Characteristics of back corona discharge in a honeycomb catalyst and its application for treatment of volatile organic compounds

Adsorption Behavior of Multi-Component BTEX on the Synthesized Green Adsorbents Derived from Abelmoschus esculentus L. Waste Residue

Benzene, toluene, ethylbenzene, and xylene (BTEX) removal is one of the most common difficulties in air pollution control. They are emitted from several processes, prejudicial to the environment and humans. BTEX leads to various environmental risks, and there is a significant need for a creating process for the complete removal of BTEX from air streams. This study's objective is the multi-component adsorption of BTEX pollutants from an air stream, by synthesizing activated carbons (ACs) under several operations. A lignocellulosic waste biomass, Abelmoschus esculentus L. (AE), was utilized as the precursor for synthesizing activated carbons (AE-ACs), and their surface chemical characteristics were investigated. Optimization processes were examined, and the change in the surface area of AE-ACs was investigated as change of some variables results like activation agent, impregnation ratio, temperature, and activation time. The maximum surface area of 968 m2/g and total pore volume of 0.51 cm3/g were attained at 1:2 impregnation ratio, activation time of 110 min, and activation temperature of 800 °C, under N2 atmosphere. A mixture of BTEX pollutants was employed to consider the effect of humidity (0.5, 1, 1.5, and 2 wt%) and initial concentrations (from 5 to 300 mg/m3), using a contact time of 120 min at the temperature of 25 °C. Under the studied conditions, the multi-component and single-component BTEX adsorption capacities by HCl-activated carbon, AE-ACH, were specifically achieved to 6.86-51.36 mg/g and 22-93.62 mg/g, respectively. Overall, Abelmoschus esculentus L. was exploited for the synthesis of AE-ACH which was successfully utilized for efficient BTEX capture from a polluted air stream.

Soot Combustion over Cu-Co Spinel Catalysts: The Intrinsic Effects of Precursors on Catalytic Activity

In this work, a series of CuCo₂O₄-x (x = N, A and C) catalysts were synthesized using different metal salt precursors by urea hydrothermal method for catalytic soot combustion. The effect of CuCo₂O₄-x catalysts on soot conversion and CO₂ selectivity in both loose and tight contact mode was investigated. The CuCo₂O₄-N catalyst exhibited outstanding catalytic activity with the characteristic temperatures (T₁₀, T₅₀ and T₉₀) of 451 °C, 520 °C and 558 °C, respectively, while the CO₂ selectivity reached 98.8% during the reaction. With the addition of NO, the soot combustion was further accelerated over all catalysts. Compared with the loose contact mode, the soot conversion was improved in the tight contact mode. The CuCo₂O₄-N catalysts showed better textural properties compared to the CuCo₂O₄-A and CuCo₂O₄-C, such as higher specific surface areas and pore volumes. The XRD results confirmed that the formation of a CuCo₂O₄ crystal phase in all catalysts. However, the CuO crystal phase only presented in CuCo₂O₄-N and CuCo₂O₄-A. The relative contents of Cu²⁺, Co³⁺ and O_ads on the surface of CuCo₂O₄-x (x = N, A and C) catalysts were analyzed by XPS. The CuCo₂O₄-N catalyst displayed the highest relative content of Cu²⁺, Co³⁺ and O_ads. The activity of catalytic soot combustion showed a good correlation with the order of the relative contents of Cu²⁺, Co³⁺ and O_ads. Additionally, the CuCo₂O₄-N catalyst exhibited lower reduction temperature compared to the CuCo₂O₄-A and CuCo₂O₄-C. The cycle tests clarified that the copper-cobalt spinel catalyst obtained good stability. In addition, based on the Mars-van Krevelen mechanism, the process of catalytic soot combustion was described combined with the electron transfer process and the role of oxygen species over CuCo₂O₄ spinel catalysts.

