Search

Pesticides are widely used in commercial goji Lycium barbarum cultivation to prevent damage of the delicate fruits by insects, potentially leading to insecticide and fungicide residues at levels dangerous to human health. In this study, removal of organophosphorus pesticide (OP) residues (i.e. omethoate and dichlorvos) from the surface of L. barbarum was conducted using a gas phase surface discharge (GPSD) plasma system. ICCD and GC–MS measurements showed that a homogeneous and uniform GPSD glow-like plasma could be achieved and the efficiency of OP residues degradation greatly depended on the applied voltage and plasma exposure time, with 99.55% and 96.83% efficiency recorded for omethoate and dichlorvos (DDVP), respectively after 30 min GPSD plasma exposure at the discharge voltage of 10 kV. FT-IR and chemical analysis of the intermediates produced during GPSD exposure revealed that the omethoate and DDVP molecules could be completely degraded into nontoxic species, at the appropriate dosage of GPSD plasma exposure, without compromising the quality of L. barbarum . Based on the experimental and simulation results, a mechanism of OP degradation attributed to energetic electrons and highly reactive species generated by GPSD plasma was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Underwater plasma bubbles were used to degrade cefixime in water. • Complete cefixime degradation with high-energy yield of 1.5 g/kWh. • Degradation of cefixime was conducted by reactive species, especially short-lived OH radicals. • Degradation pathways of cefixime were proposed by intermediates identified by LCMS. • Plasma treatment leads to the loss of antibacterial activity and cytotoxicity of cefixime. Excessive use and indiscriminate discharge of antibiotics inevitably lead to their accumulation in the environment, posing significant ecological and physiological risks. Non-thermal plasma (NTP) is receiving increasing attention as a sustainable technology for the efficient breakdown of these antibiotics as well as other contaminants. However, implementation of NTP technology still faces several hurdles, particularly the maximization of the reactive plasma effects and the practical scaling approaches. In this study, we generated NTP inside forming bubbles with enlarged gas-liquid interfacial areas for efficient delivery of reactive plasma species to target cefixime antibiotic molecules in aqueous solution. The degradation of cefixime was largely dependent on the different number of microholes, air flow rate, discharge power, plasma exposure time and solution properties. Results show that a high-performance degradation was achieved in the 10-microhole reactor with an energy yield of 1.5 g/kWh, after 30 min of plasma treatment. Based on LC-MS analysis, an NTP-initiated cefixime degradation pathway was proposed. Cytotoxicity studies demonstrated that the antibiotic activity of cefixime was effectively and wholly deactivated by the plasma process, and that no toxic effects of the 30 min-treated water were observed toward human cell lines. Furthermore, considering that air was employed as the inducer gas, which results in the formation of reactive nitrogen species in the water, the treated water was able to enhance seedling growth, further contributing to the societal and economic benefits of this plasma-based antibiotic degradation strategy. [ABSTRACT FROM AUTHOR]

• The current state-of-the-art of plasma-enabled ammonia synthesis is summarized. • The fundamental physio-chemistry of plasma activation of feedstocks is provided. • The mechanisms for the reaction dynamics of reactive species are concluded. • Opportunities and challenges for the plasma-ammonia industry are outlined. Ammonia is one of our most important industrial chemicals supporting the global food supply as the major crop fertilizer. Moreover, it is increasingly being promoted as a promising carbon-free fuel source, and an energy storage and transportation medium. However, the current approach for ammonia synthesis, known as the Haber-Bosch process, requires large-scale infrastructure preventing the designs of decentralization. The process consumes a large fossil fuel input leading it to be a major source of CO 2 emissions. Plasma-enabled ammonia synthesis provides a clean, sustainable and flexible alternative, where the process is driven by the use of plasmas that activate the source gas(es). However, atmospheric plasmas are complex due to their highly reactive environment (energetic electrons, reactive oxygen and nitrogen species, UV photons, electric field effects, and others), resulting in a challenging scientific issue for both plasma researchers