Plasma-generated Reactive Species Research Articles

Examining plasma-generated ozone and nitric oxide's role in synthetic textile dye water remediation and ecotoxicological analysis

Synthetic dyes produced by the textile dyeing industry and released into wastewater contribute significantly to water pollution. This study explores the efficacy and versatility of a novel multi-electrode dielectric barrier discharge (MEDBD) plasma system that mainly generates ozone (O3 generator) and nitric oxide (NO generator) selectively to degrade various synthetic textile dyes, namely Methylene Blue (MB), Congo Red (CR), Methyl Orange (MO), Crystal Violet (CV), and Evans Blue (EB). Plasma achieved selective enrichment of O3 and NO by utilizing optimized plasma generation duty cycles of 15% and 100%, respectively. The proposed O3 generator plasma involves plasma-generated aqua electron impact, excited species, and reactive oxygen species notably O3, which degrades synthetic textile dyes into simple forms such as CO2, H2O, and N2. This approach achieved over 95% degradation of the above synthetic textile dyes when employing the O3 enriched plasma with 2.44 ± 0.21 W of power. Ecotoxicological evaluation, including microbial, human cell, and phytotoxicity evaluations of the O3 generator plasma for MB and CR dye-contaminated water, underscored the potential of this plasma system for environmentally friendly dye degradation. Overall, this study promotes MEDBD plasma, particularly the O3 generator, as a sustainable and efficient solution for treating synthetic dye-contaminated water across industries.

Plasma-catalytic dry reforming of CH4: Effects of plasma-generated species on the surface chemistry

By means of steady-state experiments and a global model, we studied the effects of plasma-generated reactive species on the surface chemistry and coking in plasma-catalytic CH4/CO2 reforming at reduced pressure (8–40 kPa). We used a hybrid ZDPlasKin-CHEMKIN model to predict the species densities over time. The detailed plasma-catalytic mechanism consists of the plasma discharge scheme, a gas-phase chemistry set and a surface mechanism. Our experimental results show that the coupling of Ni/SiO2 catalyst with plasma is more effective in CH4/CO2 activation and conversion than unpacked DBD plasma, with syngas being the main products. The highest total conversion of 16 % was achieved at 8000 V and 473 K, with corresponding CO and H2 yields of 15 % and 12 %, respectively. The reactants conversion and product selectivity are well captured by the kinetic model. Our simulation results suggest that vibrational species and radicals can accelerate the dissociative adsorption and Eley-Rideal (E-R) reactions. Path flux analysis shows that E-R reactions dominate the surface reaction pathways, which differs from thermal catalysis, indicating that the coupling of non-equilibrium plasma and catalysis can effectively shift the formation and consumption pathways of important adsorbates. For instance, our model suggests that HCOO(s) is primarily generated through the E-R reaction CO2(v) + H(s) → HCOO(s), while the hydrogenation reaction HCOO(s) + H → HCOOH(s) is the main source of HCOOH(s). Carbon deposition on the catalyst surface is primarily formed through the stepwise dehydrogenation of CH4, while the E-R reactions enhanced by plasma-generated H and O atoms dominate the consumption of carbon deposition. This work provides new insights into the effects of reactive species on the surface chemistry in plasma-catalytic CH4/CO2 reforming.

Multiple RONS-Loaded Plasma-Activated Ice Microneedle Patches for Transdermal Treatment of Psoriasis.

