Journal of Hazardous Materials 287 (2015) 69–77

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Journal of Hazardous Materials

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Integrated synthesis of zeolites 4A and Na–P1 using coal fly ash forapplication in the formulation of detergents and swinewastewater treatment

Ariela M. Cardosoa, Martha B. Hornb, Lizete S. Ferretc, Carla M.N. Azevedoa,b,Marcal Piresa,b,∗

a Post-Graduation Program in Engineering and Technology Materials, Pontifical Catholic University of Rio Grande do Sul, Av. Ipiranga 6681,Prédio 30, 90619-900 Porto Alegre-RS, Brazilb Faculty of Chemistry, Pontifical Catholic University of Rio Grande do Sul, Av. Ipiranga 6681, Prédio 12B, 90619-900 Porto Alegre-RS, Brazilc Fundacão de Ciência e Tecnologia (CIENTEC), Rua Washington Luiz, 675, 90010-460 Porto Alegre-RS, Brazil

h i g h l i g h t s

• The two integrated synthesis processes, resulted in zeolites of similar purity.• Process 1 was more favorable than process 2 in terms of greater incorporation of Si.• Zeolite 4A was synthesized according to the conformity parameters for use in detergents.• Zeolite Na–P1 in the treatment of swine wastewater confirmed its high ion exchange capacity.

a r t i c l e i n f o

Article history:Received 6 October 2014Received in revised form22 December 2014Accepted 19 January 2015Available online 20 January 2015

Keywords:Coal fly ashZeolitesIntegrated synthesisDetergentsSwine wastewater

a b s t r a c t

Several researchers have reported zeolite synthesis using coal ash for a wide range of applications. How-ever, little attention has been given to green processes, including moderate synthesis conditions, usingwaste as raw material and effluent reuse or reduction. In this study, Brazilian coal fly ashes were usedfor integrated synthesis of zeolites 4A and Na–P1 by two different routes and under moderate operat-ing conditions (temperature and pressure). Both procedures produced zeolites with similar conversions(zeolite 4A at 82% purity and zeolite Na–P1 at 57–61%) and high CEC values (zeolites 4A: 4.5 meq Ca2+ g−1

and zeolites Na–P1: 2.6–2.8 meq NH4+ g−1). However, process 1 generated less effluent for the zeolite

mass produced (7 mL g−1), with low residual Si and Al levels and 74% of the Si available in the coal flyash incorporated into the zeolite, while only 55% is used in process 2. For use as a builder in detergents,synthetic zeolite 4A exhibited conformity parameters equal to or greater than those of the commer-cial zeolite adopted as reference. Treatment of swine wastewater with zeolite Na–P1 resulted in a highremoval capacity for total ammoniacal nitrogen (31 mg g−1).

© 2015 Elsevier B.V. All rights reserved.

1. Introduction

Typical commercial detergents from the 1950s containedaround 40% sodium tripolyphosphate (STPP). The growing use ofthese cleaning products, combined with anthropogenic pollution,such as the indiscriminate use of phosphate fertilizers on crops,

∗ Corresponding author at: Post-Graduation Program in Engineering and Technol-ogy Materials, Pontifical Catholic University of Rio Grande do Sul, Av. Ipiranga 6681,Prédio 30, 90619-900 Porto Alegre-RS, Brazil. Tel.: +55 51 33534305;fax: +55 51 33203549.

E-mail address: mpires@pucrs.br (M. Pires).

has resulted in environmental impacts that include water pollu-tion [1]. The substantial amount of phosphates in stagnant naturalwaters leads to the excessive growth of algae, which can causeeutrophication of the water source [2–4]. Guided by ecologicalsustainability and economic competitiveness, detergent manufac-turers are eliminating STPP and replacing it with other materials,including zeolites [5]. Zeolite 4A is used as a builder in the formu-lation of detergents due to its high cation exchange capacity (CEC)[6–9]. Zeolites are industrially produced using compounds contain-ing Al and Si, though many researchers have achieved satisfactoryresults employing coal fly ash (CFA) to synthesize different zeolites,such as Na–P1, 4A, sodalite, and Na–X [10–14]. Given their avail-

http://dx.doi.org/10.1016/j.jhazmat.2015.01.0420304-3894/© 2015 Elsevier B.V. All rights reserved.

