Self-assembling of NCQDs-TiO2 nanocomposite on poly(acrylic acid)-grafted polyethersulfone membrane for photocatalytic removal and membrane filtration

Abstract

Considering the tedious post-reaction recovery of nano-sized phototcatalysts and the critical fouling problem faced in membrane separation, incorporation of photocatalyst with polymeric membrane has been developed to alleviate these issues. In this study, polyethersulfone (PES) membrane was synthesized by phase inversion method and poly-acrylic acid (PAA) was later grafted onto the PES surface via UV-induced graft polymerization technique. The PAA film has introduced –COOH functional groups for the surface immobilization of green nitrogen-doped carbon quantum dots-titanium dioxide (NCQDs-TiO2) photocatalyst via a self-assembly approach. The PAA-modified supporting layer and the NCQDs-TiO2 functional layer were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). The characterization results evidenced that PAA chains were successfully polymerized on PES support while the nanocomposite was firmly deposited on the PAA-grafted membrane. The novel NCQDs-TiO2/PAA/PES composite membrane demonstrated excellent photocatalytic capability, wherein 94.41% of methylene blue (MB) was removed under 1 h of visible-light irradiation. The antifouling property of the modified membrane was proven by the rapid flux stabilization and the high flux recovery ratio of 83.92%. The current research work proposed the synergistic use of visible-light responsive photocatalytic membrane in the degradation and filtration of wastewater, which is more energy-efficient and could reduce secondary pollution.