Synergistic effects of sonolysis combined with photocatalysis in degradation of industrial waste water

The accelerated photocatalytic degradation of industrial wastewater using titanium dioxide as catalyst activated by ultrasound has been investigated in photocatalytic reactor using ultraviolet light source of 125 W. The effect of number of parameters, such as pH, oxidant concentration and catalyst dose has been examined to study the degradation rates in sonolytic, photocatalytic and sonophotocatalytic processes. The basic reaction mechanism for both sonolysis as well as photocatalysis is the generation of free radicals and subsequent attack by these on the pollutant organic species. If the ultraviolet and ultrasound are operated in combination, more number of free radicals will be available for the reaction thereby increasing the rates of reaction. The ultrasonic activation contributes degradation through cavitation and the turbulence induced by the cavitation phenomena can aid in eliminating the drawbacks associated with photocatalytic oxidation. The results showed that there was synergistic effect between ultrasound and ultraviolet irradiation in the presence of titanium dioxide since the rate constants of the combined process are greater than the sum of the rate constants of the individual processes. It differs from the other treatment processes because wastewater compounds are degraded rather than concentrated or transferred into a different phase. Because the secondary waste materials are not generated, there is no need to dispose of the treated materials. So, we can say that sonophotocatalysis is an excellent technique for treatment of wastewater. Keywords-sonolysis; photocatalysis; sonophotocatalysis; titanium dioxide