National Engineering Research Center of Industrial Wastewater Detoxication and Resource Recovery, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
Water Res. 2024 Nov 1;265:122299. doi: 10.1016/j.watres.2024.122299. Epub 2024 Aug 18.
The removal of arsenic (As(III)) from acidic wastewater using neutralization or sulfide precipitation generates substantial arsenic-containing hazardous solid waste, posing significant environmental challenges. This study proposed an advanced ultraviolet (UV)/dithionite reduction method to recover As(III) in the form of valuable elemental arsenic (As(0)) from acidic wastewater, thereby avoiding hazardous waste production. The results showed that more than 99.9 % of As(III) was reduced to As(0) with the residual concentration of arsenic below 25.0 μg L within several minutes when the dithionite/As(III) molar ratio exceeded 1.5:1 and the pH was below 4.0. The content of As(0) in precipitate reached 99.70 wt%, achieving the purity requirements for commercial As(0) products. Mechanistic investigations revealed that SO and H· radicals generated by dithionite photolysis under UV irradiation are responsible for reducing As(III) to As(0). Dissolved O, Fe(III), Fe(II), Mn(II), dissolved organic matter (DOM), and turbidity slightly inhibited As(III) reduction via free radicals scavenging or light blocking effect, whereas other coexisting ions, such as Mg(II), Zn(II), Cd(II), Ni(II), F(-I), and Cl(-I), had limited influence on As(III) reduction. Moreover, the cost of treating real arsenic-containing (250.3 mg L) acidic wastewater was estimated to be as low as $0.668 m, demonstrating the practical applicability of this method. This work provides a novel method for the reductive recovery of As(III) from acidic wastewater.
使用中和或硫化物沉淀去除酸性废水中的砷（As(III)）会产生大量含砷的危险固体废物，对环境造成重大挑战。本研究提出了一种先进的紫外线（UV）/连二亚硫酸钠还原方法，可将酸性废水中的 As(III)以有价值的元素砷（As(0)）的形式回收，从而避免产生危险废物。结果表明，当连二亚硫酸钠/As(III)摩尔比超过 1.5:1 且 pH 值低于 4.0 时，在几分钟内，超过 99.9%的 As(III)被还原为 As(0)，残留砷浓度低于 25.0μg/L。沉淀物中 As(0)的含量达到 99.70wt%，达到商业 As(0)产品的纯度要求。机理研究表明，UV 照射下连二亚硫酸钠光解生成的 SO 和 H·自由基是将 As(III)还原为 As(0)的原因。溶解氧、Fe(III)、Fe(II)、Mn(II)、溶解有机物（DOM）和浊度通过自由基清除或光阻挡效应略微抑制了 As(III)的还原，而其他共存离子，如 Mg(II)、Zn(II)、Cd(II)、Ni(II)、F(-I)和 Cl(-I)，对 As(III)的还原影响有限。此外，处理实际含砷（250.3mg/L）酸性废水的成本估计低至 0.668 美元/m，表明该方法具有实际应用价值。这项工作为从酸性废水中还原回收 As(III)提供了一种新方法。
