Main Oxidation Research Articles

Oxygen Nonstoichiometry, Electrical Conductivity, Chemical Expansion and Electrode Properties of Perovskite-Type SrFe0.9V0.1O3−δ

X-ray diffraction analysis of the pseudo-binary SrFe1−xVxO3−δ system showed that the solid solution formation limit at atmospheric oxygen pressure corresponds to x ≈ 0.1. SrFe0.9V0.1O3−δ has a cubic perovskite-type structure with the Pm3¯m space group. The oxygen nonstoichiometry variations in SrFe0.9V0.1O3−δ, measured by coulometric titration in the oxygen partial pressure range of 10−21 to 0.5 atm at 1023–1223 K, can be adequately described using an ideal solution approximation with V5+ as the main oxidation state of vanadium cations. This approach was additionally validated by statistical thermodynamic modeling. The incorporation of vanadium decreases both oxygen deficiency and the average iron oxidation state with respect to undoped SrFeO3−δ. As a result, the electrical conductivity, thermal expansion and chemical expansivity associated with the oxygen vacancy formation all become lower compared to strontium ferrite. At 923 K, the conductivity of SrFe0.9V0.1O3−δ is 14% lower than that of SrFeO3−δ but 21% higher compared to SrFe0.9Ta0.1O3−δ. The area-specific polarization resistance of the porous SrFe0.9V0.1O3−δ electrode deposited onto 10 mol.% scandia- and 1 mol.% yttria-co-stabilized zirconia solid electrolyte with a protective Ce0.9Gd0.1O2−δ interlayer, was 0.34 Ohm×cm2 under open-circuit conditions at 1173 K in air.

Oxidation Kinetics of Iron-Chromium and Iron-Chromium-Aluminium Alloys

The paper presents a mathematical model to describe thermogravimetric curves of the growth of scale with its simultaneous sublimation during oxidation of the surface of a metal or alloy. For alloys iron-chromium and iron-chromium-aluminium, a decrease in the effective reaction area as a result of the formation of the oxide of the alloying element lanthanum or yttrium (together with the formation of the main oxide: chromia or alumina) is considered. For metals, the case of increasing this area is also considered. During the oxidation of the chromia-forming alloy, another secondary process is added: the evaporation of chromia. Therefore, the equations describing the kinetics of changes in mass of these alloys are different. Equations are also considered that make it possible to describe the kinetics of the oxidation process taking into account the initial non-isothermal heating. The formal equations of the oxidation process with an increase in the reaction surface as a result of crushing metal powder are also considered. The resulting equations are used to describe the kinetic curves of changes in the mass of the samples under study. The given equations can be considered as a more accurate approximation to describe the experimental data than the formulas known so far.

Temporal dynamics of soil microbial C and N cycles with GHG fluxes in the transition from tropical peatland forest to oil palm plantation.

Tropical peatlands significantly influence local and global carbon and nitrogen cycles, yet they face growing pressure from anthropogenic activities. Land use changes, such as peatland forests conversion to oil palm plantations, affect the soil microbiome and greenhouse gas (GHG) emissions. However, the temporal dynamics of microbial community changes and their role as GHG indicators are not well understood. This study examines the dynamics of peat chemistry, soil microbial communities, and GHG emissions from 2016 to 2020 in a logged-over secondary peat swamp forest in Sarawak, Malaysia, which transitioned to an oil palm plantation. This study focuses on changes in genetic composition governing plant litter degradation, methane (CH4), and nitrous oxide (N2O) fluxes. Soil CO2 emission increased (doubling from approximately 200 mg C m-2 h-1), while CH4 emissions decreased (from 200 µg C m-2 h-1 to slightly negative) following land use changes. The N2O emissions in the oil palm plantation reached approximately 1,510 µg N m-2 h-1, significantly higher than previous land uses. The CH4 fluxes were driven by groundwater table, humification levels, and C:N ratio, with Methanomicrobia populations dominating methanogenesis and Methylocystis as the main CH4 oxidizer. The N2O fluxes correlated with groundwater table, total nitrogen, and C:N ratio with dominant nirK-type denitrifiers (13-fold nir to nosZ) and a minor role by nitrification (a threefold increase in amoA) in the plantation. Proteobacteria and Acidobacteria encoding incomplete denitrification genes potentially impact N2O emissions. These findings highlighted complex interactions between microbial communities and environmental factors influencing GHG fluxes in altered tropical peatland ecosystems.IMPORTANCETropical peatlands are carbon-rich environments that release significant amounts of greenhouse gases when drained or disturbed. This study assesses the impact of land use change on a secondary tropical peat swamp forest site converted into an oil palm plantation. The transformation lowered groundwater levels and changed soil properties. Consequently, the oil palm plantation site released higher carbon dioxide and nitrous oxide compared to previous land uses. As microbial communities play crucial roles in carbon and nitrogen cycles, this study identified environmental factors associated with microbial diversity, including genes and specific microbial groups related to nitrous oxide and methane emissions. Understanding the factors driving microbial composition shifts and greenhouse gas emissions in tropical peatlands provides baseline information to potentially mitigate environmental consequences of land use change, leading to a broader impact on climate change mitigation efforts and proper land management practices.

