Electron Paramagnetic Resonance Analysis Research Articles

Two-State Hydrogen Atom Transfer Reactivity of Unsymmetric [Cu2(O)(NO)]2+ Complexes.

We report the temperature-dependent spin switching of dicopper oxo nitrosyl [Cu2(O)(NO)]2+ complexes and their influence on hydrogen atom transfer (HAT) reactivity. Electron paramagnetic resonance (EPR) and Evans method analysis suggest that [Cu2(O)(NO)]2+ complexes transition from the S = 1/2 to the S = 3/2 state around ca. 202 K. At low temperatures (198 K) where S = 3/2 dominates, a strong correlation between the rate of HAT (kHAT) and the population of the S = 1/2 state was identified (R2 = 0.988), suggesting that the HAT by [Cu2(O)(NO)]2+ complexes proceeds by the S = 1/2 isomer. Installation of functional groups that introduce an unsymmetric secondary coordination environment accelerates the HAT rates through perturbation of the spin equilibria. Given the often unsymmetric coordination sphere of bimetallic active sites in natural proteins, we anticipate that similar strategies could be employed by metalloenzymes to control HAT reactions.

Co3O4 decoration on iron-contained biochar composite fabricated by co-pyrolysis of red mud and spent coffee ground: A synergistic hybrid for Rhodamine B degradation via peroxymonosulfate activation

In this study, a composite was prepared by co-pyrolysis of red mud (RM) and spent coffee grounds (SCG). Then, cobalt was incorporated in the as-prepared RM/biochar composite (RMBC) and employed as the heterogeneous activator of peroxymonosulfate (PMS) for Rhodamine B (RhB) degradation. A temperature-programmed reaction and X-ray diffraction (XRD) measurements disclosed that the hematite (Fe2O3) phase in RM experienced a step-wise reduction to magnetite (Fe3O4) and Fe0 with increasing temperature during the co-pyrolysis of RM and SCG. The RMBC exhibited low performance for PMS activation to degrade RhB. However, incorporating 1.5 wt% Co can drastically improve the catalytic performance. The influence of initial pH, catalyst dosage, initial RhB concentrations, and temperature on the degradation efficiency was investigated. The quenching experiments combined with electron paramagnetic resonance analysis proved that the ·OH and SO•−4radicals, and 1O2 no-radical were the main reactive species for RhB degradation in the Co3O4/RMBC/PMS system.

Electrochemical activation of periodate: A novel strategy for the degradation of sulfamethoxazole with wide applicable pH range

Herein, this work investigated a novel strategy utilizing electrochemical activation of periodate (EC/PI) for effective degradation of sulfamethoxazole (SMX) with wide appliable pH range. The EC/PI system achieved 100% degradation efficiency of SMX under optimum conditions of 7.78 mA/cm2 current density, 1 mmol/L IO4− dosage, and 20 mmol/L Na2SO4 as the supporting electrolyte. Strong synergistic effect between applied electric current and IO4− activation was observed, indicating the robustness of EC/PI system. Through a series of chemical probe experiments and electron paramagnetic resonance analysis, it was revealed that EC/PI is a composite oxidation system with multiple active species, including hydroxyl radical (•OH), iodate radical (IO3•), and singlet oxygen (1O2). The production mechanisms of these active species were comprised of two routes: direct production via the electrode supplying electrons and indirect production via hydrogen peroxide (H2O2) and superoxide radical (O2•−) as intermediates. The EC/PI process was slightly affected by the coexisting substances in the water background, and cycle experiments verified its degradation stability, indicating that this EC/PI system exhibits excellent capacity for treatment of authentic wastewater. Finally, the SMX degradation intermediates and pathways were obtained using mass spectrometry analysis and Gauss theory calculations. These results indicated the establishment of EC/PI system provides an efficient and environmental-friendly strategy for treatment of emerging organic pollutants.

