Aggregation and deposition characteristics of silica particle and calcium carbonate on a solid surface: A molecular dynamics study

Abstract

The presence of silica (SiO2) and calcium carbonate (CaCO3) not only affects the normal operation of the heat exchanger but leads to a reduction in the heat transfer coefficient. In this work, three systems, i.e., SiO2 particle suspension, CaCO3 solution, and SiO2–CaCO3 mixed system, were adopted to analyze the aggregation mechanism and deposition process on the Cu surface using molecular dynamics simulation. The results showed that the interaction between the SiO2 particle and CaCO3 promoted the aggregation and deposition of the mixed cluster. Ca2+ and CO32− in the solution reduced the denseness of the first water molecular layer on the surface of Cu and SiO2, promoting the aggregation and deposition of SiO2. The presence of SiO2 provided an adsorption site for the CaCO3 nanocluster, and the mixed cluster rapidly adsorbed on the Cu surface. The presence of SiO2 hinders ion-to-ion agglomeration and promotes the association between ions and SiO2, accelerating the formation of the mixed cluster. The deposition time of the mixed cluster decreases with the increased CaCO3 concentration. Moreover, the number of ions adsorbed on the SiO2 surface increased synchronously. The results from the study help in better understanding the early formation process of composite fouling, reveal the aggregation and deposition mechanism, and provide a theoretical basis for the study of scale suppression methods.