Cold atmospheric plasma (CAP) is a fledgling therapeutic technique for psoriasis treatment with noninvasiveness, but clinical adoption has been stifled by the insufficient production and delivery of plasma-generated reactive oxygen and nitrogen species (RONS). Herein, patches of air-discharge plasma-activated ice microneedles (PA-IMNs) loaded with multiple RONS are designed for local transdermal delivery to treat psoriasis as an alternative to direct CAP irradiation treatment. By mixing two RONS generated by the air-discharge plasma in the NOx mode and O3 mode, abundant high-valence RONS are produced and incorporated into PA-IMNs via complex gas-gas and gas-liquid reactions. The PA-IMNs abrogate keratinocyte overproliferation by inducing reactive oxygen species (ROS)-mediated loss of the mitochondrial membrane potential and apoptosis of keratinocytes. The in vivo transdermal treatment confirms that PA-IMNs produce significant anti-inflammatory and therapeutic actions for imiquimod (IMQ)-induced psoriasis-like dermatitis in mice by inhibiting the release of associated inflammatory factors while showing no evident systemic toxicity. Therefore, PA-IMNs have a large potential in transdermal delivery platforms as they overcome the limitations of using CAP directly in the clinical treatment of psoriasis.

The effect of bending angle on a flexible electrode DBD plasma under sinusoidal excitation

There is a critical demand for sophisticated surface disinfection and sterilization devices accessible to the public by using cold atmospheric pressure air plasmas. A flexible printed circuit design of a dielectric barrier discharge reactor under non-bending and two bending configurations with an angle of 120° and 180° was studied. The characteristics of power consumption, the optical emission spectrum, dynamic process, electrode temperature and ozone concentration are evaluated. The non-bending configuration produces more O3, as compared to the bending configuration at the same applied voltage. The 180° configuration has a maximum concentration of excited species at the expense of higher electrode temperature. Both bending configurations demonstrated the propagation of filaments to bending axis where the continues luminescence is observed due to the high electrical field. The energy efficiency for plasma-generated reactive species reaches to 40% for non-bending configuration and decreases with the increase of bending angle. This research provides a new strategy for perspective into the plasma generated reactive species in biomedical and environmental applications.

Evidence for Superoxide-Initiated Oxidation of Aniline in Water by Pulsed, Atmospheric Pressure Plasma.

Plasma-driven solution electrochemistry (PDSE) uses plasma-generated reactive species to drive redox reactions in solution. Nonthermal, atmospheric pressure plasmas, when irradiating water, produce many redox species. While PDSE is a promising chemical tool, there is limited insight into the mechanisms of the reactions due to the variety of short-lived reagents produced. In this study, we use aniline as a model system for studying redox mechanisms of PDSE. We show that the plasma irradiation of aqueous aniline solutions drives the formation of polyaniline oligomer, which is suppressed under acidic starting conditions. The addition of (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO), a radical scavenger, decreases the formation of oligomer by 80%, and the addition of superoxide dismutase fully hinders oligomerization. These results lead us to conclude that the oligomerization of aniline by plasma irradiation is initiated by superoxide. This discovery provides novel insights into PDSE mechanisms and illustrates a potential method of harnessing superoxide for chemical reactions.

Human coronavirus 229E inactivation on porous and nonporous materials using dielectric barrier discharge (DBD) plasma.

Viruses can spread through contaminated aerosols and contaminated surface materials, and effective disinfection techniques are essential for virus inactivation. Nonthermal plasma-generated reactive oxygen and nitrogen species can effectively inactivate the coronavirus. We aim to interpret the coronavirus inactivation level and mechanism of surface interaction with materials with and without dielectric barrier discharge (DBD) plasma treatment. Nonthermal plasma, particularly surface-type DBD plasma, can inactivate human coronavirus 229E (HCoV-229E) on porous (paper, wood, mask) and nonporous (plastic, stainless steel, glass, Cu) materials. Virus inactivation was analyzed using a 50% tissue culture infectivity dose (TCID50) using cell line, flow cytometry, and immunofluorescence. Surfaces contaminated with HCoV-229E were treated at different time intervals (0-5 h) with and without plasma exposure (natural decay in ambient air conditions). HCoV-229E persistence conformed to the following order: plastic > cover glass > stainless steel > mask > wood > paper > Cu with and without plasma exposure. HCoV-229E was more stable in plastic, cover glass, and stainless steel in 5 h, and the viable virus titer gradually decreased from its initial log10 order of 6.892 to 1.72, 1.53, and 1.32 TCID50/mL, respectively, under plasma exposure. No virus was observed in Cu after treatment for 5 h. The use of airflow, ambient nitrogen, and argon did not promote virus inactivation. Flow cytometry and immunofluorescence analysis demonstrated a low expression level of spike protein (fluorescence intensity) during plasma treatment and in E and M genes expression compared with the virus control.