Point defects in complex inorganic compounds, spinel inverted, Kirkendall ‒ Frenkel effects

New technologies require new materials. One of the ways to find such materials are normal, reversed and partially reversed materials, which are used in spinels. Some such compounds are considered in oxygen-containing spinels, in particular, magnetic materials. Spinel inversion often results in structural defects, including antistructural exchange of cations. The preparation of solid solutions in aluminamagnesia spinel and mullite, which are not presented in the phase diagram, but have a higher diffusion mass transfer coefficient during the synthesis of a complex oxide, is considered. For spinel it is MgO, for mullite it is SiO2. For this, additives and the Kirkendall ‒ Frenkel effect were used. So far, there is no complete certainty that these are not composites, in which a material with a high diffusion mass transfer coefficient is distributed in a matrix of the main complex oxide (MgO·Al2O3, or 3Al2O3·2SiO2). The application of these approaches can expand the scope of materials for various applications.

Efficient degradation of polyethylene (PE) plastics by a novel vacuum ultraviolet-activated periodate system: Operating parameters, by-products, and toxicity

This article presents a vacuum ultraviolet (VUV)-activated periodate (PI) system for the degradation of polyethylene (PE) plastics for the first time. The study compares the performance of the VUV/PI with VUV/sulfite, VUV/peroxymonosulfate, and VUV/persulfate degradation systems. At an oxidant concentration of 5mM, reaction time of 6h, PE plastics concentration of 0.1g/L, PE plastics size of 12mm, and pH 7, VUV/PI degradation system attained a mass loss ratio of 3.9%, which was higher than the other degradation systems. The mass loss ratio increased to 4.9% at pH 3, and 6.8% for a plastic size of 6mm. The degradation mechanism was found to involve iodate radicals and singlet oxygen as the main reactive species. Prolonging reaction time to 120h resulted in a mass loss percentage of 61.8%. SEM, FTIR, and water contact angle analyses after the degradation show cracks on PE plastics surface, an increase of carbonyl index, and a decrease of hydrophobicity affirming the efficient oxidation of PE plastics by the generated reactive species. The main oxidation by-products were alcohols, esters, acids, and ketones. Cytotoxicity and phytotoxicity analyses confirmed the efficient oxidation of PE plastics by the generated reactive species to result in low toxicity of the generated intermediates. The proposed study presents a simple and effective degradation system that can be implemented on a wider scale as a tertiary treatment in wastewater treatment plants for the degradation of plastics before release to the ecosystem.

Preparation of high oxygen vacancies catalyst CeO2/Al2O3-SiC and its mechanism in enhancing the catalytic ozonation of organic pollutants in coal chemical wastewater

The complete harmless treatment of aromatic organic compounds in coal chemical wastewater (CCW) has always been a big challenge in water process engineering. This study addresses the issue by designing and preparing a kind of Ce and Al bimetallic catalyst with high oxygen vacancies (OVs) based on SiC carrier. The results showed that CeO2 and Al2O3 were uniformly dispersed on SiC, and the composite material exhibited an ordered cubic structure. The degradation efficiency and enhancement mechanism of the catalyst with ozone oxidation were investigated. When applied to actual CCW with a chemical oxygen demand (COD) concentration exceeding 600 mg/L, the synergy between O3 and CeO2/Al2O3-SiC increased the degradation efficiency of phenols from 50 % to 99 % and COD from 42 % to 78 % compared to using O3 alone. CeO2/Al2O3-SiC had a high concentration of oxygen vacancies (OVs = 48.57 %). Further research indicated that oxygen vacancies (OVs) were the main active sites for ozone adsorption and reactive oxygen species (ROSs) generation. Electron paramagnetic resonance (EPR) and quenching experiments also confirmed that O3, •O2−1, 1O2 were the main active oxidation factors, rather than •OH. Additionally, even after granulating the catalyst, it still achieved 99 % degradation of phenols. Therefore, this study provides theoretical support for the complete harmless treatment of CCW and has broad prospects for industrial application.

