Ag–TiO2/HAP/Al2O3 bioceramic composite membrane: Fabrication, characterization and bactericidal activity

Ag–TiO2/hydroxyapatite (HAP, Ca10(PO4)6(OH)2)/Al2O3 bioceramic composite membrane was fabricated to integrate membrane separation and photocatalytic bacterial inactivation by a facile two-step approach involving sol–gel method followed by calcination. The as-prepared composite membrane was characterized as a microporous membrane structure with average 0.8 μm pore size, which comprised of Ag–TiO2/HAP composite layer with a thickness of 10 μm overlaid on α-Al2O3 disk support. Detailed morphology of Ag–TiO2/HAP composite layer revealed a thickness of 10–30 nm Ag–TiO2 photocatalytic layer partially covered over HAP particles. Surface photovoltage measurement revealed a superior ability of promoted interfacial charge-transfer reactions in the case of 1 wt.% Ag–TiO2 composite. A rapid crossflow membrane system was designed to evaluate the roles of the HAP layer and Ag–TiO2 photocatalyst in the inactivation of Escherichia coli (E. coli) in suspension. HAP acted as a high efficient bacterial adsorbent while Ag–TiO2 provided powerful photocatalytic attack toward E. coli strains. The removal of E. coli within 60 min with as-prepared membrane was approximately 6 and 4 log units under UV illumination (a weak light intensity of 0.3 mW/cm2) and in dark, respectively. The permeate flux of outlet was evidently improved by 71.7% after 1 h under UV illumination, compared with that in dark. These results showed that this novel membrane of anti-fouling property might integrate multifunction of membrane separation, bacterial adsorption and photocatalytic inactivation, which suggested great potential for antibacterial treatment of groundwater and drinking water.