and chemical engineers. The review summarizes the current state-of-the-art of plasma-enabled ammonia synthesis, and provides insights into the fundamental physio-chemistry of plasma activation, including the excitation, dissociation and ionization of feedstocks, as well as the underlying mechanisms for the reaction dynamics of reactive species in the highly-reactive plasma environment. Finally, the opportunities and challenges for this plasma-enabled technology are outlined to approach a sustainable and flexible ammonia industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Underwater plasma bubbles were used to degrade cefixime in water. • Complete cefixime degradation with high-energy yield of 1.5 g/kWh. • Degradation of cefixime was conducted by reactive species, especially short-lived OH radicals. • Degradation pathways of cefixime were proposed by intermediates identified by LCMS. • Plasma treatment leads to the loss of antibacterial activity and cytotoxicity of cefixime. Excessive use and indiscriminate discharge of antibiotics inevitably lead to their accumulation in the environment, posing significant ecological and physiological risks. Non-thermal plasma (NTP) is receiving increasing attention as a sustainable technology for the efficient breakdown of these antibiotics as well as other contaminants. However, implementation of NTP technology still faces several hurdles, particularly the maximization of the reactive plasma effects and the practical scaling approaches. In this study, we generated NTP inside forming bubbles with enlarged gas-liquid interfacial areas for efficient delivery of reactive plasma species to target cefixime antibiotic molecules in aqueous solution. The degradation of cefixime was largely dependent on the different number of microholes, air flow rate, discharge power, plasma exposure time and solution properties. Results show that a high-performance degradation was achieved in the 10-microhole reactor with an energy yield of 1.5 g/kWh, after 30 min of plasma treatment. Based on LC-MS analysis, an NTP-initiated cefixime degradation pathway was proposed. Cytotoxicity studies demonstrated that the antibiotic activity of cefixime was effectively and wholly deactivated by the plasma process, and that no toxic effects of the 30 min-treated water were observed toward human cell lines. Furthermore, considering that air was employed as the inducer gas, which results in the formation of reactive nitrogen species in the water, the treated water was able to enhance seedling growth, further contributing to the societal and economic benefits of this plasma-based antibiotic degradation strategy. [ABSTRACT FROM AUTHOR]

• Underwater plasma bubbles facilitated mass transfer of highly reactive species. • Plasma catalytic bubbles using CeO 2 enhanced the AP removal efficiency. • Catalytic performance and durability of CeO 2 were improved by plasma activation. • Degradation mechanisms of AP were proposed by intermediates identified by LCMS. Interactions between effects generated by non-thermal plasma (NTP) and catalysts are increasingly investigated, ranging from energy conversion and material synthesis to pollutant degradation (e.g. volatile organic compounds, VOCs) and water purification. To make the water ecosystem more environmentally and economically sustainable, green and efficient wastewater treatment technologies are urgently required. In this study, a plasmacatalytic bubble column reactor was designed to generate underwater plasma bubbles (PBs) for efficient delivery of plasma-produced gaseous reactive oxidative species to the liquid phase for subsequent applications. This system shows great potential for degrading a stubborn water contaminant azophloxine (AP), which was further enhanced with an addition of CeO 2 catalysts, resulting in the catalytic oxidation of the azo dyes. Moreover, the performances and durability of CeO 2 were further improved via plasma pre-activation. The plasma-treated CeO 2 (CeO 2 -P) displayed a combination of favourable properties, such as a higher concentration of oxygen vacancies and Ce3+ (observed by XPS), a narrowed energy bandgap, and an increased specific surface area (by 41.39%). Compared with the sole PBs and PBs/CeO 2 systems, the highest removal efficiency and kinetic constant up to 99.5% and 0.907 min−1, respectively, were achieved in the PBs/CeO 2 -P system. Reactive species trapping corroborated that ·OH and ·O 2 – played an integral part in AP degradation. Finally, intermediates in the process of AP degradation were identified and a degradation pathway was proposed. This research would offer a promising remediation methodology for water purification via the integration of underwater plasma bubbles and CeO 2 catalysts. [ABSTRACT FROM AUTHOR]