Insight into the Thermal Washing Mechanism of Sodium Lignosulfonate Alkyl/Sodium Persulfate Compound on Oily Sludge.

The thermal washing of oily sludge using sodium persulfate (SD) assisted by sodium lignosulfonate surfactant has been demonstrated to be an effective method for oily sludge remediation. To further explore the underlying mechanisms of this process, a systematic study was conducted by simulating oily sludge systems consisting of saturated hydrocarbons (SaH), aromatics hydrocarbons (ArH), resins (Res), and asphaltenes (Asp). The effects of reaction conditions, such as pH, sodium lignosulfonate alkyl (LSA) concentration, SD concentration, and washing temperature, were analyzed. Furthermore, the oxidative kinetic mechanism during the reaction process was investigated. The results demonstrated that neither petroleum hydrocarbons nor SD underwent significant chemical transformations when exposed to LSA, while SD exhibited a marked oxidative degradation effect on all four types of hydrocarbons. Oxidation kinetics indicated that sodium hydroxide played a catalytic role, with SD being the main oxidant and particularly efficient in degrading Asp and Res. Meanwhile, LSA contributed to the removal of hydrocarbons by reducing the surface tension of the solution, enhancing solubilization. This study not only elucidates the central role of SD in the thermal washing process but also provides a solid theoretical foundation for the practical application of this technology in oily sludge treatment.

Nanoconfinement Enables Photoelectrochemical Selective Oxidation of Glycerol Via the Microscale Fluid Effect

The glycerol oxidation reaction (GOR) run with photoelectrochemical cells (PECs) is one of the most promising ways to upgrade biomass because it is thermodynamically favorable, while irreversible overoxidation leads to unsatisfactory product selectivities. Herein, a tunable one-dimensional nanoconfined environment was introduced into the GOR process, which accelerated mass transfer of glycerol via the microscale fluid effect and changed the main oxidation product from formic acid (FA) to glyceraldehyde (GLD), which led to retention of the heavier multicarbon products. The rate of glycerol diffusion in the nanochannels increased by a factor of 4.92 with decreasing inner diameters. The main product from the PEC-selective oxidation of glycerol changed from the C1 product FA to the C3 product GLD with a great selectivity of 60.7%. This work provides a favorable approach for inhibiting further oxidation of multicarbon products and illustrates the importance of microenvironmental regulation in biomass oxidation.

Electrochemical Activities of Mesoporous Pt Particles/MWCNT/ITO Electrodes for Hydrogen Generation and Glycerol Oxidation

