In order to investigate the photocatalytic degradation of phenol and methylene blue (MB) in aqueous solutions containing TiO2 nanoparticles with different particle sizes and crystalline phases, an integrated membrane process combining microfiltration (MF) and ultrafiltration was introduced for the production and size separation of TiO2 nanoparticles. TiO2 nanoparticles obtained were characterized by XRD, TEM, SEM and BET techniques. The characterization results show that TiO2 nanoparticles with various sizes and BET surface areas were obtained after MF fractionation. The size of TiO2 nanoparticles from large to small follows the order: the retentate > the feed > the permeate while the sequence of BET surface area follows the order: the permeate > the feed > the retentate. Furthermore, a smaller disperse coefficient was achieved for both the permeate and the retentate in comparison with the feed. The studies on the photocatalytic oxidation of phenol and MB with TiO2 nanoparticles before and after MF fractionation concluded that both the particle size and crystallite phase had strong influence on their photocatalytic performances. (C) 2009 Elsevier B.V. All rights reserved.