by shabnam mostary - university of...

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TRACE METALS LEACHABILITY CHARACTERIZATION OF PHOSPHOGYPSUM

By

SHABNAM MOSTARY

A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT

OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING

UNIVERSITY OF FLORIDA

2011

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© 2011 Shabnam Mostary

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To my Parents for all their love and support

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ACKNOWLEDGMENTS

I would like to thank my committee chairman, Dr. Timothy G. Townsend for his

patience and encouragement throughout my graduate program. I also wish to thank the

remaining members of my committee, Dr. Paul A. Chadik and Dr. Ben Koopman for

their insight and review of this thesis.

I would also like to thank my fellow graduate students in Solid and Hazardous

Waste, for their assistance and support with this study.

Final thanks are extended to Mosaic Fertilizer, LLC, for supporting this research.

Special thanks go to Elizabeth Foeller (Research & Development Manager) and

Charlotte Brittain (Engineering Superintendent Environmental Solutions). Also I want to

thank the Solid Waste Management Division in Polk County, Florida for their help.

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TABLE OF CONTENTS page

ACKNOWLEDGMENTS .................................................................................................. 4

LIST OF TABLES ............................................................................................................ 7

LIST OF FIGURES ........................................................................................................ 10

LIST OF ABBREVIATIONS ........................................................................................... 13

ABSTRACT ................................................................................................................... 15

CHAPTER

1 INTRODUCTION .................................................................................................... 17

1.1 Phosphogypsum and Its Management .............................................................. 17

1.2 Objectives ......................................................................................................... 19

2 LITERATURE REVIEW .......................................................................................... 20

2.1 Phosphoric Acid Production .............................................................................. 20

2.2 Potential Uses of Phosphogypsum ................................................................... 22

2.3 Leaching Tests in Solid Waste Management .................................................... 23

2.3.1 Toxicity Characteristic Leaching Procedure (TCLP) ................................ 24

2.3.2 Synthetic Precipitation Leaching Procedure (SPLP)................................ 25

2.3.3 The US EPA Multiple Extraction Procedure (MEP) ................................. 25

2.4 Leaching Tests for Assessing the Potential for Groundwater Contamination ... 26

2.5 Characteristics of Phosphogypsum................................................................... 27

2.6 Phosphogypsum Leaching Studies ................................................................... 28

3 METHODS AND MATERIALS ................................................................................ 33

3.1 Overview ........................................................................................................... 33

3.2 Sample Collection and Processing ................................................................... 33

3.3 Leaching Procedures ........................................................................................ 34

3.3.1 Toxicity Characteristic Leaching Procedure ............................................ 34

3.3.2 Synthetic Precipitation Leaching Procedure ............................................ 35

3.3.3 Extraction Procedure (EP) Toxicity Test Method ..................................... 35

3.3.4 Multiple Extraction Procedure .................................................................. 36

3.3.5 Batch Leaching Test with MSW Leachate ............................................... 36

3.3.5.1 Sulfate analysis .............................................................................. 37

3.3.5.2 Total dissolved solids (TDS) .......................................................... 37

3.3.6 Batch Leaching Test with DI Water ......................................................... 38

3.4 Total Metal Analysis .......................................................................................... 38

3.5 pH of Phosphogypsum ...................................................................................... 39

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3.6 Quality Assurance and Quality Control ............................................................. 39

4 RESULTS ............................................................................................................... 40

4.1 Total Metal Analysis Results ............................................................................. 40

4.2 pH of Phosphogypsum ...................................................................................... 41

4.3 Toxicity Characteristic Leaching Procedure (TCLP) ......................................... 41

4.4 Synthetic Precipitation Leaching Procedure (SPLP) ......................................... 42

4.5 Extraction Procedure Toxicity ........................................................................... 42

4.6 USEPA Multiple Extraction Procedure .............................................................. 43

4.7 Additional Leaching Testing .............................................................................. 43

4.7.1 The Deionized Water Batch Leaching Test ............................................. 43

4.7.2 Batch Leaching Test with MSW Leachate ............................................... 44

5 DISCUSSION ......................................................................................................... 88

5.1 Comparison to Previous Studies ....................................................................... 88

5.2 Discussion of Leaching Results ........................................................................ 89

5.3 Assessing Potential for Beneficial Reuse .......................................................... 91

5.4 Limitations and Recommendations ................................................................... 94

6 CONCLUSION ........................................................................................................ 99

APPENDIX

A ICP-AES DETECTION LIMITS ............................................................................. 101

B TOTAL METAL ANALYSIS DATA ........................................................................ 102

C TOXICITY CHARACTERISTIC LEACHING PROCEDURE DATA ....................... 106

D SYNTHETIC PRECIPITATION LEACHING PROCEDURE (SPLP) DATA ........... 110

E EXTRACTION PROCEDURE TOXICITY TEST DATA ......................................... 114

F MUTIPLE EXTRACTION PROCEDURE TEST DATA .......................................... 115

G BATCH LEACHING TEST WITH DI WATER ........................................................ 124

H MSW LEACHATE BATCH LEACHING TEST DATA ............................................ 128

I QUALITY ASSURANCE/QUALITY CONTROL .................................................... 132

LIST OF REFERENCES ............................................................................................. 137

BIOGRAPHICAL SKETCH .......................................................................................... 141

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LIST OF TABLES

Table page 2-1 Active phosphate rock mines in the United States in 2007 (USGS 2007) ........... 31

2-2 RCRA toxicity characteristics limits (metals only) ............................................... 31

2-3 US EPA drinking water standards ...................................................................... 31

2-4 Content of some trace elements in Phosphogypsum (PG) produced from different rock phosphate sources ........................................................................ 32

4-1 Metal concentrations (mg/kg) of PG samples ..................................................... 45

4-2 pH of PG samples .............................................................................................. 45

4-3 Total metal comparison with risk based standards for direct exposure .............. 46

4-4 pH results (Extraction Procedure Toxicity Test) .................................................. 46

4-5 pH results (Multiple Extraction Procedure Test) ................................................. 46

4-6 pH results (Batch leaching test with DI water) .................................................... 47

4-7 pH results (Batch leaching test with MSW leachate) .......................................... 47

5-1 TCLP results found in the previous studies ........................................................ 95

5-2 Comparisons of DI water leaching test ............................................................... 95

5-3 Comparison of SPLP with previous leaching studies .......................................... 95

5-4 Comparison of trace metal concentrations (mg/kg) ............................................ 96

A-1 Method Detection Limits ................................................................................... 101

B-1 Total metal analysis results of PG samples collected from north wall (mg/Kg) . 102

B-2 Total metal analysis results of PG samples collected from south wall (mg/Kg) 103

B-3 Total metal analysis results of PG samples collected from east wall (mg/Kg) .. 104

B-4 Total metal analysis results of PG samples collected from west wall (mg/Kg).. 105

C-1 TCLP test results of the samples collected from north wall (mg/L) ................... 106

C-2 TCLP test results of the samples collected from south wall (mg/L) .................. 107

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C-3 TCLP test results of the samples collected from east wall (mg/L) .................... 108

C-4 TCLP test results of the samples collected from west wall (mg/L) .................... 109

D-1 SPLP test results of the samples collected from north wall (mg/L) ................... 110

D-2 SPLP test results of the samples collected from south wall (mg/L) .................. 111

D-3 SPLP test results of the samples collected from east wall (mg/L) .................... 112

D-4 SPLP test results of the samples collected from west wall (mg/L) .................... 113

E-1 EPTOX test results of the samples collected from south wall (mg/L) ............... 114

F-1 MEP test results of the samples collected from south wall (extraction 1) (mg/L) ............................................................................................................... 115









G-1 Metal analysis data after batch test of PG with DI water of NW PG samples (mg/L) ............................................................................................................... 124

G-2 Metal analysis data after batch test of PG with DI water of SW PG samples (mg/L) ............................................................................................................... 125

G-3 Metal analysis data after batch test of PG with DI water of EW PG samples (mg/L) ............................................................................................................... 126

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G-4 Metal analysis data after batch test of PG with DI water of WW PG samples (mg/L) ............................................................................................................... 127

H-1 Batch leaching test with MSW leachate for PG samples collected from north wall (mg/L) ........................................................................................................ 128

H-2 Batch leaching test with MSW leachate for PG samples collected from south wall (mg/L) ........................................................................................................ 129

H-3 Batch leaching test with MSW leachate for PG samples collected from east wall (mg/L) ........................................................................................................ 130

H-4 Batch leaching test with MSW leachate for PG samples collected from west wall (mg/L) ........................................................................................................ 131

I-1 QA/QC for TCLP ............................................................................................... 132

I-2 QA/QC for SPLP ............................................................................................... 133

I-3 QA/QC for DI water batch leaching test ............................................................ 134

I-4 QA/QC for MSW batch leaching test ................................................................ 135

I-5 QA/QC for EPTOX ............................................................................................ 136

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LIST OF FIGURES

Figure page 4-1 Silver (Ag) and Arsenic (As) concentrations of PG samples in TCLP test .......... 48

4-2 Barium (Ba) and Cadmium (Cd) concentrations of PG samples in TCLP test .... 49

4-3 Chromium (Cr) and Lead (Pb) concentrations of PG samples in TCLP test ....... 50

4-4 Selenium (Se) concentration of PG samples in TCLP test ................................. 51

4-5 Silver (Ag) and Aluminum (Al) concentrations of PG samples in SPLP test ....... 52

4-6 Arsenic (As) and Boron (B) concentrations of PG samples in SPLP test ........... 53

4-7 Beryllium (Be) and Cadmium (Cd) concentrations of PG samples in SPLP test ...................................................................................................................... 54

4-8 Chromium (Cr) and Copper (Cu) concentrations of PG samples in SPLP test ... 55

4-9 Iron (Fe) and Potassium (K) concentrations of PG samples in SPLP test .......... 56

4-10 Sodium (Na) and Nickel (Ni) concentrations of PG samples in SPLP test .......... 57

4-11 Lead (Pb) and Antimony (Sb) concentrations of PG samples in SPLP test ........ 58

4-12 Tin (Sn) and Strontium (Sr) concentrations of PG samples in SPLP test ........... 59

4-13 Vanadium (V) and Zinc (Zn) concentrations of PG samples in SPLP test .......... 60

4-14 Toxicity Characteristic Leaching Procedure initial and final pH .......................... 61

4-15 Synthetic Precipitation Leaching Procedure initial and final pH .......................... 61

4-16 Aluminum (Al) and Barium (Ba) concentrations of PG samples (south wall) in EPTOX test......................................................................................................... 62

4-17 Calcium (Ca) and Chromium (Cr) concentrations of PG samples (south wall) in EPTOX test ..................................................................................................... 63

4-18 Copper (Cu) and Potassium (K) concentrations of PG samples (south wall) in EPTOX test......................................................................................................... 64

4-19 Magnesium (Mg) and Nickel (Ni) concentrations of PG samples (south wall) in EPTOX test ..................................................................................................... 65

4-20 Strontium (Sr) and Zinc (Zn) concentrations of PG samples (south wall) in EPTOX test......................................................................................................... 66

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4-21 Aluminum (Al) and Barium (Ba) leachability in US EPA’s MEP .......................... 67

4-22 Beryllium (Be) and Calcium (Ca) leachability in US EPA’s MEP ........................ 68

4-23 Chromium (Cr) and Copper (Cu) leachability in US EPA’s MEP ........................ 69

4-24 Potassium (K) and Magnesium (Mg) leachability in US EPA’s MEP .................. 70

4-25 Nickel (Ni) and Strontium (Sr) leachability in US EPA’s MEP ............................. 71

4-26 Zinc (Zn) leachability in US EPA’s MEP ............................................................. 72

4-27 Aluminum (Al) and Barium (Ba) concentrations in DI water batch leaching test ...................................................................................................................... 73

4-28 Calcium (Ca) and Copper (Cu) concentrations in DI water batch leaching test .. 74

4-29 Potassium (K) and Sodium (Na) concentrations in DI water batch leaching test ...................................................................................................................... 75

4-30 Nickel (Ni) and Strontium (Sr) concentrations in DI water batch leaching test .... 76

4-31 Zinc (Zn) concentration in DI water batch leaching test ...................................... 77

4-32 Aluminum (Al) and Arsenic (As) concentrations in MSW leachate batch leaching test ....................................................................................................... 78

4-33 Boron (B) and Barium (Ba) concentrations in MSW leachate batch leaching test ...................................................................................................................... 79

4-34 Calcium (Ca) and Cobalt (Co) concentrations in MSW leachate batch leaching test ....................................................................................................... 80

4-35 Chromium (Cr) and Copper (Cu) concentrations in MSW leachate batch leaching test ....................................................................................................... 81

4-36 Iron (Fe) and Potassium (K) concentrations in MSW leachate batch leaching test ...................................................................................................................... 82

4-37 Magnesium (Mg) and Manganese (Mn) concentrations in MSW leachate batch leaching test .............................................................................................. 83