Hydrogen produced via water electrolysis has attracted attention as a next-generation secondary energy source because of its high mass energy density and its ability to be produced by low greenhouse gas emissions during water electrolysis. In contrast to hydrogen generation at the cathode in water electrolysis, oxygen production at the anode via water electrolysis, requires a high overpotential. In this study, glycerol oxidation, which produces fine chemicals, was used to reduce the overpotential of the anode reaction. Platinum is a highly active catalyst for both hydrogen production and glycerol oxidation; however, it is not suitable for large-scale operations because of its high cost. To reduce the amount of platinum used, mesoporous platinum was electrochemically deposited on multiwalled carbon nanotube (MWCNT) film electrodes,to prepare electrodes with excellent conductivity and a large Pt surface area. The three-dimensional structure of the porous composite thin-film influences the mass transfer of products associated with hydrogen production and glycerol oxidation. Furthermore, the morphology of mesoporous Pt can nfluence electrohemical activities for these reactions by changing the surface structure of platinum. In this study, we investigated the effects of potential and the amount of electricity applied during mesoporous Pt deposition, resulting in different Pt morphologies, on the electrochemical activities for hydrogen production and glycerol oxidation at thin-film electrodes. MWCNTs were deposited on the ITO substrate via electrophoresis using sodium dodecyl benzene sulfonate (SDBS) as a surfactant. Subsequently, Pt particles were deposited on the MWCNT film electrodes via chronoamperometry in a solution containing Pt ion and Brij58. The Pt particles were deposited until the amount of electric charges reached 100 mC, 300 mC, 500 mC, and 800 mC by applying different potentials to the MWCNT film electrode, i.e., -0.1 V, -0.3 V, -0.5 V, or -0.7 V. Subsequently, micelles of Brij58 embedded in the Pt particles were removed by immersing the electrodes in ethanol to prepare mesoporous Pt/MWCNT electrodes with pore sizes in Pt particles of 5-10 nm. To evaluate the electrochemical performance of the as-prepared electrodes for hydrogen production and glycerol oxidation, cyclic voltammetry (CV) and polarization curve measurements were performed in a 0.1 M glycerol solution containing 0.1 M NaOH. All electrochemical measurements were carried out using a three-electrode cell with an as-prepared electrode as the working electrode, Ag/AgCl (saturated KCl) as the reference electrode, and platinum wire as the counter electrode.As shown in Fig. 1 and 2, one main oxidation peak was observed in cyclic voltammograms measured in the glycerol solution for all mesoporous Pt particles/MWCNT electrodes at around 0.3 V, and additional oxidation peak was observed at nobler potential than the main peak when the amount of electric charge during platinum deposition was 300 mC and more for electrodes prepared at -0.1 V. These peaks are due to the oxidation current related to glycerol, as both of them were not observed in the 0.1 M NaOH solution. By increasing the electrical charges for Pt deposition, the oxidation peak potential at around 0.3 V was observed to shift to baser potential (Fig.1), which suggest better electrochemical activity. Comparing the voltammograms of electrodes prepared at different deposition potentials, the oxidation peak potential is the smallest for the electrode prepared at -0.3 V, and the oxidation peak current at around 0.3 V appeared to be larger when applying potential of -0.5 and -0.7 V (Fig.2). These changes both in the potential and current of the peak are partially due to the effect of the additional oxidation peak observed at nobler potential than the main peak, which was observed to shift to a baser potential by changing the deposition potential from -0.1 V to -0.7 V. The exchange current density calculated from the polarization curve was 4.64 mA/㎠ for hydrogen production and 9.12 mA/㎠ for glycerol oxidation for the Pt/MWCNT electrodes prepared at -0.5V with 300mC, showing the best electrochemical activity in both reactions among all the prepared-electrodes. The influence of the thin-film morphology is also discussed in this presentation. Figure 1

Crystallization Pathways of Iron Formations: Insights From Magnetic Properties and High-Resolution Imaging of the 2.7 Ga Carajás Formation, Brazil.

Banded iron formations (BIFs) are chemical sedimentary rocks commonly utilized for exploring the chemistry and redox state of the Precambrian ocean. Despite their significance, many aspects regarding the crystallization pathways of iron oxides in BIFs remain loosely constrained. In this study, we combine magnetic properties characterization with high-resolution optical and electron imaging of finely laminated BIFs from the 2.7 Ga Carajás Formation, Brazil, to investigate their nature and potential for preserving ancient environmental conditions. Our findings reveal that magnetite, in the form of large 0.1-0.5 mm crystals, is the main iron oxide, with an overall averaged saturation magnetization (Ms) of 25 Am2/kg (corresponding to ~27 wt% of magnetite) over the studied 230 m of the sequence. Nevertheless, the non-negligible contribution of minerals with higher coercivity suggests variable proportions of hematite along the core. Additionally, we observe non-uniform behavior in magnetite grains, with distinct populations identified through low-temperature measurements of the Verwey transition. Petrographic observations indicate that the original sediment was an Fe-Si mud consisting of a ferrihydrite-silica mixture formed in the water column. This assemblage was rapidly transformed into nano-scale hematite embedded in silica as indicated by a honeycomb structure composed of Si-spherules distributed in a microscale hematite matrix. Textural relationships show that the nucleation of magnetite started during or soon after the formation of hematite, as indicated by the preservation of the Si-spherules within magnetite cores. Further magnetite overgrowth stages are characterized by inclusion-free rims, associated with continuous Si supply during the evolving diagenetic or early metamorphic stages. These findings, combined with existing literature, suggest that ferrihydrite precipitated alongside Si and organic material, later crystallizing as hematite on the seafloor. Anaerobic respiration by Fe(III)-reducing microorganisms likely contributed to early magnetite formation in a fluid-saturated, unconsolidated sediment. Subsequent low-grade metamorphism and Si mobilization led to palisade quartz precipitation and a second stage of magnetite growth likely formed at the expense of matrix hematite through thermochemical Fe(III) reduction. Low-temperature magnetic analyses revealed that the two generations of magnetite core and rim are associated with specific stoichiometry.

