PNNL

Abstract

The van der Waals interaction has been extensively studied for colloidal forces and resultant emergent phenomena such as colloidal stability, aggregation, and suspension rheology, but the effect of electrolytes on the van der Waals interaction, especially at intermediate and high electrolyte concentrations, remains incompletely understood. We have extended the Lifshitz theory for van der Waals interactions in pure water to alkali nitrate solutions at arbitrary concentrations by developing a dielectric response model for alkali nitrate solutions that is based on electronic structure calculations of the molecular constituents. As a benchmark case, the Hamaker constants for rutile, boehmite, and alumina particles in alkali nitrates solutions are calculated as a function of electrolyte concentration. Contrary to prevailing assumptions, increasing the concentration of Na, K, and Rb nitrate solutions causes small increases of the Hamaker constants relative to pure water, and CsNO3 that has almost no effect on the Hamaker constant. We discussed the influence of the solution molar volume, the polarizability of the dissolved ions, and optical properties of the interacting particles in the context of previously published work. Our study indicates a non-vanishing role of van der Waals interactions on colloidal stability at intermediate and high electrolyte concentrations, leading to physical insights on emergent phenomena associated with nanoparticles.