Immobilization of TiO2 and TiO2-GO hybrids onto the surface of acrylic acid-grafted polymeric membranes for pollutant removal: Analysis of photocatalytic activity

The grafting polymerization was used to prepare the nanocomposite photocatalytic membranes. The surface of a microporous hydrophobic poly(vinylidene fluoride) (PVDF) membrane was first activated by argon plasma. By generation of free radicals after plasma exposure, the GO and TiO2 nanoparticles were successfully coated on the membrane surface after grafting with acrylic acid (AA). Photocatalytic activity of the TiO2-GO hybrids represents efficiently under UV irradiation. Here, the excitation of TiO2 leads to the transition of electrons (e−) from valence band to conduction band leaving holes (h+). These holes then react with water molecules generating ⋅OH radicals. While electron reacts with oxygen molecules releasing ⋅O2- radicals, which can move to GO sheets. The generated radicals (⋅OH and ⋅O2-) can readily decompose the pollutant. The trapping of electrons in GO sheets prolongs the life-time of electron-hole pairs which enhances photocatalytic activity of the composite membrane. [Display omitted] •GO and TiO2 were immobilized on plasma-activated PVDF membrane surface after grafting by acrylic acid.•The concentration of acrylic acid (AA) played a key role in coating of GO and TiO2 onto the membrane.•The generated electrons trapped by GO sheets inhibited the rate of the recombination of hole-electron pairs.•Tests of impedance, photocurrent, and phenol degradation all revealed high photoactivity of the membrane. The nanocomposite titania@graphene oxide (TiO2-GO) hybrids were prepared to achieve the photocatalysis synergy after they were immobilized onto the surface of hydrophobic microporous poly(vinylidene fluoride) (PVDF) membranes. The immobilization of TiO2 and TiO2-GO hybrids was followed after the membrane was plasma-activated and was grafted with acrylic acid (AA). The crystal structure, morphology, chemical composition, and hydrophilicity of such photocatalytic membranes were analyzed. The rate of the recombination of electron-hole pairs generated by the composite membranes under UV irradiation was also determined from electrochemical impedance spectra and photocurrent measurements. The photocatalytic activity of TiO2 and TiO2-GO hybrids on the membranes was examined under UV illumination, particularly at different AA concentrations in the grafting solution (20, 30, and 40 vol% in isopropanol) and different compositions of the TiO2-GO hybrids (0, 25, 50, and 75 wt.% of GO. It was shown that the AA concentration played a crucial role in the attachme