PHOTO CATALYTICALLY INDUCED DYE DECOLORIZATION IN AN UNSUPPORTED THIN-FILM REACTOR

Aqueous solutions of the dye indigo carmine were decolourised followin g ultraviolet (UV) irradiation in the form of thin liquid films in the presence of the semi-conductor photocataIyst, titanium dioxide, TiO2. These films, which were unsupported and totally enclosed, are com mon ly referred to as liquid ''bells'' and were generated using a nozzle o f special design, Decolourisation rates were increased as the concentr ation of TiO2 was increased from 0.74 to 11.8 g/l. Addition of hydroge n peroxide, H2O2, in concentrations ranging from 1.07 to 8.53 g/l at a fixed TiO2 concentration of 1.47 g/l also resulted in increased rates of decolourisation. The rate of disappearance of the indigo carmine w as assumed to follow first order kinetics whereas the influence of the two other species, TiO2 and H2O2, was accounted for by a power law mo del. The exponents for this model, obtained from an analysis of the ex perimental data, were 0.8 and 0.2 for, respectively TiO2 and H2O2.