Electron Paramagnetic Resonance Analysis Research Articles

Electrochemical activation of periodate with graphite electrodes for degradation of high concentrations of thiocyanogen (SCN−) in mineral processing tail liquid

Cyanide has been widely used in gold extraction due to its cost-effectiveness, high selectivity and recovery. Regrettably, its wide application also leads to the presence of a large amount of thiocyanogen (SCN−) in the tail liquid of mineral processing plants, which affects the quality of the effluent water, and thus poses a threat to the ecological environment and human health. This paper investigates the degradation of high concentration of SCN− in water using electrochemical oxidation/periodate (E-GP/PI) system. A degradation rate of 90.25 % of SCN− was achieved by optimising various operating parameters. The effects of organic matter and typical heavy metal ion concentrations on the degradation of SCN− were investigated, and it was found that Cu2+ was able to promote the degradation of SCN− through the formation of stable complexes with SCN−, which enhanced the degradation rate to 96.48 %. However, the presence of Octadecyltrimethylammonium bromide (OTAB) and butylxanthin hindered the degradation process, where 500 mg/L of OTAB reduced the degradation rate of SCN− to 80.88 %, while 100 mg/L of butylxanthin reduced the degradation rate to 78.66 %. On this basis, experiments were carried out using real wastewater samples and SCN− degradation efficiencies of about 90 % were obtained. Afterwards, through electron paramagnetic resonance analysis, free radical burst, ion chromatograph and other research techniques, IO3 and O2– were obtained as the main drivers of SCN− degradation and SCN− degradation pathways were elucidated. Finally, the E-GP/PI system was shown to be effective in reducing the ecotoxicity of SCN− by increasing the 24-h LC50 from 12.5 % to 48.5 % in a toxicity test with daphnia. This study provides a new idea for the green and efficient treatment of SCN− rich beneficiation tail liquid.

Structural, optical, luminescent and magnetic properties of Gd2O3 nanoparticles: A comparative study on the effect of different green fuels in the sol–gel synthesis tactics

In this study, five samples of Gd2O3 NPs (size range: 4–33 nm) were synthesized by five different green facile and diverse natural products acting as reducing & stabilizing agents such as: fresh juices of sugarcane, lemon, tomato & orange fruits and citric acid via self combustion sol–gel tactics. Powder X-ray diffraction (PXRD), High resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) and Raman analysis affirmed cubic-C type crystal structure of Gd2O3 NPs prepared using citric acid, lemon juice and sugarcane juice. Mixed cubic and monoclinic phases were observed in Gd2O3 NPs prepared using tomato and orange juices. Notably, NPs of Gd2O3 in quantum dot regime (size: 6 ± 2 nm) were produced in the fresh sugarcane juice mediated synthesis protocol. Fresh lemon juice and sugarcane juice were appeared to be the most efficient green fuel for producing quality samples of Gd2O3 NPs. Optical absorption studies showed that bandgap in these Gd2O3 NPs is strongly dependent on the preparation protocol and type of green fuel. Interestingly, highest and lowest band gap of 4.91 eV and 4.43 eV were obtained for Gd2O3 NPs fabricated with orange and lemon juices, respectively. Photoluminescence (PL) and electron spin resonance (ESR) analysis affirmed formation of Schottky and Frenkel surface defects along with self trapped excitons and oxygen vacancies in these Gd2O3 NPs. Paramagnetic character of these Gd2O3 NPs at 300 K is validated by dc-magnetization and ESR studies. Present study demonstrated that microstructural, optical absorption and photoluminescence properties of Gd2O3 NPs can be easily customized by choice of natural products in the synthesis tactics.