Fabrication of visible-light-driven bulk carbon doped carbon nitride with enhanced photocatalytic activity for tetracycline degradation and mechanism insight

Carbon nitride (CN) has garnered considerable attention in the realm of pollutant treatment. However, the photocatalytic activity of pristine CN is severely restricted due to its limited light absorption and rapid recombination of photoinduced carriers. Herein, a rational configuration of dopant and precursor with similar chemical structure was employed to synthesize C doped CN (CCN) through the copolymerization of 2,4,6-triamine-pyrimidine (TAP) and melamine. The characterization results demonstrate that the incorporation of pyrimidine block from TAP monomer not only realizes nearly homogeneous C doping in bulk, but also controls the doping site accurately. Consequently, it enables the CN to process significant absorption in the visible light region, narrow the intrinsic band gap from 2.73 to 2.53 eV, and enhance separation efficiency of photoinduced carriers. As a result, the CCN as a visible-light-driven photocatalyst shows markedly enhanced photocatalytic activity compared with pristine CN in the degradation of tetracycline. The degradation rate constant of the optimal CCN is almost 6.30 times that of pristine CN under visible light. Moreover, the cyclic experiments reveal the favorable stability of CCN. In addition, •O2− and h+ responsible for the degradation of tetracycline are demonstrated by trapping experiments and electron spin resonance analysis. The work provides a straightforward and impactful copolymerization strategy to achieve bulk doping and control doping position within the CN framework for ameliorating the photoelectrical properties and photocatalytic activity.

Activated peroxymonosulfate with co-doped copper oxide nanomaterials for highly efficient degradation of organic pollutants

In the current work, a series of novel cobalt-doped copper oxide nanomaterials (Co-CuOT, subscript ‘T’ means ‘calcination temperature’) were prepared through the chemical reduction method following by calcination. Their reactivities were screened for the degradation of various organic pollutants including p-chlorophenol (4-CP) in the presence of peroxymonosulfate (PMS) as oxidant precursor. These as-prepared Co-CuOT nanomaterials possess exposed active surface as well as positive Cu-Co synergistic effect, and further enhances the 4-CP degradation by activating PMS. The Co-CuO300/PMS exhibited the best ability toward the 4-CP degradation, achieving 100% degradation of 4-CP and excess 80 % removal efficiency of total organic carbon (TOC) within 10 min at room temperature. The Co-CuO300 sample is two to thirteen folds dominative than the other samples (Co-CuO400, Co-CuO500, CuOcds and CoB), respectively. Attractive reactivities of Co-CuOT nano-catalysts are attributed to the amounts of oxygen vacancies, copper-cobalt synergy, and increased generation of reactive radicals. Based on quenching experiment and electron paramagnetic resonance (EPR) analysis, the degradation of 4-CP in the PMS/Co-CuO300 system was found to mainly depend on the species of free radicals, e. g., hydroxyl radical (•OH), sulfate radical (SO4•−). Meanwhile, Co-CuO300 displayed better recyclability and anti-interference ability. The reactivated catalyst after the fifth run still showed high degradation activity, even completely eliminating 4-CP. Substrate expense indicate that the Co-CuO300/PMS system exhibited high efficiency in the degradation of various types of organic pollutants including phenolic compounds and antibiotics under mild conditions. Phytotoxicity assessment showed that mung beans grew well in both the deionized water and the filtered degradation solution, suggesting highly remarkable elimination of 4-CP in Co-CuO300/PMS system. Overall, Co-CuOT nanocomposites hold great promise for large-scale practical application in the activation of PMS and subsequent degradation of organic pollutants.

Nitrogen self-doped chitosan carbon aerogel integrating with CoAl-LDH for ultra-efficient sulfamethoxazole degradation based on PS-AOPs: From batch to continuous process

Nitrogen self-doped chitosan carbon aerogel (NCCA) integrating with CoAl layered double hydroxide (CoAl-LDH) was successfully fabricated and utilized for the ultra-efficient activation of peroxymonosulfate (PMS) toward sulfamethoxazole (SMX) degradation. And the NCCA/CoAl-LDH-2 catalyst possessed the highest catalytic activity with 97.5% of SMX degradation efficiency in 5 min and 74.8% of total organic carbon (TOC) removal efficiency in 30 min, may being on account of the synergistic interaction between NCCA and CoAl-LDH. Additionally, the NCCA/CoAl-LDH-2 catalyst not only had good reusability and stability, but also could realize continuous degradation of SMX solutions via a fixed-bed reactor. Furthermore, the results of quenching tests, electrochemical measurements as well as electron paramagnetic resonance (EPR) analysis demonstrated that both non-radical and radical processes participated in the SMX degradation, in which the latter played a predominant role. X-ray photoelectron spectroscopy (XPS) corroborated that the main active sites were the CO groups and graphitic N of NCCA, and the Co3+/Co2+ redox cycle of CoAl-LDH. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis and density functional theory (DFT) calculation containing the laplacian bond order (LBO) and Fukui index were carried out to deeply explore the reasonable SMX degradation pathways. This current study provided a theoretical basis to design an efficient PMS activation system toward continuous antibiotics degradation.