The Bibliometric Analysis and Review of the Application of Plasma in the Field of VOCs

The application of plasma in the field of volatile organic compounds (VOCs) can be traced back to the 1990s and has gradually developed into an important research field. In this regard, this article primarily sorts and analyzes the literature on the “application of plasma in the field of VOCs” in the Web of Science core collection database from 1992 to 2021 and, subsequently, obtains important data and trends, including the annual number of articles published, country, institution analysis, and journal, as well as discipline analysis, etc. The results show that China is not only in a leading position in the field of research, but also has six top-ten research institutions. This field has more research results in engineering, chemistry, physics, and environmental disciplines. In addition, this article summarizes dielectric barrier discharge (DBD) and titanium-containing catalysts, which represent the discharge characteristics and type of catalyst highlighted through the hot keywords. This review will provide certain guidance for future, related research.

Evaluation of Au/γ-Al2O3 nanocatalyst for plasma-catalytic decomposition of toluene

The emission of toluene into the atmosphere can seriously affect the environmental quality and endanger human health. A dielectric barrier discharge reactor filled with a small amount of Au nanocatalysts was used to decompose toluene in He and O₂ gases mixtures at room temperature and atmospheric pressure. Normally, the oxidation of toluene using Au nanocatalysts suffers from low reaction activity and facile catalyst deactivation. Herein, the effects of Au loading, calcination time and calcination temperature were systematically investigated. It was found that 0.1 wt%Au/γ-Al₂O₃ calcined at 300 °C for 5 h can keep an average size around 6 nm with good dispersion on γ-Al₂O₃ surface and display the best catalytic performance. Moreover, the influences of energy density, gas flow rate, toluene concentration and O₂ concentration on toluene degradation using 0.1 wt%Au/γ-Al₂O₃ were evaluated. It showed the best catalytic performance of near 100% conversion for toluene degradation under the reaction conditions of the energy density was 20 J/L, the gas flow rate was 300 mL/min, the concentration of toluene was 376 mg/m³ and the oxygen content was 10%. Combining experimental results and theoretical calculations, the values of reaction constant k were 8.6 × 10^-5, 3.53 × 10^-5 and 3.09 × 10^-5 m⁶/(mol*J), when O₂ concentration, power or flow rate changed, respectively. Therefore, O₂ concentration has the greatest effect on toluene decomposition compared to other factors in the presence of Au/γ-Al₂O₃.

Recent progress in air treatment with combined photocatalytic/plasma processes: A review

Nowadays, air pollution is an increasingly important topic, as environmental regulations require limiting pollutant emissions. This problem requires new techniques to reduce emissions by either improving the current emission control systems and processes or installing new hybrid treatment systems. These are of broad diversity, and every system has its advantages and disadvantages. The tendency is, accordingly, to combine various techniques to achieve more acceptable and suitable treatment. Recent studies suggest that the combination of photocatalysis and plasma in a reactor can offer attractive pollutant treatment efficiency with a minimum of partially oxidized by-products than that of these processes taken separately. However, there is little review of the capability of this pairing to treat different brands of pollutants. Besides, available data concerning reactor design with flows treated 10 to 1000 times higher than those studied at the lab scale. This review paid particular attention to determine the reaction mechanisms in terms of engineering and design of combination reactors (plasma and catalysis). Likewise, we developed the effect of critical parameters such as pollutant load, relative humidity, and flow rate to understand the degradation kinetics of specific pollutants individually by using plasma and photocatalysis. Additionally, this review compares different designs of cold plasma reactors combination with heterogeneous catalysis with special attention on synergistic and antagonistic effects of using plasma and photocatalysis processes at the laboratory, pilot, and industrial scales. Therefore, the elements discussed in this review stick well to the first theme on pollution prevention of the special issue concerning pollution prevention and the application of clean technologies to promote a circular (bio) economy.

