The influence of titanium dioxide modifications on photocatalytic oxidation of lignin and humic acids

A few design options of attached photocatalyst reactors were tested in photocatalytic oxidation (PCO) of UV/VIS-irradiated aqueous solutions containing lignin and humic acids (HA). Degussa P25, anode-oxidized titanium and titanium dioxide doped with sulphur and boron atoms attached to various supports were tested. Maximum PCO efficiency with P25 was observed with floating glass plate support submerged at the depth of 7.0 mm, providing beneficial combination of the layer transparency and mixing conditions, thus noticeably exceeding the efficiency of buoyant glass micro-spheres.The electrolytic titanium dioxide film on metallic titanium demonstrated rather low efficiency: only HA in acidic media was photocatalytically oxidized. The sulphur content in the catalysts active in visible light was found to have an optimum value for the PCO efficiency.