70 A.M. Cardoso et al. / Journal of Hazardous Materials 287 (2015) 69–77

Table 1Characteristics of swine wastewater (Valley of Taquari – RS, Southern Brazil) usedin the study of decontamination with zeolite Na–P1.

Parameter Unit Value

pH – 5.7Conductivity �S cm−1 13.62NH4

+ mg L−1 1205K+ mg L−1 1747Ca2+ mg L−1 54.0Mg2+ mg L−1 23.0Na+ mg L−1 1128

ability and high content of silica and aluminum, these residues havesignificant industrial importance. The mineral forms (crystalline oramorphous) in which Si and Al are found in CFA are highly relevantin the selective formation of each type of zeolite [14–18].

Zeolite Na–P1, used in wastewater treatment [19–22], canbe easily produced by direct hydrothermal synthesis of fly ash,whereas, producing zeolite 4A requires a two-stage process[23–25]. The first stage consists of extracting Si from fly ash, fol-lowed by synthesis of pure zeolite 4A by combining the extract witha secondary source of aluminum. Solid waste from Si extractionmay be suitable for conventional synthesis of low-purity zeolites,such as zeolite Na–P1 [23,25]. The combination of these proceduresenables integrated conversion of fly ash into high purity zeolite 4Aand low-grade zeolite Na–P1 [23]. An alternative route for the inte-grated process could begin with direct synthesis of Na–P1, resultingin an extract with higher Si levels that produces pure zeolite 4Awhen combined with a secondary source of Al. To the best of ourknowledge, this alternative route has never been tested, althoughthe amount of waste produced is probably smaller than the routeinvestigated by Hollman et al. [23]. In addition, sustainable zeo-lite production should include moderate synthesis conditions (lowtemperature and pressure) and the use of low-cost reactors. Unfor-tunately, little attention has been given to these aspects, which maybe crucial to the viability of large-scale zeolite production usingwaste as raw material. It is important to underscore the major con-tribution of recent studies demonstrating a significant reductionin the synthesis time of different types of zeolites using ultra-sound and microwaves [26,27]. However, our research is aimedat obtaining as simple a process as possible, with reduced waterconsumption and effluent generation. In the present research, flyash from Brazilian coal combustion was used for green integratedsynthesis of zeolite 4A and Na–P1. Two integrated routes were eval-uated, using metallic aluminum as a second Al source and moderatesynthesis conditions. Physical, chemical, and mineralogical anal-yses were conducted to characterize the zeolites. An integratedprocedure is proposed to obtain high-purity zeolite 4A for use as abuilder in detergents, and zeolite Na–P1 as a secondary product forthe removal of ammonium ions from swine wastewater.

2. Materials and methods

2.1. Materials

Zeolite synthesis used fly ash generated by coal combustionin Unit B of the Presidente Médici Thermal Power Plant (UTPM)in Candiota (Rio Grande do Sul state – Brazil), as well as NaOH(Merck, 99.5%) and metallic Al (Synth, commercial grade). Samplesof commercial zeolites 4A and Na–P1 (Industria Quimica del Ebro –IQE, Spain) were used as comparison materials. Swine wastewater(2 L) was collected at a small pig farm (Vale do Taquari, SouthernBrazil), submitted to preliminary treatment (solid–liquid separa-tion) and immediately characterized in accordance with Table 1.Solutions of NH4Cl (Merck 99%) and CaCl2·2H2O (Merck, 99.5%)were used in cation exchange capacity (CEC) tests. All the solu-

tions were prepared using deionized water (Milli-Q Plus, Millipore,resistivity > 18 M� cm−1).

