Iron Oxide Research Articles

Protein-metal interactions due to fretting corrosion at the taper junction of hip implants: an in vitro investigation using Raman spectroscopy

Modular hip implants are a clinically successful and widely used treatment for patients with arthritis. Despite ongoing retrieval studies the understanding of the fundamental physico-chemical mechanisms of friction and wear within the head-taper interface is still limited. Here, we Raman-spectroscopically analyze structural features of the biotribological material which is formed within the taper joint between Ti6Al4V and low-carbon cobalt alloy or high-nitrogen steel surfaces in in vitro gross-slip fretting corrosion tests with bovine calf serum. As a function of the fretting duration, we investigate short and long aliphatic chains and their adsorption behavior on the cobalt- and steel-type surfaces. Using the intensity and frequency shifts of the amide I and III Raman bands, we furthermore identify progressive protein folding and unfolding including the secondary structures of α-helix, β-sheet, and random-coil configuration as well as the formation of proteinaceous clusters depending on the hydrophilicity of the metallic surfaces. We additionally find a mixture of chromates and iron oxides with tryptophan and tyrosine at the worn cobalt alloy and high-nitrogen steel surfaces, respectively. Also, for long fretting duration, sp2 hybridized amorphous carbon is formed due to fretting-induced cleavage of proteins. Statement of significanceDespite efforts enhancing the biomedical tribology of hip implants, the impact of the organic environment on friction&wear at the femoral head-stem taper interface is limitedly understood. Using Raman spectroscopy we resolve structural changes within the biotribological material agglomerated at biomedical-grade metal alloys due to organo-metallic interactions during in vitro fretting corrosion tests. Adsorption of short and long aliphatic chains, progressive protein (un)folding and proteinaceous cluster formation depend to a distinguishable extent on the fretting duration and type of alloy. Chromates and iron oxides are mixed with tryptophan and tyrosine, and amorphous carbon is formed resulting from a fretting-induced cleavage of serum proteins. Such information spectroscopically gleaned from biotribological material are vital to improve the design and performance of taper junctions.

Molecular characterization on the fractionation of organic phosphorus induced by iron oxide adsorption using ESI-FT-ICR MS

The interaction between organic phosphorus (OP) and iron oxide significantly influences the phosphorus cycle in the natural environment. In shallow lakes, intense oxidation-reduction fluctuations constantly alter the existing form of iron oxides, but little is known about their impact on the adsorption and fractionation of OP molecules. In this study, electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS) was used to investigate the fractionation of OP from alkali-extracted sediment induced by crystalline goethite and amorphous ferrihydrite adsorption at a molecular scale. The results showed that ferrihydrite and goethite both exhibited high OP adsorption, and the adsorption amount decreased as the pH increased. The adsorption kinetics matched the pseudo-second-order equation. The ESI-FT-ICR MS analysis showed that 91 P-containing formulas were detected in the alkaline-extracted sediment solution. Ferrihydrite and goethite adsorbed 51 and 24 P-containing formulas, respectively, with adsorption rates of 56.0 % and 26.4 %. Ferrihydrite could adsorb more OP compounds than goethite, but no obvious molecular species selectivity was observed during the adsorption. The P-containing compounds, including unsaturated hydrocarbons-, lignin/carboxyl-rich alicyclic molecule (CRAM)-, tannin-, and carbohydrate-like molecular compounds, were more suitable for iron oxide adsorption. The double bond equivalence (DBE) is a valuable parameter that indicates OP fractionation during adsorption, and P-containing compounds with lower DBE values such as lipid- and protein-like molecular were prone to remain in the solution after adsorption. These research results provide insights into the biogeochemical cycling process of P in the natural environment.

