Adsorption of cationic-anionic surfactant mixtures on silica gel/water and silica gel/mineralized water interfaces

The adsorption of cationic-anionic surfactant mixtures (dodecylpyridinum chloride/sodium octylsulfonate and octyltriethylammonium bromide/sodium dodecylbenzenesulfonate) on silica gel/water and silica gel/mineralized water interfaces was investigated. The effects of anionic (cationic) surfactants on the adsorption of cationic (anionic) surfactants were discussed. It was shown that the existence of anionic surfactant did not affect the adsorption of cationic surfactants on negatively charged solid surface, but the anionic surfactant, which had low amount adsorbed on negatively charged solid surface, was no longer adsorbed with the existence of cationic surfactant. The amount adsorbed of the cationic surfactant was much lower in mineralized water solution than in water solution. The results were explained based on the adsorption mechanism of silica gel.