Simultaneous ethylbenzene decomposition by ozone in a liquid–solid–gas three-phase system

The aim of this study is to analyse the simultaneous decomposition of ethylbenzene (ETB), in a three-phase system (liquid–solid–gas) using ozone. Ozone was injected in the liquid phase (10 mg of ETB dissolved in water) and then, the gas flow transferred this compound by stripping to the solid phase (calcinated commercial sand or CS, and calcinated agricultural soil or AS). This transferring yields ETB adsorption in the solid phase, where it is decomposed by the residual ozone. The rest of the ETB is transferred to the gas phase over the solid phase, where the remaining ozone mass reacts with the released ETB. In this reaction system, after 20 min, 96% of ETB was decomposed during ozonation. ETB elimination from the liquid phase attains 29% of the initial concentration due to the simultaneous processes: Stripping and decomposition by ozone. Meanwhile, 53% and 58% of ETB were degraded in the CS and AS, respectively. Thus, the rest of ETB was degraded in the gaseous phase (14% and 9%, with the presence of CS and AS respectively). In the proposed treatment scheme, most of the ozone mass is used, minimizing the residual ozone at the reactor outlet, and achieving the almost complete decomposition of the contaminant. The identified intermediates and final products of ETB decomposition at each reaction phase (malonic, maleic, oxalic as well as formic acids) are less toxic than ETB (demonstrated by the seed germination test in the liquid phase). This reaction strategy yields improving ozone consumption along with the decomposition of ETB.