Treatment of seeds by cold ambient air plasma: combining impedance measurements with water sorption modeling to understand the impact of seed hydration

In this article, we focus on the plasma seed interaction and more specifically-on the feedback exerted by the seeds on the plasma properties. Dormant Arabidopsis seeds with different water contents (WC), namely 3%DW, 10%DW and 30%DW were exposed to cold ambient air plasma (C2AP) generated in a dielectric barrier device (DBD). It is found that increasing WC enhances the capacitive current of the DBD, generates a greater number of low energy streamers (characterized by current peaks lower than 10 mA) that preferentially interplay with the seeds. Since the resistive and capacitive components of the seeds modify the C2AP electrical properties, impedance measurements (also called LCRmetry) have been carried out to measure their main dielectric parameters before/after plasma exposure (seeds resistance, capacitance, complex relative permittivity, tangent loss and conductivity). It appears that WC significantly changes dielectric losses at low frequencies (<1 kHz) due to polarization relaxation of the polar molecules (i.e. water). LCRmetry further reveals that C2AP does not substantially alter seeds dielectric parameters, i.e. it neither adds or removes significant amounts of new materials, meaning that the relative starch, protein and lipid contents remain essentially unaffected. However, it cannot be discounted that some bulk properties of the Arabidopsis seeds may be modified, especially regarding their porosity. This characteristic could facilitate penetration of plasma-generated reactive oxygen species into the internal seed tissues, leading to the grafting of oxygenated groups. To corroborate this theory, water sorption isotherms have been achieved on Arabidopsis seeds and fitted with four thermodynamic models, including the Brunauer–Emmett–Teller model and the Generalized D’Arcy and Watt model. It is demonstrated that C2AP primarily strengthens water-seed affinity by modifying molecular interactions rather than changing the seed’s moisture layer. This occurs despite a potential decrease in the number of adsorption sites, indicating a significant increase in overall seed hydrophilicity after plasma treatment.

Non-thermal atmospheric-pressure positive pulsating corona discharge in degradation of textile dye Reactive Blue 19 enhanced by Bi2O3 catalyst

In this work, monoclinic Bi2O3 was applied for the first time, to the best of our knowledge, as a catalyst in the process of dye degradation by a non-thermal atmospheric-pressure positive pulsating corona discharge. The research focused on the interaction of the plasma-generated species and the catalyst, as well as the role of the catalyst in the degradation process. Plasma decomposition of the anthraquinone reactive dye Reactive Blue 19 (RB 19) was performed in a self-made reactor system. Bi2O3 was prepared by electrodeposition followed by thermal treatment, and characterized by x-ray diffraction, scanning electron microscopy and energy-dispersive x-ray techniques. It was observed that the catalyst promoted decomposition of plasma-generated H2O2 into •OH radicals, the principal dye-degrading reagent, which further attacked the dye molecules. The catalyst improved the decolorization rate by 2.5 times, the energy yield by 93.4% and total organic carbon removal by 7.1%. Excitation of the catalyst mostly occurred through strikes by plasma-generated reactive ions and radical species from the air, accelerated by the electric field, as well as by fast electrons with an energy of up to 15 eV generated by the streamers reaching the liquid surface. These strikes transferred the energy to the catalyst and created the electrons and holes, which further reacted with H2O2 and water, producing •OH radicals. This was indentified as the primary role of the catalyst in this process. Decolorization reactions followed pseudo first-order kinetics. Production of H2O2 and the dye degradation rate increased with increase in the input voltage. The optimal catalyst dose was 500 mg∙dm−3. The decolorization rate was a little lower in river water compared with that in deionized water due to the side reactions of •OH radicals with organic matter and inorganic ions dissolved in the river water.