Activation of periodate by self-recycled Ru(III)/TiO2 for selective oxidation of aqueous organic pollutants: Essential role of homogeneous Ru(V)=O species

Recently, metal catalysts have received much attention in periodate (PI) activation for production of reactive oxygen species to efficiently degrade organic contaminants, yet activation efficiency is cumbered with their sluggish catalytic cycle. In the study, TiO2 supported Ru(III) catalysts (Ru(III)/TiO2, 0.45 wt% as Ru) were used to catalyze PI activation for oxidation of aqueous organic pollutants. Ru(III)/TiO2 exhibited comparable performance with homogeneous Ru(III) for phenol degradation via PI activation at initial pH = 4, 7 and 10. Moreover, the Ru(III)/TiO2-PI system showed high selectivity for degradation of electron-rich organic contaminants. In comparison, benzoic acid and ibuprofen were hardly oxidized in the system. Scavenging tests, H218O-isotope labeled methyl phenyl sulfoxide (PMSO) probe experiments, X-ray absorption near-edge structurespectra and Electron Spin Resonance analysis confirm formation of Ru(V) = O species as dominant oxidant in the process with little involvement of IO3, OH and O2−. The formed Ru(V) = O species were further confirmed to be water-soluble via analysis of Ru distribution between aqueous solution and TiO2surface. They can be reduced to Ru(III) species by reacting with organics, realizing the catalytic cycle of Ru(III) → Ru(V) = O → Ru(III) and self-recycle of Ru(III) onto TiO2surface. In addition, PI was decomposed in stoichiometry into IO3–without generation of undesired iodine species (i.e., HOI and I2). This study advances understandings of PI activation mechanism by heterogeneous Ru(III) catalysts, and also provides a promising oxidation technology for wastewater purification.

Cobalt cross-linked ordered mesoporous carbon as peroxymonosulfate activator for sulfamethoxazole degradation

Ordered mesoporous carbons (OMCs) functionalized with catalytically-active metals have many potential applications in sulfate radical-based advanced oxidation processes for degrading antibiotics. Cobalt cross-linked ordered mesoporous carbon materials (OMC-Co-Tx) were synthesized through evaporation-induced self-assembly, calcinated at (600 to 800) oC. The OMC-Co-Tx materials were then employed as peroxymonosulfate (PMS) activators for removal of sulfamethoxazole (SMX) from aqueous solutions. OMC-Co-T800 prepared by calcination at 800 °C had a large specific surface area (449 m2/g), uniform pore structure (∼4.5 nm) and showed the best performance for activation of PMS. With a dosage of 0.1 g/L OMC-Co-T800 and 0.4 g/L PMS, the functionalized OMC material allowed SMX (10 mg/L) removal of up to 99% in 30 min. The increase of calcination temperature promoted the reduction of cobalt in OMC materials and increased the defects in their structure, resulting in better catalyst behavior. Quenching experiments and electron paramagnetic resonance analyses showed that reactive species of sulfamethoxazole degradation involved in the OMC-T800/PMS system were SO4•−, OH, O2•− and 1O2. HPLC-MS analyses of degradation intermediates formed in the OMC-Co-T800/PMS system allowed elucidation of four transformation pathways for SMX degradation.

Insights into the protonation state and spin structure for the g = 2 multiline electron paramagnetic resonance signal of the oxygen-evolving complex.

