Effect of process parameters on fouling and stability of MF/UF TiO2 membranes in a photocatalytic membrane reactor

The investigations on the influence of TiO2 photocatalyst (Aeroxide® TiO2 P25) loading, feed cross-flow velocity (vF) and transmembrane pressure (TMP) on the fouling and stability of ceramic membranes in a photocatalytic membrane reactor are presented. Two ultrafiltration membranes with molecular weight cut-off of 5 kDa (Filtanium 5) and 100 kDa (Filtanium 100), and one microfiltration membrane (Filtanium 0.2) with maximum pore size of 0.2 μm were used. Regardless of the applied vF (3-6 m/s), TMP (1-3 bar) and TiO2 P25 loading (0.5-1.5 g/dm3) no permeate flux decline was observed when the UF membranes were used. On the opposite, an increase of the flux for 5-10% compared to pure water flux due to abrasion of the membranes separation layer by TiO2 P25 particles was found. In case of MF membrane a significant influence of vF and TMP on permeate flux was observed. Application of vF = 3 m/s led to a significant membrane fouling while at vF = 6 m/s the permeate flux exceeded pure water flux in the whole range of TMP. The fine UF Filtanium 5 membrane lost its separation properties due to abrasion by TiO2 P25 particles, whereas the performance of the ordinary UF Filtanium 100 membrane did not change during 100 h of operation in the PMR. Additionally, the influence of a commercial TiO2 ST01 (Ishihara Sangyo, Japan) and laboratory made A700 (anatase) and A800 (rutile) on the permeate flux through Filtanium 100 membrane were assessed. The difference between the lowest and the highest values of the permeate fluxes measured for various TiO2 materials did not exceed 12%.