leaching characteristics of fly ash

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Leaching characteristics of fly ashAysenur Ugurlu

Abstract The disposal of fly ash as a byproduct ofthermic power stations, results in significantenvironmental problems. The leaching of coal fly ashduring disposal is of concern for possiblecontamination, especially for the aquaticenvironment when ash is in contact with water. Theaim of this study was to investigate the leaching

behaviour of fly ashes currently disposed inKemerkoy Power Plant (Turkey) fly-ash-holdingpond. The studies were conducted with fly ashesfrom the electrostatic precipitators (fresh fly ash)and from the fly ash pond (pre-leached fly ash). Thefly ashes has alkaline in nature and pH rangesbetween 11.9 to 12.2. The pre-leached fly ashexhibited lower EC values (7,400 lS) than the freshfly ash (10,300 lS). In contrast to Fe and Pb, theelements such as Cr, Cd, Cu and Co did not leachfrom the fly ash. The Ca and Mn concentrationsdecreased with increasing temperature whereas, Naand K concentrations increased. The results showed

that the most important effects of fly ash leachingwere pH, Na, Ca, K, Fe, Mg, Mn and Pb.

Keywords Ash pond Coal solid waste Flyash Leaching

Introduction

Coal is the most abundant and widely spread fossil energyresource in the world (Benito and others 2001). Fly ash is abyproduct of incineration of coal. More than 150 million

tons of fly ash are produced annually worldwide from thecombustion of coal in power plants. Fly ash is utilized incement and construction industry. However, the rate ofproduction is greater than the consumption. The unusedfly ash is disposed into the holding ponds, lagoons, land-fills and slag heaps. Disposal of huge amounts of fly ash inlandfills and surface impoundments or its re-use in con-struction materials is of environmental concern (Piekos

and Paslawska 1998). Fly ash is classified as a hazardousresidue.Coal contains significant quantities of various trace ele-ments and, during combustion of coal, trace elements areenriched as a result of carbon loss as carbon dioxide andthe trace elements are associated with the surface of theash particle due to evaporation and condensation. Thecharacteristics of the coal used and the type of theinstallation employed in generating the solid combustionwastes (fly ash) have a direct influence on chemical andmineralogical composition of fly ash (Benito and others2001).The disposal of fly ash is considered a potential source of

contamination due to the enrichment and surface associ-ation of trace elements in the ash particles (Choi andothers 2002). The elements Mn, Ba, V, Co, Cr, Ni, Ln, Ga,Nd, As, Sb, Sn, Br, Zn, Se, Pb, Hg and S in the coal arevolatile to a significant extent in the combustion process.However, the elements Mg, Na, K, Mo, Ce, Rb, Cs and Nbappear to have smaller fraction volatilized during com-bustion. Whereas, Si, Fe, Ca, Sr, La, Sm, Eu, Tb, Py, Yb, Y,Se, Zr, Ta, Na, Ag, and Zn are either not volatilized or onlyshow minor trends related to geochemistry of mineralmatter (Iyer 2002).During transport, disposal and storage phases, the resi-dues from coal combustion are subjected to leaching ef-

fects of rain and part of the undesirable components in theashes may pollute both ground and surface waters (Benitoand others 2001). These solid residues (fly ash) can beleached in higher concentrations than drinking waterstandards and can cause contamination in drinking watersources.Therefore, it is important to predict the leaching behaviourof residues to prevent the environmental effects, especiallyfor the aquatic environment when ash is in contact withwater. The toxic elements leached from fly ash can con-taminate soil, ground water and surface water. Therefore,effective water management plans are required for fly ashdisposal. Although chemical composition of coal waste can

Received: 8 July 2003 / Accepted: 7 May 2004Published online: 9 June 2004 Springer-Verlag 2004

A. UgurluEnvironmental Engineering Department, Hacettepe University,06532 Beytepe, Ankara, TurkeyE-mail: [email protected].: +90-312-2977822Fax: +90-312-2992053

890 Environmental Geology (2004)46:890895 DOI 10.1007/s00254-004-1100-6

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give us an idea about the pollutants passing through water,in order to quantify these phenomena it is necessary tocarry out leaching tests.Lau and Wong (2001) found that different elements havedifferent leaching behaviours because of differences inelemental properties and pH of the solution and leachingtime, which strongly influence the leaching behaviour.