Coupling the COST reference plasma jet to a microfluidic device: a computational study

The use of microfluidic devices in the field of plasma-liquid interaction can unlock unique possibilities to investigate the effects of plasma-generated reactive species for environmental and biomedical applications. So far, very little simulation work has been performed on microfluidic devices in contact with a plasma source. We report on the modelling and computational simulation of physical and chemical processes taking place in a novel plasma-microfluidic platform. The main production and transport pathways of reactive species both in plasma and liquid are modelled by a novel modelling approach that combines 0D chemical kinetics and 2D transport mechanisms. This combined approach, applicable to systems where the transport of chemical species occurs in unidirectional flows at high Péclet numbers, decreases calculation times considerably compared to regular 2D simulations. It takes advantage of the low computational time of the 0D reaction models while providing spatial information through multiple plug-flow simulations to yield a quasi-2D model. The gas and liquid flow profiles are simulated entirely in 2D, together with the chemical reactions and transport of key chemical species. The model correctly predicts increased transport of hydrogen peroxide into the liquid when the microfluidic opening is placed inside the plasma effluent region, as opposed to inside the plasma region itself. Furthermore, the modelled hydrogen peroxide production and transport in the microfluidic liquid differs by less than 50% compared with experimental results. To explain this discrepancy, the limits of the 0D–2D combined approach are discussed.

Harnessing plasma-generated reactive species for the synthesis of different phases of molybdenum oxide to study adsorption and photocatalytic activity.

This study employs plasma-liquid interaction technique to synthesize different phases of molybdenum oxide using air and argon as plasma-forming gases. In situ plasma-generated nitrogen species primarily NO3-/NO2- and hydrogen species (H+) facilitate the reduction of the molybdenum precursor anion (Mo7O24-). The reduced Mo species subsequently reacts with reactive oxygen species, forming MoO6 octahedra, which is the building block of a molybdenum oxide crystal. Varied concentrations of NO3-/NO2- and H+ species in air and argon plasma treatment significantly influence the growth process. Air plasma synthesis yields hexagonal molybdenum oxide microrods, which upon calcination changes its phase to orthorhombic 2D layered structure. Moreover, the argon plasma synthesized sample exhibits a mixed phase of hexagonal and orthorhombic molybdenum oxide due to the heavy argon ion bombardment, inducing material porosity and surface oxygen vacancies. The mixed-phase material exhibits superior adsorption and photo-degradation towards cationic dye compared to the other two phases. The higher photocatalytic performance may be responsible for the extended lifetime of the photo-generated charge carriers possessed by the mixed-phase material. Radical scavenging tests have identified holes and hydroxyl radicals as the key reactive species that take part in the photo-degradation process.

The potential of multicylindrical dielectric barrier discharge plasma for diesel-contaminated soil remediation and biocompatibility assessment

This study explored the use of multicylindrical dielectric barrier discharge (MC–DBD) plasma technology to eliminate diesel fuel contamination from the soil. This study also assessed the environmental impact of plasma-generated reactive species on soil properties, plant growth, and the safety of microbial and human skin cells using various analytical methods. MC–DBD plasma was characterized using the current–voltage analysis and optical emission spectroscopy (OES). Gas Fourier transform infrared spectroscopy was employed to detect reactive species, such as O3, NO, NO2, N2O, and HNO3, in the plasma-treated air. The diesel fuel concentration in the soil was measured before and after plasma treatment using a gas chromatography–flame ionization detector. The efficacy of the MC–DBD plasma treatment was evaluated based on soil characteristics (pH and moisture), discharge parameters (power), and reactive species (O3 and NOx). Using only power of 30 W, the MC–DBD achieved a 94.19% removal of diesel fuel from the soil and yielded an energy efficiency of 1.78 × 10−2 m3/kWh within a 60-min treatment period. Neutral soil with a moisture content of 2% proved more effective in diesel fuel removal compared with acidic or alkaline soil with higher moisture content. O3 was the most efficient plasma-generated reactive species for diesel fuel removal and is involved in oxidation-induced fragmentation and volatilization. Overall, the potential of the MC–DBD plasma technology for remediating diesel fuel-contaminated soils is highlighted, and valuable insights for future applications are provided.

