铬渣污染土壤清洗剂筛选研究

以3种不同质地的铬渣污染土壤(A土，B土和C土)为研究对象，探讨了4种清洗剂对污染土壤中Cr的清洗效果，并采用欧盟BCR三步顺序提取法，研究了不同清洗剂对土壤中各形态Cr的去除效果. 结果表明:同一污染土壤上4种清洗剂对总Cr的去除效果差别不大；低浓度清洗剂对Cr(Ⅵ)和Cr(Ⅲ)的去除效果与去离子水相当；高浓度清洗剂效果优于低浓度清洗剂，且高浓度清洗剂洗出的总Cr主要以Cr(Ⅲ)为主. 同一清洗剂对3种污染土壤的清洗效果为C土>B土>A土. 去离子水主要去除酸可提取态Cr；EDTA-Na₂对酸可提取态和可还原态Cr去除效果较好；柠檬酸去除的是酸可提取态、可还原态和可氧化态Cr；而HCl对各形态Cr都有所去除. 因此，对于酸可提取态和可氧化态Cr含量较高的A土，柠檬酸是最佳清洗剂；而对于酸可提取态Cr占优势的B土和C土，去离子水是最佳清洗剂. 

Selection of Washing Agents for Remediation of Chromium Slag-Contaminated Soil

Three different types of chromium slag-contaminated soil were selected as test samples to investigate the Cr removal efficiencies of four washing agents. The removal efficiencies of the different washing agents on different fractions of chromium in soils were measured using the BCR method of EU. The main findings were as follows: the total Cr removal efficiencies in the same kind of soil by the four washing agents showed no significant differences. The removal efficiencies of hexavalent chromium and trivalent chromium by low concentration of EDTA-Na₂, citric acid and HCl were similar to that of deionized water, although washing agents with higher concentrations had better efficiencies than the same agents with lower concentrations. The primary Cr in the eluate of high concentration of wash chemicals was trivalent chromium. The removal ability of the same washing chemical on Cr in the three chromium slag-contaminated soils was in the sequence of Soil C > Soil B > Soil A. The main fraction of Cr removed by deionized water was exchangeable and weak acid extracted fraction, while EDTA-Na₂ could extract Cr with exchangeable and weak acid extracted fraction as well as reducible Cr fraction. In addition to these two fractions, citric acid could also extract oxidizable Cr fraction. HCl showed removal ability on all fractions. Citric acid was the best washing agent for Soil A with higher content of exchangeable and weak acid extracted Cr fraction and oxidizable Cr fraction, while deionized water was more suitable for Soil B and Soil C with higher content of exchangeable and weak acid extracted Cr fraction.