Dissolution of Commercial Microscale Quartz Particles in Water at Biological-Like Conditions and Its Theoretical Description

The solubility of two commercially available microscale quartz powders in water under biological-like conditions is investigated. The experimental results are evaluated by common phenomenological theories and by complete analysis of the Gibbs free energy of the system particles-solution (gradient method). The different theories are compared with each other, and the interrelations between the theories are discussed. The application of the gradient method always leads to the best agreement between experimental results and theory because the gradient model considers the simultaneous changes of both particle size and particle concentration during dissolution. The optimal values of saturation concentrations and dissolution rate constants are determined by statistical analyses and by calculation of the coefficient of determination. The expected influence of temperature on the dissolution behavior is confirmed. Higher values of the crystal strain of the quartz samples result in higher values of the dissolution rate constant and more rapid dissolution. The saturation concentrations and rate constants determined for the commercially available quartz samples are at least 1 order of magnitude larger than most values reported in the literature for natural quartz. In accordance with statements found in the literature, this fact should be taken into account for the assessment of the potential health risk of the investigated commercially available quartz powders.