Spectrophotometric aspects in the working of photocatalytic reactors

The current research work presents a methodology for determining the area of influence of the ultraviolet light emitted by a lamp located in the center of a photocatalytic reactor, at different concentrations of the catalyst TiO 2 degussa P25 and of the acid blue 9 dye. The measurements for the development of the corresponding methodology were performed through a novel system that allows the evaluation of light intensity at different distances from the lamp and at real working concentrations (with no dilution). The results obtained from these measurements indicate that for 600 mg L −1 , 450 mg L −1 , 300 mg L −1 , and 150 mg L −1 catalyst concentrations there is complete absorption of the light emitted by the lamp at distances of 0.8, 1.0, 1.6, and 2.4 cm, respectively. For the dye it was observed that at 2.4 cm from the lamp, there is an intensity reduction in the order of 91%, 85%, 71%, and 50% for concentrations of 80 mg L −1 , 60 mg L −1 , 40 mg L −1 , and 20 mg L −1 , respectively. The results obtained with the application of the developed methodology for the evaluation of the combined effect of the catalyst and dye absorption, show that, the absorption of the catalyst is more important than that of dye in the concentrations evaluated. With higher catalyst concentration, complete light absorption happens closer to the lamp wall, which produces an increment in the reaction kinetics; with higher dye concentrations, the amount of energy reaching by the catalyst decreases and causes an exponential decrease in the reaction kinetics. © 2009 American Institute of Chemical Engineers Environ Prog, 2010