Electron Paramagnetic Resonance Results Research Articles

Cu2(OH)3NO3/γ-Al2O3 catalyzes Fenton-like oxidation for the advanced treatment of effluent organic matter (EfOM) in fermentation pharmaceutical wastewater: The synergy of Cu2(OH)3NO3 and γ-Al2O3

The secondary effluent of fermentation pharmaceutical wastewater exhibits high chromaticity, elevated salinity, and abundant refractory effluent organic matter (EfOM), presenting significant treatment challenges and environmental threats. Herein, Cu2(OH)3NO3/γ-Al2O3 was fabricated through ultrasound-assisted impregnation and calcination to catalyze the Fenton-like oxidation for degrading organic pollutants in this secondary effluent. Under neutral conditions, with 400.00 mg/L H2O2, 8 g/L catalyst, and at 30 ℃, the EfOM and CODCr removal efficiencies can reach 96.90 % and 51.56 %, respectively. The Cu2(OH)3NO3/γ-Al2O3 catalyst possesses ideal reusability, maintaining CODCr, chromaticity, and EfOM removal efficiencies at 44.44 %-64.59 %, 85.45 %-93.45 %, and 61.00 %-95.00 % over 220 h in a continuous-flow catalytic oxidation system operated at room temperatures (15–25 ℃). Electron paramagnetic resonance results and density functional theory calculations indicate that •OOH may be the predominant reactive oxygen species, facilitated by the easier elongation of the OH bond in H2O2 compared to the OO bond. The adjusted electronic structure endows Cu2(OH)3NO3/γ-Al2O3 composite sites with superior catalytic selectivity for H2O2 activation compared to Cu2(OH)3NO3 single crystal sites, with γ-Al2O3 additionally facilitating H2O2 activation through electron donation. This research highlights the efficacy of Cu2(OH)3NO3/γ-Al2O3 in the advanced treatment of complex industrial wastewater, elucidating its catalytic mechanisms and potential applications.

Uranium mineralization in the Thrace Basin, NW Türkiye: Evidence from radiation-induced defects in detrital quartz and synchrotron XRF/XANES analysis

The Paleogene-Neogene Thrace Basin in northwestern Türkiye has long been known to host economic gas and oil resources and has recently been reported to potentially host sandstone-type uranium deposits in the Oligocene Süloğlu Formation. The latter discovery raises questions about the source and deposition mechanism of uranium mineralization in the basin. This contribution reports on the results of a detailed electron paramagnetic resonance (EPR) spectroscopic study of detrital quartz from four sandstone and one mudstone samples in the Süloğlu Formation and documents the distribution and speciation of uranium using combined microbeam synchrotron X-ray fluorescence maps (μsXRF) and microbeam X-ray near edge structure spectroscopy (μsXANES). The EPR spectra of quartz separates are characterized by the presence of diagnostic radiation-induced defects (i.e., silicon-vacancy hole centers H′3, H′4, and H′7 with gmax = 2.049, 2.034, and 2.018, respectively, and the oxygen-vacancy electron center E′1), formed by the bombardment of alpha particles emitted from uranium, thorium, and their unstable progenies. Moreover, notable decreases in the intensity of silicon-vacancy hole centers in the EPR spectra of quartz separates after partial dissolution with hydrofluoric acid, provide compelling evidence for the circulation of uranium-bearing fluids in the Thrace Basin. The μsXRF and μsXANES data reveal the occurrences of mixed U6+ and U4+ species in hematite partially replacing pyrite aggregates but dominantly U4+ in disseminated pyrite and illite in sandstones of the Süloğlu Formation. These results provide new insights into uranium transport, reduction, and deposition mechanisms, with important implications for better understanding sandstone-type uranium deposits in general and further exploration in the Thrace Basin.

