Reactive Species Research Articles

Cold atmospheric plasma-activated medium for potential ovarian cancer therapy.

Cold atmospheric plasma (CAP) has emerged as an innovative tool with broad medical applications, including ovarian cancer (OC) treatment. By bringing CAP in close proximity to liquids such as water or cell culture media, solutions containing reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated, called plasma-activated media (PAM). In this systematic review, we conduct an in-depth analysis of studies focusing on PAM interactions with biological substrates. We elucidate the diverse mechanisms involved in the activation of different media and the complex network of chemical reactions underlying the generation and consumption of the prominent reactive species. Furthermore, we highlight the promises of PAM in advancing biomedical applications, such as its stability for extended periods under appropriate storage conditions. We also examine the application of PAM as an anti-cancer and anti-metastatic treatment for OC, with a particular emphasis on its ability to induce apoptosis via distinct signaling pathways, inhibit cell growth, suppress cell motility, and enhance the therapeutic effects of chemotherapy. Finally, the future outlook of PAM therapy in biomedical applications is speculated, with emphasis on the safety issues relevant to clinical translation.

Gas phase formaldehyde degradation: Continuous versus duty cycle driven plasma reactor

This study investigated the degradation of formaldehyde (HCHO) using continuous plasma reactor (CPR) and duty cycle driven plasma reactor (DCPR) to obtain insights into reactor selection, optimization strategies, and underlying kinetics. The electrical characteristics of the reactors were analyzed via current-voltage analysis while optical properties were investigated using optical emission spectroscopy (OES). Furthermore, the reactive species concentrations were determined using gas Fourier-transform infrared (FTIR) measurements. The optimization of the degradation focused on varying the applied voltages, resulting in intensified plasma and changes in the surface temperature, electron temperature rotational temperature, and vibrational temperature. CPR demonstrated outstanding efficiency, with an energy yield of 3.60 g kW−1 h−1 and an impressive 89 % removal effectiveness at 5.8 kV. The best removal efficiency of 92 % was observed at 6.2 kV. The degradation kinetics were primarily driven by energetic electrons, along with primary reactive species such as OH ⋅ and O ⋅ with a reaction rate of 6.8 × 10−3 L J−1. This study contributes to advancing the understanding of HCHO degradation kinetics and provides practical insights into enhancing plasma-based environmental cleanup technologies without using any catalyst.

Magnéli Ti4O7 nanowire induces locally enhanced electric field and electrocatalytic activity for rapid and efficient water disinfection via synergistic electroporation and electrochlorination

Waterborne pathogens in drinking water remains a prominent cause of morbidity and mortality in developing rural areas. Electrochlorination offers a promising alternative for decentralized water disinfection, but its efficiency was strongly restrained by the low Cl- concentrations in natural waters. Herein, we proposed a Magnéli Ti4O7 nanowire-assisted electrochemical approach via forming locally enhanced electric field over nanowire tips for reinforcing electroporation, and via forming locally enhanced charge density for promoting Cl- enrichment and subsequent electrochlorination on anodic nanowire tips. Ti4O7 nanowires induced the enhancement of electric field by 4 orders of magnitude and Cl- concentration by ∼3 orders of magnitude at nanowire tips, and promoted ∼3 times more active chlorine generation at a voltage of 3.0 V compared with non-nanostructured one. Synergistic electroporation and electrochlorination on nanowires enabled rapid and efficient disinfection with hydraulic retention time of ∼36 s and energy consumption below ∼5 J/L/log for inactivation of various gram-positive/negative bacteria and phage MS2. Analyses of cell morphology and membrane integrity revealed that electroporation-induced cell pores provided diffusion channels of reactive chlorine species for oxidative damage of cell structures, resulting in ∼1.5–4.5 times lower energy consumption than the thin-film, nanoparticle, and nanorod ones. The excellent operation stability for tap water with significant bacterial inactivation and active chlorine generation demonstrated its great application potential for decentralized water disinfection.

