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The chemical effect of hydrodynamic cavitation (HC) in a Venturi reactor from both the theoretical and the experimental point of view is dealt. A mathematical model is presented to simulate the global production of hydroxyl radicals; it is based on a set of ordinary differential equations that account for the hydrodynamics, mass diffusion, heat exchange, and chemical reactions inside the bubbles. Experimentally, the degradation of p-nitrophenol (initial concentration 0.15 g dm 23 ) has been conducted in a lab scale Venturi reactor at inlet pressure ranging from 0.2 to 0.6 MPa and has been used to estimate the hydroxyl radical production. The optimum configuration, suggested by numerical simulations, has been experimentally confirmed. Thanks to the empirical validation, this novel modeling approach can be considered as a theoretical tool to identify the best configuration of HC operating parameters. Figure 8. a-b. Experimental number of degraded pNP moles ( • ); numerical value of •OH moles produced (2); values related to the treatment time (a) and to one cycle into the reactor (b).

Ibuprofen (IBP) is an anti-inflammatory drug whose residues can be found worldwide in natural water bodies resulting in harmful effects to aquatic species even at low concentrations. This paper deals with the degradation of IBP in water by hydrodynamic cavitation in a convergent-divergent nozzle. Over 60% of ibuprofen was degraded in 60 min with an electrical energy per order (EEO) of 10.77 kWh m(-3) at an initial concentration of 200 μg L(-1) and a relative inlet pressure pin=0.35 MPa. Five intermediates generated from different hydroxylation reactions were identified; the potential mechanisms of degradation were sketched and discussed. The reaction pathways recognized are in line with the relevant literature, both experimental and theoretical. By varying the pressure upstream the constriction, different degradation rates were observed. This effect was discussed according to a numerical simulation of the hydroxyl radical production identifying a clear correspondence between the maximum kinetic constant kOH and the maximum calculated OH production. Furthermore, in the investigated experimental conditions, the pH parameter was found not to affect the extent of degradation; this peculiar feature agrees with a recently published kinetic insight and has been explained in the light of the intermediates of the different reaction pathways.