Bandgap tuning of TiO₂ by Cu nanoparticles applied in photocatalytic antifouling-coated PES membranes through PAA-plasma grafted adhesive layer

This study has tuned the bandgap of TiO2 with Cu nanoparticles (NPs) to apply as an antifouling coating on polyethersulfone (PES) membranes through polyacrylic acid (PAA)-plasma-grafted intermediate layer. Cu NPs were chemically reduced from Cu2+ ions by ascorbic acid and simultaneously precipitated onto TiO2 by the sol-gel method at molar ratios of 1, 3, 5, 10, 15, and 25%. Cu@TiO2 photocatalysts have been characterized by methods such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy-energy-dispersive X-ray spectroscopy (TEM-EDS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron spin resonance (ESR) spectroscopy, which shows that Cu@TiO2 photocatalysts have been successfully synthesized with reduced bandgap, particle size in the range of 50-150 nm, generation of reactive free radicals under light irradiation, etc. The 25% Cu@TiO2 photocatalyst gave the highest catalytic efficiencies for Acid Blue 260 (AB260) degradations with and without H2O2 at 73 and 96%, respectively. Photocatalytic membranes based on this catalyst give an AB260 degra-dation efficiency of 91% and are stable over five continuous cycles. Sodium alginate-fouled photocatalytic membranes have fully recovered water permeability after undergoing photocatalytic degradation of foulants. In addition, the AFM analysis results show that the modified membrane has a higher surface roughness than the pristine PES membrane due to the presence of photocatalyst particles on the membrane surface.