Developing an efficient TiO_2-coated biofilm carrier for intimate coupling of photocatalysis and biodegradation

摘要

30%Intimate coupling of photocatalysis and biodegradation (ICPB) shows promise to remove recalcitrant organic compounds from water, because photocatalysis breaks the compounds into biodegradable intermediates that are immediately mineralized by microorganisms inside a macroporous carrier, where they are protected from UV light and free radicals. Key to successful ICPB is a carrier capable of accumulating biofilm in its interior and strongly adhering photocatalyst on its exterior. We employed a low-temperature sintering method, the O method, to adhere TiO_2 to sponge-type macroporous carriers. The O method achieved a 7-fold increase of TiO_2 density, compared to the previously used sol-gel method, and it conserved the macropores for biofilm accumulation. Although the O-method carrier met the basic requirements of ICPB when degrading 2,4,5 trichlorophenol, it had low photocatalytic activity for breaking down more complex aromatics, like reactive dyes. Therefore, we improved the sintering method in two steps called the D and DN methods: reducing the TiO_2 concentration and then removing trimesic acid in the coating solution. The photocatalytic efficiency towards reactive black 5 increased 5 fold for the D method and 10 fold for DN method, and the DN carrier had superior TiO_2 adherence during long-term operation.