Magnéli Ti4O7 modified ceramic membrane for electrically-assisted filtration with antifouling property

• Conductive Magnéli Ti4O7 layer was successfully coated on tubular Al2O3 membrane.
• The conductive layer can serve as either anode or cathode for membrane separation.
• The synergy between electrochemistry and membrane separation was observed.
• Oily, humic acid wastewaters and BSA, were tested with excellent antifouling results obtained.

Antifouling tubular Al2O3 microfiltration membranes were successfully developed with a Magnéli Ti4O7 modified inner layer to enhance filtration performance coupled with external electricity. The Magnéli Ti4O7 layer was obtained by dip-coating a layer of TiO2 first and then reducing this layer at 1050 °C in H2 atmosphere. The fabricated Ti4O7 layer exhibited the conductivity of over 200 S cm−1 with particle size of 200–300 nm, average pore diameter of 350 nm and water contact angle of 0°. The antifouling performance of tubular Ti4O7/Al2O3 membrane was evaluated through a home-made cross-flow electrically-assisted membrane filtration module for the treatment of three typical feed solutions that are known to foul easily, namely, oily wastewater, humic acid (HA), and bovine serum albumin (BSA). During membrane filtrations, the permeate fluxes of Ti4O7/Al2O3 composite membranes at around critical electrical potentials could maintain over 90% of their initial values after 1 h, in contrast to the low values obtained with the uncoated Al2O3 membranes, 15.6% for oily wastewater, 62.7% for HA and 41.6% for BSA. Meanwhile, the permeate quality was also improved correspondingly, with oil, HA and BSA rejections increased from 95.8, 2.0 and 18.1% of uncoated Al2O3 membranes to 97.9, 96.2 and 76.1% of Ti4O7/Al2O3 membranes respectively. The total energy consumed by the electrically-assisted filtration of oily wastewater at around critical electrical potential in 1 h has decreased 58% in comparison with uncoated Al2O3 membrane in terms of kWh m−3 permeate. For HA and BSA, the total amounts of energy also decreased over 53 and 47% compared with corresponding ultrafiltration membranes, which are commonly used for HA and BSA rejections, at the same average permeate fluxes in 1 h. Therefore, the designed electrically-assisted filtration process with Magnéli Ti4O7 modified membrane provides a promising alternative for ceramic membrane filtrations with antifouling property, good permeate quality and easy operation.

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