Arsenic leaching characteristics and correlations with iron,manganese in fly ash from coal-fired power plants

Fly ash samples from three different coal-fired power plants were divided into sub-samples according to particle size(0—2.5 μm,2.5—10 μm,10—60 μm,60—100 μm,100—200 μm,200 μm).Total concentrations of arsenic in the samples were determined by atomic fluorescence spectrometry.It was found that the total arsenic in fly ash was negatively correlated with particle size.Arsenic in the fly ash samples with different particle size(200 μm,100—200 μm,60 μm) was extracted respectively by deionized water(H2O),acetic acid(CH3COOH),diluted hydrochloric acid(HCl),hydroxylammonium chloride(NH2OH · HCl),oxalate-ammonium oxalate solution(C2H2O4-(NH4)2C2O4),and sodium citrate-sodium hydrosulfite solution(Na3C6H5O7-Na2S2O4).The results revealed that water soluble arsenic accounted for 5.93%—18.7% of total arsenic.Carbonate arsenic extracted by acetic acid accounted for 6.78%—16.91% of total arsenic.Arsenic concentrations extracted by 0.25 mol · L-1 HCl,0.6 mol · L-1 HCl,NH2OH · HCl,C2H2O4-(NH4)2C2O4 accounted for 18.1%—56.5%,28.2%—74.8%,43.4%—80.8% and 39.1%—66.7% of the total amount,respectively.NH2OH · HCl was the most effective reagent for arsenic leaching from fly ash in our experiment.The concentration of extractable arsenic had significant linear correlation with the concentration of Fe and Mn in fly ash.