重金属-多氯联苯复合污染土壤同步洗脱

电子垃圾拆解区土壤具有重金属与有机物复合污染的特性,尤其以Cu、Pb、Cd和多氯联苯(PCBs)的复合污染较为突出。为了同步脱除土壤中重金属与PCBs,选用增溶物质:Tween 80、TX-100、SDBS、β-环糊精与螯合剂柠檬酸依次组合进行复合污染土壤淋洗实验,应用批量平衡震荡法研究它们对重金属(Cu、Pb、Cd)与PCBs(Aroclor 1254)的洗脱效果。通过比较洗脱效果、环境友好性等方面,得出非离子表面活性剂Tween 80与天然螯合剂柠檬酸2种淋洗剂复合最佳;进一步研究两者的淋洗先后顺序、浓度配比、洗脱时间及淋洗剂pH对污染土壤洗脱效果的影响,结果表明,在Tween 80和柠檬酸均为10 g/L、pH=6、淋洗时间12 h时淋洗效果达到最佳,对Cu、Pb、Cd及PCBs的洗脱率分别达到98.77%、55.92%、66.82%和58.01%。因此,利用Tween80和柠檬酸组合可同时有效去除土壤重金属和PCBs,是复合污染土壤淋洗修复的有效淋洗剂。

Simultaneous desorption of heavy metals and PCBs by composite eluents from contaminated soils

Soil of electronic waste (e-waste) dismantling sites is often characteristic of combined contamination of organic chemicals and heavy metals, in which the Cu, Pb, Cd and polychlorinated biphenyl (PCBs) multiple-contamination is a prominent case. This study applied a novel combination of surfactants (i.e., TW-80, TX-100, SDBS, β-cyclodextrins) and citric acid as composite eluents in batch experiment to investigate the effect of simultaneous desorption of heavy metals (Cu, Pb, Cd) and PCBs (Aroclor 1254) from combined contaminated soils. Taking three factors into account, namely flushing efficiency, eluent volume and environmental friendliness, non-ionic surfactant polyoxyethylene sorbitan monooleate (Tween 80) and biodegradable chelant citric acid were chosen as the two preferable flushing agents for PCBs and heavy metals contaminated soil. Moreover, the effects of leaching method, ratio of eluents, flushing time, elution sequence and the pH of these two eluents on the desorption efficiency were studied. The results show that the maximal desorption rates of Cu, Pb, Cd and PCBs can achieve 98.77% , 55.92%, 66.82% and 58.01%, respectively, by addition of 10 mg/L citric acid and 10 mg/L Tween 80 under the conditions of pH=6 and 12 h of leaching time.