Degradation of carbamazepine in piezo-activation of persulfate systems: Comparison of PDS and PMS

The choice of persulfate (PS) is crucial to the degradation and energy efficiencies for piezo-activation of PS (PE-PS) systems. Herein, a comparison between piezoelectrically activated peroxydisulfate (PDS) and peroxomonosulfate (PMS) using BaTiO3 are comparatively investigated for carbamazepine (CBZ) degradation. By contrast, the PE-PMS system achieves better degradation and mineralization of CBZ, as well as higher reaction stoichiometric efficiencies (%RSE). Nevertheless, the energy consumption of the PE-PDS system is only 9.69% of the PE-PMS system. The quenching test, chemical probe determination, and electron spin resonance (EPR) analysis suggest that the concentration of •OH, SO4∙-, and 1O2 except ∙O2- of the PE-PMS system, is higher than that of the PE-PDS system. The piezoelectric current density and carrier separation efficiency of the PE-PMS system are higher than that of the PE-PDS system, demonstrating that the piezoelectrically activated PMS has higher reactivity than piezoelectrically activated PDS. The ∙O2- and •OH are the primary ROS in the PE-PDS system, while 1O2 and •OH are the major ROS in the PE-PMS system. Additionally, CBZ is effectively degraded by both PE-PMS and PE-PDS systems from actual water sources. This work compares the performance, energy cost, and mechanism of PE-PMS and PE-PDS systems systematically. Hopefully, all of that is designed to tender a helpful reference for the choice of PS in piezocatalytic research and application.

Magnetic MgFeO@BC Derived from Rice Husk as Peroxymonosulfate Activator for Sulfamethoxazole Degradation: Performance and Reaction Mechanism.

Heterogeneous Mg-Fe oxide/biochar (MgFeO@BC) nanocomposites were synthesized by a co-precipitation method and used as biochar-based catalysts to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) removal. The optimal conditions for SMX degradation were examined as follows: pH 7.0, MgFeO@BC of 0.4 g/L, PMS concentration of 0.6 mM and SMX concentration of 10.0 mg/L at 25 ℃. In the MgFeO@BC/PMS system, the removal efficiency of SMX was 99.0% in water within 40 min under optimal conditions. In the MgFeO@BC/PMS system, the removal efficiencies of tetracycline (TC), cephalexin (CEX), ciprofloxacin (CIP), 4-chloro-3-methyl phenol (CMP) and SMX within 40 min are 95.3%, 98.4%, 98.2%, 97.5% and 99.0%, respectively. The radical quenching experiments and electron spin resonance (ESR) analysis suggested that both non-radical pathway and radical pathway advanced SMX degradation. SMX was oxidized by sulfate radicals (SO4•-), hydroxyl radicals (•OH) and singlet oxygen (1O2), and SO4•- acted as the main active species. MgFeO@BC exhibits a higher current density, and therefore, a higher electron migration rate and redox capacity. Due to the large number of available binding sites on the surface of MgFeO@BC and the low amount of ion leaching during the catalytic reaction, the system has good anti-interference ability and stability. Finally, the intermediates of SMX were detected.

Facile synthesis of ultrafine Co3O4/Al2O3 catalysts for superior peroxymonosulfate activation in rhodamine B degradation

Advanced oxidation processes based on persulfate (PS-AOPs) have emerged as effective strategies for environmental remediation, with cobalt-based oxides serving as prominent catalysts for peroxymonosulfate (PMS) activation. In this study, we developed a highly active Co3O4/Al2O3 catalyst (Co/AA) featuring ultrafine nanoparticles, synthesized via a facile approach using tannic acid (TA) as a coordinating agent and activated alumina as a robust support. Co/AA-0.1, as the representative catalyst, was characterized and exhibited outstanding performance in degrading rhodamine B (RB) via PMS activation. Our findings highlight TA's critical role in reducing Co3O4 nanoparticle size, thereby increasing the availability of active sites. The degradation mechanism was elucidated through reactive oxygen species (ROS) quenching experiments and electron paramagnetic resonance (EPR) analysis, revealing that sulfate radicals (SO4•−) are the dominant ROS. The high activity of Co/AA-0.1 is confirmed by analyzing X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area and O2-temperature programmed desorption data of the samples. We also investigate the effects of various factors, such as anions, reaction temperatures, and PMS dosage, on RB degradation. Higher temperatures for treating the catalyst are found to reduce activity but improve stability. Notably, the catalyst synthesized through EDTA-assisted synthesis showed balanced activity and stability. Furthermore, the versatility of our synthesis method was demonstrated by successfully applying it to other supports, such as SiO2 and TiO2, offering the development of more efficient and stable catalysts for environmental applications.

