Investigation on the conditions mitigating membrane fouling caused by TiO2 deposition in a membrane photocatalytic reactor (MPR) used for dye wastewater treatment

In this study, the effects of MPR's operating conditions such as permeate flux, solution pH, and membrane hydrophobicity on separation characteristics and membrane fouling caused by TiO2 deposition were investigated. The extent of fouling was measured in terms of TMP and tank turbidity variation. The results showed that, at mildly acidic conditions (pH similar to 5), the turbidity within the tank decreased and the extent of turbidity drop increased with increasing flux for all the membranes. On the other hand, at pH >= 7, the turbidity remained constant at all flux and for all membranes tested. The fouling variation at different pH was closely linked with the surface charge (zeta potential) and hydrophilicity of both membrane and particles. It was observed that the charge differences between the particles and membranes accelerate the intensity of fouling and binding of TiO2 particles on the membrane surface under different pH conditions. The presence of a very thin layer of TiO2 can alter the hydrophilicity of the membranes and can slightly decrease the TMP (filtration resistance) of the fouled membranes. Besides, the resistance offered by the dense TiO2 cake layer would dominate this hydrophilic effect of TiO2 particles, and it may not alter the filtration resistance of the fouled membranes. (C) 2011 Elsevier B.V. All rights reserved.