Nanoconfinement-induced high activity of ZIF-8 derived atomic Zn-N-C materials for fenton-like reactions

Atomic Zn-N-C materials are synthesized by direct carbonization of ZIF-8, which maintains the rhombic dodecahedron morphology (RDM) with abundant nanopores. Zn-N-C-RDM shows enhanced catalytic activity with bisphenol A (BPA) as model pollutant and peroxydisulfate (PDS) as oxidant. Molecular dynamic (MD) calculations show that mean square displacement (MSD) of PDS, BPA, and H2O molecules in the nanotunnels decreases obviously with smaller pore size. Due to the confinement, the BPA (di = 1.0 nm) and PDS (di = 0.5 nm) can easily enter and confined in the cavities of Zn-N-C-RDM. PDS can be therefore activated more easily to degrade BPA due to their faster diffusion and shorter transfer routes. > 97 % degradation of BPA can therefore be achieved by Zn-N-C-RDM within 20 min. Quenching experiments, electron paramagnetic resonance (EPR) and open circuit potential (OCP) results indicate that O2•− radical dominate the degradation. According to the density functional theory (DFT) results, the binding sites of Zn-pyridinic N are the main active sites. This work provides new insights for improving activity in Fenton-like reactions in the field of environmental remediation.

Synthesis of coal slime-based catalytic material for peroxymonosulfate activation through molten salt thermal treatment

Coal slime-based peroxymonosulfate (PMS) catalytic materials were synthesized utilizing coal slime (CS) as raw material under the N2 atmosphere in this study. Raw and calcined coal slime were systematically characterized concerning morphologies, pore structures, chemical bonds, phase constituents, and defect density. Results show that after being calcinated with FeCl2∙4H2O at 750 °C, the specific surface area increased by nearly 21.0 times higher than that of CS. The addition of FeCl2∙4H2O has certain effect on the chemical bonds of calcined coal slime, i.e. the Fe elements can be fixed by the silicon aluminum skeleton with sekaninaite (Fe2Al4Si5O18) and aluminum iron silicon (Al0.5Fe3Si0.5, above 650 °C) generation, and the ID/IG values increase to 2.96 for CS-FeCl2-750. In addition, the degradation percentage of phenol by using CS-FeCl2 can achieve 100% in 25 min under optimized conditions. Furthermore, 1O2 plays a major role in phenol degradation, followed by •OH and SO4•− in the CS-FeCl2/PMS system from the quenching experiments and electron paramagnetic resonance results. Overall, the novel CS-FeCl2 material displays good application prospects in the field of effluent treatment, with efficient utilization of carbonaceous and silicon aluminum skeleton in coal slime.

A novel NiFe-LDH/AC three-dimensional particle electrode system and its application for degradation of N-nitrosamines: Condition optimization and degradation mechanism

A green and sustainable three-dimensional particle electrodes system with nickel-iron layered double hydroxide mixing activated carbon particles (NiFe-LDH/AC) as particle electrodes is used in this work. Its employment in degradation of N-Nitrosodiethylamine (NDEA), A type of nitrosamines disinfection byproducts (NAs) widely present in water bodies, exhibiting significant degradation efficiency at close to neutral pH. Response surface methodology (RSM) is used to analyze the interaction effects and predict optimal conditions of four operating parameters (influent water flow, electrolyte concentration, current density and initial concentration) on the NDEA degradation efficiency. Calculated coefficients of determination (R2) are higher than 0.997 for all responses according to analysis of variance. At optimum conditions, a maximum degradation efficiency of 71.88% is achieved for NDEA. The results of electron paramagnetic resonance (EPR) and free radical quenching experiments indicate that the degradation of NDEA in the 3D AER system is dominated by •OH. Furthermore, based on the recognition of main reaction intermediates by GC-MS and density functional theory (DFT), possible degradation pathway is proposed and toxicological evaluation of degradation products is made. Our research provides a promising alternative method for the efficient and environmentally friendly removal of NAs from water.

Study on the Inhibition Characteristics of Coal Spontaneous Combustion by Silica Gel Foam.

The spontaneous combustion of residual coal in abandoned mining areas severely affects the safe and efficient extraction of coal, employee occupational health, and regional environmental ecology. A technical measure for preventing and controlling the spontaneous combustion of residual coal involves injecting antispontaneous combustion materials into abandoned areas. In this study, the composition, preparation, and mechanism of action of silica gel foam, a material used to suppress spontaneous combustion during coal mining, were investigated to improve the performance of materials designed to prevent spontaneous combustion in abandoned areas. The inhibitory efficiency improved, and the mechanical strength and stability of the foam liquid film increased upon adding modified antioxidants and nanosilica particles to the gel foam. Macro performance tests, microstructural characterization, and chemical inhibition mechanism analyses verified the efficacy of silica gel foam for suppressing spontaneous combustion. The air leakage resistance of the silica gel foam effectively increased the air leakage resistance of the coal samples at different pressures. New radicals formed during the spontaneous combustion of coal comprising different inhibitors, as indicated by the g-factor results of electron paramagnetic resonance (EPR) spectroscopy analysis; the formation of radicals initially decreased and then increased when the inhibitor material changed. The concentration of free radicals decreased markedly during the spontaneous combustion process of both raw and inhibited coal samples at low oxidation temperatures (∼60-100 °C), indicating a marked inhibitory effect.

