Intensification of cavitational activity in the sonochemical reactors using gaseous additives

• Evaluation of different gaseous additives for enhancing the cavitational effects.
• Optimum power dissipation, pH and temperature should be selected.
• Type of gas and its mechanism of intensification are important.
• Confirmation using simulations for volume fraction and pressure intensity.

Sonochemical reactors have a significant potential for intensification of physical as well as chemical processes due to the effects of hotspots, intense turbulence and generation of free radicals. However, it is observed that commercial scale applications of these reactors are scarce possibly due to lack of uniform intensified activity at large scale and reliable design/operating strategies. The present work deals with investigations related to the intensification of cavitational activity based on the use of different gaseous additives with the results being equally applicable for all gas–liquid applications of sonochemical reactors. Model reactions of oxidation of potassium iodide and salicylic acid degradation have been used for quantification of cavitational activity. Initially, effect of different operating parameters such as temperature, power, duty cycle and initial concentration has been investigated. The different gaseous additives used in the work include air, oxygen, nitrogen and carbon dioxide. Effect of air flow rate on the cavitational activity has also been examined. Theoretical modeling studies based on the use of COMSOL have also been performed to explain the alteration of pressure field distributions due to the presence of gaseous additives. Overall it can be said that presence of gases enhances the cavitational activity and the effect is dependent on the nature of the gas and its physicochemical properties as well as the operating conditions in terms of the flow rate of the introduced gas. The work presents new design related information helpful for effective scale up and operation of sonochemical reactors.