4-38 Sodium (Na) and Nickel (Ni) concentrations in MSW leachate batch leaching test ...................................................................................................................... 84

4-39 Antimony (Sb) and Strontium (Sr) concentrations in MSW leachate batch leaching test ....................................................................................................... 85

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4-40 Vanadium (V) and Zinc (Zn) concentrations in MSW leachate batch leaching test ...................................................................................................................... 86

4-41 Sulfate concentration results of batch test with MSW leachate .......................... 87

4-42 TDS results of batch test with MSW leachate ..................................................... 87

5-1 Aluminum (Al) concentrations in different batch leaching tests .......................... 97

5-2 Barium (Ba) concentrations in different batch leaching tests .............................. 97

5-3 Chromium (Cr) concentrations in different batch leaching tests ......................... 98

5-4 Calcium (Ca) concentrations in different batch leaching tests ............................ 98

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LIST OF ABBREVIATIONS

ASTM American Society for Testing and Materials

CFS Cancer Slope Factors

DI Water Deionized Water

EPA Environmental Protection Agency

EPTOX Extraction Procedure Toxicity

EW East Wall

FIPR Florida Institute of Phosphate Research

GWCTL Groundwater Cleanup Target Level

ICP-AES Inductively Coupled Plasma Atomic Emission Spectrophotometer

L/S Ratio Liquid to Solid Ratio

LOAEL Lowest Observed Adverse Effect Level

MEP Multiple Extraction Procedure

MSW Municipal Solid Waste

NESHAP National Emissions Standards for Hazardous Air Pollutants

NOAEL No Observed Adverse Effect Level

PG Phosphogypsum

RCRA Resource Conservation and Recovery Act

RFD reference dose

SPLP Synthetic Precipitation Leaching Procedure

SW South Wall

TCLP Toxicity Characteristic Leaching Procedure

TDS Total Dissolved Solids

UCL95 95% Upper Confidence Limit

USGS United States Geological Survey

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WW West Wall

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the

Requirements for the Degree of Master of Engineering

TRACE METALS LEACHABILITY CHARACTERIZATION OF PHOSPHOGYPSUM

By

Shabnam Mostary

May 2011

Chair: Timothy G. Townsend Major: Environmental Engineering Sciences

Phosphogypsum (PG), a primary byproduct from phosphoric acid production, is

accumulated in large stockpiles and occupies vast areas of land. The aim of this study

was to characterize the trace metals leachability of phosphogypsum under different

environmental conditions. For this purpose multiple batch leaching tests were

conducted to observe the leaching behavior of PG elements. Based on the toxicity

characteristic leaching procedure (TCLP) and extraction procedure toxicity (EPTOX)

test, none of the metals (Ag, As, Ba, Cd, Cr, Pb, Se) exceeded the regulatory toxicity

limits; thus PG samples tested did not meet the definition of EP Toxicity under the

Resource Conservation and Recovery Act (RCRA). It is notable that mercury was not

tested in this study. Results from the TCLP, synthetic precipitation leaching procedure

(SPLP) and deionized water (DI) extraction, leached relatively similar concentrations of

inorganic constituents (except calcium). Aluminum and iron concentrations exceeded

their respective groundwater cleanup target level (GWCTL) in SPLP leachates. In the

multiple extraction procedure (MEP), most of the metals leached at greater

concentration in the second extraction than in the first. In a leaching test utilizing

municipal solid waste (MSW) leachate as the extraction fluid, a few constituents of PG

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such as calcium and sulfate considerably leached out. Calcium leached more in the

MSW leaching test than TCLP and SPLP. Aside from calcium and strontium there was

no significant leaching of other metals in the MSW leaching test. Though concentration

of arsenic (UCL95) was above GWCTL in total metal analysis, it was not detected in any

of the leaching test.

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CHAPTER 1 INTRODUCTION

1.1 Phosphogypsum and Its Management

Phosphogypsum (PG), a waste by-product from the wet manufacturing process of

phosphoric acid, is abundant in Florida due to the presence of this industry. The

composition of PG is variable and is related to the source of phosphate rock as well as

the manufacturing process. Gypsum (CaSO4.2H2O) is the main component; however,

PG also contains low concentrations of P and some of the impurities that were originally

in the phosphate rock (F, trace elements and naturally occurring radionuclides). Some

of the minor elements that are common, such as F, As, Cd, P, and S, have the potential

to pose environmental health concern if excessive levels are transported into ground or

surface waters. Thus, there are environmental concerns in regards to the potential

movement of fluoride, sulfate, certain trace elements, and radionuclides from the

phosphogypsum stacks into groundwater. PG is currently placed in large piles or

“stacks” to prevent it from entering the environment. Leachate from these “gyp stacks”,

as they are called, must be properly understood to minimize the risk of environmental

contamination.

Prior to 1989, PG was treated as any other item of commerce. The US

Environmental Protection Agency (EPA) first issued the National Emissions Standards

for Hazardous Air Pollutants (NESHAP) for phosphogypsum in 1989 (54 FR 51654,

December 15, 1989). The 1989 rule required that all phosphogypsum be stored in

stacks. EPA also prohibited all phosphogypsum research and uses, such as agricultural

or indoor research and development.

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In response to several petitions, EPA conducted risk assessments and revised the

standard to permit alternate uses of PG in 1992 (40 CFR Part 61, Subpart R). The 1992

revision permitted uses of PG for agricultural uses (as a conditioner for soils containing

high quantities of salt or low quantities of calcium and other nutrients), research and

development projects and other alternate uses that are approved by EPA on a case-by-

case basis.

In 1999 EPA increased the amount of phosphogypsum which may be used in

indoor laboratory research from 700 to 7,000 pounds per experiment, with no limit on

the number of experiments (40CFR 61.205). Under the 1999 rule, PG may be lawfully

removed from a stack and distributed in commerce for use in agriculture if the average

radium-226 concentration of the PG does not exceed 10 picocuries per gram

(pCi/g)(40CFR 61.204). The owner or operator of the stack from which the PG is

removed shall determine annually the average radium-226 concentration at the location

in the stack from which the PG will be removed. PG may not be lawfully removed from a

stack and distributed or used for any purpose other than agriculture and research

purposes without prior EPA approval (40CFR 61.204). This restriction on the maximum

radium radioactivity essentially eliminates the use of southern/central Florida

phosphogypsum because its radium-226 levels are commonly in the range of 20 to 35

pCi g-1 (Guidry 1990; May and Sweeney 1984a). The restriction does not impact

phosphogypsum from northern Florida or North Carolina, which generally have lower

levels of radium-226.

Considerable research has been conducted to evaluate the leachability of toxic

metals (As, Ba, Cd, Cr, Hg, Pb, Se and Ag) from phosphogypsum by TCLP and

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EPTOX. Several researchers have conducted leaching tests to estimate mobility of

trace metals, radionuclides and rare earth metals from PG using different leaching

solutions like distilled water, aqua regia, salt water etc.

1.2 Objectives

The primary objective of this thesis was to determine typical trace metal leaching

behavior of PG using standardized regulatory leaching tests for solid wastes. Leaching

tests play an important role in the reuse of raw waste materials as secondary materials.

Analyses such TCLP, SPLP, EPTOX, MEP that would typically be required for a

beneficial use demonstration in Florida were conducted. These analyses were

conducted to evaluate the leachability of trace metals (Ag, Al, As, B, Ba, Ca, Cd, Co, Cr,

Cu, Fe, K, Mn, Na, Ni, Pb, Sb, Se, Sn, Sr, V, Zn) in PG. Laboratory leaching tests which

generate leachate from waste have been used to evaluate leachability of hazardous

constituents (As, Ba, Cd, Cr, Pb, Se, Ag) from PG. The results (total and leachable

concentrations of inorganic constituents) were compared to Florida’s risk-based target

levels like soil cleanup target level (SCTL) and groundwater cleanup target level

(GWCTL). PG leachability using different solutions like MSW leachate and DI water was

also examined. Knowledge on leaching behavior of PG could help to explore disposal

options and assess the risk associated with beneficial-use options for PG.

This study investigates one particular phosphogypsum stack in an attempt to

characterize PG leachability that would be typical for many of the other stacks in central

Florida. Chapter 2 investigates the literature pertinent to PG production and leachate

resulting from PG and leaching tests. Chapter 3 discusses the materials and

methodology used in this research. Chapter 4 presents the results from various leaching

tests. Finally, discussions of the results are presented in Chapter 5.

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CHAPTER 2 LITERATURE REVIEW

2.1 Phosphoric Acid Production

Phosphogypsum is the primary byproduct generated from the wet-acid process for

producing phosphoric acid from phosphate rock. Phosphoric acid is an industrial raw

material required for the production of phosphate fertilizer. Phosphate rock, mined in

open pit mines, does not have a definite chemical composition and the composition

varies in different mining areas. Phosphate ore contains roughly one-third quartz sands,

one-third clay minerals, and one third phosphate particles (USEPA 1992). Impurities like

calcium, fluoride, chlorides, chromium, rare earths and radio nuclides are also common.

United States is the world’s leading producer and consumer of phosphate rock and

phosphate fertilizers (USGS 2002). Extensive deposits of phosphate rock are found in

Florida, Tennessee, North Carolina and Idaho. As a result of the low aqueous solubility

of calcium phosphate, the phosphate content of the rock is converted into phosphoric

acid to produce fertilizer. Phosphate ore composition partly determines the nature of the

phosphorus fertilizer and phosphogypsum. For every ton of phosphoric acid produced,

4.5-5.5 tons of phosphogypsum are produced (Saylak et al. 1988).

According to a mineral industry survey conducted by U.S. Geological Survey

(USGS) in 2007, a total of twelve phosphate rock producing mines were active

nationwide (Table 2-1). In Florida, phosphate rock is mined and processed by three

companies: CF Industries, Inc., The Mosaic Co., and PCS Phosphate Co., Inc. (USGS

2007).

Phosphate rock is usually treated by a physical process called beneficiation; a

process prior to acid treatment in order to concentrate the P content of the ore (Becker

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1989). Beneficiation often involves concentration by washing, screening and flotation.

Phosphoric acid is produced either by dry thermal or wet acid methods. The dry thermal

method produces elemental phosphorus using an electric arc furnace. Phosphoric acid

produced by dry thermal process is of a much higher purity and is used in the

manufacture of high grade chemicals, pharmaceuticals, detergents, food products,

beverages, and other non fertilizer products.

In the wet acid process, phosphate rock is treated with concentrated sulfuric acid

and water to produce gypsum (CaSO4.2H2O), phosphoric acid and hydrogen fluoride.

Wet process phosphoric acid is used in fertilizer production because it is more

economical. The following is a simplified chemical reaction to illustrate the process

(Luther et al. 1992).

Ca10(PO4)6F2 + 10H2SO4 + 20H2O →10CaSO4.2H20 + 6H3PO4 + 2HF

Once crystallized, the gypsum is separated from the acid by filtration, mixed with

water and transferred as slurry to onsite disposal areas referred to as phosphogypsum

stacks. The phosphogypsum stacks are an integral part of the overall wet process.

The phosphogypsum slurry is pumped to the top of the stack and discharged into

perimeter deposition ponds. The process water is decanted into a center storage pond

and then removed from the stack for recycle via a siphon. The phosphogypsum slurry

begins to form a small pond on top of the stack with the growth of stack. Workers

dredge gypsum from the pond to build up the dike around it and the pond gradually

becomes a reservoir for storing and supplying process water. As the wet process

requires large quantities of water, the water impounded on the stack is used as a

reservoir that supplies and balances the water needs of the process.

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2.2 Potential Uses of Phosphogypsum

EPA first banned any use of phosphogypsum in 1989. Since then it has been a

divisive issue on if and how to use phosphogypsum. As a local material,

phosphogypsum stacks can be found extensively in Florida. However, due to the 1992

EPA ban on the use of phosphogypsum, research has slowed dramatically. As a result,

special provisions must be made to FDEP and EPA before this material can be used

other than agricultural purposes.

It is of interest to the fertilizer industry to find effective and economical long-term

solutions for the management of PG; this would help to minimize space requirements

and the potential for environmental impact caused by the accumulation of PG stacks.

Several research projects have investigated practical application of PG for a

variety of purposes, including its use as road fill material (May 1983; Chang 1989; Lloyd

1985) and as a soil stabilizer (Degirmenci 2006). Several roads and parking lots were

constructed using PG or cement-PG. They are used daily in Florida and Texas with no

reported negative environmental impacts (Nifong and Harris 1993). Sulfur deficiencies

exist in soils of the southeastern US. Phosphogypsum soil amendment is a possible

solution to correct this deficiency because it provides a sulfur source that is slowly

available to the plants and is not easily leached out of the soil by rainfall (Lloyd 2004).

