阴极pH控制对电动去除电镀污泥重金属的影响

Effect of pH control at cathode on the electrokinetic removal of heavy metals from the electroplating sludge

采用电动修复装置,选用电镀污泥作为试验材料,试验设计了3个不同pH值的阴极缓冲液处理,施加直流电压32 V,运行7 d,研究了不同pH值阴极缓冲液对电镀污泥电动修复过程的影响.结果表明,阴极缓冲液pH值的变化,影响了电动过程中电流大小,pH较低时,电流较大;pH较高时,电流较小.电动修复后,各处理电镀污泥重金属的电动修复效果不同,其中,pH值控制为3时,Ni、Cu、Zn和Cr的去除率分别达到70%、59%、30%和29%,而Pb的去除率在pH值控制为5时去除率达46%.各处理截面重金属浓度较实验前都有不同程度的降低,其中Cu、Pb和Ni在不同污泥截面分布较均匀,而Cr和Zn在各截面分布波动较大.电动修复对各种形态的重金属都有不同程度的去除,对可交换态和铁锰氧化物态的去除效果较差,对碳酸盐结合态和残渣态有明显去除,有机硫化物态去除效果一般.

The effect of pH value of cathode buffer solution on electrokinetic（EK） remediation efficiency of heavy metals in the electroplating sludge was investigated.In these EK experiments,electrokinetic remediation apparatus was adopted,and the sludge collected from a electroplate factory and seriously polluted by Zn,Cu,Pb,Cr and Ni was used as materials.EK experiments were performed through cathode rinsing using cathode buffer solution with three different pH values and operated for 7 d at 32 V direct current power.The results showed that the pH value of cathode buffer solution changed the current markedly in the EK processes,the lower the pH value,the higher the current.After EK remediation,all experiment systems had different remediation efficiency.The best remediation effect of Ni,Cu,Zn and Cr was observed at pH 3,and the removal rates of Ni,Cu,Zn and Cr were 70%,59%,30% and 29% respectively,but the best remediation effect of Pb was observed at pH 5,and the removal rate of Pb was 46%.In addition,the concentrations of Zn,Cu,Cr,Pb and Ni in the five sections decreased in different degree,and the distribution of Cu,Pb and Ni was homogeneous in sections,but the distribution of Cr and Zn was fluctuated severely.We also found that all species of heavy metals were removed more or less,and among which the removal of carbonate bound fraction and residual fraction heavy metal was high,but the removal of exchangeable fraction and Fe-Mn oxide fraction heavy metal was low,and the removal of organic sulfide fraction heavy metal falls in between.