2.2. Integrated synthesis of zeolites 4A and Na–P1

Integrated synthesis of zeolites 4A and Na–P1 was carried outusing two different pathways, denominated processes 1 and 2. Inprocess 1 (Fig. 1) ash was activated by NaOH solution (3.0 mol L−1

and L/S ratio of 6 L kg−1) using the conventional hydrothermalprocess in a closed borosilicate reactor (Schott, 250 mL) at 100 ◦Cfor 24 h. The resulting product was separated by filtration (glassmembrane, Millipore, 0.22 �m) and washed several times withdeionized water to remove excess sodium and lower the alkalinecontent, then dried (100 ◦C for 2 h) and stored in a desiccator. Si andAl levels in the filtrate were determined by flame atomic absorp-tion spectroscopy (FAAS) and the possible glass reactor leachingwas taken in account in the balance adjust. As sodium is present inhigh concentration, a supplementary contribution by leaching fromglass reactor should be negligible. The molar ratio was adjustedto 1.0 (for zeolite 4A formation) by adding an alkaline solution(3.0 mol L−1) containing Al, previously dissolved from aluminummetal powder. The resulting solution was transferred to a borosili-cate glass reactor (Schott, 250 mL), stirred manually (2 min at 25 ◦C)and immediately heated at 90 ◦C for 1.5 h, followed by another 2.5 hat 95 ◦C, according to the adapted methodology [7]. Fig. 2 shows theflow chart depicting process 2, which begins with zeolite 4A syn-thesis. In the first stage, Si was extracted from fly ash in alkalinesolution (2.0 mol L−1 NaOH), in a water bath at 100 ◦C for 2 h withconstant magnetic agitation (5.0 rpm), and the filtrate was used tosynthesize zeolite 4A as described in process 1. The residual solid,depleted in silicon and aluminum, was employed to synthesizezeolite Na–P1 using the conventional hydrothermal process (seeprocess 1) in a closed borosilicate glass reactor. The resulting fil-trates for both processes were stored for further characterization.All experiments were made in duplicates.

The equations below were used to compare the efficiency ofthe processes and the effluent generation. The letters j and k indi-cate the synthesis process (1 or 2) and the type of zeolite (4A orNa–P1) produced, respectively. The semi-quantitative content ofzeolite (PZj

k) in the product of each stage, was calculated by Eq. (1),

comparing the cation exchange capacities. It used the experimen-tal cation exchange capacity (CECj

k, expressed in meq g−1) of the

synthetized products and the theoretical cation exchange capacity(TCECk) calculated by the chemical formula [28] of the zeolite 4A(5.48 meq g−1) and zeolite Na–P1 (4.60 meq g−1).

PZjk

= CECjk

TCECk× 100 (1)

The mass of the zeolites obtained (mZjk) was calculated using Eq.

(2), considering the semi-quantitative content of zeolite (PZjk) and

mass of the product (mPjk) formed at the end of the process.

mZjk

= mPjk

× PZjk

100(2)

In order to conduct a more detailed analysis of process efficiencyregarding the use of available raw material, expressions are pro-posed to analyze the relationship between the amount of siliconavailable in the ash and the amount that effectively incorporatedon zeolite structures. Based on the chemical formulas of each zeo-lite (Na–P1: Na6Al6Si10O32·12H2O and 4A: Na2Al2Si2O8·4.5H2O),the theoretical mass of silicon in the zeolite crystal (MSiZk) and themolecular mass of the zeolite (MZk) can be calculated. These values

A.M. Cardoso et al. / Journal of Hazardous Materials 287 (2015) 69–77 71

Fig. 1. Flow diagram of the zeolites synthesis 4A and Na–P1 by integrated process 1.

and the mass of zeolite in the product (mZjk, Eq. (2)) are used to

calculate the mass of silicon (mSiZjk) incorporated on the zeolite:

mSiZjk

= mZjk

× MSiZk

MZk(3)

To calculate the Si percentage incorporated in zeolite structure(Sij%), it is necessary to determine the mass of the silicon availablein the ash (mSiFAj) using the silicon perceptual content in ash (FASi),obtained by XRF (Supplementary material, Table A.1), and the massof the ash (mFAj) used:

mSiFAj = FASi

100× mFAj (4)

