Bromate (BrO3−) 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−1, 2.50 mg L−1, 5.00 mg L−1 were identically close to 0.08 min−1. For 0.20 mg L−1, a reaction rate coefficient near 0.10 min−1 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−1) 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.
Tianhao Na,Hui Zhu,Pei Chen,Fang Liu,Yong Yi,Jian Zhou,Tao Duan,Jiehong Lei
During the spent fuel reprocessing, large quantities of radioactive iodine vapor are generated. The complex conditions of high temperature, strong acidity, and high humidity are critical factors to consider when designing iodine vapor adsorbents. This paper reports on the synthesis of an in-situ grown nanoscale zero-valent bismuth-doped polyvinylpyrrolidone (PVP) 3D honeycomb-like porous carbon material (Bi 0 @PVP-C) for the efficient capture and immobilization of iodine vapor under high temperature, strong acidic, and high humidity conditions. Bi 0 @PVP-C exhibits a 3D porous honeycomb morphology with abundant layered structures. At 200 °C, its iodine vapor capture capacity reaches an astonishing 1252.16 mg/g, significantly higher than other bismuth-containing adsorbents. Characterization techniques such as XRD, HRTEM, XPS, and density functional theory calculations using the Dmol3 module in Materials Studio software, demonstrate that the primary mechanism involves a chemical reaction between abundant nanoscale zero-valent bismuth particles within the pores of Bi 0 @PVP-C and iodine vapor. The unique affinity of elemental bismuth for iodine enables the material to selectively capture iodine vapor, forming stable BiI 3 . Furthermore, due to the excellent acid resistance and hydrophobicity of Bi 0 @PVP-C, the iodine vapor capture capacities under conditions of pH = 2 and 75 % humidity remain high at 1003.56 mg/g and 1135.27 mg/g, respectively. Compared to the optimal capture capacity, there is only a slight decrease of 19.8 % and 9.3 %. Therefore, Bi 0 @PVP-C exhibits excellent application potential for iodine vapor capture under complex conditions of high-temperature, high-humidity, and strong acidity.
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