Sonochemical degradation of Coomassie Brilliant Blue: Effect of frequency, power density, pH and various additives

Coomassie Brilliant Blue (CBB), discharged mainly from textile industries, is an identified water pollutant. Ultrasound initiated degradation of organic pollutants is one among the promising techniques and forms part of the Advanced Oxidation Processes (AOPs). Ultrasonic degradation of CBB under different experimental conditions has been investigated in the present work. The effect of frequency (200 kHz, 350 kHz, 620 kHz and 1 MHz) and power density (3.5W mL(-1), 9.8W mL(-1) and 19.6W mL(-1)) on the degradation profile was evaluated. The optimum performance was obtained at 350 kHz and 19.6W mL(-1). Similar to other sonolytic degradation of organic pollutants, maximum degradation of CBB was observed under acidic pH. The degradation profile indicated a pseudo-first order kinetics. The addition of ferrous ion (1 x 10(-4) M), hydrogen peroxide (1 x 10(-4) M), and peroxodisulphate (1 x 10(-4) M) had a positive effect on the degradation efficiency. The influence of certain important NOM like SDS and humic acid on the sonolytic degradation of CBB was also investigated. Both the compounds suppress the degradation efficiency. LC-Q-TOF-MS was used to identify the stable intermediate products. Nearly 13 transformed products were identified during 10 min of sonication using the optimized operational parameters. This product profile demonstrated that most of the products are formed mainly by the OH radical attack. On the basis of these results, a degradation mechanism is proposed. (C) 2014 Published by Elsevier Ltd.