Revisited Synthesis of Trispyrazolylborate Aluminum Halides Suban Kundu, Raju Chambenahalli, Alex P. Andrews and Ajay Venugopal*

Tris(3,5‐dimethylpyrazolyl)borate aluminum dihalides TpMe2AlX2 (X=Cl, Br and I) can be potential precursors for preparing highly electrophilic dications as well as low oxidation state aluminum compounds. However, the coordinative unsaturation in TpMe2AlX2 makes them susceptible to rearrangement to [Tp2Al][AlX4]. In this work, we revisited the synthesis of TpMe2AlX2 by isolating the solvent‐stabilized tris(3,5‐dimethylpyrazolyl)borate aluminum dihalides TpMe2AlX2(L) (X=Cl, Br; L = THF, HPMA). Efforts to isolate TpMe2All2 resulted in the ring opening of THF revealing the mediation of a highly reactive cationic aluminum species. The monocationic, [TpMe2AlCl(THF)2][B{C6H3(CF3)2}4] was prepared from TpMe2AlCl2(THF) via silver salt metathesis. Attempts to prepare the dicationic species [TpMe2Al(THF)3]2+ resulted in the instantaneous ring‐opening polymerization of THF.

Water mediated redox-neutral cleavage of arylalkenes via photoredox catalysis

Cleavage of carbon-carbon bonds remains a challenging task in organic synthesis. Traditional methods for splitting Csp2=Csp2 bonds into two halves typically involve non-redox (metathesis) or oxidative (ozonolysis) mechanisms, limiting their synthetic potential. Disproportionative deconstruction of alkenes, which yields one reduced and one oxidized fragment, remains an unexplored area. In this study, we introduce a redox-neutral approach for deleting a Csp2 carbon unit from substituted arylalkenes, resulting in the formation of an arene (reduction) and a carbonyl product (oxidation). This transformation is believed to proceed through a mechanistic sequence involving visible-light-promoted anti-Markovnikov hydration, followed by photoredox cleavage of Csp3-Csp3 bond in the alcohol intermediate. A crucial consideration in this design is addressing the compatibility between the highly reactive oxy radical species in the latter step and the required hydrogen-atom-transfer (HAT) reagent for both steps. We found that ethyl thioglycolate serves as the optimal hydrogen-atom shuttle, offering remarkable chemoselectivity among multiple potential HAT events in this transformation. By using D2O, we successfully prepared dideuteromethylated (-CD2H) arenes with good heavy atom enrichment. This work presents a redox-neutral alternative for alkene deconstruction, with considerable potential in late-stage modification of complex molecules.

Efficient Photocatalytic Degradation of Triclosan and Methylene Blue by Synthesized Ag-Loaded ZnO under UV Light

Industrial discharge of hazardous organic and synthetic chemicals, such as antibacterials and dyes, poses severe risks to human health and the environment. This study was conducted to address the urgent need for efficient and stable zinc-oxide-based photocatalysts to degrade such pollutants. A novel approach to synthesizing silver-loaded zinc oxide (Ag@Z) catalysts was introduced by using a simple and efficient combination of hydrothermal and precipitation methods. Comprehensive characterization of Ag@Z photocatalysts was performed using XRD, XPS, Raman, UV–vis adsorption, FTIR, and SEM, revealing an enhancement of structural, optical, and morphological properties in comparison to pure zinc oxide. Notably, the 5%Ag@Z catalyst exhibited the highest degradation efficiency among the other synthesized catalysts under UV-C light irradiation, and enhanced the degradation rate of pure zinc oxide (Z) by 1.14 and 1.64 times, for Triclosan (TCS) and Methylene Blue (MB), respectively. the effect of catalyst dose and initial concentration was studied. A mechanism of degradation was proposed after investigating the effect of major reactive species. The 5%Ag@Z catalyst increased the photostability, which is a major problem of zinc oxide due to photocorrosion after reusability. We found that 50% and 74% of energy consumption for the photocatalytic degradation of TCS and MB by 5%Ag@Z, respectively, was saved in compassion with zinc oxide. The remarkable photocatalytic performance and the good recovery rate of Ag@Z photocatalysts demonstrate their high potential for photocatalytic degradation of organic contaminants in water.

