Mineralsorption

Mineralsorption is the process by which dissolved species adhere to mineral surfaces or exchange with ions bound to those surfaces. In environmental and soil science, it encompasses adsorption (including outer-sphere and inner-sphere complexation) and ion exchange on minerals such as clays, iron and aluminum oxides, and other silicate minerals. While adsorption refers to the attachment of ions to surface sites, ion exchange involves the replacement of surface-bound ions with ions from solution. Together, these mechanisms influence the distribution and mobility of nutrients and contaminants in natural systems.

The specific mechanisms depend on mineralogy, surface area, and the chemical conditions of the environment. Surface complexation models describe how ions form bonds with surface sites, often influenced by pH, ionic strength, and the presence of competing ions. Factors such as the mineral’s point of zero charge, charge density, and sorption sites determine whether a given species is strongly sorbed or remains in solution. Phosphates and arsenates commonly sorb to iron oxides, while cesium and other cations interact with clay minerals like illite or montmorillonite.

Applications and significance include controlling contaminant transport in soils and groundwater, nutrient availability in agriculture, and strategies for remediation. Sorption can be reversible or effectively irreversible under certain conditions. Laboratory sorption isotherms and kinetic studies (e.g., Langmuir, Freundlich models) help quantify capacity and rates, but natural systems are complex due to coupled dissolution-precipitation processes and mineralogical heterogeneity.