Electron Paramagnetic Resonance Results Research Articles

Persulfate oxidation of tetracycline, antibiotic resistant bacteria, and resistance genes activated by Fe doped biochar catalysts: Synergy of radical and non-radical processes

To reduce the adverse effects of antibiotics and antibiotic resistance genes (ARGs) in the environment, this study employed iron-loaded biochar (Fe-LBH) as an activator in a persulfate (PDS) oxidation system to degrade tetracycline (TC), inactivate antibiotic resistant bacteria (ARB), and remove ARGs. TC was removed efficiently (more than 85%) in the Fe-LBH-PDS system within 30 min, which was higher than that in the pristine biochar-PDS system (15.5%). The Fe doping amount in biochar, PDS, and catalyst dose significantly affected TC degradation. Furthermore, the Fe-LBH-PDS system inactivated 60.4% of ARB (Pseudomonas aeruginosa HLS-6) within 60 min. The removal efficiencies of ARGs (sul1 and sul2) and intI1 were 0.05–0.60- and 1.54–2.74 log2-fold, respectively. Fe (II) and oxygen functional groups (e.g., -C-OH and -C = O) were verified as the reactive sites for PDS activation. In addition, according to the results of electron paramagnetic resonance (EPR) and radical quenching experiments, the radical pathway dominated by OH and the non-radical pathway dominated by singlet oxygen (1O2) play synergistic roles in the Fe-LBH-PDS oxidation process. These findings provide a possible application of Fe-LBH-PDS for TC degradation and hindering antibiotic resistance dissemination in wastewater treatment practice.

Catalytic ozonation performance of graphene quantum dot doped MnOOH nanorod for effective treatment of ciprofloxacin and bromate formation control in water

A catalyst GQDs@MnOOH was successfully synthesized by attaching graphene quantum dots (GQDs) on the surface of MnOOH nanorods to boost catalytic ozonation of antibiotic, exemplified by ciprofloxacin (CIP). The result demonstrated that the GQDs@MnOOH/O3 system had the greatest CIP removal effectiveness, followed by that of MnOOH/O3 and O3 only. The 0.02 mM CIP was degraded with 99.9% efficiency in 30 min in the presence 9.6 mg L-1 of O3 catalyzed by 12.5 mg L-1 of GQDs@MnOOH. The kinetic rate constants ​​were in the order: GQDs@MnOOH/O3 (0.161 min−1) > MnOOH/O3 (0.079 min−1) > O3 (0.055 min−1). The GQDs@MnOOH could enhance CIP degradation and inhibit BrO3- formation in different water sources. Results of scavenger and electron paramagnetic resonance (EPR) experiments demonstrated that oxygen radical (O2•-), singlet oxygen (1O2), and hydroxyl radicals (•OH) were involved in CIP degradation by the GQDs@MnOOH/O3 system. Accordingly, the degradation pathways of CIP and mechanism of catalytic ozonation over GQDs@MnOOH were investigated and proposed. This research is expected to shed light on the connection between carbonaceous material and metal hydroxide in catalytic ozonation.

Photocatalytic CO2 Reduction to CH4 and Dye Degradation Using Bismuth Oxychloride/Bismuth Oxyiodide/Graphitic Carbon Nitride (BiOmCln/BiOpIq/g-C3N4) Nanocomposite with Enhanced Visible-Light Photocatalytic Activity

