(35c) Fouling Free Hydrophilic Polysulfone Ultrafiltration Membranes

This work describes the preparation of hydrophilic polysulfone (PSF) ultrafiltration membranes having reduced fouling tendency and increased separation performance. The various additives used in this study are hydrophilic polymers, namely poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (AMPS), poly(ethylene glycol) (PEG) and polymer nanocomposites viz. titanium dioxide- poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (TiO₂-AMPS). Direct blending technique is used for these additives and membranes are prepared by phase inversion method. The membranes are then characterized for their morphological and permeation characteristics by using different characterization techniques. Field emission electron microscopy (FESEM) is used for the structural analysis of the membranes and analysis of flux profiles for the permeability assessments. Fourier transform infrared spectroscopy (FTIR) is used for the confirmation of the presence of the additives in the prepared membranes. Lastly, antifouling and separation efficiencies are tested with humic acid (HA) solutions. The membranes modified with hydrophilic polymers (entitled M1) have shown narrow pore size (2.31-7.91 nm) as compared to the membranes (entitled M2) modified using polymer nanocomposites (16.27-21.30 nm). These differences can also be seen from the FESEM micrographs of the membranes. The FTIR analysis of the membranes confirms the successful incorporation of the additives in the membranes. Also, the hydrophilicity of the membranes increases for both M1 and M2 membranes on addition of hydrophilic additives. This is confirmed by the decreasing water contact angle of the membranes, for M1 membranes it is decreased from 72.12° (M1_0) to 40.32° (M1_4) and 71.71° (R1) to 36.56° (R4) for M2 membranes. Further, the M1 shows better separation characteristics, when analyzed with HA (98.93% removal) solutions as compared to M2 membranes (92% removal). This is due to the better surface presence of the polymeric additives and narrow pores size range of the membranes. On the other hand, M2 membranes shows better antifouling nature (F_RR from 47.23 (R1) - 67.25 (R4)) compared to M1 membranes (F_RR from 48.63 (M1_0) - 52.11 (M1_4)). However, the overall comparison shows that the membranes modified with polymer nanocomposites are best in performance due to the synergistic effect of both the polymer as well as the nanoparticles present in a polymer nanocomposite. The membranes prepared in this study are suitable for the treatment of contaminated drinking water and industrial wastewater as well.

Keywords: Polysulfone, ultrafiltration, phase inversion, hydrophilic and antifouling, polymer nanocomposites