Effect of dielectric material on the uniformity of nanosecond pulsed dielectric barrier discharge

Dielectric barrier discharge (DBD) is considered as a promising technique to produce large volume uniform plasma at atmospheric pressure, and the dielectric barrier layer between the electrodes plays a key role in the DBD processes and enhancing discharge uniformity. In this work, the uniformity and discharge characteristics of the nanosecond (ns) pulsed DBD with dielectric barrier layers made of alumina, quartz glass, polycarbonate (PC), and polypropylene (PP) are investigated via discharge image observation, voltage-current waveform measurement and optical emission spectral diagnosis. Through analyzing discharge image by gray value standard deviation method, the discharge uniformity is quantitatively calculated. The effects of the space electric field intensity, the electron density (N e), and the space reactive species on the uniformity are studied with quantifying the gap voltage U g and the discharge current I g, analyzing the recorded optical emission spectra, and simulating the temporal distribution of N e with a one-dimensional fluid model. It is found that as the relative permittivity of the dielectric materials increases, the space electric field intensity is enhanced, which results in a higher N e and electron temperature (T e). Therefore, an appropriate value of space electric field intensity can promote electron avalanches, resulting in uniform and stable plasma by the merging of electron avalanches. However, an excessive value of space electric field intensity leads to the aggregation of space charges and the distortion of the space electric field, which reduce the discharge uniformity. The surface roughness and the surface charge decay are measured to explain the influences of the surface properties and the second electron emission on the discharge uniformity. The results in this work give a comprehensive understanding of the effect of the dielectric materials on the DBD uniformity, and contribute to the selection of dielectric materials for DBD reactor and the realization of atmospheric pressure uniform, stable, and reactive plasma sources.

Physical and chemical characteristics of plasma-activated water generated by hybrid dielectric barrier discharge and gliding arc discharge

This research explores the synergistic application of Dielectric Barrier Discharge (DBD) and Gliding Arc Plasma Jet (GAPJ) in a Hybrid Plasma Discharge (HPD) setup for enhanced water activation. The HPD system demonstrated balanced and sustained generation of reactive oxygen and nitrogen species (RONS), maintaining efficiency at higher specific input energy (SIE) values. Comparative analyses with DBD and GAPJ systems highlighted the superior performance of the HPD system in generating RONS and modifying water’s molecular structure. Key observations included a decrease in water’s pH and an increase in oxidation-reduction potential, total dissolved solids, and conductivity, stabilizing beyond 5 l min−1 airflow and 10 min of treatment. UV−Vis spectroscopy identified nitrites, nitrates, hydrogen peroxide, and nitrous acid, while Raman spectroscopy captured shifts in vibrational modes, particularly in librational and O–H stretching bands. These changes correlated with alterations in reactive species concentrations and pH levels. Overall, the HPD system emerged as a versatile and efficient approach for generating plasma-activated water, suitable for applications in microbial deactivation, surface sterilization, and electrocatalytic process optimization, offering stable and continuous production of reactive species across a range of SIE values.

Hourly effect of atmospheric reactive nitrogen species on the onset of acute ischemic stroke: Insight from the Shanghai Stroke Service System Database

Acute ischemic stroke (AIS) is one of the most predominant causes of mortality and disability in China. Significant uncertainties in stroke diagnosis and time of onset have resulted in inconsistent evidence on the association between ambient air pollution and the risk of AIS. The present study aimed to evaluate the impact of air pollution on AIS onset based on high time-resolution air pollution data and a stroke-specific registry across the past five years. Hourly concentrations of PM2.5, PM10, O3, SO2, CO, NO2 and nitrous acid (HONO) were monitored from 2017 to 2021, with which a distributed lag non-linear model and conditional logistic regression models coupled with a time-stratified case-crossover design were applied to 106,623 AIS cases recorded in the Shanghai Stroke Service (4S) database during the study period. Results from the conditional logistic regression models indicate that acute exposure to PM2.5, PM10, SO2, NO2 and HONO was found to be associated with AIS onset, respectively. The corresponding cumulative excessive risks of AIS onset were 0.8 %, 1 %, 2.4 %, 2.1 % and 1.8 % for each interquartile range increase in the respective concentration. The longest lag-effect (up to 13 h) was observed for reactive nitrogen species (RNS), such as NO2 and HONO, which remained robust in two-pollutant models. Similar important role of RNS in AIS onset were confirmed by the distributed lag non-linear model. By demonstrating the transient effect of ambient air pollution on AIS, especially the relationships between RNS and AIS for the first time, our study provides stringent evidence for future mitigation strategies for pollution emission and public health.

