土壤粒径和参数对重金属淋洗的影响分析

Study on the influence of size distribution and process parameters on soil washing

目的以上海地区黏性重金属污染土为研究对象,分析以上海为代表的长江三角洲地区黏性土壤的粒径分布以及不同粒径范围土壤淋洗效率的特点。方法采集了上海地区大型土壤修复项目的重金属污染土,以2、0.9、0.2、0.075 mm为节点,确定粒径分布。进一步细化粒径范围,并对不同粒径范围内的污染土进行相同条件下的淋洗实验,对比不同粒径范围内土壤的淋洗效果,此外考察工艺参数液固比、淋洗时间、淋洗次数对淋洗效率的影响。结果研究得到,该黏性污染土的粒径主要分布在0.075 mm以下(超过50%)。随着粒径的减小,淋洗效率呈逐渐降低趋势。其中,Pb在粒径>2 mm和0.2~0.45 mm内的土壤中去除率最大。随着液固比、淋洗时间以及淋洗次数的增大,淋洗效率逐渐升高。结论土壤淋洗修复项目中淋洗小试的研究应重点考察0.075 mm以下粒径土壤的淋洗效果。工艺参数的优选结果为,液固比为4:1,淋洗时间为1~2 h,淋洗次数为1次。

Based on clay soil in Shanghai,this study analyzed the soil particle size distribution and the influence of the size on washing efficiency.Heavy metal polluted soil was sampled from large soil remediation project and size distribution analysis had been carried out(taking 2,0.9,0.2,0.075 mm as nodes).Soil washing efficiencies were compared in different particle size ranges under the same washing conditions.Besides,the effects of process parameters including liquid-solid ratio,washing time and washing frequency on washing efficiency had been discussed.Results proved that particles below 0.075 mm were the main part of soil and the efficiency gradually decreased as the particle size decreased.For Pb,the removal rate was maximum for soil with the particle size>2 mm and in 0.2-0.45 mm.The efficiency increased with the increase of those process parameters.In future,the washing test should focus on the washing performance of the soil below 0.075 mm,and the optimal values of liquid-solid ratio,washing time and washing times were 4 ml/g,1-2 h,and once.