Mechanisms of selenate adsorption at the imogolite-water interface

Abstract

Selenium (Se) can be toxic at high concentrations, mainly through exposure to contaminated groundwater and bioaccumulation in plants. Under oxidizing conditions, Se has preferential inorganic forms, Se oxyanions, which are highly soluble and weakly adsorbed on mineral surfaces. Therefore, retarding the release and migration of Se oxyanions is critical for the protection of groundwater quality. Imogolite is a tubular aluminosilicate with a high adsorptive capacity for anions, including IO3-, TcO4-, and PO43-. However, the potential adsorption of selenate on imogolite has not yet been evaluated to determine potential environmental applications including groundwater remediation. In this study, we synthesized and characterized imogolite using solid-state and electrostatic techniques. The synthesized imogolite was used to evaluate the adsorption of selenate under a range of physiochemical conditions using adsorption isotherms combined with various modeling techniques including the Freundlich model and the charge distribution at multi-site surface complexation (CD-MUSIC) model to decipher surface complexation mechanisms of selenate on imogolite. SynopsisAdsorption affinity and mechanisms of selenate on imogolite are mechanistically evaluated to understand potential environmental applications of imogolite for the protection of groundwater quality.