Simple mechanistic models for inhibition of a dissolution reaction

In this paper we examine the effect of inhibition on mineral dissolution rate. We postulate a reaction mechanism that involves catalysis and inhibition. The reaction mechanism consists of fast adsorption of a catalyst and/or an inhibitor on the mineral surface, followed by a slow hydrolysis step. The rate of the hydrolysis, which is the rate-determining step, demands on the adsorbed surface species. Therefore, the rate law includes the adsorption isotherms of the catalyst and the inhibitor. Two endmember mechanisms are analyzed. In the first mechanism the catalyst and the inhibitor compete with each other; ie, they have a full mutual (negative) dependence; while in the second mechanism we assume that the adsorption of the catalyst and the inhibitor are absolutely independent on each other. A third general mechanism describes the whole range between the two endmember mechanisms. In this model, the degree of dependence of the catalyst adsoption on the inhibitor adsorption varies from 1 to 0, ie, from complete competition to full independence, respectively. The models are applied to three case studies of kaolinite, albite and K-feldspar dissolution.