Photolytic oxidation of Safranin-O with H2O2

Safranin-O (C.I name is Basic Red 2), a histologically important dye for counterstaining cartilages, was subjected to UV radiation in the presence of hydrogen peroxide. The photo-oxidation of the dye was monitored spectrophotometrically. The rate of degradation was calculated from the observed absorption data and was found to be first order. A systematic study of the effect of dye concentration as well as H2O2 concentration on the kinetics of dye degradation was carried out. Additionally, the effect of various additives on the degradation of this dye was also investigated. Most of the anions tested had a minor inhibitory effect on the degradation of the dye, with the most pronounced effect seen with Cl−, Br−, CH3COO−, and SO32− ions. Addition of cations did not significantly affect the dye degradation, except for Cd2+, Cu2+, and Ag+, all of which inhibited dye degradation, and Fe3+, which dramatically enhanced the rate of dye degradation. Examination of the effect of pH showed that the dye could be efficiently degraded over a wide pH range. A plausible explanation involving the probable radical initiated mechanism was given to explain the dye degradation.