MXene-supported MIL-88A(Fe) as persulfate activator for removal of tetracycline.

The poor conductivity, poor stability, and agglomeration of iron-based metal organic framework MIL-88A(Fe) limit its application as persulfate (PS) activator in water purification. Herein, MXene-supported MIL-88A(Fe) composites (M88A/MX) were synthesized to enhance its adsorption and catalytic capability for tetracycline (TC) removal. Scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR), and X-ray photoelectron spectroscopy (XPS) were used to characterize prepared materials, confirming the successful attachment of MIL-88A(Fe) to the surface of MXene. M88A/MX-0.2 composites, prepared with 0.2g MXene addition, exhibit optimal degradation efficiency, reaching 98% under conditions of 0.2g/L M88A/MX-0.2, 1.0mM PS, 20ppm TC, and pH 5. The degradation rate constants of M88A/MX-0.2 were 0.03217min-1, which was much higher than that of MIL-88A(Fe) (0.00159min-1) and MXene (0.00626min-1). The removal effects of reaction parameters, such as dosage of M88A/MX-0.2 and PS; initial solution pH; and the presence of the common co-existing constituents (humic acid and the inorganic anions) were investigated in detail. Additionally, the reuse of M88A/MX-0.2 showed that the composites had good cycling stability by recurrent experiments. The results of electron paramagnetic resonance (EPR) and quenching experiments indicated that ·OH, ·SO4-, and ·O2- were involved in the M88A/MX-0.2/PS system where persulfate oxidation process was activated with prepared M88A/MX-0.2. In addition, the intermediates of photocatalytic degradation were determined by HPLC-MS, and the possible degradation pathways of the target molecules were inferred. This study offered a new avenue for sulfate-based degradation of Fe-based metal organic framework.

Highly Effective Fe-Doped Nano Titanium Oxide for Removal of Acetamiprid and Atrazine under Simulated Sunlight Irradiation

Pesticides are widely detected in large quantities in the environment, posing an ecological threat to the human body and ecology. Semiconductor nanomaterials such as nano-titania (nTiO2) have strong photocatalytic degradation efficiency for pollutants. However, the wide bandgap and limited light absorption range inhibit nano-titania’s practical application. Therefore, nTiO2 was modified by Fe3+ doping using the microwave hydrothermal method to improve its photocatalytic performance in this study. Fe-nTiO2 doped with a 1.0% mass ratio was used due to its high photocatalytic performance. Its maximum degradation efficiencies for ACE and ATZ under a 20 W xenon lamp were 88% and 88.5%, respectively. It was found that Fe3+ doping modification distorted the spatial morphology of nTiO2 and shortened the bandgap to facilitate the photocatalytic reaction. The electron paramagnetic resonance results showed that the reactive radicals (1O2, ·OH) produced by photogenerated electrons (e−) and holes (h+) of Fe-nTiO2 were the main active species in the degradation of ACE and ATZ. Additionally, the application of Fe-nTiO2 significantly enhanced the growth of lettuce under sunlight; the degradation efficiencies of ACE and ATZ in lettuce were 98.5% and 100%, respectively. This work provides new insights into the removal of organic contaminants by photocatalysts under sunlight in agriculture.

Evaluation of gamma irradiation effects on antioxidant capacity of propolis

The irradiation effects on antioxidant potential and on content of phenolic compounds of propolis ethanoic extracts were studied. It was found out that gamma treatment of samples with 2 and 10 kGy had a weak decreasing effect on the total phenolic content (TPC), while no change was observed in the propolis irradiated with 5 kGy. The antiradical activity of extracts was assessed by the DPPH free radical scavenging activity evaluated by Electron Paramagnetic Resonance (EPR) spectroscopy. The EPR results were in agreement with TPC. Some main phenolic compounds of the studied non-irradiated and irradiated samples were identified and compared by ultra-high performance liquid chromatography (UHPLC).

