Descoloração do azul de metileno por processo fotocatalítico utilizando o sistema Nb2O5/UV

Abstract

Water is the most important natural resource in the maintenance of life on Earth and great part of its pollutants are dyes that end up in waterbodies, due to the inefficience in the dyeing process of the textile industry, one of the major polluting industries in the world. Traditional treatment methods for effluents cannot fully discolorate them, one of the outstanding method is Photocatalysis, an Advanced Oxidation Process (AOP) that uses photoactivated semiconductors in order to oxidize organic pollutants. The discoloration of methylene blue (MB) in photocatalytic reactions was evaluated by using the Nb2O5/UV system. Three parameters were varied using a central composite experimental design: pH of the reactional médium, Nb2O5 calcination temperature and catalyst load. All the reactions were performed in a batch reactor with bulk catalyst. The maximum MB discoloration achieved, in 150 minutes, was 96% (pH= 9,7, calcination temperature= 391 °C and catalyst load= 1 g L-1). The adsorption phenomenon had weak influence in the photocatalytic reactions and photolysis was not efficient in the MB discoloration. All of the three factor with the experimental design were considered significants to the reactions according to the Pareto Chart.