Stanley and Lloyd (1992) studied phosphogypsum, reporting that PG is currently

being wasted and that PG enriches the soil. Lloyd states that “PG has been proven to

be a suitable amendment for many soil types and is an excellent fertilizer source of

sulfur, calcium and phosphorous”. He argues that “Any soil that tends to surface-harden

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and resist water would benefit from PG. It creates a more porous texture that soaks up

rainfall”.

In the past, countries such as France and Japan used phosphogypsum for

construction of roadways and landfills and as a building material for houses. Research

has been conducted in France to use PG for embankment construction (Moussa et al.

1984). Their study showed that re-utilization of PG is possible in well-determined

conditions of placement and use.

Studies suggest that PG along with coal fly ash can be used as an amendment to

improve rice paddy soil fertility (Lee et al. 2009). It was concluded that the fly ash and

PG mixture could be a good source of inorganic soil amendments to restore the soil

nutrient balance in rice paddy soil.

Extensive research has been conducted to recover sulfur from PG. In general,

sulfate is converted to sulfur dioxide by a high temperature decomposition of calcium

sulfate in the PG. The sulfur dioxide is scrubbed from the gaseous emissions and sent

to the facility’s chemical plant where it is converted to sulfuric acid. This is then utilized

in the wet acid process (US EPA 1992). This method is not economical if the price of

sulfur is too low.

2.3 Leaching Tests in Solid Waste Management

Leaching is a method to remove soluble components from a solid matrix. Many

leaching test procedures have been developed to simulate the leaching processes of

wastes in landfills or other disposal scenarios; these assist in evaluating potential risks

to human health and environment from solid wastes. Therefore, leaching tests are often

used in the decision making process of solid waste management. Leaching tests are

used to estimate the potential concentration of contaminant that leaches from a solid

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waste when exposed to water or similar extraction solution. In general, there are two

types of leaching tests: batch leaching tests and dynamic column/lysimeter tests. Some

common batch leaching tests include Extraction Procedure Toxicity (EPTOX), Toxicity

Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure

(SPLP), American Society for Testing and Materials (ASTM) extraction test and Multiple

Extraction Procedure (MEP). While batch leaching tests are characterized by a constant

liquid to solid ratio, dynamic leaching tests are characterized by increasing liquid to solid

ratio as the experiment proceeds. Batch tests typically involve adding waste to an

extraction solution and then agitating the mixture for a short period of time (typically less

than 24 hour).Thus, batch tests offer a relatively rapid, cost effective method for the

assessment of metal leachability. Batch tests are primarily conducted as a regulatory

tool but they can also be conducted in a manner to examine a specific variable’s

influence on metal mobility, like impact of pH, liquid to solid ratio, etc.

2.3.1 Toxicity Characteristic Leaching Procedure (TCLP)

TCLP (EPA Method 1311) is the most frequently used batch test in the

management of solid waste. The TCLP was designed by the US Environmental

Protection Agency (EPA) to provide a relatively quick test to determine whether a solid

waste should be characterized as hazardous and thus be managed in a more controlled

manner. The TCLP attempts to mimic reducing, low pH environmental conditions in

MSW landfills. The extraction fluid (pH 4.93 ± 0.05) simulates a scenario where a

potentially hazardous waste is co-disposed with MSW. The primary extraction fluid is a

buffered acetic acid solution in a liquid to solid ratio of 20:1 for 18 ± 2 hours. Particle

size reduction is required if the particle is greater than 1 cm in its narrowest dimension.

The concentrations of contaminants are compared to toxicity characteristic (TC) limit

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concentrations outlined in 40CFR261.3 to determine hazardous waste designation. The

TC limits for the eight metals used in determination of hazardous waste are presented in

Table 2-2. Note that there are a number of organic contaminants which also carry a

toxicity characteristic limit. TCLP uses acetic acid (weak acid) which has a strong ability

to complex or chelate metals.

2.3.2 Synthetic Precipitation Leaching Procedure (SPLP)

The SPLP is an EPA SW-846 analytical method (EPA Method-1312) designed to mimic

the mobility of toxic contaminants when exposed to acidic rainfall. The SPLP is thus

used to evaluate the potential for metal leaching into ground and surface waters from

waste exposed to rainfall (Jang and Townsend 2001; Brantley and Townsend 1999).

The time and liquid-to-solid ratio are the same as in the TCLP, but SPLP utilizes an

extraction fluid intended to simulate precipitation or acid rain. Particle size reduction is

required if the particle is greater than 1 cm in its narrowest dimension The extraction

fluid (pH 4.2 ± 0.05) is made of two inorganic acids (nitric and sulfuric acid) to simulate

acidic rainwater.

2.3.3 The US EPA Multiple Extraction Procedure (MEP)

The MEP simulates leaching caused by the repetitive precipitation of acid rain

water (EPA Method 1320). MEP may be used to address long-term leachability. MEP is

designed to simulate the leaching that a waste will undergo from repetitive precipitation

of acid rain on an improperly designed sanitary landfill. The repetitive extractions will

give the highest concentration of each constituent that is likely to leach in a natural

environment. This test utilizes an initial acetic acid extraction (pH 5 ± 0.2) followed by

sequential extractions with simulated acid rain So, MEP combines aspects from both

the TCLP and the SPLP. Extraction on the first day calls for TCLP extraction fluid at a

26

liquid-to-solid ratio of 20:1; thereafter, the procedure calls for SPLP extraction solution

(pH 3 ± 0.2) (at least eight subsequent extractions) at the same liquid-to-solid ratio.

Details are discussed in Chapter 3.

2.4 Leaching Tests for Assessing the Potential for Groundwater Contamination

Leaching of pollutants to groundwater is a very complex process influenced by

several factors such as meteorological parameters (e.g., rainfall), soil properties

(particle size distribution, organic carbon content), and physical-chemical characteristics

(Kördel and Klein 2006).

Regulation of groundwater quality is generally under state jurisdiction; most states

have their own risk-based regulatory thresholds regarding contaminant transport from

soil to groundwater. The state of Florida has what are known as Soil and Groundwater

Cleanup target Levels (SCTL and GWCTL). The SCTLs consist of over 350 individual

chemicals with pre-calculated total constituent concentration thresholds based on-direct

human contact with soil and potential for soil contamination to migrate to groundwater.

Different limits reflect different possible groundwater uses. The worst case scenario is

where the water is assumed to be used for direct human consumption.

The GWCTLs are a similar list of maximum leachable concentrations for various

constituents. For particularly hazardous constituents, the US EPA primary and

secondary drinking water standards (Table 2-3) are generally used for the GWCTL.

SCTL were developed based on direct human contact (i.e., direct exposure), and based

on soil acting as a source of groundwater or surface water contamination (i.e.,

leachability). The US EPA has developed measurements of cancer potency of

carcinogens, which are termed cancer slope factors (CSFs). Risk-based soil cleanup

guidelines have been developed for both carcinogens and non carcinogens. For non-

27

cancer risks, the reference dose (RfD) is the term used to refer to the maximum

acceptable exposure. RfD’s are determined from Lowest Observed Adverse Effect

Level (LOAEL) or No Observed Adverse Effect Level (NOAEL) measurements that have

been multiplied by a series of uncertainty factors. There are separate RfDs for different

pathways of exposure (Oral, inhalation). For calculating SCTL, we need to consider

different pathways (ingestion, inhalation, dermal exposure). As for example, equation for

a cancer risk from soil exposure through ingestion will be, CTL (mg/Kg) = {Target

Cancer risk X Body weight (Kg)}/ {Oral Cancer Slope Factor (mg/kg-day)-1X ingestion

rate (mg/day)}.

The formula for calculating GWCTL (carcinogen) is, GWCTL (mg/L) = {Target

Cancer risk X Body weight (Kg)}/ {Oral cancer slope factor ((mg/kg-day)-1 X Average

Water Consumption Rate (L/day)}.

Body weight and water consumption are assumed for calculation. For non

carcinogen it will be only, GWCTL= {(RFDX Body Weight)/Water consumption rate}.

Since metals present in land-applied solid waste may leach from the waste and migrate

to the groundwater (Townsend et al. 2003), possible risk to ground water should be

assessed. In Florida and many other states, leaching risk is evaluated by conducting the

SPLP and comparing the results to the aforementioned risk-based groundwater

standards. This approach is typically viewed as being more representative because the

chemical nature of the waste, which can impact leaching, is tested.

2.5 Characteristics of Phosphogypsum

The chemical and mineralogical characteristics of phosphogypsum vary depending

upon the nature of the phosphate ore, the type of process used in fertilizer

manufacturing, the efficiency of plant operation, the age and location of the stockpile,

28

and any contaminants which may be introduced into the phosphogypsum at the

production plant (Arman and Seals 1990). Calcium and sulfate dominate the

composition of phosphogypsum because it is approximately >90% gypsum (Berish

1990). PG normally has a pH between 4.5 and 5.0. Acidity of PG is due to residual

phosphoric acid, sulfuric acid and fluoride acids contained within the pore spaces. May

and Sweeney (1984a) found the pH of extracts from Florida phosphogypsum to range

between 2.1 and 5.5. Metal concentrations in PG have been thoroughly characterized

and typical concentrations are summarized in Table 2-4. These elemental compositions

may vary greatly depending on the source of the phosphate rock.

2.6 Phosphogypsum Leaching Studies

The leaching behavior of materials depends on several parameters. These include

specific element solubility and availability or release potential. Again solubility can be

influenced by pH, complexation by inorganic species or dissolved organic matter, and

reducing properties (Kim 2002).

May and Sweeney (1984a) investigated nine PG stacks in Florida to study various

physical and chemical characteristics of PG. Results for this analysis showed that the

trace elements were uniformly distributed within the PG stacks. May and Sweeney

(1984b) evaluated the leachability of Ra and elements the EPA has classified as toxic

(As, Ba, Cd, Cr, Pb, Hg, Se, and Ag) by using the standard EPA 'EP' extraction

procedure (Federal Register 1980). The concentrations of toxic elements in the extract

were all below EPA maximal concentrations, therefore the material was considered non-

toxic by EPA standards. The authors estimated that the inclusion of Ra into the

phosphogypsum crystal structure would be 89% of the amount originally present,

indicating that very little Ra would be leached. They concluded that phosphogypsum

29

could not be classified as a hazardous waste because it was neither corrosive nor

caustic (pH was > 2 and < 12.5). In addition the average total elemental concentrations

of elements classified as toxic by the EPA were less than the EPA allowable toxic

elemental criteria for toxic hazardous waste (Federal Register 1980).

Rusch and Seals (2004) conducted TCLP on raw PG and oven dried PG samples

(oven-dried at 45oC for 12 hours and ground to pass through a US Standard sieve

No.10.) collected from Louisiana. The metal concentrations in the leachate from both

type, were also well below the US EPA toxicity characteristics limits. Also, there was no

significant difference between these two types of samples.

Kendron (1996) conducted EPTOX and TCLP on raw PG specimens to

understand the leaching behavior of As, Ba, Cd, Cr, Pb, Ag, Hg and Se through

phosphogypsum. The results indicated a potential leaching of these species. Although,

the leachate concentration levels were below the US EPA toxicity limits, the

concentrations failed to meet the US EPA drinking water limits for several species.

To determine the potential environmental impact of phosphogypsum, Naff (1984)

conducted EPTOX on phosphogypsum. The results were within the permissible EPA

limits for toxicity; however SO42- and fluoride levels exceeded drinking water standards.

Haridasan (2002), conducted leaching studies on PG samples (Kochi, India) using

distilled water (pH 6.0) and rainwater (pH= 5.0–5.8) as leachants. They varied contact

time and solid/liquid ratio in the leaching procedures. The laboratory results indicated

that rainwater leached less 226Ra than distilled water.

The leachability of Cd, Cu, U and Zn in Syrian PG was studied by Al-Masri et al.

(2004). They did leaching test of PG with distilled water and concluded that Cu and Cd

30

are easily transferrable to water or surrounding environment. They also grouped PG into

six different particle sizes to observe the effect of particle size on leachability and found

that fine particles (45–75 mm) yielded a relatively high solubility.

