ASPHALTENES ADSORPTION BY QUARTZ AND FELDSPAR

Abstract

ABSTRACT The adsorption of asphaltenes and resins from toluene solutions onto quartz and feldspar and the effect of this process on the properties of the mineral-aqueous solution interface have been investigated. Asphaltenes were adsorbed to a greater extent than resins, and the adsorption of mixtures was at least equivalente to the weighted average of the adsorption of both components separately. The electrophoretic mobility of quartz or feldspar was not modified by the adsorption of asphaltenes or resins, indicating that the sites responsible for the surface charge of the minerals were unaffected by the presence of the adsorved organic species. The adsorption turned the minerals partially hydrophobic. This effect is more important for asphaltene covered particles which do not immerse in aqueous electrolyte solutions, indicating a contact angle larger than 90a immersion become spontaneous in liquid mixtures (methanol-water, ethanol-water), presenting a surface tension lower than 35 mNm-1. Ethoxylated and ethoxylated-propoxylated surface active agents prevent the adsorption of asphaltenes and resins on the minerals, and this effect increases as the ethoxylated/propoxylated moiety of the surfactant increases. The results indicate that fine particles with adsorbed polar fractions of oil play an important role in the stabilization of the water-in-oil emulsions formed in some secondary oil recovery processes and that ethoxylated/propoxylated surfactants and/or solvents may prevent the formation of these emulsions by modifying the wetting behaviour of the mineral particles.