Photocatalytic degradation of volatile and nonvolatile organic compounds on titanium dioxide particles using fluidized beds

The photocatalytic degradations of an acid dye, C.I. Acid Blue 40, on titanium dioxide (TiO2) particles suspended in a gas-liquid dispersion, and of methylethyl ketone (MEK) on TiO2 particles suspended in the liquid were carried out using coaxial double-cylinder-type reactors. The former degradation was executed in a three-phase fluidized bed, whereas the latter one was done in a liquid-solid fluidized bed. A black-light-type fluorescent tube was installed in the internal cylinder of the reactor. The photocatalytic degradation of both acid dye and MEK here could be described as first-order with respect to the reactant species (i.e., acid dye or MEK). The apparent first-order rate constants in both systems, however, decreased with increasing initial concentration of reactant species. Such an observation was examined on the basis of the Langmuir-Hinshelwood-type catalytic reaction mechanism and the competition of light absorption due to the reactant species. In both degradation systems, the observed relationship between the apparent first-order rate constant and TiO2 catalyst loading was satisfactorily compared with the prediction on the basis of the premise that the decay of light illumination obeys Lambert-Beer law.