Sonochemical reactions, when, where and how: Modelling approach

This chapter introduces state-of-the-art modelling techniques of chemical kinetics inside a single spherical oscillating bubble placed in an infinite domain of liquid water. The initial content of the bubble is pure oxygen and water vapor. The reaction mechanism that governs chemical kinetics inside the bubble takes into account many aspects that are usually neglected in previous sonochemical investigations. First, at the collapse state of a bubble, the pressure inside can reach several hundreds of atmospheres; thus, the incorporation of the pressure dependence of reactions in which a third body plays a role is mandatory. Second, third body efficiencies are also taken into account. Third, the backward reactions are computed via thermodynamic equilibrium conditions. Fourth, reactions that have non-Arrhenius temperature dependence can be described by two sets of Arrhenius constants. These reactions are identified and modelled properly. As more experimental data have been accumulated over the decades, the Arrhenius constants of certain reactions have been changed even by orders of magnitude. Therefore, it is also important to employ up-to-date values of the Arrhenius constants. The behavior of the proposed model is demonstrated with reaction condition sets (pressure amplitude, frequency and bubble size) typically used during the experiments. The production of important chemical species (e.g., hydrogen or free radicals) are investigated from energy efficiency points of view (yield in mole per unit dissipated power of the bubble)