In this study, the degradation of benzene by the means of an optimized surface/packed-bed hybrid discharge (SPBHD) plasma combined with γ-Al2O3-supported MOx (M = Ag, Mn, Cu, or Fe) catalysts in post plasma-catalysis (PPC) system. The effects of Ag loading amount and gas hourly space velocity (GHSV) for plasma-catalysis degradation of benzene have been systematically investigated. The experimental result showed that the benzene degradation was improved and the mineralization process was greatly enhanced towards total oxidation after the combination of plasma with all MOx/γ-Al2O3 catalysts. The AgOx/γ-Al2O3 catalyst exhibited the best catalytic activity in benzene degradation than the other catalysts in PPC system. The highest benzene degradation efficiency of 96% and COx selectivity of 99% can be obtained for AgOx/γ-Al2O3 catalyst with optimum Ag loading amount and GHSV of 15% and 22,856 h−1, respectively. Time course of benzene degradation during PPC process indicated that the plasma-induced catalytic activity of AgOx/γ-Al2O3 catalyst was temporary rather than lasting over a period after the plasma off. FT-IR analysis results revealed that the intermediate products (such as CO, HCOOH) and unwanted by-products (O3 and NOx) generated in plasma process could be significantly inhibited by PPC process with AgOx/γ-Al2O3 catalyst.

•A gas-phase dielectric barrier discharge (GPDBD) reactor was utilized to treat coking wastewater.•Total phenol and PAHs are effectively removed from wastewater by GPDBD reactor.•Enhanced Biodegradability of wastewater treated by GPDBD is observed by BOD5/COD.In the present study, gas phase dielectric barrier discharge (GPDBD) was used for pretreatment of coking wastewater with the objective of improving its biodegradability. The effects of some operational parameters including initial concentration, pH value of coking wastewater and air flow rate in GPDBD reactor on the COD removal were investigated. The removal efficiency of main compounds (total phenol, PAHs and NH3–N) and biodegradability (BOD5/COD) of coking wastewater were evaluated. The results show that the removal of COD by GPDBD fitted well with the second-order kinetics. The raw pH of coking wastewater was beneficial for COD removal. The optimal air flow rate was observed as 2 L min−1. Approximately 100% of total phenol and PAHs (benzoquinone, naphthalenol, dimethyl phthalate, etc.) removal was achieved at a reaction time of 120 min, and the removal efficiency of NH3–N reached 21%. The BOD5/COD ratio increased from 0.14 to 0.52 within 100 min of discharge treatment, suggesting the biodegradability of the coking wastewater was significantly improved. The GPDBD system is an effective pretreatment method for enhancing the biodegradability of coking wastewater.

A surface dielectric barrier discharge plasma reactor was employed to study Hg0 oxidation in coal-fired flue gas. The experimental results showed that 98 % of Hg0 oxidation efficiency and 13.7 μg kJ−1 of energy yield were obtained under a specific energy density (SED) of 7.9 J L−1. Increasing SED was beneficial for Hg0 oxidation due to higher production of active species. Higher initial concentration resulted in lower Hg0 oxidation efficiency, but higher amount of Hg0 oxidation. Water vapor inhibited Hg0 oxidation because the generation of O3 was suppressed. The presence of NO remarkably restrained Hg0 oxidation, while SO2 showed little effect on Hg0 oxidation. Roles of active species in Hg0 oxidation were examined under different gas atmospheres (O2 and air), indicating that O3 played an important role in Hg0 oxidation. Deposits on the internal surface of the reactor were analyzed by energy dispersive spectroscopy and the product was identified as HgO.

An innovative plasma reactor, which generates hybrid surface/packed-bed discharge (HSPBD) plasmas, was employed for the degradation of benzene. The HSPBD reactor was found to display remarkably better benzene degradation, mineralization, and energy performance than surface or packed-bed discharge reactors alone. The degradation efficiency, CO2 selectivity, and energy yield in the HSPBD reactor were 21%, 11%, and 3.9 g kWh–1 higher, respectively, than in a surface discharge reactor and 30%, 21%, and 5.5 g kWh–1 higher, respectively, than in a packed-bed discharge reactor operated at 280 J L–1. Particularly, the benzene degradation in the HSPBD reactor exhibited an unambiguous synergistic enhancement rather than a simple additive effect using the surface discharge and packed-bed discharge reactors. Moreover, in the HSPBD reactor, the formation of byproducts, such as NO2, was suppressed, while O3 was promoted. The use of N2 as the carrier gas was found to be effective for benzene degradation because of the fast reaction rate of N2(A3∑u+) with benzene, and oxygen species derived from the dissociation of O2 were found to be significant in the mineralization process. Thus, the addition of O2 to N2 allows for efficient degradation of benzene, and the optimized amount of O2 was determined to be 3%.