Removal of ethyl acetate in air by using different types of corona discharges generated in a honeycomb monolith structure coated with Pd/γ-alumina

A method based on the corona discharge produced by high voltage alternating current (AC) and direct current (DC) over a Pd/γ-Al₂O₃ catalyst supported on a honeycomb structure monolith was developed to eliminate ethyl acetate (EA) from the air at atmospheric pressure. The characteristics of the AC and DC corona discharge generated inside the honeycomb structure monolith were investigated by varying the humidity, gas hourly space velocity (GHSV), and temperature. The results showed that the DC corona discharge is more stable and easily operated at different operating conditions such as humidity, GHSV, and gas temperature compared to the AC discharge. At a given applied voltage, the EA conversion in the DC honeycomb catalyst discharge is, therefore, higher compared with that in the AC honeycomb catalyst discharge (e.g., 96% of EA conversion compared with approximately 68%, respectively, at 11.2 kV). These new results can open opportunities for wide applications of DC corona discharge combined with honeycomb catalysts to VOC treatment.

High-Throughput NOx Removal by Two-Stage Plasma Honeycomb Monolith Catalyst

A two-stage plasma catalyst system for high-throughput NO_x removal was investigated. Herein, the plasma stage involved the large-volume plasma discharge of humidified gas and was carried out in a sandwich-type honeycomb monolith reactor consisting of a commercial honeycomb catalyst (50 mm high; 93 mm in diameter) located between two parallel perforated disks that formed the electrodes. The results demonstrated that, in the plasma stage, the reduction of NO_x did not occur at room temperature; instead, NO was only oxidized to NO₂ and n-heptane to oxygenated hydrocarbons. The oxidation of NO and n-heptane in the honeycomb plasma discharge state was largely affected by the humidity of the feed gas. Furthermore, the oxidation of NO to NO₂ occurs preferably to that of n-heptane with a tendency of the NO oxidation to decrease with increasing feed gas humidity. The reason is that the generation of O₃ decreases as the amount of water vapor in the feed gas increases. Compared to the catalyst alone, the two-stage plasma catalyst system increased NO_x removal by 29% at a temperature of 200 °C and an energy density of 25 J/L.

Nonthermal plasma in practical-scale honeycomb catalysts for the removal of toluene

Nonthermal plasma combined with a practical-scale honeycomb catalyst of 5.0 cm in height and 9.3 cm in diameter was investigated for the removal of toluene. The creation of plasma in the honeycomb catalyst greatly depended on the humidity of the feed gas and the presence of metals on the honeycomb surface. Compared to the bare ceramic honeycomb, the metal-loaded one gave higher toluene removal efficiency because the decomposition of toluene by the plasma-generated reactive species occurred not only homogeneously in the gas phase but also heterogeneously on the catalyst surface. The present plasma-catalytic reactor was able to successfully remove about 80% of dilute toluene (15 ppm in air) at a large flow rate of 60 L/min with a specific energy input of 58 J/L. The honeycomb-based plasma-catalytic reactor system is promising for practical applications since it can overcome such problems as high-pressure drop and difficulty in scale-up encountered in packed-bed reactors.

Dependence of humidified air plasma discharge performance in commercial honeycomb monoliths on the configuration and key parameters of the reactor

The effect of the reactor configuration and several key parameters such as the gas temperature, humidity, and flow rate on the corona discharge plasma in honeycomb monoliths was investigated. The AC corona discharge-based plasma reactor consisted of two parallel electrodes (perforated disk/wire-mesh) placed at both ends of the honeycomb monolith. Although the wire-mesh electrode offers increased sharpness, the perforated disk electrode, where the corona discharge started at the sharp edges of the holes, produced more discharge power because of the larger effective electrode area. Loading a small amount of metal onto the monolith was found to increase the discharge power significantly. Coating the monolith with a zeolite such as ZSM-5 (Si/Al: 23.9) led to a decrease in the discharge power because of its hydrophobic nature and large surface area. The result also revealed that the operating temperature, the humidity of the feed gas, and the gas velocity were key factors affecting the discharge performance. The discharge power was inversely proportional to the temperature. On the other hand, the use of a high-velocity feed gas with high water vapor content was found to be particularly advantageous for obtaining high discharge power.