Coupled effects of iron (hydr)oxides and clay minerals on the heterogeneous oxidation of aqueous Mn(II) and crystallization of manganese (hydr)oxides

The formation of nanominerals and mineral nanoparticles (NMMNs) has drawn broad attention due to their high reactivity and omnipresence in the environment. While the heterogeneous formation of NMMNs on surfaces of various minerals has been extensively studied, little is known about how mineral heteroaggregates influence this process. Herein, we investigated how heteroaggregates of iron (hydr)oxides and clay minerals affect the heterogeneous oxidation of Mn(II) and crystallization of manganese (hydr)oxides (MnOx). Our results revealed that iron (hydr)oxides (ferrihydrite) and clay minerals (kaolinite or montmorillonite) in heteroaggregates can exert coupled effects on these processes, dictating the distribution of Mn and the morphology of MnOx. Specifically, ferrihydrite catalyzed gradual oxidative removal of Mn(II) and triggered MnOx nucleation; in contrast, kaolinite/montmorillonite rapidly adsorbed Mn(II) but hardly catalyzed its oxidation. These reactions collectively caused fast adsorption and gradual oxidation of Mn(II) on the heteroaggregates. Further, MnOx nanoparticles formed on ferrihydrite surfaces migrated to kaolinite/montmorillonite surfaces, which resulted in MnOx interacting with various component minerals of the heteroaggregates. This strongly altered the further growth pathways and the eventual morphology of MnOx. Consequently, while MnOx nanoparticles in the ferrihydrite-only system aggregated freely and formed well-extended nanowires, most of those in the ferrihydrite-kaolinite system became short nanorods due to the immobilization by kaolinite surfaces; in the ferrihydrite-montmorillonite system, considerable MnOx nanoparticles attached to montmorillonite surfaces due to strong electrostatic attraction, and further grew into blocky particles via particle attachment. These results illustrate that surface reactivities of heteroaggregated ferrihydrite and kaolinite/montmorillonite are coupled when they interact with Mn(II) or MnOx. Our work, for the first time, exemplify the cooperation between surfaces of various minerals during the heterogeneous formation of NMMNs. Findings from this study also help advance our understanding of MnOx formation on surfaces with diverse atomic structures, and also Mn cycling in the environment.

Influence of flame stability on iron oxide nanoparticle growth during FSP

Flame stability during flame spray pyrolysis (FSP) remains an active topic of investigation due to its impact on synthesised particle attributes and purity. The unique feature of the burner investigated here is the ability to control flame stability over newly defined stability maps. The novelty of the current work lies in understanding the influence of these broad stability modes on nanoparticle growth during FSP and on the attributes of collected products. Several distinct flame configurations are selected for iron oxide nanoparticle synthesis, ranging from stable to highly unstable flames. The flame stability regimes are characterised by OH∗ chemiluminescence and broadband flame luminescence imaging. Stability is correlated with the coefficient of variation of flame luminescence (CV) and flame height with mean OH∗ chemiluminescence. Planar Mie scattering is then used to identify the effect of flame luminescence intermittency on spray atomisation and evaporation quality. For particle analysis, in-situ thermophoretic sampling is performed from 30 to 200 mm above the burner exit plane and analysed via transmission electron microscopy (TEM). Further ex-situ analysis is also performed on the bulk-collected product via high-resolution TEM, X-ray powder diffraction (XRD), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). It is demonstrated that flames with higher instability (CVmin ≥ 0.35) maintain increased spray heights (>26 %) and reduced flame heights (>79 %) compared to stable flames with the same precursor volume flowrate. This reduces the high-temperature particle residence time for primary particle growth and impacts subsequent agglomeration. For example, the mean diameter of gyration and primary particle diameter are found to vary by 44 % and 29 % depending on the flame regime, respectively. Ex-situ analysis also demonstrates that the dominant iron oxide phase produced is maghemite regardless of the stability regime. However, higher concentrations of organic impurities including methyl, methylene and carboxylate functional groups are found via ATR-FTIR with increased flame instability (CV).