Efficient activation of peroxyacetic acid by cobalt-iron alloy/oxide heterojunctions anchored in defect-rich biochar for pesticide degradation in water: Unravelling the radical-unradical mechanism

The activation processes of peracetic acid (PAA-AOPs) have garnered significant attention in wastewater treatment. In this study, an amorphous carbon-modified bimetallic CoFe alloy/oxide catalyst (CoFe@DBCx-y, where x represents biomass mass and y represents pyrolysis temperature) was developed to activate PAA for the degradation of organochlorine pesticides (OCPs). Due to the size effect, biochar dynamically regulates the particle size of metal species, which is influenced by the pyrolysis temperature. Among these systems, the CoFeDBC2.0–700/PAA oxidation system effectively removed 95.7 % of 2,4-dichlorophenoxyacetic acid (2,4-D), exhibiting a kinetic constant 1.7 times higher than that of the Nano/PAA system. Furthermore, quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that high-valent metal oxides (MIV = O) and singlet oxygen (1O2) are the primary active species responsible for the removal of 2,4-D, whereas organic radicals (RO·) and hydroxyl radicals (·OH) play a secondary role. Electrochemical and Raman spectroscopy tests revealed the formation of a metastable surface complex (≡Co(III)–OO(O)CCH3) between PAA and the catalyst, which acted as an intermediate oxidant to generate reactive oxygen species (ROS) through a chain reaction. Carbon defects in the biochar functioned as an electron source, continuously replenishing the electrons consumed in the reaction and facilitating the valence cycling between Co and Fe. This study provides new insights into the remediation of pesticide-contaminated wastewater using PAA-AOPs with heterogeneous bimetallic carbon-based catalysts.

Pt-supported on N-doped carbon/TiO2 nanomaterials derived from NH2-MIL-125 for efficient photo-thermal RWGS reaction

To mitigate carbon dioxide (CO2) emissions and advance carbon neutrality, the conversion of CO2 into value-added fuels and chemicals via the reverse water–gas shift (RWGS) reaction is recognized as a promising approach. In this study, we designed platinum (Pt)-loaded nitrogen-doped carbon composite dual-phase titanium dioxide (TiO2) nanomaterials to achieve efficient photo-thermal performance in the RWGS reaction. The incorporation of Pt, nitrogen doping, and the selection of an appropriate calcination temperature enhance light responsiveness and reduce the recombination of photo-generated carriers, thereby improving the efficiency of the photo-thermal RWGS reaction. The optimized catalysts exhibited a high CO2 conversion (42.79 %), a carbon monoxide (CO) production rate (81.46 mmol gcat−1 h−1) and over 99.9 % selectivity under conditions of 400 °C and 1.2 W cm−2 light illumination. In addition, electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analyses revealed that Pt/TiO2@CN-525 was enriched with more oxygen defects, which was facilitate the adsorption and activation of CO2. CO temperature-programmed desorption (CO-TPD) showed that Pt/TiO2@CN-525 possesses a strong desorption capacity for CO. In addition, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) pointed to COOH* as a key intermediate in the reaction process. The photo-thermal co-catalyzed CO2 reduction by CO-TPD as well as in-situ DRIFTS indicated that Pt/TiO2@CN-525 follows the RWGS reaction. This work provides a potential strategy for the synthesis of catalysts for enhancing photo-thermal co-catalyzed RWGS reactions.

