Influence of azo dye-TiO2 interactions on the filtration performance in a hybrid photocatalysis/ultrafiltration process

Filtration performances of hollow fiber ultrafiltration membrane were investigated in a photocatalysis/ultrafiltration process used for dyeing wastewater treatment. Special attentions were focused on the dye-TiO2 interactions and their effect on membrane flux and dye rejection. Solution pH was proved to be the predominant force that controlled the interactions by changing the surface charge characteristics of TiO2 and altering the size and fractal dimension of TiO2 aggregates which determined the property and structure of deposit layer. Dye-TiO2 interaction had pronounced effect on membrane flux in adsorptive regions, but this effect became insignificant in non-adsorptive regions. The rejection of dye in the presence of TiO2 was found to decrease markedly due to the deposition of TiO2 particles on membrane interface. Bridging effect of TiO2 between membrane interface and dyes produced by electronic interaction, coordination, and hydrogen bonding was responsible for the decrease in dye rejection. In view of the results presented in this paper, the interactions between pollutant and photocatalysts and their effect on the performance of membrane in hybrid photocatalysis/membrane process should be taken into consideration in the future practice. (C) 2012 Elsevier Inc. All rights reserved.