不同异位修复工艺对高浓度铬渣污染土壤中Cr的去除特性

Characteristics of chromium removing using different ex-situ remediations in soil seriously contaminated by chromite ore processing residue

以我国某铬盐厂的两种不同污染特性铬渣污染土壤(A土和B土)为研究对象,探讨了三种异位修复工艺(淋洗、稳定化、湿法解毒)去除铬渣污染土壤中总Cr和Cr(Ⅵ)的效果,并采用改进BCR顺序提取法分析了不同修复工艺对土壤中各形态Cr的去除效果。实验结果表明,三种异位修复工艺对铬污染土壤中Cr(Ⅵ)的去除效果为湿法解毒>稳定化>淋洗,湿法解毒工艺对A土、B土中Cr(Ⅵ)的去除率分别高达83.26%、92.94%;对铬污染土壤总铬去除效果最佳的是异位淋洗工艺,异位淋洗工艺对A土、B土总铬消减分别达54.87%、80.16%。异位淋洗工艺实现了对水溶态Cr(Ⅵ)、酸溶态Cr(Ⅵ)的泥水分离,是总铬消减的主要原因;稳定化工艺和湿法解毒工艺降低了土壤p H,促进了水溶态Cr、酸溶态Cr及可还原态Cr向可氧化态Cr的转化,因此土中总Cr并未发生显著消减。高浓度铬渣污染土壤经三种异位修复工艺处理后,A土Cr(Ⅵ)仍然残留736.6 mg·kg^(-1),B土Cr(Ⅵ)仍然残留245.47 mg·kg^(-1),酸溶态Cr的残留是导致三种工艺修复Cr(Ⅵ)效果受限的主要原因。

Two different types of chromite ore processing residue（COPR） contaminated soil were selected from one of chromate plants in China as research objects. The removal efficiencies of total chromium and hexavalent chromium were investigated by using three ex-situ remediation technologies which were soil washing, ex-situstabilization and wet-process detoxication. The removal mechanisms of various forms of chromium by three kinds of remediation technologies were studied using the modified BCR method. The results show that wet-process detoxication technology was favor in Cr（Ⅵ） reducing. Cr（Ⅵ） removal rate of the wet-process detoxication technology for soil A and soil B were up to 83.26%, 92.94%, respectively. The Cr（Ⅵ） removal rate of wet-process detoxication technology was higher than soil washing and ex-situ stabilization. For total chromium removal rate, soil washing was the best remediation technology. The total Cr removal rate of the soil washing technology for soil A and soil B were up to 54.87%, 80.16%, respectively. Separating soluble Cr（Ⅵ） and acid soluble Cr（Ⅵ） from soil were the main reasons for the reduction of total chromium. The total Cr remove was not significant for ex-situ stabilization and wet-process detoxication technology. Because, acid conditions which was reduced by these two remediation technologies, promote soluble Cr, acid soluble Cr and reducible Cr transformed into oxidizable Cr and the total amount Cr did not change. After remediation, the Cr（Ⅵ） residual of COPR contaminated soil still maintains a high level（the Cr（Ⅵ） residual content of soil A was 736.6 mg·kg（-1）, the Cr（Ⅵ） residual content of soil B was 245.47 mg·kg（-1））. The main reason was the acid soluble Cr residue.