Surface modification of novel polyether sulfone amide (PESA) ultrafiltration membranes by grafting hydrophilic monomers

In this study, new polymeric material namely polyether sulfone amide (PESA) containing hydrophile group was synthesized via polycondensation reaction of diamine with dicarboxylic acid. Synthesized PESA was used as main polymer to fabrication of novel PESA UF membranes to improve the membrane properties especially in view of fouling reduction. The PESA membrane was modified by grafting two hydrophilic monomers i.e. 3,5-diaminobenzoic acid (DBA) and gallic acid (GA) via interfacial polymerization. The prepared membranes were characterized by contact angle measurement, equilibrium water content (EWC), scanning electron microscopy (SEM), atomic force microscopy (AFM), FTIR-ATR analyses. Membrane performance was evaluated by measuring the pure water flux and humic acid (HA) solute separation with dead-end filtration system. As a result, the contact angle measurement showed that the PESA membrane had high hydrophilic surface. Also, super hydrophilic surfaces were introduced by grafting DBA and GA on the surface of PESA membrane. The SEM images proved the formation of large finger-likes in the sublayer for PESA membrane. Filtration tests showed that pure water flux and HA solution flux of the PESA membranes were higher in comparison to the PES membrane. Although fluxes were obviously decreased after grafting monomers onto the PESA membrane surface, higher HA separation efficiency was achieved. Meanwhile fouling tendency was decreased. All these results indicated that the new PESA modified membranes showed superior performance compared to the PES membrane. Furthermore, GA was found to be the most effective hydrophilic monomer to improve the membrane hydrophilicity and fouling resistibility.