TiO2-assisted degradation of environmentally relevant organic compounds in wastewater using a novel fluidized bed photoreactor

The photocatalytic degradation of two environmentally relevant organic compounds [4-chlorophenol (4-CP) and p-toluenesulfonic acid (PTSA)] was investigated using a novel cylindrical fluidized bed photoreactor (FBPR). Accumulated biodegradable organic acids, identified as intermediate reaction products, decreased after the removal of original pollutants. Measurements of the oxygen uptake rates with a mixed culture showed that all intermediate photooxidation products were much better biodegradable than the initial aromatic pollutants (4-CP, PTSA). The influence of HCO3- and Cl- on the degradation rate was also studied. For concentrations of 1 mM bicarbonate (HO. radical scavenger) and of 140 mM chloride (photo-inhibitor), the photocatalytic degradation rate decreased by 50%. During the photocatalytic reaction process, hydrogen peroxide accumulated in solution up to 0.21 mM depending on the initial concentration of the organic compounds and the concentration of dissolved oxygen. The relative quantum efficiency increased up to a factor of 2.3 by dosing of additional H2O2.