Sonochemical oxidation activity in 20-kHz probe systems: The effects of vessel shape, vessel wall thickness, and probe position

As a follow-up to our previous studies aimed at optimizing the use of the 20 kHz probe system in chemical and environmental engineering processes, the effects of vessel shape, vessel wall thickness, and probe position on sonochemical oxidation activity in circular and rectangular acrylic vessels were investigated. Electrical and calorimetric powers were obtained, and the sonochemical oxidation activity was quantified using KI dosimetry (pseudo-zero-order reaction kinetics) under 42 geometric conditions. All the geometric conditions of vessel shape, wall thickness, and probe position significantly affected the magnitudes and trends of the sonochemical activity. The average power conversion efficiencies from electrical to calorimetric power were 47.9 ± 3.0 % and 50.3 ± 6.1 % for circular and rectangular vessels, respectively. Overall, much higher activity was obtained when the probe was placed close to the bottom of the circular and rectangular vessels. Average volume-modified zero-order reaction rate constants were 0.20 ± 0.09 and 0.29 ± 0.08 μmol/min for the circular vessels with wall thicknesses of 5 and 10 mm and rectangular vessels with wall thicknesses of 5, 10, 15, and 20 mm. However, the probe positions for the highest activity moved toward to the liquid surface as the thickness increased in the rectangular vessels. The variation in the sonochemical activity was well visualized in the sonochemiluminescence (SCL) image (side and bottom views) analysis, and a higher intensity was observed in the SCL images when the probe was positioned adjacent to the vessel bottom. Thus, the total intensities of the SCL matched well with those of the sonochemical activity using KI dosimetry. Significantly different trends were observed in the BPA degradation tests, which may be attributed to the difference between the zero-order and first-order reactions.