ABSTRACT In this study, the enhanced effect of oxalic acid (Ox) on Cr(VI) electroreduction was evaluated. It was found that for Cr(VI)-contaminated solution ([Cr(VI)]0 = 1.0 mM, pH = 3.0), addition of 5.0 mM Ox can significantly increase Cr(VI) reduction from 0.36 to 1.0 mM within 90 min electrolysis reaction, accompanying with the increase of current efficiency from 19% to 53%. Increasing initial Ox concentration (0–10 mM) and electric current (10–40 mA) facilitated Cr(VI) reduction, whereas it was inhibited with decreasing solution pH value (2.0–3.5) and elevating Cr(VI) concentration (0.1–2.0 mM), respectively. Results show that reactive electron was the primary reductant for the heterogeneous reduction of Cr(VI) on the cathode. In addition, Ox can also serve as an electron donor for the homogeneous reduction of Cr(VI). During this process, the formation of Cr(VI)-oxalate complex is indispensable for the enhanced Cr(VI) reduction. The coordination of Ox with Cr(VI) did not only make the structure of Cr(VI) more distorted but also improved the reactivity of Cr(VI) in Cr(VI)-oxalate complex toward reduction reaction. In general, this study provides an energy-efficient and environmentally benign strategy for the treatment of Ox and Cr(VI) co-contaminated wastewater. GRAPHICAL ABSTRACT

中文翻译：

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草酸通过形成中间体 Cr(VI)-草酸盐络合物对 Cr(VI) 电还原的增强作用

摘要 在本研究中，评估了草酸 (Ox) 对 Cr(VI) 电还原的增强作用。发现对于 Cr(VI) 污染的溶液 ([Cr(VI)]0 = 1.0 mM, pH = 3.0)，添加 5.0 mM Ox 可以在 90 分钟内显着增加 Cr(VI) 的还原量从 0.36 到 1.0 mM电解反应，电流效率从 19% 提高到 53%。增加初始氧浓度 (0-10 mM) 和电流 (10-40 mA) 促进了 Cr(VI) 的还原，而它会随着溶液 pH 值的降低 (2.0-3.5) 和 Cr(VI) 浓度的升高 (0.1-) 而受到抑制2.0 mM)，分别。结果表明，反应电子是阴极上 Cr(VI) 异相还原的主要还原剂。此外，Ox 还可以作为电子供体用于 Cr(VI) 的均相还原。在这个过程中，Cr(VI)-草酸盐络合物的形成对于增强的Cr(VI)还原是必不可少的。Ox与Cr(VI)的配位不仅使Cr(VI)的结构更加扭曲，而且提高了Cr(VI)-草酸盐络合物中Cr(VI)对还原反应的反应性。总的来说，这项研究为处理 Ox 和 Cr(VI) 共污染废水提供了一种节能且环境友好的策略。图形概要 该研究为处理 Ox 和 Cr(VI) 共污染废水提供了一种节能且环境友好的策略。图形概要 该研究为处理 Ox 和 Cr(VI) 共污染废水提供了一种节能且环境友好的策略。图形概要