31

Table 2-1. Active phosphate rock mines in the United States in 2007 (USGS 2007)

Owner Mine State

CF Industries, Inc. South Pasture Florida Mosaic Co, The Four Corners Florida Do Hookers Prairie Florida Do Hopewell Florida Do South Fort Meade Florida Do Wingate Creek Florida Nu-West Industries, Inc. (Agrium Inc.) Dry Valley Idaho P4 Production, LLC. (Monsanto Co.) South Rasmussen Idaho PCS Phosphate Co., Inc. Aurora North Carolina Do Swift Creek Florida Simplot, J.R., Co. Smoky Canyon Idaho Do Vernal Utah

Table 2-2. RCRA toxicity characteristics limits (metals only)

Metal RCRA TC Limit (mg/L)

As 5.0 Ba 100 Cd 1.0 Cr 5.0 Hg 0.2 Se 1.0 Ag 5.0 Pb 5.0

Table 2-3. US EPA drinking water standards

Primary Secondary

Contaminant Standard (mg/L) Contaminant Standard (mg/L)

As 0.01 Al 0.2

Ba 2.0 Cu 1.0

Be 0.004 Fe 0.3

Cd 0.005 Mn 0.05

Cr 0.1 Zn 5

Cu 1.3 Cl- 250

Pb 0.015 SO42- 250

Sb 0.006 TDS 500

Se 0.05

Tl 0.002

32

Table 2-4. Content of some trace elements in Phosphogypsum (PG) produced from different rock phosphate sources; also included are typical literature values for soil

Element Florida Source PGa

Idaho Source PGb

South African

Source PGc

Tunisian Source PGd

Typical soile

mg/Kg

Ag <1 1-11 0.05 As 40 <1-2 7.2

Au (g/kg) 3-15

B 3 <10-30 33 Ba 7 20-140 140 580 Be 1 1-2 0.92 Br 1-2 0.85 Cd 7 9-28 40 0.35 Cl <100-300 100 Co 2 <1 8 9.1 Cr <10-70 54 Cu 8 10-42 103 6 25

Hg (g/kg) <50 14000 90

Mn 15 <2-10 550 Mo 16 <1-2 5 0.97 Ni 2 3-15 15 19 Pb 1 3-7 13 19 Rb <10-20 67 Sb 100 0.3-0.8 0.66 Se 4-67 0.39 Sr 10 610-670 240 Th <1 9.4 U 6-13 2.7 V 19 10-40 80 Y 2 100-120 50 25 Zn 9 18-112 6 315 60 Zr 10 <10-110 185 230 aMay and Sweeney (1984a) bLuther and Dudas (1993) cMalan (1988) dRouis and Bensalah (1990) eSposito (1989)

33

CHAPTER 3 METHODS AND MATERIALS

3.1 Overview

To assess the leachability of various trace metals from phosphogypsum (PG),

samples were extensively analyzed with respect to composition and leaching behavior.

Inorganic element concentration from acid digestion and leaching samples were

analyzed using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-

AES).This section will describe the preparation of the samples and methods that were

followed to carry out the leaching tests.

3.2 Sample Collection and Processing

PG was sampled from the top of a PG stack located in Mulberry, Florida. Samples

were collected from four locations: the north, south, east, and west walls of the top

stack. Samples were retrieved from depths of 1 to 2 feet from the top of the stack. PG

samples were named north wall (NW), south wall (SW), east wall (EW) and west wall

(WW) based on their locations. PG samples were collected by using cleaned scoops,

trowels, shovels, and were placed in five-gallon buckets (HDPE) then sealed with lids.

PG samples were then transported to the UF laboratory. A total of 330 kg of PG was

collected from each of the four sampling locations. In the lab, samples collected from

different locations were not mixed together. But samples collected from different depths

for each location were thoroughly mixed to get a homogenous sample for that location

Samples were stored in closed containers in the lab at room temperature. To perform

research on PG, the requirements of 40 CFR 61.205 were followed; all PG was

accompanied by certification documents that conformed to the requirements of 40 CFR

61.208. The total quantity of PG at a facility did not exceed 7000 lbs. Containers of PG

34

were labeled with the following warning: “Caution: Phosphogypsum Contains Elevated

Levels of Naturally Occurring Radioactivity”.

3.3 Leaching Procedures

Four regulatory-based leaching tests were performed-TCLP, SPLP, EPTOX, and

MEP. The TCLP, SPLP, EPTOX, and MEP were developed by the US Environmental

Protection Agency (EPA). In addition, several experiments were conducted in a similar

fashion as TCLP but substituting actual landfill leachates and DI water as the leaching

solution.

3.3.1 Toxicity Characteristic Leaching Procedure

The TCLP method is defined in EPA Method 1311.TCLP uses one of two different

extraction fluids, depending on the alkalinity of the waste. Extraction fluid 1 is prepared

by diluting a mixture of 11.4 mL acetic acid (CH3COOH) and 128.6 mL of 1N sodium

hydroxide (NaOH) to 2L deionized water (DI). The resulting solution pH is 4.93 ± 0.05.

Extraction fluid 2 is used for highly alkaline materials. This solution is prepared by

adding 11.4 mL acetic acid to 2L deionized water. pH of this solution should be

2.8±0.05. Because the pH of the PG sample was less than 5, extraction fluid 1 was

used. The TCLP requires that samples first be size-reduced to less than 0.95 cm in any

dimension. One hundred grams of the size-reduced samples were placed in a 2.2-L

TCLP extraction vessel, and 2.00 L of the extraction solution were added. The slurry

was mixed on a rotary extractor for 18 ± 2 hr at 30 ± 2 revolutions per minute and then

filtered through a 0.7 μm glass fiber filter. The filtrate was collected in 500 mL plastic

bottles (HDPE) and preserved by adjusting the pH to less than 2 using nitric acid. The

leachates generated by the TCLP process were acid digested and analyzed using ICP-

AES.

35

3.3.2 Synthetic Precipitation Leaching Procedure

SPLP leachates were prepared according to the procedure outlined in EPA

method 1312. A concentrated SPLP solution was prepared by adding 100 mL of one

percent (by volume) solution of concentrated nitric acid and 100 mL of one percent

solution of concentrated sulfuric acid, and then combining these in a 2 parts nitric to 3

parts sulfuric ratio (40%:60%). Then, 0.4 - 0.5 mL of concentrated SPLP solution was

added to reagent water in a 2-L volumetric flask and diluted to 2-L. The resulting SPLP

solution pH was required to be 4.20 ± 0.05. The SPLP requires that samples first be

size-reduced to less than 0.95 cm. One hundred grams of the size-reduced samples

were placed in a 2.2-L SPLP extraction vessel, and 2 L of the SPLP solution were

added. The slurry was mixed on a rotary extractor for 18 ± 2 h. After the extraction

procedures, separation of the leachate solution from PG was completed using a

vacuum filtration set-up. The filter used was a 0.7 μm acid-washed glass fiber filter .The

rotary extractor was used during the TCLP and SPLP tests was designed to rotate eight

2-L bottles in an end-over-end fashion. When loaded with a full load, each extractor

rotates at 30 rpm as required by the TCLP and SPLP procedures. The filtrate was

collected in 500-mL plastic bottles and preserved by adjusting the pH to less than 2

using nitric acid.

3.3.3 Extraction Procedure (EP) Toxicity Test Method

The method is defined in EPA Method 1310b.This test requires the continual

addition of acid to maintain a constant extraction pH. For the EPTOX, 100 g of sample

were placed in 1.6 L of deionized water and agitated for 24 hours. The method requires

that the pH of the mixture be maintained at 5 ± 0.2 by adding 0.5N acetic acid. The PG

samples in this study did not require any further acid addition. After 24 h of extraction,

36

deionized water was added to bring the total volume of the extraction fluid to 2 L. The

leachate was filtered using 0.45-μm filter.

3.3.4 Multiple Extraction Procedure

This test utilizes an initial acetic acid extraction followed by sequential extractions

with simulated acid rain. The initial extraction fluid is the same as the EPTOX. The

simulated rainfall extraction solution is similar to the SPLP leaching fluid but with a pH of

3.0 ± 0.2. This synthetic acid rain extraction fluid was prepared by adding 60% sulfuric

acid and 40% nitric acid (weight percent) to distilled deionized water until the pH is 3.0 ±

0.2. The residual solids after the extraction were re extracted nine times consecutively

using synthetic acid rain extraction fluid. An initial sample size of 12.5 g was used. Each

extraction step is performed at an L/S ratio of 20:1 for 24 h. After each filtration, both the

filter and the sample were added to the next extraction vessel. The final pH values of

leachates and metal ion concentrations were determined for each extraction.

3.3.5 Batch Leaching Test with MSW Leachate

This batch leaching test mimicked the condition that MSW landfill leachate directly

contacts PG and measured any constituent change before and after mixing MSW

leachate with PG. This test method is similar to the TCLP or SPLP test except that it

uses MSW landfill leachate as the extract solution. A 100 g sample of PG was mixed

with 2 L of MSW leachate and mixed for 18 ± 2 hours using a rotating shaker at 30 rpm.

The mixture of MSW landfill leachate and PG was filtered using 0.7 μm glass fiber filter

after the rotation. Inorganics were analyzed after acid digestion. For this test, MSW

landfill leachate was obtained from Polk County North Central landfill. The pH of

leachate was 7.6 and totals dissolved solids (TDS) was 6300 mg/L.

37

3.3.5.1 Sulfate analysis

Sulfate concentration in leachate samples from batch leaching test of PG (with

MSW leachate) was determined using a spectrophotometer (DR/4000 UV-VIS, HACH,

Loveland, CO) with HACH Method 8051. A sample cell was filled with 25 mL of sample.

One SulfaVer® 4 reagent powder was added to the cell. Sulfate ions in the sample react

with barium in the SulfaVer® 4 and form a precipitate of barium sulfate. The amount of

turbidity formed is proportional to the sulfate concentration.

3.3.5.2 Total dissolved solids (TDS)

Total dissolved solids (TDS) of the leaching solution from the batch leaching test

with MSW leachate was determined following EPA method 160.1. For this, aluminum

weighing dishes were placed in an 180oC drying oven one day before the test.

Desiccators were used to cool the dishes. Pre-dried dishes were weighed. A total of 100

mL sample was filtered using vacuum filtration. Filtrates were placed into an oven at

95oC for 18 hours to allow the samples to evaporate to dryness. After 18 hours,

temperature was increased to 180oC and continued at least for another 4 hours. The

dishes are removed from the oven and placed in the desiccators to cool for 30 minutes.

Then the dishes were returned to the 180oC oven for 1-2 hours and weighed. This

drying and weighing cycle was repeated until the last two weighings differ by less than

0.5 mg. Dishes were then placed in the desiccators to cool for at least one hour. Then

the dish containing the oven-dried sample was weighed to the nearest 0.1 mg. TDS was

determined using Equation 3-1.

(

)

(3-1)

38

3.3.6 Batch Leaching Test with DI Water

This test is similar to TCLP/SPLP except DI water was used as the leaching

solution. For this batch test 100 grams of PG was mixed with 2 L of DI water in a 2.2 L

glass jar. The mixture was agitated using a rotator for 16 to 20 hrs. After tumbling, the

slurry was filtered to separate PG leachate from the slurry. Then samples of this PG

leachate was retained for the chemical analysis.

3.4 Total Metal Analysis

Samples were digested to prepare them for trace metal analysis. The leaching test

samples from various batch tests were digested according to US EPA Method 3010. To

determine total metal concentration of PG, samples were digested according to the US

EPA 3050B. Digestion procedure was used to prepare aqueous leachate samples that

may contain insoluble colloidal particles for analysis by Inductively Coupled Plasma

Atomic Emission Spectrophotometer (ICP-AES). Leached and digested samples were

analyzed using ICP-AES as per US EPA SW846 method 6010B.

For digestion of aqueous samples nitric acid is added to a specified volume (50

mL) to the sample. The sample is refluxed with additional portion of nitric acid until the

digestate is clear or the color is stable. When the digestate reduced to a low volume, it

is then finally refluxed with hydrochloric acid and brought up to volume. The digested

sample is than analyzed by ICP-AES.

For digestion of solid PG, 1 gram (dry weight) sample was digested with repeated

additions of nitric acid (HNO3) and hydrogen peroxide (H2O2). For ICP-AES analyses,

hydrochloric acid (HCl) is added to the final digestate and the sample is refluxed.

39

3.5 pH of Phosphogypsum

The pH values of PG samples were determined by EPA method 9045D. For this,

20 grams of PG was mixed with 20 mL of reagent water and stirred continuously for 5

min. Then it was allowed to stand for 1 hour. After that, pH was measured.

3.6 Quality Assurance and Quality Control

All sampling equipment and containers were cleaned and prepared according to

the US EPA established standards. In the laboratory, analysis blanks, duplicates and

calibration check samples were analyzed as appropriate. For total metal analysis every

digestion event included (approximately 20 samples) a blank sample, a duplicate

sample, a triplicate sample, a matrix spike, a matrix spike duplicate for digestion. All

regulatory batch leaching test were conducted in triplicate. However for digestion, a

blank, duplicate sample, a sample spike and a sample spike duplicate were included.

