K061 wasteand soil spiked with vanadium were easily stabilizedto less than 0.1 mg/l with cement alone, or nearly threeorders of magnitude reduction in TCLP leachability.The higher the cement content (up to mix ratios of 1.0at least) the lower the leachability. This indicates thatvanadium is not sensitive to over-treatment.

Zinc. There is considerable data on zinc stabilization,all of it indicating the substantial reduction in leach-ability is achieved with simple pH control, usingsimple cement-based stabilization systems. Whilecomplexation with cyanide is common in electroplat-ing wastes, the data on treatment of electroplatingsludges and other wastes indicate no problems withstabilization of zinc in these residuals.

Finely Divided Elemental Metals. Particulate, el-emental metals may be divided into three categories.• Very finely divided metals are often pyrophoric,

and must be handled as D003 Reactive Waste.The usual way to de-activate these wastes wouldbe to react the metals to a higher valence state;care should be taken due to the possibility ofhydrogen gas formation, an explosion hazard.In this process, the metal could be speciated in arelatively insoluble form and may or may notrequire further special treatment.

• Non-reactive elemental metals with low solubil-ity in the TCLP test—beryllium, cadmium, chro-mium, nickel, silver, zinc—would likely pose no

difficulty stabilized or not stabilized.• Metals with higher solubility in the test—lead,

mercury and selenium —should experience sub-stantial reduction in leachability in stabilizeddebris because the metal, as it dissolves, reactswith the alkalinity in the cement or pozzolan toform low-solubility hydroxides.

Organics

Organic stabilization, although more recent than metalstabilization, has been shown in numerous studies(Conner, 1990) (Gilliam et al., 1986) (Caldwell et al.,1990) (Soundararajan et al., 1990) to be capable ofconsiderably reducing the mobility of organic constitu-ents. In 1990-1991, a massive study was conducted onthe stabilization of low-level organic contaminants insoils (Conner and Lear, 1991). It demonstrated that themobility of nearly all classes of organics could be sub-stantially reduced by the proper choice of additive, asmeasured either by the Toxicity Characteristic Leach-ing Procedure (TCLP) or by Total Waste Analysis(TWA). In view of the most recent regulatory stance onorganic stabilization, it is necessary in many cases toconduct both Total Constituent Analysis (TCA) andTCLP analyses on samples before and after stabiliza-tion to prove the effectiveness of the treatment.

Stabilization, with additives, can meet the presentTC standards for all TC-constituents (USEPA, 1990).S/S can also meet the Proposed Universal TreatmentStandards (UTS) (Federal Register, 1993)(USEPA, 1994)based on Total Constituent Analysis (TCA) for most ofthe 50 constituents tested in the Conner and Lear(1991) study. Reductions in TCLP leachability rangedfrom a minimum of 90% to better than 99%. Reduc-tions in TCA ranged up to 99.9%, with some reductionin all cases.

One surprising result of the above and other recentexperimental work (Spence et al., 1990) has been thefact that Volatile Organics (VOCs) are not necessarilylost by volatilization during S/S, as was previouslythought (Weitzman et al., 1987). TCA reduction levelssuggest that VOCs sorbed onto or associated with soilparticles may be less susceptible than expected to vola-tilization during stabilization, at least in these slowexotherm, cement-based systems under relatively staticair flow conditions. Some additives, such as rubberparticulate, have been shown in independent studies(Environmental Technologies Alternative, 1994) tosubstantially reduce the evaporation rate of VOCs sothat air pollution is minimized, and also reduce theflash point of the system, thus providing an additionalsafety factor in treatment and disposal. This property

13

PCA EB211

is expected to be of increasing importance as the new airpollution control requirements (USEPA, 1991) for treat-ment units come into effect.

Based on the work by Conner and Lear (1991), threeadditives –—activated carbon, organoclays, and a pro-prietary rubber particulate formulation — all are broadlyuseful with specific contaminants in specific test meth-ods, and none works best for all. Carbon is effectiveoverall for reduction in TCLP leachability but not forreduction in TCA. Particulate rubber is not as effectivein TCLP reduction, but is the only additive that wasbroadly useful for TCA reduction, especially for thelow-volatility compounds. Organo-clays are effectivewith specific contaminants.

In addition to these three additives, some othershave been found to have very narrow applicability forspecific situations. Tables 9 - 11 (pp 43-46) list a numberof organic compounds that have been stabilization-testedwith various additives (Gilliam et al., 1986) (Conner andLear, 1991) (Conner, 1995) (Conner et al., 1990) (Connerand Smith, 1993). Unless otherwise stated, the test workwas performed on natural soil spiked with the indicatedconcentrations of target organic compounds. The spikedsoil was stabilized with 20% cement alone, and with 20%cement plus a number of generic and proprietary addi-tives. In most cases, the additive was used at the 10%addition level because the total level of target constitu-ents approached the 10,000 mg/kg (1%) level. Thisresults in very expensive formulations. However, inpractice it is probable that much lower levels can be usedin most instances - most likely in the 1% to 5% range,which would result in additive costs of about $5 to $100per ton of waste treated.

All samples were subjected to both TCLP and TCAtesting. The tables give the best level achieved in TCLPand TCA testing, respectively, for each target com-pound, and the additive and addition ratio used toattain that level (in a few instances, designated by “none,”no addititive was required). Because of the uncertaintyat this time as to what the final regulatory stance will beregarding organics, it is difficult to state how useful S/Swould be in any given scenario. However, the achiev-able TCLP and TCA levels shown here should allow thereader to determine whether S/S may be effective in agiven waste/treatment/disposal situation once the re-quirements are established. Table 12 (page 47) summa-rizes reagent utilization, showing the most useful addi-tives for various organic groupings. In using thesetables, it is important to understand that, in addition tothe additive that gave the best result, other additivesusually also produced improved results for a givencombination of target constituent and test method. Inpractice, the actual selection of additive(s) must bedetermined by treatability testing with actual wastes.

Volatile organics (VOCs). Although there is no oneadmixture that produces the best results for all con-stituents or combination thereof, activated carbonworks best for TCLP reduction of VOCs overall(Conner and Lear, 1991). Although some volatiliza-tion undoubtedly takes place, comparison of the TCAand TCLP results shows that this is a minor effect inmost instances. Carbon has now been used success-fully in a number of specific remediation treatabilitystudies (Chemical Waste Management, 1994) (Siegristet al., 1992) (Morse and Dennis, 1994). Organo-clayshave also been used successfully in organic VOCstabilization. A modified rubber particulate, KAX-100™1, also worked well for VOC stabilization, espe-cially for TCA reduction. Table 9 lists the most effec-tive additives for the various organic compounds thathave been tested.

Semi-volatile organics (SVOCs). Conner and Lear(1991) showed that, for SVOCs, carbon produces thebest TCLP mobility reductions, but rubber particulate(Environmental Technologies Alternatives, Inc., 1994a)provides the best reductions in TCA (Conner andSmith, 1993). A mixture of carbon and rubber particu-late would seem to be way to go for SVOCs, depen-dent on what EPA finally does in the way of organicstabilization regulations. Rubber particulate is sur-face treated, finely ground tires or other rubber scrap,with particle sizes in the range of 10 to 60 mesh. It isgenerally less expensive than carbon, especially vir-gin carbon. Thus a mixture of the two would be costeffective. Table 10 lists the most effective additives forthe various semi-volatile organic compounds thathave been tested.

Mixtures of VOCs and SVOCs. This common situa-tion seems to be best handled by a mixture of carbonand rubber particulate, by a modified rubber particu-late (Environmental Technologies Alternatives, Inc.,1995), or by organo-clays for specific compounds. Thebest additive or combination of additives can be deter-mined by comparing the mixture of target compoundsto be treated with Tables 9 and 10.

Polychlorinated biphenyls (PCBs). PCBs are wellknown to be immobile in virtually any stabilizationsystem. There is considerable literature (Conner, 1990)showing the latter effect. Therefore, PCB stabilizationcan be effectively accomplished in simple cement-based systems.

1 KAX-50™ and KAX-100™ are proprietary rubber particu-late-based additives manufactured by EnvironmentalTechnology Associates, Inc., Port Clinton, OH.

14


Pesticides, herbicides. Conner and Lear (1991) foundthat pesticides and herbicides are easily immobilizedleachability-wise with cement plus carbon formulations,and in many cases, by cement alone. TCA reductionsrange from 50% to greater than 99%. A general formula-tion here would again be a cement/carbon/rubber mix-ture; however, depending on the regulatory interpreta-tion of what test method constitutes “mobility reduc-tion” for organics, cement alone might be used in manycases. Table 11 lists the most effective additives for thevarious pesticides and herbicides that have been tested.

Organo-Metallics

Many industrial waste streams contain soluble metalcomplexes that are very difficult to treat because of theirstability. Simple complexes such as cyanides can bedestroyed by alkaline chlorination. More stable com-plexes such as citrates, EDTA chelates, and a widevariety of non-chelate organometallics may requirestrong oxidants such as potassium permanganate orpotassium persulfate, and possible use of elevated tem-perature. Other problems complicate the oxidativedestruction of complexes. If chromium is present it willbe oxidized to Cr+6 and must then be reduced beforeprecipitation. With either oxidizing or reducing agents,species other than the target compound may competefor the reagent; large additions of oxidizing agent maybe necessary and this becomes very expensive and timeconsuming. Therefore, a non-oxidative method forhandling complexed nickel is desirable. Recently, an-other approach was used with nickel chelates—sorp-tion on activated carbon. This reduced the leachabilityof nickel substantially and met the required regulatorylevel. Additional studies have shown that this tech-nique also works with chromium, and should workwith arsenic and cadmium. The sorbed organometalliccompounds may then be solidified using portland ce-ment. Table 7 lists the additives used for organo-metallic compounds.

Organo-arsenic compounds. The organic arsenicalsare of special interest in stabilization because they areoften found in wastes, especially in remediation work atold lagoons and other contaminated disposal sites.Arsenic combines readily with carbon to form a widevariety of compounds many of which are manufacturedand used commercially, but may also be formed aswaste products in manufacturing and during wastetreatment processes.

Organo-cadmium compounds. A number of organicligand complex systems involving cadmium are known:

acetic acid, dimethylglyoxime, EDTA, glycolic acid,methylamine, oxalic acid, pyridine, sulfamic acid, tar-taric acid, and thiourea. Dialkyl cadmium compoundsare used as polymerization catalysts in organic andpolymer synthesis, and as heat and light stabilizers inplastics. The major complex in use, however, is inor-ganic Cd(CN)4

-2, which is used in electroplating and istreated with alkaline chlorination.

Organo-lead compounds. Tetraethyllead (TEL), usedas an antiknock additive in gasoline until recently, isthe most important organo-lead compound from astabilization standpoint. While TEL has undoubtedlybeen present in various waste streams, there does notseem to have been a reported leachability problemtraceable to it. This may be due to its low solubility, orto low levels in the wastes.

Organo-nickel compounds. Organo-nickel complexesinclude salts such as acetate, formate, oxalate and stear-ate, and nickel chelates. Nickel acetate is found in metalfinishing operations such as aluminum anodizing andelectroplating. The fatty acid salts are used in dying ofsynthetic fibers. Various soluble chelates are formed,and these are the source of most of the problems en-countered in fixation of nickel. Organo-nickel com-plexes such as EDTA, citrate, and gluconate may re-quire high temperature oxidation with strong oxidiz-ing agents. Nickel cyanide complexes can be brokenwith alkaline chlorination, leaving a nickel species whichcan be stabilized to low leaching levels.

Organo-silver compounds. In cases where a stable,soluble silver complex is present in large amounts,several techniques are available. Magnesium sulfateand lime can be used to precipitate a mixed sulfate-oxide. Alkaline chlorination can be used to break thecomplex and precipitate silver chloride. Sulfides andhydrosulfites are also used to treat silver complexes.

Soluble Salts

Chlorides, nitrates, sulfates. While it is possible toinsolubilize these anions (e.g., silver for chloride, bariumfor sulfate, etc.), there is no practical way to do so withinthe realm of S/S processes. The best approach is toproduce a low permeability matrix, and/or one that ishydrophobic, to limit the diffusion of the solute out ofthe stabilized mass. However, this technique will notbe effective with crushed or ground material, as isdeliberately done in the TCLP test. Actual field leach-ing of stabilized masses should be much lower thanTCLP tests indicate, because of the monolith effect.

15

PCA EB211

Cyanides. This issue has been in dispute betweenindustry and EPA. As we understand it, the disputecenters around whether one-step alkaline chlorina-tion as presently used constitutes “destruction” inEPA’s meaning of the word, i.e., conversion to CO2and nitrogen. This also affects the use of calciumpolysulfide, which converts the cyanide to thiocyan-ate. EPA has said that stabilization is not permitted forcyanide treatment, and that these two processes mayconstitute stabilization, especially if they are used inconjunction with normal cement or pozzolan treat-ment. Therefore, while cyanide standards can be metwith additive-enhanced stabilization, the regulatorysituation is unclear at this time.

IV. ADDITIVES USED IN CEMENT-BASED STABILIZATION/SOLIDIFICATION

Many additives have been tried out in S/S processes,and a number are used commercially, especially atTSDFs. A summary of the most commonly encoun-tered additives and the characteristics of their use isgiven in Table 1. In this section, specific additives areunderlined for easier identification in the text. Refer-ences to the use and properties of many of theseadditives have been given in earlier sections; where noreference is given, refer to Conner (1990), BattelleColumbus (1993), U.S. Army Corps of Engineers Wa-terways Experiment Station (1990), and United StatesEnvironmental Protection Agency (1982). Stabiliza-tion additives can be categorized in three basic ways:metal stabilization; immobilization of organic con-stituents; processing and anti-inhibition aids.

Metal Stabilization

pH control and buffering. Acids, alkalies and salts,such as lime, caustic soda, and ferrous sulfate, can beused to control the pH of the system. Buffers such ascalcium carbonate and magnesium oxide are used tokeep it within the desired range after the leaching testis complete. Control of pH can also effect the removalof interfering substances from solution in certain cases,e.g., destruction of gels and film-formers.Lime

The most common alkali used in stabilization islime (either quicklime (CaO) or hydrated lime(Ca(OH)2)), because it is the most cost effectivein most instances. Lime also supplies additionalcalcium for cement reactions and may react withcertain interfering organics. Lime products may

be either high calcium or dolomitic. The lattercontains substantial amounts of MgO or Mg(OH)2in place of some of the calcium.

