Study of the influential factors in the simultaneous photocatalytic degradation process of three textile dyes

The influence of several factors in the simultaneous photocatalytic degradation of three textile dyes – Acid Red 97, Acid Orange 61 and Acid Brown 425 – has been studied using a fractional factorial design 2 5-1. The considered factors were: the initial concentration of each dye, the catalyst concentration (TiO 2) and pH. First, we developed a rapid analytical methodology based on recording UV–visible spectra during the degradation process and a data treatment using multivariate curve resolution with alternating least squares (MCR-ALS), which enabled the three dyes to be quantified simultaneously despite the overlap of their spectra. The kinetic constant of degradation for each dye in all the experiments was evaluated. In all cases the degradation followed a first order kinetics. For a significance level of 5%, the most important factor in the photodegradation of each dye is the concentration of Acid Red 97, the degradation is more effective at higher pHs and, in the studied range, the concentration of the catalyst is not important.