Confining migration of amine monomer during interfacial polymerization for constructing thin-film composite forward osmosis membrane with low fouling propensity

Abstract

Abstract Forward osmosis (FO) membrane is paramount to the progress and implementation of FO process. However, typical FO membranes are confronted with many unsatisfactory issues, including the low water flux, high fouling propensity and the poor long-term operation stability in most cases, which confines the practical application of FO process to a large extent. This study proposes a feasible way to mitigate the internal concentration polarization (ICP) and optimize the polyamide (PA) layer structure of as-fabricated thin-film composite forward osmosis (TFC-FO) membranes simultaneously by incorporating phosphorylated titanium dioxide ( p -TiO 2 ) in polyvinylidene fluoride (PVDF) substrate. P -TiO 2 nanoparticles with abundant phosphate groups were prepared through a chemical absorption approach followed by the thermal post-treatment. Superior water flux and the better antifouling properties of the resultant PVDF/ p -TiO 2 TFC-FO membrane was achieved, taking advantage of the more compact and smoother PA layer as a result of the confined migration of amine monomer during interfacial polymerization (IP). In addition, effects of p -TiO 2 content on morphological changes and physicochemical properties of modified substrates and the construction of top PA layer are studied and elaborated systemically via many characterizations as well as the permeation tests. As a result, the water flux decline of PVDF/ p -TiO 2 TFC membrane is much lower (16.0 %) than that (∼31.3 %) of the pristine TFC membrane, in the long-term (20 h) dynamic fouling test against 500 ppm humic acid (HA) solution. Therefore, PVDF/ p -TiO 2 TFC-FO membrane with improved water flux and low fouling tendency is beneficial for wastewater treatment and desalination process, especially for the treatment of brackish water with high fouling tendency or under harsh conditions.