Elaboration and study of poly(vinylidene fluoride)–anatase TiO2 composite membranes in photocatalytic degradation of dyes Original Research Article

Porous PVdF-based membranes filled with anatase (TiO2) nanocrystalline particles were prepared by using a new phase inversion technique for entrapment of TiO2. The prepared samples were characterized by scanning electron microscopy, thermal gravimetry analysis, and contact angle measurements. The SEM investigation showed a fair distribution in the membranes of the TiO2 particles, mainly in aggregate form. The best photocatalytic membrane had a pore size of 0.96 μm, with a maximum porosity of 86% at 0.5 TiO2/PVdF weight ratio. The original porous TiO2/PVdF membranes showed a very weak degradation ability of dyes in an aqueous medium due to their poor wetting. We showed that a prior membrane conditioning in ethanol increased the membrane wetting, thus the dye degradation rate by making the TiO2 particles in the internal structure accessible to the external medium. The adsorption capacity of the TiO2/PVdF membrane was studied with the aqueous solutions of Brilliant Green (BG) and Indigo Carmin (IC) dyes, and the photocatalytic efficiency of TiO2 immobilized in PVdF was compared with that of the conventional TiO2 Degussa P25 catalyst. The rate of TiO2/PVdF membrane degradation photocatalytic was 6.1 and 2.4 μmol L−1 min−1 for IC and BG respectively, against 8.7 and 5.9 μmol L−1 min−1 for the P25 TiO2. The Langmuir-Hinshelwood model was adequate to describe the rate of dye degradation only when the amount of dyes adsorbed on photocatalytic material is significant.