CNTs–TiO2/Al2O3 composite membrane with a photocatalytic function: Fabrication and energetic performance in water treatment

• Designed and fabricated a photocatalytic membrane based on heterojunction structure.
• The membrane exhibited efficient charge separation capacity.
• Membrane filtration coupled with photocatalysis exhibited synergistic effect.
• The membrane exhibited high anti-fouling capacity.

Integrating a microfiltration with photocatalysis is a rising method for improving the anti-fouling capability of membrane by degradating pollutants blocked the pores of membrane via photocatalysis. However, the quick recombination of photogenerated charges in the photocatalytic layer limited the performance of this photocatalytic membrane. To inhibit the recombination of photogenerated charges, a CNTs–TiO2/Al2O3 composite membrane was designed and fabricated. Compared with TiO2/Al2O3 membranes (the typical photocatalytic membrane), the CNTs–TiO2/Al2O3 composite membrane displayed lower photoluminescence intensity and higher photocurrent density, which indicated the higher separation efficiency of its photogenerated charges. To get a good combination of membrane flux and rejection, the CNTs content and the thickness of CNTs–TiO2 layer was optimized. Under the best prepared parameters, the Polyethylene glycol (PEG) rejection and permeate flux was 70% and 980 L m−2 h−1, respectively. The optimized CNTs–TiO2/Al2O3 composite membrane under UV light irradiation exhibited 3 times higher of the stable permeate flux than filtration alone, and the humic acid removal rate of composite membrane was 10% higher than TiO2/Al2O3 membranes. This work could provide an alternative way to improve rejection and photocatalytic efficiency for conventional photocatalytic membranes and facilitate their practical application in water treatment.

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