This value and the sum of the masses of the silicon on bothzeolites (

∑k

mSiZjk) given us:

Sij% =

∑k

mSiZjk

mSiFAj× 100 (5)

Another important aspect is the effluent generated at the endof the process. For a better comparison between the proposed pro-cesses a new parameter was calculated. The Ej

Z is defined as the

volume of effluent per mass unit of zeolite obtained and is calcu-lated by following equation:

EjZ =

⎛⎜⎜⎝

Ej∑k=2

mZjk

⎞⎟⎟⎠ × 100 (6)

where Ej is the total volume (mL) of effluent generated and the sumof the mass of the zeolites produced in the process (j).

2.3. Characterization of the synthetic zeolites

The morphology of the synthetic zeolites was studied usingScanning Electron Microscopy (SEM) and elementary analysis wasconducted by energy-dispersive X-ray spectrometry (EDS) withEDAX software. The following analyses were performed for chem-ical characterization: X-ray Diffraction (XRD), cation exchangecapacity (CEC) and leaching tests [18,29]. The cation-exchangecapacity of the zeolites was determined by saturation with ammo-nium ion without solution renewal, following the methodology ofthe International Soil Reference and Information Center [29]. Theleaching tests consisted of adding 1.0 g of zeolite in 50 mL of ultra-pure deionized water (Milli-Q, Millipore, resistivity > 18 M� cm−1)with mechanical stirring (Wagner, 5 rpm) for 2 h, followed bycentrifugation [18]. Parameters, such as pH (Digimed DM-21)

72 A.M. Cardoso et al. / Journal of Hazardous Materials 287 (2015) 69–77

Fig. 2. Flow diagram of the zeolites synthesis 4A and Na–P1 by integrated process.

and electrical conductivity (SHOT Lab 960) were determined.The concentration of cations (Na+, NH4

+, K+, Mg2+, and Ca2+) wasperformed by ion chromatography (IC) and other elements (As, Cu,Cd, Cr, Mn, Ni, Pb, and Zn) by FAAS.

2.4. Conformity analysis of zeolite 4A

The technical conformities of synthetic zeolite 4A were analyzedin both integrated processes, according to the standard operat-ing procedures supplied by Industrias Quimicas del Ebro (IQE,Spain). The sequestering power of Ca (mg CaO g−1) in the zeolitewas determined and the Ca2+ content was analyzed by IC. Chemi-cal composition (Al2O3, SiO2, and Na2O) was determined by X-rayfluorescence (XRF) and average particle size was established withlaser spectrometry (CILAS 1180, liquid mode) using the continuousdistribution method). The zeolites were analyzed in a Spectra-Match CM 2600d spectrophotometer with SpectraMatch software(version 3.5 D – Color Sensor version: 141) to measure white-ness. Complementary tests were performed in compliance withindustrial requirements: pH (5% m/v) in deionized water, appar-ent density (g L−1), oil adsorption (%) and loss through calcinationat 800 ◦C.

2.5. Ammonium ion removal from swine wastewater with zeoliteNa–P1

For ammonium ion removal, 1.0 g of synthetic zeolite Na–P1was placed in contact with 50 mL of swine wastewater under con-stant agitation for 30 min, followed by immediate centrifugationand analysis of the supernatant. Given the high ammonia content in

the effluent (Table 1), additional removal tests were conducted withappropriate dilutions in deionized water (2, 4, and 10X). Ammoniacontent was analyzed by IC before and after contact.