The use of visible-light-driven photocatalysts in wastewater treatment, photoreduction of CO2, green solar fuels, and solar cells has elicited substantial research attention. Bismuth oxyhalide and its derivatives are a group of visible-light photocatalysts that can diminish electron–hole recombination in layered structures and boost photocatalytic activity. The energy bandgap of these photocatalysts lies in the range of visible light. A simple hydrothermal method was applied to fabricate a series of bismuth oxychloride/bismuth oxyiodide/grafted graphitic carbon nitride (BiOmCln/BiOpIq/g-C3N4) sheets with different contents of g-C3N4. The fabricated sheets were characterized through XRD, TEM, SEM-EDS, XPS, UV-vis DRS, PL, and BET. The conversion efficiency of CO2 reduction to CH4 of BiOmCln/BiOpIq of 4.09 μmol g−1 can be increased to 39.43 μmol g−1 by compositing with g-C3N4. It had an approximately 9.64 times improvement. The photodegradation rate constant for crystal violet (CV) dye of BiOmCln/BiOpIq of k = 0.0684 can be increased to 0.2456 by compositing with g-C3N4. It had an approximately 3.6 times improvement. The electron paramagnetic resonance results and the quenching effects indicated that 1O2, •OH, h+, and •O2− were active species in the aforementioned photocatalytic degradation. Because of their heterojunction, the prepared ternary nanocomposites possessed the characteristics of a heterojunction of type II band alignment.

Efficient activation of peroxymonosulfate by MoS2 intercalated MgCuFe layered double hydroxide for phenol pollutant control

The application of MoS2 as an emerging cocatalyst in wastewater treatment is of great significance, but the efficiency of cocatalyst is often limited due to its easy agglomeration and insufficient interaction with the catalyst. Here, we used layered double hydroxide (LDH) as the catalyst and the growth template of MoS2 to achieve an efficient combination of catalyst and cocatalyst in the removal of organic pollutants by peroxymonosulfate (PMS) activation. The outcomes showed that the MoS2 intercalated LDH composite samples (MLDH) owned excellent phenol degradation performance, reaching nearly 100% removal within 10 min, and the calculated apparent rate constants were 2.3, 5.6, 17.7 and 19.8 times higher than that of the samples of directly growing MoS2 on the LDH (M@LDH), physically blended MoS2 and LDH samples, LDH and MoS2, respectively. Based on the results of electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), SO4•- had a major impact on the elimination of phenol, Mo(Ⅳ) in MoS2 also participated in and encouraged the Fe(Ⅲ)/Fe(Ⅱ) redox cycle, providing the driving force for the further activation of PMS. Moreover, the effects of pH value, anions, cations and water environment of MLDH during the activation of PMS were also determined, and it was found that under various catalytic environments, MLDH always maintained a high removal rate of phenol and showed strong anti-interference ability. Collectively, the results of this research would offer more possibilities and suggestions for creating highly effective catalysts for wastewater cleanup.

Is the sacrificial agent really just a sacrificial agent? A case study on the photocatalytic reduction of U(VI) by alcohols

Although organic sacrificial agents are often used to improve the efficiency of photocatalytic reactions, the impact of their existence on the performance evaluation of photocatalysts has not been analyzed yet. In this study, to clearly understand the role of organic sacrificial agents in the photocatalytic process, the photocatalytic reduction of hexavalent uranium (U(VI)) by alcohols is systematically analyzed. The results reveal that under the conditions of pH 5, nitrogen atmosphere, visible light irradiation, and no photocatalyst, the alcohol sacrificial agents can directly reduce U(VI) with efficiencies as high as 98%. Uranium dioxide, formaldehyde, and hydrogen ion are identified as the final products of the photocatalytic reaction, and the reaction mechanism is proposed based on the results of electron paramagnetic resonance (EPR) spectroscopy. Accordingly, it is inferred that alcohol as an organic sacrificial agent markedly interferes with the performance evaluation of photocatalysts during the photocatalytic reduction of U(VI). Overall, this study provides valuable insights into the actual role of sacrificial agents in the photocatalytic reduction process.

