Phosphate and illite colloid pose a synergistic risk of enhanced uranium transport in groundwater: A challenge for phosphate immobilization remediation of uranium contaminated environmental water

Xiaoyan Wei; Xinyi Shi; Meilin Yang; Qi Tan; Zhen Xu; Bin Ma; Duoqiang Pan; Wangsuo Wu

doi:10.1016/j.watres.2024.121514

Phosphate and illite colloid pose a synergistic risk of enhanced uranium transport in groundwater: A challenge for phosphate immobilization remediation of uranium contaminated environmental water

Water Res. 2024 May 15:255:121514. doi: 10.1016/j.watres.2024.121514. Epub 2024 Mar 24.

Authors

Xiaoyan Wei¹, Xinyi Shi², Meilin Yang², Qi Tan², Zhen Xu², Bin Ma³, Duoqiang Pan⁴, Wangsuo Wu⁵

Affiliations

¹ MOE Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China; Laboratory for Waste Management, Paul Scherrer Institut (PSI), CH-5232 Villigen PSI, Switzerland.
² School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
³ Laboratory for Waste Management, Paul Scherrer Institut (PSI), CH-5232 Villigen PSI, Switzerland; College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, China.
⁴ MOE 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.
⁵ MOE Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China; School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.

PMID: 38554633
DOI: 10.1016/j.watres.2024.121514

Abstract

The phosphorus-containing reagents have been proposed to remediate the uranium contaminated sites due to the formation of insoluble uranyl phosphate mineralization products. However, the colloids, including both pseudo and intrinsic uranium colloids, could disturb the environmental fate of uranium due to its nonnegligible mobility. In this work, the transport pattern and micro-mechanism of uranium coupled to phosphate and illite colloid (IC) were investigated by combining column experiments and micro-spectroscopic evidences. Results showed that uranium transport was facilitated in granular media by forming the intrinsic uranyl phosphate colloid (such as Na-autunite) when the pH > 3.5 and C_Na+ < 10 mM. Meanwhile, the mobility of uranium depended greatly on the typical water chemistry parameters governing the aggregation and deposit of intrinsic uranium colloids. However, the attachment of phosphate on illite granule increased the repulsive force and enhanced the dispersion stability of IC in the IC-U(VI)-phosphate ternary system. The non-preequilibrium transport and retention profiles, HRTEM-mapping, as well as TRLFS spectra revealed that the IC enhanced uranium mobility by forming the ternary IC-uranyl phosphate hybrid, and acted as the coagulation preventing agent for uranyl phosphate particles. This observed facilitation of uranium transport resulted from the formation of intrinsic uranyl phosphate colloids and IC-uranyl phosphate hybrids should be taken into consideration when evaluating the potential risk of uranium migration and optimizing the in-situ mineralization remediation strategy for uranium contaminated environmental water.

Keywords: Illite colloid; Phosphate; Transport risk; Uranium.