A Review on the Gas‐Phase Modeling Study of Aluminum Combustion in Various Environments

AbstractAluminum combustion is an area of intense research due to its wide‐ranging applications in the aerospace, automotive, energy storage carrier and defense industries. Gas‐phase reaction mechanism plays an important role on the prediction of the combustion intermediates and final products, which can significantly affect the combustion heat releases and combustion organization forms. In recent years, researchers have developed some gas‐phase reaction mechanisms to predict the combustion phenomenon and behavior of aluminum in different environments. This review aims to provide an overview of the current state of the art in gas‐phase modeling study on aluminum combustion with various oxidizers, including oxygen, steam, carbon dioxide and so on. The primary oxidation reactions of aluminum were concluded, and the rate coefficients of these reactions were also reviewed and compared in this work. Besides, the simulations by using the gas‐phase reaction mechanisms were reviewed and the main oxidation reaction pathways of aluminum with various oxidizers were analyzed based on modeling analysis results. Combining phase change reactions and surface reactions, gas‐phase reaction mechanism will become more important for prediction the combustion speed, combustion temperature and combustion mode of aluminum in future.

Structural Changes in Copper Slags During Slow Cooling

The objects of the study were converter slags from the Balkhash copper plant in their initial state and after heat treatment. Using mineralogical and X-ray phase analysis, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA), it was found that the initial converter slag and its thermally treated samples have identical matrices with almost complete coincidence in mineral and phase compositions. The distinguishing feature is the quantitative ratio of mineral components in the slag mass. Almost all of the iron is oxidized and present in the form of fayalite, magnetite, and magnetite, with other elements (silicon, copper, zinc, and aluminum) incorporated into its lattice. The structure of all slag samples indicates an association of sulfur exclusively with copper. Copper in the slags was identified in both metallic and sulfide forms. Slow cooling of the converter slag after its remelting contributes to the reduction in the sulfide–metal suspension in the volume of the melt and its coarsening. During slow cooling, structural changes occur not only in the main oxide part of the slag but also in the polymetallic globules.

Evaluation of the corrosion and oxidation resistance of NiCoCrAlY cladding on CMSX-4 by laser cladding

This study uses laser cladding to investigate the hot corrosion and oxidation behavior of CMSX-4 claddes with NiCoCrAlY powder. High-temperature oxidation tests were conducted at 1050°c for 50, 100, 150, and 200 h on 4 samples, while 6 samples underwent hot corrosion testing at 850°c for 6 h. The innovative application of laser cladding enables the creation of a γ′ and β interdendritic phase microstructure. High-temperature oxidation tests reveal a growth rate of 0.05 μm/h in oxide layer thickness between 50 and 200 h, accompanied by a surface weight increase rate of approximately 0.8 mg/cm2.h. The oxide layer's regeneration, continuity, and density are observed at 200 h, highlighting the innovative potential of this technique. Fracture oxidation is observed at 150 h in some TGO layer regions, but at 200 h of oxidation, the TGO layer's regeneration, continuity, and dense TGO was observed at the cladding interface. The TGO forms at 1050°c consist of Al2O3, Cr2O3, and CoO oxides, with Al2O3 as the main oxide phase. The study's findings demonstrate the ability of laser cladding to enhance the thermal protection of CMSX-4, showcasing a promising innovation in the field.