40

CHAPTER 4 RESULTS

4.1 Total Metal Analysis Results

The chemical composition, which was determined using the US EPA Method

3051b, of the PG samples from each location is shown in Table 4-1. Samples were

analyzed for 23 metals (silver, aluminum, arsenic, boron, barium, beryllium, calcium,

cadmium, cobalt, chromium, copper, iron, potassium, magnesium, manganese sodium,

nickel, lead, antimony, selenium, tin, vanadium and zinc.). Calcium was the most

abundant metal detected in PG and ranges from 113,220 (± 58,100) to 171,200 (±

25,900) mg/kg. The minor constituents of raw PG were Al, Fe and K which each had a

concentration that exceeded 100.0 mg/kg. Trace elements, such as As, B, Ba, Cr, Cu,

Mn, Pb , Sn, V and Zn were also present. Ag, Cd, Co, Mg, Mo, Na, Ni, Sb and Se were

not detectable in the samples that were tested. For PG metal analysis, triplicate

samples from each location were analyzed. Of the RCRA TC limit metals, barium had

the highest concentration (38.6 mg/Kg). Concentrations of other toxic metals (As, Cr,

Pb) were below 3 mg/Kg. To use PG beneficially, to where direct human contact with

the PG is possible, comparison with risk based standards is needed. Although risk

assessment through direct exposure is not the focus of this research, it is discussed

briefly as it would certainly need to be considered as part of any beneficial use

application. Table 4-3 compares the concentration for each metal with its respective

Florida’s risk based soil cleanup target level. Florida’s SCTLs examine direct exposure

in two scenarios, residential and industrial settings. Of the metals detected in PG, the

95% Upper Confidence Limit (UCL95) of only one metal (arsenic) was slightly above its

SCTL for residential exposure but below the industrial limit. UCL95 was calculated using

41

samples from all four locations. In Table 4-1, the average concentrations with standard

deviations for each PG sample are presented. Detailed total analysis results are given

in Appendix B.

4.2 pH of Phosphogypsum

The pH of PG samples used in this study was in the range of 4.5-4.8 (Table 4-2).

One PG sample from each location was tested for pH. The pH of DI water used for this

experiment was 6.3. Though PG is composed primarily of the slightly soluble neutral

salt, calcium sulfate dihydrate, the acidity may be due to residual phosphoric and

sulfuric acids plus hydrofluoric and fluosilicic acids (Smith and Wrench 1984).

4.3 Toxicity Characteristic Leaching Procedure (TCLP)

US EPA specifies toxicity characteristic limits based on the metal concentrations in

the TCLP leachates. If any listed compound (mentioned in Chapter 2) exceeds the level

specified, the original waste is considered hazardous. The TCLP leachates for raw PG

were analyzed for trace metals that are on EPA’s list of toxicity characteristic elements

such as silver, arsenic, barium, cadmium, chromium, lead and selenium. Mercury was

not tested in this study. The TCLP was performed on 12 samples (triplicate samples for

each of the 4 locations). All the metal concentrations in the TCLP leachate analyzed for

each location were well below the respective regulatory levels. TCLP test data are

presented in Figures 4-1 through 4-4. Samples whose concentrations are below

detection limits are presented in the plots on the MDL (method detection limit) line. In

general, barium leached at higher concentrations than chromium. The mean barium

concentration of all 12 samples was 0.11 mg/L (0.07–0.16 mg/L).

42

4.4 Synthetic Precipitation Leaching Procedure (SPLP)

The average concentrations (from the four samples; each sample was measured

in triplicate) of 21 inorganic elements in the extraction fluids from SPLP test were

determined. Eleven of them were detected at concentrations above their respective

detection limit. As, B, Be, Cd, Co, Pb, Sb, Sn, Sr, V were not detected in SPLP.SPLP

results were compared with Groundwater Cleanup Target Levels (GWCTL). Most of the

metals were well below GWCTL except for aluminum and iron. Aluminum concentration

is greater than the GWCTL for all the samples. Iron concentration is greater than

GWCTL for six samples out of twelve. Even though aluminum and iron are the

secondary standards, these results may be questioned by a regulatory agency when

PG is considered for use in land application. SPLP results are presented in Figures 4-5

through 4-13 and detailed data are given in Appendix C.

Figures 4-14 and 4-15 show the initial and final pH’s for the TCLP test and SPLP

test, respectively. The final pH in the SPLP test was consistently lower than the TCLP

test in terms of final pH. Figure 4-15, which shows the initial and final pH’s in the SPLP

tests, shows that the final pH’s are generally consistent regardless of the location of the

sample.

4.5 Extraction Procedure Toxicity

EPTOX was conducted on PG samples of one location (SW) in triplicate and of the

22 metals analyzed aluminum, barium, calcium, chromium, copper, iron, potassium,

magnesium, nickel, strontium and zinc were detected. Final pHs of extraction fluids

were greater than SPLP but close to TCLP test (Table 4-4). The TCLP extracted slightly

higher concentrations of all the metals than EPTOX except copper, nickel and zinc.

Both tests use acetic acid as leaching solution but they have different pH. EPTOX

43

results are presented in Figures 4-16 through 4-20 and detailed data are given in

Appendix E.

4.6 USEPA Multiple Extraction Procedure

The MEP is used to assess long-term leachability of waste by combining aspects

from both the TCLP and the SPLP. The method requires sequential extraction of the

same waste. With each subsequent extraction, it is usually expected that leaching

concentrations will be decreased with time as there are less contaminants available for

leaching. As samples from all the locations showed similar leaching concentrations, the

MEP was conducted on samples from only one location (SW) in triplicate. Of the 21

metals analyzed only aluminum, barium, beryllium calcium, chromium, copper,

potassium, magnesium, nickel, strontium and zinc were detected above their respective

detection limit. The barium, copper, magnesium and potassium results are typical of

most sequential leaching tests, with the concentrations decreasing with consecutive

extractions. However, for other detected metals, an increase in concentration is

observed in the second extraction compared to the first extraction. This may be due to

the change in pH (Table 4-5). After the initial increase the metal concentration stabilized

and began to decrease with subsequent extractions. Results are presented in Figures

4-21 through 4-26.

4.7 Additional Leaching Testing

4.7.1 The Deionized Water Batch Leaching Test

Batch leaching test with DI water was conducted on samples of all four locations in

duplicate (Figures 4-27 through 4-31, Table 4-6). Calcium, which was predominant,

leached more in DI leachate than SPLP. Average calcium concentration in SPLP

leachate is 656 mg/L and 808 mg/L in DI water leachate. Of the 22 metals analyzed

44

only aluminum, barium, calcium, copper, potassium, molybdenum, sodium, nickel,

strontium and zinc were detected above their respective detection limit. Iron, which was

detected both in SPLP and TCLP test, was below its detection limit when leached with

DI water. Barium concentration was also higher in both TCLP and SPLP than DI water

leaching test. Again, copper concentrations leached by DI water were higher than both

SPLP and TCLP. Other than these metals, when PG samples were leached with DI

water; extracted concentrations were somewhat similar to the SPLP.

4.7.2 Batch Leaching Test with MSW Leachate

Figures 4-32 through 4-40 present the results of the leaching tests where MSW

leachates were used as the extraction fluids. Table 4-7 presents the result of the final

pH of MSW leaching solutions. This leaching test was carried out on samples of all four

locations in triplicate. Samples were analyzed for 22 metals. Only antimony, copper,

selenium and tin were below their respective detection limit. Concentrations of most

cations in the MSW leaching solution were similar to those in the MSW leachate except

calcium, iron and strontium. While iron concentration decreased after contacting with

leachate, strontium concentration increased. Calcium concentrations in MSW leaching

solution were up to one order of magnitude greater than those in the MSW leachate.

Concentrations of sulfate and TDS in the MSW leachate were compared to those in the

original MSW leaching solutions (Figure 4-41 and 4-42). Sulfate concentrations in the

leachate ranged from 3,000-3,250 mg/L. These sulfate concentrations are 15 times

greater than those in original MSW leachate. TDS measured in the leaching solutions

ranged from 9,350-9,500 mg/L. TDS concentration in the original MSW leachate was

about 6,300 mg/L.

45

Table 4-1. Metal concentrations (mg/kg) of PG samples

Element Detected

Sample ID Mean ± SD (mg/Kg)

NW SW EW WW

Ag BDLa BDL BDL BDL Al 875±77b 738±56 625±56 785±55 As 1.9±0.9 1.9±0.7 2.1±1.0 1.7±0.9 B 60±18 57±10 22±2.1 55±16 Ba 48.0±6.4 30.8±2.0 33.4±7.2 42.2±6.6 Be BDL BDL BDL BDL Ca

171,200 ±25,900

138,300 ±13,100

147,600 ±36,500

113,200 ±58,100

Cd BDL BDL BDL BDL Co BDL BDL BDL BDL Cr 1.9±0.4 1.6±0.3 1.5±0.5 1.3±0.5 Cu 2.0±0.8 1.9±0.7 1.9±0.6 1.9±0.5 Fe 903±65 932±130 615±133 717±94 K 126±24 187±31 140±5 175±29 Mg BDL BDL BDL BDL Mn 2.0±0.1 4.2±0.4 2.8±0.7 1.7±0.6 Mo BDL BDL BDL BDL Na BDL BDL BDL BDL Ni BDL BDL BDL BDL Pb 3.1±0.6 3.5±0.9 2.8±0.4 2.7±0.6 Sb BDL BDL BDL BDL Se BDL BDL BDL BDL Sn 6.3±0.8 3.8±1.1 4.0±1.0 3.9±0.4 V 1.6±0.6 2.3±0.6 1.2±0.1 1.3±0.3 Zn 4.2±0.9 4.7±0.8 3.1±0.5 5.3±0.9

aBDL = Below detection limit (detection limits are presented in Appendix A) barithmetic mean ± standard deviation of three replicates Table 4-2. pH of PG samples

Sample Location pH

North Wall 4.5 South Wall 4.7 East Wall 4.7 West Wall 4.8

46

Table 4-3. Total metal comparison with risk based standards for direct exposure

Metal

Mean Concentration ± SD (mg/Kg)

UCL95 (mg/Kg)

Florida SCTL

Residential (mg/Kg)

Industrial (mg/Kg)

Al 756108a 817 80000 NA

As 1.90.8 2.37 2.1 12

B 48.519.8 59.7 17000 430000

Ba 38.68.8 43.6 120 130000

Ca 14259029550 159296 NA NA

Cr 1.60.4 1.82 210 470

Cu 1.90.6 2.28 150 89000

Fe 792166 886 53000 NA

K 15733.4 176 NA NA

Mn 2.71.1 3.31 3500 43000

Pb 3.00.7 3.4 400 1400

Sn 4.51.3 5.26 47000 880000

V 1.60.6 1.93 67 10000

Zn 4.31.1 4.95 26000 630000 aarithmetic mean ± standard deviation of all (12) samples Table 4-4. pH results (Extraction Procedure Toxicity Test)

Sample ID pH

SW 1 4.71 SW 2 4.69 SW 3 4.72 DI Water 7.20

Table 4-5. pH results (Multiple Extraction Procedure Test)

Extraction Number pH

1 4.71 2 3.39 3 3.44 4 3.40 5 3.26 6 3.34 7 3.34 8 3.30 9 3.15

47

Table 4-6. pH results (Batch leaching test with DI water)

Sample ID pH

North Wall (NW) 4.53 South Wall (SW) 4.72 East Wall (EW) 4.92 West Wall (WW) 4.78 DI Water 7.4

Table 4-7. pH results (Batch leaching test with MSW leachate)

Sample ID pH

North Wall (NW) 7.40 South Wall (SW) 7.40 East Wall (EW) 7.60 West Wall (WW) 7.60 MSW Leachate 7.70

48

Figure 4-1. Silver (Ag) and Arsenic (As) concentrations of PG samples in TCLP test

49

Figure 4-2. Barium (Ba) and Cadmium (Cd) concentrations of PG samples in TCLP test

50

Figure 4-3. Chromium (Cr) and Lead (Pb) concentrations of PG samples in TCLP test

51

Figure 4-4. Selenium (Se) concentration of PG samples in TCLP test

52

Figure 4-5. Silver (Ag) and Aluminum (Al) concentrations of PG samples in SPLP test

53

Figure 4-6. Arsenic (As) and Boron (B) concentrations of PG samples in SPLP test

54

Figure 4-7. Beryllium (Be) and Cadmium (Cd) concentrations of PG samples in SPLP test

55

Figure 4-8. Chromium (Cr) and Copper (Cu) concentrations of PG samples in SPLP test

56

Figure 4-9. Iron (Fe) and Potassium (K) concentrations of PG samples in SPLP test

57

Figure 4-10. Sodium (Na) and Nickel (Ni) concentrations of PG samples in SPLP test

58

Figure 4-11. Lead (Pb) and Antimony (Sb) concentrations of PG samples in SPLP test

59

Figure 4-12. Tin (Sn) and Strontium (Sr) concentrations of PG samples in SPLP test

60

Figure 4-13. Vanadium (V) and Zinc (Zn) concentrations of PG samples in SPLP test

61

Figure 4-14. Toxicity Characteristic Leaching Procedure initial and final pH

Figure 4-15. Synthetic Precipitation Leaching Procedure initial and final pH

4.6

4.7

4.8

4.9

5

NWSW

EWWW

pH

Sample Location

Final

Initial

3.8

4

4.2

4.4

4.6

4.8

NWSW

EWWW

pH

Sample Location

Initial

Final

62

Figure 4-16. Aluminum (Al) and Barium (Ba) concentrations of PG samples (south wall) in EPTOX test