In photosystem II (PSII), one-electron oxidation of the most stable oxidation state of the Mn4CaO5 cluster (S1) leads to formation of two distinct states, the open-cubane S2 conformation [Mn1(III)Mn2(IV)Mn3(IV)Mn4(IV)] with low spin and the closed-cubane S2 conformation [Mn1(IV)Mn2(IV)Mn3(IV)Mn4(III)] with high spin. In electron paramagnetic resonance (EPR) spectroscopy, the open-cubane S2 conformation exhibits a g = 2 multiline signal. However, its protonation state remains unclear. Here, we investigated the protonation state of the open-cubane S2 conformation by calculating exchange couplings in the presence of the PSII protein environment and simulating the pulsed electron-electron double resonance (PELDOR). When a ligand water molecule, which forms an H-bond with D1-Asp61 (W1), is deprotonated at dangling Mn4(IV), the first-exited energy (34 cm-1) in manifold spin excited states aligns with the observed value in temperature-dependent pulsed EPR analyses, and the PELDOR signal is best reproduced. Consequently, the g = 2 multiline signal observed in EPR corresponds to the open-cubane S2 conformation with the deprotonated W1 (OH-).

Polypyrrole-decorated ZnO/g-C3N4 S-scheme photocatalyst for rhodamine B dye degradation: Mechanism and antibacterial activity

Polypyrrole (PPy) and graphitic carbon nitride (g-C3N4) nanoparticles are added to the surface of ZnO nanorods to successfully produce a Step-scheme (S-scheme) photocatalytic system known as g-C3N4/PPy/ZnO (GPZ) by a multistep process: hydrothermal and calcination processes, followed by polymerization. During the formation of the heterojunction, the oxygen vacancy (OV) on ZnO promotes effective separation and increases the redox power of the photogenerated excitons via the built-in internal electric field of S-scheme pathways between g-C3N4 and ZnO. The successful construction of the S-scheme heterojunction was substantiated through X-ray photoelectron spectroscopy, experimental calculations, radical trapping experiment, and liquid electron spin resonance (ESR) characterization, whereas the existence of OVs was well confirmed by ESR analysis. Meanwhile, the PPy served as a supporter, and the polaron and bipolaron species of PPy acted as electron and hole acceptors, respectively, which further enhances the charge-carrier transmission and separation in the ternary GPZ photocatalyst. The photocatalytic activity of the PPy-designed ternary photocatalyst g-C3N4/PPy/ZnO is outstanding and is greater than that of other samples like g-C3N4, ZnO, and ZnO/g-C3N4 and remove 99.0% of RhB (50 mg/L) in 60 min. RhB could be degraded most effectively by GPZ-0.75 photocatalysis at a pH of 7, and 1.0 g/L of the photocatalyst was the ideal concentration. Gram-positive (G + ve) and Gram-negative (G-ve) microorganisms were used as test subjects to determine the antibacterial effectiveness of the photocatalysts using the good diffusion approach. Ternary g-C3N4/PPy/ZnO heterostructure outperformed its competitors in terms of antibacterial activity. Additionally, after five cycles, the as-synthesized photocatalyst showed superb stability. By using a photocatalyst with a superior utilization efficiency of visible light energy, this paper offers a clearly promising, highly effective, and simple method to destroy exceedingly harmful and renowned contaminants.

Balancing thermal conductivity and strength of hot-pressed AlN ceramics via pre-sintering and annealing process

The heat dissipation requirements of the new generation of semiconductors are placing higher demands on the overall performance of aluminum nitride (AlN) ceramics. This has led to an increasing emphasis on AlN ceramics that combine thermal conductivity and strength. AlN ceramics are often strengthened by hot-press sintering, but their thermal conductivity is typically modest. In this study, pre-sintering and annealing processes are introduced to optimize the thermal conductivity of hot-pressed AlN ceramics to avoid the detrimental effects of oxygen impurities in the AlN lattice. The effect of the oxide layer on the surface of commercial AlN particles is investigated, including density, phase composition, microstructure, and fracture behavior. The effect of annealing on the improvement of thermal conductivity and flexural strength is also verified. Electron paramagnetic resonance (EPR) analysis is performed to examine the concentration of intercrystalline defects under various conditions. Finally, AlN ceramics with a thermal conductivity of 204 W m−1 K−1 and a flexural strength of 376 MPa are obtained.