Marine-derived magnetic nanocatalyst in sustainable ultrasound-assisted synthesis of 2,3-diphenyl-2,3-Dihydroquinazolin-4(1H)-One derivatives

This research presents a sustainable approach to fabricate iron oxide nanoparticles by employing phytochemicals derived from marine grass extract as both reducing and stabilizing agents. Formation of magnetic nanoparticles (MNPs) initially confirmed by ultraviolet–visible spectroscopy (UV–vis) showing absorption peak at 370 nm. X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques unveiled magnetic iron oxide NPs with a rod shape, an average size of 21 nm, and an inverse spinel crystal structure. The participation of organic compounds in the production and stabilization of MNPs was evidenced through Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). A vibrating sample magnetometer (VSM) demonstrated the magnetic properties of iron oxide NPs showing a saturation magnetization value of 21.46 emu/g. The catalytic efficiency of these marine-assisted MNPs was evaluated in a one-pot three-component reaction involving isatoic anhydride, aromatic aldehydes, and amines under ultrasonic conditions. Under optimal conditions, a low dose of 1.5 mg of biobased magnetite nanoparticles yielded dihydroquinazolin-4(1H)-One products with up to 95 % efficiency in a brief duration of 15 min at an ultrasonic power intensity of 130 W. Different directing groups were investigated, and control experiments were carried out to enhance the understanding of the reaction mechanism. The obtained results highlight the synergistic effect of marine grass-mediated magnetic nanocatalysts combined with ultrasonic-assisted synthesis in developing sustainable green methodologies in organic synthesis.

Sensitive detection of unsafe nitrite chemical based on GO@Fe2O3/Y2O3 nanocomposite by electrochemical approach for environmental assessment

In this study, we quantified nitrite in phosphate buffer solution (PBS) at a pH of 8.00 using linear sweep voltammetry (LSV) under room conditions. The working electrodes (WE) were flat glassy carbon electrodes (GCEs) modified with a nanocomposite of graphene oxide, iron oxide, and yttrium oxide (GO@Fe2O3/Y2O3 NCs), fabricated using a 5 % Nafion conducting coating binder. The GO@Fe2O3/Y2O3 NCs were prepared by a solid-state chemical process and thoroughly analyzed using various techniques, including XRD, FTIR, FESEM, EDS, BET, HRTEM, EIS, and XPS, to examine their binding energy, surface area, crystallinity, structural integrity, functionality, and morphology. Electrochemical characteristics and detection capabilities of the modified electrodes were examined using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The linear dynamic range (LDR) for nitrite detection, determined using LSV, was from 0.74 to 1.09 M. The sensor exhibited a sensitivity of 73.83966 µAmM−1cm−2, calculated from the slope of the calibration curve considering the electrode’s surface area. The lower limit of detection (LOD) was found to be 2.25 mM, and the limit of quantification (LOQ) was 7.50 mM. Additionally, we thoroughly investigated pH optimization, sensor-probe characteristics, stability, and reliability of the sensor under the same conditions. Validity tests conducted on the GO@Fe2O3/Y2O3 NCs/Nafion/GCE sensor probe demonstrated reliable and accurate performance in spike samples. This novel electrochemical sensor method shows promise for large-scale environmental chemical monitoring, aiming to enhance safety in environmental and healthcare sectors.

Murexide retention and antibacterial performance of semiconductor copolymer/magnetic iron oxide hybrid nanocomposites synthesized via one pot in-situ chemical oxidative polymerization

Herein, semiconductor-magnetic hybrid nanocomposites, poly(vanillin-co-thiophene)/magnetic iron oxide (PVTO-Fe3O4), were successfully synthesized via single-step in situ chemical oxidative polymerization in the presence of different weight percentages of magnetic iron oxide nanoparticles Fe3O4 NPs (3, 6, and 9 wt%). Whereas the Fe3O4 NPs were prepared via an environmentally friendly, modified co-precipitation method, and their physicochemical characteristics were comprehensively analyzed using various analytical techniques. The adsorption behavior of the resulting samples towards murexide dye in aqueous solutions was investigated, along with their antibacterial efficacy against both gram-positive (Staphylococcus aureus and Bacillus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. The adsorption study revealed that the nanocomposite containing 9 wt% Fe3O4 NPs achieved the highest removal efficiency for MX (approximately 87.41 %) and exhibited a maximum adsorption capacity of approximately 100.7 mg/g, surpassing many adsorbents reported in the literature. Optimization experiments identified the optimal conditions as 40 mg of adsorbent dose, 40 mL of MX solution (125 mg/L), pH 5, and 160 min contact time. The adsorption kinetics followed pseudo-second-order kinetics, and the adsorption isotherm fitted well with the Freundlich model. Moreover, the nanocomposite was efficiently recovered from the solution using an external magnet, highlighting its potential for practical applications. Antibacterial testing revealed significant antibacterial effectiveness of PVTO and its nanocomposites against both gram-positive and gram-negative bacteria, with a minimum inhibition zone of 20 mm.

