Non-thermal Plasma Technique Research Articles

Effect of Gliding Arc Plasma-Induced UV Light During the Photo-Fenton Oxidation of 4-Chlorophenol in Aqueous Solution

4-chlorophenol (4-CP) is recognized as a highly toxic organic which can cause damage effects on human life and the aquatic environment. Since conventional wastewater techniques were unable to remove non-biodegradable chlorophenols, advanced oxidation process was investigated to achieve this goal. Amongst them, non-thermal plasma was recently proposed as an alternative and promising technique. However, the energy efficiency of most non-thermal plasma technique is very low as well as the input energy is dissipated in many forms such as heat, UV radiation, electromagnetic waves, etc., that are not totally involved in the pollutant degradation. In this work, quantitative analyses of UV radiation and H2O2 in a moist air gliding arc plasma (glidarc) were performed using potassium ferrioxalate actinometry and peroxytitanyl complex method, respectively. The role of UV light emitted in gliding arc plasma was elucidated by performing parallel experiments: H2O2, glidarc alone, glidarc + H2O2, glidarc + H2O2 + Fe3+ (plasma-Photo-Fenton). The results show that the incorporation of Fenton reagents in 4-CP solution exposed to the plasma enhanced the yields of chemical active species, which were available for efficient removal and mineralization of 4-CP.

Recent progress of non-thermal plasma material surface treatment and functionalization

Plasma technology plays an important role in preparing and processing materials nowadays. This review focuses on the applications of non-thermal plasma (NTP) in the surface treatment and functionalization of materials, including the plasma sources for generating plasmas, NTP techniques and specific application fields. The plasma sources include inductively coupled plasma, capacitively coupled plasma, electron cyclotron resonance plasma, surface wave plasma, helicon wave plasma, atmospheric pressure plasma jet, and dielectric barrier discharge plasma. The NTP techniques for material surface treatment and functionalization include plasma surface grafting and polymerization, plasma enhanced chemical vapor deposition, plasma assisted atomic layer deposition, plasma enhanced reactive ion etching, and plasma assisted atomic layer etching. Specific applications of plasma surface treatment and functionalization cover hydrophilic/hydrophobic surface modification, surface micro-nano processing, biological tissue surface treatment, and catalyst surfaces treatment. Finally, the application prospects and development trends of NTP technology for material surface treatment and functionalization are proposed.

The Prototype of Non-thermal Plasma After treatment System for Simultaneous Reduction of Nitrogen Oxide Emission in Flue Gas

Nowadays, global warming is the main environmental problems all over the world. The air pollutants mainly from the burning of fossil fuels and coal in power plants, transportation, and automobiles. There are release major point emission of the atmosphere. The nitrogen oxides are the most relevant for air pollution that contribute to the formation of photochemical smog and acid rain. Numerous methods have been studied to eliminate the nitrogen oxides such as the use low-nitrogen fuels technology, the selective catalytic reduction (SCR), wet scrubbing. The aim of this research is investigated non-thermal plasma (NTP) techniques offer an innovation to eliminate both nitrogen oxide (NOx) and soot emissions from combustion. This study is used to selectively transfer input electrical energy to electrons without expending this in heating the entire gas flow which creates free radicals in the flue gases. The simulated flue gas from combustion process is applied to the system. The results showed that the prototype of nonthermal plasma system is shown the highly efficient of NOx removal was achieved. However, the optimised of NTP operating conditions are required to enhance the NOx reduction activities.

Evaluation of a Catalyst Packed-bed Nonthermal Plasma Reactor for VOC and PM Removal

Volatile organic compounds (VOCs) and particulate matter (PM) emitted from factories in the painting and printing industries, and various exhaust gas regulations have been implemented. VOCs are the cause of photochemical oxidants and suspended PM such as PM2.5, which has become a global environmental problem. As one of the solution technologies, catalysis nonthermal plasma (NTP) techniques have been studied as VOCs control methods. In this study, in order to extend the application to the treatment of water-soluble VOCs, a wet-type catalysis plasma reactor is proposed. As an initial step to evaluate proposed technique, the simultaneous removal of nanoparticles and toluene or typical VOCs, are performed at relatively high gas flow rates of 10 L/min. As catalyst pellets, α-alumina spheres are filled in the NTP reactor, and a MnO2 catalytic reactor is installed after the plasma reactor for ozone removal. Simultaneous removal of toluene and nanoparticles using dry and wet-type catalytic NTP reactors showed that the results used the wet-type reactor were superior in particle collection efficiency of 99%. As for the toluene removal efficiency, the dry-type was 91% and the wet-type was 73%, with the dry-type showing better results. However, the proposed wet-type catalysis NTP reactor could efficiently treat water-soluble VOCs, such as acetaldehyde and acetic acid.

