Simultaneous Kinetics of Selenite Oxidation and Sorption on ?-MnO 2 in Stirred-Flow Reactors

Zheyong Li, Yajun Yuan, Lin Ma, Yihui Zhang, Hongwei Jiang, Jiqiang He, Yifan Hu, Shoushu Yuan, Matthew Ginder-Vogel and Shuxin Tu
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Zheyong Li: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
Yajun Yuan: School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, China
Lin Ma: CAS Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
Yihui Zhang: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
Hongwei Jiang: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
Jiqiang He: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
Yifan Hu: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
Shoushu Yuan: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
Matthew Ginder-Vogel: Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
Shuxin Tu: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China

IJERPH, 2021, vol. 18, issue 6, 1-16

Abstract: Selenium (Se) is an essential and crucial micronutrient for humans and animals, but excessive Se brings negativity and toxicity. The adsorption and oxidation of Se(IV) on Mn-oxide surfaces are important processes for understanding the geochemical fate of Se and developing engineered remediation strategies. In this study, the characterization of simultaneous adsorption, oxidation, and desorption of Se(IV) on ?-MnO 2 mineral was carried out using stirred-flow reactors. About 9.5% to 25.3% of Se(IV) was oxidized to Se(VI) in the stirred-flow system in a continuous and slow process, with the kinetic rate constant k of 0.032 h ?1 , which was significantly higher than the apparent rate constant of 0.0014 h ?1 obtained by the quasi-level kinetic fit of the batch method. The oxidation reaction was driven by proton concentration, and its rate also depended on the Se(IV) influent concentration, flow rate, and ?-MnO 2 dosage. During the reaction of Se(IV) and ?-MnO 2 , Mn(II) was produced and adsorbed strongly on Mn oxide surfaces, which was evidenced by the total reflectance Fourier transform infrared (ATR-FTIR) results. The X-ray photoelectron spectroscopy (XPS) data indicated that the reaction of Se(VI) on ?-MnO 2 produced Mn(III) as the main product. These results contribute to a deeper understanding of the interface chemical process of Se(IV) with ?-MnO 2 in the environment.

Keywords: selenium; oxidation; adsorption; manganese oxide; simultaneous kinetics (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
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