• New approach for clean hydrogen energy and smart nano-carbons production. • Effective bioresource conversion using new pulsed plasma modes. • Catalyst-free, plasma conversion of ethanol at near-room temperature. • Towards full bioresource utilization: carbon for carbon, hydrogen for hydrogen. Selective conversion of bio-renewable ethanol under mild conditions especially at room temperature remains a major challenge for sustainable production of hydrogen and valuable carbon-based materials. In this study, adaptive non-thermal plasma is applied to deliver pulsed energy to rapidly and selectively reform ethanol in the absence of a catalyst. Importantly, the carbon atoms in ethanol that would otherwise be released into the environment in the form of CO or CO 2 are effectively captured in the form of carbon dots (CDs). Three modes of non-thermal spark plasma discharges, i.e. single spark mode (SSM), multiple spark mode (MSM) and gliding spark mode (GSM), provide additional flexibility in ethanol reforming by controlling the processes of energy transfer and distribution, thereby affecting the flow rate, gas content, and energy consumption in H 2 production. A favourable combination of low temperature (<40 °C), attractive conversion rate (gas flow rate of ~120 mL/min), high hydrogen yield (H 2 content >90%), low energy consumption (~0.96 kWh/m3 H 2) and the effective generation of photoluminescent CDs (which are applicable for bioimaging or biolabelling) in the MSM indicate that the proposed strategy may offer a new carbon-negative avenue for comprehensive utilization of alcohols and mitigating the increasingly severe energy and environmental issues. [ABSTRACT FROM AUTHOR]

[Display omitted] • A transient spark gas–liquid discharge combined with TiO 2 was employed for the degradation of tetracycline in water. • A degradation rate of 90.2% was achieved by plamsa-TiO 2 system for 10 min treatment. • The catalyst TiO 2 exhibits a high efficiency at a lower pulse voltage. • Possible pathways of tetracycline degradation were deduced based on the analysis of intermediate by LC/MS. • The treated solution was proved to be harmless for the seed germination and plant growth. Water pollution driven by the increasing antibiotic abuse leads to serious ecological impacts and risks to human health. Non-thermal plasma, a sustainable advanced oxidation process, is considered as a promising approach for antibiotic degradation. In this study, a transient spark gas–liquid discharge was developed for the degradation of tetracycline in water and coupled with a photocatalyst (TiO 2) to further improve the degradation efficiency. Results show that the discharge was accompanied by intense UV light of up to 28 μW/cm2. The tetracycline degradation performance was strongly dependent on the pulse voltage, working gas, initial concentrations of tetracycline and the catalyst addition. The best degradation performance was achieved in the plasma-TiO 2 system with a degradation rate of 90.2% after 10 min treatment. The catalyst exhibits a high efficiency at lower pulse voltages, with the synergetic intensity of plasma and TiO 2 showing a decreasing trend with increasing pulse voltage. Radical quenching experiments suggest that hydroxyl radical (∙OH) plays a key role in the tetracycline degradation process. A pathway for tetracycline degradation by the plasma-TiO 2 process is deduced according to the analysis of the degradation intermediates. Further, seed germination and plant growth tests for the treated water demonstrated the feasibility of discharging the treated water to irrigate agricultural crops. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fix N 2 as aqueous nitrates and nitrites from air plasma with underwater bubbles. • Enhance nitrogen oxidation catalytic activity by a structured TiO 2 catalyst. • Gaseous NO x surface adsorption and reactions from catalyst characterizations. • Critical intermediate species and chemical pathways from plasma chemical modelling. Current industrial nitrogen fixation technology is unsustainable and has adverse environmental effects due to its reliance on fossil fuels. Using electricity-driven non-thermal plasma catalysis to fix nitrogen into NO 3 − is a promising solution, but the underlying mechanisms remain largely unknown. This study integrates a structured catalyst into a plasma column with a water-electrode bubble reactor that can fix nitrogen at ambient pressure and temperature with a 93% selectivity to NO 3 − with excellent catalytic stability. Characterizations of the catalyst