Degradation of the drug diclofenac in water by sonolysis in presence of catalysts

Diclofenac, as one of the most popular antiphlogistics, is produced in great quantities. Nowadays this drug is ubiquitously present in the aquatic environment due to its resistance to biodegradation. Degradation by ultrasonic irradiation is a possibility to eliminate diclofenac from water without the addition of chemicals. The sonolysis of diclofenac in water was investigated at ultrasound frequencies of 24 kHz, 216 kHz, 617 kHz, and 850 kHz and in the presence of various catalysts (TiO2, SiO2, SnO2, and titanosilicate). The degradation of diclofenac by sonolysis of an aqueous solution at 617 kHz followed first-order kinetics. Catalysts, especially TiO2 increased the rate of degradation. Within 30 min of irradiation, the relative concentration of diclofenac decreased from 100% to 16%. By HPLC and GC-MS methods, chlorinated anilines, phenols and carboxylic acid derivatives were detected as a result of the sonolysis. About 35% of organic chlorine was transformed into inorganic chloride. Most of the identified degradation products in the sonolysis of diclofenac were the same compounds that were detected during photo-oxidation experiments with this anti-inflammatory drug.