Fe3C@Fe decorated carbonized wood Fiber catalyst for organic dyes degradation: Preparation, characterization and mechanism

The extensive use of organic dyes has led to significant water pollution. Using lignocellulosic waste as a precursor for catalysts preparation for sewage remediation presents an effective alternative with numerous advantages in sustainability, cost-effectiveness, and environmental compatibility. In this work, wood fiber waste collected from wood processing plants was decorated with Prussian blue (PB) and then annealed to produce carbonized wood fiber catalyst (Fe3C@Fe-CB). In the presence of peroxymonosulfate (PMS), the prepared catalyst could achieve over 98.69 % efficiency in degrading methylene blue (MB) solutions (20 mg/L) in 60 min across a pH range of 3 to 11. Electrochemical test and electron paramagnetic resonance (EPR) analysis respectively verified that electron transfer pathway and radical pathway were the key factors for the degradation of MB. Cyclic degradation tests demonstrated that the degradation efficiency remained above 93.67 % after five recycling experiments. Moreover, the used magnetic catalyst can be easily recycled by magnet. This study proposed a facile and sustainable carbonized wood fiber catalyst decorated by Fe3C@Fe-CB, which could realize efficient elimination of organic dyes. Moreover, we offered a novel choice for dyes-polluted water treatment and paving a new route for converting low-value lignocellulosic waste to high-value utilizations.

Sulfadimethylpyrimidine degradation by non-radical dominated peroxomonosulfate activated with geopolymer-loaded cobalt catalysts

Geopolymers are frequently employed as adsorbent materials to treat heavy metals in wastewater due to their special structure analogous to that of zeolites. Nevertheless, their utilization as catalyst supports has not been extensively employed. In this study, geopolymers were modified using carboxymethyl chitosan and subsequently converted into zeolite through the hydrothermal method. Following calcination with Co loading, Co@MGA was obtained. The results indicated that as-prepared Co@MGA exhibited an excellent performance in activating PMS to degrade SMT. Moreover, the mineralization rate of SMT reached 76 %. Quenching experiments and electron paramagnetic resonance analyses had demonstrated that the non-radical pathway predominated in the degradation process of SMT, and 1O2 was the primary reactive oxygen species. The formation of surface bond was further elucidated through in-situ Raman spectroscopy and electrochemical tests. The potential mechanism and pathways of SMT degradation within the Co@MGA/PMS system were proposed. The system exhibited adaptability to different pH levels and robust resistance to inorganic ions and humic acid. Co@MGA demonstrated excellent reusability and stability, suggesting that Co@MGA is a highly promising catalyst for the activation of PMS.

Porous biochar supported PET plastic waste MOF heterostructure as a novel, efficient and recyclable catalyst for acetaminophen degradation

Herein, the innovative hybrid photocatalyst PET-based Zn-MOF on orange peel biochar (BC)(PZM/BC) was designed and synthesized via the hydrothermal method. Electrochemical methods have been used to demonstrate the action of the PET-MOF in the PZM/BC photocatalyst as a medium for electron transfer. The latter involved the synthesis of a zinc-containing metal–organic framework (MOF) in which the linkers were derived from the depolymerization of polyethylene terephthalate (PET) originating from plastic wastes. According to research, the catalytic reactions are sped up when porous BC and linker PET are assimilated into PZM/BC photocatalyst hetero-junction. Furthermore, BC stored electrons under light and released these electrons under dark conditions. When BC was combined with PET-MOF, the electrons on the biochar activated the catalytic redox activity of acetaminophen. Additionally, it lowers the reassimilation rate due to the combined meshed nanostructures and functionality of PET-MOF and PZM/BC. UV–Vis DRS, Mott-Schottky, Photoluminescence(PL), and Electrochemical Impedance spectra(EIS) results showed that the PZM/BC exhibited efficient spatial separation and transportation of photogenerated charge carriers and exhibited superior photocatalytic ability. Electron spin resonance(ESR) analysis confirmed that ⋅OH and h+ were the predominant radical species responsible for the degradation of acetaminophen(ACT). The optimum conditions for ACT removal were observed at pH 6.07, with a PZM/BC dosage of 0.1 g L−1, and an initial ACT concentration of 50 mg L−1, highlighting the pivotal role of the PZM/BC system in ACT degradation. Furthermore, potential photocatalytic degradation pathways of ACT were inferred renders on the identified intermediates which are responsible for the degradation of refractory intermediates. Regeneration trials were carried out to assess the stability of the photocatalyst. Additionally, the degraded intermediates generated during the degradation processes were examined, providing a comprehensive elucidation of the degradation mechanism.Graphical

