矿物改性污泥生物炭对土壤重金属浸出的影响

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

为研究凹凸棒石-污泥共热解生物炭对重金属污染土壤的淋溶性的影响,该文在350℃下将污泥、污泥和凹凸棒石混合热解制备2种生物炭,将2种不同生物炭施用于重金属污染土壤中进行钝化实验。钝化完成后土壤开展模拟酸雨土柱淋溶实验,研究重金属随着雨水淋溶的迁移规律,评价材料的钝化效果。结果表明:在淋溶过程中,重金属的累积淋失率呈现前期快速增长,后期持续缓慢增长的趋势,Cd、Zn、Cu、Cr、Ni 5种重金属的累计淋失率整体呈现对照>污泥生物炭>凹凸棒石-污泥共热解生物炭的趋势,共热解生物炭处理后,重金属的累积淋失率降低了11.13%~48.02%,各重金属的累积淋失率随时间的动力学方程拟合结果显示,Elovich修正方程与重金属的释放累积过程拟合相关性最好,R2为0.918~0.995,一级动力学方程的拟合相关性最差,说明重金属在土壤中的释放过程主要受到非均质表面的化学吸附影响,生物炭能够对土壤中的重金属起到较好的固定作用,从而降低重金属的淋失迁移性。凹凸棒石与污泥的共热解显示出了优于单一材料的重金属钝化效果。表明凹凸棒石-污泥共热解生物炭是一种潜在的土壤重金属钝化修复材料,可以有效降低重金属的环境风险。

In order to study the effect of attapulgite sludge co-pyrolysis biochar on the leaching ability of heavy metal contaminated 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 leaching 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.