Effect of Mineral Modified Sludge Biochar on Leaching of Heavy Metals in Soil

TAO Ling; HAN Xuexin; REN Hanru; WANG Miao; SUN Xinni; WANG Ruo'an; REN Jun

doi:10.19672/j.cnki.1003-6504.0782.23.338

Abstract：In order to study the effect of attapulgite sludge co-pyrolysis biochar on the leaching ability of heavy metal con-taminated soil,two kinds of biochar were prepared by pyrolysis of sludge,sludge and attapulgite at 350 ℃,and two different biochar were applied to heavy metal contaminated soil for passivation experiments.After passivation,a simulated acid rain soil column leaching experiment was conducted on the soil to study the migration law of heavy metals with rainwater leaching and evaluate the passivation effect of the material.The results showed that during the leaching process,the cumulative leach-ing rate of heavy metals showed a trend of rapid growth in the early stage and continuous slow growth in the later stage.The cumulative leaching rate of five heavy metals,Cd,Zn,Cu,Cr and Ni,showed a trend of control＞sludge biochar＞attapulgite sludge co-pyrolysis biochar.After the treatment of co-pyrolysis biochar,the cumulative leaching rate of heavy metals decreased by 11.13％to 48.02％.The fitting results of the kinetic equation of the cumulative leaching rate of each heavy metal with time show that the Elovich modified equation has the best fitting correlation with the release and accumulation process of heavy metals,with R2 as 0.918～0.995,and the fitting correlation of the first-order kinetic equation is the worst,indicating that the release process of heavy metals in soil is mainly affected by the chemical adsorption of heterogeneous surfaces,and biochar can play a good role in fixing heavy metals in soil,thus reducing the leaching and migration of heavy metals.The co-pyrolysis of attapulgite and sludge showed a superior heavy metal passivation effect compared to a single material.It shows that attapulgite sludge co-pyrolysis biochar is a potential material for heavy metal passivation and remediation in soil,which can effectively reduce the environmental risk of heavy metals.