Decontamination of Polymeric Surgical Sutures Covered with Bacterial Biofilms Using Nonthermal Plasma

The objective of the study was to investigate the bactericidal effectiveness of atmospheric pressure nonthermal plasma (NTP) on biofilms of Staphylococcus aureus and Escherichia coli formed on the surface of surgical sutures. Tests were carried out for polyamide nonabsorbable monofilament sutures and mid-term absorbable synthetic monofilament sutures made of glyconate. Dielectric barrier discharge reactor providing atmospheric air plasma and constant discharge power density of 70 mW/cm2 was used in the experiments. The colonization/decontamination efficacy was quantified by colony-counting assay. It was shown that decontamination efficacy of the studied surgical sutures was time-dependent i.e. the effect was more visible for longer exposure times ranging from 60 to 360 s. It was proposed to combine plasma treatment with washing the biofilms with a phosphate buffered saline to to allow the plasma to interact with cells in the deeper layers of bacterial biofilm. The application of the original method of treatment of biofilms was more effective than the separate plasma treatment. As a result, the lethal effect was most often achieved after 300 s regardless of the type of suture and biofilm. The results of the comparative studies on the decontamination efficiency of polymeric surgical suture surface by disinfectants and NTP technique have shown unequivocally that plasma treatment is the most effective way to deactivate bacterial cells and ensures a lethal effect for most of the tested cases.

Doping of nitrogen into biomass-derived porous carbon with large surface area using N2 non-thermal plasma technique for high-performance supercapacitor

A novel and facile modified method using non-thermal plasma is proposed to insert N active sites into biomass-derived porous carbon as high-performance electrode materials for supercapacitor. Large surface areas up to 3040.3 and 2662.5 m2/g with mesopore-dominant hierarchical porous carbons are produced from biomass of lilac and lotus seedpods via KOH activation, respectively. The lilac and lotus seedpods derived porous carbon electrodes present good specific capacitances of 214.5 and 201.1 F/g, respectively. N2 non-thermal plasma modification successfully increases N-containing groups on lilac and lotus seedpods derived porous carbons, where the corresponding N atomic contents are increased by 10.2 and 3.6 times, respectively. As supercapacitor electrodes, their specific capacitances are improved greatly after plasma modification and up to 342.5 F/g (increased by 59.7%) and to 332.1 F/g (increased by 65.2%) at 0.5 A/g in 6 M KOH electrolyte with excellent cycling stability of 85.2% and 95.4% at 10 A/g after 5000 cycles, respectively.

Synthesis and surface modification of light emitting silicon nanoparticles using non-thermal plasma techniques

We have synthesised silicon nanoparticles (Si-NPs) with photoluminescence ranging from blue to IR spectral region using a low-pressure RF plasma in a flow-through glass tube reactor. The spectral position of photoluminescence band of Si-NPs is controlled by the synthesis parameters such as plasma power, silane and hydrogen concentration and pressure in the working area. Modification of Si-NPs surface both on air after the synthesis and in the vacuum chamber by second plasma in methylsilane atmosphere causes a blue spectral shift of the photoluminescence band.

Regression-based models for prediction of oxides of nitrogen in diesel exhaust with electric discharge-based treatment

A prior prediction of oxides of nitrogen, i.e., NOX (sum of NO and NO2), in diesel exhaust while treating with electric discharge-based nonthermal plasma (NTP) technique, would assist the researchers in planning the resources required for the treatment. In this present study, the performance of different regression-based models, i.e., linear, support vector regression and Gaussian process regression (GPR), has been analyzed for predicting the NOX concentrations based on the values of five dominating parameters of the NTP treatment. Experiments have been conducted and collected a dataset of 4032 number of input–output pairs to be used for training and testing of the regression models. The performances of these models have been assessed while testing them for the unseen set of data. A comparison of root-mean-square error (RMSE) has been made, where Matern 3/2 type of GPR model has been found to be the best among all the considered models with an RMSE of 1.86 ppm for a test data of 1210 sets. The model is shown to perform consistently well even when the test data are increased to 50% of total data. Regression analysis shows that the NOX can be predicted with very good accuracy using the Matern 3/2 type of GPR model.

Degradation of indigo carmine in water induced by non-thermal plasma, ozone and hydrogen peroxide: A comparative study and by-product identification.