Non-thermal plasma-enhanced low-temperature catalytic desulfurization of electrolytic aluminum flue gas by CuO-ZrSnO4: experimental and numerical analysis

Catalytic desulfurization is favored for its ability to desulfurize low concentrations of SO₂ by generating sulfur without the need for flue gas conditioning or additives. Maintaining reaction efficiency at a low temperature would justify the industrial scale use of this method. To that end, in this study, we modified a previously reported highly efficient CuO-ZrSnO₄ catalyst and investigated its desulfurization performance. The non-thermal plasma (NTP) method was used to enhance the low-temperature efficiency of the catalyst. The desulfurization rate was significantly improved without generating excess heat or by-products in the low-output mode of post-plasma-catalysis-type (PPC-type) dielectric barrier discharge (DBD). In addition, we studied the physicochemical properties of the catalyst (pore structure, physical structure, morphology, electronic properties, and chemical state) under plasma enhancement conditions. The catalyst loaded with 20 wt% Cu and aged at 40 °C exhibited optimum desulfurization performance. This study provides a theoretical foundation for the analysis of plasma-enhanced catalytic desulfurization under low-temperature conditions. Graphical abstract.

Highly efficient decomposition of toluene using a high-temperature plasma-catalysis reactor

Plasma-catalysis technologies (PCTs) have the potential to control the emissions of volatile organic compounds, although their low-energy efficiency is a bottleneck for their practical applications. A plasma-catalyst reactor filled with a CeO₂/γ-Al₂O₃ catalyst was developed to decompose toluene with a high-energy efficiency enhanced by the elevating reaction temperature. When the reaction temperature was raised from 50 °C to 250 °C, toluene conversion dramatically increased from 45.3% to 95.5% and the energy efficiency increased from 53.5 g/kWh to 113.0 g/kWh. Conversely, the toluene conversion using a thermal catalysis technology (TCT) exhibited a maximum of 16.7%. The activation energy of toluene decomposition using PCTs is 14.0 kJ/mol, which is far lower than those of toluene decomposition using TCTs, which implies that toluene decomposition using PCT differs from that using TCT. The experimental results revealed that the Ce³⁺/Ce⁴⁺ ratio decreased and O_ads/O_latt ratio increased after the 40-h evaluation experiment, suggesting that CeO₂ promoted the formation of the reactive oxygen species that is beneficial for toluene decomposition.

Non-thermal plasma coupled with MOF-74 derived Mn-Co-Ni-O porous composite oxide for toluene efficient degradation

A novel strategy for removal of toluene by non-thermal plasma (NTP) coupled with metal-organic frameworks (MOFs) derived catalyst was proposed in this work. The MOF-derived porous trimetallic oxide catalyst (MnCoNiO_x, MCNO) was prepared by simple pyrolysis of a MOF-74(Mn-Co-Ni) precursor. We found that the MCNO material can well synergy with NTP in total decomposition of toluene owing to its high specific surface area, regular porous structure and excellent reducibility, which endow superior catalytic activity and CO₂ selectivity of NTP-MCNO system compared to that of NTP-MnO_x, NTP-CoO_x and NTP-NiO_x. For instance, the toluene degradation efficiency can reach up to 75.7% in NTP-MCNO system with a low specific input energy of 101 J/L, much higher than that of NTP-MnO_x (59.3%), NTP-CoO_x (70.9%), NTP-NiO_x (65.0%) and NTP alone (42.9%). Moreover, the formed ozone (O₃) can be well-controlled by the NTP-MCNO system due to the spinel-type oxides (MCNO) derived from MOF could generate more open-formwork structure and improve the mobility of oxygen. The results of this work would shed light on rational design and preparation of spinel-type oxides for oxidation applications, which provides guidance for further improvement of plasma-catalysis system.

