电动力和铁PRB技术联合修复铬(Ⅵ)污染土壤

考察了电动力学方法对模拟铬(Ⅵ)污染土壤以及天津市原同生化工厂遗留下的铬渣山周边土壤的修复效果,并将该技术与铁可渗透反应格栅(permeable reactive barrier,PRB)技术联用,找出了较好的联用方式,与单一电动修复进行了对比.研究表明,电动力学技术能有效地修复被铬(Ⅵ)污染的土壤,模拟污染土壤铬(Ⅵ)的去除率达98%～100%,总铬去除率在阳极室附近为80%左右,而阴极室附近则为90%以上,恢复到土壤背景值;铬(Ⅵ)去除的同时伴随着铬(Ⅵ)向铬(Ⅲ)的转化,修复结束时土壤中残留的铬90%以上为铬(Ⅲ);污染极其严重的铬渣山下土,由于含约28%的铬(Ⅲ),修复结束时铬(Ⅵ)的去除率达98%以上,而总铬去除率仅为75%～77%;阳极室附近土壤pH降低而阴极室附近土壤pH升高,处于两极中间位置的pH变化不大.电动力学与铁PRB原位联用方式能充分地利用这2种技术的优点,修复后,土壤任意位置的总铬去除率接近90%,阳极室附近尤为好于单一电动修复,对土壤pH的影响也较小.

Remediation of Chromate Contaminated Soils by Combined Technology of Electrokinetic and Iron PRB

Remediation efficiency on artificial chromate Cr (VI)] contaminated soil and a field Cr (VI) contaminated soil around industrial Cr residue (Tianjin Tongsheng Chemical and Industrial Factory) by using electrokinetic method was studied. Moreover, the electrokinetic method was combined with iron permeable reactive barrier (PRB) and a better combination mode was found. The remediation efficiency of the combined method was compared with electrokinetic method. The results showed that Cr (VI) contaminated soil can be remedied effectively by electrokinetic method. For artificial contaminated soil, the removal ratio of Cr (VI) reached 98%-100%, while the total Cr was removed about 80% near the anode, and more than 90% near the cathode, where the content of Cr came back to soil background. The reduction of Cr (VI) to Cr (III) occurred during the soil remediation, and more than 90% of the residual Cr was Cr (III) at the end of remediation. More than 98% Cr (VI) were removed, whereas only 75%-77% of total Cr were removed from the heavily contaminated field soil as the soil contained 28% Cr (III) initially. Soil pH increased near the cathode and decreased near the anode, while the change of soil pH was insignificant in the middle. In situ combination mode of electrokinetic and PRB is a better method that could take the full advantages of the two technologies. The removal efficiency of total Cr was about 90% at the end of the remediation, which is better than electrokinetic method especially near the anode, and had less effect on soil pH.