Highlight the plasma-generated reactive oxygen species（ROSs）dominant to degradation of emerging contaminants based on experiment and density functional theory

This paper aims to deeply analyze the degradation mechanism of emerging contaminants by dielectric barrier discharge (DBD) plasma through experiments and simulations. It was confirmed that DBD plasma exhibits a high degradation effect on three emerging contaminants by the generated reactive oxygen species (ROSs). Increasing the output power leads to higher ROSs production and higher degradation rates of emerging contaminants. At an input power of 94.6 W, the degradation rates of sulfamethoxazole (SMX), bisphenol A (BPA) and ciprofloxacin (CIP) reach 94.5 %, 92.9 %, and 98.6 %, respectively. Trapping agent experiments were conducted to investigate the role of ROSs (·OH, ·O2–, and 1O2) in emerging contaminants degradation. Notably, capturing of 1O2 led to a decrease of up to 31 % in the degradation rate of BPA. Electron spin resonance (ESR) tests confirmed the involvement of various ROSs, especially 1O2, in the degradation process. Density functional theory (DFT) was employed to further explore the action mechanism of ROSs in the DBD plasma system. For SMX and BPA, the degradation is initiated by the dissociation of annular structures, while for CIP, annular structures are directly opened by ROSs. These findings highlight the importance of 1O2 and ·OH in the degradation process. Finally, the toxicity of intermediates produced by ROSs-dominate to degradation was declined. This work can provide new insights and unique guidance on the plasma degradation mechanism of emerging contaminants.

Persistence of Coronavirus on Surface Materials and Its Control Measures Using Nonthermal Plasma and Other Agents.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been responsible for the initiation of the global pandemic since 2020. The virus spreads through contaminated air particles, fomite, and surface-contaminated porous (i.e., paper, wood, and masks) and non-porous (i.e., plastic, stainless steel, and glass) materials. The persistence of viruses on materials depends on porosity, adsorption, evaporation, isoelectric point, and environmental conditions, such as temperature, pH, and relative humidity. Disinfection techniques are crucial for preventing viral contamination on animated and inanimate surfaces. Currently, there are few effective methodologies for preventing SARS-CoV-2 and other coronaviruses without any side effects. Before infection can occur, measures must be taken to prevent the persistence of the coronavirus on the surfaces of both porous and non-porous inanimate materials. This review focuses on coronavirus persistence in surface materials (inanimate) and control measures. Viruses are inactivated through chemical and physical methods; the chemical methods particularly include alcohol, chlorine, and peroxide, whereas temperature, pH, humidity, ultraviolet irradiation (UV), gamma radiation, X-rays, ozone, and non-thermal, plasma-generated reactive oxygen and nitrogen species (RONS) are physical methods.

Plasma–liquid interactions: an experiment and simulation study on plasma dynamic behaviors near the gas–liquid interfacial layer

Plasma–liquid interaction processes are essential to various plasma applications such as sewage disposal, biomedicine, and synthesis of nanomaterials. However, the near gas–liquid interfacial behavior of plasma property remains inadequately understood, hindering the controllability of the application process. This study combines experimental diagnostics and simulations to investigate the production and transport of plasma-generated reactive species near (∼35 μm) the gas–liquid interfacial layer. The experimental results are used to benchmark densities obtained from a zero-dimensional plasma chemical kinetics simulation, which reveals the time evolutions of plasma-generated active species. A large number of neutral particles (like OH, H2O2) and water cluster ions (like H9O4 +) were produced as a result of the evaporation effect of the cathode solution surface. The estimation of energy flux from the gaseous plasma to liquid surface showed that the hydration process of positive ions plays the key role in the resulted water evaporation at the gas–liquid interfacial layer.