and in situ plasma diagnostics indicate that the enhanced production of nitrate ions is due to abundant chemisorbed oxidized nitrogens species originating from NO and NO 2 produced by the air plasma. The plasma chemistry model combined with DFT simulations demonstrates the role of structured TiO 2 supported by 5% graphene oxide (GO) to improve NO x surface association while minimizing NO x backwards dissociation. The modelling results suggest the critical role of NO 3(ad) in enhancing NO x production predominantly in the form of N 2 O 5 molecule in the gas phase, resulting in efficient NO 3 − (aq) production as a final product in water. The study offers novel findings on plasma-catalyzed nitrogen fixation, advancing its potential for clean energy and eco-friendly chemical production through plasma-based power-to-chemical processes. [ABSTRACT FROM AUTHOR]

• A novel photocatalysis-self-Fenton system based on violet phosphorus (VP)-Fe 3 O 4 is constructed. • VP-Fe 3 O 4 coupled with underwater bubble plasma (UBP) can effectively improve the degradation efficiency of norfloxacin in water. • The excellent reducibility and electron donating ability of VP accelerate the cycle of Fe(II)/Fe(III) in Fenton reactions. • VP-Fe 3 O 4 has better synergistic degradation ability with UBP than the reduced graphene oxide-Fe 3 O 4. • The efficient utilization of H 2 O 2 in-situ produced by UBP achieves the sustainable generation of •OH after post-discharge. The contamination of water bodies has been caused by the overuse of antibiotics to an alarming extent. Green and enhanced treatment technologies for wastewater are necessary to limit the uncontrollable spread of antibiotic pollution. Herein, an efficient photocatalysis-self-Fenton system based on violet phosphorus (VP)-Fe 3 O 4 is constructed to achieve significant degradation performance. The VP-Fe 3 O 4 combined with underwater bubble plasma (UBP) has been demonstrated to obtain a norfloxacin (NOR) degradation rate as high as 91.8% with the VP content of 15 wt%, which is 77.3% and 22.2% higher than that in sole VP-Fe 3 O 4 and UBP, respectively. The •OH radicals have been demonstrated by the radical trapping test to play a crucial role in NOR removal processes. The VP-Fe 3 O 4 has also been found to have a higher synergistic degradation ability with UBP than the well-known reduced graphene oxide-Fe 3 O 4 , which is due to the excellent reducibility and electron donating ability of VP, boosting the cycle of Fe(II)/Fe(III) in Fenton reactions. The VP-Fe 3 O 4 can also consume O 3 generated by UBP, with the enhanced in-situ H 2 O 2 production. Besides, the efficient utilization of H 2 O 2 via the Fenton reaction improves the generation of •OH. A clear signal of DMPO-OH has been detected by electron spin resonance after 24 h post-discharge, further substantiating the sustainable regeneration of •OH by the synergetic system in the absence of additional reagents. Three possible degradation pathways are proposed based on the density functional theory (DFT) calculation and the degradation by-products of NOR determined during the synergetic treatment. Eventually, the synergetic degradation mechanism in the VP-Fe 3 O 4 /UBP system is elucidated. This research would provide a promising strategy for environmental remediation via the incorporation of photocatalysis-self-Fenton system and underwater bubble plasma. [ABSTRACT FROM AUTHOR]

• HDP reactor formed plasma discharges in both electrodes with a single power source. • PAW was generated with high energy efficiency and a very fast inactivation rate. • Decreasing the orifice diameter of the HPD reactor increased the energy efficiency. • Increasing salinity enhanced the energy efficiency to 0.181 mol·kW−1·h−1. • 5.18-log 10 reduction of Escherichia coli inactivation was achieved in 30 s. Plasma-activated water (PAW), an emerging and cost-effective disinfectant produced from the interaction between non-thermal plasma and water, was generated with a newly designed hybrid plasma discharge (HPD) reactor. The HPD reactor produces two simultaneous plasma discharges within one power source, one from the high-voltage electrode above the liquid surface, and the other from the ground electrode enclosed in a quartz tube, allowing the air to flow through the side of the ground electrode and injecting plasma bubbles into the liquid. The simulated distributions of electric field indicated that high electric fields were induced around both the high voltage and ground electrodes, at high input voltages, explaining the plasma discharges observed on both electrodes. The PAW generated via the HPD reactor achieved a high RONS energy efficiency