Photodegradation of Polyethersulfone (PES), Polyvinylidene Fluoride (PVDF) and Polymethyl Methacrylate (PMMA) Microplastics via a Metal Organic Framework Namely ZIF-8/ZnO/C

The aim of this study was to photodegrade the Polyethersulfone (PES), Polyvinylidene fluoride (PVDF) and Polymethyl methacrylate (PMMA) microplastics using Zeolitic imidazolate framework-8/Zinc oxide/Carbon (ZIF-8/ZnO/C) nanocomposite generated under laboratory conditions. The produced nanocomposite was analysed using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Photo Spectroscopy (XPS), Scanning Electron Microscope (SEM), Diffuse reflectance UV-vis spectra (DRS) and Electron Spin Resonance (ESR) analyses. The maximum PES, PVDF and PPMA photodegradation yields were 99%, 98%, and 96%, respectively, at 1 mg/l ZIF-8/ZnO/C nanocomposites (NCs) concentration, 1000 mg/l microplastics concentration, at pH = 10.0, at a temperature and photodegradation time of 40°C and 20 min, under oxic conditions at a sunlight intensity of 80 W/m<sup>2</sup> and a photon yield of 16. The XRD analysis showed the generation of ZIF-8/ZnO/C, while the FTIR analysis indicated the ZnO, C, and ZIF-8.

Cu-Co binary metal-organic framework nanosheets for highly efficient degradation of norfloxacin using the Fenton-like process

Efficient catalyst development for hydrogen peroxide activation is crucial in advanced oxidation processes (AOPs) technology. In this study, we successfully synthesized a bimetallic organic framework incorporating Cu-Co MOF nanosheets via a one-pot strategy. The subsequent Cu-Co MOF nanosheets demonstrated outstanding oxidative activity, achieving a remarkable 95.37 % removal of norfloxacin (NOR), surpassing the efficacy of Cu MOF/H2O2 or Co MOF/H2O2 nanosheets alone by 1.34 and 2.59 times, respectively. Density functional theory (DFT) calculations revealed that the bimetallic MOF nanosheets: firstly, enhanced optimization of the adsorption energy for H2O2 activation; and secondly, facilitated the cleavage of the O–O bond in H2O2. Furthermore, electrochemical impedance spectroscopy (EIS) analysis demonstrated a significant improvement in interfacial electron transfer once dual-reaction centers were introduced into the Cu-Co MOF nanosheets. Electron paramagnetic resonance analysis and quenching tests confirmed that 1O2, ·O2− and ·OH were involved in NOR degradation. Reasonable NOR degradation pathways were proposed by analysing the results of LC-MS and DFT calculations. Moreover, the synthesized nanosheets exhibited excellent reusability, with more than 90.00 % NOR removal achieved using the Cu-Co MOF nanosheets/H2O2 system after reuse on 3 occasions. These findings underscore the effectiveness of bimetallic MOF construction in developing highly efficient MOF-based Fenton-like catalysts. Also highlighted here is the promising role of Cu-Co MOF nanosheets in wastewater treatment, particularly for the removal of antibiotics.

Improving storage duration of tomatoes (Solanum lycopersicum) through electron beam technology.