Global numerical simulation of chemical reactions in phosphate-buffered saline (PBS) exposed to atmospheric-pressure plasmas

Abstract When a phosphate-buffered saline (PBS) solution is exposed to atmospheric-pressure plasmas generated in air, hydrogen peroxide H 2 O 2 in the solution is known to be decomposed by hypochlorite O C l − , which is formed in the solution from reactions between chlorine ions C l − present in the PBS solution and plasma-generated reactive oxygen species. Global numerical simulations of liquid-phase chemical reactions were performed to identify the reaction mechanisms of H 2 O 2 decomposition by solving known liquid-phase chemical reactions self-consistently. It has been confirmed that the decomposition of H 2 O 2 is indeed mostly due to the presence of O C l − in the solution. However, this study has also found that, in the presence of abundant hydroxyl ( O H ) radicals, the most efficient H 2 O 2 decomposition pathway can be a series of reactions that we call a chlorine monoxide cycle, where O C l − first reacts with O H to generate chlorine monoxide C l O , which then decomposes H O C l , rather than O C l − directly decomposing H 2 O 2 . The chlorine monoxide cycle generates O H as one of its byproducts, so once this cycle is initiated, it continues until either C l O − or H 2 O 2 runs out, as long as none of the intermediates are scavenged by other reactions.

Mechanistic study on the synergy of cold plasma and sulfate radical in the degradation of azo and triarylmethane dyes using density functional theory

The activation of persulfate using cold plasma and the synergy of plasma-generated reactive species and SO4•− in mineralization of organic dyes were assessed. In this regard, solutions of crystal violet (CV) as a triarylmethane dye and methyl orange (MO) as an azo dye, were treated with cold plasma, UV-C-activated sulfate radicals, and their combination. The achieved results showed 95% TOC removal, a synergy factor of 1.3 and an energy yield of 1.68 (g kWh−1) for the combined system. The contribution of oxidant species in CV (SO4•− > O2•- > •OH) and MO (SO4•−> O2•- >1O2) degradation was explored. Moreover, analysis of degradation products and density functional theory (DFT) calculations were adopted to find the degradation mechanism based on the minimum energy pathway. Experimental and DFT results revealed that while radical and nucleophilic pathways were the drivers of CV degradation, the electrophilic attack of oxidants was a more plausible mechanism for MO degradation. Additionally, a comparison of the results of different DFT methods with experimental values showed that the Kohn–Sham DFT yielded more accurate results compared to recommended double hybrid methods. Analysis of a treated real wastewater revealed that the background constituents had negligible effects on MO and CV degradation. The high TOC removal efficiency of the combined system suggests its feasibility for treating wastewater from fertilizer and pharmaceutical production facilities.

Coupling the COST reference plasma jet to a microfluidic device: a new diagnostic tool for plasma-liquid interactions

Plasma-liquid interaction processes are central to plasma applications in medicine, environment, and material processing. However, a standardized platform that allows the study of the production and transport of plasma-generated reactive species from the plasma to the liquid is lacking. We hypothesize that use of microfluidic devices would unlock many possibilities to investigate the transport of reactive species in plasma-treated liquids and, ultimately, to measure the effects of these species on biological systems, as microfluidics has already provided multiple solutions in medical treatment investigations. Our approach combines a capacitively coupled RF plasma jet known as the COST reference plasma jet with simple 3D printed microfluidic devices. This novel pairing is achieved by carefully controlling capillary effects within the microfluidic device at the plasma-liquid interaction zone. The generation and transport of reactive species from the plasma to the liquid inside the microfluidic device are analyzed using a colorimetric hydrogen peroxide concentration assay. A capillary flow model is provided to explain the two main regimes of operations observed in the device and their merits are discussed. Overall, the proposed plasma-microfluidic prototype shows great potential for the fundamental study of plasma-liquid interactions and opens the way to the use of standard microfluidic devices with plasma sources developing a plasma column or a plasma plume.