63

Figure 4-17. Calcium (Ca) and Chromium (Cr) concentrations of PG samples (south wall) in EPTOX test

64

Figure 4-18. Copper (Cu) and Potassium (K) concentrations of PG samples (south wall) in EPTOX test

65

Figure 4-19. Magnesium (Mg) and Nickel (Ni) concentrations of PG samples (south wall) in EPTOX test

66

Figure 4-20. Strontium (Sr) and Zinc (Zn) concentrations of PG samples (south wall) in EPTOX test

67

Figure 4-21. Aluminum (Al) and Barium (Ba) leachability in US EPA’s MEP

68

Figure 4-22. Beryllium (Be) and Calcium (Ca) leachability in US EPA’s MEP

69

Figure 4-23. Chromium (Cr) and Copper (Cu) leachability in US EPA’s MEP

70

Figure 4-24. Potassium (K) and Magnesium (Mg) leachability in US EPA’s MEP

71

Figure 4-25. Nickel (Ni) and Strontium (Sr) leachability in US EPA’s MEP

72

Figure 4-26. Zinc (Zn) leachability in US EPA’s MEP

73

Figure 4-27. Aluminum (Al) and Barium (Ba) concentrations in DI water batch leaching test

74

Figure 4-28. Calcium (Ca) and Copper (Cu) concentrations in DI water batch leaching test

75

Figure 4-29. Potassium (K) and Sodium (Na) concentrations in DI water batch leaching

test

76

Figure 4-30. Nickel (Ni) and Strontium (Sr) concentrations in DI water batch leaching test

77

Figure 4-31. Zinc (Zn) concentration in DI water batch leaching test

78

Figure 4-32. Aluminum (Al) and Arsenic (As) concentrations in MSW leachate batch

leaching test

79

Figure 4-33. Boron (B) and Barium (Ba) concentrations in MSW leachate batch

leaching test

80

Figure 4-34. Calcium (Ca) and Cobalt (Co) concentrations in MSW leachate batch

leaching test

81

Figure 4-35. Chromium (Cr) and Copper (Cu) concentrations in MSW leachate batch

leaching test

82

Figure 4-36. Iron (Fe) and Potassium (K) concentrations in MSW leachate batch

leaching test

83

Figure 4-37. Magnesium (Mg) and Manganese (Mn) concentrations in MSW leachate

batch leaching test

84

Figure 4-38. Sodium (Na) and Nickel (Ni) concentrations in MSW leachate batch

leaching test

85

Figure 4-39. Antimony (Sb) and Strontium (Sr) concentrations in MSW leachate batch

leaching test

86

Figure 4-40. Vanadium (V) and Zinc (Zn) concentrations in MSW leachate batch

leaching test

87

Figure 4-41. Sulfate concentration results of batch test with MSW leachate

Figure 4-42. TDS results of batch test with MSW leachate

88

CHAPTER 5 DISCUSSION

5.1 Comparison to Previous Studies

TCLP results found in the previous studies are presented in Table 5-1. In the

present study only barium and chromium were detected above detection limits in TCLP,

and both were below their respective TC limits. Concentrations of these toxic metals

were found below their TC limits in previous studies as well. Mercury was not analyzed

in this study; Kendron (1996) reported mercury concentration in TCLP leaching solution

from PG below its toxicity limit.

Al Masri et al. (2004) conducted leaching of PG (Syrian) using DI water as a first

step of sequential leaching test. In their study they used 1 g PG and 100ml DI water for

leaching (L/S ratio of 100:1). The results of the current DI water leaching test are

compared with the results obtained in the 2004 study for Cd, Zn and U in Table 5-

2.Though Cd was not detected in this study, Zn was leached at a much higher

concentration than the previous study. This may be due to the high L/S ratio (20:1) used

for this study. The bioavailability and mobility of trace metals (As, Cd, Cr, Cu, U, Zn)

were estimated by Al-Hwaiti et al. (2010) using aqua regia leaching solution. Results are

presented in Table 5-3.They used 50 mg of dried PG and 5 ml of nitric acid and

hydrochloric acid (aqua regia) and rotated for 48 hours. All the metals tested leached

below 10% (fraction leached) but the concentrations of all the metals were above

detection limits. In comparison to that study, SPLP performed in this study leached a

higher percentage of Cr, Cu and Zn.

Metal concentrations of PG is compared with gypsum wallboard in Table 5-4

Relative to gypsum wallboard, PG was elevated in total content of Al, As, Ba and K.

89

5.2 Discussion of Leaching Results

Arsenic was detected above SCTL in total metal analysis. But it was not detected

in any of the leaching tests. When metal concentrations extracted by the SPLP are

compared to those of the TCLP, calcium was leached to a greater extent in the TCLP

than in the SPLP; silver, arsenic, boron, cadmium, cobalt, magnesium, lead, antimony,

tin and vanadium were not detected in either test. Barium, chromium, iron and strontium

concentrations in the TCLP leachate were higher than the SPLP leachate, but relatively

similar. Only sodium was dramatically greater in the TCLP compared to the SPLP, but

this was because sodium is used in the TCLP solution. The TCLP and SPLP extracted

statistically similar concentrations of aluminum, copper, potassium, nickel and zinc.

Comparisons of TCLP and SPLP for other wastes have found that TCLP typically

extracts more metals than SPLP because of the buffered pH of the TCLP and the ability

of acetic acid to complex heavy metals. The degree of complexation differs depending

on the metal. Differences in metal leachability between TCLP and SPLP could be result

from several other factors. The initial pH of the SPLP solution (4.2) is less than the initial

pH of the TCLP solution (4.9). Also changes in the solution pH that occur during the 18

hour of leaching may differ between SPLP and TCLP, and thus result in different

amounts of metal leaching. In the case of PG, the pH difference between the two tests

was not very pronounced. The difference in metal concentrations between SPLP and

TCLP for PG are relatively small.

Figures 5-1 through 5-4 compare the average leachate concentrations using

SPLP, TCLP, DI and EPTOX for aluminum, barium, chromium and calcium. For

aluminum, all the tests leached similar concentrations and all of them were above

GWCTL. Barium was below TC limit for all the tests and TCLP leached barium greater

90

than SPLP and EPTOX. While MSW leaching solution leached calcium more than

TCLP, EPTOX and DI showed similar concentrations of calcium.

When the PG samples were leached with DI water, extracted concentrations were

relatively similar to the SPLP except calcium. DI water leached more calcium than

SPLP. The pH of DI water used for this test was greater than the TCLP and SPLP

extraction solutions. The pH is known as a major controlling factor for metal leachability

(Van der Sloot et al. 2001; Townsend, et al. 2004). The solubility of some metals

increased under extreme pH but this may not be applicable for all. For some metals the

change in pH had no effect (Tolaymat et al. 2008; Chuan et al. 1996). For some wastes

like wood, tire ash and wood ash, calcium, potassium and sodium concentrations were

controlled by solubility rather than pH (Tolaymat et al. 2008).This may be the case for

PG also.

The fact that most of the metals (except calcium) leached less in the MSW landfill

leachate relative to TCLP and SPLP is likely a result of the higher pH. Average pH of

leaching solution after 18 hours of agitation was 7.5 and initial pH of MSW leachate was

7.7 (Table 4-7). MSW leachate also leached considerable amount of sulfate from PG.

Under anaerobic landfill conditions, sulfate-reducing bacteria produce hydrogen sulfide

(H2S) from the sulfate (SO4-2) in gypsum and the organic carbon in waste material:

SO4-2 + 2CH2O ---> 2HCO3

-1 + H2S.

Here a simple hydrocarbon is used as a surrogate for organic wastes. This may

cause odor issues and possible health problems for workers.

For MEP some metals showed an increase in concentration in the second

extraction from the first extraction. As a reminder, the first extraction of the MEP was

91

performed using EPTOX extraction fluid (at a pH of 5.0). The subsequent extractions

were performed using a pH 3 synthetic rainwater solution. After first extraction, average

pH of leaching solutions was 4.71 (after 20:1 dilution) and after second extraction, the

pH decreased to 3.39. Studies have demonstrated that as pH decreases, metal

desorption increases; thus, metals are more soluble under acidic conditions, which

could be attributed to the tendency of metals to form soluble metal oxides in acidic

environments. After second extraction metal concentrations decreased with subsequent

extractions as there are less contaminant available for leaching.

5.3 Assessing Potential for Beneficial Reuse

The research presented here provides helpful information for making preliminary

assessments for phosphogypsum uses. Of all the trace elements analyzed in total metal

analysis test, only arsenic (UCL95) was found to exceed its respective SCTL value

(residential exposure). Following typical risk assessment procedures for the state of

Florida, this suggests that PG cannot be land applied in a setting where direct human

exposure might occur. When the SCTLs are utilized to assess risk from land application

of a waste, the waste materials are assumed to be present in a manner where they

replace the soil. In the case of an amendment such as PG, the waste is mixed with soil

and the concentration of chemicals that an individual is exposed to is not only a function

of the PG composition, but also of the background soil concentration and the rate of

application (Tolaymat et al. 2008). Also PG can be used in conjunction with other

materials such as coal ash for soil amendment (Lee et al. 2008). Further study with

mixed materials may explore beneficial use options. One important factor in the use of

phosphogypsum on agricultural lands is the possibility of radioactive element uptake by

plants. Mays and Mortvedt (1986) applied phosphogypsum containing 25 pCi g-1 226Ra

92

at rates up to 112 Mg ha-1 to the surface of a silt loam soil and grew successive crops of

corn, wheat, and soybean. Application of phosphogypsum at a rate of 112 Mg ha-1 had

no effect on the radioactivity levels in grain of corn, wheat, or soybeans. Analyses of soil

after soybean harvest showed that the level of radioactivity in the surface 15-cm layer

increased from 35 Bq kg-1 to 73 Bq kg-1at 112Mg ha-1 PG rate; the radioactivity level in

the subsurface layer was not affected. The 112 Mg ha-1 rate was more than 200 times

the normal rate of gypsum used for peanut fertilization. Additionally, they noted no

increases in grain Cd levels, but at the highest rate they found that corn growth slowed.

They speculated that the slower growth was due to an imbalance of Ca and Mg.

PG leached Al and Fe above GWCTL in SPLP, therefore cannot be reused in

Florida for land application, however, Al and Fe are secondary standards, and the other

leaching tests showed low leachability of heavy metals, so beneficial use possibilities

may exist under different regulatory scenarios. In fact PG can be used to alleviate AI

toxicity(In soil solutions containing abundant SO42- and F-, AI that is not complexed with

either of the ligands) from acid soil due to its precipitation and complexation reactions

with SO42- and F-. The reduction of Al toxicity in the subsoil by PG is a result of complex

set of mechanisms, including precipitation of aluminum as the result of liberation of OH-

ions from oxidic surfaces by ligand exchange with SO42-, formation of insoluble basic Al

sulfates, formation of complexes of Al with F (AlF2+, AlF+2 and AlF3).which are less toxic

than the uncomplexed forms of Al (Carvalho and Raij 1997, Alva and Sumner 1991).

From the leaching tests (TCLP, EPTOX, MSW leaching) it can be said that none of

the toxic metals that were tested in this study leached above TC limits. One potential

beneficial use of PG is its utilization as part of MSW landfill construction and

93

maintenance activities. Other possibilities are using PG as daily and intermediate landfill

cover and landfill foundation. At new landfill sites, compacted PG may be used as a

substitute for the large volume of soil required to be placed under the liner to provide

necessary grades. When MSW leachate contacts with PG, a few constituents of PG

such as calcium and sulfate, may be considerably leached out. PG samples released

considerable amount of calcium in all the leaching tests. Increased calcium

concentration in MSW leachate may enhance scaling in the leachate collection and

removal system. Sulfate also was considered as an easily mobile constituent from PG

to MSW leachate. Increasing sulfate in MSW leachate may be a concern in terms of

odor issues. On the other hand, in an anaerobic environment of landfill, PG could

enhance biodegradation of municipal solid waste (MSW) in the landfill. Since PG is

enriched with sulfate, it is reasonable to assume that a sulfate using bacterial colony

present in landfills will use phosphogypsum as an energy source after oxygen is

depleted. So use of phosphogypsum as landfill cover could enhance biological

decomposition of MSW.

However, if PG is utilized as a base material under a landfill bottom liner, these

issues may not be concerns because the contact of PG with MSW leachate would be

prevented by the landfill liner. However use of PG, in applications where it is in contact

with the MSW (either as cover material or as a direct amendment), needs to balance the

potential benefits (less soil usage, greater stabilization) with the potential deleterious

impacts (odors, impact on biogas collection and conversion systems). Exploration of

these uses was not the main focus of this study. But results of this study can be used

for the feasibility study.

94

5.4 Limitations and Recommendations

In this study, leachability characterization of PG was conducted using only batch

leaching test. For better understanding of PG leachability, dynamic leaching test and

other batch leaching test using different pH solutions and solid liquid ratios could help

evaluate how several test variables can affect leaching behavior of PG. Also leachability

studies could be conducted on PG along with other materials to see how they affect

leachability characteristics of PG.

