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Continuum in surface complexation mechanism of selenium oxyanions at the goethite–water interface: Role of interfacial water molecules.

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Title: Continuum in surface complexation mechanism of selenium oxyanions at the goethite–water interface: Role of interfacial water molecules.
Authors: Srabanee, Snigdha1,2 (AUTHOR), Thakur, Uday K.2 (AUTHOR), Mishra, Vivekchandra G.2 (AUTHOR), Kumar, Sumit1,2 (AUTHOR) sumitk@barc.gov.in
Source: Separation Science & Technology. 2026, Vol. 61 Issue 3-5, p608-620. 13p.
Subjects: Selenium, Goethite, Adsorption (Chemistry), Hydrogen-ion concentration, Pollutants, Water boundaries, Ionic strength, Physisorption
Abstract: Adsorption on iron oxide surfaces plays a great role in controlling the fate and migration of environmental contaminants. For structure-property correlation, surface complexation modeling based on spectroscopic details for the contaminants' surface speciation delineates interfacial reactions. Ignoring the role of desorption of interfacial water molecules during inner sphere complexation may, therefore, cause contradictory reports regarding the mechanism of adsorption behavior. In the present study, the adsorption of selenium oxyanions was studied on goethite (α-FeOOH) nanoparticles under varying pH, ionic strength and anion concentration. To incorporate the effect of interfacial water, expression for accounting the energy expense involved in desorption of water molecules was developed and used in the simulation of adsorption data. This modification is necessitated in view of the fast changing dielectric constant for the interfacial water layers. The modeling protocol provided better simulation for higher selenate concentration and ionic strength conditions. It constrained the partitioning of surface species into inner/outer spheric (IS/OS) complexes differently to achieve better simulation results. The present study thus provides a way to remove inconsistency regarding surface speciation of especially weakly absorbing species wherein a small change in the interfacial chemical conditions may tilt binding from OS to IS mode or vice versa. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Adsorption on iron oxide surfaces plays a great role in controlling the fate and migration of environmental contaminants. For structure-property correlation, surface complexation modeling based on spectroscopic details for the contaminants' surface speciation delineates interfacial reactions. Ignoring the role of desorption of interfacial water molecules during inner sphere complexation may, therefore, cause contradictory reports regarding the mechanism of adsorption behavior. In the present study, the adsorption of selenium oxyanions was studied on goethite (α-FeOOH) nanoparticles under varying pH, ionic strength and anion concentration. To incorporate the effect of interfacial water, expression for accounting the energy expense involved in desorption of water molecules was developed and used in the simulation of adsorption data. This modification is necessitated in view of the fast changing dielectric constant for the interfacial water layers. The modeling protocol provided better simulation for higher selenate concentration and ionic strength conditions. It constrained the partitioning of surface species into inner/outer spheric (IS/OS) complexes differently to achieve better simulation results. The present study thus provides a way to remove inconsistency regarding surface speciation of especially weakly absorbing species wherein a small change in the interfacial chemical conditions may tilt binding from OS to IS mode or vice versa. [ABSTRACT FROM AUTHOR]
ISSN:01496395
DOI:10.1080/01496395.2025.2478635