Dissolution of solid particles in liquids: A reaction—diffusion model

The dissolution of solid particles in liquids involves the dissociation of solute molecules through a surface reaction and the subsequent diffusion of these molecules toward the bulk liquid phase. The conventional analysis is mainly based upon extreme cases, i.e. the rate of dissolution is either controlled by surface reaction or by molecular diffusion. Here, the analysis is generalized so that the diffusional resistance and the resistance for the surface reaction are considered simultaneously. Also, the effect of the variation of the solute concentration in the bulk liquid phase on dissolution is taken into account. The applicability of the present model is justified by analyzing the experimental results for the dissolution or human enamel powder in water. The evaporation of a water drop in air and the dissolution of 2-naphthol in water are also discussed. It is concluded that neglecting the effect of the surface reaction in the dissolution kinetics may lead to a significant deviation between experimental data and theoretical calculation.