Adsorption of Ethoxylated Alkyl Phenols from High Salinity Brines

摘要

Anionic surfactants are generally used in oil field applications to lower therninterfacial tension between crude oil and brine because they are lessrnexpensive and have lower adsorption on reservoir minerals. One of thernmain challenges in applying nonionic surfactant in is a significant loss ofrnsurfactant by adsorption onto rock or clay surfaces. At high salinities,rnhowever, ionic surfactants may precipitate, and the electrostatic repulsionrnthat reduces their adsorption on rock surfaces may become insignificant.rnBecause nonionic surfactants possess low critical micelle concentrationrnand high brine tolerance, they are of interest in this research. Nonionicrnsurfactants have the potential to decrease surfactant adsorption andrnreduce the potential for phase separation in high salinity brines. In thisrnstudy, the adsorption behavior of polyethoxylated octylphenol andrnpolyethoxylated nonylphenol on silica in various aqueous solutions wasrninvestigated. Surfactant adsorption isotherms were used to study therneffects of increasing salinity concentrations on the mechanism ofrnadsorption and the overall adsorption density. The results show thatrnincreasing salinity causes increased adsorption; however, the similarityrnbetween adsorption isotherms and the single curve obtained afterrnnormalization of the isotherms at various salinities suggests a consistentrnmechanism of adsorption that is independent of salt concentration. Thesernsimilarities also suggests that there may be an upper limit to nonionicrnsurfactant adsorption so that after some maximum electrolyternconcentration little additional adsorption occurs.