硫酸根离子强化零价铁去除Cr(Ⅵ)的试验研究

Enhanced chromium removal by zerovalent iron with the presence of sulfate anion

普通零价铁去除Cr(VI)的反应活性较低且Cr(VI)会导致零价铁较快钝化.通过连续流实验,研究了硫酸根离子提高零价铁去除水中Cr(Ⅵ)的可行性与反应机理.实验结果表明,在未加入硫酸根离子时,运行5.5h后柱子出水总铬及Cr(VI)已开始超出饮用水标准.而在加入1~3mmol/LSO_4^(2-)后,出水总铬及Cr(VI)持续降低,并最终降至饮用水水质标准以下且稳定运行长达240h以上.XPS分析结果表明,还原作用是零价铁除Cr(Ⅵ)的主要机理,硫酸根离子加速了零价铁的腐蚀进而促进了Cr(VI)的去除.

Generally,zerovalent iron(ZVI)is considered to have low intrinsic reactivity toward Cr(VI)removal,and on the other hand,Cr(VI)could also cause surface passivation of ZVI.To address this issue,sulfate was introduced into a ZVI column system and its effect on ZVI performance and the corresponding mechanisms was investigated in depth.According to the results of this work,without the presence of SO4 2-,little Cr(VI)could be removed by ZVI column,and the effluent concentrations of Cr(VI)and total Cr would quickly exceed the maximum contaminant limitation of drinking water.While,upon the addition of 1~3mmol/L SO4 2-,both the concentrations of Cr(VI)and total Cr deceased rapidly and met the drinking water standards.Furthermore,this good ZVI performance kept unchanged during the following running time(~240h)in this work,and more longer duration could be expected.The XPS analysis of the reacted ZVI samples indicated Cr(VI)could be reduced to Cr(III),implying Cr(VI)reduction was its main removal mechanism by ZVI.With respect to the role of SO4 2-,it was believed to be able to accelerate ZVI corrosion and thus enhance the Cr(VI)reduction.