Effects of interfacial dynamics and nanoconfinement on the aggregation characteristics of CaSO4 in aqueous solutions inside 2D nanochannels

Abstract

In this study, molecular dynamics simulations were used to investigate the effects of interfacial dynamics and nanoconfinement on the cluster characteristics and aggregation mechanisms of CaSO4 solutions inside two-dimensional (2D) nanochannels. Results reveal that CaSO4 clusters with low hydration are more likely to be found in 2D nanochannels than in a bulk solution. The interface region formed by layered water molecules results in the specific ion distributions inside a 2D nanochannel, affecting the hydration dynamics of Ca2+ ions near the interface region and ion-association characteristics. When Ca2+ ions migrate from the interface region to the bulk-like region, the association of Ca2+ and SO42− ions is promoted and the water exchange around CaSO4 clusters is enhanced, benefiting the formation of CaSO4 clusters with Ca2+ ions in high coordinated and low hydration degrees. Our results offer a microscopic understanding of the characteristics of prenucleation clusters and aggregation mechanisms in CaSO4 solutions inside 2D nanochannels, helping to control of the morphology and properties of CaSO4 precipitation.