Oxygen vacancy-rich cuprous oxide microspheres exhibit strong absorption and high oxidative energy level for deep photodegradation of tetracycline

In this study, a Cu2O microsphere (WY1) was hydrothermal synthesized by employing a CTAB-cocoylsarcosine sodium composite micellar. WY1 has an unifirm hollow spherical structure formed by agglomeration of nanoparticles, and the results of X-ray photoelectron spectroscopy and electron paramagnetic resonance indicate that WY1 contains significantly increased oxygen vacancies. The degradation efficiency of WY1 for 40 mg L−1 TC reached 93.26% after 60 min visible-light irradiation, which was 2.04 times higher than that of the product prepared without soft template (WNT). Especially, 81.67% residual rate of total organic carbon in the degradation of TC over WY1 was 17.83 times higher than that of WNT (4.58%). The spectral and electrochemical data reveal that the position of valence band of WY1 was exceeded the H2O/·OH potential, and the ·OH species rarely played a key role in the photocatalytic degradation of tetracycline by cuprous oxide. In addition, the ·O2− species were generated by forming the electron transfer pathway with aid of oxygen vacancy-mediated trap, acting as another major active species, which followed a deep photodegradation mechanism of hydroxyl and superoxide radicals dual activities. The spatial agglomeration of cuprous oxide nanoparticles provides a new process for enhancing interfacial energy levels and inhibiting photocorrosion, which cater the antibiotic remediation.

Defect engineered N-S codoped TiO2 nanoparticles for photocatalytic and optical limiting applications: Experimental and DFT insights

N-S codoped TiO2 nanoparticles (NPs) were synthesized using a sol–gel cum hydrothermal approach, with ammonium sulfate as the nitrogen and sulfur source compound. The calcination temperature was varied from 500 to 700 °C. The pristine samples exhibited a mixed phase of anatase and brookite, while the doped samples exhibited only the anatase phase, as confirmed by X-ray diffraction (XRD) analysis. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of N-H vibrations and S-O bidentate complexation with Ti4+ ions. Electron paramagnetic resonance (EPR) revealed the presence of Ti3+ signals, confirming the creation of oxygen defects in the doped samples. The absorption and emission properties of the samples were investigated using ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy. Vibrating sample magnetometry (VSM) analysis confirms the room-temperature ferromagnetic behavior of the N-S doped TiO2, which was attributed to the presence of oxygen vacancies, as evidenced by the EPR and PL results. The N-S doped TiO2 samples demonstrated superior photocatalytic degradation of Rhodamine B (RhB), Methylene Blue (MB), and Congo Red (CR) dyes under visible light illumination compared to the pristine TiO2. This enhanced performance was attributed to the presence of N and S dopants in TiO2, which create new energy levels within the band structure of TiO2, allowing for efficient absorption of visible light and subsequent generation of reactive species for dye degradation. N-S doping modifies the electronic structure of TiO2, enhancing two-photon absorption (TPA). This increased TPA efficiency suggests promising applications in optical devices, such as laser protection systems and optical limiters. Density Functional Theory (DFT) investigation also confirms that the presence of oxygen vacancies generates energy states below the conduction band. This, in turn, benefits the absorption of more visible light during photocatalytic activities and leads to a notable nonlinear absorption in optical limiting. Overall, the N-S doping strategy significantly improves the photocatalytic and optical limiting performance of TiO2 NPs, making them promising candidates for a wide range of applications.

Synergistic mechanisms between chlorine-mediated electrochemical advanced oxidation and ultraviolet light for ammonia removal

