Elaboration and study of poly(vinylidene fluoride)–anatase TiO 2 composite membranes in photocatalytic degradation of dyes

Abstract

Porous PVdF-based membranes filled with anatase (TiO 2) nanocrystalline particles were prepared by using a new phase inversion technique for entrapment of TiO 2. 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 TiO 2 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 TiO 2/PVdF weight ratio. The original porous TiO 2/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 TiO 2 particles in the internal structure accessible to the external medium. The adsorption capacity of the TiO 2/PVdF membrane was studied with the aqueous solutions of Brilliant Green (BG) and Indigo Carmin (IC) dyes, and the photocatalytic efficiency of TiO 2 immobilized in PVdF was compared with that of the conventional TiO 2 Degussa P25 catalyst. The rate of TiO 2/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 TiO 2. 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.