环境友好型淋洗剂对重金属污染土壤的修复效果

以广西某废弃铅锌冶炼企业重金属复合污染土壤为对象，采用土柱淋洗的方法，分别将自制的茶皂素、柠檬酸和EDTA 3种淋洗剂进行复合淋洗，并对复合淋洗的最佳配比、淋洗剂添加方式和淋洗时间进行研究，得到对环境友好且淋洗效果好的复合淋洗剂。最后，对淋洗前后土壤中Cu、Pb和Zn的赋存形态进行研究，探讨淋洗机理。研究结果表明，茶皂素和柠檬酸复合时对重金属Cu、Pb、Zn的去除率分别达到了77.00%、52.09%和58.66%，综合考虑淋洗效率以及经济环保等因素，选择将茶皂素和柠檬酸复合进行淋洗。复合淋洗实验结果表明，柠檬酸和茶皂素体积比为3：1复合方式淋洗30 h，淋洗效果最佳，对重金属Cu、Pb和Zn的去除率分别达到82.77%、65.49%和78.12%。茶皂素和柠檬酸复合淋洗能有效的去除土壤中酸可提取态和有机结合态的重金属，氧化物结合态的Pb和Zn也有较大程度的降低，同时还发现，茶皂素和柠檬酸共同作用对残余态的Pb去除效果也较好，可达到50%以上。从茶籽饼中提取茶皂素与天然有机酸柠檬酸复合淋洗，用于修复污染面积小、污染浓度高且污染比较集中的重金属污染土壤，效果好且对环境友好。

Remediation of heavy metals contaminated soil by washing with environmentally friendly washing liquids

To assess the influence of soil washing with homemade tea saponin, citric acid and ethylene diamine tetraacetic acid (EDTA) on the removal of heavy metals,soils of lead and zinc smelter in Guangxi, all polluted by heavy metals of Cu,Pb,Zn were washed in a column. The volume ratio of washing reagents,the adding order of washing reagents and the washing time were chosen to research the optimum washing conditions.Then,variations of heavy metals in different forms before and after washing were discussed.Results showed that the mixed solution of homemade tea saponin and citric acid can remove 77.00% of Cu,52.09% of Pb,58.66% of Zn.The optimum washing conditions were: 3/4 citric acid,followed by 1/4 tea saponin,washing 30 h,the maximal desorption of Cu, Pb and Zn were achieved 82.77%,65.49%,78.12%, respectively. The mixed solution of homemade tea saponin and citric acid were very effective in removing the acid extractable, organic-bound states of heavy metals and oxide-bound states of Pb and Zn from the contaminated soils. At the same time,we also found that the mixed solution of tea saponin and citric acid can wash out the residual state of Pb effectively. Extracting tea saponin from tea seed cake, as a natural surface active agent mixed with natural organic acid citric acid to leaching pollution soils,is environmentally friendly and efficient.