Electron beam (EB) technology typically consists of high-energy electron streams produced by a linear accelerator. Although promising, the use of EB irradiation as a technique to delay ripening and prevent spoilage in tomatoes has not been extensively investigated. In this study, the effectiveness of EB irradiation in prolonging the shelf life of tomatoes postharvest was investigated. The results indicated that EB irradiation successfully reduced microbial contamination and decay, preserved key quality attributes (such as total soluble solids, titratable acidity, pH, and firmness), and significantly minimized weight loss. Notably, the treatment delayed the biosynthesis of lycopene, a key indicator of ripening, without adversely affecting phenolic content and antioxidant activity, which remained consistent regardless of irradiation. Additionally, different methods for detecting irradiation were evaluated. Thermoluminescence analysis proved to be the most dependable technique, especially for doses exceeding 600Gy, due to its high sensitivity and specificity. In contrast, photostimulated luminescence and electron spin resonance analyses showed limitations in accurately identifying the irradiation status of foods with high moisture content, such as tomatoes. This study confirms that EB irradiation, while maintaining postharvest quality, extends the shelf life of tomatoes by 5-10days, suggesting its potential for commercial application in food preservation.

Light switchable radical and non-radical periodate activation by Fe3O4/g-C3N4 for efficient organic contaminant elimination

Although the heterogeneous activation of periodate (PI) has recently garnered significant attention for organic pollutant degradation, regulating the non-radical and radical reaction pathways remains a challenge. Herein, a Z-scheme Fe3O4/g-C3N4 heterojunction (FCN) was developed to achieve controllable radical and non-radical PI activation using a light switch. In the dark, the interaction between FCN and PI gave rise to metastable surface-activated PI complexes (PI*) via the non-radical pathway, which served as the dominant reactive species for organic elimination. Upon light irradiation, FCN acted as an electron donor for PI activation via the radical pathway, forming iodate radicals (IO3•) for pollutant destruction. Consequently, the FCN/PI/VIS system achieved complete removal of acid orange 7 in 30 min, with a pseudo-first order reaction rate about 3.5 times higher than that of FCN/PI system. The involved reactive species were validated by scavenging tests, electron paramagnetic resonance (EPR) analysis, Raman spectra and electrochemical measurements. Moreover, the light switchable FCN-based PI activation system exhibited high recyclability and practicability for the treatment of various organic pollutants in water. This study provides new insights into the PI activation-mediated wastewater treatment processes.

Fabrication and photocatalysis of novel Z-scheme Cu2O/Cu-Ag/AgCl heterojunction possessed broad-spectrum antibacterial performance and degradation capabilities

The construction of nanostructured Z-heterostructures is a potent strategy for achieving efficient photocatalyst synthesis. Herein, a novel Cu2O/Cu-Ag/AgCl (CCAA) Z-scheme heterostructure was created via photoreduction precipitation and utilized for pollutant decomposition and microorganism inactivation. Subject to visible light (λ > 420 nm) illumination, specimen CCAA-2 demonstrated superior photodegradation competence for Congo Red (CR), achieving a degradation rate of 92.6 % within 60 min. The superior removal performance is attributed to the Z-scheme heterostructure, featuring precise interfacial contact, and the combined effect of adsorption and photocatalytic activity. Meanwhile, the optimal sample, CCAA-2, was able to achieve 100 % inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) within 15 min under visible light. The photocatalytic performance of CCAA nanocomposites is primarily attributed to the surface plasmon resonance (SPR) effect of the noble metal Ag and the fabrication of Z-Scheme heterostructures to improve the utilization efficiency of electrons (e-) and holes (h+). Particularly, the photocatalytic mechanism was scrutinized via active substance capture experiments and electron spin resonance (ESR) analysis, uncovering that •O2ˉ and h+ served as key active constituents. Hence, this research presents a feasible approach for designing and constructing Z-Scheme heterojunctions for efficacious removal of contaminants from water.