First insights into 6PPD-quinone formation from 6PPD photodegradation in water environment

p-Phenylenediamines (PPDs), an important type of rubber antioxidants, have received little study on their environmental fate, particularly for their vital photodegradation process in water environment. Accordingly, N-(1,3-dimethylbutyl)-N′-phenyl-1,4-phenylenediamine (6PPD), as a representative of PPDs, was investigated experimentally and theoretically for its photodegradation in water. Rapid photodegradation occurred when 6PPD was exposed to illumination especially UV region irradiation. Under acidic conditions, the photodegradation of 6PPD accelerated mainly due to the increased absorption of long wavelength irradiation by ionized 6PPD. Nine photodegradation products (e.g., 6PPD-quinone (6PPDQ)) of 6PPD were identified by an ultra-performance liquid chromatography QTOF mass spectrometry. Molar yields of photoproducts such as 6PPDQ, aniline, 4-aminodiphenylamine, and 4-hydroxydiphenylamine were 0.03 ± 0.00, 0.10 ± 0.01, 0.03 ± 0.02, and 0.08 ± 0.01, respectively. Mechanisms involved in 6PPD photodegradation include photoexcitation, direct photolysis, self-sensitized photodegradation, and 1O2 oxidation, as demonstrated by electron paramagnetic resonance (EPR) analysis, scavenging experiments, and the time-dependent density functional theory (TD-DFT). Notably, the toxicity of the reaction solution formed during the photodegradation of 6PPD was increased by the formation of highly toxic products (e.g., 6PPDQ). This study provides the first explanation for photodegradation mechanisms of 6PPD and confirms the pathway of 6PPDQ produced by the photoreaction in water environment.

Activation behavior of Cu0/FeS/N-graphene derived from waste soybean residue for peroxymonosulfate: Performance and mechanism

Nitrogen-enriched graphene grown on zero valent copper (Cu0) and loaded with iron sulfide (FeS) was prepared through a pyrolysis-liquid phase exfoliation process using waste soybean residue as the precursor biomass. Graphene-based catalyst (GBC) exhibits exceptional proficiency as a peroxymonosulfate activator, displaying a remarkable removal surpassing 90% of total petroleum hydrocarbons (TPHs) in 180 min. Reactive oxygen species were identified through masking experiments and electron paramagnetic resonance analysis in the Cu0/FeS/BC-900/PMS system. S(II) was the source of power for the conversion of Fe(III) to Fe(II), and it was also the reason for the continuous generation of SO4•− in the system. Density functional theory calculations revealed the active sites for adsorption and reaction. The presence of SO4•−, O2•−, and 1O2 species was attributed to the elongation of S–O and O–O bonds, as well as enhancement of electrons in sulfur and sp2 hybrid carbon atoms, respectively. The degradation of TPHs was ascribed to various radical and non-radical pathways of ROSs, with SO4•− serving as the primary oxidizing species. It was fascinating that the Cu0/FeS/BC-900/PMS system exhibited good resistance to inorganic anions and surfactants, and the treatment effect on real oilfield produced wastewater was satisfactory.

Perborate accelerated copper-immobilized carbon nanofibers activating peroxymonosulfate process for sulfadiazine degradation: Performance and mechanisms understanding

In this work, perborate (BO3−) was applied to promote the degradation of sulfadiazine (SDZ) in copper-immobilized carbon nanofibers (Cu-CNF-x) activated peroxymonosulfate (PMS) system. Results showed that in BO3−/Cu-CNF-3/PMS ternary system, 100% of SDZ (40 μM) could be efficiently eliminated in 5 min with 0.1 g/L Cu-CNF-3, 1 mM BO3− and 1 mM PMS; while Cu-CNF-3/PMS and BO3−/PMS systems only achieved 58.4% and 47.3% degradation in 30 min. In initial pH range of 5.0–9.0, the ternary system removed over 92.6% of SDZ, and the treated solution pH maintained neutral, effectively relieving the water acidification introduced by PMS. Electron paramagnetic resonance analysis and radical scavenger tests evidenced the production of SO4−•, •OH, 1O2 and H2O2BO•O•−. Mechanisms analysis proposed the activation process as follows: initially, BO3− promptly activated PMS to generate H2O2BO•O•− via electrophilic substitution reaction, and H2O2 was produced due to the decomposition of BO3−; thereafter, PMS was activated by Cu-CNF-x to yield SO4−•, •OH and 1O2; the obtained H2O2 was then utilized by Cu-CNF-x to produce •OH and 1O2 as well. Density functional theory (DFT) calculations showed that the adsorption energy (Ead) between PMS and Cu-CNF-x was 0.43 eV. BO3− greatly increased the Ead of PMS on Cu-CNF-x by ten times to 4.75 eV, which extremely promoted the PMS activation. This work provided a novel strategy of BO3−/Cu-CNF-3/PMS for the efficient degradation of refractory organic pollutants, and managed to understand the synergistic role of BO3− to PMS based heterogeneous catalytic processes.