3. Results

3.1. Synthesis and characterization of zeolites 4A and Na–P1

Zeolites 4A and Na–P1 were formed as major phases in both inte-grated synthesis processes 1 and 2. Their structures were revealedby SEM (Fig. 3) and characterized by well-defined crystalline planesfor Na–P1 in process 1 (Fig. 3A), with less defined morphology forprocess 2 (Fig. 3C). Zeolite 4A exhibited typical morphology (facetedcubes) for both processes (Fig. 3B and D). In process 1, in additionto Na–P1, the formation of zeolite sodalite was observed via XRD(Fig. 4A), though probably only a small amount, since it was notdetected with SEM. The diffractogram also shows the presence ofunreacted quartz and mullite, originally present in the fly ash [14].The solubility of these minerals in NaOH and likely saturation ofthe reactive medium with Si and Al explain this behavior. ZeoliteX was also identified as a contaminant of zeolite 4A (Fig. 4B). Inintegrated process 2, zeolite Na–P1 was observed in the formationphase of zeolite 4A (Fig. 4C). This result does not compromise thequality of the zeolitic product, since zeolite Na–P1 is also used indetergent formulation.

Table 2 shows the best results obtained by zeolitization. Zeo-lite 4A is produced with the same quality (CEC 4.5 meq g−1) andsemi-quantitative zeolite content (82%) in both processes, indicat-ing that its formation can be controlled by adding a secondary Al

A.M. Cardoso et al. / Journal of Hazardous Materials 287 (2015) 69–77 73

Fig. 3. SEM images of zeolites synthesized by integrated process 1: 3A (zeolite Na–P1), 3D (zeolite 4A) and integrated process 2: 3C (zeolite Na–P1) and 3B (zeolite 4A).

source. In this study the amount of Al needed for zeolite 4A for-mation was estimated using the concentrations of this element,determined by FAAS, in the synthesis extracts. Zeolite Na–P1 isproduced in a similar manner in both processes, with a zeolite per-centage of 57% in the final product mass and 61% for processes 1and 2, respectively. In both cases, high CEC values were recorded forammonium (2.6–2.8 meq g−1), confirming the applicability of thiszeolite in the treatment of swine wastewater. The most importantdifferences between the two synthesis routes are the characteris-tics of the post-reaction solutions and the Si percentage availablein the ash used in zeolite formation (Sij%).

Process 1 is far more efficient in that it generates less effluentper gram of zeolite produced (Table 2). While process 1 gener-ates 110 mL, process 2 produces approximately four times more(425 mL). Considering zeolite mass in each process (mZj

k), it was

found that only 7 mL of wastewater was generated for every gramof zeolite produced in process 1, while this volume approximatelytripled in process 2 (20 mL g−1). In addition, the effluents in pro-cess 2 display higher Si and Al content when compared to process1 (Table 2). The low residual level of these elements indicates thatatom economy was maximized in process 1 by incorporating moreraw material in the final products, one of the twelve principles ofGreen Chemistry [30]. This result is also confirmed by the Si per-centage incorporated into the zeolites (Sij%), with 74% of availableSi used in process 1 and only 55% in process 2.

3.2. Leaching test of the zeolites

The leaching test was carried out using zeolites Na–P1 and 4Aobtained in integrated process 1, since these zeolitic products rep-resent the best results obtained in the remaining characterizationtests. Table 3 shows the cation content, pH, and conductivity ofthe leachate. Higher levels of the cations studied were observed inthe leachate of zeolite Na–P1 than that of zeolite 4A. The elementswith the highest concentrations were Na+, due to the use of NaOHsolution during synthesis, K+, Ca2+, and Mg2+. Significant quanti-ties of the last two elements are found in fly ash from Candiota,as reported in the literature [18,31]. It is important to note thelow leaching percentage recorded for cations, except in the caseof Na+ for Na–P1, calculated via the direct relationship betweenthe initial amounts of these elements in zeolites Na–P1 and 4Aand the final levels of these cations in the leachate (Table 3). Thechemical composition of the zeolites was obtained using the oxidecontent determined by FRX (Table A.4, Supplementary material).The high pH and conductivity values found in both leachates arejustified by the residual alkalinity of the zeolites and the presenceof solubilized cations in the medium. Only zinc was detected in lowconcentrations of 0.03–0.05 mg L−1 in the leachates of zeolites 4Aand Na–P1, respectively. The other evaluated elements presentedconcentration below the detection limit of the technique (Table 3).These results indicated that the synthesized zeolites present a good

Table 2Characterization, yield, and effluent generation for the zeolites synthesis by both integrated processes 1 and 2.