Sodium Hydroxide (NaOH)In addition to neutralizing acids and raising pH,NaOH may also solubilize silica for quicker reac-tions of the pozzolanic type. One problem withthe use of sodium alkalies is that the cementitiousreactions which serve to moderate high pH inthose systems (Cote, 1986) are counteracted bythe presence of sodium ion.

Magnesium Oxide (MgO)Acts as a pH control, buffering agent. MgO hasalso been found to be useful as an additive toportland cement solidification in the nuclear wastearea (Carlson, 1987).

Sodium Carbonate (Na2CO3)Also known as soda ash, Na2CO3 is much lessfrequently used than lime in S/S work, but issometimes present in raw wastes where it wasused for neutralization of wastewaters or otherprocess wastes. Sodium carbonate also may beused in lead stabilization, and as a buffer inachieving more precise pH control.

Sodium Bicarbonate (NaHCO3)Acts as an accelerator (Shinoki et al., 1980) as wellas a pH control, buffering agent.

Reduction. Reducing agents are used for the treatmentof hexavalent chromium (Cr+6). The most common areferrous sulfate (FeSO4•7H2O), sodium metabisulfite(Na2S2O)5 and sodium hydrosulfite (Na2S2O4). Withferrous sulfate, the additive is mixed in first with thesystem preferably at low pH, then the portland cementis added and mixed in. With sodium hydrosulfite, thereagents and additive can be added in any order.Ferrous Sulfate

Probably the most widely used metal reducingagent in the S/S field, primarily on wastes con-taining Cr+6. It is safe to use, inexpensive (asreducing agents go), and often produces addi-tional benefits by co-precipitating the toxic met-als. Its main drawbacks are large volume increaseand the requirement of low pH for acceptabletreatment times. The latter problem is especiallyacute in the case of wastes with high alkalinity,where very large quantities of acid may be re-quired for pH adjustment. Reduction with fer-rous sulfate is a three step process: 1) pH adjust-ment to <3, 2) addition of ferrous sulfate andmixing until reaction is complete, and 3) raisingpH to >7 with portland cement to precipitatemetal as the hydroxide or as a co-precipitate withferric and ferrous iron. The last step allows oxida-

16


tion of ferrous iron to the Fe+3 valence state byoxygen in solution, and any residual reagentshould be destroyed. Reduction occurs over awider pH range, but at lower rates (Allied Chemi-cal Co., 1976)(Eary and Rai, 1988).

Sodium Metabisulfite/Sodium BisulfiteThese two additives react in the same way, sincemetabisulfite is the anhydrous form of bisulfite.The former is often used because it does not cakein storage. These reagents are effective reducingagents for Cr+6 and require much less acid andalkali than does ferrous sulfate, thereby generat-ing less sludge. While considerably more expen-sive than ferrous sulfate, which can often beobtained as a waste product, much less is used.The overall cost of bisulfite reduction is often lessthan that of ferrous sulfate. The principal objec-tion to the use of the bisulfites in S/S systems istheir tendency to generate sulfur oxides in vol-ume on contact with acids, a very serious prob-lem. The solids in waste residuals seem to in-crease the evolution of SO2, perhaps by a surfacecatalysis reaction. This is especially evident whentreating Cr+6 contaminated soils. Reduction ratedepends on pH (Allied Chemical Co., 1976).

Sodium HydrosulfiteThis additive is effective at the alkaline pH ofmany waste residuals, hence it normally doesnot require pH adjustment before addition. Also,it remains effective after addition of the usuallyhighly alkaline solidification reagents. This al-lows the addition of both types of reagent inrapid sequence, or even together. The majordrawback to the use of sodium hydrosulfite iscost; it is several times as expensive than themetabisulfate and more of it is required, al-though no acid is used. Nevertheless, where theCr+6 level in the waste is not too high, the addi-tional cost may be justified by simplification ofthe process (Allied Chemical Co., 1976).

Metallic IronIron filings have been tested successfully for usein reduction, but commercial use to date is notdocumented.

Other Reducing AgentsSulfides, sodium borohydride, reductive resins,and hydrazine have all been suggested for usein S/S, but have found little or no commercialapplication.

Oxidation. Oxidizing agents are used for severalpurposes: to increase the oxidation state of certainmetals such as arsenic (converting As+3 to As+5); todestroy soluble complexes such as organo-metal com-pounds (so that they can be precipitated as a less

soluble species), cyanides, hydrogen sulfide and phe-nol; to destroy interfering substances in the waste,such as algae; to alter the biological status of thesystem. There are many oxidizing agents which could,in principle, be used but most are impractical for onereason or another, usually cost. For As+3 oxidation andamenable cyanide destruction, a hypochlorite(Ca(OCl)2 or NaOCl) is normally used. For destruc-tion of organo-metal compounds, a more powerfuloxidant such as potassium permanganate (KMnO4) orammonium persulfate ((NH4)2S2O8) is used. Hydro-gen peroxide may be used for biological control. Majorproblems in the use of oxidants are non-specificityand competing constituents. If a waste contains bothnickel chelate and Cr+3 ion, oxidizing the chelate torelease nickel may also oxidize the chromium to Cr+6,which must subsequently be reduced again. This iscostly not only in the extra processing required, but inthe use of oxidizing agent where it is not needed orwanted. Organics such as oil and grease will competefor the oxidizing agent, making oxidation a very costlyprocedure if a selective agent cannot be found.Sodium or Calcium Hypochlorite

Hypochlorites are the most common oxidizingagents in S/S, having been used commerciallyprimarily for cyanide destruction and for triva-lent arsenic compounds (Conner, 1993a).

Potassium PermanganateA powerful oxidizing agent, potassium perman-ganate is used for destruction of certain organ-ics. Commercially, it has been used for phenoldestruction (Conner, 1990).

Ammonium/Sodium PersulfatePersulfates are effective in some instances wherepermanganates are not as effective. No com-mercial use has been documented.

Speciation, Re-Speciation. By far the most importantfixation mechanism for metals in S/S systems is chemi-cal precipitation as low-solubility species. All of thecement-based S/S processes and methods precipitatedissolved metals as hydroxides, silicates, or sulfides,and less frequently as carbonates, phosphates, or vari-ous complexes. However, few of these systems arereally as simple as they appear. Usually, a combina-tion of mechanisms is active and the products oftreatment are frequently not simple compounds.Equally important, the wastes being treated by S/Stechnology often are already speciated as relativelyinsoluble compounds in sludges, filter cakes, and soils.Carbonates

In certain cases, metal carbonates are less solublethan their corresponding hydroxides. In cementchemistry, the natural formation of carbonates

17

PCA EB211

from carbon dioxide from the air is termed “car-bonation” (Cote 1986). Patterson et al. (1977)found that the formation of hydroxide precipi-tates controlled the solubility of zinc and nickelover a range of pH values, but cadmium and leadsolubilities were controlled by carbonate precipi-tates in a narrower range. This is in keeping withthe results of treatability tests conducted by theauthor on lead-bearing wastes, using soluble and“insoluble” carbonates. One problem is that thecarbonates are decomposed at low pH, such asthat encountered in the TCLP test, if the pH of theleaching solution in contact with the solid actu-ally drops too low. If CO2 is evolved, the reactionis irreversible even if the final pH of the leachantis high, and the final speciation of the metal willbe as the hydroxide. This may explain the widelyvarying results reported (informally) by investi-gators testing carbonates, since the efficacy ofcarbonate precipitation would seem to be unusu-ally sensitive to test variables; the sample beingtested could either lose carbonate as CO2, or gainit in the same way from the atmosphere (air) inthe test container. The most common carbonateused in S/S is calcium carbonate (limestone oragricultural lime) because it is so inexpensive.While its solubility is low, calcium carbonate canprecipitate even less soluble carbonates such asthose of lead and barium. More soluble carbon-ates such as those of sodium or potassium may bemore effective, but are also more expensive.

Sulfur-Based AgentsOther than precipitation as hydroxides, sul-

fide precipitation of metals has probably been themost widely used method to remove metals fromwastewater. This method has been successfullyapplied in S/S treatment as well, especially forachieving regulatory limits for wastes containingmercury. Unlike water treatment, S/S treatmentrequires the use of cement, either concurrentlywith the sulfide treatment or afterwards, to pro-duce a stable product. Most metal sulfides are lesssoluble than the hydroxides at alkaline pH (ar-senic is an exception). Another interesting excep-tion in sulfide precipitation is that of chromium,which does not precipitate as the sulfide, but as thehydroxide. Therefore, chromium leaching will becontrolled by hydroxide precipitation, and henceby pH, at least in theory. Metal sulfide solubilitiesare not as sensitive to changes in pH. There arethree classes of sulfide precipitation reagents whichhave been investigated and used in S/S work:

Soluble inorganic sulfidesSodium sulfide (Na2S) and calcium polysulfide

(CaSx) are the primary examples of commercialuse of this class of sulfides in S/S. In some cases,the soluble sulfides will precipitate chromiumdirectly without pretreatment to reduce it to thetrivalent state, and sulfides are claimed to pre-cipitate complexed metals (Cherry, 1982). It isnecessary to maintain pH 8 or above to preventevolution of H2S. While excess sulfide ion isnecessary for the precipitation reaction, the ex-cess must be kept to a minimum so that freesulfide removal treatment is not required beforethe waste can be landfilled. The sulfide is addedbefore any of the solidification reagents, sincethe latter contain calcium, magnesium, iron andother metals which will compete for the solublesulfide. However, calcium sulfide, which haslimited solubility, may act as a sulfide buffer tomaintain a small excess available sulfide level inthe system, similar to the action of the alkalies inhydroxide precipitation.

“Insoluble” inorganic sulfidesOne answer to the problems encountered withuse of soluble sulfides is the use of very low-solubility species such as FeS or elemental sulfur.In the case of FeS, its solubility is about 0.0001mg/l in water. The former technology has beencommercialized as the Sulfex™ process (Knockeet al., 1977) (Feigenbaum, 1977). The advantageof this approach is that very little excess sulfideis present in the system at any time, so the prob-lem of H2S odor and toxicity is eliminated. Thecombination of elemental sulfur + alkali (Ader etal., 1989) has also been tested in S/S systems. Theprinciple here is that sulfide ion is generated as itis used up in metal-sulfide reactions, but only asmall amount of S-2 ion is present at any one time,thereby minimizing risk.

Organo-sulfur compoundsIn principle, organo-sulfur compounds may havecertain advantages over the inorganics. Severalinvestigators (Yagi and Matsunaga, 1976) (Yagi,1975) have found thiourea to be useful in reduc-ing mercury leaching from caustic-chlorine pro-duction wastes and other residues to very lowlevels, 0.0001 mg/l, in water. Nakaaki et al.(1975) lowered the mercury leachability of sea-bed sludge with a fixing agent containingpolydithiocarbamates and an iron or copper salt.Notably, all of these applications of organo-sul-fur compounds have been on mercury. This maybe due to the extremely low regulatory leachinglevels for mercury, or to the basic insolubility ofmercury sulfides, or both. Little has been re-ported on the use of these reagents for other

18


metals in sludges and other waste residuals. Onevendor (Chemical Engineering, 1988) has a lineof organosulfur reagents for use in wastewatertreatment, and there are a number of other re-agents of this class offered on a proprietary basis.

SilicatesThe reactions of polyvalent metal salts in solu-tion with soluble silicates have been studiedextensively over many years (Conner, 1990).Nevertheless, the “insoluble” precipitates whichresult from such interactions are not usuallywell characterized, especially in the complexsystems representative of most wastes. Metalsilicates are non-stoichiometric compounds inwhich the metal is coordinated to silanol groups,SiOH, in an amorphous silica matrix. The reac-tions of soluble silicates in solution is best sum-marized by Vail (1952), who states, “The precipi-tates formed by the reaction of the salts of heavymetals with alkaline silicates in dilute solutionare not the result of the neat stoichiometric reac-tions describing the formation of crystalline sili-cates, but are the product of an interplay offorces which yield hydrous mixtures of varyingcomposition and water content.” In any case,metals in solution can be effectively precipitatedby soluble silicates, and the reaction productstend to be less sensitive to pH variations in theenvironment than are hydroxide species. How-ever, metals already in relatively insoluble formare generally not re-speciated by soluble sili-cates. Nevertheless, there is evidence that suchspecies can be re-speciated in situations wheresilicates are constantly being formed. Bishop(1988) postulated that the observed low leachingof metals in portland cement CFS systems wasdue to the association of the metals with silica,possible as silicates. Perhaps most interesting isa patent application (Conner and Rieber, 1992)which claims the continuous production ofsoluble silicates from biogenetic, amorphoussilica and alkali.

For S/S work, the soluble silicate is usedalong with portland cement and/or cement kilndust, normally with the cement or kiln dustbeing added first and mixed into the wastebefore the silicate is added. The cement pro-vides the physical properties required in thetreated waste, due both to the action of thecement itself, and to its release of calcium ion toreact with the excess silicate, forming a solidcalcium silicate gel. It also results in betteroverall chemical properties in the waste form,moderating the high pH conditions in the soluble

silicate itself and interacting with waste con-stituents in ways already discussed.

PhosphatesPhosphate chemistry is very complex and var-ied. Compounds containing monomeric PO4

3-

are called orthophosphates or simply phos-phates. The simple phosphate salts of the toxicmetals have low water solubility, although theyare soluble in acids. For lead immobilization,either phosphoric acid or a sodium phosphate isused. For most S/S work, the phosphate is usedalong with portland cement and/or cement kilndust, normally with the phosphate being addedfirst and mixed into the waste before the cementis added. As is the case with soluble silicates, thecement provides the physical properties requiredin the treated waste. While phosphate is some-times used alone where lead is the only constitu-ent of concern and where physical propertydevelopment is not required, the immobilizatonof other RCRA metals requires the properties ofcement.

