The degradation of Reactive Blue 19 (RB 19) using photolysis, photocatalysis and sonophotocatalysis in aqueous solutions was investigated. Emphasis was given on the effects of different operating conditions viz. catalyst concentration, pH, initial dye concentration, ultrasonic power and reaction time) on RB 19 degradation. The extent of photocatalytic and sonophotocatalytic degradation was increased by decreasing pH, initial dye concentration and increasing catalysts loading and ultrasonic power. Ultrasound combined with photocatalysis was found efficient than the respective individual processes due to the enhanced formation of reactive hydroxyl radicals as well as the possible ultrasound-induced increase of the active surface area of the catalyst. The sonophotocatalytic efficiency was increased in acidic conditions as compare to individual processes at same experimental conditions (100 mg L-1 of dye concentration, 300 mg L-1 of TiO2 concentration, 240 W ultrasonic power and at pH 4). The kinetic study of RB 19 degradation under different experimental conditions apparently followed first order reaction. The intermediates and end products formed during the degradation were identified using gas chromatography/mass spectrometry (GC/MS) and a possible degradation pathway of RB 19 was proposed.

Maria Siddique, Romana Khan, Ather Farooq Khan and Robina Farooq