Surface Chemistry of Soil Minerals

Abstract

This chapter deals with the nature of constant-charge and pH-dependent-charge colloidal surfaces, using descriptions based on models and direct spectroscopic investigations. It outlines several of the more important surface processes including cation exchange, the chemisorption of cations and anions on oxides, and electron and proton transfer reactions. The chapter describes the properties of the pure and well-behaved minerals that are commonly modified in the soil environment. Metal oxides and aluminosilicates possessing surface metal OH (MOH) groups may interact with ionic species by processes more specific than the electrostatic mechanism of ion exchange. The actual mechanisms of electron transfer between adsorbates and Mn oxides are known for only a few reactions. The oxidation of gaseous CO by MnO2 consumes structural O2-ions; the catalyst must then be regenerated by the chemisorption of O2. Charge development on oxide surfaces is then described in terms of the chemisorption of an acid, HX, or base, MOH.