Mauro Capocelli

Degradation of ibuprofen by hydrodynamic cavitation: Reaction pathways and effect of operational parameters

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.

Modeling of cavitation as an advanced wastewater treatment

Abstract This paper presents a theoretical study of cavitation as an advanced oxidation process. A mathematical algorithm, which couples single bubble dynamics and chemical reactions for a cavitating bubble, is proposed and compared with experimental and theoretical works reported in the literature. The main output variable, used for comparison, is the hydroxyl radical production. A wide range of parameter values is evaluated for the analysis of hydrodynamic cavitation in an orifice. Thanks to the large number of simulation, it was possible to find a very good agreement with a design correlation proposed in the literature. Additionally, a novel approach has been proposed, which consists of integrating the estimated radical production over a typical bubble size distribution in order to predict a global oxidant production. Moreover, by fixing the values of flowrate, pressure, and geometric parameters, a real experimental condition of hydrodynamic cavitation in a Venturi device has been simulated. This allow...

Chapter 5 – Direct Synthesis of Methanol and Dimethyl Ether From a CO2-Rich Feedstock: Thermodynamic Analysis and Selective Membrane Application

This chapter focuses on the methanol and DME synthesis processes fed by a CO 2 -rich syngas feedstock derived from a biological process as fermentation or gasification of biomasses. The conversion of a CO 2 -rich stream allows the valorization of carbon dioxide, converting it into added high-value products such as methanol and dimethyl ether. However, a thermodynamics analysis highlights the strong negative effect that an inlet CO 2 composition has on conversion reactions and the products yielded. The solution to supporting methanol/DME production processes with high contents of CO 2 is to integrate a membrane that is selective to water and able to remove the generated steam. This approach avoids accumulation of water inside the reaction environment, thus overcoming the thermodynamic thresholds and supporting the methanol and DME generation reactions.

Cavitational reactor for advanced treatment of contaminated water: the effect of recovery pressure

AbstractThis article deals with study of hydrodynamic cavitation in a Venturi reactor by considering the degradation of p-nitrophenol and the numerical simulation of a cavitating bubble in the explored experimental conditions. The parameters depicting the cavitation performances are reported for several experimental conditions. The best result of pNP mass removed at 30 min was found by setting the inlet pressure at 0.70 MPa and the recovery one at 0.38 MPa (≈40%), while the best performances in terms of pNP conversion per unit energy consumed were observed at 0.40 MPa (2.41 mg/MJ). The study represents a step forward in the work carried out by our research group to gain theoretical insight and optimize cavitation for advanced wastewater treatment.

Thermodynamic features of dioxins' adsorption.

In this paper, the six more poisonous species among all congeners of dioxin group are taken into account, and the P-T diagram for each of them is developed. Starting from the knowledge of vapour tensions and thermodynamic parameters, the theoretical adsorption isotherms are calculated according to the Langmuirs model. In particular, the Langmuir isotherm parameters (K and wmax) have been validated through the estimation of the adsorption heat (ΔHads), which varies in the range 20-24kJ/mol, in agreement with literature values. This result will allow to put the thermodynamical basis for a rational design of different process units devoted to dioxins removal.