Fouling resistance of 3-[[3-(trimethoxysilane)-propyl] amino] propane-1-sulfonic acid zwitterion modified poly (vinylidene fluoride) membranes

Abstract

Zwitterion polymer modified membranes have demonstrated fouling resistance in wide applications. The ubiquitous success in scientific progress, however, has not yet brought significant breakthrough in the application of such membranes in wastewater treatment. Limitation of zwitterion materials in membrane is seldomly discussed. In this paper, we aimed to bring an engineering view on the pros-and-cons of zwitterion modified microfiltration membrane in treating solutions containing humic acid (HA) and bovine serum albumin (BSA). A 3-[[3-(trimethoxysilane)-propyl] amino] propane-1-sulfonic acid (TMAPS) grafted zwitterionic PVDF membrane was selected as a model membrane. The membranes were prepared via a two-step “hydroxylation-grafting” method; surface modified PVDF membrane was transformed from hydrophobic to hydrophilic with significant improvement in pure water flux. An 87% increase was obtained in the stable flux for the grafted membrane when treating HA, but very similar flux pattern to the pristine one was found when treating BSA. The membrane resistance model showed that cake layer was the main fouling factor for both foulants. For HA, the cake layer blocking model predicted the membrane flux well; but for BSA, the intermediate blocking model fits best the experimental results. Zwitterion grafted surface failed to show improvement in the fouling resistance even at very low BSA feed concentration. Adsorption experiment indicated that the interaction of BSA to membrane is significantly stronger than HA and membranes independent from the surface characteristics. Present work clarified the limitation of zwitterion modified membranes in treating solutions containing HA-like and protein matters.