Huang Hong, Liu Guoshuai, Wang Xiuheng
State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology Harbin 150090 China
RSC Adv. 2020 Jan 24;10(7):4148-4155. doi: 10.1039/c9ra10391k. eCollection 2020 Jan 22.
Bromate (BrO ) is a carcinogenic and genotoxic by-product of the ozone disinfection process. In this study, a new zero-valent metal, bismuth, was used to reduce bromate. Bismuth samples were prepared by a solvothermal method and characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The morphology of the bismuth powder was microspheres assembled with dense nanosheets. The kinetics of the direct bromate reduction by bismuth accorded with the pseudo-first-order kinetics model. The rate coefficients of the initial bromate concentration of 1.00 mg L, 2.50 mg L, 5.00 mg L were identically close to 0.08 min. For 0.20 mg L, a reaction rate coefficient near 0.10 min was obtained. The reducing products of bromate included bromide ions (Br) and bismuth oxybromides. The bromate removal efficiency was enhanced remarkably in the presence of ultraviolet (UV) light, and the corresponding kinetic coefficient was 4 times higher than that of direct reduction. The mechanism of ultraviolet enhancement was analyzed by diffuse reflectance spectroscopy (DRS), the density functional theory (DFT) calculation, open circuit potential (OCP) analysis, photocurrent measurement and linear sweep voltammetry (LSV). Besides, the influence of dissolved oxygen (DO) on bromate reduction efficiency and the sustainability of the as-prepared sample were investigated. DO inhibited the reduction rate obviously, but showed a slight effect on the formation of bromide ions. In the long-term periodic experiments, the kinetic coefficient decay occurred in both direct (without UV irradiation) and ultraviolet assisted bromate reduction. However, the kinetic coefficient of UV-assisted reduction (0.115 min) was about 2 times higher than that of the direct reduction in the last cycle of periodic experiments. In conclusion, the novel bromate reduction strategy based on the zero-valent bismuth metal material has been proved efficient and sustainable, which contributes to the development of drinking water treatment technologies.
溴酸盐（BrO₃⁻）是臭氧消毒过程中产生的一种具有致癌性和基因毒性的副产物。在本研究中，一种新型零价金属铋被用于还原溴酸盐。铋样品通过溶剂热法制备，并采用粉末X射线衍射（PXRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）进行表征。铋粉的形态为密集纳米片组装而成的微球。铋直接还原溴酸盐的动力学符合准一级动力学模型。初始溴酸盐浓度为1.00 mg/L、2.50 mg/L、5.00 mg/L时的速率系数均接近0.08 min⁻¹。对于0.20 mg/L，获得了接近0.10 min⁻¹的反应速率系数。溴酸盐的还原产物包括溴离子（Br⁻）和溴氧化铋。在紫外光（UV）存在下，溴酸盐去除效率显著提高，相应的动力学系数比直接还原时高4倍。通过漫反射光谱（DRS）、密度泛函理论（DFT）计算、开路电位（OCP）分析、光电流测量和线性扫描伏安法（LSV）对紫外增强机制进行了分析。此外，还研究了溶解氧（DO）对溴酸盐还原效率的影响以及所制备样品的可持续性。溶解氧明显抑制了还原速率，但对溴离子的形成影响较小。在长期周期性实验中，直接（无紫外照射）和紫外辅助溴酸盐还原过程中均出现了动力学系数衰减。然而 在周期性实验的最后一个循环中，紫外辅助还原的动力学系数（0.115 min⁻¹）约为直接还原的2倍。总之，基于零价铋金属材料的新型溴酸盐还原策略已被证明是高效且可持续的，这有助于饮用水处理技术的发展。