Manganese-nitrogen co-doped biochar (MnN@BC) as particle electrode for three-dimensional (3D) electro-activation of peroxydisulfate: Active sites enhanced radical/non-radical oxidation

A novel manganese-nitrogen co-doped biochar (MnN@BC) was synthesized and used as particle electrodes in three-dimensional (3D) electro-activation of peroxydisulfate (PDS) for the degradation of refractory organic pollutants. All the spectroscopy (EDS, XRD, XPS, FTIR, and Raman) results indicated that Mn-N nanoclusters were successfully deposited and embedded in BC. The material appeared graphitized structure with more defects after Mn-N doping. MnN@BC in 3D electro-activation of PDS (E/MnN@BC/PDS) exhibited excellent performance in carbamazepine (CBZ) removal, with removal efficiency and degradation rates of 96.84% and 0.0582 min-1, respectively. Besides, MnN@BC was favorable for adsorption, electron transfer, and reactive oxidizing species (ROS) formation. MnN@BC had good recyclability in the E/MnN@BC/PDS system by the recycled experiments and characterization. Furthermore, quenching experiments, probe experiments, and electron paramagnetic resonance (EPR) analyses suggested that •OH and 1O2 were the main ROS in the E/MnN@BC/PDS system, and the non-radical oxidation take a key part. In addition, this system achieved excellent CBZ degradation under wide pH range of 3–11, had good tolerance to natural organic matter and inorganic ions, and was efficient to various water matrices and other refractory organic pollutants. These findings provided new insights into particle electrode design and mechanisms enhancement in electro-activated PDS systems.

Unveiling singlet oxygen spin trapping in catalytic oxidation processes using in situ kinetic EPR analysis

Singlet oxygen (1O2) plays a pivotal role in numerous catalytic oxidation processes utilized in water purification and chemical synthesis. The spin-trapping method based on electron paramagnetic resonance (EPR) analysis is commonly employed for 1O2 detection. However, it is often limited to time-independent acquisition. Recent studies have raised questions about the reliability of the 1O2 trapper, 2,2,6,6-tetramethylpiperidine (TEMP), in various systems. In this study, we introduce a comprehensive, kinetic examination to monitor the spin-trapping process in EPR analysis. The EPR intensity of the trapping product was used as a quantitative measurement to evaluate the concentration of 1O2 in aqueous systems. This in situ kinetic study was successfully applied to a classical photocatalytic system with exceptional accuracy. Furthermore, we demonstrated the feasibility of our approach in more intricate 1O2-driven catalytic oxidation processes for water decontamination and elucidated the molecular mechanism of direct TEMP oxidation. This method can avoid the false-positive results associated with the conventional 2D 1O2 detection techniques, and provide insights into the reaction mechanisms in 1O2-dominated catalytic oxidation processes. This work underscores the necessity of kinetic studies for spin-trapping EPR analysis, presenting an avenue for a comprehensive exploration of the mechanisms governing catalytic oxidation processes.

The effect of radiation on grape seeds: ESR and microbiological analysis

In this work, pulverized grape seeds were irradiated with varying doses of 60Co gamma radiation, and the effect of radiation for each dosage value was determined using Electron Spin Resonance (ESR) spectroscopy and microbiological analysis. Through dose-response and kinetic investigations, the dose dependence and stability of the radiation induced cellulose-like radicals were determined, respectively. The effect of irradiation on aerobic bacteria was demonstrated for the first time by microbiological analysis and the inactivating dose value was identified. The obtained findings are beneficial for irradiated food detection investigations.