The combination of chlorine-mediated electrochemical advanced oxidation (Cl-EAO) and ultraviolet (UV) radiation (UV-E/Cl) can efficiently remove ammonia from wastewater. However, the synergistic mechanisms between Cl-EAO and UV need to be explored in more detail. Thus, in this study, the ammonia oxidation performance of Cl-EAO and UV-E/Cl systems were compared, while the synergistic mechanisms were identified by the performance of UV/chlorine oxidation (UV–ClO) system and the results of electron paramagnetic resonance (EPR) analysis, free radical inhibition assays, and determination of steady-state concentration of free radicals. It was found that, compared with the Cl-EAO system, UV increased the ammonia removal rate by 42.85% and reduced the active chlorine concentration (56.64%) and nitrate yield (53.61%). In the Cl-EAO, and UV-E/Cl systems, Cl• were detected, and the free radical inhibition assays and determination of steady-state concentration of free radicals suggested that UV increased the concentration of Cl• by 51.47%, resulting in Cl• becoming the major contributor to ammonia oxidation in the UV-E/Cl system. Besides, UV also increase the concentrations of HO• and Cl2•-, which further promoted the organic matter removal in the real domestic wastewater. This study also discussed the ammonia oxidation performance of the UV-E/Cl system in real domestic wastewater, even with the presence of significant levels of organic and inorganic anions in the wastewater, UV increased the ammonia oxidation by 21.95%. The results of this study thus clarify the mechanisms and potential applications of UV-E/Cl technology.

Construction of Co-doped Fe2O3/carbonized melamine foam heterogeneous catalyst for enhanced degradation of organic pollutants through peroxymonosulfate activation

Co-doped Fe2O3/carbonized melamine foam heterogeneous catalyst (CMF/Co-Fe2O3) was prepared by hydrothermal method. Rhodamine B (RhB) degradation was employed as a model test for evaluating peroxymonosulfate (PMS) activation. The degradation efficiency of RhB can reach 97 % in the catalyst dosage (50 mg/L), PMS concentration (100 mg/L), pH = 7 and RhB initial concentration (10 mg/L) after 60 min reaction. The reaction rate constant is 10 times higher than that of CMF/Fe2O3 and the activation ability of PMS is greatly improved. The degradation efficiency of RhB can be inhibited by increasing the initial mass concentration of RhB and pH value. The effect of temperature on the degradation rate of RhB conforms to the Arrhenius model, and the degradation process is a surface reaction controlled process. The results of free radical capture experiments and electron paramagnetic resonance (EPR) experiments showed that SO4¯ was the main active free radical for RhB degradation. After four cycles, the degradation efficiency of RhB still maintains 80 % with CMF/10 %Co-Fe2O3 catalyst. The heterogeneous catalyst exhibited potential application in the field of degradation of dye wastewater due to its excellent cycling stability.

A magnetically reusable Ce-MOF/GO/Fe3O4 composite for effective photocatalytic degradation of chlortetracycline.

Herein, we report a novel 1/GO/Fe3O4 photocatalyst, comprising Ce(BTB)(H2O) (MOF-1, H3BTB = 1,3,5-benzenetrisbenzoic acid), graphene oxide (GO), and iron oxide (Fe3O4) for photocatalytic degradation of chlortetracycline (CTC). This design enables the effective transfer of electrons from the MOF to GO, thereby reducing the photoelectron-hole recombination rate. Therefore, the optimized 1/GO/Fe3O4 photocatalyst with H2O2 shows the highest photocatalytic activity toward CTC. The kinetic constant is 5.4 times that in the system of MOF-1 and hydrogen peroxide, which usually acted as efficient electron acceptors to improve the photocatalytic performance of MOFs. More importantly, light absorption is extended from the ultraviolet to the visible region. Furthermore, 1/GO/Fe3O4 can be quickly recycled under an applied magnetic field and displays outstanding stability and reusability. According to the radical trapping experiments and electron paramagnetic resonance results, hydroxyl radicals, superoxide radicals, and holes all contribute to excellent photocatalytic activity. The possible catalytic mechanism of 1/GO/Fe3O4 is tentatively proposed. This work aims to explore the synergistic effect between metal-organic frameworks (MOFs) and GO, and provide a theoretical basis for MOF-based composites to remove antibiotic contaminants in the environment.

Investigation of α-Fe2O3 catalyst structure for efficient photocatalytic fenton oxidation removal of antibiotics: preparation, performance, and mechanism.