of 1.81 × 10-1 mol·kW−1·h−1 and a high inactivation against Escherichia coli of 5.18-log 10 reduction in 30 s of contact time, outperforming reported literature studies, which require minutes or hours to achieve similar inactivation. The effect of the number and size of orifices in the bubble column of the HPD reactor was studied, as well as the effect of the liquid volume (from 0.5 to 2 L), and salinity (from 0 to 8 mM NaCl). The Escherichia coli in PAW was further analysed by TEM and DNA leakage showing that PAW damaged the cell membrane. This hybrid plasma discharge reactor can be the base of producing disinfectant PAW in larger volume for the agriculture, biomedical, food and water treatment industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • New approach for surface crack repair and insulation recovery of silicone rubber composites. • Plasma-electrified repair based on dissociation and re-assembly of alkoxysilane. • Better mechanical and electrical properties of composites after plasma repair. • More effective, sustainable and low-carbon compared to common repair methods. Polymer composites, widely used in aerospace and electrical power systems, are inevitably aged by environmental stress causing cracks on the material's surface, which weakens their mechanical and electrical properties. Addressing the issue requires significant effort and the use of hazardous chemicals. In this study, a novel plasma-electrified repair method based on the Ar/H 2 O/alkoxysilane (PMDMS) low temperature plasma is developed for the surface crack healing and insulation recovery of silicone rubber (SIR) composites. It is demonstrated that the plasma-enabled polymerization effectively repairs the cracked SIR, with a new fin-like insulating layer deposited on the crack surface. The mechanical and electrical properties of the cracked SIR are improved after the plasma repair, with the result clearly better than using the conventional coating method. Hydrolysis-condensation of PMDMS by plasma-enabled dissociation and re-assembly, surface activation of the crack by plasma modification and grafting-crosslinking in the crack account for the multiphase chemical reactions induced within the crack. Further analysis based on quantum chemistry calculations reveals that the plasma treatment both promotes the chemical reactivity of the SIR surface and reconstructs a dense repair phase in the crack with a wide forbidden gap and shallow taps, further confirming this effective crack healing process which improves the mechanical and electrical performances of the damaged SIR. Overall, this newly-developed plasma-electrified repair method for damaged SIR eliminates the environmental pollution caused by large scale and overused chemical coatings, and offers new possibilities for sustainable and low-carbon-emission material engineering for processing and restoration of composite materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • New approach for biofuel production and resource recovery from human waste. • Rapid conversion of human feces to clean chemicals by plasma-electrolyic liquefaction. • Bio-crude oil contains value-added chemicals with oxygen-rich functional groups. • Sustainable recovery of ammonium, chlorine and metals from human waste. • Cleaner, energy-efficient compared to common liquefaction methods. Sustainable production of value-added fuels and chemicals from biomass faces enormous challenges for integration in zero-carbon-emissions technologies and circular economy. In this work, green and renewable solvents, polyethylene glycol 200 and glycerol, were used in a plasma-electrolytic liquefaction (PEL) system to electrically liquefy human feces in the absence of a catalyst. It is demonstrated that the plasma ignition during the liquefaction accelerated the conversion of feces (85.67% liquefaction yield within 12 min), and the intrinsic heating features of the PEL greatly reduced the energy consumption. The obtained biocrude oil at the optimized conditions contained 10.53% aldehydes, 5.39% ketones, 18.48% cyclic oxygen-containing compounds and others, with a high heating value of 28.10 MJ/kg. Further analysis of the PEL-converted products reveals that most of the chlorine in the feces was gasified, the metals were extracted into the solid residue, while ammonia was released. An evaluation of the developed plasma electrolytic feces liquefaction process was carried out and favorably compared with common liquefaction methods. Overall, the proposed approach may provide a new avenue for clean chemical production and sustainable resource recovery from human waste under benign process conditions. [ABSTRACT FROM AUTHOR]