A fundamental study of adsorption kinetics of surfactants onto metal oxides using quartz crystal microbalance with dissipation (QCM-D)

Hypothesis Membrane fouling challenges the viability of oil-field produced water (PW) treatment with ceramic membranes. Surfactants play an important role in irreversible fouling through adsorption phenomena. However, previous studies have shown contradictory results. Hence, a fundamental understanding of surfactants-metal oxides interactions is necessary. Experiments In this work, we assessed the adsorption interactions of anionic SDBS and cationic CTAB with titania, zirconia and alumina surfaces, using the quartz crystal microbalance with dissipation (QCM-D) technique. Findings We found that electrostatic interactions controlled the adsorption of SDBS onto all the surfaces studied, with titania being the most likely to adsorb SDBS. On the contrary, CTAB was adsorbed regardless of the overall metal oxide surface charge. CTAB showed a two-step adsorption at acidic pH (3.0). In the first step, a rigid film was formed with a smaller adsorption capacity compared to the neutral (6.8) and basic (9.4) pH conditions. In the second step, a viscoelastic film was formed. Our results suggest that adsorption was driven by the nature of the surfactant rather than the metal oxide properties. This implies that electrostatic interactions should not be taken as the only predicting factor of adsorption phenomena in the understanding of PW fouling in ceramic membranes as other supramolecular interactions are strongly involved.