Green synthesis of ZnO/Fe3O4 nanoparticles with nigella sativa extract: Efficient degradation of methylene blue and antimicrobial properties

Zinc oxide (ZnO), iron oxide (Fe3O4) NPs, and ZnO/Fe3O4 nanocomposites (NCs) were synthesized using Nigella sativa (NS) seed extracts. These nanomaterials (NMs) were characterized by multiple analytical techniques like UV-visible spectrophotometers, FTIR spectroscopy, SEM, and XRD spectroscopy. The UV-visible spectrum showed 364 nm, 330 nm, and 331nm for ZnO NPs, Fe3O4 NPs, and ZnO/Fe3O4 NCs, respectively. Moreover, it was confirmed when the samples were run through FTIR techniques, and it was observed that the availability of bioactive functional groups was involved in the decline of bulk compounds to NPs. XRD showed their average nanoparticle size based on applying the formula of full width at half maximum (FWHM) for ZnO NPs, Fe3O4 NPs, and ZnO/Fe3O4 NCs at 29.52 nm, 22.08 nm, and 12.82 nm, respectively. In this study, the reduction of Methylene Blue (MB) dye was done by NPs and NCs, and their catalytic activities were investigated by a UV-visible spectrophotometer. MB dye showed the maximum absorption peak at 664 nm, and the reaction of MB was reduced using synthesized products with an accompanying color change reaction from blue to colorless within 60 min at 84%, 86%, and 99.5% degradation for ZnO NPs, Fe3O4 NPs, and ZnO/Fe3O4 NCs with rate constants of 0.00035, 0.00065, and 0.0015 Lmol-1S-1. The 2nd order rate constant was observed in this study. The agar disc diffusion method was used to investigate the potential antibacterial activity of synthesized NPs and NCs. This study is best suited for Gram-positive bacteria. NS seed extract-based synthesis of NCs could be an excellent catalyst and biological application for environmental pollution.

High-capacity and long-life Fe2O3/MOFs composite anodes: Preparation, characterization, morphology regulation and electrochemical performance

Among the various transition metal oxides used in lithium-ion battery anodes, iron oxide (Fe2O3) has received extensive attention due to its low cost, good environmental compatibility and high theoretical capacity. However, the volume expansion and structural collapse during the charging-discharging cycling process significantly limited the practical application of Fe2O3. Herein, we demonstrate enhanced electrochemical properties and stability of Fe2O3 by anchoring it on metal-organic frameworks (MOFs). Through adjusting the MOF ligands and introducing humic acid (HA), we reached rational control of the morphology for the Fe2O3/MOF composites. The optimized sample, namely Fe2O3@HA-Fe-ATA, shows 3D cauliflower-like structure with abundant pores, which are beneficial to the active sites exposure, electrolyte penetration, as well as the tolerance toward volume expansion. Consequently, high reversible capacity of 1442.7 mAh g−1 (at 0.1 A g−1), excellent rate performance (<11 % capacity decrease when current density increases from 0.1 A g−1 to 1 A g−1), and satisfactory cycle stability (91 % capacity retention after 500 cycles at 1 A g−1) are obtained. This work demonstrates that the rational design of MOF by introduction of appropriate ligand is a very efficient approach to optimize the electrochemical properties of the resultant electrode material.

