Colloidal stability and correlated migration of illite in the aquatic environment: The roles of pH, temperature, multiple cations and humic acid

Xiaoyan Wei; Duoqiang Pan; Zhen Xu; Dongfan Xian; Xiaolong Li; Zhaoyi Tan; Chunli Liu; Wangsuo Wu

doi:10.1016/j.scitotenv.2020.144174

Colloidal stability and correlated migration of illite in the aquatic environment: The roles of pH, temperature, multiple cations and humic acid

Sci Total Environ. 2021 May 10:768:144174. doi: 10.1016/j.scitotenv.2020.144174. Epub 2021 Jan 9.

Authors

Xiaoyan Wei¹, Duoqiang Pan², Zhen Xu¹, Dongfan Xian³, Xiaolong Li⁴, Zhaoyi Tan⁴, Chunli Liu³, Wangsuo Wu¹

Affiliations

¹ Radiochemistry Laboratory, School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
² Radiochemistry Laboratory, School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China. Electronic address: panduoqiang@lzu.edu.cn.
³ Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry and Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
⁴ Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China.

PMID: 33453530
DOI: 10.1016/j.scitotenv.2020.144174

Abstract

The mobility and environmental risk of colloids and associated pollutants are dependent on their dispersion stability under various conditions. In this work, the stability and correlated migration of illite colloids (IC) were systematically investigated over a wide range of aquatic chemistry conditions. The results showed that IC was aggregation favorable at low pH, low temperature and high ionic strength. The critical coagulation concentration (CCC) of IC increased exponentially with increasing values of r/Z³, following the Schulze-Hardy and Hofmeister series. Humic acid (HA) greatly mitigated colloid aggregation since the attachment of HA on IC surface increased the steric hindrance and electrostatic potential, and the enhancement of stability was linearly correlated with the HA concentration. The Derjaguin-Landau-Verwey-Overbeek (DLVO) model revealed that the interaction force deriving from van der Waals forces and electrostatic double-layer energy evolved as the aquatic chemistry varied, and the reduction in repulsion force between particles facilitated the colloid collision and then aggregation. The migration of IC in the porous sand column was highly correlated with the dispersion stability and filtration effect, the agglomerated colloids were redispersed and released when conditions favored dispersion. The illite colloids acted as efficient carriers for Eu(III) transport. These findings are essential for improving the understanding of the geological fate of environmental colloids and associated radionuclides.

Keywords: Colloids; Environment; Illite; Migration; Stability.