Wastewater containing EDTA-Ni (ethylenediaminetetraacetic acid nickel salt) must be treated due to its high toxicity, accumulation of nickel and non-degradability. In the present study, effect of carbon chain length of dithiocarbamate on the removal efficiency of Ni²⁺ from an EDTA-Ni solution has been analyzed. Sodium dimethyl dithiocarbamate, sodium diethyl dithiocarbamate and sodium dibutyl dithiocarbamate were used to study their Ni²⁺ removal performances from various types of EDTA-Ni solutions. Mechanisms of reactions between different dithiocarbamates and Ni²⁺ were also studied. The results indicate that the rate of Ni²⁺ increased with an increase in the carbon chain length of dithiocarbamate. Infrared spectral analysis inferred that the three dithiocarbamates had similar removal mechanisms despite having different carbon chain lengths: all showing Ni²⁺ chelation. The thiol of dithiocarbamate captures Ni²⁺ and tends to produce an insoluble chelate. The results from scanning electron microscope show that for longer carbon chain, the chelate product is more closely packed. Therefore, removed efficiency by sodium dibutyl dithiocarbamate was higher. Meanwhile coexistence of Cr⁶⁺, Cu²⁺ and Fe³⁺ inhibited the removal of Ni²⁺, but Zn²⁺ promoted it. Metal ion impact became clearer as carbon chain length increased. The chelation capability of the three dithiocarbamates with metal ions was: Cr⁶⁺ < Fe³⁺ < Ni²⁺ < Cu²⁺and Cu²⁺ > Zn²⁺. Finally, these dithiocarbamates were tested in actual electroplating wastewater to validate our conclusions. After sodium dibutyl dithiocarbamate treatment, all residual metals' concentrations met the new tougher requirements announced by the Department of Environmental Protection of Guangdong province in Document No.25.

含EDTA-Ni（乙二胺四乙酸镍盐）的废水由于其高毒性，镍的积累和不可降解性而必须进行处理。在本研究中，已分析了二硫代氨基甲酸酯的碳链长度对EDTA-Ni溶液中Ni ²⁺去除效率的影响。用二甲基二硫代氨基甲酸钠，二乙基二硫代氨基甲酸钠和二丁基二硫代氨基甲酸钠研究了各种EDTA-Ni溶液中Ni ^2+的去除性能。还研究了不同的二硫代氨基甲酸酯与Ni ²⁺之间的反应机理。结果表明，Ni ²⁺的发生率随着二硫代氨基甲酸酯碳链长度的增加而增加。红外光谱分析表明，尽管碳链长度不同，但三种二硫代氨基甲酸酯具有相似的去除机理：均显示Ni ²⁺螯合。二硫代氨基甲酸酯的硫醇捕获Ni ²⁺并倾向于产生不溶的螯合物。扫描电子显微镜的结果表明，对于更长的碳链，螯合物的堆积更紧密。因此，二丁基二硫代氨基甲酸钠的去除效率更高。同时，Cr ⁶⁺，Cu ²⁺和Fe ^3+的共存抑制了Ni ²⁺的去除，而Zn ²⁺推广了它。随着碳链长度的增加，金属离子的影响变得更加明显。三种二硫代氨基甲酸盐与金属离子的螯合能力为：Cr ⁶⁺  <Fe ³⁺  <Ni ²⁺ <Cu ²⁺和Cu ²⁺  > Zn ²⁺。最后，在实际电镀废水中测试了这些二硫代氨基甲酸盐，以验证我们的结论。经过二丁基二硫代氨基甲酸钠处理后，所有残留金属的浓度均符合广东省环境保护厅在第25号文件中宣布的新的更严格要求。