Preparation and evaluation of poly(vinylidene fluoride)-sulfonated poly(1,4-phenylene sulfide) based membranes with improved hydrophilicity

Poly(vinylidene fluoride) (PVDF) based water purification membranes exhibit excellent thermal stability and chemical resistance, but also possess inherent drawbacks such as severe membrane fouling, lower separation efficiency and water flux due to its hydrophobic nature. In the present study, we attempted to enhance the hydrophilicity of PVDF membranes by treating with varying content (0 to 3 wt%) of partially sulfonated poly(1,4-phenylene sulfide) (sPPS) component using phase-inversion process. Compared to neat PVDF membrane, the PVDF/sPPS blend membranes exhibited typical asymmetric morphology with larger finger-like pores, efficient distribution of hydrophilic SO 3 - groups and decreasing water contact angle (WCA) upto 62° (77° for neat PVDF) as confirmed from scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and contact-angle measurements, respectively. Studies carried out for pure water flux (880 L/m 2 h) and blood serum albumin (BSA) solution flux (185 L/m 2 h) confirmed the enhanced permeability and higher fouling resistance for PVDF-sPPS (3 wt% sPPS) membranes compared to neat PVDF membrane (175 L/m 2 h and 63 L/m 2 h, respectively), though the BSA flux decreased with an increase in the filtration time due to membrane fouling. Compared to the total organic carbon (TOC) values of poly(ethylene oxide) (PEO) aqueous solutions before permeation (189.9 mg/L for M w =100,000 and 75.68 mg/L for M w =300,000), TOC of neat PVDF membrane decreased to 15 mg/L for M w = 100,000 and 5 mg/L for M w =300,000. With increasing sPPS content, the TOC values showed an increasing trend due to their increasing pore size. Overall, the incorporation of sPPS in PVDF membrane lowered the WCA, enhanced fouling resistance and improved its permeability and selectivity, which exemplifies the importance of this study.