Gamma-Ray Irradiation Stability of Zero-Dimensional Cs3Cu2I5 Metal Halide Scintillator Single Crystals

Zero-dimensional Cs3Cu2I5 is one of the most promising metal halide scintillators due to its large Stokes shift, photoluminescence quantum yields, freedom from toxic elements, and excellent energy spectrum resolution. To unlock the full potential of Cs3Cu2I5 as an effective alternative to traditional scintillators for gamma-ray detection, the irradiation stability of Cs3Cu2I5 single crystals under 60Co gamma rays with a maximum accumulated dose of 800 krad was explored. Although the luminescence mechanism remained unchanged after irradiation, the optical properties of Cs3Cu2I5 single crystals demonstrated a dose-dependent change at low accumulated doses (<600 krad). However, a further increase in the accumulated dose did not lead to more severe degradation and even slight performance recovery occurred. Electron paramagnetic resonance and theoretical calculation results revealed that the irradiation-induced Cs+-related Frenkel defects contribute to performance degradation. These results shed light on the microscopic mechanism of gamma-ray irradiation damage of Cs3Cu2I5 single crystal and provide guidance to their real application.

Aerobic oxidative lactonization of diols at room temperature over defective titanium-based oxides in water

Lactones are applied in pharmaceutical or agriculture/forestry industry as anesthetics/sedatives, pesticide intermediates or as plant growth regulators. Selective conversion of diols into value-added lactones under mild reaction conditions is still challenging. Here, we report on an environmentally benign catalytic approach using oxygen vacancies-enriched titanium-based oxides and water as solvent at room temperature for the lactonization of various aromatic and aliphatic diols. Lactonization was found to proceed in two consecutive steps: 1) the dehydrogenation of diols to hydroxyaldehyde intermediates catalyzed by the Pt cocatalyst; 2) the subsequent oxidative lactonization of the intermediates to the lactone products over defective titanium-based oxides. Diffuse reflectance infrared Fourier transform spectroscopy analysis using pyridine as probe molecule combined with electron paramagnetic resonance results suggest that oxygen vacancies as strong Lewis acid sites are pivotal for the superior catalytic activities at room temperature, which are attributed to the enhanced reaction rate of step 2 due to stronger adsorption of the hydroxyaldehyde intermediates on the Lewis acid sites.

Understanding the electro-cocatalytic peroxymonosulfate-based systems with BDD versus DSA anodes: Radical versus nonradical dominated degradation mechanisms

Herein, peroxymonosulfate (PMS) activation via electro-cocatalytic system with circulated Fe(III)/Fe(II) was investigated with boron-doped diamond (BDD) anode and dimensionally stable anode (DSA) for degradation of sulfamethoxazole (SMX). Radicals of OH and SO4− as well as non-radicals of 1O2 and Fe(IV) were all present in BDD/PMS/Fe(III) and DSA/PMS/Fe(III) systems, according to the results of scavenging experiment and electron paramagnetic resonance (EPR) analysis. Interestingly based on the results of chemical probe experiments, the ratio of OH, SO4−, and 1O2 were 9% (7.19 μmol/L), 76% (58.39 μmol/L), and 15% (11.45 μmol/L) in BDD/PMS/Fe(III) system, and were 28% (5.81 μmol/L), 18% (3.76 μmol/L), and 54% (10.93 μmol/L) in DSA/PMS/Fe(III) system. The yield of Fe(IV) in DSA/PMS/Fe(III) process was relatively higher than that in BDD/PMS/Fe(III) process. These results indicated that BDD/PMS/Fe(III) is a radical oxidation system while DSA/PMS/Fe(III) system is mainly non-radical system. Due to the high electrochemical activity of BDD anode, the one-electron transfer reaction might occur to produce more SO4−. The co-existing ions including Cl−, H2PO4−, and NO3− showed significant effects on the degradation efficiency of BDD/PMS/Fe(III) and nonsignificant impacts on DSA/PMS/Fe(III) process, indicating that DSA/PMS/Fe(III) process could be less affected by complex water matrix. BDD/PMS/Fe(III) is inclined to oxidize electron-rich contaminants, while DSA/PMS/Fe(III) is apt to oxidize electron-deficient contaminants. The degradation routes of SMX and its toxicity evolution were systematically studied with the analysis of byproducts. Overall results compared the oxidation mechanisms and primary oxidation pathways of electro-cocatalytic systems with BDD versus DSA anodes, and revealed the merits of each system for future selection and system optimization of treatment processes regarding targeted contaminants.