Sintering enhancement process based on fluidity and bonding phase strength

The sintering process is influenced by complex low-grade ores. This study used seven types of imported iron ore, A–F and domestically produced iron ore, G, as raw materials to study their chemical composition, as well as the liquid fluidity and bonding strength of the mixed ore after single and optimised ore blending. The high-temperature characteristic test values of mixed ores are positively correlated with the weighted calculated values of individual ores. Under the sintering cup conditions, the optimal ore mixing includes a 9% increase in liquid fluidity and a 6% increase in bonding strength. The latter significantly improved the sintering yield and drum strength, reaching 75.89% and 65.67%, respectively. In addition, the consumption of solid fuel has slightly decreased by 0.06 kg·t−1, and the utilisation coefficient has slightly increased. In addition, the sintering yield and quality indicators of the scheme have been comprehensively improved. Compared with the benchmark scheme, through liquid fluidity optimisation, an increase in magnetite phase, a decrease in haematite, and a significant decrease in acicular calcium ferrite were observed, interwoven with magnetite. The silicate-bounding iron oxide also showed an increase in this optimisation. In the optimisation of bonding strength, the corrosive structure interwoven with magnetite and needle shaped ferrite significantly increases, while the iron oxide bound with silicate decreases. The improvement effect of liquid phase fluidity and bonding phase strength optimisation on sintering process and mineralisation behaviour was verified through sintering cup test and mineral phase analysis.

Structural and electromagnetic properties of 3D printed and electron beam sintered lithium ferrite ceramic

In this work, the structures and electromagnetic properties of lithium ferrite ceramics manufactured by the additive method, based on the extrusion deposition of ferrite samples with a binder and their subsequent heating with high-energy electron beam, were studied. Preliminary synthesis of ferrite powder was carried out by a solid-phase method using iron oxide and lithium carbonate. To prepare ferrite paste, a binder based on ethylcellulose and terpineol was used. The printed samples were sintered by heating with 1.4 MeV electron beam using an ELV-6 accelerator. Using X-ray phase analysis, it was established that the sintered ceramic consists mainly of an ordered α−Li0.5Fe2.5O4 phase and a certain amount of disordered β−Li0.5Fe2.5O4 phase. Ferrite ceramics are characterized by a relative density of 72.6–92.1%, specific saturation magnetization of 63–65 emu/g, Curie temperature of 628–630 °C, electrical resistivity of 108–106 Ω cm, depending on the thickness of the printed sample (200 and 400 μm) and sintering temperature (1100 and 1200 °С).

Production of iron oxide pigments using metallurgical wastes

To produce paints and varnish coatings, there is an opportunity to use a waste of metallurgical production of Yakovlevsky mining and processing complex, Cherepovets, Russia. This waste contains iron oxide as iron oxide pigment. It could be used as an analogue to iron oxide pigment already existing on the market. The authors studied the pigment properties of the waste and the opportunity of using it as a raw material for the synthesis of red iron oxide pigment. The article gives recommendations on the use of the obtained product and shows the opportunity of its application for paint and varnish coatings.

Distinct microbial communities supported by iron oxidation.

Microbial biostalactites and streamers commonly grow at iron seepages in abandoned mines worldwide. This study addresses the diversity and composition of these simple prokaryotic communities, which thrive in pH ranges from 2.4 to 6.6 across six different mines. Our analysis of 85 communities reveals that a pH of approximately 3.2 is a critical threshold where alpha and beta diversity change discretely. Below this pH, the average number of ASVs per sample is 2.91 times lower than above this boundary. Autotrophs, heterotrophs, and symbionts of eukaryotes originate from nearly non-overlapping species pools in the two habitat types that differ only in pH. Communities below pH 3.2 further divide into two distinct groups, differing in diversity, taxonomic, and functional composition. Both types of communities coexist within the same stalactites, likely corresponding to zones where the capillary structure of the stalactite is either perfused or clogged. These findings indicate that microbial community structure can be significantly influenced by the intricate spatial organization of the ecosystem, rather than solely by measurable environmental parameters.

