Photosonochemical degradation of organic matter in water：a comparative study

摘要

Recent developments in sonochemistry have led us to study its use to treat water and wastewater.Currently,the sonochemical destruction of aromatic compounds in water solution is obtained with low rates.The aim of this work is to evaluate the efficiency of the sonochemical effect in conjunction with a photochemical irradiation and the effects of parameters such as pH.ultrasound frequency(35 and 130 kHz),and initial concentration on the degradation processes.The oxidation of a model pollutant.phenol,has been carried out in sonuv reactor.It was considerably more effective than ultrasound wave or ultraviolet light alone.It may be the result of three difierent oxidative processes:direct photochemical action,high frequency sonochemistry and reaction with ozone(produced by ultraviolet irradiation of air).Identification of the first intermediates of the reaction(hydroquinone,catechol,benzoquinone and resorcin)indicates that OH radicals are involved in the Photosonochemical degradation mechanisms.The experimental results have shown that lower pH and lower concentration of phenol favor the phenol degradation.But the rates of phenol degradation under sonication have always been quite low.The disappearance of phenol in each case approximately obeyed first-order kinetics with the apparent first-order decay constant increasing with decreasing solute concentration.