The non-thermal plasma (NTP) technique is an advanced oxidation technology (AOT) applied to the degradation of organic compounds in water. In this study, the degradation kinetics of indigo carmine was investigated systematically, applying N2-NTP, O2-NTP, ozonolysis and hydrogen peroxide and the results were compared. The transient species (OH, O and NO radicals) formed with the NTP discharge at the gas-liquid interface and their products (NO3-, NO2-, H2O2) stabilized by the water, were identified and quantified. These species contribute to the effects on the chemical characteristics of the water, such as a decrease in the pH and increase in the conductivity and redox potential. Additionally, the stabilization of the oxidative species was estimated from the degradation reactions induced by the post-discharge effect, which was significant in the case of N2-NTP, due to the presence of long-lived species, such as nitrite and nitrate. The kinetics study revealed first-order kinetics for IC color removal and the rate constant values followed the order: O2-NTP (3.0×10-1 min-1)>O3 (1.4×10-1 min-1)>N2-NTP (2.2×10-2 min-1)>H2O2 (negligible). Also the main by-products of N2-NTP, O2-NTP and ozonolysis degradation reaction were identified by ultra-fast liquid chromatography coupled with mass spectrometry. The route fragmentation showed the formation of indole intermediates, such as isatin, which is an important precursor in organic synthesis.

Cascaded Plasma–Ozone Injection System: A Novel Approach for Controlling Total Hydrocarbon Emission in Diesel Exhaust

The hydrocarbons present in diesel exhaust, although treated as minor pollutants, are equivalent to some of the major pollutants in terms of toxicity, contamination and harmfulness to the environment and hence, any effort towards treating hydrocarbons is a welcome step before letting the same into the atmosphere. In this current work two non-thermal plasma techniques viz., electrical discharge plasma (direct plasma) and ozone injection (indirect plasma) were coupled while treating the diesel exhaust for possible mitigation of total hydrocarbons (THC). The work is intended to provide a cleaning system which is non-catalytic, non-adsorbent and non-thermal plasma based one leading to less utilization of electrical energy and long lasting. The study was conducted at laboratory level with controlled flow conditions of the diesel exhaust. It was observed that the combined discharge plasma and ozone injection has resulted in more of THC reduction/conversion to the tune of 95% at about plasma specific energy of 55 J/L and with an injection of 1656 ppm of ozone. The individual as well as cascaded treatment techniques are discussed in detail and a comparative analysis of the same has been provided.

Prediction of NO and NO2 Concentrations in NTP Treated Diesel Exhaust Using Multilayer Perceptrons

Non-thermal plasma technique (NTP) for mitigation of NOX from diesel engine exhaust is a laboratory proven technique with a good number of experimental studies. However, there are constraints which are preventing this technique to appear in practical applications. Prior prediction of exhaust characteristics with the NTP treatment according to the variations in its operating parameters can be a step ahead to make this technique applicable in real time. In this present study, experiments are conducted by varying parameters voltage, flow rate, temperature, discharge gap and initial sum of NO and NO2 concentrations. Six hundred number of datasets are collected to train and test the predictive models which are made using multilayer perceptrons (MLP). The objective of these models is to predict the sum of NO and NO2 concentrations at the downstream of the reactor during NTP based diesel exhaust treatment. As a part of the study, optimum number of neurons in the hidden layers is also found out. The root mean square error (RMSE) of an MLP with two hidden layers, each of 20 neurons, is found to be 3.29 ppm. Results assure that the prediction of sum of NO and NO2 concentrations can be achieved with a good accuracy using MLP.

Response surface methodology-based model for prediction of NO and NO2 concentrations in nonthermal plasma-treated diesel exhaust

Nonthermal plasma (NTP) technique for diesel exhaust emission control has been in the interest of the researchers from the last two decades, and it almost became a laboratory-proven technique for its efficiency over conventional techniques. A prior prediction of effectiveness of the process may lead to overcome the constraints in bringing this technique to real-time applications of diesel exhaust pollution control. In this present study, an attempt is made to find out the most dominating parameters and to predict the sum of NO and NO2 concentrations in NTP-treated diesel exhaust with respect to variations in operating parameter values using response surface methodology (RSM). Experiments have been conducted following 3N full factorial design and collected the data by varying voltage, flow rate, temperature, discharge gap and initial (NO + NO2) concentrations. The regression coefficients of the RSM-based mathematical model have been obtained by training it using these experimental data. The root-mean-square error (RMSE) is 4.7 ppm during the training. When this model is tested for a data other than that given during training (test data), the RMSE is 5.6 ppm. Further, the results are also compared with the model derived using the only available method in the literature, i.e., dimensional analysis, and found to be performing better.