Process Fly ash Zeolite data Effluent CEC PZ

mFA mSiFA Zeolite mP mZ msiZ �msiZ Si E EZ CSi CAl Ca2+ NH4+ mean ± dp

(g) (g) (g) (g) (g) (g) (%) (mL) (mL) (mg L−1) (mg L−1) (meq g−1) (meq g−1) (%) (%)

1 15 4.8 Na–P1 13.5 7.7 2.0 3.5 74 110 7 1272 1242 n.d 2.6 57 ±44A 9.5 7.8 1.5 4.5 n.d 82 ±2

2 30 9.5 4A 9.0 7.4 1.5 5.2 55 425 20 18,800 5941 4.5 n.d 82 ±2Na–P1 23.5 14.3 3.7 n.d 2.8 61 ±3

mFA = initial ash mass, mSiFA = mass of the silicon available in the ash, mP = mass of the product, mZ = zeolite mass on the product, msiZ = mass of the silicon in the zeolite mass,�msiZ = sum of silicon mass in the zeolites produced (4A and Na–P1), Si% = percentage of silicon incorporated on both zeolites (4A and Na–P1), E = volume of effluent generated,EZ = amount of effluent produced for synthetic zeolite mass, CSi = silicon concentration, CAl = aluminum concentration, CEC = cation exchange capacity, PZ = semi-quantitativecontent of zeolite on products, dp = standard deviation, and n.d = not determined.

74 A.M. Cardoso et al. / Journal of Hazardous Materials 287 (2015) 69–77

Fig. 4. XRD diffractograms of the synthesis processes 1 (A and B) and 2 (C and D). A – zeolite 4A. P – zeolite Na–P1, S – zeolite sodalite, Q – Quartz, and M – Mullite.

A.M. Cardoso et al. / Journal of Hazardous Materials 287 (2015) 69–77 75

Table 3Characterization of the leachates and zeolites 4A and Na–P1 synthesized byProcess 1.

Parameter Zeolites Leachatea

Na–P1 4A Na–P1 4A

(mg kg−1) (mg kg−1) (mg L−1) (%) (mg L−1) (%)

Na+ 65 11 293 22 55 2.5K+ 7.2 3.1 4.73 3.0 0.59 0.9Mg2+ 5.6 4.2 0.45 0.4 0.60 0.7Ca2+ 17 1.1 2.18 0.6 1.83 8.3

Pb – – <0.01 – <0.01 –Mn – – <0.05 – <0.01 –Ni – – <0.01 – <0.01 –Cu – – <0.005 – <0.005 –Zn – – 0.05 – 0.03 –As – – <0.01 – <0.01 –Cd – – <0.001 – <0.001 –Cr – – <0.01 – <0.01 –Fe – – <0.05 – <0.022 –

pH – – 11.88 – 10.25 –Conductivity (�S cm−1) – – 1159 – 957 –

a −20 g L, rotatory agitation during 2 h (Wagner Agitator), 25 ◦C.

Table 4Characterization of the synthesized 4A zeolite (processes 1 and 2) and comparisonwith commercial grade 4A zeolite (IQE).

Parameters Zeolite 4A

Unit Process 1 Process 2 Comerciala

Chemical composition %, wt – – –Al2O3 – 27.5 28.1 28.0SiO2 – 33.5 31.7 33.0Na2O – 16.2 16.5 17.0Ignition loss −800 ◦C %, max 21.2 21.3 21.0Cation exchange mg CaO g−1 167.0 160.2 >160.0Oil absorption %, min 70 50 40Grain size �m 4.91 2.82 3.0–5.0Whiteness L 98.2 97.9 >96.0pHb – 11.2 11.4 11.0Bulk density g L−1 354 361 350

a Values provided by Industrias Quimicas del Ebro–IQE.b Suspension in H2O 5%.

leach resistance for the analyzed elements and confirm the supe-rior quality of zeolites 4A and Na–P1, indicating their suitabilityfor use as a builder in detergents and in wastewater treatment,respectively.