Niobium doping enhanced catalytic performance of Mn/MCM-41 for toluene degradation in the NTP-catalysis system

The destruction of toluene in a dielectric barrier discharge (DBD) reactor with Nb-Mn/MCM-41 had been investigated and compared with X (X = Cu, Ce, Co)-Mn/MCM-41 catalysts. The XRD and TEM result confirms that the metal species were highly dispersed on the MCM-41. The results of XPS, O₂-TPD and H₂-TPR clearly demonstrate that Nb doping facilitated formation of lattice oxygen (O_latt) and the acid sites, which are all beneficial to catalytic degradation of toluene. Compared to X (Cu, Ce, Co)-Mn/MCM-41, Nb-Mn/MCM-41 had the most contents of O_latt, the most amounts of acid sites and the strongest acidity. Consequently, the catalytic performance tests identify that Nb-Mn/MCM-41 had the best catalytic performance, the highest removal efficiency and CO₂ selectivity as well as carbon balance especially at low SIE. These results indicate that Nb was an important promoter improving the activity and CO₂ selectivity of Mn/MCM-41 for the decomposition of toluene in NTP-catalysis system.

Decomposition of volatile organic compounds using corona discharge plasma technology

This paper explores the application of corona plasma technology as a tool in treatment of volatile organic compounds (VOCs). The review introduces the principle of corona discharge and describes the characteristics of plasma, especially of various corona plasma reactors. By summarizing the main features of such reactors, this paper provides a brief background to different power sources and reactor configurations and their application to VOC treatment design. Considering chlorinated compounds, benzene series and sulfur compounds, this paper reveals the probable mechanism of corona plasma in VOC degradation. Additionally, the effects of numerous technical parameters - such as reactor structure, shape and materials of electrodes, and humidity - are analyzed comprehensively. Product distribution, energy efficiency and economic benefits are invoked as factors to evaluate the performance of VOC degradation. Finally, the practical application of corona plasma and its advantages are briefly introduced. The review aims to illustrate the enormous potential of corona plasma technology in the treatment of VOCs, and identifies future directions. Implications: This paper comprehensively describes the principle, characteristics, research progress and engineering application examples of the degradation of volatile organics by corona discharge plasma, to provide a theoretical basis for the industrial application of this process.

Visible light promoted degradation of gaseous volatile organic compounds catalyzed by Au supported layered double hydroxides: Influencing factors, kinetics and mechanism

In this paper, factors of initial concentration, catalyst dosage, irradiation intensity, relative humidity and reaction temperature onto visible light gaseous o-xylene photodegradation by ZnCr layered double hydroxides (ZnCr-LDHs) and Au supported ZnCr-LDHs (Au/ZnCr-LDHs) were investigated. ZnCr-LDHs shows low removal efficiency for o-xylene photodegradation, while Au/ZnCr-LDHs exhibits both excellent photodegradation rate and high TOF values for o-xylene as well as other VOCs including benzene, o-xylene, m-xylene and p-xylene. The kinetic equation and activation energy were calculated for o-xylene photodegradation, which are [Formula: see text] and 21.85 kJ/mol for ZnCr-LDH [Formula: see text] and 12.84 kJ/mol for Au/ZnCr-LDHs. The obvious difference both in kinetic equation and activation energy suggests the reaction mechanism of ZnCr-LDHs and Au/ZnCr-LDHs should be very different. The active species inhabitation experiments show that the major drive of photocatalytic reaction for ZnCr-LDHs is hydroxyl radical, while for Au/ZnCr-LDHs it is the hole and hydroxide radical. It is also proved that the support of Au NPs onto LDHs would result in the transfer of photoexcited electrons from LDHs to Au NPs which results in the enhancement of photocatalytic property as well as photocatalytic mechanism change based on UV-vis, XPS, the contribution of different wavelength ranges of visible light onto photocatalytic efficiency and electrochemical tests.

Application of proton transfer reaction mass spectrometry for the assessment of toluene removal in a nonthermal plasma reactor

