Mechanism and dynamic study of reactive red X-3B dye degradation by ultrasonic-assisted ozone oxidation process

Abstract The effectiveness of ozone combined with ultrasound techniques in degrading reactive red X-3B is evaluated. A comparison among ozone (O 3 ), ultrasonic (US), ozone/ultrasonic (O 3 /US) for degradation of reactive red X-3B has been performed. Results show that O 3 /US system was the most effective and the optimally synergetic factor reaches to 1.42 in O 3 /US system. The cavitation of ultrasound plays an important role during the degradation process. It is found that 99.2% of dye is degraded within 6 min of reaction at the initial concentration of 100 mg·L −1 , pH of 6.52, ozone flux of 40 L·h −1 and ultrasonic intensity of 200 W·L −1 . Ozonation reactions in conjunction with sonolysis indicate that the decomposition followed pseudo-first-order reaction kinetics but the degradation efficiencies are affected by operating conditions, particularly initial pH and ultrasonic intensity. A kinetic model is established based on the reaction corresponding to operational parameters. In addition, the main reaction intermediates, such as p -benzoquinone, catechol, hydroquinone, phthalic anhydride and phthalic acid, are separated and identified using GC/MS and a possible degradation pathway is proposed during the O 3 /US process.