Nature based forward osmosis membranes: A novel approach for improved anti-fouling properties of thin film composite membranes

Herein, polyamide thin-film composite forward osmosis (TFC-FO) membranes were fabricated using beta-cyclodextrin-graft-poly acrylic acid (ß-CD-g-PAA), as a nature-based graft polymer. The polymer was synthesized by free radical graft polymerization and was consequently incorporated into the active layer to enhance the hydrophilicity, anti-fouling, and overall performance of the conventional TFC-FO membrane. The effect of synthesized polymer concentration on characteristic features such as roughness, morphology, and hydrophilicity of the polymer-modified membranes was thoroughly investigated using different characterization techniques. Apart from that, the separation performance of the newly developed membranes was investigated in FO and reverse osmosis (RO) filtration systems. The transport data revealed increased water flux of around 1.5 times for the membrane which was modified with 1250 ppm of ß-CD-g-PAA solution (TFC-1250) compared to pristine TFC in the FO mode. Interestingly, the mentioned membrane showed demonstrably perm-selectivity of 0.043 bar in RO filtration system. The antifouling investigations of the TFC-1250 membrane against protein and organic foulant in FO mode, not only showed minor fouling tendency, but also revealed great flux recovery ratio (FRR>98%) with a simple washing step. These observations prove the reversible characteristic of fouling in FO process. Hence, this project opens a new way to surface functionalization of TFC membranes with nature-based polymers to render selectivity as well as antifouling features to them.