Proton transfer reaction mass spectrometry (PTR-MS) is a mature technique for the real-time measurement and monitoring of volatile organic compounds in the atmosphere. In this paper, a modified quantification method for PTR-MS was used to assess the performance of nonthermal plasma (NTP) reactor for the removal of toluene which was widely used in industrial production processes. Toluene and 11 corresponding organic by-products were tentatively identified and quantified by a proton transfer reaction time-of-flight mass spectrometer. The degradation dynamics of toluene and the formation of organic by-products were monitored in real-time (resolution = 1 second) under "plasma off" and "plasma on" conditions. We conclude that initial concentration and gas flow rate were the key parameters in the health risk assessment of NTP for the removal of toluene. The toluene removal efficiency and CO₂ selectivity decreased with increasing upstream toluene concentration or gas flow rate, whereas the health risk influence index increased with increasing upstream toluene concentration or gas flow rate. The highest removal efficiency of toluene (100%), CO₂ selectivity (53.2%), and the best health risk influence index for organic by-products (0.11) were achieved when the toluene concentration was kept at 105 ppmv and flow rate at 0.4 L/minute. The results demonstrate that PTR-MS is a promising tool to improve the practical applications of volatile organic compound removal by NTP because it can be used to optimize the NTP working conditions by providing a precise, fast, and clear health risk assessment for organic by-products based on their real-time analysis.

Deep Oxidation of NO by a Hybrid System of Plasma-N-Type Semiconductors: High-Energy Electron-Activated "Pseudo Photocatalysis" Behavior

A "pseudo photocatalysis" process, being initiated between plasma and N-type semiconductors in the absence of light, was investigated for NO removal for the first time via dynamic probing of reaction processes by FT-IR spectra. It was demonstrated that N-type semiconductor catalysts could be activated to produce electron-hole (e^--h⁺) pairs by the collision of high-energy electrons (e*) from plasma. Due to the synergy of plasma and N-type semiconductors, major changes were noted in the conversion pathways and products. NO can be directly converted to NO₂^- and NO₃^- instead of toxic NO₂, owing to the formation of O₂^- and ·OH present in catalysts. New species like O₃ or ·O may be generated from the interaction between catalyst-induced species and radicals in plasma at a higher SIE, leading to deep oxidation of existing NO₂ to N₂O₅. Experiments with added trapping agents confirmed the contribution of e^- and h⁺ from catalysts. A series of possible reactions were proposed to describe reaction pathways and the mechanism of this synergistic effect. We established a novel system and realized an e*-activated "pseudo photocatalysis" behavior, facilitating the deep degradation of NO. We expect that this new strategy would provide a new idea for in-depth analysis of plasma-activated catalysis phenomenon.

Crystallization of microporous TiO2 through photochemical deposition of Pt for photocatalytic degradation of volatile organic compounds

The photocatalytic mineralization efficiency of volatile organic compounds (VOCs) is determined by adsorption of reactants, separation of charge carriers, and reaction activity of catalyst surface. Herein, we provide a strategy to synthesize a novel catalyst, namely, PhPt-Micro, which is characterized by high adsorption ability, charge separation efficiency, and surface reaction activity. Toluene was chosen as the model VOC. The effects of photochemical deposition of Pt on the physical properties of microporous amorphous TiO₂ (Micro) and toluene mineralization were studied using N₂ adsorption/desorption, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, GC-flame ionization detection, and surface photovoltage spectroscopy (SPS) analyses. After photochemical treatment, the structure of Micro was optimized, and Pt nanoparticles were successfully deposited at the outlet of electrons on the catalyst surface. SPS result proved that the optimized structure enhanced the separation efficiency of charge carriers and the migration of photo-generated electrons to the PhPt-Micro surface. The quasi-equilibrium adsorption amount of toluene over PhPt-Micro was two times higher than that with commercial nano TiO₂ (P25). The micropores concentrated toluene on the catalyst surface and hindered intermediate desorption. The mineralization efficiency of toluene over PhPt-Micro was 2.4 and 5.9 times higher than those over Micro and P25, respectively.

Effects of BTEX on the Removal of Acetone in a Coaxial Non-Thermal Plasma Reactor: Role Analysis of the Methyl Group

The removal of acetone and benzene series (BTEX) under individual and concurrent conditions is carried out in a coaxial nonthermal plasma (NTP) reactor. The results show that the benzene series has a significant negative impact on acetone conversion and CO₂ selectivity under NTP treatment. Furthermore, it is found that p-xylene significantly promotes CO_x selectivity under co-treatment with acetone because of greater CO generation. Based on the results of transient FTIR, MS, and GC-MS, it is seen that quantities of formic acid, formaldehyde, and ring-opening byproducts from benzene series decomposition are reduced, while quantities of aromatic byproducts with carboxyl, phenolic, and aldehyde groups on the benzene ring increase under coexistence conditions. With the help of theoretical calculation and kinetic analysis, hydrogen abstraction from the methyl group and active hydroxyl radical consumption are proposed as critical factors in the BTEX inhibition effect on acetone degradation.

