Catalysis of advanced oxidation reactions by ultrasound: A case study with phenol

• Published in: Journal of hazardous materials Vol. 146; no. 3; pp. 630 - 635
• Main Authors: Kidak, R., Ince, N.H.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 31-07-2007; Elsevier
• Subjects: Advanced oxidation; Applied sciences; Catalysis; Catalytic reactions; Chemical engineering; Chemistry; Exact sciences and technology; General and physical chemistry; Heat and mass transfer. Packings, plates; Hydrogen-Ion Concentration; Hydroxyl radicals; Oxidants, Photochemical - chemistry; Oxidation-Reduction; Ozone; Ozone - chemistry; Phenol - chemistry; Phenol - radiation effects; Pollution; Reactors; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Ultrasonics; Ultrasound; Ultraviolet Rays; UV-irradiation; Waste Disposal, Fluid - methods; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - radiation effects; Water Purification - methods; Hydroxyl radicals; Ozone; Advanced oxidation; UV-irradiation; Ultrasound; Sonication; Shear; Hydrogen peroxide; Synergism; Ozonization; Bubble; Photolysis; pH; Oxidation; Catalysis; Photochemical degradation; Pollutant behavior; Thermal decomposition; Hydrodynamics; Cavitation; Mass transfer; Operating conditions; Ultraviolet radiation; Surveillance; Phenols; Aqueous solution
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2007.04.106

The present study is about the enhancement in ozone-mediated degradation and UV (254
nm) photolysis of phenol in aqueous solutions by 300
kHz acustic cavitation and the selection of operating parameters for optimum phenol removal efficiency. The method was based on monitoring of the concentration of phenol during 90
min exposure to ozonation, sonication, UV photolysis, O
3/ultrasound, UV/ultrasound and O
3/UV/ultrasound operations. It was found that ozonation at alkaline pH was an effective method of phenol destruction, but it was considerably more effective when applied simultaneously with ultrasonic irradiation. The observed synergy particularly at alkaline pH was attributed to combined effects of: (i) increased ozone mass transfer (upon hydrodynamic shear forces created by ultrasonic bubbles) and (ii) excess hydroxyl radical formation (upon thermal decomposition of ozone in the gaseous cavity bubbles). Degradation of phenol by photolysis alone was negligible, while combination of UV-irradiation and ultrasound rendered considerable degrees of decay. The synergy here was explained by excess hydroxyl radicals that are formed by photolysis of ultrasound-generated H
2O
2. Maximum rate of phenol degradation was observed in case of combined application of ozone, UV and ultrasound at basic pH.