电化学联合H_2O_2氧化淋洗修复典型化工厂遗留地铬污染土壤

Electrochemical and H_2O_2 oxidation with leaching to remove chromium from contaminated soil in a typical chemical deserted plant

选取的济南某化工厂遗留地土壤主体为褐土类,年均降水量在685 mm左右,铬污染场地面积约34万m2,土量约105.4万m3。为筛选出最佳氧化条件,研究了4个厂区铬污染土壤的理化性质和污染状况,探讨了通电时间、通电电压、氧化剂质量分数、土液比和pH对Cr(Ⅲ)转化成Cr(Ⅵ)比率和总铬去除率的影响。结果表明:4个厂区土壤酸碱性不同;万吨铬盐生产车间和北部厂区有机质含量较高,其他2个厂区较低;总铬含量在863.3~14 403.8 mg·kg-1之间,均严重超出国家标准;铬污染活性指数I在0.007 8~0.292 9之间,铬污染活性指数均较低;最佳通电时间选择为20 min,通电电压为10 V,H2O2质量分数为1%,土液比为2:3,pH为8。经修复,4个厂区剩余总铬浓度分别为363.68、258.09、6 938.31和495.45 mg·kg-1,最大总铬去除率分别可达到87.59%、73.95%、51.83%和42.61%,其中万吨铬盐生产车间土壤中总铬残留值可达到国家土壤环境质量二级标准(GB 15618-2008)修订稿中的居住用地标准,铬盐生产车间和北部厂区可达到修订稿中的商业用地标准。

A typical chemical deserted plant in Jinan was selected in this paper, and the main soil type is cinnamon,the annual precipitation here is about 685 mm, the area of chromium contaminated site is about 340 000 m2, and the volume of soil is about 1 054 000 m3. In order to screen out the optimum oxidation conditions, the physicochemical properties and pollution status of chromium contaminated soil in four sites has been studied, and the effect of power time, electric voltage, mass fraction of H_2O_2, solid to liquid mass ratio and pH on the transformation of Cr（Ⅲ） into Cr（Ⅵ） and the removal rate of total Cr have been discussed. The results showed that the acidity and alkalinity of soil in the four sites was different. The organic matter content of ten thousand tons chromic salt workshop and north section of the plant was higher than that of the other two sites. The content of total Cr was in the range from 863.3 to14 403.8 mg ·kg-1, which exceed the national standard seriously. The chromium pollution activity index I was low which were between 0.007 8 and 0.292 9. The optimal conditions were a power time of 20 min, electric voltage of10 V, mass fraction of H2 O2 of 1%, solid to liquid mass ratio of 2：3 and a pH of 8. After remediation, the remaining concentration of total Cr in the four sites was 363.68, 258.09, 6 938.31 and 495.45 mg·kg-1, respectively, and the maximum removal rate reached 87.59%, 73.95%, 51.83% and 42.61%. The total Cr residue in the soil of ten thousand tons chromic salt workshop reached the standard of residential land in the revised version of the National Soil Environmental Quality Class II Standard（GB 15618-2008）. At the same time, chromic salt workshop and north section of the plant reached the revised version of the commercial land standards.