On-line quantification and human health risk assessment of organic by-products from the removal of toluene in air using non-thermal plasma

Harmful organic by-products, produced during the removal of volatile organic compounds (VOCs) from the air by treatment with non-thermal plasma (NTP), hinder the practical applications of NTP. An on-line quantification and risk assessment method for the organic by-products produced by the NTP removal of toluene from the air has been developed. Formaldehyde, methanol, ketene, acetaldehyde, formic acid, acetone, acetic acid, benzene, benzaldehyde, and benzoic acid were determined to be the main organic by-products by proton transfer reaction mass spectrometry (PTR-MS), a powerful technique for real-time and on-line measurements of trace levels of VOCs, and a health-related index (HRI) was introduced to assess the health risk of these organic by-products. The discharge power (P) is a key factor affecting the formation of the organic by-products and their HRI values. Higher P leads to a higher removal efficiency (η) and lower HRI. However, higher P also means higher cost and greater production of discharge by-products, such as NO_x and O₃, which are also very dangerous to the environment and human health. In practical applications P, HRI, and η must be balanced, and sometimes the risks posed by the organic by-products are even greater than those of the removed compounds. Our mechanistic study reveals that acetone is a crucial intermediate for the removal of toluene by NTP, and we found that toluene molecules first fragment into acetone molecules, followed by other by-products. These observations will guide the study of the mechanism of aromatic molecule dissociation in plasma.

Low-Temperature and Atmospheric Pressure Sample Digestion Using Dielectric Barrier Discharge

A new sample digestion method using a double layer and coaxial dielectric barrier discharge (DBD) digestion reactor was developed for the sensitive determination of trace elements in rice samples. All the operation parameters of the DBD microplasma and other digestion conditions were carefully optimized. Three DBD-digestion modes were investigated for real matrix samples, including H₂O-DBD-digestion, H₂O₂-DBD-digestion, and HNO₃-DBD-digestion systems. Among the three modes, the H₂O-DBD-digestion system provides a suitable digestion of sample without any additional chemicals, achieving environmental friendly sample treatment and eliminating the potential interferences. Under the optimized conditions, limits of detection for Mg, Mn, Zn, Cd, Cr, Co, and As were in the range of 0.01-0.35 ng g^-1 by inductively coupled plasma mass spectrometry (ICPMS). The accuracy of the proposed method was checked by analysis of a certified reference material (GBW10043) and spiked samples with satisfactory results (83-113% recoveries).

A comparison study of toluene removal by two-stage DBD-catalyst systems loading with MnO(x), CeMnO(x), and CoMnO(x)

This paper studies the toluene removal by a two-stage dielectric barrier discharge (DBD)-catalyst system with three catalysts: MnO(x)/ZSM-5, CoMnO(x)/ZSM-5, and CeMnO(x)/ZSM-5. V-Q Lissajous method, Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), and X-ray photoelectron (XPS) are used to characterize the DBD and catalysts. The DBD processing partially oxidizes the toluene, and the removal efficiency has a linear relationship with ozone generation. Three DBD-catalyst systems are compared in terms of their toluene removal efficiency, Fourier transform infrared (FTIR) spectra, carbon balance, CO selectivity, CO2 selectivity, and ozone residual. The results show that the DBD-catalyst system with CoMnO(x)/ZSM-5 performs better than the other two systems. It has the highest removal efficiency of about 93.7%, and the corresponding energy yield is 4.22 g/kWh. The carbon balance and CO2 selectivity of CoMnO(x)/ZSM-5 is also better than the other two catalysts. The measurements of two important byproducts including aerosols and ozone are also presented.