复合药剂对不同类型重金属污染土壤的固化修复

为了考察复合药剂对Pb、Hg、Cr、Cd、Zn、Cu和Ni污染土样的固化修复效果,以重污染企业用地、冶炼厂河道底泥和自配土壤为污染土样进行试验,试验中的普适复合药剂主要为含磷酸盐沉淀剂、黏土和水泥,视情况辅以无机还原助剂和有机络合助剂。在普适药剂(相对原土样的质量分数15%)、还原剂(5%)和有机助剂(2%)的组配下,处理后的重金属浸出质量浓度低于GB 18598—2001标准值。普适药剂对Pb、Cd、Zn、Cu、Ni的固化有效,磷酸盐是促成Pb固化的关键成分,黏土和水泥分别起到吸附固定和物理包封的作用。无机助剂中的还原/络合性成分和硫化物分别对Cr(VI)和Hg的固化有明显的促进作用。对于Pb、Cd、Zn、Cu复合污染土壤的修复,分析了重金属浸出质量浓度随普适药剂投加量变化的特征曲线,结果表明,Pb比Cu的曲线斜率更大,表明Pb的固化效率更高;Cd和Zn具有相似的曲线形状,推测二者具有类似的固化机理。

Immobilization and remediation of the heavy metal contaminated soils via the composite agents

The paper is to devote itself to the research on the immobilization and remediation mechanism of the heavy metal contamination in the soils via the composite agents.For the said purpose,we have chosen a series of composite agents to immobilize such heavy metal contaminants ofPb,Hg,Cr,Cd,Zn,Cu,and Ni in the soil samples from the nearby manufacturing spots,the river-course sediments and the synthetic land soils by choosing the normal components of the composite agents including soluble phosphate,calcium montmorillonite clay,and the fly-ash Portland cement.We have also added inorganic reductants including ferrous sulfate and calcium sulfide,and a thiol-based organic complexant,to the composite agents as adjuvants in case they are needed.The remediation process we have adopted included the pretreatment of soil samples,the addition of the composite agents with blending,and the incubation.Effective remediation of the soil samples were obtained,and the leaching concentrations of the heavy metal contaminants from the soil samples,too,in accordance with the Chinese national standard GB 18598-2001,can also be expected to achieve proper dosage of the composite agents (normal components,and/or inorganic adjuvants),so as to reduce the rate of the normal components content,inorganic adjuvants content,and organic adjuvants content to less than 15％,5％,and 2％ of their original soil weight,respectively.The normal components of the composite agents were found to be effective in immobilizing the contaminants of Pb,Cd,Zn,Cu,and Ni,for in this case,phosphate tends to play a key function in precipitating Pb,whereas clay and cement are vital for adsorbing and enveloping the aforementioned heavy metal residuals.What is more,the inorganic adjuvants may play their roles in the reduction and complexation of Cr and in the sulfidation of Hg.Therefore,we have made a proposal to remediate for the pollution with multiple heavy-metal composite agents,to relieve the characteristic curves of the leaching concentrations as the function of dosage,which tends to be instructive for optimizing the dosage and exploring the immobilization mechanism.Hence,it can be inferred from the slopes of the curves that Pb can be more effectively stabilized by the composite agents than can Cu.The similar curve forms for Cd and Zn may still imply that they are likely to give similar response to the process of immobilization.