Iron CompoundsThe removal of toxic metals from wastewaterwith systems which co-precipitate and/or floc-culate them with iron salts is well known andwidely used (Sittig, 1973) (Swallow et al., 1980).More recently, it has been used to reduce thesolubility of various toxic metals in hazardouswaste treatment (Pojasek, 1980). The ratio of Fe+2

to Fe+3 is important, with ratios of 1:1 to 1:2reported as yielding optimum results. Sano etal. (1975) attribute the removal of zinc and cad-mium to the formation of ferrite crystals whichcould subsequently be removed magnetically.The crystals capture the other metals in thelattice, or adsorb them on the surfaces. Thismechanism has not been confirmed by others,who ascribe the results obtained to co-precipita-tion followed by flocculation. Sols of hydrousmetal oxides are stabilized by the presence ofexcess ferric ion, but acquire a negative charge,destabilize and flocculate under alkaline condi-tions. As the system becomes alkaline, the fer-rous ion is also easily oxidized to ferric, andprecipitates as the hydroxide. These reactionsremove other metal ions from solution, reduc-ing their concentrations to levels below thoseobtained with simple hydroxide precipitation.Whatever the mechanism, the net effect is reduc-tion of leachability in many instances. In addi-tion to the iron species, co-precipitation withcalcium carbonate and other species has beenreported (Envir. Sci. Tech., 1982).

19

PCA EB211

Again, for S/S work, the iron compound isused along with portland cement and/or ce-ment kiln dust, normally with the iron salt beingadded at the same time as the cement. Whereferrous iron salts are used for electrochemicalreduction, the iron salt is normally added first,and the cement added after reduction is com-plete. The cement provides the physical proper-ties required in the treated waste, as well as thealkalinity and other properties of cement neces-sary for immobilization of RCRA metals.

XanthatesCellulose and starch xanthates have been usedfor the stabilization of a number of metals inwaste streams, especially cadmium, chromium,nickel, and mercury (Bricka and Hill, 1989). Themost widely publicized additive has been in-soluble starch xanthate (ISX) (Wing, 1975). ISXis produced by treating starch with crosslinkingagents, then xanthating it with CS2 in the pres-ence of an alkali metal base such as sodiumhydroxide. The resulting product is a particu-late solid. Since 1980, ISX has been a commer-cially available product with usage in the treat-ment of wastewaters from metal finishing andsimilar sources. ISX is also reported to act as areducing agent for Cr+6. Chromium is reducedto Cr+3 and removed by neutralization to pre-cipitate the hydroxide. It should be noted thatISX operates at low pH and the process is lesseffective as pH rises. Tests with selenium(Navickis, 1975) indicated that the metal afterimmobilization with ISX could not be extractedwith either high or low pH water, but chlorideion does cause some release of selenium. Starchxanthate fixes mercury better than cellulose xan-thate, but xanthates alone are not adequate forfixation of cadmium, chromium and nickel —cement also is required. The latter finding prob-ably demonstrates the necessity for pH controlin the alkaline range for adequate fixation ofcadmium, chromium, and nickel, a result that isnot surprising.

Insoluble SubstratesRather than precipitate metals from solution inthe usual sense—by formation of low-solubilityspecies from ions in solution—another approachis to react the metal with an active area or func-tional group on the surface of an insoluble sub-strate. Nelson (1980) used a treated leatherwaste to remove heavy metal ions, particularlylead and cadmium, from nitrate and acetatesolutions. Another process (Chemical Engineer-ing, 1979) uses modified casein to remove cad-

mium, chromium, copper, mercury, nickel, andzinc from wastewater. Chromium reportedlycan be removed as directly as Cr+6, without priorreduction, to levels below 1.0 ppm from streamscontaining up to 500 ppm Cr+6. The casein ismodified by treating with formaldehyde to forma cross-linked, insoluble product.

Inorganic ComplexationMany metals exist in ores and rocks as complexcrystalline structures. The curing of cement-based solidification systems may eventually re-sult in complexes such as those formed whenmetals are removed from solution by substitu-tion for calcium, aluminum, etc. in cement hy-dration products. Another example is the for-mation of ferrite crystals mentioned previously,if indeed these actually form in CFS systems.Both ferricyanide and ferrocyanide form low-solubility species with a number of metals.

Organic ComplexationMany organic compounds form low-solubilityspecies with certain metals (e.g., tartrates ofcadmium, lead, mercury(+1), and nickel). Un-fortunately, little information is available oneither the actual solubility numbers for metalorganic compound in aqueous solution or on theeffects of pH and other ions. Manahan andSmith (1973) report that humic acids formed inthe decay of vegetable matter immobilize metalions in sediments and soil.

MiscellaneousSodium sulfate (Na2SO4) and sodium chloride(NaCl), respectively, are used to immobilizesoluble barium and silver species. Young (1979)reported improved resistance to arsenic leach-ing by the addition of calcium and manganesechlorides, sulfates, and acetates. Onoda CementCo. (1976) used gypsum to produce an improvedproduct from S/S with cement. Chen (1978)reported improved leaching properties by usinga mixture of cement and vermiculite. Phospho-rus pentoxide and a stearate (Takashita, 1979)were used to treat oily sludges.

Co-precipitation and flocculation. Aggregation offine particles and film-formers into larger size flocsthat are removed from the reactive cement particlesurfaces can prevent the inhibition of cement settingand hardening. There are many organic surfactantsthat might be used for this purpose, and a few inor-ganic additives. Co-precipitation can be very useful inimmobilizing metal and organic compounds in a com-plex structure. It is difficult to separate the effects ofco-precipitation from those of sorption in systems

20


where the sorbent is formed in-situ.Ferrous Sulfate

In addition to its use as a reducing agent, ferroussulfate is used as a co-precipitant and flocculat-ing additive, primarily in lead stabilization andespecially where mobile colloidal species arepresent. It can also be used for the same purposefor other metals such as arsenic, if necessary.

Organic Flocculants, SurfactantsThere is a large variety of organic surfactants thatcan be used to remove fine particulate matterfrom the surfaces of the reactive cement par-ticles, thereby preventing their inhibiting effect.Alcohols, amides, lignosulfonates (Kokusai, 1981)(Veda and Ito, 1977), and other specific surfac-tants can aid in wetting solids and dispersingfine particulates and oil which interfere withreactions by coating the reacting surfaces.Flocculants can also serve this purpose.

Other surface effects. Dispersion of oils, greases, andfine particulates away from reacting surfaces, and pre-cipitation of interfering substances have effects analo-gous to the use of flocculation on interfering particulatematter. Generally, a wide variety of commercial organicsurfactants can be used for this purpose.

Ion Exchange. Ion exchange can be either beneficial ordetrimental to cement-based S/S. It can inhibit orretard S/S reactions by removing calcium from solu-tion, preventing it from entering into the necessarycementitious reactions. It can also accelerate the pro-cess by removing interfering metal ions from solution.Which occurs may depend on the selectivity of the ionexchange material.

Substitution. Certain metals may retard and inhibitthe reactions by substituting for calcium in thecementitious matrix, which may explain the effect ofmagnesium in dolomitic lime products. Certain sub-stances are natural or synthetic complexing agentswhich remove calcium from availability in the settingand curing reactions. However, cement can also im-prove metal immobilization when the metals substi-tute for calcium in the hydrated cement matrix.

Sorption. Here, the term “sorption” is used to coveradsorption at surfaces, absorption into the interior ofsolid substrates, and chemisorption. Often, it is impos-sible to distinguish between these various effects inreal, complex systems, and in the practical sense, it doesnot matter anyway. An example of sorption of metalson active oxides is given by Posselt and Anderson(1968). They used hydrous manganese dioxide formed

in-situ by reduction of permanganate ion (Mn+7). Metalion sorption was rapid, with equilibrium attainedwithin minutes. Dzombak and Morel (1987) foundconsiderable data which show that metals adsorbstrongly to iron and aluminum oxides. Lagvankar etal. (1986) described an interesting process using ironfilings which are activated by the waste stream itself.Metal sorbents can be broken down into a number ofclasses or groupings:

Metal OxidesIron, manganese, aluminum, etc.

ClaysBentonite, montmorillonite, attapulgite,illite, kaolinite - all natural and modified.

Natural MaterialsPeat moss, natural zeolites, sawdust,vermiculite, sand, etc.

Synthetic MaterialsZeolites, flyash, cullite, activated alumina,organic polymers, etc.

Activated CarbonCement Hydrate PhasesChan et al. (1980) evaluated ten potential sorbents,

natural and synthetic, for their ability to remove avariety of pollutants from landfill leachate. They foundthat no single sorbent is effective in removing all pollut-ants, and some were not attenuated by any of thematerials tested (bottom and flyashes, vermiculite, il-lite, sand, activated carbon, kaolinite, natural zeolite,activated alumina, and cullite). As expected, activatedcarbon was most effective for organics, with illite alsobeing successful. Specific sorbents were effective onfluoride and cyanide, but not on chloride. Activatedalumina was moderately effective in removing nickel,but none of the other sorbents achieved any successwith this metal. None of the sorbents tested wereeffective for lead. Other investigators have found thatflyash, kaolin, and sawdust (Benson, 1980), and a cal-cined mixture of bentonite and flyash (Japan Kokai,1980) were effective in immobilizing a variety of metals.

Immobilization of Organic Constituents

Sorption. Sorbents are used for immobilization oforganics and organo-metallic compounds (arsenic,chromium, lead, and nickel). While many sorbentshave been tested, the most effective overall are acti-vated carbon, organo-clays, and rubber particulate.From a practical standpoint, a combination may be thebest single sorbent where a variety of organic constitu-ents of concern are present. Sorbents can also immo-bilize organo-metallic species, especially thosecomplexed forms which are otherwise difficult to

21

PCA EB211

precipitate. Sorbents can also be used for removal ofinterfering substances from reacting surfaces.Activated Carbon

One of the earliest mentions of the use of acti-vated carbon for immobilization of organics (pri-marily phenol) was by Chappell (1980). Sincethen, carbon has been used for this purpose in anumber of commercial projects (Lawson et al.,1996) and has been demonstrated in many treat-ability studies (Conner and Lear, 1991).

ClaysNatural clays are not very effective stabilizationagents for organics, less so than for metals.However, treated clays – the so-called organo-clays – are effective (Boyd and Mortland, 1987).These are natural clays that have been reactedwith various reagents, primarily quaternary am-monium compounds and derivatives, to renderthem organophillic on internal as well as exter-nal surfaces. The organophillic groups attachedto the clays attract and hold organic contami-nants in the waste. Organo-clays have beenused for this purpose in a number of commercialprojects (Lawson et al., 1996) and have beendemonstrated in many treatability studies(Conner and Lear, 1991).

Rubber ParticulatesThese are proprietary formulations (Environmen-tal Technologies Alternatives, Inc., 1994a) – KAX-50™ and KAX-100™–based on rubber particulatederived from ground scrap tires, and were report-edly specifically formulated for this purpose.KAX-50™ was most effective with semi-volatileorganics (Conner and Smith, 1993), while KAX-100 ™ worked best for mixtures of VOCs andSVOCs, as well as the pesticides/herbicides group.

Oxidation of unwanted species. Powerful oxidizingagents such as potassium permanganate and sodiumpersulfate are effective in destroying certain organiccontaminants in wastes. See “Oxidation” in the previ-ous section, Metal Stabilization, for more informationon these additives. However, there are a number ofdrawbacks to the use of oxidizers for this purpose. Theprimary problem is cost. Since these additives aregenerally non-selective in their action, all oxidizablespecies in the waste will compete for the additive;examples are oils, biological materials, vegetative mat-ter, metal species such as Cr+3 and many other commonwaste components. Thus, a very large excess of addi-tive may be required. Secondly, the oxidation processis exothermic and considerable heat is often generated,which will tend to vaporize VOCs rather than destroythem, and cause air pollution problems. Also, any

chromium in the waste will be oxidized to the Cr+6

valence state, and then require reduction so that it canbe stabilized. For these reasons, oxidation has beenlittle used for organic treatment, except in instanceswhere the constituent is easily oxidized and present atlow levels and there is little other oxidizable species inthe waste. One successful use has been for phenoldestruction in metal finishing wastes (Conner, 1990).

Processing and Anti-inhibition Aids

More and more, additives are being used in chemicalsystems for purposes other than stabilization. Ce-ment-based systems, especially, are sensitive to manywaste components discussed previously in their set-ting and strength development. Additives such aslime and sodium silicate are often used to counterthese inhibition effects. On the other hand, somewaste components cause premature setting and re-quire the use of set retarders commonly used in mak-ing concrete. The latter effect must also be controlledin some delivery systems, especially in in-situ S/S.Other processing aids are sometimes used: “water-reducing agents” or surfactants to lower viscosity, orclays and polymers to increase viscosity. This subjectis covered in some detail in Section II, and will only bediscussed briefly here.

Acceleration. There are many compounds that havebeen reported for their ability to accelerate the settingand/or hardening of cement. Many of these may beeffective also in cement-based S/S systems. Commonadditives and groups of additives, along with refer-ences to their use, are listed as follows:

Calcium Chloride (Kantro, 1975)Dispersants/Water Reducing Agents (Falcoux

et al., 1980)Magnesium Oxide (Kawasaki Steel Corp., 1980)Lime (Falcoux et al., 1980)Calcium Aluminate MineralsAmines (Wagner and Ellis, 1980)Organic Acids and Salts (Falcoux et al., 1980)

(Yamagisi et al., 1980) (Bonnel andHevanee, 1972)

Glycols and Related Compounds (Wagner andEllis, 1980)

Calcium Tetraformate (Berry, 1980)Asphalt Emulsion

Combined with cement, calcium aluminateminerals, and calcium sulfate(Higuchi, 1978)

Metal IonsMechanism unclear

22


Cement Kiln DustSource of lime

Of all of these additives, calcium chloride, lime,cement kiln dust, sodium silicate (see below), and theproprietary concrete set retarders have been most usedin S/S technology.

Anti-Inhibition. These additives function in the samemanner as accelerators in many cases, and thus arebasically the same materials. However, some additivesnot normally used in concrete technology are used inS/S. An example of this is sodium silicate, which reactswith interfering metals and other waste componentsand also causes acceleration of initial set by very rap-idly forming a silicate gel.

Retardation. To date, most applications of set retardersin S/S systems have been with the proprietary setretarders commonly used in concrete ready-mix batchplants. These applications have been for in-situ S/Swhere the pumpable grout is made up first, and theninjected into the waste, requiring it to remain pumpablefor up to several hours before beginning to set. Otherretarders are:

Sugars and Derivatives(Metcalf and Ellers, 1980) (Industrial WaterEngineering, 1970)

Excessive Water Content. Excessive water in the wastecan result in supernatent liquid on the surface aftersetting and in low strength in the cured waste form.Additives used to counter these problems are of threetypes: accelerators to reduce set time; bulking agents orsorbents to reduce the free water; and gellants to in-crease viscosity of the system. Accelerators were dis-cussed in Section IV, gellants in Section II. Bulkingagents commonly used are listed below:

FlyashCement Kiln DustBlast Furnace Slag (Chudo et al., 1981)Corn Cob, Wood Chips, etc.

