Dissolution kinetics: Catalysis by strong acids

Abstract

The dissolution of silicate minerals in mixtures of hydrofluoric acid and strong acids such as HCl is catalyzed by H+ ions adsorbed at the mineral surface. Studies of the catalyzed dissolution of kaolinite, quartz, potassium feldspar, and sodium montmorillonite have shown that the rates of dissolution can be increased by as much as 900%. The dissolution process can be modeled as simultaneous catalyzed and uncatalyzed reactions, where the surface concentration of H+ ions is determined by a Langmuir adsorption isotherm. The degree of catalysis is a strong function of the nature of the silicate surface, a fact which has application in the area of selective dissolution within mixed mineral systems.