Iron oxide modified polyethersulfone hollow fiber membranes with improved hydrophilicity for water treatment

Abstract

Rapid industrialization has led to deterioration of water quality due to the increase in improper discharge of wastewater into receiving water body. Over the years, membrane technology has emerged as a potential alternative to treat various types of water and wastewater. However, fouling and flux declination are still the major hindrances for the membrane application. To address this issue, the aim of this work was to develop a hollow fiber membrane with improved surface properties via incorporation of hydrophilic nanoparticles for water application. The objective of this work is to investigate the impacts of particle size of iron oxide (Fe3O4) and the effects of different surface-functionalized Fe3O4 nanoparticles on the properties of polyethersulfone (PES) hollow fiber membranes for ultrafiltration process. All of the membranes were synthesized via a dry-jet wet spinning process followed by a series of instrumental characterization before proceeding to filtration performance assessment. The results showed that the addition of smaller Fe3O4 particles (50 nm) into PES dope solution could produce a membrane with better hydrophilicity (contact angle: 75.77°) and consequently better pure water flux (PWF) (102.74 L/m2.h.bar) compared to the pristine PES membrane (82.55 L/m2.h.bar) and membrane incorporated with larger Fe3O4 particles of 5 µm (91.55 L/m2.h.bar). This is due to better particle dispersion in the PES matrix that subsequently enhances the membrane permeability. In addition, the membrane modified by 50-nm Fe3O4 also displayed good filtration performance by rejecting 80.43% bovine serum albumin (BSA) from aqueous solution. Surface coating of 50-nm Fe3O4 nanoparticles using polydopamine (PDA) could further improve its dispersion and stability in dope solution, leading to improved membrane performance. Compared to the membrane incorporated with neat Fe3O4, the addition of PDA-coated Fe3O4 into PES membrane showed 17.58% improvement in water flux and 6.08% higher BSA rejection, reaching 121.19 L/m2.h.bar and 85.32%, respectively. This can be attributed to the improvement in terms of membrane hydrophilicity and porosity. The incorporation of dual functionalized Fe3O4 into PES membrane using amine were found to greatly promote membrane permeability compared with using sulfonic acid due to enhanced synergistic interaction between Fe3O4/PDA-amine and PES polymer. The PES/Fe3O4/PDA-amine membrane recorded the highest PWF of 137.15 L/m2.h.bar and BSA rejection of 92.16%. This membrane also achieved excellent chemical oxygen demand (95.17%) and color reduction (89.86%) when tested using river water sample. In conclusion, the developed PES/Fe3O4/PDA-amine membrane showed an excellent separation performance and antifouling property for water treatment, overcoming the drawbacks of PES membrane.