Size-dependent dissolution kinetics of CaCO3 nanoparticles in theory and experiment

Abstract

In preparation and application of nanomaterials, the dissolution of nanoparticles is usually involved. However, it remains unclear about size dependent the dissolution kinetic parameters of nanoparticles. In this paper, kinetic model for the dissolution of nanoparticles is proposed, and the relations between dissolution kinetic parameters (rate constant, order, apparent activation energy and pre-exponential factor), respectively, and particle sizes were theoretically deduced by applying the transition state theory to the dissolution process, and then the influence regularity and mechanism of particle size on the kinetic parameters were discussed. Experimentally, the dissolution kinetic parameters of nano-CaCO3 with different particle sizes were determined by conductivity meter, and the quantitative influences of particle size on the dissolution kinetics were obtained. The experimental results are consistent with the theoretical relations. The results show that there are significant effects of the particle sizes of CaCO3 nanoparticles on dissolution kinetic parameters; with the particle diameter decreasing, the apparent activation energy and the pre-exponential factor correspondingly decrease, while the rate constant and the dissolution order increase sharply. When the diameter of nanoparticle exceeds 20 nm, the logarithm of the dissolution rate constant, the apparent activation energy, and the logarithm of the pre-exponential factor are all linearly related with the reciprocal of particle diameter. Furthermore, the apparent activation, the dissolution order, the pre-exponential factor, and the dissolution rate constant are influenced by the partial molar surface enthalpy, the partial molar surface area, the partial molar surface entropy, and the partial molar surface Gibbs energy, respectively.