Seferinoglu and others (2003) reported that trace-elementleaching from bottom ash is slower and often requires thatthe entire bulk matrix be dissolved.The aim of this study is to investigate the leachingbehaviour of fly ashes disposed in the Kemerkoy PowerPlant (Turkey) ash pond and to investigate the potentialinfluence from the ash disposal on ground water quality.The study includes batches of leaching tests with fly ashbefore disposal and with fly ash slurry collected from thefly ash pond.

Materials and methodsChemical composition

The main method of disposal of fly ash from the powerplant is mixing with water. The resultant slurry is trans-ferred to an ash-disposal pond. Random samples of freshlygenerated fly ash have been collected (5 kg) from theelectrostatic precipitators in the Kemerkoy ThermoelectricPower Plant and then mixed. The pre-leached fly ash wascollected at various parts of the fly ash pond located 800 mto the Plant at 5 cm below the surface and then mixed. Thesamples were taken from the part where the fly ash hadbeen stored for 1 week to 3 months. The coal and fly ash

samples were analysed by X-ray diffraction (XRD). Thephysico-chemical properties of the elements in the fly ashis related to their chemical form in the coal, coal com-bustion process and mechanisms of emission-controldevices. The fly ash was produced through the combustionof lignite coal, which is transported from the nearby area(Yatagan). The composition of the lignite coal and somephysical properties are shown in Table 1. The ash contentof the coal was about 33%. The lignite coal burnt in thepower plant produced fly ash with a high lime content(15.819.7%) as well as Fe2O3(1.22.8%), SiO2(8.212.6%)and Al2O3 (3.05.1%; Baba 2000). The fly ash is a finepowdery residue with particle sizes in the range of 63 to125 lm. Data on chemical composition of fly ash takenfrom the incinerator (FA-1) and from the fly ash pond

(FA-2) are shown in Table 2. The fly ash contains highconcentrations of silica together with oxides of Ca, Al andFe. The fly ash has very high organic content that was notlost during combustion (12.7%). Mg, Na, Ti, K and Pcontent account for only 3.5%. Trace elements make upthe rest of the fly ash.As can be seen from the Table 2, there are slight differ-

ences between the chemical composition of FA-1 andFA-2. The wet disposal of the fly ash into the ash pondcaused leaching of some constituents from the fly ash dueto weathering. Some constituents showed an increase dueto leaching of some constituents from the fly ash particles.

Batch leaching testsA series of batch leaching tests were conducted in thelaboratory. In order to better simulate the natural condi-tions and susceptibility to release a lower-liquid-to-solid(L/S) ratio was used. Therefore, 5-g fly ash samples weremixed with 25 ml of de-ionized water, giving a liquid/solidratio of 5. Three subsequent extractions with the same

volume were applied and gentle stirring was continuedduring the extraction (2 h). The experiments were carriedout at room temperature (23 C), and at 40 and 50 C. Theresults were calculated using the mean value of duplicates.The fly ash samples were tested for characteristic proper-ties related to leaching behaviour. The tests were con-ducted in order to distinguish the easily leachable and lessreadily released loads of soluble components. The fly ashsamples were tested for characteristic properties related toleaching behaviour. In these studies, the leaching of Ca,Mg, Na, K, SO4 , Mn, Pb, Cd, Cu, Co, Fe, pH and con-ductivity (EC) from fly ash were investigated in order topredict potential pollution. The results were calculated

using the mean value of duplicates of each extraction.

Environmental Geology (2004) 46:890895 891

Table 1Chemical and physical characteristics coal

Parameter Coal(mean SD)

Moisture (%) 31.65Ash (%) 33.410Sulfur (%) 0.820.25Gross calorific value (kcal/kg) 1,805288Density (g/cm3) 1.140.06

Table 2Chemical analysis of fly ash. FA-1fly ash from Incinerator; FA-2 flyash from pond; DLS dolomitic limestone; CLS cherty limestone

Fly-ash-1 Fly-ash-2 DLS CLS

Major elements (wt%)SiO2 26.4 25.3 4.61 57.85Al2O3 10.0 9.43 9.87Fe2O3 3.4 3.3 0.48 4.24MnO 0.05 0.04 0.133MgO 1.72 1.84 10.56 1.34CaO 33.8 30.1 37.86 9.95

