不同pH调控方法对电助淋洗去除农田土壤Cd的影响

摘要

Leaching is a simple and efficient way of soil restoration, but the effect on soil of low permeability is unsatisfactory.In view of this, electrokinetic remediation was taken to promote the efficiency of leaching of cadmium-contaminated paddy soils , and the influence of electrolyte pH control on the pH value of soil and the removal of heavy metal Cd was discussed in this paper.Results showed that when voltage gradient is 1.5 V/cm, working for five days intermittently and 8 hours every day continuously, the removal efficiency of Cd in electrokinetic leaching(Ex1) reached 50.87%, 10% higher than test Ex0 which was only simple leaching;electrokinetic remediation could strengthen the flow of pore water in the soil, accelerate the migration of Cd2+ in pore water of soil, improve the removal rate of Cd, and effectively promote the leaching effect of Cd in farmland soil.Compared with test Ex1 in which electrolyte pH was uncontrolled, tests Ex2, Ex3, and Ex4 could control the soil''s pH value and improve the mobility efficiency of Cd2+ in pore water of soil.Therefore, when factors such as site operation were considered, polarity switching technology would be a good choice in controlling soil''s pH value.%淋洗是修复土壤的一种简单高效的方法,但是对于渗透性系数低的土壤效果不佳.因此,采用电动修复技术强化农田重金属Cd的淋洗(简称电助淋洗),探讨了不同电解液pH控制方法对电助淋洗去除重金属Cd的影响.研究结果表明:在电压梯度为1.5 V/cm、间歇通电5 d,每天连续通电8 h条件下,电助淋洗试验Ex1中重金属Cd的去除率为50.87%,比单一淋洗试验组Ex0中重金属Cd的去除率高10%;电动修复技术能强化土壤中孔隙水的流动,加速重金属离子的迁出,提高重金属去除率,有效促进农田土壤重金属Cd的淋洗效果.对比不控制电解液pH的试验Ex1和控制电解液pH的试验Ex2,Ex3,Ex4可知,控制电解液pH能控制土壤pH值,提高重金属Cd的迁移率.综合考虑现场操作等因素,建议采用电极极性切换控制土壤pH值.