Adsorption of Sulfonate on Kaolinite and Alumina in the Presence of Gypsum

ABSTRACT Loss of surfactants by adsorption and precipitation that can occur during enhanced oil recovery by micellar flooding is a complex phenomenon dependent not only on solution properties such as pH and salinity, but also on the presence of even minor mineral constituents such as gypsum and limestone. In this paper, the results on adsorption of isomerically pure decyl-benzenesulfonate on gypsum, kaolinite and alumina are presented. Sulfonate abstraction by kaolinite and alumina in the presence of trace amounts of gypsum is also determined. Adsorption of sulfonates varied significantly from mineral to mineral. Gypsum exhibited a sharp increase in adsorption above 4-6×10−5 kmol/m3 of residual sulfonate. Tests using the supernatant of gypsum showed sulfonate precipitation by the dissolved mineral species to be a major factor responsible for the high uptake. A thermodynamic analysis of the solubility and stability characteristics of gypsum and anhydrite is presented. The sharp rise in abstraction has been shown to correspond to the onset of sulfonate precipitation. Presence of trace amounts of gypsum either with alumina or kaolinite is found to markedly increase the sulfonate uptake by these minerals. It is shown that in kaolinite-gypsum and alumina-gypsum mixtures, the total abstraction at high sulfonate levels is due to adsorption on alumina and kaolinite and precipitation caused by gypsum.