Currently, the surface structure modification of photocatalysts is one of the effective means of enhancing their photocatalytic efficiency. Therefore, it is critically important to gain a deeper understanding of how the surface of α-Fe2O3 photocatalysts influences catalytic activity at the nanoscale. In this work, α-Fe2O3 catalysts were prepared using the solvothermal method, and four distinct morphologies were investigated: hexagonal bipyramid (THB), cube (CB), hexagonal plate (HS), and spherical (RC). The results indicate that the hexagonal bipyramid (THB) exhibits the highest degradation activity towards tetracycline (TC), with a reaction rate constant of k = 0.0969 min-1. The apparent reaction rate constants for the cube (CB), hexagonal plate (HS), and spherical (RC) morphologies are 0.0824, 0.0726, and 0.0585 min-1, respectively. In addition, it has been observed that the enhancement of photocatalytic activity is closely related to the increase in surface area, which provides more opportunities for interactions between Fe2+ and holes. The quenching experiments and electron paramagnetic resonance (EPR) results indicate that the ˙O2, ˙OH and h+ contribute mainly to the degradation of TC in the system. This research contributes to a more comprehensive understanding of catalyst surface alterations and their impact on catalytic performance.

Spin polarization engineering on SnS2 for improving photocatalytic disinfection

With the emergence and massive spread of antibiotic-resistant bacteria, it is urgent to develop new bactericidal technologies. Photocatalytic sterilization is a technique that uses solar energy to produce reactive oxygen species to kill pathogenic bacteria, and ROS effects depends on the charge separation characteristics of photocatalysts, so the development of strategies to promote charge separation is crucial. Here, we use the strategy of introducing sulfur vacancy on SnS2, effectively improving the separation of photogenerated charge. The femtosecond transient absorption results confirm that the charge lifetime of SnS2 (Sv-SnS2) after the introduction of the sulfur vacancy is 13.33 times that of pristine SnS2. The DFT theoretical results confirm that sulfur vacancy causes spin polarization. It is easier to separate when the spin direction of the electrons and holes changes. In addition, the sulfur vacancy also expands the light absorption range and exposes the surface catalytic site. These phenomena lead to a higher ROS yield of Sv-SnS2 (confirmed by electron paramagnetic resonance results). Thus, Sv-SnS2 killed 99.99 % of E. coli and MRSA within 40 min under visible-light illumination. This efficient bactericidal performance can be attributed to improved photogenerated charge separation. This study confirms the effectiveness of sulfur vacancy strategy to improve charge separation and extend charge life, and applies it to the killing of antibiotic resistant bacteria, providing a new idea for the killing of resistant bacteria.

A hierarchical 3D hybrid CoAl-layered double hydroxide/TiO2/Ti3C2 MXene S-scheme photocatalyst with 2D/0D/2D contact interfaces for sustainable pollutant degradation

Environmental pollution, particularly that derived from waterborne antibiotics, is a rising concern because of its detrimental effects on aquatic ecosystems and human health. Hence, in this study, we present a hierarchical 3D-structured hybrid photocatalyst comprising a CoAl-layered double hydroxide (LDH), TiO2, and Ti3C2 MXene synthesized using an in situ hydrothermal method. Various characterization techniques revealed that the hybrid CoAl-LDH/TiO2/Ti3C2 photocatalyst exhibited improved optical absorption, and the tailored 2D/0D/2D contact interfaces among the constituents enhanced charge migration and minimized electron-hole recombination. The results of electron paramagnetic resonance and in situ-irradiated X-ray photoelectron spectroscopy analyses confirmed that the hybrid photocatalyst follows an S-scheme mechanism that not only promotes the separation of photoinduced electron-hole pairs but also preserves their robust redox capability. The amalgamation of the three components resulted in synergistic advantages. Consequently, the optimized CoAl-LDH/TiO2/Ti3C2 photocatalyst exhibited remarkable performance in degrading and mineralizing the antibiotic diclofenac sodium (DFS) and the dyes rhodamine B and indigo carmine, surpassing its constituents and previously reported photocatalysts. Furthermore, the hybrid retained high efficiency across multiple cycles, underscoring its potential reusability. Therefore, this study demonstrates the potential of the developed hybrid photocatalyst for sustainable water treatment, thereby fostering cleaner aqueous environments.

