p-Nitrophenol contaminated soil remediation in a spray-type coaxial cylindrical dielectric barrier discharge plasma system.

In the present work, plasma remediation of p-nitrophenol (PNP) contaminated soil was performed in a novel spray-type coaxial cylindrical dielectric barrier discharge (DBD) system at ambient temperature. This system is capable of generating large-size nonthermal plasma (NTP) and improving the diffusion and transfer of chemical active species around the dispersed soil particles. Several key parameters including plasma treatment time, discharge voltage, soil granular size, the entry speed of soil, PNP initial concentration, gas variety, and gas flow rate were investigated in terms of PNP degradation and energy efficiencies. Under the optimized experimental conditions, 54.2% of PNP was degraded after only 50 s discharge treatment, indicating that the spray-type coaxial cylindrical DBD system can degrade organic pollutants in soil more quickly compared to other plasma systems due to its efficient transfer of reactive oxygen and nitrogen species (RONS) into the contaminated soil. The possible PNP degradation pathways were proposed based on intermediates identification results and the role of reactive species analysis. The toxicological assessment of the PNP decomposition products was conducted by quantitative structure-activity relationship (QASR) analysis. This work is expected to provide a potential plasma technology for rapid and efficient processing of industrial organic pollutants contamination soil.

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-MnOx catalysts is studied to treat dimethyl sulfide (DMS). The physicochemical properties of all catalysts and the effect of the catalytic performance of CeO2-MnOx catalysts on DMS removal efficiency are studied. Placing CeO2-MnOx catalysts after the non-thermal plasma system can improve the capability of DMS degradation. The results exhibit that CeO2-MnOx (1:1) catalyst presents a higher catalytic activity than that of CeO2, MnOx, CeO2-MnOx (1:0.5) and CeO2-MnOx (1:3). At the power of 21.7 W, the combination of dielectric barrier discharge and CeO2-MnOx (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-MnOx catalysts is proposed. Finally, the stability of the CeO2-MnOx (1:1) catalyst is investigated, and the reason for the decreased activity of the used catalyst is analyzed.