Synthesis and Electrophilic Trifluoromethylthiolation Properties of 1-Methyl-4-(trifluoromethylthio)piperazine (MTTP).

A cyclic diamine, 1-methyl-4-(trifluoromethylthio)piperazine (MTTP, 1), prepared by a one-step reaction from commercial materials, is a shelf-stable and powerful electrophilic trifluoromethylthiolating (CF3S) reagent with wide reactivity profile. Activation of 1 with triflic acid (TfOH) yields two reactive species A and B, depending on the molar ratios of TfOH/1. B showed unprecedented high reactivity, making possible the trifluoromethylthiolation of electron-deficient aromatic systems. In addition, B accomplished the trifluoromethylthiolation of active methylene compounds under acidic conditions.

Calculations for preemptive surface adsorbate drive-off to minimize plasma formation during operation of high-power microwave sources

Thermal driven desorption of surface impurities is probed based on coupled Monte Carlo–heat flow–molecular dynamics simulations. Such adsorbates can lead to plasma formation during the operation of high-power microwave systems with various negative outcomes and so need to be curtailed. Our study attempts to obtain temperature thresholds for desorbing different surface contaminants such as C2, O2, CO, and CO2. The results show that carbon-based adsorbates on copper (chosen as an example anode material) could be ejected at a relatively modest surface temperature of 650 K. On the other hand, reactive species such as oxygen are very stable due to their large cohesive energies. Our calculations further suggest the benefit of using a platinum coating layer, as the noble metal is robust with strong resistance to oxidation.

Structure-Activity Relationship of Benzophenazine Derivatives for Homogeneous and Heterogenized Photooxygenation Catalysis.

Singlet oxygen is a powerful oxidant used in various applications, such as organic synthesis, medicine, and environmental remediation. Organic and inorganic photosensitizers are commonly used to generate this reactive species through energy transfer with the triplet ground state of oxygen. We describe here a series of novel benzophenazine derivatives as a promising class of photosensitizers for singlet oxygen photosensitization. In this study, we investigated the structure-activity relationship of these benzophenazine derivatives. Akin to a molecular compass, the southern fragment was first functionalized with either aromatic tertiary amines, alkyl tertiary amines, aromatic sulfur groups, alkyl sulfur groups, or cyclic ethers. Enhanced photophysical properties (in terms of triplet excited-state lifetime, absorption wavelength, triplet state energy, and O2 quenching capabilities) were obtained with cyclic ether and sulfur groups. Conversely, the presence of an amine moiety was detrimental to the photocatalysts. The western and northern fragments were also investigated and slightly undesirable to negligible changes in photophysical properties were observed. The most promising candidate was then immobilized on silica nanoparticles and its photoactivity was evaluated in the citronellol photooxidation reaction. A high NMR yield of 97 % in desired product was obtained, with only a slight decrease over several recycling runs (85 % in the fourth run). These results provide insights into the design of efficient photosensitizers for singlet oxygen generation and the development of heterogeneous systems.

Electrocatalytically active and charged natural chalcopyrite for nitrate-contaminated wastewater purification extended to energy storage Zn-NO3− battery