Effective removal of organic compounds by g-C3N4-AQ/Fe(III) via photocatalytic oxidation and photochemical cycling of iron

Anthraquinone-anchored graphitic carbon nitride (denoted as g-C3N4-AQ), which has been reported in the photochemical production of H2O2, demonstrated significant visible light photocatalytic activity with Fe(III) for the degradation of organic compounds. The synthesized g-C3N4-AQ exhibited a light absorption spectrum and crystallinity comparable to that of pristine g-C3N4. FT-IR and XPS analyses confirmed the covalent bonding between AQ and g-C3N4. The synthesized g-C3N4-AQ generated 12μM of H2O2 within 2h under visible light illumination, a quantity negligible for the degradation of organic compounds. However, in the combination with Fe(III), the system successfully degraded organic compounds, achieving degradation of 88 – 99% in the presence of dissolved oxygen. It was also observed that the photochemical activity of g-C3N4-AQ/Fe(III) was non-selective towards the target organic compounds. Intriguingly, the visible light-illuminated g-C3N4-AQ/Fe(III) selectively degraded target organic compounds in the absence of dissolved oxygen. Experimental work employing reactive oxidant scavengers and oxidant probes revealed that •OH is the main reactive species responsible for the degradation of organic compounds in the presence of dissolved oxygen, whereas in its absence, the hole acts as the primary oxidant in the selective degradation of organic compounds. This finding provides important insights into the application of the g-C3N4-AQ/Fe(III) system for effective micropollutant removal.

The combined leaching of copper, gold and uranium in chloride solutions. I. Chalcopyrite

In a study (Part II) aimed at the simultaneous heap leaching of copper (predominantly chalcopyrite), gold and uranium from an ore, it was found that this could be achieved using chlorate as the oxidant in chloride solutions. As a result, a more detailed study has been made using electrochemical and batch leach tests on pure chalcopyrite electrodes under typical heap leach conditions.The use of chlorate at moderately low concentrations has shown that enhanced rates of dissolution of chalcopyrite can be maintained over periods up to 4 days at ambient temperatures in acidic chloride solutions. The rate of dissolution is enhanced at higher acid concentrations. The rate in the presence of chlorate does not appear to depend on the iron(III) (and presumably the copper(II)) concentration.The observed rates are significantly greater than those predicted for oxidative dissolution from the electrochemistry and the mixed potential model. An alternative non-oxidative mechanism has been revisited to account for this difference.A preliminary measurement has been made of the kinetics of the oxidation of hydrogen sufide and iron(III) by low concentrations of chlorine produced by reaction of chlorate with chloride ions. These reactions are rapid, and theory shows that they would support the proposed non-oxidative mechanism.

Synthesis and physicochemical studies of iron(III) complex compounds with TSC

The authors developed methods for the synthesis of coordination compounds of iron(III) with thiosemicarbazide (TSC).The compounds structure was proved by IR spectroscopy, conductometry, X-ray diffraction, and thermogravimetry. The authors found the bidentate coordination of TSC with iron(III) via sulphur and nitrogen atoms. Thermogravimetrically authors have established the proceeding of the complex decomposition in two stages. The first stage involves thermolysis of organic ligands with the formation of the corresponding iron salts; the second one includes decomposition of iron salts and formation of iron(III) oxide. Conductometrically we have established the synthesised complexes are strong electrolytes. X-ray diffraction shows the crystallisation of the complexes into orthorhombic syngonies. There are two structural units in the cell.

