Ultrafiltration Polyethersulfone Membranes Fabrication Through Incorporating Cationic and Anionic Functional Polymers with Enhanced Antifouling and Water Flux

Abstract

Polyethersulfone (PES) membrane is widely employed for ultrafiltration of wastewater owing to its robustness, structural and chemical durability, and convenient modifiability. Regrettably, these membranes are predominantly hydrophobic, making them extremely prone to fouling. Surface modification of membranes is one among several techniques for controlling fouling. This study aims to develop and prepare PES membranes that are resistant to fouling through phase inversion method by blending with two different polymers as additives. The performance of fabricated membranes was studied in terms of pure water flux, porosity, water uptake and bovine serum albumin (BSA) rejection tests. Antibacterial activity of fresh prepared membranes was also investigated by using disc diffusion method. These objectives were achieved by adding varying percentages of water-soluble cationic poly [2- (dimethyl amino) ethyl methacrylate] (PDMAEMA) and anionic hydrophilic polymer, poly (3-Sulfopropyl methacrylate (PSPMA) as additives to uniform casting solutions of PES. The modified membranes exhibited a direct correlation between the concentration of PDMAEMA or PSPMA and increase in the volumetric water flux. Under a constant pressure of 0.2 MPa, fabricated membranes with 3 % PDMAEMA exhibited a pure water flux value of 330.39 L. m₋2.h-1, significantly surpassing the pure water flux of 163.158 L. m₋2.h-1 observed in the pristine PES membrane. Similarly, the pure water flux for the PES/PSPMA was 154.18 L. m₋2.h₋1 which is much higher than pure PES membrane (103.52 L. m₋2.h₋1). For all the developed membranes, increasing the pressure led to improved filtration performance, as for PDMAEMA (3%), water flux was found 65 L. m₋2.h-1 at 1.0 MPa and 560 L. m₋2.h-1 at 0.35 MPa applied pressure. Membranes with the highest percentage of the PDMAEMA and PSPMA exhibited a greater flux Recovery Ratio (FRR), and superior total fouling ratio (TFR) compared to the membranes without these additives. This was evaluated by employing BSA xviii as a representative protein. The developed PES/PDMAEMA membranes with 3.0 wt.% PDMAEMA at 0.2 MPa applied pressure, exhibited a TFR of 36 % in comparison with the neat PES membranes having TFR of 64.9 %. While the TFR of neat PES and PES/PSPMA membranes was 25.7% and 44.6% respectively. The findings demonstrated that there was an increased rejection of BSA when the concentration of these hydrophilic polymers in the mixture was increased. The modified membranes exhibit exceptional antimicrobial efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) when tested using disc diffusion technique, rendering them well-suited for water treatment applications Overall, the addition of PDMAEMA and PSPMA in the PES membrane system significantly improved its ability to achieve better antifouling properties as well as better filtration performance. This approach can be extended to develop different homopolymers and copolymer additives for the same applications such as heavy metal removal, affinity filtration, and desalination.