Insights into sorption speciation of uranium on phlogopite: Evidence from TRLFS and DFT calculation

Duoqiang Pan; Xiaodong Zhao; Peng Wang; Ping Li; Yuhong Li; Wangsuo Wu; Zheming Wang; Qiaohui Fan

doi:10.1016/j.jhazmat.2021.128164

Insights into sorption speciation of uranium on phlogopite: Evidence from TRLFS and DFT calculation

J Hazard Mater. 2022 Apr 5:427:128164. doi: 10.1016/j.jhazmat.2021.128164. Epub 2021 Dec 28.

Authors

Duoqiang Pan¹, Xiaodong Zhao², Peng Wang², Ping Li³, Yuhong Li², Wangsuo Wu⁴, Zheming Wang⁵, Qiaohui Fan³

Affiliations

¹ Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China; School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China. Electronic address: panduoqiang@lzu.edu.cn.
² School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
³ Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
⁴ Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China.
⁵ Pacific Northwest National Laboratory, Richland, WA 99352, United States.

PMID: 34991008
DOI: 10.1016/j.jhazmat.2021.128164

Abstract

Knowledge of the sorption speciation of uranium at mineral/water interface is essential to construct reliable retention and migration models. In this work, the sorption speciation of U(VI) at the phlogopite/water interface was studied at trace concentrations by combining batch sorption, time-resolved luminescence spectroscopy, and theoretical calculation. Batch experiments showed that the sorption of U(VI) on phlogopite was strongly dependent on pH but weakly affected by ionic strength, implying that the inner-sphere surface complexation was mainly responsible for U(VI) sorption on phlogopite. The diverse luminescence spectral characteristics indicated the formation of multiple inner-sphere surface species at the phlogopite/water interface, whose abundances varied as a function of pH. A portion of U(VI) precipitated as uranyl oxyhydroxides such as metaschoepite and becquerelite at high pH. Density functional theory calculation revealed that the bidentate complex at the edge of phlogopite (≡AlO-MgO-UO₂(H₂O)₃) was the most favorable sorption configuration for U(VI) at acidic condition. The increasing temperature enhanced the sorption of U(VI) on phlogopite without altering the sorption species, and such enhancement in U(VI) sorption was withdrawn once the temperature decreased. These findings are essential for understanding the immobilization mechanism of U(VI) in mica-rich granitic terrains at a molecular scale and building a reliable retention model.

Keywords: Phlogopite; Sorption; Speciation; Uranium.