可渗透反应复合电极法对土壤重金属的电动去除

将零价铁(Fe0)、沸石等活性材料附着在电极上形成可渗透反应层并构成可渗透反应复合电极,采用不同的复合电极对Cd2+、Ni 2+、Pb2+和Cu2+等4种阳离子型重金属污染土壤进行了电动力学修复。研究了不同可渗透反应复合电极对土壤pH的控制效果以及对重金属的去除作用,分析了迁移到复合电极中的重金属形态变化。结果表明,复合电极中添加酸、碱性沸石并适时更换,可有效中和、截留阴阳极电解产生的OH-和H+,避免或减缓土壤酸碱迁移带的形成,防止重金属离子的过早沉淀及土壤过度酸化,极大提高了重金属的去除率。复合电极中Fe0可将迁移进来的重金属离子进行还原稳定,实现重金属污染物的捕获与固定,与迁移到沸石复合电极中的4种重金属不稳定态相比,"Fe0+沸石"复合电极中重金属不稳定态分别下降了61.4、60.5、61.4、57.1百分点。结果还显示,阴极采用"Fe0+沸石"复合电极并适时进行更换,施加1.5V/cm的直流电压修复10d后,土壤中Cd、Ni、Pb、Cu的总去除率分别为44.5%、41.5%、33.5%和36.7%,且进一步延长修复时间和持续更换电极可获得更为理想的修复效果。

Electrokinetic removal of heavy metals in contaminated soil using permeable reactive composite electrodes

The permeable reactive composite electrodes was established by adhering reactive materials such as zero-valent iron(Fe0) and zeolite on the electrodes to form a permeable reactive layer.The composite electrodes were used for electrokinetic remediation of soil contaminated by Cd2+,Ni2+,Pb2+ and Cu2+.The effects of different composite electrodes on pH control and heavy metal removal efficiency were studied,and speciation changes of heavy metals moved onto the electrodes were analyzed.The results showed that with acidic/alkaline zeolite added and timely renewed,the composite electrodes can effectively neutralize and capture H+ and OH-produced from electrolysis of the anode and cathode,avoiding or delaying the formation of acidic/alkaline band in soil,preventing untimely precipitation of heavy metal ions and over-acidification of soil,and thus significantly improving the heavy metal removal efficiency.The Fe0 in the composite electrodes can reduce and stabilize the migrated heavy metal ions,and thereby realize the capture and immobilization of the pollutants.The unstable forms of the 4 above-mentioned heavy metals in "Fe0+zeolite" composite electrodes decreased by 61.4%,60.5%,61.4% and 57.1%,respectively,compared with those in zeolite composite electrodes.The results also showed that,for a "Fe0 + zeolite" permeable composite electrode in the cathode with timely renewal,after 10-day remediation with a direct current voltage of 1.5 V/cm,the total removal rate of Cd,Ni,Pb and Cu were 44.5%,41.5%,33.5% and 36.7%,respectively.Further prolonging remediation duration and constantly renewing electrodes can produce better remediation result.