Developing and verifying a quantitative dissolution model for metal-bearing nanoparticles in aqueous media

Dissolution of nanoparticles (NPs) determines the fate and subsequently the actual exposure of biota to the NPs. Whether and to what extent NPs dissolve or remain in their particulate form in aqueous media is thus of pivotal knowledge for the safety assessments of NPs. In this research, secondary data on dissolution of NPs were systematically collected. A range of dissolution rates could be recalculated, as dependent on the characteristics of the NPs and the exposure medium. For example, two nanoparticles which are identical in terms of chemical composition of the particle core and of the coating, had a fully different dissolution behaviour, as subject to different surface modifications. A model was derived for calculating dissolution rate constants of NPs. The model is based on the initial kinetics of dissolution of NPs under different exposure scenarios and on the assumption of pseudo-first order reaction kinetics at the particle surface. Characterizing the dissolution rates and the parameters which modify dissolution allows for grouping of those NPs that dissolve either very slowly or very quickly. This information can be used for risk assessment of NPs, and once sufficient kinetic dissolution data are available, will ultimately allow for development of predictive models for the dissolution kinetics of newly developed nanomaterials.