Mechanistic studies of photoinduced degradation of Orange G using LC/MS

Photocatalytic degradation of Orange G dye was carried out with UV light in the presence of TiO₂ mixed with 20% chromium oxide as a catalyst. The conditions for maximum dye degradation were optimized in terms of catalyst amount, dye concentration, pH and time. The dye degradation followed pseudo first-order kinetics. LC-MS/MS was used to track the numerous intermediate products formed during the course of dye degradation. Major intermediate products confirmed were substituted phenols, aromatic hydroxyl amine, nitroso hydroxyl aromatic amines and dicarboxyl aromatic compounds. These intermediates along with some minor products were correlated to suggest a possible degradation pathway of Orange G. The dye degradation occurred mainly by three pathways, namely the hydroxylation of the aromatic ring, desulfonation and oxidative cleavage of the azo bond.