PHOTOCATALYTICALLY INDUCED DYE DECOLOURISATION IN AN UNSUPPORTED THIN FILM REACTOR

Aqueous solutions of the dye indigo carmine were decolourised following ultraviolet (UV) irradiation in the form of thin liquid films in the presence of the semi-conductoi photocatalyst, titanium dioxide, Ti02. These films, which were unsupported and totally enclosed, are commonly referred to as liquid “bells” and were generated using a nozzle of special design. Decolourisation rates were increased as the concentration of Ti0₂ was increased from 0.74 to 11.8 g/l. Addition of hydrogen peroxide, H₂0₂, in concentrations ranging from 1.07 to 8.53 g/l at a fixed Ti0₂ concentration of 1.47 g/l also resulted in increased rates of decolourisation. The rate of disappearance of the indigo carmine was assumed to follow first order kinetics whereas the influence of the two other species, Ti02 and H202, was accounted for by a power law model. The exponents for this model, obtained from an analysis of the experimental data, were 0.8 and 0.2 for, respectively Ti0₂ and H₂0₂.