Rapid electron transfer-promoted tetracycline hydrochloride degradation: Enhanced activity in visible light-coupled peroxymonosulfate with PdO/g-C3N4/kaolinite catalyst

In this work, a novel highly dispersed PdO/g-C3N4/kaolinite (P/CNK) composite was synthesized to activate peroxymonosulfate (PMS) under visible light for tetracycline hydrochloride (TCH) degradation. The 4 %P/CNK catalyst showed the best catalytic ability for TCH degradation within 20 min (94.5 %) over the vis/PMS system. The favorable specific surface area and pore volume of CNK allowed for the high dispersion of PdO and the adsorption of PMS, while PdO anchoring on CNK endowed the catalyst with channels and acceptors that could accommodate a large number of electrons to achieve rapid transfer between electrons. Furthermore, kaolinite is inexpensive, and the plentiful hydroxyl groups on the kaolinite surface can accelerate the self-decomposition of PMS. The 4 %P/CNK system also showed excellent degradation efficiency under different pH conditions and maintained its catalytic activity (87.1 %) after five cycles. The intermediates produced during the degradation of TCH and the corresponding differences in aquatic toxicity were identified. The results of electron paramagnetic resonance and reactive oxygen species quenching experiments showed that 1O2 was the key reaction species, while O2− and h+ were secondary species during the degradation process. In addition to TCH, 4 %P/CNK also had good degradation and mineralization effects on sulfamethoxazole, chlortetracycline, and carbamazepine. This work provides a deep foresight into the efficient degradation of antibiotic pollutants by kaolinite-based catalytic materials in a photocatalytic coupled PMS system.

Synergetic Removal of Pb(II)- and Sulfonamide-Mixed Pollutants using Ni/Co Layered Double Hydroxide Nanocages Coupled with Peroxymonosulfate

Organic pollutants are often present in wastewater coupled with toxic metallic ions, which are harmful to both human beings and the ecological environment, and their simultaneous removal is of great significance. In this work, hollow Ni/Co layered double hydroxide (LDH) nanocages were synthesized through the hydrothermal method by using zeolitic imidazolate framework-67 as a self-sacrificial template, and it was further used as a catalyst to activate peroxymonosulfate (PMS) for sulfonamide (SA) degradation and an adsorbent for Pb(II) removal simultaneously. The materials were characterized using various techniques, and the effect of parameters including the dosage of the catalyst and PMS, initial temperature, and pH on the performances of the LDH nanocage was investigated. Nearly 80% of SA (15 mg/L) could be degraded via PMS activation, whereas ∼93% of Pb(II) (20 mg/L) could be removed simultaneously within 60 min. During the reaction, there were redox cycles for both Co and Ni over the surface of LDH, but Pb did not participate in the process, and it had a slightly negative effect on SA degradation. The quenching experiments and the electron paramagnetic resonance results showed that the radicals (•OH, •SO4–, O2•–, and 1O2) generated from PMS activation participated in the process. Finally, the possible mechanism and degradation pathways were proposed, based on the intermediate products identified, and the toxicity of the intermediate products was evaluated.

Layered β‐ZrNBr Nitro‐Halide as Multifunctional Photocatalyst for Water Splitting and CO2 Reduction

AbstractDeveloping mixed‐anion semiconductors for solar fuel production has inspired extensive interest, but the nitrohalide‐based photocatalyst is still in shortage. Here we report a layered nitro‐halide β‐ZrNBr with a narrow band gap of ca. 2.3 eV and low defect density to exhibit multifunctionalities for photocatalytic water reduction, water oxidation and CO2 reduction under visible‐light irradiation. As confirmed by the results of electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations, the formation of anion vacancies in the nitro‐halide photocatalyst was inhibited due to its relatively high formation energy. Furthermore, performance of β‐ZrNBr can be effectively promoted by a simple exfoliation into nanosheets to shorten the carrier transfer distance as well as to promote charge separation. Our work extends the territory of functional photocatalysts into the nitro‐halide, which opens a new avenue for fabricating efficient artificial photosynthesis.