Na2O 0.15 0.16 K2O 1.0 1.0 1.81Ti2O 0.43 0.41 0.47P2O5 0.23 0.21 0.13Trace elements (ppm)Nb 6.3 8.1 1.3 1.1Zr 73.5 74.2 15.0 12.2Y 13.9 14.5 3.5 8.0Sr 380.7 358.4 100.1 88.6Rb 41.7 41.7 2.6 5.0Ga 6.3 6.5


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In addition to the leaching tests using de-ionized water,adsorption studies were also conducted by using the typ-ical ground profile beneath the ash pond. The fly ash wasstored in a valley located on a karstic and fractureddolomitic and cherty limestone basin. The ash level was3 m at the time of sampling (during plant start-up stud-ies). It was expected that the ash level in the pond would

increase to 130 m. Limestone is the most extensive rockunit in this area and it is reported that it is densely frac-tured, porous and partly karstified (Baba 2000). Thesebasins are present beneath an alluvial layer (1 m). Theleaching studies with these rock types were also conductedin order to determine the background concentrations, thepossible elemental contamination from fly ash disposaland possible adsorption on these rock types. These rocksamples were collected nearby the ash-disposal site fromdrilling studies (150 m), which did not come into contactwith leachates. In these studies, the leaching behaviour ofFA-1 and FA-2 samples (5 g) were studied when they werein contact with dolomitic (DLS) or cherty (CLS) limestone

samples (5 g) and 25 ml of distilled water. The ash sampleswere dried at 110 C prior to batch analysis.

Analytical methodsAll the analyses were carried out according to standardmethods (APHA 1989). The Ca, Mg, Na, K and trace ele-ments were analysed by an atomic adsorption spectro-photometer (Perkin Elmer 2280). pH was measured by anEDT instruments BA 350 pH meter. All the samples werefiltered through a 0.45-lm micropore membrane filterprior to analyses.

Results and discussion

Leaching studies are important in predicting the envi-ronmental impacts associated with the disposal into fly ashponds. In these studies, the leachability of elements fromfresh fly ash (FA-1) and weathered fly ash samples takenfrom the ash pond (FA-2) in the Kemerkoy Power Plant

were compared. During these studies, leaching of calcium,sodium, magnesium, sulphates, potassium and variousheavy metals from fly ash was determined. The fly ashsamples were extracted three times with each extractionlasting 2 h.The effect of number of extractions on the leachability ofEC and pH was studied. It is suggested that the leachability

of toxic trace elements from fly ash particles is affected bythe number of extractions. The EC values decreased withthe number of extractions at all temperatures applied andthe highest EC values were observed in the first extraction(see Table 3). Therefore, cation concentrations decreasedafter each extraction. The EC from FA-1 reduced from10,300 to 5,400 lS after the third extraction at roomtemperature. The leachate of the pre-leached fly ash (FA-2)exhibited lower EC values than the fresh fly ash (FA-1).The difference was significant. This is probably related tothe higher ion dissolution that occurred from the FA-1.The lower EC values of the FA-2 can be explained byleaching to some extent in the ash pond.

The ECs of the rock samples were low and average valueswere about 70 lS for both rock types. The studies with theunderlying rock samples showed that a decrease in ECvalues of the fly ash samples was not significant for bothrock types and, therefore, it can be expected that high ECvalues are released to the ground water. The pre-leachedfly ash reaction with both rock samples resulted in lowerEC values than fresh fly ash. In these studies, FA-1 withdolomitic limestone exhibited slightly lower EC valuesthan that of cherty limestone.There are significant differences among the conductivity ofthe leachates at room temperature and at 40 and 50 C.The first extraction of FA-2 at room temperature was

7,420l

S. It decreased to 4,170l

S at 40

C and increasedto 7,000 lS at 50 C. The conductivity change of leachatefrom FA-1, with respect to temperature, was different thanthat of FA-2. The EC decreased with increasing tempera-ture. However, higher conductivity cannot be attributed tothe higher dissolution rates of K and Na for both fly ashesin the heated leaching experiments with respect to ambientextractions.