95

Table 5-1. TCLP results found in the previous studies

Element Regulatory limit (mg/L)

FIPR, 1995 (Kendron)

(mg/L)

FIPR, 2005 (Rusch & Seals)

(mg/L)

In this study (mg/L)

As 5.0 0.882 NDa <0.002

Ba 100 0.17 ND 0.16-0.07

Cd 1.0 0.01 ND <0.001

Cr 5.0 0.05 - 0.04-0.02

Pb 5.0 0.1 ND <0.003

Ag 5.0 0.05 - <0.005

Hg 0.2 0.005 - -

Se 1.0 0.1 ND <0.004 aND = Not detected Table 5-2. Comparisons of DI water leaching test

Element % Fraction leacheda % Fraction leachedb

Cr 10 BDLc U 20 -- Zn 58 82

aAl Masri et al. (2004) bIn this study cBDL = Below detection limit (detection limits are presented in Appendix A) Table 5-3. Comparison of SPLP with previous leaching studies

Element % Fraction leacheda % Fraction leachedb (SPLP)

As 3 BDLc Cd 1 BDL Cr 5 15 Cu 9 21 U 4 -- Zn 3 51

aAl-Hwaiti et al. (2010) bIn this study cBDL = Below detection limit (Detection limits are presented in Appendix A)

96

Table 5-4. Comparison of trace metal concentrations (mg/kg)

Element Gypsum Wallboarda Phosphogypsumb Al 295 756 As -- 1.9 B 42.5 48.5 Ba -- 38.5 Ca 169360 142590 Cd 3.1 BDLc Co 9.2 BDL Cr 11.6 1.6 Cu 7.1 1.9 Fe 942 792 K -- 157 Mg 8475 BDL Mo 2.7 -- Mn 45.6 2.7 Ni 20.1 BDL S 133821 -- Pb 15.6 3 Se -- BDL Zn 16.6 4.3

aR. P. Wolkowski (2000) bIn this study cBDL = below detection limit

97

Figure 5-1. Aluminum (Al) concentrations in different batch leaching tests

Figure 5-2. Barium (Ba) concentrations in different batch leaching tests

98

Figure 5-3. Chromium (Cr) concentrations in different batch leaching tests

Figure 5-4. Calcium (Ca) concentrations in different batch leaching tests

99

CHAPTER 6 CONCLUSION

Phosphate mining in Florida is currently one of the state’s largest industries, and

produces approximately 40 million tons of waste material per year (Burnett et al. 1996).

The total and leachable concentrations in PG were characterized for a number of

metals. These data were then used to examine a variety of issues associated with

determining whether the PG could be beneficially used outside of a landfill (e.g., land

application as fill material, soil amendment).

Metal release was assessed using standardized batch leaching tests and

additional leaching experiments using specific leaching solutions. To identify potential

chemicals of concern, the concentrations of pollutants in the samples were compared

with the risk-based standards. Based on the TCLP test, none of the TCLP results

exceeded the regulatory toxicity limits showing PG samples did not meet the definition

of EPA Toxicity Characteristic under RCRA (40 CFR Part 261.30). Note that Mercury

and radionuclide were not tested in this study. However, in the SPLP tests aluminum

and iron exceeded their respective Florida groundwater cleanup target levels. When

MSW leachate contacts with PG, a few constituents of PG such as calcium and sulfate,

may be considerably leached. Increasing sulfate in MSW leachate may be a concern in

terms of increased hydrogen sulfide generation; hydrogen sulfide carries concerns of

odor and potential deleterious health effects to those exposed. PG samples released

considerable amounts of calcium in the TCLP, SPLP, EPTOX and in the leaching test

with MSW leachate and DI water.

The TCLP and the SPLP extracted relatively similar metal concentrations (except

calcium). Although arsenic was detected at high concentrations in the PG totals

100

analysis, it did not leach at concentrations that may pose a risk to human health and the

environment in all the leaching tests. In terms of risk assessment, from a direct human

exposure pathway, arsenic was found to be the most limiting element. The SPLP results

did not find arsenic to pose a risk, but has aluminum and iron concentrations above

GWCTL.

It is important to examine potential impacts of PG management to the groundwater

because in Florida, over 90% of residents rely on groundwater for a potable water

source. Also the results of this study can assist in the consideration of land application

of PG.

101

APPENDIX A ICP-AES DETECTION LIMITS

Table A-1. Method Detection Limits

Element MDL(mg/L)

Ag 0.005 Al 0.025 As 0.002 B 0.009 Ba 0.002 Be 0.001 Ca 0.07 Cd 0.001 Co 0.001 Cr 0.002 Cu 0.002 Fe 0.06 K 0.06 Mg 0.02 Mn 0.002 Mo 0.004 Na 0.44 Ni 0.002 Pb 0.003 Sb 0.006 Se 0.004 Sn 0.006 Sr 0.002 V 0.002 Zn 0.003

102

APPENDIX B TOTAL METAL ANALYSIS DATA

Table B-1. Total metal analysis results of PG samples collected from north wall (mg/Kg)

Element Sample 1 Sample 2 Sample 3

Ag BDLa BDL BDL Al 955 869 801 As 1.01 2.79 2.06 B 76.66 63.87 40.79 Ba 51.88 51.56 40.59 Be BDL BDL BDL Ca 179439 191994 142179 Cd BDL BDL BDL Co BDL BDL BDL Cr 1.89 2.28 1.56 Cu 2.18 2.67 1.12 Fe 938 944 828 K 114 153 110 Mg BDL BDL BDL Mn 2.15 2.04 1.95 Na BDL BDL BDL Ni BDL BDL BDL Pb 2.66 2.86 3.87 Sb BDL BDL BDL Se BDL BDL BDL Sn 5.47 7.06 6.31 V 1.44 1.00 2.24 Zn 4.17 5.19 3.37

aBDL = Below detection limit

103

Table B-2. Total metal analysis results of PG samples collected from south wall (mg/Kg)




104

Table B-3. Total metal analysis results of PG samples collected from east wall (mg/Kg)




105

Table B-4. Total metal analysis results of PG samples collected from west wall (mg/Kg)


Ag BDLa BDL BDL

Al 788 838 728

As 2.80 1.38 1.00

B 70.95 55.5 39

Ba 43.10 48.26 35.16

Be BDL BDL BDL

Ca 107139 118809 113622

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 1.31 0.9 1.86

Cu 2.58 1.71 1.65

Fe 808 620 725

K 170 206 149

Mg BDL BDL BDL

Mn 2.41 1.35 1.46

Na BDL BDL BDL

Ni BDL BDL BDL

Pb 3.14 1.99 2.96

Sb BDL BDL BDL

Se BDL BDL BDL

Sn 4.19 4.08 3.53

V 1.62 1.19 1.04

Zn 4.3 5.45 6.25 aBDL = Below detection limit

106

APPENDIX C TOXICITY CHARACTERISTIC LEACHING PROCEDURE DATA

Table C-1. TCLP test results of the samples collected from north wall (mg/L)


Ag BDLa BDL BDL

Al 1.81 1.66 1.71

As BDL BDL BDL

B BDL BDL BDL

Ba 0.14 0.11 0.09

Ca 956 887 889

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.03 0.03 0.03

Cu 0.02 0.01 0.02

Fe 0.38 0.58 0.51

K 1.16 1.71 1.64

Mn BDL BDL BDL

Na 1559 1399 1465

Ni 0.07 0.04 0.03

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 3.37 3.08 2.96

V BDL BDL BDL


107

Table C-2. TCLP test results of the samples collected from south wall (mg/L)


Ag BDLa BDL BDL

Al 1.96 2.18 1.73

As BDL BDL BDL

B BDL BDL BDL

Ba 0.09 0.1 0.07

Ca 945 1030 892

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.03 0.04 0.03

Cu 0.03 0.02 0.02

Fe 0.34 0.56 0.39

K 4.04 4.37 4.88

Mn BDL BDL BDL

Na 1512 1661 1435

Ni 0.03 0.04 0.02

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 3.02 3.27 2.82

V BDL BDL BDL


108

Table C-3. TCLP test results of the samples collected from east wall (mg/L)


Ag BDLa BDL BDL

Al 1.73 1.69 1.75

As BDL BDL BDL

B BDL BDL BDL

Ba 0.12 0.12 0.09

Ca 948 971 914

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.03 0.02 0.02

Cu 0.03 0.06 0.02

Fe 0.57 0.52 0.56

K 1.42 1.95 1.83

Mn BDL BDL BDL

Na 1500 1552 1445

Ni 0.02 0.02 0.02

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 3.2 3.25 3.01

V BDL BDL BDL


109

Table C-4. TCLP test results of the samples collected from west wall (mg/L)


Ag BDLa BDL BDL

Al 1.9 2.13 2.08

As BDL BDL BDL

B BDL BDL BDL

Ba 0.12 0.16 0.09

Ca 953 1003 990

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.03 0.04 0.04

Cu 0.03 0.02 0.02

Fe 0.54 0.36 0.32

K 1.81 1.09 1.92

Mn BDL BDL BDL

Na 1480 1571 1576

Ni 0.03 0.01 0.03

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 3.05 3.17 3.14

V BDL BDL BDL


110

APPENDIX D SYNTHETIC PRECIPITATION LEACHING PROCEDURE (SPLP) DATA

Table D-1. SPLP test results of the samples collected from north wall (mg/L)


Ag BDLa BDL* BDL

Al 2.12 1.79 1.81

As BDL BDL BDL

B BDL BDL BDL

Ba 0.09 0.07 0.08

Be BDL BDL BDL

Ca 697 632 639

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.01 0.01 0.02

Cu 0.02 0.01 0.02

Fe 0.38 0.46 0.41

K 1.41 1.37 1.34

Na 9.25 7.53 8.66

Ni 0.02 0.03 0.04

Pb BDL BDL BDL

Sb BDL BDL BDL

Sn BDL BDL BDL

Sr 2.41 2.4 2.42

V BDL BDL BDL

Zn 0.08 0.1 0.13 aBDL = Below Detection Limit

111

Table D-2. SPLP test results of the samples collected from south wall (mg/L)


Ag BDLa BDL* BDL

Al 2.12 1.72 1.79

As BDL BDL BDL

B BDL BDL BDL

Ba 0.06 0.05 0.06

Be BDL BDL BDL

Ca 676 521 602

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.02 0.01 0.01

Cu 0.02 0.03 0.06

Fe 0.3 0.18 0.22

K 3.3 2.26 2.51

Na 10.08 7.84 8.02

Ni 0.01 0.04 0.03

Pb BDL BDL BDL

Sb BDL BDL BDL

Sn BDL BDL BDL

Sr 2.25 1.7 1.98

V BDL BDL BDL


112

Table D-3. SPLP test results of the samples collected from east wall (mg/L)


Ag BDLa BDL BDL

Al 1.67 1.55 1.5

As BDL BDL BDL

B BDL BDL BDL

Ba 0.13 0.1 0.08

Be BDL BDL BDL

Ca 675 637 628

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.01 0.01 0.01

Cu 0.01 0.01 0.01

Fe 0.45 0.31 0.27

K 1.43 1.29 1.38

Na 9.75 8.31 8.98

Ni 0.04 0.02 0.01

Pb BDL BDL BDL

Sb BDL BDL BDL

Sn BDL BDL BDL

Sr 2.42 2.28 2.22

V BDL BDL BDL


113

Table D-4. SPLP test results of the samples collected from west wall (mg/L)


Ag BDLa BDL BDL

Al 1.49 1.67 2.64

As BDL BDL BDL

B BDL BDL BDL

Ba 0.06 0.06 0.07

Be BDL BDL BDL

Ca 593 617 644

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.01 0.01 0.01

Cu 0.02 0.02 0.02

Fe 0.39 0.17 0.22

K 1.19 1.25 1.75

Na 7.22 7.12 10.11

Ni 0.01 0.01 0.02

Pb BDL BDL BDL

Sb BDL BDL BDL

Sn BDL BDL BDL

Sr 2.03 2.17 2.18

V BDL BDL BDL


114

APPENDIX E EXTRACTION PROCEDURE TOXICITY TEST DATA

Table E-1. EPTOX test results of the samples collected from south wall (mg/L)


Ag BDLa BDL BDL

Al 1.83 1.73 1.80

As BDL BDL BDL

B BDL BDL BDL

Ba 0.06 0.05 0.05

Be BDL BDL BDL

Ca 752 743 739

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.04 0.04 0.04

Cu 0.19 0.12 0.12

Fe BDL BDL BDL

K 3.46 3.12 2.67

Mg 0.71 0.77 0.78

Mn BDL BDL BDL

Ni 0.06 0.06 0.05

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 2.34 2.30 2.35

V BDL BDL BDL


115

APPENDIX F MUTIPLE EXTRACTION PROCEDURE TEST DATA

Table F-1. MEP test results of the samples collected from south wall (extraction 1) (mg/L)