Layered β-ZrNBr Nitro-Halide as Multifunctional Photocatalyst for Water Splitting and CO2 Reduction.

Developing mixed-anion semiconductors for solar fuel production has inspired extensive interest, but the nitrohalide-based photocatalyst is still in shortage. Here we report a layered nitro-halide β-ZrNBr with a narrow band gap of ca. 2.3 eV and low defect density to exhibit multifunctionalities for photocatalytic water reduction, water oxidation and CO2 reduction under visible-light irradiation. As confirmed by the results of electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations, the formation of anion vacancies in the nitro-halide photocatalyst was inhibited due to its relatively high formation energy. Furthermore, performance of β-ZrNBr can be effectively promoted by a simple exfoliation into nanosheets to shorten the carrier transfer distance as well as to promote charge separation. Our work extends the territory of functional photocatalysts into the nitro-halide, which opens a new avenue for fabricating efficient artificial photosynthesis.

D 6 h Symmetric Radical Donor–Acceptor Nanographene Modulated Interfacial Carrier Transfer for High-Performance Perovskite Solar Cells

<i>D</i> ^{6 <i>h</i>} Symmetric Radical Donor–Acceptor Nanographene Modulated Interfacial Carrier Transfer for High-Performance Perovskite Solar Cells

Electrochemical activation of persulfate by Al-doped blue TiO2 nanotubes for the multipath degradation of atrazine

The combination of electrolysis and persulfate activation (E/PDS) is a cost-effective method for the treatment of refractory organics. However, persulfate is difficult to be activated into radicals at the anode, resulting in insufficient electro-activation efficiency. Herein, Al doped blue TiO2 nanotube electrodes (Al-bTNT) were first employed as cost-effective anode materials to fully activate PDS to radicals. In E/PDS, the kinetic constant of atrazine removal by Al-bTNT (0.048 min−1) substantially outperformed the other anodes, including the blue TiO2 nanotube electrodes (bTNT) (0.024 min−1), Ti4O7 (0.02 min−1), and B doped diamond (BDD) anodes (0.023 min−1). The Al-bTNT-E/PDS exhibited a low energy consumption (EEO = 0.72 kWh m−3) and a high mineralization rate. Based on the results of electron paramagnetic resonance, quenching experiments, and probe experiments, we propose that atrazine degrades in the Al-bTNT-E/PDS system mainly via a novel radical pathway that involves both·OH and SO4·- and the generated SO4·- is responsible for the enhanced removal rate. The oxygen vacancies (VO) generated from interstitial Al may serve as the active sites to adsorb and dissociate the persulfate molecules based on extensive characterizations. The attempt at soil-washing wastewater disposal indicated the synergistic system possessed good potential for future practical application.

Co3O4 anchored on biochar derived from chitosan (Co3O4@BCC) as a catalyst to efficiently activate peroxymonosulfate (PMS) for degradation of phenacetin

Chitosan, as a bio-friendly and abundant biochar precursor, was employed to prepare cobalt-based catalyst (Co3O4@BCC) by calcination for activating peroxymonosulfate (PMS) to degrade phenacetin (PNT). Various characterization technologies and experimental designs were performed to investigate the physicochemical properties and catalytic performance of Co3O4@BCC. Approximately 99.0% of phenacetin (10 mg/L) was degraded in the system of Co3O4@BCC (0.05 g/L)/PMS (1.0 mM) within 15 min and the rate constant was 6 times higher than that in the system of Co3O4 (0.05 g/L)/PMS (1.0 mM). The results demonstrated that BCC as a carrier not only dispersed Co3O4 nanoparticles and improved the stability of catalyst, but also provided abundant electron-rich groups to facilitate the activation of PMS and the production of reactive oxygen species (ROS). Co3O4@BCC composite also exhibited good universality and reusability. More than 90% of BPA, SIZ and CAP was degraded by Co3O4@BCC activated PMS within 15 min at pH 7. The degradation rate of PNT was recovered from 90% to 98.0% via the regeneration of the used catalyst after the third run (calcination at 400 °C for 5 min). SO4•−, •OH and 1O2 were identified to be responsible for PNT degradation. Furthermore, the activation mechanism of PMS and the possible pathways of PNT degradation were reasonably speculated according to the results of electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), quenching experiments and HPLC-TOF-MS2. This study explored the application of chitosan as a recycled material and provides a feasible strategy for designing and fabricating environmentally friendly and efficient catalysts for PMS activation to degrade organic pollutants.