V. PHYSICAL/CHEMICAL TECHNIQUESUSED IN CEMENT-BASEDSTABILIZATION/SOLIDIFICATION

In addition to additives, other techniques are used inS/S to improve the properties of the product, to aid inprocessing, and to immobilize or destroy various con-stituents of concern.

Anti-Inhibition Aids

There are some physical, non-additive techniques thatcan be used to counter the effects of inhibiting materi-als in the waste.

Aeration. Aeration can serve several purposes: alter-ation of biological status of the waste, which mayprevent the formation of inhibiting film formers onthe surfaces of the cement binder; and removal ofinterfering VOCs.

Temperature Adjustment. This technique can be usedboth to improve the leaching characteristics of the wasteform produced by S/S (Vejmelka et al., 1985), and toaccelerate the reaction rate to counter retarding effects.

Physical Property Development

Humidity Control. Ambient humidity in the curingarea must be kept high if the product is to cure properly.Evaporation of water from the surface will inhibit orstop solidification, and perhaps some fixation reactionsin the surface layer. In the laboratory, samples arenormally cured at about 95% relative humidity to pre-vent this effect from masking the real solidificationreactions. In very hot and dry field conditions, espe-cially where the layer of curing S/S product is thin, itmay be necessary to keep the waste moistened as itcures, much as is done with concrete under the sameconditions.

Dewatering. Removal of excess water by physicalmeans is often less costly than the use of additives toabsorb the water.

Air Entrainment. This technique may be useful insome cases where maximum freeze/thaw resistanceis required. It generally employs additives to aid inentrainment of air. Air entrainment is not known tohave been deliberately applied in the field.

Processing Aids

Viscosity/Pumpability Alteration. Water reducingagents, flyash (Industrial Water Engineering, 1970),and natural clays (attapulgite and illite) (IndustrialWater Engineering, 1970) have been used to adjust theviscosity of grout formulations, especially for in-situS/S applications.

Elevated Temperature. S/S processes are chemical

23

PCA EB211

reactions and would be expected to follow the generalrules of such – that reaction rate usually increases withtemperature, perhaps according to the old rule-of-thumb that reaction rate doubles with each 10oC rise intemperature. S/S reaction rates do increase withtemperature, but there are limitations. Below freezingtemperatures can cause irreversible changes in thefinal product by breaking gel structures at a criticalstage, much as can happen with concrete. At very hightemperatures, release of steam can actually break upthe solid mass, and the loss of water can interfere withsubsequent curing reactions. This latter phenomenonis of concern in cement-based systems which are exo-thermic. Some additives also generate a large exothermand very rapidly. This must be considered whendesigning the mechanical aspects of the system. Also,the low heat transfer rate from a large mass of treatedwaste while curing can drive the internal temperatureto unacceptable levels, even though a laboratory testdid not indicate a potential problem. This, also, mustbe taken into consideration in the system design. Selfheating of the mass, however, is a valuable aid tocuring if it is kept under control and within limits. Tobe assured that cementitious reactions will start, thetemperature should be maintained above -3oC.

Mixing Techniques

Mixing is an important, sometimes critical, element ofany S/S process. While it seems obvious that thor-ough dispersion of the S/S reagents in the waste isimportant, it is also possible to over-mix certain sys-tems. Fluid wastes such as low-solids sludges areusually easiest to mix, while sticky sludges and filtercakes with the consistency of peanut butter are themost difficult. Soils, solid particulates, and granularmaterials fall in-between. Selection of a mixer is notonly determined by the physical characteristics of thewaste, however. Some wastes and some processes arequite sensitive to the energy input and shear rate of themixer. Use of a high-shear mixer with some wastesmay irreversibly alter their properties, causing phaseseparation. On the other hand, high-shear mixingmay be required to completely homogenize othermixtures—for example, to incorporate non-polar or-ganics in aqueous systems. High energy input mayhelp with some plastic, pseudoplastic, or thixotropicwastes by decreasing their viscosity temporarily, andby aiding in the reactions (Kitsugi, 1978) (Munster,1982). In rare cases, dilatent materials may literallysolidify in the mixer before reagents are even added.

Over-mixing, either by using the wrong mixer ormixing too long, interferes with the initial gel forma-

tion of cementitious S/S systems, causing delayed set,slow curing and even the loss of final physical proper-ties. An extreme example of this is seen in the use ofsoluble silicates, where it irreparably destroys thesilica gel structure, preventing the process from work-ing properly at all. Over-mixing can also go the otherway. Many a processor has had to dig out a mixerbecause the blend set up before it could be emptied.This usually happens in batch systems, but has alsobeen observed in continuous mixers when the mixer isstopped while full.

While it is widely assumed that very thoroughand intimate mixing is require to assure that reactionwill take place and fixation of hazardous constituentswill be complete, it is known that such mixing does nothappen with most in-situ techniques and still the endresult may be satisfactory. One investigation (Chemi-cal Waste Management, 1987) tentatively reached theconclusion that complete mixing at the microscopicscale is not always necessary in commercial S/S sys-tems. Other scientists have recently realized this asthey began to look at the microstructures of solidifiedwastes (Eaton et al., 1985). At this level, apparentlyunreacted waste conglomerates are evident, as areareas of unmixed reagent. The question now remains:At what size level can inhomogeneities exist and stillnot prevent the process from achieving its function?There is probably no single answer; it varies fromwaste to waste and process to process.

Ex-Situ Mixing. The choice of mixer is determined bythe rheological properties of the waste, the reagents tobe added (including how many and in what order), themode of operation (batch, continuous, or in-situ), thethrough-put rate, and the waste conveyance methods.For large volume operations with a continuous, rea-sonably consistent feed, continuous mixing usuallygives the best results at the lowest cost. For smallerprojects, and where the waste feed is very variable,batch mixing may be the only feasible method. Some-times the two are combined by accumulating a largebatch of waste and homogenizing it to provide a uni-form feed to a low through-put, continuous mixer untilthe batch is processed.

In-Situ Mixing. In-situ mixing is a special case untoitself. The equipment used is not generally thought ofas a mixer, but has some other primary function as, forexample, a backhoe, a drilling auger used for stabiliz-ing foundations, or a rock cutting head used in mining.More recently, specialized equipment has been appliedmore and more to this area, most of it being constructedby or for the S/S contractor himself. Several require-ments for state-of-the-art in-situ S/S that are peculiar to

24


in-situ work are deliberate retarding of the set to allowtime for handling, injection and mixing of a grout intothe waste, and the formulation of that grout.

VI. REFERENCES

Ader, M., Glod, E.F., and Fochtman, E.G .,U.S. Patent4,844,815, Jul. 4, 1989.

Allied Chemical Co., Treatment of Chromium WasteLiquors, New York, 1976.

American Society for Testing and Materials (ASTM),Temperature Effect On Concrete, Philadelphia, PA,1985, p.104.

Ashworth, R., “Some Investigations into the Use ofSugar as an Admixture to Concrete,” Proc. Inst.of Civil Engineering, London, 1965.

Battelle Columbus, Technical Resource Document So-lidification/Stabilization and Its Application to WasteMaterials 4-29 - 4-44, EPA/530/R-93/012, UnitedStates Environmental Protection Agency, RiskReduction Engineering Laboratory, Cincinnati,OH, Jun. 1993.

Benson, R.E. Jr., “Natural Fixing Materials for the Con-tainment of Heavy Metals in Landfills,” Proc. Mid-Atlantic Industrial Waste Conf., 1980, pp. 212-15.

Berry, D., U.S. Patent 4,191,584, Mar. 4, 1980.Bishop, P.L., “Leaching of Inorganic Hazardous Con-

stituents from Stabilized/Solidified HazardousWastes,” Hazardous Wastes & Hazardous Materi-als 5, No. 2, 1988, pp.129-43.

Blake, L.S., ed., Civil Engineer's Reference Book,Butterworths, London, 1975.

Bonnel, B. and Hevanee, C., U.S. Patent 3,656,985,Apr. 18, 1972.

Boyd, S.A. and Mortland, M.M., “Use of ModifiedClays for Absorption and Catalytic Destructionof Contaminants,” 13th Annual Research Sympo-sium at Cincinnati, U.S.EPA, Cincinnati, Jul. 1987.

Bricka, R.M. and Hill, D.O., “Metal Immobilization bySolidification of Hydroxide and Xanthate Slud-ges,” Environmental Aspects of Stabilization andSolidification of Hazardous and Radioactive Sludges,ASTM STP 1033, American Society for Testing andMaterials, Philadelphia, PA, 1989, pp. 257-272.

Caldwell, R.J., Cote, P.L., and Chao, C.C.,“Investi-gation of Solidification for the Immobilization ofTrace Organic Contaminants,” Hazardous Waste& Hazardous Materials 7, No. 3, pp. 273-282.

Carlson, J.E., “The Chemistry of Processing NuclearWaste with Portland Cement,” Chemical WasteManagement Stabilization Seminar, Jun. 4-5, 1987.

Chalasani, D., Cartledge,F.K., Eaton, H.C.,Tittlebaum, M.E., and Walsh, M.B., “The Effects

of Ethylene Glycol on a Cement-Based Solidifi-cation Process,” Hazardous Wastes & HazardousMaterials, 3, No. 2, 1986.

Chan, P.C., Liskowitz, J.W., Perna, A., and Trattner,R.,Evaluation of Sorbents for Industrial Sludge LeachateTreatment, EPA-600/2-80-052, U.S. EPA, Cincin-nati, 1980.

Chappell, C.L., U.S. Patent 4,230,568, Oct. 28, 1980.Chemical Engineering, May 2, 1979, pp. 83-4.Chemical Engineering, Feb. 15, 1988.Chemical Waste Management, Internal Study, 1987.Chemical Waste Management, Stabilization of Sb, Be,

Tl and V Using AA100, Geneva Research Center,Geneva, IL, 1992.

Chemical Waste Management, Private Communica-tion, 1994.

Chen, K.S., U.S. Patent 4,113,504, Sep. 12, 1978.Cherry, K.F., Plating Waste Treatment, Ann Arbor

Science Pub., Ann Arbor, MI, 1982.Chudo, A., Sugi, T., and Katsoka, K., U.S. Patent

4,266,980, May 12, 1981.Conner, J.R., U.S. Patent 3,837,872, Sep. 24, 1974.Conner, J.R., U. S. Patent 4,518,508, May 21, 1985.Conner, J.R., U.S. Patent 4,623,469, Nov. 18, 1986.Conner, J.R., U.S. Patent 4,600,514, Jul. 15, 1986a.Conner, J.R., U.S. Patent 5,078,795, Jan. 7, 1992.Conner, J., Chemical Fixation and Solidification of Haz-

ardous Wastes, Van Nostrand Reinhold, NewYork, NY, 1990, pp. 77-102, 298-304.

Conner, J.R. and Lear, P.R., “Immobilization of Low-Level Organic Compounds in HazardousWaste,” Proc. Air and Waste Management 84thAnnual Meeting, Vancouver, BC, 1991.

Conner, J.R. and Lear, P.L., Treatment of Landban-Varianced Arsenic Wastes at TSDFs, ChemicalWaste Management, Geneva, IL, 1992.

Conner, J.R. and Rieber, R.S., U.S. Patent 5,078,795,Jan. 7, 1992.

Conner, J.R., “Advanced Stabilization Methods forTreatment of Hazardous Wastes,” Conference onChemical-Physical Treatment of Industrial Wastes,Univ. of Brescia, Italy, Jun. 17-18, 1993a.

Conner, J.R., “Recent Findings on Immobilization ofOrganics as Measured by Total ConstituentAnalysis,” Waste Management 15, Nos. 5/6, 1995,pp.359-369.

Conner, J.R. and Smith, F.G., “Immobilization ofLow-level Hazardous Organics Using RecycledMaterials,” Third International Symposium on Sta-bilization/Solidification of Hazardous, Radioactive,and Mixed Wastes, Williamsburg, VA, Nov. 1-5,1993.

Conner, J.R., Private Communication, 1993.Conner, J.R., Li, A., and Cotton, S., “Stabilization of

25

PCA EB211

Hazardous Waste Landfill Leachate TreatmentResidue,” Journal of Hazardous Materials 24, 1990,pp.111-121.

Coté, P., Contaminant Leaching From Cement-Based WasteForms Under Acidic Conditions, PhD Thesis,McMaster Univ., Hamilton, ON, Canada, 1986.

Cullinane, J.M., Jr., Jones, L.W., and Malone, P.G.,Handbook for Stabilization/Solidification of Hazard-ous Waste, EPA/540/2-86/001, U.S. EPA, Cincin-nati, OH, 1986.

Cullinane, M.J., Bricka, R.M., and Francingues, Jr.,N.R.,“An Assessment of Materials That Interferewith Stabilization/Solidification Processes,” InProc. 13th Annual Research Symposium, U.S.EPA,Cincinnati, OH, 1987, pp. 64-71.

Dzombak, D.A. and Morel, F.M., “Development of aData Base for Modeling Adsorption of Inorganicson Iron and Aluminum Oxides,” EnvironmentalProgress 6, No. 2, 1987, pp. 133-7.

Eary, L.E. and Rai, D., “Chromate Removal fromAqueous Wastes by Chromium Reduction withFerrous Ion,” Environmental Science Technology22, No. 8, 1988, pp. 972-7.

Eaton, H.C., Walsh,M.B., Tittlebaum,M.E., Cartledge,F.K., and Chalasani, D., “Organic Interference ofSolidified/Stabilized Hazardous Wastes,” Envi-ronmental Monitoring and Assessment 9, 1987, pp.133-142.

Eaton, H.C., Walsh, M.B., Tittlebaum, M.E., Cartledge,F.K., and Chalasani, D., “Microscopic Character-ization of the Solidification/Stabilization of Or-ganic Hazardous Wastes,” Energy Sources andTechnology Conference and Exhibition, ASME Pa-per No. 85-Pet-4, 1985.

Electric Power Research Institute, In-SituSolidification/Stabilization of Arsenic Contaminated Soils - DraftReport, Palo Alto, CA, Apr. 1996.

El-Korchi, T., Melchinger, K., Kolvites, B., and Gress, D.,The Effect of Heavy Metals and Organic Solvents on theMicrostructure of Cement Stabilized Hazardous Waste,University of New Hampshire, 1990.

