Electrocoagulation (EC) is a facile technique for removing arsenic (As) pollutants from different water matrices with high efficiency. In this work, a novel strategy of Mn-assisted Fe EC was developed to further enhance the removal efficiency of arsenite [As(III)] from wastewater. When 1 mM of MnCl was added to an Fe-EC system, the As removal efficiency reached 99.99%, and the residual concentration was only 9 μg/L, which is lower than the World Health Organization’s limit for drinking water. The characteristics of the generated flocs by four different EC processes in Fe, Fe-Mn, Fe-As, and Fe-Mn-As systems were investigated. The results showed that Mn promoted the formation of FeOOH, FeO, MnO, FeHAsO, and MnHAsO through low crystallinity and a high surface area. Density functional theory simulation and crystal orbital hamiltonian population confirmed that the generated Fe-Mn flocs had a greater adsorption affinity for As(III) and arsenate [As(V)]. The possible reactions in the EC processes and reaction mechanisms were also hypothesised. The current work provides meaningful insights into understanding the mechanisms of Mn-assisted Fe-EC systems, and further confirms its potential for practical applications in As pollution treatment.

中文翻译：

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锰辅助铁电凝高效除砷策略及其机理


电凝 (EC) 是一种简便的技术，可高效去除不同水基质中的砷 (As) 污染物。在这项工作中，开发了一种Mn辅助Fe EC的新策略，以进一步提高废水中亚砷酸盐[As(III)]的去除效率。当Fe-EC体系中添加1mM的MnCl时，砷去除率达到99.99%，残留浓度仅为9μg/L，低于世界卫生组织对饮用水的限值。研究了 Fe、Fe-Mn、Fe-As 和 Fe-Mn-As 体系中四种不同 EC 过程生成的絮凝体的特性。结果表明，Mn通过低结晶度和高表面积促进了FeOOH、FeO、MnO、FeHAsO和MnHAsO的形成。密度泛函理论模拟和晶体轨道哈密顿布居证实生成的Fe-Mn絮体对As(III)和砷酸盐[As(V)]具有更大的吸附亲和力。还假设了EC过程中可能发生的反应和反应机制。目前的工作为理解Mn辅助Fe-EC系统的机制提供了有意义的见解，并进一步证实了其在砷污染处理中实际应用的潜力。