(154f) Adsorption of Ethoxylated Alkyl Phenols From High Salinity Brines

Anionic surfactants are generally used in oil field applications to lower the interfacial tension between crude oil and brine because they are less expensive and have lower adsorption on reservoir minerals. One of the main challenges in applying nonionic surfactant in is a significant loss of surfactant by adsorption onto rock or clay surfaces. At high salinities, however, ionic surfactants may precipitate, and the electrostatic repulsion that reduces their adsorption on rock surfaces may become insignificant. Because nonionic surfactants possess low critical micelle concentration and high brine tolerance, they are of interest in this research. Nonionic surfactants have the potential to decrease surfactant adsorption and reduce the potential for phase separation in high salinity brines. In this study, the adsorption behavior of polyethoxylated octylphenol and polyethoxylated nonylphenol on silica in various aqueous solutions was investigated. Surfactant adsorption isotherms were used to study the effects of increasing salinity concentrations on the mechanism of adsorption and the overall adsorption density. The results show that increasing salinity causes increased adsorption; however, the similarity between adsorption isotherms and the single curve obtained after normalization of the isotherms at various salinities suggests a consistent mechanism of adsorption that is independent of salt concentration. These similarities also suggests that there may be an upper limit to nonionic surfactant adsorption so that after some maximum electrolyte concentration little additional adsorption occurs.