Fabrication Of TiO₂/MWNTs Photocatalytic Composite Membrane And Its Performance In Water Treatment

Membrane separation technology has been widely used in drinking water and industrial wastewater treatment, but single membrane separation usually suffers the problem of membrane fouling in the application, resulting in an increase in the cost and energy consumption. As an energy-efficient and green technology, photocatalytic technology has been widely applied in the field of pollution control. However, it is difficult to separate and recover the photocatalysts. Integration of photocatalytic process and membrane separation has both photocatalytic ability and membrane separation function. It not only reduces membrane fouling in the separation processes, but also can solve the problem of separation and recovery of the photocatalysts. TiO2is one of the main photocatalytic functional layer materials of photocatalytic membranes due to its high catalytic activity, non-toxic and low price. TiO2photocatalyst suffer from the disadvantage of photo-generated electrons and holes recombination, and low quantum efficiency. To overcome these problems, TiO2/multi-walled nanotubes photocatalytic membrane was designed and fabricated empolying TiO2and carbon nanotubes (CNT) as a function layer in which electric field is formed to promote photoinduced charge separation and hence achieve efficient decomposition of the pollutants intercepted and the membrane fouling is inhibited.TiO2/multi-walled nanotubes (MWNTs)/Al2O3composite membrane was successfully fabricated by a two-step approach involving vacuum filtration of MWNTs suspension followed by chemical vapor deposition (CVD) of TiO2. The pore size of the as-prepared membrane was controlled by the deposition time of TiO2. Considering membrane flux and rejection as well as photocatalytic performance of the composite membrane, the optimal deposition time of TiO2was determined to be10min according to the experimental results. DRS results showed that TiO2/MWNTs/Al2O3composite membrane exhibited better UV light absorption than bare TiO2/Al2O3composite membrane. EDX map demonstrated that TiO2was distributed evenly on the surface of interweaving MWNTs membrane.15mg·L-1of Humic Acid (HA) was used as a target pollutant to investigate the water treatment performance of the composite photocatalytic membrane. By coupling membrane separation with photocatalysis technique, the removal efficiency of HA was80.9%within60min, which was improved12.2%compared with membrane separation alone during the same time. HA permeate flux of fitration with UV light irradiation was70.9%higher than that without UV after5h running, indicating good antifouling property of the composite membrane.