Mechanical processing of wet stored fly ash for use as a cement component in concrete

Wet storage effects on fly ash mean that processing may be necessary to achieve the physical properties required for use in concrete. This paper considers drying, de-agglomeration and milling of various wet stored fly ashes at laboratory and pilot/benchtop scales, towards meeting these. In the laboratory, different batch quantities and milling times with as-received/pre-screened materials were examined using a ball mill. Greater particle size reductions were obtained with increased milling time but at gradually reducing rates. Pre-screening and batch quantity had relatively minor effects on particle size reductions, with small differences also found between wet and dry stored fly ash. Extended milling time resulted in a darkening of colour; slight increases in loss-on-ignition, the main oxides content and crystalline components; reductions in water requirement (to a point); and greater reactivity. Similar effects were generally noted in concrete for the superplasticising admixture dose to achieve a target slump and compressive (cube) strength. At pilot/benchtop scale, a dryer-pulveriser and spiral jet mill were used, which gave general agreement with the behaviour noted in the laboratory, but with the effects tending to be less. Fineness levels in Standards were achievable, with subsequent performance in concrete, appearing to depend on the milling process used.

Clay mineralogy in mylonite weathering products from Njimom (west Cameroon): origin and terracotta suitability

This study investigated the mineralogical assemblage of weathering products developed on mylonite rocks in west Cameroon. Smectite and vermiculite occurrence was studied, particularly to emphasize its origin and the potential of the samples in terracotta production. Samples characteristics were determined through X-Ray Diffraction (XRD) and X-ray Fluorescence (XRF) methods. Weathering products were observed along road trenches of 450 m long and 50 m height on a syenitic basement rock intruded by magmatic rock veins. Clay minerals are mainly composed of kaolinite and illite. 2:1 swelling clay minerals (vermiculite, montmorillonite) occur in some samples mainly originated from the contact between weathering materials and quartzo feldspatic bands. The main oxides are SiO2 (46–72%), Al2O3 (16–31%), Fe2O3 (2–16%) and K2O (0.1–6%). Vermiculite may be formed by fluid-mineral interactions during alteration of the chlorite in the plasmic microsystems of the soil. Structural changes in the upper part of the saprolite leading to the transformation of vermiculite into smectite under supergene alteration control, which predominates in humid tropical zones. Heavy rainfall leads to the formation of kaolinite at the expense of 2:1 clay minerals. Empirical classification revealed that the studied weathering products can be used to produce common bricks.

Using synchrotron based ATR-FTIR, EXAFS, and XRF to characterize the chemical compositions of TSP in industrial estate area

In Thailand, the Map Ta Phut Industrial Estate (MTPIE), a prominent industrial hub, has substantial environmental and health issues caused by industrial pollution. This study uses advanced synchrotron-based techniques, such as Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR), Extended X-ray Absorption Fine Structure (EXAFS), and X-ray Fluorescence (XRF), to fully examine the chemical make-up of total suspended particulate (TSP) in the given area. Notable findings include the detection of remarkably high enrichment factors for magnesium and sulfur, indicating the presence of industrial operations. Additionally, we found that magnetite, which accounts for an average of 40 % of the total iron oxides in the samples, is the main iron oxide. The study also highlights about how calcium carbonate and different organic functional groups are found in large amounts, which shows that industrial emissions and natural sources are connected in a complex way. The findings underscore the susceptibility of children to TSP exposure, revealing increased rates of inhalation and significant health hazards. In order to safeguard public health in industrial areas such as MTPIE, it is imperative to implement more sophisticated pollution control techniques and maintain ongoing environmental monitoring.

Enhancing the Regeneration Performance of Methylene Blue Saturated Biochar in H2O2 System via Fe‐Doping

AbstractTo improve the regeneration efficiency of methylene blue (MB) saturated biochar in H2O2 system, biochar was modified by Fe‐doped by using FeSO4 and Fe(NO3)3 as iron sources. The effects of Fe‐doped on its microstructure were characterized by XRD, SEM, and BET. The adsorption and regeneration performance of biochar before and after Fe‐doped were compared through adsorption and regeneration experiments. X‐ray photoelectron spectroscopy, electron spin resonance, and quenching experiments were used to explore the regeneration mechanism. The results show that Fe‐doped biochar (SP‐GBC) prepared from FeSO4 maintains a high specific surface area of 1205.9 m2/g and a high adsorption capacity of 375.43 mg·g−1 for MB. After adsorption, the MB‐saturated SP‐GBC exhibits excellent regeneration performance in the H2O2 system, in which the regeneration efficiencies for five consecutive cycles are 85.76%, 83.92%, 94.01%, 99.24%, and 100.79%, respectively. The synergistic effect of H2O2 desorption and degradation is the main regeneration mechanism for MB‐saturated SP‐GBC. The zero valent iron and Fe (II) on the surface of SP‐GBC are the main active sites for H2O2 activation, while 1O2 and HO· are the main oxidation species. In summary, this work provides a simple and feasible method for the design and synthesis of adsorbents with highly efficient regeneration performance.

