Remediation of lead polluted soil by active silicate material prepared from coal fly ash

To improve the effect of coal fly ash on the remediation of heavy metal polluted soils, the active silicate material (ASM) was prepared by coal fly ash and the remediation of lead polluted soils by ASM was investigated in this study. To study the reaction mechanism between ASM and Pb(II) in soil, the Pb(II) adsorption by ASM was investigated by a series of batch experiments. The result shows that the maximum adsorption capacity of ASM was 300.62 mg g^-1 according to the Langmuir isotherm model. The average adsorption energy obtained from the D-K model revealed that the adsorption process of ASM is the ion-exchange process. To apply the ASM to the remediation of lead polluted soils, the soil stabilization experiment and pot experiment were carried out. The results reveal that ASM can reduce the mobility and bioavailability of lead in the soils by transforming the lead from exchangeable fraction, carbonate fraction and reducible fraction to oxidizable fraction and residual fraction. Moreover, ASM can improve the growth of pakchoi by promoting the production of chlorophyll. Furthermore, ASM can reduce the Pb accumulation of pakchoi by inhibiting the absorption of lead in the roots. It is anticipated that this study can provide a novel active silicate material for the application of coal fly ash in heavy metal pollution treatment.