铬污染场地土壤化学修复淋洗剂筛选及条件优化研究

Selection and condition optimization of soil chemical leaching agent for chromium contaminated sites

以石家庄市井陉县大通化工有限公司的铬污染场地土壤为研究对象,考察了6种淋洗剂对其中总铬和六价铬的淋洗去除效果,筛选出最佳淋洗剂;通过正交实验,确定其最佳淋洗条件;考察复合淋洗剂对总铬和六价铬的去除效果;最后考察最佳淋洗剂多次淋洗对总铬和六价铬的去除效果,确定最佳淋洗次数。结果表明:柠檬酸对总铬和六价铬的淋洗去除效果最好,其最佳淋洗条件为:浓度为0.50 mol/L,淋洗时间为4 h,p H值为2.0,固液比为1∶10,在此条件下,淋洗4次时,土壤中六价铬去除率达到100%,总铬残留量由2 630.0 mg/kg降到183.4 mg/kg,去除率达到93.03%,可满足《土壤环境质量标准》中二级标准(总铬浓度250 mg/kg)的场地修复要求。

The chromium contaminated soil in the Da Tong Chemical Corporation Ltd. was used as the research object, theremoval effects for hexavalent chromium and total chromium in chromium contaminated soil of six kinds of leaching agentwere studied to select the optimum leaching agent. Through orthogonal experiment, the optimum leaching conditions of theoptimum leaching agent were determined. And the removal effects for hexavalent chromium and total chromium inchromium contaminated soil of complex leaching agents were also investigated. Ultimately the optimum washing times ofthe optimum leaching agent were determined. The results show that citric acid has the highest leaching removal efficiencyof hexavalent chromium and total chromium,and the optimum leaching conditions of citric acid were 0.5 mol/L of citric acidconcentration, 4 h of washing time, 2.0 of pH value, and 1 ： 10 of the solid-liquid ratio under which the removal rate ofhexavalent chromium and total chromium reach 100% and 93.03% after 4 times washing, respectively. And the totalchromium concentration in soil reduces from 2 630 mg/kg to 183.4 mg/kg, which can meet the secondary standard of siteremediation requirements of ＂Soil Environmental Quality Standards＂.