Fe^(0)去除地下水Cr(Ⅵ)过程中的钝化作用及电化学解钝参数优化

Passivation effect of Fe^(0) in the removal of Cr(Ⅵ)from groundwater and the optimization of electrochemical depassivation parameters

零价铁(Fe^(0))广泛用于Cr(Ⅵ)污染地下水的修复,但存在Fe^(0)钝化降低修复效率的问题。首先使用Fe^(0)去除地下水中的Cr(Ⅵ)并制备不同钝化程度的钝化铁屑,然后采用电化学方法对钝化铁屑进行解钝,并通过单因素试验和正交试验研究电极设置、电解电压、电解时间及电极距对解钝效果的影响,同时对解钝溶液和解钝前后的铁屑及解钝过程中产生的沉淀进行分析。结果表明:以钝化铁屑作阳极时解钝效果最佳;解钝效果随电解电压增大先上升后降低,随电极距增大而降低,随电解时间增加而上升,3个因素对解钝效果的影响依次为电解时间>电解电压>电极距;X射线衍射仪、扫描电子显微镜和能谱分析表明,钝化铁屑在电化学作用下因表面沉淀脱落使得其活性得到有效恢复;钝化铁屑解钝的最佳条件(以钝化铁屑作阳极,电解电压为10 V,电解时间为60 min,电极距为2 cm)下,解钝后铁屑对Cr(Ⅵ)的去除率可恢复至原来的90%以上;解钝过程中不会促使Cr(Ⅲ)沉淀溶解,但会增加溶液中Fe的浓度。上述研究成果对提高Fe^(0)修复Cr(Ⅵ)污染地下水的修复效果及材料使用率具有参考作用。

Zero-valent iron(Fe^(0))is widely used in the remediation of groundwater polluted by Cr(Ⅵ).However,there is a problem that passivation reduces the remediation efficiency.First of all,Fe^(0) was used to remove Cr(Ⅵ)in groundwater,and passivated iron filings with different passivation degrees were prepared.Subsequently,the electrochemical method was used to deactivate the passivated iron filings,and the effects of electrode setting,electrolysis voltage,electrolysis time and electrode distance on the depassivation effect were studied by single factor test and orthogonal test.Meanwhile,the depassivation solution and the iron filings before and after depassivation as well as the precipitate produced during the depassivation process were analyzed.The results showed that the depassivation effect was the best when passivated iron filings were used as anode.The depassivation effect first increased and then decreased with the increase of electrolysis voltage,decreased with the increase of electrode distance,and increased with the increase of electrolysis time.The influence of three factors on the depassivation effect from high to low was as follows:electrolysis time>electrolysis voltage>electrode distance.The results of the X-ray diffractometer,scanning electron microscope and energy dispersive spectroscopy analysis showed that the activity of passivated iron filings could be recovered effectively due to surface precipitation shedding under electrochemical action.The optimum conditions for depassivation of passivated iron filings were as follows:passivated iron filings for anode,electrolysis voltage=10 V,electrolysis time=60 min,electrode distance=2 cm.Under these conditions,the removal rate of Cr(Ⅵ)by iron filings after depassivation could be restored to more than 90%of the original;Cr(Ⅲ)precipitate could not be dissolved,but the concentration of Fe in the solution could be increased during depassivation process.These research results could provide a useful reference for improving the remediation effect and material utilization rate of Cr(Ⅵ)polluted groundwater by Fe^(0).