Enhanced activation of peroxymonosulfate by introducing Co/Fe atoms in LaCoO3-biochar derived catalysts for the degradation of sulfamethoxazole

In this study, a novel perovskite-biochar composite, LaCoMO3-C (LaCoM-C, M = Cu, Fe), was designed using a co-precipitation-calcination strategy and employed activation of peroxymonosulfate (PMS) for efficiently degrade sulfamethoxazole (SMX). The degradation results indicated that the LaCoCu-C/PMS system could effectively degrade 95 % of SMX within 7 min with a kinetics rate constant of 0.33 min−1, which was about 2.21, 6.64 and 3.7 times that of LaCoFe-C, LaCoCu and LaCo-C, respectively. The biochar skeleton greatly increased the specific surface area and uniform distribution of surface active sites of the composites, leading to the optimization of its catalytic performance. Density Functional Theory (DFT) calculations demonstrated that the adsorption capacity of the composites with PMS could be improved by introducing Cu/Fe elements into the interfacial structure of the composites, while Co was identified as the dominant active site. Combined with quenching test, electron paramagnetic resonance(EPR) and X-ray photoelectron spectroscopy (XPS) analyses, we demonstrated the generation of reactive oxygen species including 1O2, •OH, SO4•- and O2•-, and revealed that the oxidation process of Cu+/Cu2+ and Co2+/Co3+ on the LaCoCu-C surface contributes to PMS activation. This work constitutes an insightful reference for the development of catalysts based on perovskite B-site for efficient activation of PMS.

Weak magnetic field for enhanced degradation of sulfamethoxazole by the CoFe2O4/PAA system: Insights into performance and mechanism

In this work, a novel approach coupling a heterogeneous weak magnetic field (WMF) with the CoFe2O4/peroxyacetic acid (PAA) system was employed to enhance the degradation of sulfamethoxazole (SMX). Under the optimized conditions of 50 mT WMF, 0.1 g/L CoFe2O4, 0.2 mM PAA, and initial pH 6.0, a complete degradation of 10 μM SMX was achieved in 25 min, exhibiting a high synergistic coefficient of 1.61. This result indicates a significant synergistic effect among WMF, CoFe2O4, and PAA in effectively degrading SMX. The introduction of WMF did not alter the pH application range of the CoFe2O4/PAA system. Furthermore, the degradation efficiency of SMX by the CoFe2O4/PAA/WMF system was significantly reduced in the presence of humic acid (HA) and bicarbonate ions (HCO3−), while chloride ions (Cl−) exhibited a minor inhibitory effect. Quenching experiments and electron paramagnetic resonance (EPR) analysis reveal that WMF did not alter the types of reactive oxygen species (ROS) generated in the CoFe2O4/PAA system. The degradation of SMX in the CoFe2O4/PAA/WMF system involved both radical (CH3C(O)O∙ and CH3C(O)OO∙) and non-radical (1O2) oxidation pathways, driven by the redox cycling between ≡Co2+/≡Co3+ and PAA, as well as the rapid adsorption and transformation of oxygen (O2) at oxygen vacancies (OV), respectively. The presence of WMF enhanced the utilization of PAA by CoFe2O4 by improving the convection and mass transport in the solution, facilitating the formation of superoxide anion (O2∙−) and supplemented lattice oxygen (O2−) through the directional migration of paramagnetic O2 towards the CoFe2O4 surface, thus significantly promoting ROS formation. Additionally, the degradation pathways of SMX in the CoFe2O4/PAA/WMF system were proposed based on density functional theory (DFT) calculations and the detected transformation products (TPs). The toxicity of SMX was effectively reduced, as verified by predictions from the Ecological Structure-Activity Relationship Model (ECOSAR) procedure. The excellent catalytic performance, reusability, and effective degradation of various organic pollutants demonstrated by the CoFe2O4/PAA/WMF system suggest its potential as a promising strategy for water treatment.