Environmental Science Technology 16, No. 12, 1982, 641a.Environmental Technologies Alternatives, Inc., Con-

trol of Air Emissions in Hazardous Waste Stabiliza-tion Operations, KAX-50™ Technical Bulletin TB-214, Port Clinton, OH, 1994.

Environmental Technologies Alternatives, Inc., Im-mobilization of Organics in Debris and Characteristic(D-code) Wastes, Technical Bulletin TB-234, PortClinton, OH, 1994a.

Environmental Technologies Alternatives, Inc., KAX100™ Technical Bulletin, Port Clinton, OH, 1995.

Falcoux, P., Filhol, R., and Communal, J., U.S. Patent4,238,236, Dec. 9, 1980.

Federal Register: 48(176), Sep. 14, 1993, pp. 48092-48204.Feigenbaum, H.N., “The Sulfex™ Process for Re-

moval of Heavy Metals in a Textile WasteStream,” Proc. Textile Wastewater Treatment andAir Pollution Control Conference, Jan. 1977.

Gilliam, T.M., Dole, L.R., and McDaniel, E.W.,“Waste Immobilization in Cement-BasedGrouts,” Hazardous and Industrial Solid WasteTesting and Disposal: Sixth Volume, ASTM STP933, American Society for Testing and Materi-als, Philadelphia, PA, 1986, pp. 295-307.

Gilliam, T.M. and Wiles, C.C., eds., Stabilization andSolidification of Hazardous, Radioactive, and MixedWastes, 3rd Volume, STP 1240, ASTM, WestConshohocken, PA, 1996.

Harada, Y., Itai, N., Uchikawa,H., Kato, H., Sato, K.,and Itoh, A., U.S. Patent 4,060,425, Nov. 29, 1977.

Higuchi, Y., Harada, Y., Nakagawa, K., Kawaguchi, I.,and Kasahara, Y., U. S. Patent 4,084,981, Apr. 18,1978.

Industrial Water Engineering, Oct. 1970.Japan Kokai 70/40,797, Oct. 20, 1980.Kantro, D.L., “Tricalcium Silicate Hydration in the

Presence of Various Salts,” ASTM Journal OfTesting and Evaluation, July, 1975.

Kawasaki Steel Corp., Japan Kokai 80,136,166, 1980.Kitsuge, K. and Kozeki, S., U.S. Patent 3,947,283,

Mar. 30, 1976.Kitsugi, K., U.S. Patent 3,947,284, Mar. 30, 1976.Kitsugi, K. and Shimoda, M., Japan Kokai 78 12,770,

Feb. 4, 1978.Knocke, W.R., Croy,L.P., and Kelley, R.T., An Evalu-

ation of the Solids Handling Characteristics of SludgeProduced by Two Metals’ PrecipitationTechniques, Virginia Polytechnic Institute,Blacksburg, VA, 1977.

Kokusai, G., Japan Kokai 81 53,796, May 13, 1981.Lagvankar, A., Mayenkar, K., and Pherson, P.A.,

“An Innovative Process for Removing HeavyMetals from Wastewater,” 59th Annual MeetingCentral States Water Pollution Control Association,May 14-16, 1986.

Lawson, M.A., Venn, J.G., Pugh, L.B., and Vallis, T.,Stabilization and Solidification of Hazardous, Radio-active, and Mixed Wastes, 3rd Volume, ASTMSTP 1240, West Conshohocken, PA, 1996.

Manahan, S.E. and Smith, M.J., “The Importance ofChelating Agents,” Water and Sewage Works, 1973,pp. 102-6.

Metcalf, A.S. and Ellers, L.H., U.S. Patent 4,210,455,Jul. 1, 1980.

Morse, J.G. and Dennis, D., “Assessment and Cleanupof Soils Using In Situ Stabilization at a Manufac-tured Gas Plant Site,” At 87th Annual Meeting &

26


Exhibition, AWMA, Cincinnati, Jun. 19-24, 1994.Munster, L., U.S. Patent 4,338,134, July 6, 1982.Nakaaki, O., Horie, Y., Idohara, M., and Shiraogi, J.,

Japan Kokai 75,99,962, Aug. 8, 1975.Navickis, L.L., Wing, R.E., and Bagley, E.B., “AISX

Reduces Selenium Count in Process Wastewa-ters,” Industrial Wastes, Jan./Feb. 1979, pp. 26-30.

Nelson, D.A., “Removal of Heavy Metal Ions fromAqueous Solution with Treated Leather,” Ameri-can Chemical Society, Houston, TX, 1980.

Onoda Cement Co., U.S. Patent 3,947,284, Mar. 30, 1976.Patterson, J.W., Allen, H.E., and Scala, J.J., “Carbonate

Precipitation from Heavy Metals Pollutants,” Jour-nal of the Water Pollution Control Federation 12,1977, pp. 2397-410.

Pojasek, R.B., Toxic and Hazardous Waste Disposal, Vol.1-4, Ann Arbor Science Pub., Ann Arbor, 1980.

Portland Cement Association, Portland Cements,Skokie, IL, 1974.

Portland Cement Association, Design and Control ofConcrete Mixtures, Skokie, IL, 1979.

Posselt, H.S. and Anderson, F.J., “Cation Sorption onColloidal Hydrous Manganese Dioxide,” Envi-ronmental Science Technology 2, 1968, pp. 1087-93.

Rosskopg, P.A., Linton, F.J., and Peppler, R.B., “Effectof Various Accelerating Chemical Admixtures onSetting and Strength Development of Concrete,”Journal of Testing and Evaluation 3, No. 4, 1975.

Sano, M., Sugano, I., and Okuda, T., Japan Kokai75,133,654, Oct. 23, 1975.

Shinoki, K., Katayame, T., and Yamaguchi, S., JapanKokai 80 44,355, Mar. 28, 1980.

Siegrist, R.L. et al., “In-situ Treatment of Clay Soils byPhysicochemical Processes Coupled with SoilMixing: Highlights of the X-231b Technology Dem-onstration,” At I&EC Special Symposium, ACS, At-lanta, GA, Sep. 21-23, 1992.

Sittig, M., Pollutant Removal Handbook, Noyes DataCorp., London, 1973.

Soundararajan, R., Barth, E.F., and Gibbons, J.J., “Us-ing an Organophilic Clay to Chemically StabilizeWaste Containing Organic Compounds,” Haz-ardous Materials Control, Jan./Feb. 1990.

Spence, R.D., Gilliam, T.M., Morgan, I.L., and Osborne,S.C., “Stabilization/Solidification of Wastes Con-taining Volatile Organic Compounds in Commer-cial Cementitious Waste Forms,” Presented at 2ndInternational Symposium on S/S of Hazardous, Radio-active and Mixed Wastes, Williamsburg, VA, May29-Jun. 1, 1990.

Spence, R., Chemistry and Microstructure of SolidifiedWaste Forms, Lewis Publishers, Ann Arbor, MI,1992.

Swallow, K.C., Hume, D.N., and Morel, F.M., “Sorp-

tion of Copper and Lead by Hydrous FerricOxide,” Environmental Science Technology 14,No. 11, 1980, pp. 1326-31.

Takashita, I., Japan Kokai 79,162,844, 1979.United States Environmental Protection Agency, Guide

to the Disposal of Chemically Stabilized and SolidifiedWaste, SW-872, Office of Solid Waste and Emer-gency Response, Washington, DC, Sep. 1982.

United States Environmental Protection Agency, Fed-eral Register 50, No. 105, May 31, 1985, pp. 23250.

United States Environmental Protection Agency,Cleaning Up the Nation’s Waste Sites: Markets andTechnology Trends, EPA 542-H-92-012, Washing-ton, DC, April, 1993.

United States Environmental Protection Agency, Fed-eral Register 55, No. 61, Mar. 29, 1990, pp. 11798-11877.

United States Environmental Protection Agency,Federal Register 56, No. 140, Jul. 22, 1991, pp.33490-33579.

United States Environmental Protection Agency,Technical Resource Document: Solidification/Stabi-lization and its Application to Waste Materials,EPA/530/R-93/012, Office of Research andDevelopment, Washington, DC, Jun. 1993.

United States Environmental Protection Agency,Land Disposal Restrictions Phase II — UniversalTreatment Standards, and Treatment Standards forOrganic Toxicity Characteristics Wastes and NewlyListed Wastes, Final Rule, 40 CFR 148, Sep. 1994,pp. 260-261, 264-266, 268, 271.

United States Environmental Protection Agency,Innovative Treatment Technologies: Annual StatusReport (Seventh Edition) Applications of New Tech-nologies at Hazardous Waste Sites, EPA-542-R-95-008, Office of Solid Waste and Emergency Re-sponse, Sep. 1995.

U.S. Army Corps of Engineers Waterways Experi-ment Station, U.S. Patent 3,642,503, InterferenceMechanisms in Waste Stabilization/Solidification Pro-cesses, EPA 600/2-89/067, United States Environ-mental Protection Agency, Risk Reduction Engi-neering Laboratory, Cincinnati, OH, Jan. 1990.

Vail, J.G., Soluble Silicates, Reinhold, New York, 1952.Veda, S. and Ito,M., Japan Kokai 77 38,468, Mar. 25,

1977.Vejmelka, P.R., Kosher, and Hauler, W., U.S. Patent

4,533,395, Aug. 6, 1985.Wagner, H.B. and Ellis, J.R., U.S. Patent 4,211,572,

Jul. 8, 1980.Walsh, M.B., Eaton, H.C., Tittlebaum, M.E.,

Cartledge, F.K., and Chalasani, D., “The Effect ofTwo Organic Compounds on a Portland Ce-ment-Based Stabilization Matrix,” Hazardous

27

PCA EB211

Wastes & Hazardous Materials 3, No. 1, 1986.Weiner, R.F., “Acute Problems in Effluent Treat-

ment,” Plating 54, 1967, pp. 1354-6.Weitzman, L., Hamel, L.E., and Cadmus, S.R., Vola-

tile Emissions From Stabilized Waste In HazardousLandfills, U.S.EPA Contract 68-02-3993, ResearchTriangle Park, Aug. 28, 1987.

Wing, R.E., “Corn Starch Compound Recovers Met-als from Water,” Industrial Wastes, Jan./Feb. 1975,pp. 26-7.

Yagi, T., Japan Kokai 75,105,541, Aug. 20, 1975.Yagi, T. and Matsunaga, S., Japan Kokai 76,123,775,

Oct. 28, 1976.Yamagisi, H., Sakamaki, S., Nakagawa, K., and

Sirasawa, M., U.S. Patent 4,190,454, Feb. 26, 1980.Young, J.F., “A Review of the Mechanisms of Set-

Retardation of Cement Pastes Containing Or-ganic Admixtures,” Cement and Concrete Research2, No. 4, 1972.

Young, D.A., U.S. Patent 4,142,912, Mar. 6, 1979.

28


Additive Effect RelativeCost

pH Control andBuffering:

pH adjustment; removal of interferingsubstances from solution; destruction of gelsand film-formers

Lime - CaO or Ca(OH)2 Neutralizes acids, raises pH Low

Sodium hydroxide Neutralizes acids, raises pH Low

Sodium carbonate Neutralizes acids, raises pH Low

Sodium bicarbonate Buffer Low

Magnesium oxide Buffer Moderate

Ferrous sulfate Lowers pH, alkalinity Low

Sulfuric acid Lowers pH, alkalinity Low

Reduction: Alteration of valence state of metals

Ferrous sulfate Reducing agent in acid conditions Low

Sodium hydrosulfite Reducing agent in alkaline conditions Moderate

Sodium metabisulfite Reducing agent in acid conditions Low

Blast furnace slag Reducing agent Low

Metallic iron Reducing agent Low

Oxidation: Alteration of valence state of metals;destruction/conversion of interferingsubstances

Potassiumpermanganate

Powerful, non-selective oxidizing agent;alteration of biological status

High

Sodium or potassiumpersulfate

Powerful, non-selective oxidizing agent;alteration of biological status

High

Sodium or calciumhypochlorite

Non-selective oxidizing agent; alteration ofbiological status

High

Hydrogen peroxide Mild, non-selective oxidizing agent;alteration of biological status

Moderate

Speciation, Re-Speciation:

Alteration of the species of the constituentsof concern to fix metals and other ions

Carbonates With lead, forms carbonates, basiccarbonates

Low

Iron and aluminumcompounds

Various Low tomoderate

Table 1. Additives Used in Cement-based S/S

29

PCA EB211


Phosphoric acid andsalts

With lead, forms phosphate compounds thathave low solubility through a wide pH range

Low tomoderate

Sodium silicate Forms low-solubility, silicate species with avariety of metals in solution; anti-inhibitor

Low tomoderate

Sodium sulfide Forms metal sulfides, except with chromium Low

Calcium polysulfide Forms metal sulfides, except with chromium Low

Organic sulfurcompounds -thiocarbamates

Forms metal sulfides, except with chromium;safer than inorganic sulfides

Moderate

Sulfur + alkali Forms metal sulfides, except with chromium Low

Xanthates Form low-solubility starch or cellulosexanthate substrates with metals attached

Moderate

Sodium chloride Silver fixant Low

Sodium sulfate Barium fixant Low

Ferrous sulfate Removes sulfide ion from solution Low

Precipitation andFlocculation:

Aggregation of fine particles and film-formers; dispersion of oils and greases andfine particulates away from reactingsurfaces

Ferrous sulfate Co-precipitating agent Low

Proprietary organicflocculants, surfactants

Flocculants and dispersants Low tomoderate

Alcohols Wetting agent Low tomoderate

Amides Wetting agent Low tomoderate

Carboxylic acids Dispersants Moderate

Aldehydes and Ketones Dispersants Moderate

Sulfonates Dispersants Moderate

Amines Flocculants Moderate

Iron salts Flocculants Low

Magnesium salts Flocculants Low toModerate

Silica Flocculants Low

Additive Effect Relative Cost

30




Sorption, Bulking,StructuralModification:

Removal of interfering substances fromreacting surfaces; immobilization of organicspecies; free water reduction; viscositycontrol; improvement of microstructure

Activated carbon Sorbent for organics, especially VOCs,organo-metallics, and some metals

High

Organoclays Sorbent for organics High

Rubber particulate Sorbent for organics, especially SVOCs Moderate

Fly ash Sorbent for some metals and organics;pozzolanic reaction with alkalies; bulkingagent

Low

Rice hull ash Sorbent for organics, especially VOCs;reacts with alkalies to form soluble silicates