Atmospheric argon plasma jets are generated with the rod-tube/tube high voltage electrode and a ring ground electrode at 8 kHz sinusoidal excitation voltage. It is found that the vibrational temperature, electronic excitation temperature, atomic oxygen density and spectral intensity with the rod-tube high voltage electrode are enhanced significantly than that with the tube high voltage electrode. The atomic oxygen density, molecular nitrogen density, and average electronic density are about magnitude of 1016 cm−3, 1015 cm−3, and 1012 cm−3 respectively, and the excited Ar, N2, OH and O are presented in the plasma plume with the rod-tube/tube high voltage electrode.Highlights► The conduction and displacement current are determined by equivalent circuit diagram. ► The spectral characteristics are enhanced with the rod-tube high voltage electrode. ► The density of atomic oxygen and nitrogen are about 1016 and 1015 cm−3 magnitude. ► The average electronic density is in order of magnitude of 1012 cm−3.

An atmospheric-pressure argon plasma jet is generated with tube-ring electrodes in surface dielectric barrier discharge by a sinusoidal excitation voltage at 8 kHz. The electrical and spectral characteristics are estimated such as conduction and displacement current, electric-field, electron temperature, rotational temperature of N2 and OH, electronic excitation temperature, and oxygen atomic density. It is found that the electric-field magnitudes in the top area of the ground electrode are higher than that in the bottom area of the power electrode, and the electron temperature along radial direction is in the range of 9.6–10.4 eV and along axial direction in the range of 4.9–10 eV. The rotational temperature of N2 obtained by comparing the simulated spectrum with the measured spectrum at the C3Πu → B3Πg(Δv = − 2) band transition is in the range of 342–387 K, the electronic excitation temperature determined by Boltzmann's plot method is in the range of 3188–3295 K, and the oxygen atomic density estimated by the spectral intensity ratio of atomic oxygen line λ = 844.6 nm to argon line λ = 750.4 nm is in the order of magnitude of 1016 cm− 3, respectively.Highlights► The conduction and displacement current are calculated by equivalent circuit diagram. ► The 2D distribution of electric-field magnitude is calculated by ElecNet software. ► The electron temperature along axial direction is in the range of 4.9–10 eV. ► The oxygen atomic density is about a magnitude of 1016 cm− 3.

•Air plasma jet was generated by the dielectric barrier discharge.•Plasma jet length reached about 25 mm.•Gas temperature was close to the room temperature.•Active species (O*, N2*, N2+, and N*) were detected in the plasma plume.A low temperature air plasma jet was generated by syringe needle–ring electrodes dielectric barrier discharge at atmospheric pressure. It was found that the air plasma jet length reached about 25 mm and the gas temperature was close to the room temperature. Besides, the optical emission spectrum showed that a large number of active species, such as O* (777.2 nm), O* (794.7 nm), O* (799.5 nm), O* (844.6 nm), N2* (C-B), N2* (B-A), N2+ (B-X), N* (750.7 nm), N* (812.9 nm), etc., existed in the air plasma plume.

An integrated granular activated carbon (GAC) adsorption and dielectric barrier discharge (DBD) plasma degradation process was applied for treatment of organic wastewater. A methodology of scaling up the DBD plasma reactor was proposed, and a technique for regenerating GAC using the up-scaled DBD reactor driven by bipolar pulsed power has been achieved. The mass of exhausted GAC being treated was 1200 g in each experimental process. The feasibility of GAC regeneration using the up-scaled reactor was systematical assessed by monitoring the GAC regeneration efficiency (RE) and phenol degradation on GAC at different operational parameters, such as pulse voltage, treatment time, air flow rate and water content of GAC. Under the optimized conditions (pulse voltage of 21 kV, treatment time of 60 min, air flow rate of 0.45 m3/h and GAC water content of 31%), RE and the phenol degradation reached 94% and 70%, respectively. After four adsorption–regeneration cycles, RE was still 32% higher than RE of untreated exhausted GAC. FTIR analysis proved the phenol decomposition on GAC after DBD treatment. In addition, TOC and COD removal of adsorbed phenol on GAC reached 49% and 58%, respectively. Effect of DBD plasma on the texture characteristic of GAC after several adsorption–regeneration cycles were investigated by adsorption of N2 and Boehm titration. The results suggest that the up-scaled DBD reactor for GAC regeneration is feasible, and this technique for wastewater treatment provides us with an optimistic outlook for the practical application of this process.Highlights► Exhausted activated carbon was regenerated by dielectric barrier discharge plasma. ► A methodology of scaling up the dielectric barrier discharge reactor was proposed. ► The operation parameters of the up-scaled reactor was optimized.

