Toluene decomposition performance and NOx by-product formation during a DBD-catalyst process

Physicochemical Characteristics and Antimicrobial Efficacy of Plasma-Activated Water Produced by an Air-Operated Coaxial Dielectric Barrier Discharge Plasma

In this study, Plasma-Activated Water (PAW) was synthesized using a coaxial Dielectric Barrier Discharge (DBD) reactor, benefiting from the elevated capacity of air-flow-assisted DBD discharges to enhance nitrogen-based species concentration. By manipulating operational parameters, including gas flow rate, activation time, and DI water volume, we achieved significant concentrations of reactive oxygen and nitrogen species (RONS). As a result, the PAW obtained displayed pronounced physicochemical attributes: a pH of 2.06, an ORP of 275 mV, conductivity of 3 mS/cm, and TDS of 1200 mg/L. A pivotal aspect of this research was the evaluation of the reactor’s efficiency, as indicated by metrics like the specific input energy and ozone efficiency yield. The antimicrobial potential of the PAW was also assessed against pathogenic microbes, with remarkable reductions in viability for both Staphylococcus aureus and Escherichia coli (99.99%) and a more moderate decrease for Candida albicans (37%). These findings underscore the capability of coaxial DBD reactors in crafting high-quality PAW with significant antimicrobial properties, necessitating further studies to validate its broad-spectrum and safe applications.

Non-Thermal Plasma Incorporated with Cu-Mn/γ-Al2O3 for Mixed Benzene Series VOCs’ Degradation

In this work, a coaxial dielectric barrier discharge (DBD) reactor was constructed to degrade the mixture of toluene and o-xylene, two typical benzene series. The Cu-MnO2/γ-Al2O3 series catalysts prepared by redox and impregnation methods were filled into the plasma device to degrade VOCs synergistically and explore the degradation effect. The experimental results showed that the introduction of a Cu-doped MnO2 catalyst significantly improved the pollutants’ removal efficiency and CO2 selectivity, and greatly inhibited the formation of by-products. Among them, Cu0.15Mn/γ-Al2O3 showed the highest removal efficiency (toluene was 100% and o-xylene was 100%), and the best CO2 selectivity (92.73%). The XRD, BET, XPS and SEM results confirmed that the synergistic effect between Cu and Mn in the Cu-Mn solid solution could promote the amount and reducibility of the surface active oxygen species, which improved the catalytic performance. Finally, the toluene and o-xylene decomposition pathways in the NTP catalytic system were speculated according to the detected organic matter. This work provides a theoretical and experimental basis for the application of DBD-catalyzed hybrid benzene series VOCs.

Removal of dimethyl sulfide by post-plasma catalysis over CeO2-MnOx catalysts and reaction mechanism analysis

The combination of a multistage rod plasma reactor and post CeO₂-MnO_x catalysts is studied to treat dimethyl sulfide (DMS). The physicochemical properties of all catalysts and the effect of the catalytic performance of CeO₂-MnO_x catalysts on DMS removal efficiency are studied. Placing CeO₂-MnO_x catalysts after the non-thermal plasma system can improve the capability of DMS degradation. The results exhibit that CeO₂-MnO_x (1:1) catalyst presents a higher catalytic activity than that of CeO₂, MnO_x, CeO₂-MnO_x (1:0.5) and CeO₂-MnO_x (1:3). At the power of 21.7 W, the combination of dielectric barrier discharge and CeO₂-MnO_x (1:1) catalyst could improve the DMS removal efficiency and CO₂ selectivity by 16.2% and 18.2%, respectively. This result maybe closely related with its specific surface area, redox properties and oxygen mobility. In addition, the degradation mechanism of DMS over CeO₂-MnO_x catalysts is proposed. Finally, the stability of the CeO₂-MnO_x (1:1) catalyst is investigated, and the reason for the decreased activity of the used catalyst is analyzed.

Decomposition efficiency and aerosol by-products of toluene, ethyl acetate and acetone using dielectric barrier discharge technique

Dielectric barrier discharge (DBD) has been widely used as end-of-pipe technology to degrade low-concentration volatile organic compound (VOC) emissions. In this work, the influence of DBD conditions including discharge voltage, VOC residence time in DBD plasma, VOC initial concentration and synergistic effect of multiple VOC mixing on the decomposition efficiency of three VOCs (toluene, ethyl acetate and acetone) were investigated systematically. One focus of this work was to investigate size distribution and chemical composition of aerosol by-products. The results suggested that high discharge voltage, long residence time and low VOC initial concentration would increase VOC removal ratio and their conversion to CO₂. Among the three VOCs, toluene was easiest to form particles with a mode diameter between 40 and 100 nm and most difficult to be decomposed completely to CO₂. Maximum aerosol yield from toluene was observed to account for 13.1 ± 1.0% of initial concentration (400 ppm) in the condition of discharge voltage 6 kV and residence time 0.52 s. Gas chromatography-mass spectrometry analysis showed that non-nitrogen containing benzene derivatives, nitrophenol derivatives and amines were the main components of toluene aerosol by-products. For ethyl acetate and acetone, aerosols could only be produced in the condition of high discharge voltages (>7.5 kV) and long gas residence time (≥0.95 s) with a bimodal distribution below 20 nm. When the mixture of three VOCs was fed into the plasma, we observed a strong synergistic effect that led to higher VOC removal ratio, but lower conversion of decomposed VOCs to CO₂ and aerosols.

NO Removal by Plasma-Enhanced NH3-SCR Using Methane as an Assistant Reduction Agent at Low Temperature

The effects of using CH4 as an assistant reduction agent in plasma-assisted NH3–SCR were investigated. The new hybrid reaction system performed better than DBD–NH3–SCR when the O2 concentration varied from 2% to 12%. Compared with DBD–NH3–SCR, DBD–NH3–CH4–SCR (NH3:CH4 = 1:1) showed a more significant promotion effect on the performance and N2 selectivity for NOX abatement. When the O2 concentration was 6% and the SIE was 512 J/L, the NO removal efficiency of the new hybrid system reached 84.5%. The outlet gas components were observed via FTIR to reveal the decomposition process and its mechanism. This work indicated that CH4, as an assistant agent, enhances DBD–NH3–SCR in excess oxygen to achieve a new process with significantly higher activity at a low temperature (≤348 K) for NOX removal.

The Design of MnOx Based Catalyst in Post-Plasma Catalysis Configuration for Toluene Abatement

This review provides an overview of our present state of knowledge using manganese oxide (MnOx)-based catalysts for toluene abatement in PPC (Post plasma-catalysis) configuration. The context of this study is concisely sum-up. After briefly screening the main depollution methods, the principles of PPC are exposed based on the coupling of two mature technologies such as NTP (Non thermal plasma) and catalysis. In that respect, the presentation of the abundant manganese oxides will be firstly given. Then in a second step the main features of MnOx allowing better performances in the reactions expected to occur in the abatement of toluene in PPC process are reviewed including ozone decomposition, toluene ozonation, CO oxidation and toluene total oxidation. Finally, in a last part the current status of the applications of PPC using MnOx on toluene abatement are discussed. In a first step, the selected variables of the hybrid process related to the experimental conditions of toluene abatement in air are identified. The selected variables are those expected to play a role in the performances of PPC system towards toluene abatement. Then the descriptors linked to the performances of the hybrid process in terms of efficiency are given and the effects of the variables on the experimental outcomes (descriptors) are discussed. The review would serve as a reference guide for the optimization of the PPC process using MnOx-based oxides for toluene abatement.