Amino acid promoted oxidation of atrazine by Fe3O4/persulfate

In the present study, we demonstrated that the presence of cysteine could remarkably enhance the degradation of atrazine by Fe3O4/persulfate system. The results of electron paramagnetic resonance (EPR) spectra confirmed the combination of cysteine and Fe3O4 exhibited much higher activity on activation of persulfate to generate more SO4•- and •OH than Fe3O4 alone. At pH of 3.0, SO4•- and •OH contributed to about 58.2 % and 41.8 % of atrazine removal respectively, while •OH gradually dominated the oxidation of atrazine from neutral condition to alkaline condition. The co-existing Cl− and HCO3− could quench SO4•-, resulting in the inhibition of atrazine degradation. The presence of low natural organic matters (NOM) concentration (0–2 mg L−1) could enhance the atrazine removal, and high concentration (>5 mg L−1) of NOM restrained the atrazine degradation. During the Cysteine/Fe3O4/Persulfate process, cysteine served as a complexing reagent and reductant. Through acidolysis and complexation, Fe3O4 could release dissolved and surface bound Fe2+, both of which contributed to the activation of persulfate together. Meanwhile, cysteine was not rapidly consumed due to a regeneration process, which was beneficial for maintaining Fe2+/Fe3+ cycle and constantly accelerating the activation of persulfate for atrazine degradation. The reused Fe3O4 and cysteine in the Cysteine/Fe3O4/Persulfate process exhibited high stability for the atrazine degradation after three cycles. The degradation pathway of atrazine included alkylic-oxidation, dealkylation, dechlorination-hydroxylation processes. The present study indicates the novel Cysteine/Fe3O4/Persulfate process might be a high potential for treatment of organic polluted water.

An electron paramagnetic resonance study of the electron transport in heavily Si-doped high Al content AlxGa1−xN

High Al mole fraction AlGaN is an ultrawide bandgap semiconductor with potential applications in power electronics and deep UV detectors. Although n-type material is achievable with Si-doping, the role of Si is controversial, particularly for AlxGa1−xN with x > 0.8. For this paper, AlGaN films were grown by plasma-assisted molecular beam epitaxy onto bulk AlN substrates and doped with 1018–1020 cm−3 Si. We examine electron transport in heavily Si-doped AlxGa1−xN with x ≥ 0.65 using magnetic resonance, which allows us to probe the neutral donors directly rather than the free carriers and avoids complications due to electrical contacts. Transport was studied through the temperature-dependent linewidth of the electron paramagnetic resonance (EPR) signature for the neutral donor. Analysis shows evidence of hopping conductivity in the most lightly doped samples and impurity band formation in the most heavily doped ones. The EPR results, which are consistent with Hall measurements performed on the same samples, are promising for the development of highly conducting high Al content AlGaN.

Carbonized eggshell membranes as highly active co-catalyst with Fe3+/persulfate for boosting degradation of carbamazepine by accelerating Fe3+/Fe2+ cycle

The sluggish Fe3+/Fe2+ cycle greatly limits the effectiveness of the Fe3+-induced persulfate (Fe3+/PS) system for degrading refractory organic pollutants. Coupling Fe3+/PS system with a co-catalyst is a promising strategy to solve this issue. Herein, we report a carbonized eggshell membrane (CESM) as a potential co-catalyst to efficiently drive Fe3+/PS oxidation. The promotion effect of the CESM on the Fe3+/Fe2+ cycle resulted in the improvement in the activity of the Fe3+/PS system to degrade carbamazepine (CBZ), with ∼100 % CBZ removal achieved with low doses of Fe3+ (1.0 mg/L) and PS (100 mg/L). Crucially, a pseudo-first-order rate constant of CESM/Fe3+/PS system was 18- and 28-times that of the Fe3+/PS and CESM/PS systems. Experimental and theoretical findings reveal that the phenolic –OH groups and carbon--center persistent free radicals in CESM are electron donors, while the nitrogen sites function as favorable Fe3+-adsorption sites. The electron transfer in CESM/Fe3+/PS system occurred between a CESM and an attached Fe3+, facilitating the generation of Fe2+ and thus contributing to the continuous activation of PS. The quenching and electron paramagnetic resonance results indicate that active oxygen radicals (O2•−,•OH and SO4•−) and Fe(IV) acted together to realize the efficient CBZ degradation. Moreover, this system exhibited good reusability and environmental adaptability in various real water matrices. The co-catalyst effect of CESM is expected to inspire the exploration of utilization of different waste-biomass-derived organic materials as co-catalysts in the Fe3+/PS system for water purification.