3.3. Conformity analysis of zeolite 4A

Table 4 shows the results of the conformity tests conductedusing the parameters required by the detergent industry for zeoliteapplication in their formulation. The last column of the table con-tains the amounts for commercial zeolite 4A, as indicated by thesupplier (IQE, Spain). This zeolite, commercialized as an adjuvantin detergent formulation to replace polyphosphates, was comparedagainst the zeolites obtained in this study. It was found that bothsynthesis routes (processes 1 and 2) produced high quality zeolite4A, with high Ca sequestering power. An important and particu-larly relevant parameter is lightness (L value), one of the greatestchallenged in this study, since the fly ash used as raw material isgreyish in color and can contribute to the formation of yellow zeo-lites. Detergent industry requirements for this parameter (L > 96.0)were met in the synthetic products (L > 97.9). Comparison betweensynthetic zeolites in processes 1 and 2 showed that higher qualityzeolite 4A was obtained in the first process. This zeolitic prod-uct exhibits better lightness, higher calcium sequestering powerand greater oil adsorption, as well as better pH values, apparent

density, and calcinations loss. Another important characteristic isparticle size distribution, given its influence on the kinetics of waterhardness removal by zeolites, with the zeolites in both processesfalling within the required range. Among the conformity param-eters, it is important to determine the chemical composition ofthe oxides (Al2O3, SiO2, and Na2O), because the values obtainedby XRF can be used to confirm the chemical formula of zeolite4A by calculating the mass and molar amounts of Si, Al, and Na(Tables A.2 and A.3, Supplementary material). These results indi-cated that waste used in moderate and integrated processes issuited to the production of high quality zeolite as a builder fordetergents.

3.4. Treatment of swine wastewater with zeolite Na–P1

Table 5 shows that after contact with synthetic zeolite Na–P1,the original and diluted effluents (2, 4, and 10X) exhibited adecline in total ammoniacal nitrogen concentration [NH4

+ + NH3]of 52%, 59%, 81%, and 70%, respectively. It is important to notethat wastewater dilution, associated with the presence of zeolite,caused an increase in pH from 7.11 to 10.70. The effluent wasdiluted to obtain ammoniacal nitrogen concentrations closer tothose reported in the literature for treatment with zeolites [32–35].Another aspect to be considered is the conversion of ammoniumion into ammonia, which can be volatilized by the increased pHof the medium, leading to overestimation of NH4

+ removal [36].Table 5 shows an estimate of the percentage contribution of ammo-nia concentration to ammoniacal nitrogen, which varies from 0.7%to 97% for the original effluents (pHfinal 10.70). As expected, theamount of ammonium adsorbed by zeolite mass (q) declined withwastewater dilution (31–4 mg g−1). It is important to underscorethat the maximum q obtained in this study is higher than thatreported (3.8–7.2 mg g−1) by Penn et al. [22] under similar con-ditions (batch shaken tests) using natural zeolites (Clinoptilolite70–85% pure).

Despite the significant ammonia adsorption capacity of the zeo-lites in pH close to 7 (original effluent), the results recorded wereabove the disposal limit (26 mg L−1 of ammoniacal nitrogen) [37].The wastewater used was only submitted to solid/liquid separation,making it far more concentrated in elements other than ammo-nium, hampering its treatment. Swine wastewater treated withzeolites typically undergoes several primary treatments (sedimen-tation, flocculation, anaerobic lagoons, etc.), which significantlyreduce the organic load and nutrients. Table 6 shows the cationlevels in the original effluent, before and after contact with zeoliteNa–P1 (30 min, 20 g L−1, 25 ◦C, and 5.0 rpm). There was a decline inthe ammonium (52%), magnesium (−42%), and potassium (−29%)concentration of the treated wastewater. These ions were proba-bly exchanged with the sodium and calcium ions present in thezeolite structure. The role of calcium, present in coal ash and prob-ably partially solubilized during zeolite synthesis, can be explainedby its incorporation as compensation ions, along with sodium, inthe zeolite structure. This is justified by the varying concentra-tion of sodium and calcium desorbed from the zeolite, with theresulting 50% and 69% increase in their concentrations in solution,respectively. The results obtained can be better evaluated by takinginto account the variation (�C) in load balance of the exchange-able cations (meq L−1). Table 6 shows load variation close to zero(+1.1 meq L−1), indicating that the species assessed represent themain exchangeable cations. This result also indicates good ana-lytical quality data. The competition between K+ and Mg2+ ionsand NH4