Efficiency and mechanistic insights of photocatalytic degradation and sterilization utilizing g-C3N4/WO3-x Z-scheme heterojunction under full-spectrum light

Designing highly efficient full-spectrum responsive Z-scheme heterojunction for wastewater decontamination and disinfection is urgently essential. Herein, a novel Z-scheme g-C3N4/WO3-x heterojunction was successfully synthesized by a facile wet impregnation method for the highly efficient photocatalytic degradation and sterilization. Benefiting from the accelerated charge separation, broadened light absorption to near infrared region, and appropriate band energy, optimized g-C3N4/WO3-x heterojunction exhibited photocatalytic degradation of 86.3 % and 97.4 % tetracycline in 2 h under visible light and full-spectrum light, respectively. Meanwhile, 6.5-log of Escherichia coli strains could also be inactivated by optimized g-C3N4/WO3-x heterojunction within 45 min and 15 min under visible light and full-spectrum light, respectively. Impressively, it also exhibited desirable anti-interference ability and satisfying photocatalytic degradation capacity with various key experimental parameters. The plausible degradation pathways of TC and the main active species involved in the photocatalysis were investigated based on liquid chromatography-mass spectrometer (LC-MS) and electron paramagnetic resonance (EPR) analysis. Mineralization process of TC was further confirmed by three-dimensional fluorescence spectra (3D EMMs). Besides, Toxicity Estimation Software Tool (T.E.S.T.) and Ecological Structure-Activity Relationships (ECOSAR) program were applied to predict the noxiousness of TC and its potential intermediates. The results suggested that the excitotoxicity of intermediates generally decreased relative to the pristine TC. Finally, we propose a plausible enhancement mechanism of photocatalytic degradation and sterilization. This work sheds a new light on the design of novel full-spectrum responsive Z-scheme heterojunction for environmental remediation.

Electron paramagnetic resonance study of the paramagnetic centers in gamma-irradiated 2-nitrobenzoic acid single crystal

2-nitrobenzoic acid (C7H5NO4) (2NBA) single crystals were made paramagnetic using 60Co-gamma rays. An attempt was made to detect the resonance form formed in 2-nitrobenzoic acid single crystal with Electron Paramagnetic Resonance (EPR) Spectroscopy. EPR spectra were taken at 125 K in three different axes of the crystal. As a result of EPR analysis of gamma irradiated 2NBA single crystal, it was understood that 2NBA anion radical was formed. The principal values of the hyperfine structure constants, the principal values of the g-tensor and their direction cosines were calculated.

Electron Paramagnetic Resonance Analysis of Hydroquinone Polymerization Catalyzed by Small Laccase

AbstractLaccases are multi‐copper oxidases (MCOs) that oxidize a broad range of substrates while reducing molecular oxygen to water. Although much effort has been made to elucidate the catalytic mechanism of laccases, information about reactive catalytic intermediates during catalysis is not yet fully understood. Herein, hydroquinone (HQ) polymerization catalyzed by prokaryotic small laccase (SLAC) was investigated by electron paramagnetic resonance (EPR) spectroscopy to provide more information on the catalytic mechanism. Briefly, free radical intermediates during the catalysis were investigated by real‐time in situ EPR measurement to monitor the formation and transformation of free radicals. A paramagnetic species was identified which was attributed to a copolymer formed by hydroquinone, benzoquinone, and semiquinone radical. In addition, the low‐temperature EPR spectrum of the trinuclear copper center during catalysis not only revealed tentative rotational motion of the histidine imidazole rings coordinating the TNC upon electron uptake but also provided evidence of the formation of oxygen bridge at TNC during the reaction, represented by the observation of a new type 2 copper component featured larger g// values and smaller A// values. Together, EPR spectroscopic insights into the catalytic intermediates during enzymatic hydroquinone polymerization have extended the knowledge of the biophysical characteristics and catalytic mechanism of SLAC.