改性矿物材料钝化污泥土地利用过程中重金属的淋溶特性

Leaching characteristics of heavy metals in the sewage sludge immobilized by modified mineral materials during land use process

为更好地评价污泥土地利用的环境安全性,研究了经改性矿物材料钝化处理的污泥重金属的淋溶释放特性,并利用一级动力学方程、修正Elovich方程、双常数速率方程和抛物线扩散方程进行拟合,探索其累积释放动力学。结果表明,污泥的加入显著提高了淋出液的pH和电导率,重金属(Cu、Cr、Zn)的浓度也明显增加。改性矿物材料的钝化处理能降低Cu、Cr的累积淋出量,对Zn的释放反而有活化作用。淋出液中Cu、Cr、Zn的最高质量浓度分别为1.49、0.081、1.45 mg/L,均低于《地下水质量标准》(GB/T 14848—2017)Ⅳ类限值。修正Elovich方程的拟合结果与重金属累积释放过程吻合度最高,Cu、Cr和Zn累积释放量拟合方程R^(2)分别为0.9751~0.9825、0.9118~0.9853和0.9314~0.9751,表明修正Elovich方程可较好模拟Cu、Cr、Zn的累积释放过程,可为调整钝化污泥添加量,减少重金属的淋出量提供理论依据。

In order to evaluate environmental safety of land use of sewage sludge,leaching characteristics of heavy metals in sewage sludge immobilized by modified mineral materials were studied.The first-order kinetic equation,modified Elovich equation,double-constant equation and parabola equation were used to explore cumulative release kinetics of heavy metals.The results showed that pH and electrical conductivity of the leachate were significantly increased with the addition of sewage sludge,and the concentrations of heavy metals(Cu,Cr and Zn)were also significantly increased.The immobilization by modified mineral materials reduced the cumulative release of Cu and Cr,while increased that of Zn.The highest concentrations of Cu,Cr and Zn in the leachates were 1.49,0.081 and 1.45 mg/L,respectively,which were all lower than the limit values of the ClassⅣin“Standard for groundwater quality”(GB/T 14848-2017).The fitting results of modified Elovich equation obtained the highest agreement with the cumulative leaching process.R^(2) of the fitting equation for cumulative release of Cu,Cr and Zn were 0.9751-0.9825,0.9118-0.9853 and 0.9314-0.9751,respectively,suggesting that the modified Elovich equation could simulate the cumulative release process of Cu,Cr and Zn,which could provide a theoretical basis for adjusting addition of immobilized sludge and reducing the leaching amount of heavy metals.