Zwitterion augmented polyamide membrane for improved forward osmosis performance with significant antifouling characteristics

Zwitterion augmented forward osmosis (FO) membranes were fabricated having polyamide active layer on the polysulfone support to improve the overall performance and antifouling characteristics. FTIR and XPS were employed in evidencing the incorporation of zwitterion in terms of functional groups and relative compositions of hetero atoms. AFM, SEM, water contact angle and zeta potential measurement are used to characterize the zwitterion augmented surface in terms of surface morphology, surface charge and hydrophilicity/hydrophobicity. Augmentation of zwitterion was found to enhance the hydrophilicity and surface roughness resulting the enhancement in the water permeability. The anionic moiety of the zwitterion was exposed outside, while the cationic moieties of the zwitterion mostly retained towards the core as suggested by negative zeta potential and protein absorption. Incorporation of zwitterion was found to enhance the antifouling property of the membrane as evident from static and dynamic test. The relative composition of zwitterion on active membrane surface was optimized by investigating the tradeoff between water permeability and reverse salt flux.