Charged natural chalcopyrite (CuFeS2, Ncpy) was developed for a three-dimensional electrochemical nitrate reduction (3D ENO3−RR) system with carbon fiber cloth cathode and Ti/IrO2 anode and Zn-NO3− battery. The 3D ENO3−RR system with Ncpy particle electrodes (PEs) possessed superior nitrate removal of 95.6 % and N2 selectivity of 76 % with excellent reusability under a broad pH range of 2–13 involving heterogeneous and homogeneous radical mechanisms. The Zn-NO3− battery with Ncpy cathode delivered an open-circuit voltage of 1.03 V and a cycling stability over 210 h. It was found that Ncpy PEs functioned through self-oxidation, surface dynamic reconstruction (Cu1.02Fe1.0S1.72O1.66 to Cu0.61Fe1.0S0.27O2.98), intrinsic micro-electric field (CuI, S2− anodic and FeIII cathodic poles), and reactive species (•OH, SO4•−, 1O2, •O2− and •H) generation. Computational analyses reveal that CuFeS2(112) surface with the lowest surface energy preferentially exposes Fe and Cu atoms. Cu site is beneficial for reducing NO3− to NO2−, Fe and Fe−Cu dual sites are conducive to N2 selectivity, lowering the overall reaction barriers. It paves the way for selective NO3− reduction in wastewater treatment and can be further extended to energy storage devices by utilizing low-cost Ncpy.

Autocatalytic degradation of Cu-EDTA in the Calcite/PMS system: Singlet oxygen and Cu(III)

The simultaneous removal of heavy metal complexes (HMCs) and heavy metal ions presents a significant challenge in treating wastewater. To address this, we propose a Calcite/Peroxymonosulfate (Calcite/PMS) system aimed at simultaneously decomplexing Cu-EDTA and removing Cu ions. Calcite/PMS system could achieve 99.5 % Cu-EDTA decomplexation and 61.9 % Cu ions removal within 60 min under initial conditions of Cu-EDTA (10 mg/L), Calcite (3 g/L), and PMS (2 mM). Singlet oxygen (1O2) emerged as the predominant reactive species responsible for Cu-EDTA decomplexation, which selectively targeted the N-C bonds in the Cu-EDTA structure to produce intermediates with lower biotoxicity than EDTA. Interestingly, solid phase Cu(III) (≡Cu(III)) promoted the generation of superoxide radicals (O2•−) with a contribution of up to 72.8 %. Subsequently, nascent ≡Cu(III) and O2•− accelerated the degradation of intermediates. Besides, coexisting organic substances inhibited Cu-EDTA decomplexation, whereas inorganic ions had a weak impact. After five cycles of use, the Calcite/PMS system retained 99.3 % efficiency in decomplexing Cu-EDTA. This investigation provides valuable insights into using calcite to remove HMCs and enhances our comprehension of the decomplexation intermediates accelerating HMCs degradation.

High-efficient M-NC single-atom catalysts for catalytic ozonation in water purification: Performance and mechanisms

Heterogeneous catalytic ozonation (HCO) holds promise in water purification but suffers from limited accessible metal sites, metal leaching, and unclear structure-activity relationships. This work reported M-NC (M=Co, Ni, Fe, and Mn) single-atom catalysts (SACs) with high atomic efficiency and minimal metal release. The new HCO systems, especially the Co-based system, exhibited impressive performance in various refractory contaminant removal, involving various reactive species generation, such as •OHads, •OHfree, *O, and 1O2. For sulfamethoxazole removal, the normalized kobs for Co-NC, Ni-NC, Fe-NC, and Mn-NC were determined as 13.53, 3.94, 3.55, and 4.13 min−1·mMmetal−1·g·m−2 correspondingly, attributed to the abundant acid sites, faster electron transfer, and lower energy required for O3 decomposition and conversion. The metal atoms and hydroxyl groups, individually serving as Lewis and Bronsted acid sites (LAS and BAS), were the primary centers for •OH generation and O3 adsorption. The relationships between active sites and both O3 utilization and •OH generation were found. LAS and BAS were responsible for O3 adsorption, while strong LAS facilitated O3 conversion into •OH. Theoretical calculations revealed the catalytic mechanisms involved O3→ *O→ *OO→ O3•−→ •OH. This work highlights the significance of SAC design for HCO and advances the understanding of atomic-level HCO behavior.