Enantioselective Radical Addition to Ketones through Lewis Acid-Enabled Photoredox Catalysis.

Photocatalysis opens up a new window for carbonyl chemistry. Despite a multitude of photochemical reactions of carbonyl compounds, visible light-induced catalytic asymmetric transformations remain elusive and pose a formidable challenge. Accordingly, the development of simple, efficient, and economic catalytic systems is the ideal pursuit for chemists. Herein, we report an enantioselective radical photoaddition to ketones through a Lewis acid-enabled photoredox catalysis wherein the in situ formed chiral N,N'-dioxide/Sc(III)-ketone complex serves as a temporary photocatalyst to trigger single-electron transfer oxidation of silanes for the generation of nucleophilic radical species, including primary, secondary, and tertiary alkyl radicals, giving various enantioenriched aza-heterocycle-based tertiary alcohols in good to excellent yields and enantioselectivities. The results of electron paramagnetic resonance (EPR) and high-resolution mass spectrum (HRMS) measurements provided favorable evidence for the stereocontrolled radical addition process involved in this reaction.

Electro-activating persulfate via biochar catalytic cathode for sulfamethazine degradation: Performance and mechanism insight

This work prepared biochar particle electrodes (BCPE) from excess sludge and biochar catalytic cathodes (BCCC) synthesized by modifying nickel foam electrodes with BCPE. Then, both of them were constructed as electrocatalytic systems for activating persulfate (PS) to degrade sulfamethazine (SMZ). BCPE demonstrated remarkable electrocatalytic PS performance, in which oxygen-containing functional groups and Fe3O4 are the main active sites. The quenching experiment and electron paramagnetic resonance (EPR) results indicate that free hydroxyl radicals, sulfate radicals and superoxide radicals are generated in solution of the particle electrode system. On the contrary, most of the above radicals generated by BCCC exist on the electrode surface, and the direct electron transfer from the power source to BCCC effectively improves the mass transfer rate and catalytic performance, thus leading to the complete degradation of 50 mg/L SMZ within 60 min. Fe2+/Fe3+ released by BCCC was below the ambient concentration, which constituted a stable cycle in the electrocatalytic system and efficiently activated PS. The calculation results of density functional theory and oxygen reduction reactions verified the mechanism of activation. Electrostatic surface potential distribution calculation showed that Fe and C were the main active site. In silico toxicity assessment by ADMETlab2.0 found a significant decrease in overall toxicity of SMZ degradation products.

Self-Doping Based Facet Junctions and Oxygen Vacancies in Ferroelectric Bi3TixNb2-xO9 Nanosheets for Boosting Photocatalytic Degradation and Antibacterial Activity.