+ is evident in their decreased concentration in the treatedwastewater. However, the high initial Na+ and Ca2+ levels are likelyto negatively influence the exchange of these compensation ions forammonium in the zeolite structure.

76 A.M. Cardoso et al. / Journal of Hazardous Materials 287 (2015) 69–77

Table 5Ammonium removal from swine wastewater after two sequential contact with the synthetic zeolite Na–P1 (30 min, 20 g L−1).

Affluent Effluent Removal

Dilution Conductivity [NH4+]initial pHfinal [NH4

+]final [NH3]finala Qb

(�S cm−1) (mg L−1) (mg L−1) (%) (%) (mg g−1)

0 12.80 1205 7.11 581 0.7 52 312× 8.12 578 8.05 237 6.0 59 174× 4.95 340 9.30 63 53 81 1410× 2.80 125 10.70 38 97 70 4

a Calculated using pKa 9.25, (25 ◦C).b Q is the ratio between amount (mg) of NH4

+ adsorbed and zeolite mass (g) used.

Table 6Initial and final concentrations (after contacting the synthetic zeolite Na–P1) of all cations present in swine wastewater.

Element Cinitial Cfinal Adsorbed or desorbeda Cinitial Cfinal �C(mg L−1) (mg L−1) (%) (meq L−1) (meq L−1) (meq L−1)

NH4+ 1205 581 +52 66.8 32.2 −34.6

Mg2+ 231 135 +42 4.8 2.8 −2.0K+ 1747 1246 +29 44.7 31.9 −12.8Na+ 1129 2255 −50 49.1 98.1 +49.0Ca2+ 54 175 −69 0.7 2.2 +1.5Sum – – – 166.0 167.1 1.1

a Negative values indicate adsorption and positive values indicate desorption, calculated by: adsorption = [Cf − Ci]/Ci × 100 and desorption = [Cf − Ci]/Cf × 100.

4. Conclusion

The two integrated synthesis processes, using moderate con-ditions and waste (coal ash and metallic aluminum), resulted inzeolitic products of similar purity and conversions. It was possibleto produce zeolite 4A with good purity (82%) and low-grade zeoliteNa–P1 (57–61%). However, process 1 was more favorable than pro-cess 2 in terms of greater incorporation of Si, found in the ash, intothe zeolite structure and the lower volume and concentrations of Siand Al in the wastewater generated. With respect to the conformityparameters for use of zeolite 4A as a builder in detergents, the syn-thetic zeolites in both processes obtained results equal to or betterthan the commercial zeolite used as reference. Swine wastewatertreatment showed highly significant results. The application of zeo-lite Na–P1 in the treatment of swine wastewater confirmed its highremoval capacity (31 mg g−1) for total ammoniacal nitrogen. Evenin the presence of high levels of other cations, the ammonia concen-tration of 1205 mg L−1 declined by half, suggesting that low-gradeNa–P1 is suitable for the treatment of swine wastewater.

Acknowledgements

The authors are grateful to the CNPq and FAPERGS for theirfinancial support and the Master’s scholarships awarded. Specialthanks to Mr. Francisco Cacho (Ind., Quimica del Elbro, Spain) fordonating zeolites and to the LabCEMM-PUCRS for SEM analysis.

Appendix A. Supplementary data

Supplementary data associated with this article can be found,in the online version, at http://dx.doi.org/10.1016/j.jhazmat.2015.01.042.

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