Strong enhancement on acetaminophen elimination and effective control of chlorinated/brominated by-products generation in heat/peroxymonosulfate system with sodium perborate

The application of heat/peroxymonosulfate (PMS) system was severely constrained due to the high O–O bond dissociation energy of PMS and the high risk of forming halogenated by-products. Interestingly, this work found that sodium perborate (NaBO3) could significantly improve the removal of acetaminophen in heat/PMS system. The proposed NaBO3/heat/PMS system could achieve 100 % elimination efficiency of ACT within 15 min and exhibited an excellent pseudo-first-order rate constant (kobs), which was 35.6-folds higher than heat/PMS system. 1O2 and OH were identified as the primary reactive species in NaBO3/heat/PMS system. NaBO3 can hydrolyze to produce BO2− and H2O2, where BO2− can subsequently hydrolyze to generate B(OH)4− having strong buffer capacity. The HOOB(OH)3/HOOBO, characterized by their asymmetric O–O bonds, can be formed through the reaction of PMS with BO2− and B(OH)4−. 1O2 mainly originated from the reactions of PMS with the formed HOOB(OH)3/HOOBO, and OH primarily originated from the cleavage of O–O bond in HOOB(OH)3/HOOBO and PMS. Three removal pathways of acetaminophen were proposed. The toxicity of acetaminophen solution was reduced following the treatment using NaBO3/heat/PMS system. Humic acid, CO32−, Br− and Cl− suppressed the acetaminophen removal in NaBO3/heat/PMS system, while initial pH, NO3− and SO42− had minimal impact. Notably, the kobs of acetaminophen removal in actual waters (e.g., groundwater and lake water) were greater than that in ultrapure water. More importantly, NaBO3/heat/PMS system can effectively control the formation of chlorinated/bromine by-products, which was achieved by converting HClO to inert B(OH)3OCl− with B(OH)4−, and reducing the HBrO and HClO to Br– and Cl– with deprotonated H2O2 (HO2−). This study proposed a promising approach for improving heat/PMS system and underscored its application potential in treating water containing Cl−and Br−.

ZnFe layered double hydroxide wrapped metal-organic framework derived cobalt-nitrogen-doped carbon material as peroxymonosulfate activator for ciprofloxacin degradation

ZnFe layered double hydroxide (ZnFe-LDH) wrapped metal–organic framework derived cobalt and nitrogen-doped carbon-based materials (ZnFe-LDH@CoNC) were synthesized. The fabricated nanocomposites exhibited uniform distribution of ZnFe-LDH-3 on CoNC matrix. Degradation efficiency of ciprofloxacin (CIP, 10 mg/L) in the peroxymonosulfate (PMS)-containing catalytic system reached up to 98.5 % at a dosage of 0.2 g/L ZnFe-LDH-3@CoNC and 0.4 g/L PMS at a reaction time of 30 min at 25 °C. The ZnFe-LDH-3@CoNC/PMS catalytic system was found to act as a pH buffer and it exhibited more stable activity in cyclic tests compared with the CoNC/PMS catalytic system. Quenching experiments and EPR analyses showed that 1O2 was the primary reactive species in the ZnFe-LDH-3@CoNC/PMS catalytic system. Degradation intermediate products of CIP were identified and a potential degradation mechanism was suggested. The ZnFe layered double hydroxide wrapped metal–organic framework advances methods in environmental catalyst design and simultaneously improves active metal for PMS activation.

Efficacy, kinetics, inactivation mechanism and application of cold plasma in inactivating Alicyclobacillus acidoterrestris spores

