Comparison of calorimetric energy and cavitation energy for the removal of bisphenol-A: The effects of frequency and liquid height

For decades, the measurement of heat generated during sonication - the calorimetric method - has been considered to represent the energy efficiency of ultrasonic reactors for useful chemical reactions. In this study, a modified calorimetric energy method using cavitating and non-cavitating solutions, referred to as cavitation energy method, has been developed and compared with conventional calorimetric method for the removal of an organic pollutant, bisphenol-A, in aqueous solutions under various experimental conditions. As the liquid height/volume was increased, cavitation yield for the degradation and mineralization of BPA significantly increased at 36 kHz and 262 kHz. Higher cavitation yields were obtained for both degradation and mineralization at 262 kHz compared to 36 kHz. It was found that the cavitation energy had a better correlation with the degradation and mineralization of BPA compared to the calorimetric energy. The enhancement observed at higher liquid height has been suggested to be due to the establishment of a standing wave field. The cavitation energy method seems to be useful to design the sonochemical reactors for the removal aqueous pollutants. (C) 2011 Elsevier B.V. All rights reserved.