Constructing facet junction in semiconductor photocatalysts has been demonstrated as an effective method to promote charge-carrier separation and suppress carrier recombination. Herein, we proposed a novel but facile self-doping strategy to regulate the crystal facet exposure ratio in ferroelectric Bi3TixNb2-xO9 single-crystalline nanosheets, thereby optimizing its facet junction effect. Through tuning the atomic ratio of Ti and Nb, the exposure ratio of {001} and {110} crystal planes in Bi3TixNb2-xO9 nanosheets can be delicately modulated, and more {110} facets were exposed with the increase of the Ti/Nb atomic ratio as evidenced by the X-ray diffraction and scanning electron microscopy results. A facet junction between {110} and {001} crystal planes was verified based on the density functional theory calculation and photodeposition experiment results. Photogenerated electrons tend to accumulate in {110}, while holes gathered in {001} crystal planes. Owing to the optimal facet junction effect, the sample of Ti1.05 shows the most efficient charge-carrier separation and transportation compared to Ti0.95 and Ti1.00 as supported by the photoluminescence, surface photovoltage, photoelectrochemistry, and electron paramagnetic resonance (EPR) results. In addition, the oxygen vacancy arising from the inequivalent substitution of Nb5+ by Ti4+ as proved by X-ray photoelectron spectroscopy and EPR results and the enhanced ferroelectricity supported by P-E loops can also assist charge-carrier separation and migration. Benefiting from these properties, Ti1.05 outperformed Ti0.95 and Ti1.00 in the photodegradation of organic dye and antibiotic molecules. Meanwhile, the excellent antibacterial activity of Ti1.05 under visible light was also demonstrated by the Escherichia coli sterilization experiment. This work not only presents a novel pathway to adjust the facet junction but also provides new deep insights into the crystal facet engineering in ferroelectrics as photocatalysts.

Degradation of pyrene in sediments based on the activation of peroxymonosulfate with nitrogen-doped magnetic biochar: Synergistic effect and mechanism

Pyrene (PYR) is a typical high molecular weight polycyclic aromatic hydrocarbon (HMW-PAH) with potential biotoxicity and resistance to biodegradation, and the accumulation of PYR in sediments increases the risk to ecosystems. Therefore, this study evaluated the catalytic performance of nitrogen-doped magnetic biochar-activated peroxymonosulfate system (NMBC/PMS) on PYR in sediments and elucidated its mechanism. The results showed that the degradation rate of PYR in sediments by the NMBC/PMS system reached 87% at PMS= 1 × 10−4 M, NMBC= 3.0 g/L and pH= 9, which conformed to the pseudo-first-order rate law, and the rate constant(Kobs) was 7.3 × 10−2 h−1. The high adsorption performance of NMBC was attributed to π-π electron donor-acceptor interactions (π-π EDA). The high degradation performance of NMBC/PMS system was attributed to the active sites generated by graphitization, magnetism, and electronegativity of NMBC, which were the key to activate PMS to degrade PYR. The results of X-ray photoelectron spectroscopy (XPS), quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that N-doping and Fe3O4-loading on NMBC synergistically promoted the degradation of PYR. In addition, the mechanism of PYR degradation by NMBC/PMS system was investigated, indicating that SO4·-, HO·and 1O2 were the main reactive oxygen species. The excellent recoverability of NMBC showed its application potential. The NMBC/PMS system developed in this study provided a theoretical basis for a future multi-pathway synergistic degradation mechanism of PYR in sediments.

On the mechanism of radiation and thermal-induced degradation of the insulation cables in nuclear power plants-the presence of long-lived polyenyl C-centered radicals

Radiolytically and thermally produced long-lived polyenyl C-centered radicals in the nuclear power plants’ insulation cables are detected and measured after more than 45 months of aging since the irradiation and the thermal treatment. Electron Paramagnetic Resonance (EPR) results of the irradiated Cross-linked Polyethylene (XLPE) and Ethylene Propylene Rubber (EthProRu), used as primary insulation materials at Nuclear Power Plants (NPP), clearly demonstrate the presence of polyenyl radicals along with allyl and peroxyl radicals. The yields of these free radicals are dose-rate dependent. EPR results also show the presence of the long-lived polyenyl along with allyl and peroxyl free radicals in the thermally treated XLPE, and EthProRu. These free radicals can cause a major failure in the performance of these cables in NPPs. Besides, the results showed the enhancement in the oxidation reactions due to the migration of copper ions from the conductor to the bulk of the insulation.This study also shows that the oxidation index (OI) and Elongation at Break (EAB) increases and decreases respectively at higher doses and temperatures.