Robust and stable TiO2/Al2O3–SiO2 membrane with enhanced flux and antifouling performance for organic dye removal

Abstract

Al₂O₃–SiO₂ membranes were modified with a titanium source, tetrabutyl orthotitanate (TBOT), using the sol–gel method to prepare TiO₂/Al₂O₃–SiO₂ composite membranes, whose performance was tested with various ionic dyes. The membrane with n_Ti = 0.15 exhibited the best filtration performance, considering the rejection and membrane flux. Membrane flux was over 15% higher than that of the original membrane, whereas rejection decreased by only 2%. The experimental data were analyzed to estimate the solute transport parameter and the mass transfer coefficient (k) using the Combined Film Theory-Solution-Diffusion (CFSD) membrane transport model. The adsorption of Al₂O₃–SiO₂ and TiO₂/Al₂O₃–SiO₂ membranes was investigated using the D–R isotherm model. It was found that cationic dyes adsorbed well on both membranes, and the adsorption binding force of the original membrane for dyes was strong, which is the reason for its poor antifouling performance. The anionic dye RB-KNB was less likely to cause membrane fouling. After six cycles of filtering the RB-KNB solution, the FRR increased from 79.9% for the original membrane to 93.8% for the modified membrane, further demonstrating that the antifouling performance of the membrane had been highly enhanced. Clearly, the obtained TiO₂/Al₂O₃–SiO₂ membrane possesses high application potential for textile wastewater treatment.