Abstract
Plasma-enhanced chemical vapor deposition is applied to prepare amorphous TiO2 thin films at low temperature. Post-annealing at 300 °C for minimal staying time 4.5 h is required to form crystalline anatase phase. Characteristics of the TiO2 thin films including crystalline structure, microstructure, band gap and surface hydrophilicity, are determined. Functional performance of these anatase thin films as photocatalysts is first examined with patented Pilkington assessment by removing, under UV irradiation, stearic acid initially adsorbed on TiO2 layers here deposited on silicon wafers. Membranes M100 (TiO2 continuous layer) and M800 (TiO2-skin on support grain) are prepared on the macroporous top layer of porous alumina supports with an average pore size of 100 nm and 800 nm, respectively. These membranes are tested in “static” condition under the effect of diffusion of an organic solute in water. For Methylene Blue it is shown that the quantity of destroyed compound per unit of membrane surface area and per unit of time is equal to 2×10−8 mol m-2 s-1 for M100 and 1×10−8 mol m-2 s-1 for M800. These membranes are also tested in “dynamic” conditions, i.e. pressure-driven membrane processes, with two different configurations (photocatalytic layer on the feed side or on the permeate side) and three different organics (Methylene Blue, Acid Orange 7 and phenol). Process modelling (adsorption and photocatalysis reaction) is finally carried out from the available experimental outputs.