Competitive ion-exchange reactions of Pb(II) (Pb2+/PbCl+) and Ra(II) (Ra2+) on smectites: Experiments, modeling, and implication for 226Ra(II)/210Pb(II) disequilibrium in the environment. (February 2023)

• Record Type: Journal Article
• Authors: Parrotin, Flora; Robin, Valentin; Beaucaire, Catherine; Descostes, Michael; Tertre, Emmanuel
• Is Part Of: Chemosphere. Volume 313(2023)
• Publication Date: 2023-02
• Subjects: Ion-exchange -- Ion pairs -- Lead -- Radium -- Radioactive disequilibrium -- Smectite; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.137369
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: In this study, new experimental data for the adsorption of lead onto a swelling clay mineral with a tetrahedral charge (beidellite) at the ultratrace level (<10 −10 M) are presented. The data were interpreted using an ion-exchange multisite model that considers the sorption of major cations (including H + ), which always compete with trace elements for sorption onto mineral surfaces in natural environments. The ability of the proposed model to predict experimental Kd values under various conditions of ionic strength (fixed by NaCl solutions) and aqueous cation compositions (including Pb 2+ and PbCl + ) was tested. The proposed model was applied to experimental data previously published for other types of swelling clay minerals, and the results were compared with the results obtained using previously published models. The preferential adsorption of chloride ion pairs, as well as the effect of the swelling clay crystal chemistry on lead adsorption, were assessed. Finally, the selective adsorption behavior of 226 Ra compared to 210 Pb was demonstrated, which has implications for the study of many environmental processes using isotope partitioning. Graphical abstract: Image 1 Highlights: Reliable multisite ion-exchange model for Pb 2+ and PbCl + on swelling clay minerals. Preferential adsorption on clay minerals of PbCl + ion pairs compared to Pb 2+ . 226 Ra/ 210 Pb disequilibrium evidenced due to selective adsorption on smectite.