Titanium dioxide coated polyetherimide photocatalytic nanofiber membrane for water treatment

Abstract

Access to clean water for human use is a growing concern across the world with the ever-increasing human population. Treatment of wastewater to produce usable water is essential to meet future clean water demand. Separation and decontamination processes using membrane technologies have been implemented worldwide. Photocatalytic membrane is an emerging technology that is capable of simultaneously separating and degrading organic pollutants (e.g., humic acid (HA) and dyes) present in aqueous solution under UV-irradiation besides microorganism disinfection. In view of this, the main objective of this work is to fabricate and characterize a new type of nanocomposite nanofiber membrane by incorporating photocatalytic nanomaterials – titanium dioxide (TiO2) into a highly porous nanofiber made of UV-resistant polyetherimide (PEI). The nanofiber membrane was fabricated via an electrospinning method using a dope solution containing 15 wt% PEI dissolved in a mixed solvent of dimethylformamide (DMF)/n-methyl-2-pyrrolidone (NMP) with ratio of 2:8. The top surface of nanofiber membrane was further modified by coating it with different TiO2 concentration (0.2 and 0.6 wt%) using electrospraying method. The properties of the TiO2-modified PEI nanofiber membranes were then analysed using scanning electron microscope (SEM), water contact angle (WCA) goniometer and tensile strength machine. Results showed that 0.2 wt% TiO2-modified PEI nanofiber displayed better behaviour by reducing WCA of unmodified nanofiber from 130.25° to 23.35° and improving water flux by 28%. Although the WCA of membrane was further reduced when a higher TiO2 amount (0.6 wt%) was used, the resultant nanofiber suffered from decreased ultimate strength and significant nanoparticles leaching. Using the best performing 0.2 wt% TiO2-modified PEI membrane, significant removal rate of Escherichia coli (99%) and humic acid (~80%) could be achieved along with 85% methylene blue degradation during photocatalytic process. The findings of this work provide an insight into the design of advanced nanocomposite nanofiber membrane for photocatalytic process.