Moderate

Natural clays Sorbents for some metals; bulking agent;viscosity control

Low

Expanded minerals Sorbents for some metals; bulking agent Low tomoderate

Diatomaceous earth Sorbents for some metals; bulking agent Low tomoderate

Blast furnace slag Pozzolanic reaction with alkalies; bulkingagent; reducing agent; structuralmodification

Low

Silica fume Pozzolanic reaction with alkalies; bulkingagent; structural modification

Low

Wood chips Sorbent; bulking agent Low

Ground corn cob Sorbent; bulking agent Low

Cement kiln dust Pozzolanic bulking agent, as well asaccelerator in some cases

Low

Acceleration/Anti-Inhibition:

Counter the effects of set retarders in waste;accelerate the normal set time of cement-based systems

Calcium chloride Accelerates set Low

Calcium aluminate Accelerates set Low

Calcium sulfate Accelerates set Low

Glycols Accelerates set Moderate

31

PCA EB211



Sugar Accelerates set Moderate

Amines Accelerates set Moderate

Organic acid salts Accelerates set Moderate

Lime Supplies additional calcium for reaction;reacts with certain interfering organics; anti-inhibitor; controls biological status

Low

Sodium silicate Reacts with interfering metals; anti-inhibitor;causes acceleration of initial set; fixesmetals

Low tomoderate

Iron compounds Counters effect of tin, lead arsenates,sulfides by reaction

Low

Triethanolamine Accelerates set Moderate

Calcium formate Accelerates set Moderate

Phosphates Accelerates set Low

Bentonite Sorbs oils, organics; anti-inhibitor Low

Cement kiln dust Accelerator in some cases Low

Retardation: Retardation of setting to allow for betterprocessing control

Sugar Retards of setting at low levels Low

Sugar derivatives Retards setting Moderate

Zinc hydroxide Retards setting Low

Copper hydroxide Retards setting Low

Lead hydroxide Retards setting Low

Calcium chloride >4% Retards setting Low

Magnesium salts Retards setting Low

Tin salts Retards setting Low

Phosphates Retards setting Low

Lignosulfonic acid saltsand derivatives

Retards setting Low toModerate

Hydroxy carboxylicacids


Polyhydroxycompounds


32




Free Water Control: Control (usually reduction) of the free watercontent of the system

Slag Bulking agent; pozzolan Low

Flyash Bulking agent; pozzolan Low

Concrete waterreducing additives

Reduce water requirement whereapplicable

Low tomoderate

Cement kiln dust Bulking agent, pozzolan Low

Miscellaneous:

Biocides Counter biological activity Moderate

Organic polymers Fill pores, improve microstructure, improvedurability

Moderateto High

Air entrainmentadditives

Improve durability Low toModerate

Wood resins Improve durability Moderate

33

PCA EB211

Tab

le 3

. S

olid

ific

atio

n P

rob

lem

s

PR

OB

LE

MP

RO

BA

BLE

CA

US

E -

WA

ST

EC

HA

RA

CT

ER

IST

ICS

,IN

GR

ED

IEN

TS

AP

PR

OA

CH

TO

SO

LUT

ION

SP

EC

IFIC

AD

DIT

IVE

S O

RT

EC

HN

IQU

ES

US

ED

AD

DIT

ION

RA

TIO

RA

NG

E(w

eigh

t %)

CO

ST

RA

NG

E($

per

ton

of w

aste

trea

ted)

Will

not

set

1.

Fin

e pa

rtic

ulat

es:

silt,

clay

, co

lloid

al m

atte

r2.

A

naer

obic

con

ditio

ns3.

C

alci

um r

emov

ers

1.

Sur

face

act

ive

agen

ts:

wet

ting

agen

ts,

disp

ersa

nts,

flo

ccul

ants

2.

Aer

ate;

add

oxi

dize

r,lim

e, b

ioci

de3.

R

epla

ce lo

st c

alci

um

1.

Iron

sal

ts,

ferr

ous

sulfa

te,

mag

nesi

um s

alts

, si

lica,

as

phal

t em

ulsi

ons,

alc

ohol

sam

ides

, am

ines

, ca

rbox

ylic

acid

s, c

arbo

nyls

, su

lfona

tes

2.

Air,

oxy

gen,

lim

e,ca

lciu

m/s

odiu

m h

ypoc

hlor

ite,

prop

rieta

ry b

ioci

de3.

Li

me,

cal

cium

chl

orid

e,g

ypsu

m

1.

0.01

- 1

.02.

1

- 5

3.

1 -

10

1. <

1 -

202.

1

- 25

03.

1

-25

Set

s, b

ut d

oesn

’th

ard

en

1.

Fin

e pa

rtic

ulat

es:

silt,

clay

, co

lloid

al m

atte

r2.

A

naer

obic

con

ditio

ns

1.

Sur

face

act

ive

agen

ts:

wet

ting

agen

ts,

disp

ersa

nts,

flo

ccul

ants

2.

Aer

ate;

add

oxi

dize

r,l im

e, b

ioci

de3.

R

epla

ce lo

st c

alci

um

1.

Iron

sal

ts,

ferr

ous

sulfa

te,

mag

nesi

um s

alts

, si

l ica,

as

phal

t em

ulsi

ons,

alc

ohol

sam

ides

, am

ines

, ca

rbox

ylic

acid

s, c

arbo

nyls

, su

lfona

tes

2.

Air,

oxy

gen,

lim

e,ca

lciu

m/s

odiu

m h

ypoc

hlor

ite,

prop

rieta

ry b

ioci

de3.

Li

me,

cal

cium

chl

orid

e,g

ypsu

m

1.

0.01

- 1

.02.

1

- 5

3.

1 -

10

1. <

1 -

202.

1

- 25

03.

1

-25

34


Tab

le 3

. S

olid

ific

atio

n P

rob

lem

s (c

on

tin

ued

)

Set

is

reta

rded

1.

Fin

e pa

rtic

ulat

es:

silt,

clay

, co

lloid

al m

atte

r2.

S

ugar

3.

Pho

spha

tes

4.

Sul

fur

5.

Bic

arbo

nate

s of

sodi

um a

nd p

otas

sium

6.

Che

mic

alin

terf

eren

ce:

a.

Ino

rgan

ics:

met

alsa

lts,

sodi

um i

odat

e,so

dium

pho

spha

te,

sodi

um a

rsen

ate,

sodi

um b

orat

e, s

odiu

msu

lfide

b.

Che

latin

g ag

ents

c.

Org

anic

s7.

M

i ld a

naer

obic

cond

ition

s8.

In

suffi

cien

t cu

re t

ime

9.

Gen

eral

set

reta

rdat

ion

1.

Sur

face

act

ive

agen

ts:

wet

ting

agen

ts,

disp

ersa

nts,

flo

ccul

ants

2a.

Add

mor

e su

gar

-

0

.2%

2b.

Add

a s

orbe

nt3.

Add

cal

cium

ion

4.

Non

e es

tabl

ishe

d5.

U

se a

cidi

c m

ater

ial t

od

eco

mp

ose

6a,b

. A

dd a

n ac

cele

rato

ror

ant

i-inh

ibito

r6c

. A

dd a

sor

bent

,ox

idan

t, ac

cele

rato

r or

anti-

inhi

bito

r7.

A

erat

e; a

dd o

xidi

zer,

l ime,

bio

cide

8.

Cur

e lo

nger

9.

Add

a g

ener

alac

cele

rato

r C

alci

um c

hlor

ide

1.

Iron

sal

ts,

ferr

ous

sulfa

te,

mag

nesi

um s

alts

, si

lica,

as

phal

t em

ulsi

ons,

alc

ohol

sam

ides

, am

ines

, ca

rbox

ylic

acid

s, c

arbo

nyls

, su

lfona

tes

2a.

Sug

ar2b

. C

lay,

fly

ash,

diat

omac

eous

ear

th,

carb

on3.

Li

me,

gyp

sum

, ca

lciu

mch

lorid

e5.

A

cids

, fe

rrou

s su

lfate

6a,b

. S

ulfa

tes,

sol

uble

sil ic

ates

, al

umin

ates

,ph

osph

ates

, hy

drox

ylat

edor

gani

c ac

ids,

gly

cols

, am

ines

,iro

n co

mpo

unds

, A

ST

M s

etac

cele

rato

rs6c

. C

lay,

lim

e, li

mes

tone

,fly

ash,

car

bon;

hyd

roge

npe

roxi

de,

pota

ssiu

mpe

rman

gana

te,

sodi

umpe

rsul

fate

, ca

lciu

m/s

odiu

mhy

poch

lorit

e; a

lso

see

6a,b

ab

ove

7.

Air,

oxy

gen,

lim

e,ca

lciu

m/s

odiu

m h

ypoc

hlor

ite,

prop

rieta

ry b

ioci

de9.

C

alci

um c

hlor

ide,

sod

ium

silic

ate,

lim

e

1.

0.01

- 1

.02a

. >

0.2

2b.

.5 -

53.

1

- 5

5. 0

.1 -

10

6a,b

. 0.

01 -

56c

. 0.

1 -

107.

0.1

- 5

9.

1 -

5

1. <

1 -

202a

. <

1 -

202b

. 1

- 10

3.

1 -

55.

<1

- 5

6a,b

. 1

- 25

6c.

1 -

100

7.

2 -

109.

1

- 10

PR

OB

LE

MP

RO

BA

BLE

CA

US

E -

WA

ST

EC

HA

RA

CT

ER

IST

ICS

,IN

GR

ED

IEN

TS

AP

PR

OA

CH

TO

SO

LUT

ION

SP

EC

IFIC

AD

DIT

IVE

S O

RT

EC

HN

IQU

ES

US

ED

AD

DIT

ION

RA

TIO

RA

NG

E(w

eigh

t %)

CO

ST

RA

NG

E($

per

ton

of w

aste

trea

ted)

35

PCA EB211

Tab

le 3

. S

olid

ific

atio

n P

rob

lem

s (c

on

tin

ued

)

PR

OB

LE

MP

RO

BA

BLE

CA

US

E -

WA

ST

EC

HA

RA

CT

ER

IST

ICS

,IN

GR

ED

IEN

TS

AP

PR

OA

CH

TO

SO

LUT

ION

SP

EC

IFIC

AD

DIT

IVE

S O

RT

EC

HN

IQU

ES

US

ED

AD

DIT

ION

RA

TIO

RA

NG

E(w

eigh

t %)

CO

ST

RA

NG

E($

per

ton

of w

aste

trea

ted)

Su

pe

rna

ten

tliq

uid

on s

urfa

ceaf

ter

setti

ng(U

sual

ly d

ue t

ola

rge

part

icle

siz

ean

d/or

hig

hpa

rtic

le s

peci

ficgr

avity

in lo

wca

lciu

m/s

odiu

mhy

poch

lori

tevi

scos

itym

ed

ium

)

1.

Set

is t

oo s

low

2.

Wat

er c

onte

nt i

s to

ohi

gh3.

V

isco

sity

of

syst

em is

too

low

1.

Add

set

acc

eler

ator

or a

nti-i

nhib

itor:

2.

Dew

ater

or

sorb

wat

er3.

In

crea

se v

isco

sity

of

syst

em

1. S

ulfa

tes,

sol

uble

sili

cate

s,al

umin

ates

, ph

osph

ates

,hy

drox

ylat

ed o

rgan

ic a

cids

,gl

ycol

s, a

min

es,

iron

com

poun

ds,

AS

TM

set

acce

lera

tors

2.

Dec

ant

wat

er;

filte

r ra

ww

aste

; ad

d fly

ash,

cla

y, s

lag,

sil ic

a fu

me,

woo

d ch

ips,

grou

nd c

orn

cob,

diat

omac

eous

ear

th,

expa

nded

min

eral

s

3.

Gel

l ing

agen

t -

sodi

umsi

licat

e; s

orbe

nt -

see

(2)

ab

ove

1.

1-10

2.

5-50

3.

1-50

1.

2-20

2.

0-25

3.

0-25

Set

s to

o ra

pidl

yfo

r sa

tisfa

ctor

ypr

oces

sing

1.

Acc

eler

atin

g ag

ents

:su

lfate

s; s

olub

lesi

l icat

es,

alum

inat

es,

ph

osp

ha

tes;

hydr

oxyl

ated

org

anic

acid

s, g

lyco

ls,

othe

ror

gani

cs;

ion

exch

ange

mat

eria

l2.

C

arbo

nate

s an

dbi

carb

onat

es o

f so

dium

and

pota

ssiu

m3.

S

ugar

> 0

.2%

1.

Add

set

ret

arde

r2.

D

ecom

pose

or

neut

raliz

e w

ith a

cidi

cad

ditiv

e3a

. A

dd r

etar

der

3b.

Che

mic

al o

xida

tion

1.

Pro

prie

tary

, co

ncre

te s

etre

tard

er;

zinc

, co

pper

or

lead

oxid

e/hy

drox

ide;

cal

cium

chlo

ride

(>4%

0; m

agne

sium

and

tin s

alts

; ph

osph

ates

,cl

ays

2.

Fer

rous

sul

fate

, su

lfuric

aci

d3a

. S

ee (

1) a

bove

3b.

Hyd

roge

n pe

roxi

de,

calc

ium

/sod

ium

hyp

ochl

orite

,po

tass

ium

per

man

gana

te,

sodi

um p

ersu

lfate

1.

0.01

- 5

2.

1 -

103a

. 0

.01

- 5

3b.

1 -

10

1.

2 -

52.

<1

- 20

3a.

2 -

53b

. 5

- 2

50

36


PR

OB

LE

MP

RO

BA

BLE

CA

US

E -

WA

ST

EC

HA

RA

CT

ER

IST

ICS

,IN

GR

ED

IEN

TS

AP

PR

OA

CH

TO

SO

LUT

ION

SP

EC

IFIC

AD

DIT

IVE

S O

RT

EC

HN

IQU

ES

US

ED

AD

DIT

ION

RA

TIO

RA

NG

E(w

eigh

t %)

CO

ST

RA

NG

E($

per

ton

of w

aste

trea

ted)

Tab

le 3

. S

olid

ific

atio

n P

rob

lem

s (c

on

tin

ued

)

Insu

ffic

ient

un

con

fine

dco

mpr

essi

vest

reng

th (

AS

TM

D-2

166,

D-1

633)

1.

