Comparison of effectiveness of acoustic and hydrodynamic cavitation in combined treatment schemes for degradation of dye wastewaters

Cavitation has shown promising applications but individually it cannot prove to be an energy efficient approach for wastewater treatment. The present study reports the use of combined treatment strategies based on cavitation and different oxidizing agents (H2O2, Na2S2O8 and NaOCl). Decolorization of two biorefractory dye pollutants viz. orange acid-II (OA-II) and brilliant green (BG) has been investigated as model systems for comparison of the effectiveness of cavitating conditions generated by acoustic and hydrodynamic modes. The optimum conditions for temperature, pH and power dissipation in the case of acoustic cavitation and inlet pressure in the case of hydrodynamic cavitation have been established initially. At the optimum operating conditions, the effect of combination of different oxidizing agents has been examined with an objective of obtaining the maximum decolorization. Basic extent of decolorization due to the use of oxidizing agents has also been quantified by performing experiments in the absence of cavitating conditions. The obtained results for cavitational yields indicate that the decolorization is most efficient for the combination of hydrodynamic cavitation and chemical oxidation as compared to chemical oxidation and acoustic cavitation based combination for both the dye effluents.