Molecular Dynamics Simulation of the Adsorption Interactions of Selected Polar and Nonpolar Polymers on Kaolinite Basal Surfaces in the Presence of Cyclohexane

Abstract

The nonaqueous extraction (NAE) of bitumen has been proposed as a more environmentally friendly alternative to the current water-based extraction process employed in Athabasca oil sands. The high content of fine clays in the solvent-diluted bitumen product is a considerable challenge to the NAE commercial implementation. Seven candidate polymer flocculants were studied in a kaolinite–cyclohexane suspension by using molecular dynamics simulations. The adsorption interactions on both kaolinite basal surfaces were evaluated along with the solubility in cyclohexane. The strongest interaction was observed between poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and the aluminum hydroxide surface, with an adsorption energy of −228 kJ mol–1. On the silicon oxide surface, polyacrylamide interacted the strongest, with an adsorption energy of −106 kJ mol–1. The interactions are interpreted in relation to the number of polymer–surface and polymer–solvent contacts and the cyclohexane–polymer Flory–Huggins interaction parameters and corroborated by the radii of gyration and the solvent accessible surface areas of the polymers in cyclohexane. Polyisoprene (PI) presented the highest number of contacts with kaolinite among the nonpolar polymers. The findings suggest that efficient polymer flocculants containing cyclohexane-soluble and kaolinite-attracting moieties, such as the PI–PAMPS block copolymer, could potentially improve fine solid removal from diluted bitumen product and enhance NAE viability.