The Use of Zeolites for VOCs Abatement by Combining Non-Thermal Plasma, Adsorption, and/or Catalysis: A Review

Non-thermal plasma technique can be easily integrated with catalysis and adsorption for environmental applications such as volatile organic compound (VOC) abatement to overcome the shortcomings of individual techniques. This review attempts to give an overview of the literature about the application of zeolite as adsorbent and catalyst in combination with non-thermal plasma for VOC abatement in flue gas. The superior surface properties of zeolites in combination with its excellent catalytic properties obtained by metal loading make it an ideal packing material for adsorption plasma catalytic removal of VOCs. This work highlights the use of zeolites for cyclic adsorption plasma catalysis in order to reduce the energy cost to decompose per VOC molecule and to regenerate zeolites via plasma.

Plasma Farming: Non-Thermal Dielectric Barrier Discharge Plasma Technology for Improving the Growth of Soybean Sprouts and Chickens

Non-thermal dielectric barrier discharge (DBD) plasma is an innovative and emerging field combining plasma physics, life science and clinical medicine for a wide-range of biological applications. Plasma techniques are applied in treating surfaces, materials or devices to realize specific qualities for subsequent special medical applications, plant seeds to improve the production and quality of crops, and living cells or tissues to realize therapeutic effects. Several studies that are summarized within this review show that non-thermal DBD plasma technique has potential biological applications in soybean sprout growth, chicken embryonic development and postnatal growth rate, and even male chicken reproductive capacity. The current developments in the non-thermal DBD plasma technique may be beneficial to improve plant and poultry productivity.

Design of O2/SO2 dual-doped porous carbon as superior sorbent for elemental mercury removal from flue gas.

A porous carbon was synthesized via hydrothermal carbonization and CO2 activation. O2 and SO2 were successfully co-doped onto carbon surface by applying non-thermal plasma technique. Porous carbon possessing excellent textural properties is effective to adsorb the radicals generated by plasma. Plasma promotes the adsorption of O2 and SO2 on carbon surface with the formation of abundant CO, C-S and C-SOx (x = 1-3) groups. The O2/SO2 dual-doped porous carbon was utilized to adsorb elemental mercury (Hg0) from the flue gas of coal combustion. The Hg0 adsorption ability of the O2/SO2 dual-doped porous carbon is closely related with the concentrations of O2 and SO2 for plasma treatment and the treatment time. The optimal O2/SO2 dual-doped porous carbon exhibited far greater Hg0 adsorption capacity than a commercial brominated activated carbon. Density functional theory was employed to understand the Hg0 adsorption mechanism at the molecular level. CO, C-S and C-SOx (x = 1-3) groups enhanced the interaction of Hg0 with surface carbon atom. The activity of them for enhancing Hg0 adsorption is in the order of C-SO2 > CO > C-S > C-SO > C-SO3. Porous carbon can be activated by plasma in flue gas containing O2 and SO2, and used as superior sorbent for Hg0 removal.

Plasma Assisted Catalytic Conversion of CO2 and H2O Over Ni/Al2O3 in a DBD Reactor

We present an innovative approach for reacting carbon dioxide and water to give syngas by combining heterogeneous catalysis and non-thermal plasma techniques. This approach utilizes an abundant water and nickel catalyst, and mitigates the thermodynamic penalty by using a Dielectric Barrier Discharge (DBD) plasma reactor. Argon dilution was used in the experiment to reduce the exothermic recombination of hydrogen and oxygen, which is considered as the major hurdle for H2O conversion. As a result, the syngas ratio was dramatically improved from 0.07 to 0.86. In addition, the conversions of CO2 and H2O were improved by packing Ni/γ–Al2O3 catalysts into the DBD reactor. The yields of H2 and CO were up to 13.8% and 5.6% respectively. The conditions for plasma catalysis and the catalyst characterization are presented and discussed.

Innovative Approach of Non-Thermal Plasma Application for Improving the Growth Rate in Chickens.