In this study, an integrated granular activated carbon (GAC) preconcentration and dielectric barrier discharge (DBD) plasma degradation process was proposed for treatment of bisphenol A (BPA) wastewater. Firstly, BPA in water was adsorbed onto GAC, and then the BPA was decomposed and GAC was regenerated simultaneously by DBD plasma. The adsorption characteristics of BPA on GAC were studied by batch kinetics. The effects of pulse voltage, pulse repetitive rate, treatment time and air flow rate were investigated. Experimental results indicated that increasing pulse voltage, pulse repetitive rate, treatment time and air flow rate could enhance the degradation of BPA. The Fourier transform infrared spectroscopy analysis proved the removal of BPA on GAC after DBD treatment. The analysis of texture of GAC samples showed that the specific surface area and pore volume of GAC decreased after DBD regeneration. Furthermore, all adsorption equilibrium isotherms fitted the Langmuir model fairly well, which demonstrated that DBD plasma did not appear to modify the adsorption process but to shift the equilibrium toward lower adsorption concentrations.

Wastewater containing pentachlorophenol (PCP) was treated by granular activated carbon (GAC) adsorption and double-dielectric barrier discharge (D-DBD) plasma. A packed bed D-DBD reactor was applied for removal of PCP on GAC and GAC regeneration, where the discharge gap was filled with GAC. PCP degradation efficiency of 65% and GAC regeneration efficiency (RE) of 87% were achieved. Effects of discharge power, treatment time and O2 flow rate on PCP degradation and GAC regeneration were investigated. Increasing discharge power, treatment time and O2 flow rate were favorable for PCP degradation, and also contributed to GAC RE. C–Cl bonds in PCP were cleaved by D-DBD plasma. Effect of D-DBD plasma on physical and chemical properties of GAC during GAC regeneration process was characterized by N2 adsorption and Boehm titration. This study is expected to demonstrate the feasibility of applying D-DBD plasma for efficient organic wastewater treatment by coupling with GAC adsorption.

Nonthermal discharge plasma and TiO2 photocatalysis are two techniques capable of organic pollutants removal in soil. In the present study, a pulsed discharge plasma-TiO2 catalytic (PDPTC) technique by combining the two means, where catalysis of TiO2 is driven by the pulsed discharge plasma, is proposed to investigate the remediation of p-nitrophenol (PNP) contaminated soil. The experimental results showed that 88.8% of PNP was removed within 10 min of treatment in PDPTC system and enhancing pulse discharge voltage was favorable for PNP degradation. The mineralization of PNP and intermediates generated during PDPTC treatment was followed by UV-vis spectra, denitrification, total organic carbon (TOC), and COx selectivity analyses. Compared with plasma alone system, the enhancement effects on PNP degradation and mineralization were attributed to more amounts of chemically active species (e.g., O3 and H2O2) produced in the PDPTC system. The main intermediates were identified as hydroquinone, benzoquinone, catechol, phenol, benzo[d][1, 2, 3]trioxole, acetic acid, formic acid, NO2–, NO3–, and oxalic acid. The evolution of the main intermediates with treatment time suggested the enhancement effect of the PDPTC system. A possible pathway of PNP degradation in soil in such a system was proposed.

Chlorinated organics are frequently found as harmful soil contaminants and persisted for extended periods of time. A novel approach, named pulsed corona discharge plasma (PCDP), was employed for the degradation of pentachlorophenol (PCP) in soil. Experimental results showed that 87% of PCP could be smoothly removed in 60 min. Increasing pulse voltage, enhancing soil pH, lowering humic acid (HA) in soil and reducing granular size of the soil were found to be favorable for PCP degradation efficiency. Oxidation and physical processes simultaneously contributed to PCP removal in soil and ozone was the main factor in PCDP treatment. C—Cl bonds in PCP were cleaved during PCDP treatment by Fourier transform infrared spectroscopy (FTIR) analysis. The mineralization of PCP was confirmed by total organic carbon (TOC) and dechlorination analyses. The main intermediate products such as tetrachlorocatechol, tetrachlorohydroquinone, acetic acid, formic acid, and oxalic acid were identified by HPLC/MS and ion chromatography. A possible pathway of PCP degradation in soil in such a system was proposed.

Wire–plate-type reactors with the pulse-induced plasma chemical process (PPCP) have been extensively investigated for flue gas cleaning such as SOX and NOX, and the electrode configuration of reactors such as the plate-to-plate spacing and the wire-to-wire spacing is directly related to the formation of discharge plasma and the utilization efficiency of discharge energy, so it is useful to study the electrode configuration in order to provide a basis for PPCP applications. In this paper, the influence of these factors such as the plate-to-plate spacing and the wire-to-wire spacing on the discharge characteristics was investigated using a positive, nanosecond pulse generator. Some experimental results were obtained and discussed. It was found that when the wire-to-wire spacing (a) and the plate-to-plate spacing (c  ) of reactors satisfied the relation below, a/c=0.4-0.6a/c=0.4-0.6, the primary streamer energy was more bigger.