Influence of a transient spark plasma discharge on producing high molecular masses of chemical products from l-cysteine

Cold atmospheric pressure plasmas are considered a forthcoming method in many research areas. Plasma modification of biomolecules has received much attention in addition to plasma-treated biomaterials. Hence, in this work, we operated a transient spark plasma (TSP) discharge to study its effect on the l-cysteine chemical structure. the TSP was configured in a pin-to-ring electrode arrangement and flowed by Ar gas. We also investigated the effect of two chemicals; dimethyl sulfoxide (DMSO) and hydrogen peroxide (H2O2) by the bubbling method to show how they can change the creation of new chemical bioproducts. Ultraviolet–Visible absorption spectroscopy, Fourier transform infrared spectroscopy and Liquid chromatography–mass spectroscopy were used to investigate any changes in chemical bonds of cysteine structure and to depict the generation of new biomolecules. Based on the displayed results plasma-generated reactive species had a great role in the chemical structure of the cysteine. Entering DMSO and H2O2 into the plasma caused the creation of new products and the heaviest biomolecule was produced by the simultaneous addition of DMSO and H2O2. The results also predicted that some chemical products and amino acids with a higher value molecular masse produced from the polymerization process of cysteine solution. The strong oxidation process is responsible for the heavy chemical compounds.

Power dependence of reactive species generation in a water falling film dielectric barrier discharge system

The short-lived and long-lived reactive species generated in plasma-liquid interactions determine their potential applications in wastewater purification and plant growth stimulation. In this work, plasma-generated reactive species including hydroxyl radicals (∙OH), hydrogen peroxide (H2O2), ozone (O3), hydronium (H3O+), and nitrate (NO3-) were quantified in a water falling film dielectric barrier discharge system. The reaction kinetics of short-lived ∙OH were analyzed based on the quantification of ∙OH and degradation of salicylic acid, focusing on the contribution and utilization of ∙OH. The interconversion of ∙OH with H2O2 and O3 was also calculated. The accumulation rates of H3O+ and NO3- indicated the potential of this dielectric barrier discharge system in sustainable fertilizer production. In addition, the toxicity prediction of salicylic acid degradation intermediates and the cultivation of soybean seeds verified the feasibility of plasma-liquid interactions in organic wastewater recycling.

Plasma-enhanced microbial electrolytic disinfection: Decoupling electro- and plasma-chemistry in plasma-electrolyzed oxidizing water using ion-exchange membranes

Pathogenic microorganisms pose a global threat to public health and environment. Common antibacterial chemicals produce toxic residues, inevitably harming the environment. Electrolyzed oxidizing water (EOW), a promising environment-friendly alternative disinfectant, still lacks effective production processes, sufficient bactericidal efficacy and stability, while the enabling physico-chemical mechanisms remain unclear. Here, we report, for the first time, an effective hybrid plasma electrochemical EOW production process and reveal the mechanisms by combining nonthermal plasmas and a two-chamber electrochemical cell separated by a cation exchange membrane (CEM) for decoupling the chemical reactions during the plasma treatment of water. Experimental results demonstrate that combined chlorine (chloramine) was the main chlorine product in the plasma-enhanced EOW (P-EOW) without a membrane, owing to the consumption of free chlorine (Cl2, HOCl, ClO−) by plasma-generated reactive nitrogen species. With a CEM in the plasma electrolysis system and through controlling the plasma discharge polarity, the production of free chlorine and other reactive species can be selectively controlled, with the highest concentration of free chlorine obtained in the negative plasma-enhanced EOW (NP-EOW). According to the transportation of cations by the CEM, the high concentrations of free chlorine may be attributed to the higher consuptions of H+ in cathode cell of negative plasma. The study of antibacterial ability of EOW produced under different conditions revealed that Staphylococcus aureus cells were best inactivated by the NP-EOW with CEM, which is mainly attributed to the higher concentration of free chlorine. This study demonstrates the feasibility of plasma-enhanced microbial electrolytic disinfection and offers new insights into the fundamental aspects of P-EOW chemistries for the future development of sustainable, efficient, and cost-effective multipurpose sustainable chemical technologies for water research and treatment.