Strong complexation between heavy metals and organic complexing agents makes the heavy metals difficult to be removed by classical chemical precipitation. In this study, a novel decomplexation method was developed using discharge plasma oxidation, which was followed by alkaline precipitation to treat water containing heavy metal–organic complex, that is, Cu–ethylenediaminetetraacetic acid (Cu–EDTA). The decomplexation efficiency of Cu complex reached up to nearly 100% after 60 min’s oxidation by discharge plasma, which was accompanied by 82.1% of total organic carbon removal and energy efficiency of 0.62 g kWh^–1. Presence of free Cu²⁺ favored Cu–EDTA decomplexation, whereas the presence of excessive EDTA depressed this process. Cu–EDTA decomplexation was mainly driven by the produced ¹O₂, O₂^•–, O₃, and •OH by discharge plasma. Cu–EDTA decomplexation process was characterized by UV–vis, ATR–FTIR, total organic carbon, and three-dimensional fluorescence diagnosis. The main intermediates including Cu–EDDA, Cu–IDA, Cu–NTA, small organic acids, NH₄⁺, and NO₃^– were identified, accompanied by Cu²⁺ releasing. The followed precipitation process removed 78.1% of Cu²⁺, and Cu-associated precipitates included CuCO₃, Cu₂CO₃(OH)₂, CuO, and Cu(OH)₂. A possible pathway of Cu complex decomplexation and Cu²⁺ removal in such a system was proposed.

中文翻译：

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新型铜（II）-EDTA的放电等离子体氧化分解及碱性沉淀去除铜的机理：机理

重金属与有机络合剂之间的强络合使得重金属很难通过经典的化学沉淀法去除。在这项研究中，使用放电等离子体氧化技术开发了一种新的分解方法，随后进行碱性沉淀来处理含有重金属-有机配合物（即铜-乙二胺四乙酸（Cu-EDTA））的水。放电等离子体氧化60分钟后，Cu络合物的分解效率达到近100％，伴随着总有机碳去除量的82.1％和0.62 g kWh ^–1的能量效率。游离Cu ^2+的存在促进了Cu-EDTA的分解，而过量EDTA的存在抑制了该过程。Cu-EDTA的分解过程主要由产生的产物驱动¹ O ₂，O ₂ ^•–，O ₃和•OH通过放电等离子体产生。Cu-EDTA分解过程的特征在于UV-vis，ATR-FTIR，总有机碳和三维荧光诊断。鉴定出了主要中间体，包括Cu–EDDA，Cu–IDA，Cu–NTA，小有机酸，NH ₄ ⁺和NO ₃ ^–并伴有Cu ^2+的释放。随后的沉淀过程除去了78.1％的Cu ²⁺，并且与Cu相关的沉淀包括CuCO ₃，Cu ₂ CO ₃（OH）₂，CuO和Cu（OH）₂。提出了在这种系统中铜络合物分解和去除Cu ^2+的可能途径。