Static adsorption of protein-polysaccharide hybrids on hydrophilic modified membranes based on atomic layer deposition: Anti-fouling performance and mechanism insight

Abstract

Initial membrane fouling affects fouling behavior and characteristic significantly. Static adsorption investigation contributes to intensively understand the initial fouling process. In order to determine the superior anti-fouling material prepared by atomic layer deposition, the TiO2, Al2O3 and ZnO modified membranes were successfully fabricated, characterized by XPS, XRD and SEM and then employed for static adsorption of BSA and SA foulants. More importantly, the anti-fouling mechanism was interpreted by adsorption isotherms and thermodynamics. Results showed that the adsorption amount of BSA and SA on PVDF membrane decreased by 43.2% and 73.0% with ZnO modification, reaching the highest among all the modified membranes. As a consequence, the minimum reduction of pure water flux and increase of membrane resistance were realized after fouling. The Sips model presented the most satisfactory fitting for BSA and SA adsorption on ZnO modified membrane. Thermodynamic investigation revealed that the ZnO modified membrane exhibited the lowest degree of spontaneity and the weakest interaction with foulants (London dispersion forces of physisorption). Moreover, the smallest ΔS value indicated the regular distribution of foulants on membrane surface, which greatly alleviated membrane fouling. The relatively smooth surface of ZnO modified membrane with lower roughness and water contact angle confirmed the excellent anti-fouling property. The reported results in this study could provide fundamental basis for the anti-fouling performance of ALD modified membranes, which would accelerate the actual application process.