Antimony isotope fractionation during adsorption on aluminum oxides

Weiqing Zhou; Aiguo Zhou; Bing Wen; Peng Liu; Zhenli Zhu; Zou Finfrock; Jianwei Zhou

doi:10.1016/j.jhazmat.2022.128317

Antimony isotope fractionation during adsorption on aluminum oxides

J Hazard Mater. 2022 May 5:429:128317. doi: 10.1016/j.jhazmat.2022.128317. Epub 2022 Jan 20.

Authors

Weiqing Zhou¹, Aiguo Zhou², Bing Wen³, Peng Liu², Zhenli Zhu⁴, Zou Finfrock⁵, Jianwei Zhou⁶

Affiliations

¹ School of Environmental Studies, China University of Geosciences, Wuhan 430074, People's Republic of China; Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, China University of Geosciences, Wuhan 430074, People's Republic of China.
² School of Environmental Studies, China University of Geosciences, Wuhan 430074, People's Republic of China.
³ State Environmental Protection Key Laboratory of Soil Environmental Management and Pollution Control, Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, People's Republic of China.
⁴ State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, People's Republic of China.
⁵ CLS@APS sector 20, Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA; Science Division, Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK S7N 2V3, Canada.
⁶ School of Environmental Studies, China University of Geosciences, Wuhan 430074, People's Republic of China; Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, China University of Geosciences, Wuhan 430074, People's Republic of China. Electronic address: jw.zhou@cug.edu.cn.

PMID: 35086037
DOI: 10.1016/j.jhazmat.2022.128317

Abstract

The environmental fate of antimony (Sb) is often strongly affected by adsorption, and the Sb isotope fractionation mechanism during adsorption has not been reported. Four batch experiments (kinetic, isothermal, effect of pH, and effect of coexisting anions) were conducted to evaluate the mechanism of Sb(V) adsorption to γ-Al₂O₃ and the fractionation of Sb isotopes. Extended X-ray absorption fine structure (EXAFS) analyses show Sb(V) adsorption on γ-Al₂O₃ occurs via outer-sphere surface complexation. The triple-layer model (TLM) effectively predicted the theoretical Sb adsorption amount under different pH conditions. The Sb isotope fractionation in the adsorption process can be divided into an initial kinetic stage (Rayleigh model, α_{adsorbed-aqueous} = 0.99975 ± 0.00003) and subsequent isotopic equilibrium stage due to isotope exchange; however, no significant equilibrium isotope fractionation (Δ¹²³Sb_{aqueous-adsorbed} = ~0 ± 0.08‰) was evident by the end of the experiments. We propose the lack of significant equilibrium isotope fractionation in the effect of pH and isothermal experiments is due to Sb forming an outer-sphere complex on γ-Al₂O_3. This study reveals Sb equilibrium isotope fractionation does not occur during Sb(V) adsorption onto γ-Al₂O₃, providing a reference for the future study of Sb isotopes and furthering understanding of the Sb isotope fractionation mechanism.

Keywords: Adsorption; Antimony; Isotope fractionation; X-ray absorption spectroscopy; γ-Al(2)O(3).