Sorption behavior and mechanism of U(VI) on Tamusu clay in the presence of U(VI)-CO3 complexes

Xiaoyu Yin; Peng Wu; Shilong Shi; Yufan Zhao; Honghui Li; Feize Li; Jiali Liao; Ning Liu; Yuanyou Yang; Tu Lan

doi:10.1016/j.jenvrad.2023.107286

Sorption behavior and mechanism of U(VI) on Tamusu clay in the presence of U(VI)-CO₃ complexes

J Environ Radioact. 2023 Dec:270:107286. doi: 10.1016/j.jenvrad.2023.107286. Epub 2023 Aug 24.

Authors

Xiaoyu Yin¹, Peng Wu¹, Shilong Shi¹, Yufan Zhao¹, Honghui Li², Feize Li¹, Jiali Liao¹, Ning Liu¹, Yuanyou Yang³, Tu Lan⁴

Affiliations

¹ Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
² China Institute for Radiation Protection, Taiyuan, 030006, PR China.
³ Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China. Electronic address: yangyy@scu.edu.cn.
⁴ Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China. Electronic address: tlan720@scu.edu.cn.

PMID: 37633243
DOI: 10.1016/j.jenvrad.2023.107286

Abstract

The sorption behavior of U(VI) on Tamusu clay sampled from a pre-selected high-level radioactive waste (HLW) disposal site in Inner Mongolia (China) was studied systematically in the U(VI)-CO₃ solution at pH 7.8 by batch experiments. The results demonstrated that the distribution coefficients (K_d) decreased with the increasing values of pH_initial, [U(VI)]_initial, and ionic strength, but increased with the extended time and the rising temperature. The sorption was a pH-dependent, heterogeneous, spontaneous, and endothermic chemical process, which could be better described by Freundlich isothermal model and pseudo-second-order kinetic model. The presence of humic acid (HA) or fulvic acid (FA) significantly inhibited the U(VI) sorption, due to the enhanced electrostatic repulsion between the negatively charged HA/FA adsorbed on the clay surface and the negative U(VI) species, as well as the well dispersed HA/FA aggregates in solution wrapping the U(VI) species. The FTIR and XPS spectra indicated that the HCO₃^- groups on the surface of Tamusu clay after hydroxylation and the ‒OH groups in HA/FA were involved in the U(VI) sorption. The results reported here provide valuable insights into the further understanding of U(VI) migration in geological media.

Keywords: Fulvic acid; Humic acid; Mechanisms; Sorption; Tamusu clay; U(VI).

MeSH terms

Adsorption
Clay
Humic Substances
Hydrogen-Ion Concentration
Radiation Monitoring*
Uranium* / chemistry

Substances

Clay
Uranium
Humic Substances