Mechanisms of UV-Light Promoted Removal of As(V) by Sulfide from Strongly Acidic Wastewater
Mechanisms of UV-Light Promoted Removal of As(V) by Sulfide from Strongly Acidic Wastewater
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DOI：
10.1021/acs.est.7b02451
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发表时间：
2017-11-07
影响因子：
11.4
通讯作者：
Hu, Xingyun
中科院分区：
文献类型：
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作者：
Kong, Linghao;Peng, Xianjia;Hu, Xingyun
具有高砷浓度的强酸性废水由许多工业产生。用硫化物去除强酸性废水中的As（V）（H3 AsO 4）是一个难题。本研究提出了一种紫外光辅助硫化物去除砷（V）的方法，并对其机理进行了系统的研究。在黑暗条件下，硫化物对As（V）的去除效率较低，这是由于中间物种的形成和转化缓慢，硫代砷酸根（H3 AsO 3S）的存在是硫化反应的主要控制步骤。然而，紫外光照射不仅通过光诱导HS中心点和中心点H自由基促进H3 AsO 3S的形成，而且通过H3 AsO 3S络合物中S（-II）和As（V）之间的电荷转移过程促进H3 AsO 3S的转化，从而显著提高As（V）的去除效率，导致As（V）还原成As（III）和S（-II）氧化成S（O）。形成的As（III）物质在过量S（-II）下立即沉淀为As 2S 3。动力学模型提供了一个定量的解释的结果，并验证了所提出的机制。该研究为光促进As（V）硫化去除的应用提供了理论基础，可促进强酸性废水中砷和酸的回收利用。
Strongly acidic wastewater with a high arsenic concentration is produced by a number of industries. The removal of As(V) (H3AsO4) by sulfide from strongly acidic wastewater remains a difficult issue. This study proposed a UV-assisted method to efficiently remove As(V) by sulfide, and, the involved mechanisms were systematically investigated. In the dark, the low removal efficiency of As(V) by sulfide was attributed to the slow formation and transformation of an intermediate species, i.e., monothioarsenate (H3AsO3S), in the As(V) sulfuration reaction, which were the rate-controlling steps in this process. However, UV irradiation significantly promoted the removal efficiency of As(V) not only by promoting the formation of H3AsO3S through light induced HS center dot and center dot H radicals but also by enhancing the transformation of H3AsO3S through a charge-transfer process between S (-II) and As(V) in the H3AsO3S complex, leading to the reduction of As(V) to As(III) and the oxidation of S (-II) to S(0). The formed As(III) species immediately precipitated as As2S3 under excess S(-II). Kinetic modeling offered a quantitative explanation of the results and verified the proposed mechanisms. This study provides a theoretical foundation for the application of light promoted As(V) sulfuration removal, which may facilitate the recycling and reuse of arsenic and acid in strongly acidic wastewater.