Cation Sample 1 Sample 2 Sample 3

Ag BDLa BDL BDL

Al 1.83 1.73 1.80

As BDL BDL BDL

B BDL BDL BDL

Ba 0.06 0.05 0.05

Be BDL BDL BDL

Ca 752 743 739

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.04 0.04 0.04

Cu 0.19 0.12 0.12

Fe BDL BDL BDL

K 3.46 3.12 2.67

Mg 0.71 0.77 0.78

Mn BDL BDL BDL

Ni 0.06 0.06 0.05

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 2.34 2.30 2.35

V BDL BDL BDL


116



Ag BDL BDL BDL

Al 2.97 2.81 2.90

As BDL BDL BDL

B BDL BDL BDL

Ba 0.05 0.05 0.05

Be 0.47 0.46 0.46

Ca 813 801 801

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.06 0.05 0.05

Cu 0.11 0.11 0.10

Fe BDL BDL BDL

K 2.16 2.87 1.12

Mg 0.75 0.53 0.78

Mn BDL BDL BDL

Ni 0.09 0.09 0.09

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 2.39 2.47 2.41

V BDL BDL BDL

Zn 0.49 0.41 0.35

*BDL = Below Detection Limit

117



Ag BDLa BDL BDL

Al 2.87 2.75 2.67

As BDL BDL BDL

B BDL BDL BDL

Ba 0.04 0.04 0.04

Be 0.45 0.45 0.45

Ca 786 782 776

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.05 0.05 0.05

Cu 0.10 0.10 0.09

Fe BDL BDL BDL

K 0.87 0.76 0.66

Mg 0.65 0.50 0.40

Mn BDL BDL BDL

Ni 0.09 0.09 0.09

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 2.44 2.43 2.37

V BDL BDL BDL


118



Ag BDLa BDL BDL

Al 2.65 2.65 2.57

As BDL BDL BDL

B BDL BDL BDL

Ba 0.04 0.04 0.04

Be 0.43 0.43 0.42

Ca 813 801 801

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.05 0.05 0.05

Cu 0.09 0.09 0.08

Fe BDL BDL BDL

K BDL BDL BDL

Mg 0.37 0.38 0.34

Mn BDL BDL BDL

Ni 0.09 0.09 0.09

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 2.34 2.28 2.28

V BDL BDL BDL


119



Ag BDLa BDL BDL

Al 2.55 2.53 2.50

As BDL BDL BDL

B BDL BDL BDL

Ba 0.04 0.04 0.04

Be 0.39 0.39 0.38

Ca 756 747 737

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.05 0.05 0.05

Cu 0.08 0.08 0.08

Fe BDL BDL BDL

K BDL BDL BDL

Mg 0.23 0.21 0.21

Mn BDL BDL BDL

Ni 0.09 0.09 0.09

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 2.24 2.23 2.18

V BDL BDL BDL


120



Ag BDLa BDL BDL

Al 2.31 2.30 2.26

As BDL BDL BDL

B BDL BDL BDL

Ba 0.04 0.04 0.04

Be 0.01 0.03 0.02

Ca 734 723 722

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.05 0.05 0.04

Cu 0.08 0.07 0.07

Fe BDL BDL BDL

K BDL BDL BDL

Mg BDL BDL BDL

Mn BDL BDL BDL

Ni 0.08 0.08 0.08

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 2.14 2.14 2.07

V BDL BDL BDL


121



Ag BDLa BDL BDL

Al 1.69 1.81 1.73

As BDL BDL BDL

B BDL BDL BDL

Ba 0.03 0.02 0.02

Be BDL BDL BDL

Ca 720 720 714

Cd BDL BDL BDL

Co BDL BDL BDL

Cr 0.04 0.04 0.04

Cu 0.06 0.06 0.06

Fe BDL BDL BDL

K BDL BDL BDL

Mg BDL BDL BDL

Mn BDL BDL BDL

Ni 0.08 0.08 0.08

Pb BDL BDL BDL

Sb BDL BDL BDL

Se BDL BDL BDL

Sn BDL BDL BDL

Sr 1.7 1.25 1.55

V BDL BDL BDL


122



Ag BDLa BDL BDL Al BDL BDL BDL As BDL BDL BDL B BDL BDL BDL Ba BDL BDL BDL Be BDL BDL BDL Ca 710 714 706 Cd BDL BDL BDL Co BDL BDL BDL Cr 0.04 0.04 0.04 Cu 0.06 0.06 0.05 Fe BDL BDL BDL K BDL BDL BDL Mg BDL BDL BDL Mn BDL BDL BDL Ni 0.08 0.08 0.08 Pb BDL BDL BDL Sb BDL BDL BDL Se BDL BDL BDL Sn BDL BDL BDL Sr BDL BDL BDL V BDL BDL BDL Zn BDL BDL BDL


123



Ag BDLa BDL BDL Al BDL BDL BDL As BDL BDL BDL B BDL BDL BDL Ba BDL BDL BDL Be BDL BDL BDL Ca 705 694 691 Cd BDL BDL BDL Co BDL BDL BDL Cr 0.04 0.04 0.04 Cu 0.05 0.04 0.04 Fe BDL BDL BDL K BDL BDL BDL Mg BDL BDL BDL Mn BDL BDL BDL Ni 0.08 0.08 0.07 Pb BDL BDL BDL Sb BDL BDL BDL Se BDL BDL BDL Sn BDL BDL BDL Sr BDL BDL BDL V BDL BDL BDL Zn BDL BDL BDL


124

APPENDIX G BATCH LEACHING TEST WITH DI WATER

Table G-1. Metal analysis data after batch test of PG with DI water of NW PG samples (mg/L)

Element Sample 1 Sample 2

Ag BDLa BDL Al 1.50 1.45 As BDL BDL B BDL BDL Ba 0.02 0.02 Ca 816 831 Cd BDL BDL Co BDL BDL Cr BDL BDL Cu 0.11 0.10 Fe BDL BDL K 1.55 1.42 Mn BDL BDL Mo 0.09 0.10 Na 11.51 10.79 Ni 0.02 0.02 Pb BDL BDL Sb BDL BDL Se BDL BDL Sn BDL BDL Sr 2.65 2.54 V BDL BDL Zn 0.10 0.11


125

Table G-2. Metal analysis data after batch test of PG with DI water of SW PG samples (mg/L)




126

Table G-3. Metal analysis data after batch test of PG with DI water of EW PG samples (mg/L)




127

Table G-4. Metal analysis data after batch test of PG with DI water of WW PG samples (mg/L)




128

APPENDIX H MSW LEACHATE BATCH LEACHING TEST DATA

Table H-1. Batch leaching test with MSW leachate for PG samples collected from north wall (mg/L)

Element Blank Sample 1 Sample 2 Sample 3

Al 0.2 0.2 0.19 0.17 As 0.16 0.14 0.16 0.15 B 6.47 6.59 6.97 6.43 Ba 0.05 0.05 0.04 0.04 Ca 85 1051 1170 1080 Co 0.03 0.03 0.03 0.03 Cr 0.08 0.08 0.08 0.07 Cu 0.02 BDLa BDL BDL Fe 5.96 2.60 3.53 2.99 K 847 858 928 853 Mg 36.43 36.09 38.76 35.86 Mn 0.14 0.12 0.13 0.17 Na 1558 1574 1711 1558 Ni 0.11 0.11 0.12 0.13 Sb 0.11 BDL BDL BDL Se BDL BDL BDL BDL Sn BDL BDL BDL BDL Sr 0.27 3.16 3.48 3.2 V 0.05 0.05 0.05 0.04 Zn 0.05 0.03 0.02 0.03


129

Table H-2. Batch leaching test with MSW leachate for PG samples collected from south wall (mg/L)




130

Table H-3. Batch leaching test with MSW leachate for PG samples collected from east wall (mg/L)


Al 0.2 0.18 0.13 0.21 As 0.16 0.16 0.14 0.14 B 6.47 7.00 6.34 6.37 Ba 0.05 0.06 0.05 0.03 Ca 85 1119 1154 1157 Co 0.03 0.03 0.03 0.03 Cr 0.08 0.08 0.07 0.07 Cu 0.02 BDLa BDL BDL Fe 5.96 2.96 2.74 2.51 K 847 917 869 855 Mg 36.43 37.72 36.06 35.57 Mn 0.14 0.11 0.1 0.1 Na 1558 1670 1577 1550 Ni 0.11 0.11 0.10 0.09 Sb 0.11 BDL BDL BDL Se BDL BDL BDL BDL Sn BDL BDL BDL BDL Sr 0.27 3.32 3.38 3.38 V 0.05 0.05 0.04 0.04 Zn 0.05 0.03 0.03 BDL


131

Table H-4. Batch leaching test with MSW leachate for PG samples collected from west wall (mg/L)




132

APPENDIX I QUALITY ASSURANCE/QUALITY CONTROL

Table I-1. QA/QC for TCLP

Element NW1Dup (mg/L

% Recovery

MS MSD

Ag BDLa 91 94 Al 1.81 82 91 As BDL 110 107 B BDL 88 87 Ba 0.14 87 103 Ca 960 83 81 Cd BDL 101 111 Co BDL 99 109 Cr 0.03 97 107 Cu 0.02 88 91 Fe 0.38 88 98 K 1.17 110 106 Mn BDL 104 106 Na 1559 85 87 Ni 0.07 83 87 Pb BDL 101 103 Sb BDL 86 82 Se BDL 93 94 Sn BDL 96 94 Sr 3.37 87 80 V BDL 92 98 Zn 0.29 88 94


133

Table I-2. QA/QC for SPLP


% Recovery

MS MSD

Ag BDLa 104 105 Al 2.2 110 106 As BDL 103 107 B BDL 96 99 Ba 0.09 95 100 Be BDL 93 97 Ca 700 90 95 Cd BDL 95 97 Co BDL 95 99 Cr 0.01 93 98 Cu 0.02 102 108 Fe 0.38 85 84 K 1.41 101 108 Na 9.25 85 94 Ni 0.02 93 98 Pb BDL 97 101 Sb BDL 87 96 Sn BDL 95 102 Sr 2.41 98 100 V BDL 90 91 Zn 0.08 90 97


134

Table I-3. QA/QC for DI water batch leaching test


% Recovery

MS MSD

Ag BDLa 97 95 Al 1.50 81 85 As BDL 98 94 B BDL 84 87 Ba 0.023 93 97 Ca 816 104 100 Cd BDL 97 99 Co BDL 87 86 Cr BDL 98 104 Cu 0.11 85 88 Fe BDL 93 95 K 1.55 105 102 Mn BDL 101 99 Mo BDL 100 103 Na 11.51 83 88 Ni 0.018 85 84 Pb BDL 118 110 Sb BDL 95 103 Se BDL 105 105 Sn BDL 101 102 Sr 2.65 100 96 V BDL 85 87 Zn 0.103 94 98


135

Table I-4. QA/QC for MSW batch leaching test


% Recovery

MS MSD

Al BDLa 105 103 As 0.14 101 98 B 6.59 100 95 Ba 0.05 91 93 Ca 1051 95 98 Co 0.03 108 104 Cr 0.08 95 98 Cu BDL 104 101 Fe 2.60 98 99 K 858 97 99 Mg 36.1 109 103 Mn 0.12 82 86 Na 1574 87 89 Ni 0.11 100 96 Sb BDL 105 101 Se BDL 94 97 Sn BDL 87 93 Sr 3.16 88 94 V 0.05 94 99 Zn 0.03 95 102


136

Table I-5. QA/QC for EPTOX

Element SW1Dup (mg/L

% Recovery

MS MSD

Ag BDLa 94 99 Al 1.83 87 92 As BDL 102 97 B BDL 98 104 Ba 0.06 99 98 Be BDL 95 98 Ca 752 108 104 Cd BDL 95 98 Co BDL 104 101 Cr 0.04 95 98 Cu 0.19 104 101 Fe BDL 98 99 K 3.46 97 99 Mg 0.71 109 103 Mn BDL 82 86 Ni 0.06 97 99 Pb BDL 87 86 Sb BDL 98 104 Se BDL 85 88 Sn BDL 89 94 Sr 2.34 100 102 V BDL 99 103 Zn 0.26 94 96


137

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BIOGRAPHICAL SKETCH

Shabnam Mostary was born in Cox's Bazar, a city in Bangladesh. She started her

education in Little Jewels School, and continued in Ispahani Public School and College

and Chittagong College. She joined to the Civil Engineering Department at Bangladesh

University of Engineering and Technology (BUET), where she got her B.Sc. Degree in

January 2008. She was accepted into the graduate program in the Department of

Environmental Engineering at University of Florida in August 2009. Her research

interests include water, wastewater and solid and hazardous waste management. She

received her ME from University of Florida in the spring of 2011.

by shabnam mostary - university of...

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