Che

mic

alin

terf

eren

ce:

met

al s

alts

,le

ad n

itrat

e, s

odiu

mio

date

, so

dium

phos

phat

e, s

odiu

mar

sena

te,

sodi

umbo

rate

, so

dium

sul

fide

2.

Sod

ium

sul

fide,

sodi

um s

ulfit

e, s

odiu

mhy

drox

ide

3.

Sug

ar4.

A

lgae

5.

Ana

erob

ic c

ondi

tions

6.

Oil

and

grea

se7.

P

heno

l8.

W

ater

con

tent

too

high

9.

Cem

ent

cont

ent

too

low

1. A

dd a

n ac

cele

rato

r or

anti-

inhi

bito

r2.

Ir

on s

alts

; ch

emic

alox

idat

ion;

aci

d3.

C

hem

ical

oxi

datio

n

4a.

Add

sor

bent

4b.

Che

mic

al o

xida

tion

4c.

Add

lim

e4d

. A

dd b

ioci

de5.

A

erat

e; a

dd o

xidi

zer,

l ime,

bio

cide

6a.

Che

mic

al o

xida

tion

6b.

Add

sor

bent

6c.

Add

che

mic

als

7.

Che

mic

al o

xida

tion

8a.

Dew

ater

or

sorb

wat

er9.

A

dd m

ore

cem

ent

1.

Sul

fate

s, s

olub

le s

ilica

tes,

alum

inat

es,

phos

phat

es,

hydr

oxyl

ated

org

anic

aci

ds,

glyc

ols,

am

ines

, iro

nco

mpo

unds

, A

ST

M s

etac

cele

rato

rs2a

. F

erro

us s

ulfa

te2b

. H

ydro

gen

pero

xide

,ca

lciu

m/s

odiu

m h

ypoc

hlor

ite3a

. H

ydro

gen

pero

xide

,po

tass

ium

per

man

gana

te,

sodi

um p

ersu

lfate

,ca

lciu

m/s

odiu

m h

ypoc

hlor

ite4a

. C

lays

, l im

esto

ne,

flyas

h4b

. S

ee (

3a)

5.

A

ir, o

xyge

n, li

me,

calc

ium

/sod

ium

hyp

ochl

orite

,pr

oprie

tary

bio

cide

6a.

See

(3a

)6b

. F

lyas

h, b

ento

nite

,l im

esto

ne6c

. Q

uick

l ime,

ste

arat

es7.

P

otas

sium

per

man

gana

te,

sodi

um p

ersu

lfate

8.

Dec

ant

wat

er;

filte

r ra

ww

aste

; ad

d fly

ash,

cla

y, s

lag,

sil ic

a fu

me,

woo

d ch

ips,

grou

nd c

orn

cob,

diat

omac

eous

ear

th,

expa

nded

min

eral

s

1.

1 -

102a

. 1

- 1

02b

. 1

- 1

03.

1

- 10

4a.

2 -

10

4b.

1 -

10

4c.

2 -

10

4d.

0.0

1 -

15.

1

- 10

6a.

1 -

10

6b.

2 -

10

6c.

2 -

10

7.

2 -

108.

5

- 50

1.

2 -

202a

. 2

- 2

02b

. 5

- 2

003.

5

- 25

0

4a.

1 -

54b

. 5

- 2

504c

. 2

- 1

04d

. <

1 -

205.

5

- 20

06a

. 5

- 2

506b

. 1

- 5

6c.

2 -

50

7.

5 -

250

8.

2 -

20

37

PCA EB211

Tab

le 3

. S

olid

ific

atio

n P

rob

lem

s (c

on

tin

ued

)

PR

OB

LE

MP

RO

BA

BLE

CA

US

E -

WA

ST

EC

HA

RA

CT

ER

IST

ICS

,IN

GR

ED

IEN

TS

AP

PR

OA

CH

TO

SO

LUT

ION

SP

EC

IFIC

AD

DIT

IVE

S O

RT

EC

HN

IQU

ES

US

ED

AD

DIT

ION

RA

TIO

RA

NG

E(w

eigh

t %)

CO

ST

RA

NG

E($

per

ton

of w

aste

trea

ted)

Pe

rme

ab

ility

to

oh

igh

(S

W8

46

,M

eth

od

91

00

)

1.

In

com

ple

te c

uri

ng

2.

In

suff

icie

nt

cem

en

t3

. H

igh

wa

ste

pe

rme

ab

ility

1.

Cu

re f

or

at

lea

st 2

8d

ays

2.

Use

mo

re c

em

en

t3

a.

Ad

d l

ow

pe

rme

ab

ility

ad

diti

ve3

b.

Ad

dh

ydro

ph

ob

izin

g a

ge

nt

3c.

F

ill p

ore

s w

ith w

ate

rre

sist

an

t m

ate

ria

l3

d.

De

velo

p b

ete

rm

icro

stru

ctu

re

2.

Po

rtla

nd

ce

me

nt

3a

. B

en

ton

ite c

lay

3b

. E

mu

lsifi

ed

asp

ha

lt,st

ea

rate

s3

c.

La

tex

or

oth

er

wa

ter-

com

pa

tible

po

lym

er

3d

. F

lya

sh,

bla

st f

urn

ace

sla

g,

silic

a f

um

e

3a

. 5

- 3

03

b.

1 -

53

c.

5 -

10

3a

. 5

- 3

03

b.

1 -

53

c.

50

- 1

00

Po

or

du

rab

il ity

(AS

TM

D-4

84

2-

90

, D

-48

43

-88

)

1.

In

suff

icie

nt

cem

en

t2

. P

oo

r m

icro

stru

ctu

re3

. E

xce

ssiv

e p

oro

sity

4.

La

rge

am

ou

nts

of

solu

ble

sa

lts s

ulfa

tes,

chlo

rid

es,

nitr

ate

s

1.

Ad

d m

ore

ce

me

nt

2a

. A

dd

fly

ash

, si

lica

fum

e2

b.

Air

en

tra

inm

en

t3

a.

Mo

dify

wa

ter

con

ten

t3

b.

Ad

d b

ulk

ing

ag

en

to

r w

ate

r a

bso

rbe

r3

c.

Ad

d p

ore

fill

ing

ag

en

t3

d.

Ad

dh

ydro

ph

ob

izin

g a

ge

nt

4.

No

ne

re

po

rte

d

1.

Po

rtla

nd

ce

me

nt

2a

. F

lya

sh,

silic

a f

um

e2

b.

Use

air

en

tra

inin

g a

ge

nt,

pro

cess

to

en

tra

in a

ir3

a.

De

can

t w

ate

r; f

ilte

r ra

ww

ast

e3

b.

Fly

ash

, cl

ay,

sla

g,

silic

afu

me

, w

oo

d c

hip

s, g

rou

nd

co

rnco

b,

dia

tom

ace

ou

s e

art

h,

exp

an

de

d m

ine

rals

3

c.

La

tex

or

oth

er

wa

ter-

com

pa

tible

po

lym

er

3d

.

Em

uls

ifie

d a

sph

alt,

ste

ara

tes

2a

. 5

- 2

52

b.

0.0

1 -

13

b.

5 -

25

3c.

5

- 1

03

d.

1 -

5

2a

. 2

- 2

02

b.

2 -

20

3b

. 2

- 1

03

c.

50

- 1

00

3d

. 1

- 5

38


Tab

le 7

. S

tab

iliza

tio

n o

f M

etal

s

Pro

blem

or

Tar

get

Con

stitu

ent

orS

peci

esA

ppro

ach

to S

olut

ion*

Spe

cific

Add

itive

s U

sed*

Add

ition

Rat

ioR

an

ge

(wei

ght %

)

Cos

t R

ange

($ p

er t

on o

fw

aste

trea

ted)

An

timo

ny

Ars

enic

tris

ulfid

e1.

O

xida

tion

to A

s+5 f

ollo

wed

by

2.

P

reci

pita

tion

with

cal

cium

1.

Cal

cium

/sod

ium

hyp

ochl

orite

or

pota

ssiu

m p

erm

anga

nate

2.

Lim

e

1.

1 -

202.

5

- 10

1.

20 -

400

2.

5 -

10

Ars

enic

com

plex

es

1.

Imm

obili

ze b

y so

rptio

n2.

D

estr

oy c

ompl

ex b

y ox

idat

ion

1.

Act

ivat

ed c

arbo

n2.

P

otas

sium

per

man

gana

te,

sodi

umpe

rsul

fate

1.

1 -

102.

5

- 10

1.

20 -

200

2.

100

- 20

0

Bar

ium

, so

lubl

eco

mp

ou

nd

sP

reci

pita

te a

s su

lfate

Cal

cium

sul

fate

(gy

psum

)1

- 5

1 -

5

Ber

yll iu

m

Cad

miu

m,

sim

ple

Rai

se p

HLi

me,

lim

esto

ne,

high

-fre

e-l im

e ce

men

tki

ln d

ust

5 -

105

- 10

Cad

miu

m c

yani

deD

estr

oy c

ompl

ex b

y al

kal in

eox

idat

ion

Cal

cium

/sod

ium

hyp

ochl

orite

or

hydr

ogen

per

oxid

e1

- 10

20 -

200

Chr

omiu

m,

sim

ple

Chr

omiu

m a

s C

r+6

Red

uce

to C

r+3

Fer

rous

sul

fate

, so

dium

bis

ulfit

e or

met

abis

ulfit

e, o

r so

dium

hyd

rosu

lfite

5 -

2010

- 1

20

Chr

omiu

mco

mpl

exes

Imm

obil i

ze b

y so

rptio

nA

ctiv

ated

car

bon

1 -

1020

- 2

00

Lead

, si

mpl

e1.

C

o-pr

ecip

itate

2.

Spe

ciat

e as

car

bona

te,

basi

cca

rbo

na

te3.

S

peci

ate

as s

ulfid

e

1.

Fer

rous

sul

fate

2.

Cal

cium

car

bona

te,

sodi

umca

rbo

na

te3.

S

odiu

m s

ulfid

e or

org

ano-

sulfu

rco

mp

ou

nd

s

1.

5 -

102.

5

- 20

3.

0.1

- 5

1.

10 -

20

2.

2 -

103.

2

- 40

Lead

, co

mpl

exed

1.

Imm

obil i

ze b

y so

rptio

n2.

D

estr

oy c

ompl

ex b

y ox

idat

ion

1.

Act

ivat

ed c

arbo

n2.

C

alci

um/s

odiu

m h

ypoc

hlor

ite,

pota

ssiu

m p

erm

anga

nate

, so

dium

pers

ulfa

te

1.

1 -

102.

5

- 10

1.

20 -

200

2.

100

- 20

0

Not

e:M

etal

s or

met

als

spec

ies

that

are

ade

quat

ely

stab

ilize

d by

cem

ent a

lone

are

sha

ded.

39

PCA EB211

Lead

, el

emen

tal

Incl

ude

a so

urce

of

carb

onat

e to

re-

spec

iate

lead

as

it di

ssol

ves

Cal

cium

car

bona

te,

sodi

um c

arbo

nate

5 -

202

- 10

Mer

cury

, si

mpl

eS

peci

ate

as s

ulfid

e1.

S

odiu

m s

ulfid

e or

org

ano-

sulfu

rco

mp

ou

nd

s2.

S

ulfu

r +

alk

ali

1.

0.1

- 5

2.

1 -

101.

2

- 40

2. <

1 -

5

Nic

kel,

sim

ple

Spe

ciat

e as

sul

fide

Sod

ium

sul

fide

or o

rgan

o-su

lfur

com

po

un

ds

0.1

- 5

2 -

40

Nic

kel c

yani

deD

estr

oy c

ompl

ex b

y al

kalin

eox

idat

ion

Cal

cium

/sod

ium

hyp

ochl

orite

or

hydr

ogen

per

oxid

e1

- 10

20 -

200

Nic

kel c

ompl

exes

1.

Imm

obil i

ze b

y so

rptio

n2.

D

estr

oy c

ompl

ex b

y ox

idat

ion

1.

Act

ivat

ed c

arbo

n2.

P

otas

sium

per

man

gana

te,

sodi

umpe

rsul

fate

1.

1 -

102.

5

- 10

1.

20 -

200

2.

100

- 20

0

Sel

eniu

m,

sim

ple

Sel

eniu

m,

sele

nate

Co-

prec

ipita

teF

erro

us s

ulfa

te1

- 5

2 -

10

Silv

er,

sim

ple

Silv

er,

high

leve

lP

reci

pita

te a

s ch

lorid

eS

odiu

m c

hlor

ide

0.1

- 1

<1

- 1

Tha

ll ium

Va

na

diu

m

Zin

c

Met

als,

ele

men

tal,

finel

y di

vide

dD

e-ac

tivat

e by

dis

solu

tion

ifpy

roph

oric

Aci

ds1

-10

<1

- 5

Tab

le 7

. S

tab

iliza

tio

n o

f M

etal

s (c

on

tin

ued

)

Pro

blem

or

Tar

get

Con

stitu

ent

orS

peci

esA

ppro

ach

to S

olut

ion*

Spe

cific

Add

itive

s U

sed*

Add

ition

Rat

ioR

an

ge

(wei

ght %

)

Cos

t R

ange

($ p

er t

on o

fw

aste

trea

ted)

*It

is a

ssum

ed th

at th

e tr

eatm

ent i

s be

ing

done

in th

e co

ntex

t of a

cem

ent-

base

d S/

S sy

stem

. Th

eref

ore,

mul

tiste

p tr

eatm

ent r

equi

ring

prec

ipita

tion

or s

peci

atio

n by

cem

ent i

n th

e la

st s

tep

is a

ssum

ed in

the

tabl

e an

d is

not

spe

lled

out.