892 Environmental Geology (2004) 46:890895

Table 3EC values from the batch leaching tests (lS). FA-1fly ash from incinerator; FA-2fly ash from ash pond; FA-1+DLSFA-1 mixed with dolomiticlimestone; FA-1+CLSFA-1 mixed with cherty limestone; FA-2+DLSFA-2 mixed with dolomitic limestone; FA-2+CLSFA-2 mixed with chertylimestone

Batch leachingtests

T FA-1 FA-2 DLS CLS FA-1 +DLS

FA-1 +CLS

FA-2 +DLS

FA-2 +CLS(C)

Test 11st extraction 23 10,300 7,420 90 92 7,840 8,540 3,260 4,8302nd extraction 23 5,730 4,310 69 64 5,630 6,470 2,530 3,6803rd extraction 23 5,400 3,550 60 48 5,370 5,630 2,820 2,960Test 21st extraction 40 7,860 4,170 105 88 5,450 8,880 1,980 2,7002nd extraction 40 6,140 4,470 89 60 5,130 5,620 1,718 2,7503rd extraction 40 5,990 4,050 80 52 4,860 5,700 1,388 2,430Test 31st extraction 50 7,500 7,000 88 120 7,160 5,800 4,160 3,4802nd extraction 50 3,400 4,500 55 98 4,610 4,170 2,900 2,4803rd extraction 50 2,350 3,490 49 83 3,950 3,750 1,906 2,060

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Batch leaching tests showed that the pH values of theweathered and fresh fly-ash samples were both alkaline innature and the pH of the leachate from FA-1 and FA-2ranged from 11.8812.97 and 11.2712.48, respectively(Table 4). This was probably due to the high Ca content ofthe fly-ash samples. Similar results have been observed inprevious studies (Choi and others 2002). The change in pH

with the number of extractions was insignificant. Theeffect of temperature on leaching of fly ash was studied inthe range of 2350 C using distilled water. The effect oftemperature on pH-leaching tests showed that for both flyash samples pH values decrease when the temperature wasincreased to 40 C and increase when the temperature wasfurther increased to 50 C. The leaching tests were alsoconducted for rock samples. Both rock types have alkalineproperties and the pH of the dolomitic limestone (DLS)ranged from 8.31 to 8.65 and the cherty limestone (CLS)ranged between 8.36 to 9.23. When the ash samples weremixed with DLS or CLS samples, the pH of the leachatewas slightly lower than the pH values observed for FA-1

and FA-2 leachates. This may indicate that the high pHvalues will probably reach the groundwater.The main components of the fly ash are Ca, Na, K and Mgand they were leached in high amounts from the fly ashsamples. Calcium amounts leached from FA-1 and FA-2showed significant differences. The leaching studies atroom temperature showed that about 50% lower Ca wasextracted from FA-2 than FA-1. The Ca concentrationleached from FA-1 was 880 mg/l whereas it was 460 mg/lfrom FA-2 at this temperature. This can be explained bythe leaching of Ca in some extent in the ash pond. Itprobably combined with CO2present in the rock and/or inthe air, and resulted in the formation of low solubility

calcium carbonate (CaCO3

). The concentration of Ca de-creased when temperature was increased. A similar trendwas also observed by Khanra and others (1998). It issuggested that Ca can be precipitated as CaSO4 and/orCaCO3. The Ca concentrations leached at 50 C weresimilar for both fly ash samples (about 600 mg/l). How-ever, Na and K concentrations increased with temperature.The coal solid waste is disposed of in an ash pond lying ona dolomitic and cherty limestone basin. The leaching

studies of dolomitic and cherty limestone showed very lowCa concentrations. When the rock samples were in contactwith fly ash samples, this resulted in Ca concentrationsbeing increased. The FA-2 reaction with rock samplesexhibited lower Ca values than FA-1. In these studies bothfly ash samples, in contact with DLS, showed lower Cavalues than that of CLS. However, most of the Ca was not

retained in the rock.Higher concentrations of Mg were extracted from rocksamples than that of both fly ash samples. Magnesium wasfound as a less readily soluble component of the fly ashand this suggests that it was incorporated within theinterior of the fly ash. Slightly lower Mg values weremeasured from the pre-leached fly ash. Potassium andsodium were also leached in higher amounts from FA-2than FA-1. They were probably present in the interior partof the fly ash and were leached for longer periods. Sig-nificantly higher K concentrations were leached from FA-2samples (255 mg/l) than FA-1 (49 mg/l). It was seen thatwhen both of the fly ash samples were in contact with rock

samples, the K concentration did not interact with anyrock samples. The potassium concentration leached fromFA-2 was slightly reduced when it was in contact with CLS.Therefore, it can be expected that K concentrations willalso be transported to the ground water. High Na con-centrations will also be transported to the ground water.The leachability of Cu, Cr, Pb, Mn, Co and Fe from fly ashwas also studied. Chromium did not leach from the fly ashsamples. The leached Cu concentrations were close to thedetection limit. This is probably because Cr and Cu areprecipitated as their insoluble hydroxides. The lead con-centration of FA-1 and FA-2 samples did not show dif-ferences. Higher Mn concentrations (0.210.76 mg/l) were

