Theoretical investigation of the effect of ambient pressure on bubble sonochemistry: Special focus on hydrogen and reactive radicals production

Abstract

Abstract The effect of static pressure (P∞) on bubble sonochemistry (i.e. hydrogen and reactive species production) is investigated on a range of ambient bubble sizes (R0) for argon-saturated water. The used ambient pressure ranges from 0.3 to 2 atm, where its impact is shown for frequencies of 355, 500 and 1000 kHz. It is found that for each ambient pressure, the change of bubble temperature and its chemical yield profiles vs. R0 follow a Gaussian tendency, where optimal values are inferred from these curves. Optimum pressures of 0.7 and 0.5 atm are obtained at 355 and 515 kHz for both, the bubble temperature and the production of hydrogen. The range of R0 for active bubbles varies sensitively with P∞ and frequency variation. The yield of H2, O and H is promoted in the regions of R0 where the average bubbles temperature is ~ 8500 K, conversely to the production of OH, which is favored at relatively lower temperatures (~5500 K).