Hydroxyl radical-mediated advanced oxidation processes for textile dyes: a comparison of the radiolytic and sonolytic degradation of the monoazo dye Acid Orange 7

Acid Orange 7, a textile azo dye, has been partially mineralized and degraded using γ-radiolysis and sonolysis. These two different advanced oxidation processes (AOP) are effective in producing ⋅OH radicals and cause complete destruction of the chromophore. The reaction mechanism of dye degradation has been probed by analyzing the reaction products with HPLC. In both cases, the final end products of degradation are oxalate and formate ions. The intermediates observed are all similar. While hydroxybenzenesulfonic acid is the major observed reaction intermediate in the oxidation processes, the pulse radiolysis studies indicate that the OH radical initiated pathway for attack occurs via the initial formation of 1,2-naphthaquinone and subsequent breakdown into oxalic acid.