leached out from both rock types than any fly ash samplesat any temperature applied. In the present studies, Ca, SO4,Pb, Mn and Co leached in higher amounts from fresh flyash than the pre-leached fly ash. However, Mg, Na, K, Cuand Fe are higher in the pre-leached fly ash. The effect oftemperature was insignificant for some ions. Mn and Cuconcentrations did not change with temperature.Iron oxides have a lower solubility in distilled water. Ironleached from fly ash is probably precipitated as hydroxides


Table 4pH values from the batch leaching tests. FA-1 fly ash from Incinerator; FA-2fly ash from ash pond; FA-1+DFA-1 mixed with dolomiticlimestone; FA-1+CFA-1 mixed with cherty limestone; FA-2+D FA-2 mixed with dolomitic limestone; FA-2+CFA-2 mixed with chertylimestone

Batch leachingtests

T FA-1 FA-2 DLS CLS FA-1 +DLS

FA-1 +CLS

FA-2 +DLS

FA-2 +CLS()

Test 11st extraction 23 12.78 12.47 8.31 8.36 12.66 12.03 11.97 12.002nd extraction 23 12.28 12.07 8.40 9.23 13.03 12.04 12.52 11.983rd extraction 23 12.28 11.97 8.40 9.18 12.17 12.12 11.87 11.88Test 21st extraction 40 11.88 11.27 7.67 8.01 11.68 12.14 11.15 11.122nd extraction 40 11.82 11.33 7.93 8.30 11.95 11.97 11.04 11.523rd extraction 40 12.16 11.29 8.37 8.63 11.39 11.32 10.87 11.23Test 31st extraction 50 12.70 12.48 8.15 7.70 12.44 12.71 12.00 11.682nd extraction 50 11.98 12.01 8.20 7.85 11.75 12.05 11.56 11.583rd extraction 50 12.28 12.30 8.50 8.04 11.90 11.53 11.29 11.64

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due to the alkaline nature of fly ash. The concentration ofPb, Fe and Mn in leachates depends on the test conditions.During the leaching studies, the resulting high pH in theleachates led to a limited removal of Pb and Fe from flyash, which was even less removal than the other metals(Cu, Co, Mn). The leachability of trace elements will de-pend more or less on the leachability of iron (Khanra and

others, 1998).Leaching of the metals decreased generally with increasingtemperature. In most cases, a direct link between extrac-tion and leachability could not be found. It is suggestedthat the degree of extraction does not exclusively deter-mine the leachability of all metals, rather, it is temperature.However, the applied leaching conditions did not lead tothe complete removal of soluble compounds due to a lowL/S ratio of only 5.Choi and others (2002) have suggested that the elements inthe ash particles were mainly associated with the surfaceand these surface-associated fractions might dominate theleachate chemistry at the early stages of fly-ash disposal in

contact with water. Some elements showed a rapid release.However, the elements incorporated within the interior ofthe fly ash dissolved in a slower mode compared with thereadily leachable surface-associated elements.This may explain why EC, Ca, Na, K and Fe leaching wasdifferent for un-leached (FA-1) and pre-leached (FA-2)samples. The fly ash from the ash pond was pre-leachedand exhibited lower EC and Ca values than FA-1. However,the calcium that is leached from the pre-leached fly ash(FA-2) is probably retained in the interior. This supports

the theory that these elements were surface associated andthey leached in the ash pond where they were weathered.In contrast, FA-2 exhibited higher K, Na and Fe valuesthan FA-1, which are thought to be associated within theinterior of the fly ash.Although both fly-ash samples showed no increase inconductivity, the dissolution of K and Na increased with

temperature. It is suggested that leaching with respect tothe ambient extraction principally affected the aluminiumsilicate fraction of the fly ash, mainly K and Na. However,a major impurity such as Ca and many trace elements,such as Cd, Co and Cu, did not increase considerably.Sulfates were leached in high amounts from the fly ash(Table 5). The difference between the leached SO4 con-centration of the FA-1 and FA-2 was not significant. Theinteraction of both fly ash samples with dolomitic lime-stone was slightly stronger than cherty limestone. It can beexpected that the leachable fraction of this ion can bewashed out completely into the ground water.The leached concentrations of some ions decreased when

