This study aims to clarify the removal mechanism and to calculate the effective current of electrocoagulation (i.e., EC) for treating wastewater containing Ni(II), Cu(II), and Cr(VI). The adsorption behavior of various heavy metals onto Al(OH)3 coagulant generated by the EC process was investigated and the estimating method of the corresponding current was established. Results indicate that adsorption of single Ni(II) and Cu(II) by Al(OH)3 coagulant can be simulated by the Langmuir isotherm, while Cr(VI) adsorption fits the Freundlich isotherm better. As treating single heavy metal of wastewater, the removal mechanism of the EC process is the adsorption reaction. Under the coexisting condition, the Ni(II) and Cu(II) will compete for the same active sites on the Al(OH)3 surface and Cu(II) suppresses Ni(II) adsorption. As treating the coexisting heavy metals, Ni(II) removal not only associates with adsorption but also with the coprecipitation. In contrast, Cr(VI) does not compete with other metal ions for the same type of adsorption sites. Whether single or coexisting conditions, the adsorption capacity of heavy metals onto Al(OH)3 coagulants can be used to compute the necessary current to effectively remove heavy metals in the EC system.

中文翻译：

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电絮凝处理含Ni(II)、Cu(II)、Cr(VI)废水的去除机理及有效电流

本研究旨在阐明去除机理并计算电凝聚（即 EC）处理含 Ni(II)、Cu(II) 和 Cr(VI) 废水的有效电流。研究了各种重金属在EC工艺产生的Al(OH)3混凝剂上的吸附行为，建立了相应电流的估算方法。结果表明，Al(OH)3混凝剂对Ni(II)和Cu(II)的吸附可以通过Langmuir等温线模拟，而Cr(VI)吸附更符合Freundlich等温线。作为处理废水中的单一重金属，EC工艺的去除机理是吸附反应。在共存条件下，Ni(II)和Cu(II)将竞争Al(OH)3表面的相同活性位点，Cu(II)抑制Ni(II)吸附。在处理共存的重金属时，Ni(II)的去除不仅与吸附有关，而且与共沉淀有关。相比之下，Cr(VI) 不与其他金属离子竞争相同类型的吸附位点。无论是单一条件还是共存条件，重金属在 Al(OH)3 混凝剂上的吸附能力都可用于计算有效去除 EC 系统中重金属所需的电流。