Preparation of pyrolysis products by catalytic pyrolysis of poplar: Application of biochar in antibiotic wastewater treatment

Poplar waste is acted as feedstock to produce renewable biofuel and green chemical by catalytic pyrolysis using ferric nitrate and zinc chloride as additive. The additive contributes to the generation of furfural in bio-oil. Additive promotes the generation of H2 and inhibits the generation of CO with bio-gas heating value of 12.16 MJ (Nm3)−1. Biochar exists ZnO and Fe3O4 with large surface area, which could be used as absorbent and photocatalyst for tetracycline and ciprofloxacin removal. The tetracycline and ciprofloxacin adsorption amount of biochar are 316.41 and 255.23 mg g−1 respectively. While the photocatalytic degradation removal of the tetracycline and ciprofloxacin is close to 100%. The adsorption and photocatalytic degradation mechanism are investigate and analyzed using the density functional theory and electron paramagnetic resonance analysis. Biochar can be quickly recycled and regenerated after use. Besides, biochar can be used in lithium ion battery industry for energy storage, which specific capacity is 535 mAh g−1.

Novel double Z-scheme g-C3N5/BiFeO3/ZnIn2S4 heterojunction system with enhanced visible-light-induced photo-Fenton activity towards sulfamethoxazole degradation

In this study, a novel double Z-scheme g-C3N5/BiFeO3/ZnIn2S4 (CBZ) heterojunction nanocomposite was synthesized using a simple wet chemical process. The crystal structure, morphology, optical, and chemical compositional behaviors of the prepared nanocomposite were characterized using various techniques. The Vis/H2O2/CBZ-40% system could remove 97% sulfamethoxazole (SMX) pollutant for 60 min. The significantly enriched performance was attributed to the greater Fe2+/Fe3+ conversion efficiency by decomposing H2O2, and the synergistic coupling of the CBZ-40% in ternary heterojunction provided a better charge transfer pathway for the initiation of photo-Fenton reactions. In addition, the trapping experiments and electron spin resonance analysis identified active reactive oxygen species such as •OH, •O2−, and 1O2. The possible degradation mechanism of SMX and their intermediate products were proposed based on the above experimental analysis. Moreover, this results showed the suitability of using Vis/H2O2/CBZ-40% system, providing excellent reusability and an admissible platform for wastewater remediation via double Z-scheme heterojunction.

The overlooked role of Cr(VI) in micropollutant degradation under solar light irradiation

Hexavalent chromium (Cr(VI)) is ubiquitous in natural environments, whereas its role in the transformation of coexisting contaminants may have been overlooked. In this work, it was reported for the first time that the irradiation of Cr(VI) by solar light (solar light/Cr(VI) system) could effectively degrade various micropollutants with different structures. The removal efficiency of selected micropollutants was increased by 13.3–64.8% by the solar light/Cr(VI) system compared to that by direct solar photolysis. Meanwhile, the oxidation rates were enhanced by 2.2–21.5 folds, while they were negligible by Cr(VI) oxidation alone. Experiments by specific scavengers, probe compounds, fluorescence absorbance, and electron spin resonance analysis demonstrated that hydroxyl radical (•OH) was the major reactive species in the solar light/Cr(VI) system. Further experiments showed that the generation of •OH was closely related to the intermediate Cr(V) generated from Cr(VI) reduction, and Cr(V) could be re-oxidized back to Cr(VI). Increasing solution pH negatively affected model micropollutant (carbamazepine (CBZ)) degradation by the solar light/Cr(VI) system, mainly due to the decreased quantum yield of •OH at higher pH. Coexisting sulfate ions showed negligible effect on CBZ degradation in the solar light/Cr(VI) system, while the presence of bicarbonate, chloride, and humic acid inhibited CBZ degradation to varying degrees, owing to their diverse scavenging effects on •OH. Furthermore, moderate CBZ degradation was also achieved by natural solar light photolysis of Cr(VI). This study demonstrated the pivotal role of Cr(VI) in the transformation of micropollutants under solar irradiation, which advances the understanding of the fate of micropollutants in natural environments.