40


Con

tam

inan

tA

dditi

ve U

sed

(X)

Fly

ash/

Bed

Ash

Hyd

rate

dLi

me

FeS

O4

CaC

O3

Na

2CO

3N

aCl

Na

2SO

4O

rgan

o-S

ulfu

rC

arbo

nC

a(O

Cl)

2/N

aOC

lK

MnO

4/(N

H4) 2

S2O

8

Na

2S2O

4N

a2S

/S

ulfu

r

Ant

imon

y

Ars

enic

- A

s+5,

conv

entio

nal

X

Ars

enic

- A

s+3X

XX

X

Ars

enic

-or

gano

-co

mpo

unds

XX

XX

Bar

ium

XX

Ber

yll iu

m

Cad

miu

mX

X

Chr

omiu

m -

Cr+3

,co

nven

tiona

l

X

Chr

omiu

m -

Cr+6

,he

xava

lent

XX

X

Chr

omiu

m -

com

plex

esX

Lead

-co

nven

tiona

lX

XX

XX

Lead

-or

gano

-co

mpo

unds

XX

X

Tab

le 8

. G

ener

al A

dd

itiv

e U

tiliz

atio

n L

ist,

Met

als

41

PCA EB211

Tab

le 8

. G

ener

al A

dd

itiv

e U

tiliz

atio

n L

ist,

Met

als

(co

nti

nu

ed)

Con

tam

inan

tA

dditi

ve U

sed

(X)

Flya

sh/

Bed

Ash

Hyd

rate

dLi

me

FeS

O4

CaC

O3

Na

2CO

3N

aCl

Na

2SO

4O

rgan

o-S

ulfu

rC

arbo

nC

a(O

Cl)

2/N

aOC

lK

MnO

4/(N

H4) 2

S2O

8

Na

2S2O

4N

a2S

/S

ulfu

r

Ati

Lead

-el

emen

tal

X

Mer

cury

-co

nven

tiona

lX

XX

Mer

cury

-or

gano

-co

mpo

unds

XX

Mer

cury

-el

emen

tal

X

Nic

kel -

conv

entio

nal

XX

Nic

kel -

cyan

ide

com

plex

es

XX

X

Nic

kel -

orga

no-

com

poun

ds

XX

X

Sel

eniu

m -

conv

entio

nal

X

Sel

eniu

m -

sele

nate

*X

Silv

erX

X

Tha

ll ium

42


Con

tam

inan

tA

dditi

ve U

sed

(X)

Fly

ash/

Bed

Ash

Hyd

rate

dLi

me

FeS

O4

CaC

O3

Na

2CO

3N

aCl

Na

2SO

4O

rgan

o-S

ulfu

rC

arbo

nC

a(O

Cl)

2/N

aOC

lK

MnO

4/(N

H4) 2

S2O

8

Na

2S2O

4N

a2S

/S

ulfu

r

Tab

le 8

. G

ener

al A

dd

itiv

e U

tiliz

atio

n L

ist,

Met

als

(co

nti

nu

ed)

*St

ront

ium

is r

epor

ted

to b

e us

eful

in s

tabi

lizat

ion

of s

elen

ate

ion

Va

na

diu

m

Zin

cX

43

PCA EB211

TA

RG

ET

CO

NS

TIT

UE

NT

UTS

LE

VE

L

TC

LP T

ES

TIN

G (

mg/

l)T

CA

TE

ST

ING

(m

g/kg

)

Un

-tr

ea

ted

Tre

ated

Add

itive

Add

ition

Rat

io(%

)

Un

-tr

ea

ted

Tre

ated

Add

itive

Add

ition

Rat

io(%

)

Ace

ton

e16

0

12

0.5

17

.25

KA

X-5

0™

10

918

<

20

0K

AX

-10

0™

10

Be

nze

ne

10

26

.5<

1.2

5C

arbo

n1

041

8

26

.4K

AX

-10

0™

10

2-B

utan

one

(Met

hyl

ethy

l ke

tone

)36

6

8.0

6.0

Car

bon

10

430

9

5.8

Car

bon

10

Car

bon

Dis

ulfid

e

4

.8*

5.0

<0

.25

***

10

83

<0

.25

Non

e-

Car

bon

Tet

rach

lorid

e6

1

8.0

<1

.25

Car

bon

10

429

1

4.5

KA

X-1

00

™1

0

Ch

loro

be

nze

ne

6

35

.5<

1.2

5C

arbo

n1

014

00

40

2C

arbo

n1

0

Chl

orof

orm

6

48

.5<

2.5

KA

X-

10

0™

10

431

9.

8K

AX

-10

0™

10

1,2-

Dic

hlor

oeth

ane

6

68

.5<

2.5

KA

X-

10

0™

10

654

<

0.2

5K

AX

-10

0™

10

1,1-

Dic

hlor

oeth

ylen

e6

-

--

-2

.24

<

0.2

5O

-cla

y1

0

Eth

yl A

ceta

te33

2

9.5

<0

.25

KA

X-5

0™

10

258

<

0.2

5**

10

Eth

yl B

enze

ne10

1

1.0

<2

.5**

**1

010

40

2.6

3C

arbo

n1

0

Met

hyle

ne C

hlor

ide

30

15

.0<

0.2

5K

AX

-50

™1

062

<

0.2

5K

AX

-10

0™

10

4-M

ethy

l-2-P

enta

none

(M

ethy

l is

obut

ylke

tone

)3

31

04

.5<

2.5

Car

bon

10

1030

6

10

KA

X-1

00

™1

0

Tet

rach

loro

ethy

lene

6

22

.0<

1.2

5C

arbo

n1

019

80

61

5K

AX

-10

0™

10

To

lue

ne

10

33

.5<

1.2

5C

arbo

n1

093

8

25

6K

AX

-10

0™

10

1,1

,1-T

richl

oroe

than

e6

3

4.5

<0

.25

KA

X-5

0™

10

550

<

0.2

5K

AX

-10

0™

10

Tric

hlor

oeth

ylen

e6

4

4.5

<1

.25

Car

bon

10

881

8

9.1

KA

X-1

00

™1

0

Tab

le 9

. S

tab

iliza

tio

n o

f V

ola

tile

Org

anic

s

44


TA

RG

ET

CO

NS

TIT

UE

NT

UTS

LE

VE

L

TC

LP T

ES

TIN

G (

mg/

l)T

CA

TE

ST

ING

(m

g/kg

)

Un

-tr

eate

dT

reat

edA

dditi

veA

dditi

onR

atio

(%)

Un

-tr

eate

dT

reat

edA

dditi

veA

dditi

onR

atio

(%)

Tab

le 9

. S

tab

iliza

tio

n o

f V

ola

tile

Org

anic

s (c

on

tin

ued

)

Tri

chlo

roflu

orom

etha

ne30

-

--

-0

.49

<

0.2

5N

one

-

1,1

,2-T

richl

oro

-1,2

,2-T

riflu

oroe

than

e30

-

--

-9.

1

<0

.25

***

10

Tot

al X

ylen

es30

1

1.0

<1

.25

Car

bon

10

1070

1

74

Car

bon

10

N-B

utan

ol2.

6

55

.03

1.4

KA

X-5

0™

10

3350

<

5K

AX

-10

0™

10

Cyc

loh

exa

no

ne

0

.75*

--

--

536

<

5K

AX

-10

0™

10

Iso-

But

yl A

lcoh

ol17

0

--

--

2100

<

5K

AX

-10

0™

10

Me

tha

no

l

0.75

*2

33

.05

0.4

Car

bon

10

2337

4

44

KA

X-1

00

™1

0

Not

e:

“O-c

lay”

= o

rgan

ocla

y

* =

TLC

P

**

= C

arbo

n, O

-cla

ys, o

r K

AX

-100

™

***

= O

-cla

y or

KA

X-1

00™

*

***

= C

arbo

n or

O-c

lays

45

PCA EB211

Tab

le 1

0. S

tab

iliza

tio

n o

f S

emi-

Vo

lati

le O

rgan

ics

TA

RG

ET

CO

NS

TIT

UE

NT

UT

SL

EV

EL

TC

LP T

ES

TIN

G (

mg/

l)T

CA

TE

ST

ING

(m

g/kg

)

Un-

tre

ate

dT

rea

ted

Ad

diti

veA

dd

itio

nR

atio

(%)

Un-

tre

ate

dT

rea

ted

Ad

diti

veA

dd

itio

nR

atio

(%

)

An

thra

cen

e3.

4

0.0

32

<0

.02

**1

054

4

6.9

KA

X-5

0™

10

Bis

(2-E

thyl

hexy

l) P

htha

late

28

0.5

2<

0.0

2K

AX

-50

™1

077

6

<0

.99

KA

X-5

0™

10

1,2-

Dic

hlor

oben

zene

6

2.1

<0

.02

Ca

rbo

n1

042

9

6.7

8K

AX

-50

™1

0

1,4-

Dic

hlor

oben

zene

6

1.8

6<

0.0

2C

arb

on

10

461

6

.03

KA

X-5

0™

10

2,4-

Din

itrot

olue

ne14

0

6.2

6<

0.0

2C

arb

on

10

438

<

0.9

9K

AX

-50

™1

0

He

xach

loro

be

nze

ne

10

--

--

440

6

.96

KA

X-5

0™

10

He

xach

loro

bu

tad

ien

e5.

6

0.1

4<

0.0

2*

10

620

1

0K

AX

-50

™1

0

He

xach

loro

eth

an

e30

0

.38

<0

.02

Ca

rbo

n1

038

1

6.4

6K

AX

-50

™1

0

4-M

ethy

l ph

enol

5.6

12

.2<

0.1

**1

0

Na

ph

tha

len

e5.

6

2.1

--

-58

4

6K

AX

-50

™1

0

Nitr

ob

en

zen

e14

1

1.6

0.0

5C

arb

on

10

372

3

.66

KA

X-5

0™

10

Pe

nta

chlo

rop

he

no

l7.

4

2.3

<0

.2**

*1

015

2

<1

.8*

10

Pyr

idin

e16

3

0.2

28

.2C

arb

on

10

1900

3

5.1

KA

X-5

0™

10

2,4,

5-T

rich

loro

phen

ol7.

4

8.2

<0

.5*

10

132

3

.37

Ca

rbo

n1

0

2,4,

6-T

rich

loro

phen

ol7.

4

13

.7<

0.1

K

AX

-50

™1

095

2

<0

.99

KA

X-5

0™

10

Not

e:

* =

Car

bon

or K

AX

-50™

/KA

X-1

00™

**

= C

arbo

n, O

-cla

ys, o

r K

AX

-100

™ *

** =

Car

bon

or O

-cla

ys

46


TA

RG

ET

CO

NS

TIT

UE

NT

UTS

LE

VE

L

TC

LP T

ES

TIN

G (

mg/

l)T

CA

TE

ST

ING

(m

g/kg

)

Un

-tr

ea

ted

Tre

ate

dA

dditi

veA

dditi

onR

atio

(%)

Un

-tr

ea

ted

Tre

ate

dA

dditi

veA

dditi

onR

atio

(%)

gam

ma-

BH

C (

Lind

ane)

0.0

66

1.5

<0

.2*

10

25

<5

.0K

AX

-1

00

™1

0

Hep

tach

lor

0.0

66

0.4

<0

.00

8**

10

16

35

4O

-cla

ys1

0

End

rin0

.13

0.3

<0

.02

**2.

60.

8C

arbo

n1

0

Met

hoxy

chlo

r0

.18

<1

0.

<0

.2**

10

1.1

0.2

8C

arbo

n1

0

Chl

orda

ne0

.26

<0

.03

<0

.03

***

10

52

5.6

Car

bon

10

To

xap

he

ne

2.6

<0

.5<

0.5

***

10

68

26

Car

bon

10

2,4-

Dic

hlor

ophe

noxy

acet

ic a

cid

10

<0

.1<

0.1

***

10

26

00

01

7K

AX

-1

00

™1

0

N

otes

:

“O-c

lay”

= o

rgan

ocla

y

*

= O

-cla

y or

KA

X-5

0™/K

AX

-100

™

** =

Car

bon

***

= C

arbo

n, O

-cla

y or

KA

X-5

0™//1

00™

Tab

le 1

1. S

tab

iliza

tio

n o

f P

esti

cid

es a

nd

Her

bic

ides

47

PCA EB211

Tab

le 1

2. G

ener

al A

dd

itiv

es U

tiliz

atio

n L

ist,

Org

anic

s

TA

RG

ET

CO

NS

TIT

UE

NT

CA

RB

ON

OR

GA

NO

-CLA

YR

UB

BE

RP

AR

TIC

ULA

TE

KA

X-5

0™

MO

DIF

IED

RU

BB

ER

PA

RT

ICU

LAT

EK

AX

-10

0™

TC

LPTC

AT

CLP

TCA

TC

LPTC

AT

CLP

TCA

VO

Cs

XX

XX

XX

X

Sem

i-VO

Cs

XX

XX

XX

XX

PC

Bs

NR

ND

NR

ND

NR

ND

NR

ND

Pes

ticid

es,

Her

bici

des

XX

XX

XX

XX

Org

ano-

met

all ic

sX

ND

ND

ND

XN

DX

ND

Pol

y N

ucle

ar A

rom

atic

s (P

NA

s)X

XX

XX

XX

Alc

ohol

sX

ND

ND

XX

NR

= N

ot R

equi

red

ND

= N

o D

ata

48


KEYWORDS: additives, cement, compressive strength, durability, fixation, heavy metals, immobilization,metals, organics, organo-metallics, permeability, portland cement, solidification, soluble salts, stabilization.

ABSTRACT: Portland cement-based stabilization/solidification (S/S) has been used to successfully treat a widevariety of wastes. Some situations (because of the waste itself, the disposal scenario, and/or the regulatoryrequirements) require the use of additives or physical/chemical techniques to improve the effectiveness ofcement-based S/S. The problems encountered in S/S can be broadly classified into solidification problems, i.e.obtaining the required physical properties in the treated waste, and stabilization problems, i.e. adequatelyimmobilizing the hazardous constituents of the waste. The Guide lists additives and techniques that can beapplied to specific solidification problems such as problems in development of set, compressive strength, andfree liquids. Also included are lists of additives and techniques that can be applied to immobilization of specifichazardous constituents such as lead, cadmium, and chromium, as well as classes of constituents such as volatileorganics, organo-metallics and soluble salts. The Guide lists a variety of generic additives for specific desiredstabilization/solidification effects, including those that can be used to control the pH of wastes; to reduce,oxidize, and co-precipitate constituents; and to accelerate or retard set.

This publication is intended SOLELY for use by PROFESSIONALPERSONNEL who are competent to evaluate the significance andlimitations of the information provided herein, and who will accepttotal responsibility for the application of this information. The PortlandCement Association DISCLAIMS any and all RESPONSIBILITY andLIABILITY for the accuracy of and the application of the informationcontained in this publication to the full extent permitted by law.

Portland Cement Association 5420 Old Orchard Road, Skokie, Illinois 60077-1083, (847) 966-6200, Fax (847) 966-9781

An organization of cement manufacturers to improve and extend the usesof portland cement and concrete through market development, engineer-ing, research, education and public affairs work.

Printed in U.S.A. EB211.01W

guide to improving the effectiveness of cement-based ... · organo-metallics ... effectiveness of...

Documents