Fabrication of photocatalytic membrane and evaluation its efficiency in removal of organic pollutants from water

TiO2/Al2O3 composite membranes with photocatalytic capability have been successfully prepared from colloidal titania sols by the sol-gel technique. Pore sizes of the resulting membrane were mainly controlled by the sol properties and the immersion time. A preliminary investigation of the sol-gel process, the membrane characterization and the stability of composite membrane were carried out using IR-spectra, scanning electron microscopy (SEM), X-ray diffraction (XRD). The results proved that TiO2 immobilized on the support of Al2O3 had anatase crystal structure in the calcination temperature range. Direct Black 168 was used as the test pollutant for investigation of the multifunctions of photocatalysis and separation of TiO2/Al2O3 composite membrane. Some operational parameters such as the pressure in the membrane cell, the initial pH and air flow were determined and the influence of various parameters was also discussed to obtain high reaction rates, high membrane rejection and operating stability. The removal of Direct Black168 with UV irradiation alone achieved 70% and the retention of the dye with membrane filtration alone reached 65% after 300 min in the continuous system. By combining the photocatalysis with membrane techniques, the removal efficiency of the dye was improved markedly and reached 82% after 300 min. Although the dye was not completely decomposed by photocatalysis, the degradation of the dye helped to enhance the composite membrane flux and prevent membrane fouling. It was possible to treat successfully Direct Black168 solutions (100 mg/L) by means of a continuous process obtaining good values of permeate fluxes (82 L/m(2) h). The TiO2/Al2O3 composite membrane with photocatalytic function could be interesting for water purification. (C) 2005 Elsevier B.V. All rights reserved.