As spores of Alicyclobacillus acidoterrestris can survive traditional pasteurization, this organism has been suggested as a target bacterium in the fruit juice industry. This study aimed to investigate the inactivation effect of cold plasma on A. acidoterrestris spores and the mechanism behind the inactivation. The inactivation effect was detected by the plate count method and described by kinetic models. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), the detection of dipicolinic acid (DPA) release and heat resistance detection, the detection and scavenging experiment of reactive species, and cryo-scanning electron microscopy were used to explore the mechanism of cold plasma inactivation of A. acidoterrestris. The results showed that cold plasma can effectively inactivate A. acidoterrestris spores in saline with a 3.0 ± 0.3 and 4.4 ± 0.8 log reduction in CFU/mL, for 9 and 18 min, respectively. The higher the voltage and the longer the treatment time, the stronger the overall inactivation effect. However, a lower gas flow rate may increase the probability of spore contact with reactive species, resulting in better inactivation results. The biphasic model fits the survival curves better than the Weibull model. SEM and TEM revealed that cold plasma treatment can cause varying degrees of damage to the morphology and structure of A. acidoterrestris spores, with at least 50 % sustaining severe morphological and structural damage. The DPA release and heat resistance detection showed that A. acidoterrestris spores did not germinate but died directly during the cold plasma treatment. 1O2 plays the most important role in the inactivation, while O3, H2O2 and NO3− may also be responsible for inactivation. Cold plasma treatment for 1 min reduced A. acidoterrestris spores in apple juice by 0.4 ± 0.0 log, comparable to a 12-min heat treatment at 95 °C. However, as the treatment time increased, the survival curve exhibited a significant tailing phenomenon, which was most likely caused by the various compounds in apple juice that can react with reactive species and exert a physical shielding effect on spores. Higher input power and higher gas flow rate resulted in more complete inactivation of A. acidoterrestris spores in apple juice. What's more, the high inactivation efficiency in saline indicates the cold plasma device provides a promising alternative for controlling A. acidoterrestris spores during apple washing. Overall, our study provides adequate data support and a theoretical basis for using cold plasma to inactivate A. acidoterrestris spores in the food industry.

Chloride-mediated enhancement in Cu(II)-catalyzed Fenton-like reaction: The overlooked reactive chlorine species

The practical application of Cu(II)-catalyzed Fenton-like reaction (Cu(II)/H2O2) exhibits a low efficiency in the degradation of refractory compounds of wastewater. The impact of chloride ions (Cl−) on Fenton-like reactions have been investigated, but the influence mechanism is still unclear. Herein, the presence of Cl− (5 mM) significantly accelerated the degradation of benzoic acid (BA) under neutral conditions. The degradation of BA follows pseudo-first-order kinetics, with a degradation rate 7.3 times higher than the Cu(II)/H2O2 system. Multiple evidences strongly demonstrated that this reaction enables the production of reactive chlorine species (RCS) rather than HO• and high-valent copper (Cu(III)). The kinetic model revealed that Cl− could shift reactive species from the key intermediate (Cu(III)-chloro complexes) to RCS. Dichlorine radicals (Cl2•-) was discovered to play a crucial role in BA degradation, which was largely overlooked in previous reports. Although the reaction rate of Cl2•- with BA (k = 2.0 × 106 M−1 s−1) is lower than that of other species, its concentration is 10 orders of magnitude higher than that of Cu(III) and HO•. Furthermore, the exceptional efficacy of the Cu(II)/H2O2 system in BA degradation was observed in saline aquatic environments. This work sheds light on the previously unrecognized role of the metal-chloro complexes in production the RCS and water purification.

Anchoring N and Co species on the aluminum-graphite surface to enhance oxygen activation for the degradation of tetracycline at neutral conditions

Molecular oxygen (O2) activation for reactive species (RSs) production has recently received increasing interest. Reported herein is a novel O2 activator (Al-Gr-N/Co), synthesized by anchoring N and Co species on the aluminum-graphite (Al-Gr) surface, that could achieve efficient degradation of tetracycline (TC) by activating O2 in air purging water. RSs, including HO•, O2•− and 1O2, could be generated in the Al-Gr-N/Co/Air process, achieving 97.8 % of TC degradation at pH 7. This degraded TC can be attributed to the oxidation by 1O2 and HO•; direct adsorption by Al-Gr-N/Co also contributed to the TC degradation. The N species promoted the H2O2 production during O2 activation by Al-Gr-N/Co; these produced H2O2 could be further converted to RSs by Co and N species. Demethylation, hydroxylation and dehydration reactions were proposed as the oxidation pathways of TC by Al-Gr-N/Co/Air. TOC result suggests that TC and the oxidized intermediates could be adsorbed by Al-Gr-N/Co or converted to inorganic compounds. Negligible amount of the dissolved metal ions (<0.44 mg/L) was observed after reaction. Highly efficient removal of TC (>82.2 %) in lake water, tap water and MBR secondary effluents suggested that the Al-Gr-N/Co/Air process could be potentially applied in real water systems.