FeCl_3-柠檬酸复合淋洗剂去除土壤中Pb、Cd机理研究

Washing mechanism of removing Pb and Cd from the contaminated soil with the FeCl_3-organic acid

以FeCl_3-柠檬酸复合淋洗剂为淋洗剂,测定不同浓度淋洗剂作用时土壤pH、Eh值变化,进行FeCl_3-柠檬酸复合淋洗剂对土壤中Pb和Cd的淋洗动力学实验,采用BCR连续提取法对淋洗前后土壤中Pb、Cd赋存形态进行分析。结果表明,随着淋洗剂浓度的增大,土壤pH值下降,Eh值增大,且FeCl_3-柠檬酸复合淋洗剂作用时土壤pH和Eh变化较FeCl_3和柠檬酸单一作用时更明显,0.2 mol/L FeCl_3-柠檬酸为适宜淋洗剂;Pb、Cd的淋洗平衡时间为120 min,过程分为快速淋洗阶段、慢速淋洗阶段和淋洗平衡阶段,Pb、Cd的平衡淋洗量分别为0.109 mg/g和0.015 mg/g,分别占土壤中其含量的95.98%和97.98%;淋洗后,土壤中Pb和Cd各形态含量均有所下降,Pb的酸可提取态、可还原态、可氧化态和残渣态分别降低82.97%,62.04%,55.29%和22.12%,而Cd的4种形态分别降低96.7%,95.03%,29.59%和17.71%。

FeCl3-citric acid in compound leaching agent as eluent,the pH and Eh values of samples were measured in different concentrations of leaching agent,the leaching kinetics experiment were did,the speciations of Pb and Cd were analyzed with BCR sequential extraction method before and after leaching.The results showed that with the increase of eluent concentration,soil pH value decreased, Eh value increased,and the pH and Eh of soil were more obvious of FeCl3-citric acid than those of FeCl 3 or citric acid,the 0.2 mol/L FeCl3-citric acid was appropriate eluent;The leaching balance time was 120 min,the process of Pb and Cd can be divided into rapid elution stage,slow elution stage and leaching equilibrium stage.The equilibrium leaching amount of Pb and Cd is 0.109 mg/g and 0.015 mg/g,accounting for 95.98% and 97.98% of the content in soil respectively;After leaching various forms of Pb and Cd in soil were decreased than that before leaching,acid extractable Pb,reducible Pb,oxidizable Pb and residual Pb were decreased by 82.97%,62.04%,55.29% and 22.12%,and the four forms of Cd were decreased by 96.7%,95.03%,29.59% and 17.71%.