the fly ash samples were in contact with typical rocksamples from beneath the ash pond. In these studies, FA-1mixed with cherty limestone samples exhibited lowerleaching of any constituents than FA-1 with dolomiticlimestone. In contrast, FA-2 mixed with dolomitic lime-stone showed lower concentrations of constituents thanFA-2 with cherty limestone. Therefore, the elements thatdo not or are that are weakly interact with rock willprobably be transported to deeper layers and ultimately tothe ground water. Some elements, such as Cd, Cu, Co and

894 Environmental Geology (2004) 46:890895

Table 5Concentrations of major and minor elements in leachates. FA-1+DLSFA-1 mixed with dolomitic limestone; FA-1+CLSFA-1 mixed with cherty

limestone; FA-2+DLS FA-2 mixed with dolomitic limestone; FA-2+CLS FA-2 mixed with cherty limestone

Element T FA-1 FA-2 DLS CLS FA-1+DLS

FA-1+CLS

FA-2 +DLS FA-2+CLS()

Ca 23 880 460 25.3 20.5 1340 905 243 30540 830 670 2.5 43 740 1020 350 43550 640 610 51.0 21 670 670 230 305

Mg 23 2.0 3.0 9.5 2.5 4.0 4.0 8.5 3.040 5.0 5.0 2.5 17 10 24 3.0 1450 0.8 1.3 13.5 1.2 0.2 0.9 3.1 0.4

Na 23 25 67 4.8 7.5 41 31 33 5240 9 85 6.3 8.0 11 10.5 26 2950 81 150 8.0 4.5 95 14 90 52

K 23 49 255 4.3 6.0 9.5 44 265 19040 32 205 11.5 2.3 36 17 205 178

50 105 255 9.5 4.5 95 30 265 110SO4 40 1016 904 35 48 704 920 504 62450 946 960 16 24 600 688 510 560

Pb 23 0.37 0.23 0.08 0.35 0.27 0.10 0.0840 0.30 0.30 0.08 0.08 0.32 0.28 0.19 0.1550 0.12 0.07 0.07 0.06 0.12 0.12 0.07 0.11

Mn 23 0.13 0.08 0.21 0.32 0.05 0.07 0.02 0.0540 0.05 0.09 0.30 0.76 0.07 0.09 0.11 0.1250 0.03 0.06 0.11 0.34 0.02 0.09 0.05 0.11

Co 23 0.06 0.03 0.03 0.06 0.06 0.11 0.03 0.0240 0.05 0.05 0.03 0.04 0.05 0.05 0.04 0.0250 0.05 0.02 0.03 0.05 0.04 0.05 0.04 0.03

Cu 23 0.01 0.01 0.03 0.01 0.01 0.01 0.0440 0.01 0.02 0.01 0.01 0.02 0.01 0.0350 0.01 0.02 0.02 0.02 0.02 0.04

Fe 50 0.80 1.35 0.16 0.38 0.38 0.22 0.61

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Cr, are not expected to leach from fly ash. In contrast,elements such as Na, K, Mg, Pb and Mn will be transportedto the ground water.

Conclusions

A major part of the water soluble compounds was removedin the fly ash pond. The results of batch tests, especiallywith pre-leached fly ash, showed that the release of ele-ments into the solution continues over long periods. TheEC values decreased after each extraction. In the both fly-ash samples Ca, Na, K, Mn, Fe, S and Pb showed maximumleachability, whereas, Cd, Mg, Cu, Cr, Zn and Co showedminimum leachability. The leaching of heavy metals waslow for the studied fly ash. The low metal leaching due tohigh pH resulted in low contamination of the leachate. Theleached concentration of Mg, Pb and Mn decreased whenthey were in contact with typical rock samples from be-

neath the ash pond. However, the elements (Na, K, Mg, Pb,Mn, SO4) that do not or that weakly interacted with theunderlying rock types will probably be transported to theground water.

References

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Choi SK, Lee S, Song YK, Moon HS (2002) Leaching character-istics of selected Korean fly ashes and its implications for thegroundwater composition near the ash mound. Fuel81:10801090

Iyer R (2002) The surface chemistry of leaching coal fly ash.J Hazard Material B93:321329

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Original article

leaching characteristics of fly ash

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