Comparative efficiencies of the degradation of Crystal Violet using UV/hydrogen peroxide and Fenton's reagent

The kinetics of the photo-decoloration of Crystal Violet (CV) imparted by UV/H₂O₂ process and also by Fenton's reagent were investigated. Negligible effects were observed in the presence of either UV light or H₂O₂ alone. As expected, the Fenton-mediated decoloration occurred much faster than the photolytic process. The effects of dye concentration, hydrogen peroxide concentration, pH and the presence of various ions on the decoloration rate were also studied. The extent of decoloration of the dye was found to be independent of pH. The rate of decoloration of the dye that occurred in both the photolytic as well as in the Fenton's methods was found to fit first-order kinetics. A mechanism is suggested for the degradation of the dye. The effect of anions that are normally present in dye effluent on the degradation of the dye was also investigated. Unexpectedly, hydrogen phosphate ions were found to dramatically inhibit the Fenton-mediated decoloration of the dye, whereas they had a minor effect on the photolytic degradation system. The other ions tested had equal minor inhibitory effects on dye degradation by both the methods.