As an innovative technology in biological applications—non-thermal plasma technique—has recently been applied to living cells and tissues. However, it is unclear whether non-thermal plasma treatment can directly regulate the growth and development of livestock. In this study, we exposed four-day-incubated fertilized eggs to plasma at 11.7 kV for 2 min, which was found to be the optimal condition in respect of highest growth rate in chickens. Interestingly, plasma-treated male chickens conspicuously grew faster than females. Plasma treatment regulated the reactive oxygen species homeostasis by controlling the mitochondrial respiratory complex activity and up-regulating the antioxidant defense system. At the same time, growth metabolism was improved due to the increase of growth hormone and insulin-like growth factor 1 and their receptors expression, and the rise of thyroid hormones and adenosine triphosphate levels through the regulation of demethylation levels of growth and hormone biosynthesis-related genes in the skeletal muscles and thyroid glands. To our knowledge, this study was the first to evaluate the effects of a non-thermal plasma treatment on the growth rate of chickens. This safe strategy might be beneficial to the livestock industry.

MicroRNA-7450 regulates non-thermal plasma-induced chicken Sertoli cell apoptosis via adenosine monophosphate-activated protein kinase activation

Non-thermal plasma treatment is an emerging innovative technique with a wide range of biological applications. This study was conducted to investigate the effect of a non-thermal dielectric barrier discharge plasma technique on immature chicken Sertoli cell (SC) viability and the regulatory role of microRNA (miR)-7450. Results showed that plasma treatment increased SC apoptosis in a time- and dose-dependent manner. Plasma-induced SC apoptosis possibly resulted from the excess production of reactive oxygen species via the suppression of antioxidant defense systems and decreased cellular energy metabolism through the inhibition of adenosine triphosphate (ATP) release and respiratory enzyme activity in the mitochondria. In addition, plasma treatment downregulated miR-7450 expression and activated adenosine monophosphate-activated protein kinase α (AMPKα), which further inhibited mammalian target of rapamycin (mTOR) phosphorylation in SCs. A single-stranded synthetic miR-7450 antagomir disrupted mitochondrial membrane potential and decreased ATP level and mTOR phosphorylation by targeting the activation of AMPKα, which resulted in significant increases in SC lethality. A double-stranded synthetic miR-7450 agomir produced opposite effects on these parameters and ameliorated plasma-mediated apoptotic effects on SCs. Our findings suggest that miR-7450 is involved in the regulation of plasma-induced SC apoptosis through the activation of AMPKα and the further inhibition of mTOR signaling pathway.

Advanced meat preservation methods: A mini review

AbstractDevelopment of various novel thermal and nonthermal techniques has shown potential applications in meat processing and preservation. Consumer's demand of meat products with esteemed quality, wholesomeness, and superior safety has led to the commercial introduction of these innovative methods. Accordingly, this treatise outlines the potential of several advanced thermal and nonthermal methods like super‐chilling, ultrarapid freezing, immersion vacuum cooling, hydrofluidization freezing, impingement freezing, electrostatic‐assisted freezing, pressure‐shift freezing, acidic electrolyzed water coupled with high hydrostatic pressure, and nonthermal plasma technique for preserving meat quality and prolongation of shelf stability. This article also highlights the advancements in the packaging technology like use of linear low‐density polyethylene‐based active clay nanocomposite films and resulted benefits for the meat sector. Additionally, consumer responses to various meat products preserved with these technologies are also discussed in this critique. The focal objective of the current discourse is to reconnoiter the aptitude of these novel techniques in meat preservation so that these methods can be adopted at commercial scale in a much broader sense.Practical applicationsFor decades, several methods have been adopted for preservation of meat. With technological advancements, meat industry is looking for some modern and economic preservation methods for meat and meat‐based products. In this regard, several nonconventional techniques like super‐chilling, hydrofluidization freezing, impingement freezing, electrostatic‐assisted freezing, and pressure‐shift freezing have shown their potential for effective meat preservation. Therefore, this article will be helpful for the meat industrialists to consider these techniques for commercial preservation of meat and meat products in a more effectual manner.

Augmenting NO x reduction in diesel exhaust by combined plasma/ozone injection technique: a laboratory investigation

With the advent of non-thermal plasma technique for diesel exhaust treatment attention is being focused on reducing oxides of nitrogen (NO x ) both from stationary as well as automobile sources. In this work, an attempt has been made to enhance NO x reduction only by utilising a plasma/ozone injection approach without resorting to additional treatments based on catalysts/adsorbents. It was observed that cascading ozone injection with discharge plasma enhances the reduction of NO x as high as 95% for the specific energy of 123 J/l. In the long run, this plasma-only based approach may be beneficial or a possible alternative for catalyst/adsorbent based NO x treatments. The results have been discussed and a comparative analysis has been made with respect to individual plasma and ozone injection treatment.