Impact of humic acid on iron (oxyhydr)oxide transport in the presence of phosphate in saturated porous media

The subsurface flow of particular phosphate (P) has been recently regarded as a vital P transport path. Humic acid (HA) and P usually coexist in the natural environment and show a strong affinity to iron (Fe) (oxyhydr)oxide. The impact of P and HA on Fe (oxyhydr)oxide stability and transport is critical for evaluating the vertical transport of particular P and biogeochemical processes of Fe and P. This study investigated the effect of inorganic (IP) and organic (OP) phosphate on the stability and transport of ferrihydrite and goethite with HA through stability tests and column experiments. The adsorption of IP or OP on Fe (oxyhydr)oxide enhanced the stability and transport of Fe (oxyhydr)oxide, and OP showed a stronger enhancement than IP due to its stronger binding capacity and more negative surface. Compared with ferrihydrite, goethite had fewer adsorption sites for IP or OP and showed strong stability and transport at low IP (50 μM) or OP (10 μM) concentration. HA decreased IP or OP adsorption on Fe (oxyhydr)oxide through competition adsorption and electrostatic repulsion. The formed ternary phosphate-Fe (oxyhydr)oxide-HA complex showed a more negative surface and strong stability and transport. Our findings provide direct insights into the distinct role of IP and OP on Fe (oxyhydr)oxide stability and transport in the presence of HA, which provides essential information for evaluating the transport of particular Fe (oxyhydr)oxide-facilitated P in soils and subsurface environments rich in iron, phosphate, and dissolved carbon.

In situ introduced oxygen-containing functional groups boost the reactivity and regenerability of FeOx/AC for cyclic denitrification-desulfurization-regeneration

Synergistic pollutant removal and resource utilization holds paramount importance in the advancement of low-carbon flue gas pollution control technologies. This work delves into a cyclic denitrification-desulfurization-regeneration (N-S-R) system over activated carbon supported iron oxides (FeOx/AC), aiming to cyclically eliminate NOx and SO2. During N-S-R cycles, FeOx/AC exhibits dynamically enhanced denitrification and desulfurization performances. Notably, the SO2 capacity of FeOx/AC attained 70.34 mg/g after five N-S-R cycles, representing a threefold increase compared to S-R cycles. A systematic investigation into the physicochemical evolution of FeOx/AC during cyclic reactions reveals the pivotal role of in situ introduced oxygen-containing functional groups (OCFGs). Specifically, C–OH and –COOH groups are defined to be introduced during the denitrification reaction and C = O groups emerge in the regeneration stage. Theoretical calculations reinforce that in situ introduced OCFGs act as auxiliary active sites alongside Fe, enhancing the adsorption of SO2, O2 and NH3 and facilitating the decomposition of Fe2(SO4)3. These findings further elucidate the synergistic promotional mechanism between OCFGs and Fe for boosting reaction performance and regeneration efficiency. Such work not only provides a promising application for the low-cost FeOx/AC, but also establishes a theoretical basis for cooperative air pollutants control over carbon materials.

Excellent antibiotic degradation through PMS activation via bio derived Fe-Mn oxides with tunable defect concentration: Synergy between singlet oxygen oxidation and electron transfer

Regulating the defect sites and structural composition of metal-based metal catalysts is an effective strategy to improve the activity of activating PMS to degrade pollutants. Herein, bio derived Fe/Mn composite oxides (BFMO) rich in oxygen vacancy composed of crystalline manganese oxide coated with amorphous iron oxide was prepared through microbial mediation, and used for PMS activation in the degradation of tetracycline (TC). After 60minutes reaction, the removal rate of TC achieved 92.4%−98.8% within wide pH range of 3-12. Besides, this system has outstanding anti-interference ability to common ions and humic acid (HA). The outstanding catalytic performance stemmed from the non-radical pathway for producing singlet oxygen (1O2) and electron transfer, facilitated by defect-rich polyvalent Mn and amorphous Fe species. Polyvalent Mn species accelerate the electron transfer process, and its surface defect structure further promotes the adsorption of pollutants on the surface of the materials. The redox cycle of Fe3+/Fe2+ was accelerate via electron-rich groups. This study explored the synergy triggered by microbe-mediated defect sites and structure-dependent, providing a design strategy for environmental remediation of PMS activated by Fe/Mn based bimetallic catalysts with strong resistance to environmental interference.

Nano magnesium oxide and nano iron oxide on growth and yield of European cucumber

Nano magnesium oxide and nano iron oxide on growth and yield of European cucumber