The effect of configurational entropy and refractory elements on the oxidation behaviour of high entropy carbides containing up to eight refractory elements

High entropy carbides (HECs) have attracted increasing attention due to their promising oxidation resistance properties. The oxidation behaviour of (Zr,Nb,Ta,Hf,Cr)C (HEC5-Cr), (Ti,V,Cr,Zr,Nb,Hf,Ta,W)C (HEC8-Cr), and (Ti,V,Zr,Nb,Mo,Hf,Ta,W)C (HEC8-Mo) powders was compared and studied from room temperature to 1200 °C. It was found that the oxidation onset temperatures (OOT) for the HEC5-Cr, HEC8-Cr, and HEC8-Mo powders were 790 °C, 688 °C, and 617 °C respectively. The high entropy effect benefits the structural stability of carbides and thus improves their oxidation resistance. However, there is no direct correlation between the configurational entropy value and the OOT of the studied HECs. Compared to the configurational entropy value, the refractory elements in HECs and the thermal stability of the produced oxides have a more significant impact on the oxidation resistance of HECs. Most of the group IV, V, and VI metals except W, Mo, and V have main oxides suitable for high-temperature applications, making them attractive candidates for oxidation-resistant HECs.

Synergistic ultra-high adsorption and oxidation of arsenic in groundwater by iron-modified biochar: Mechanisms and potential application

This study explores the potential of low-cost biochar modified with ferrihydrite and goethite for the remediation of heavily As-polluted groundwater. Combining batch experiments and synchrotron radiation-based characterization, we investigated the mechanisms of As(III) adsorption and oxidation. The modified biochars exhibited significant adsorption capacities, achieving fitted qmax of 45.7 ± 3.9 mg/g for ferrihydrite-modified biochar (FhGM) and 20.2 ± 1.5 mg/g for goethite-modified biochar (GtGM) at a dosage of 1.0 g/L and an initial concentration of 10 mg/L As(III) over 24 h. Biochar facilitated approximately 30 % As(V) generation from As(III) due to enhanced electron transfer. Moreover, over 90 % of As(III) was oxidized to As(V) following the addition of H2O2, with scanning transmission X-ray microscopy revealing the distribution of As(III), and As(V) on the solid phase. In the GtGM-H2O2 system, reactive oxidation species, primarily O2•–, served as the main oxidant. In the FhGM-H2O2 system, Fe(IV) likely acted as the primary oxidizing agent. Column experiments with 0.64 g of FhGM demonstrated that, when treating 50 mg/L As-contaminated groundwater, the effluent total As concentration remained below the maximum allowable limit of 10 μg/L after 21 h. Furthermore, in the presence of H2O2, the system managed to treat 200 mg/L As-contaminated groundwater, and the effluent total As concentration exceeded 10 μg/L after 11 h. This study provides valuable insights and practical results for the remediation of high-concentration arsenic-contaminated groundwater, highlighting the effectiveness of iron-modified biochar in this application.

Petrogenesis of Metamorphic Rock in the Mukito Formation at Sorawolio Region, Bau-Bau City, Buton Island, Southeast Sulawesi Province, Indonesia

The petrogenesis study of the metamorphic rocks of the Mukito Formation was carried out in the Sorawolio area, Bau-Bau City, Buton Island, Southeast Sulawesi Province, Indonesia. This research area is included in the southern part of the Buton sheet with coordinates S 5⁰23'40.8'' and E 122⁰43'44.9''. The aim of this research is to determine the petrogenesis of metamorphic rocks which includes determining the rock type, facies, type of metamorphism and protolith. The research methods used include megascopic and microscopic analysis of rocks in the form of petrographic analysis which includes identification of mineral content and rock texture and geochemical analysis in the form of XRF tests to determine the main oxide elements in metamorphic rock samples. Data obtained from the results of petrographic analysis show that the research area consists of several types of metamorphic rock, namely serpentinite, phyllite, chlorite schist, hornblende schist and amphibolite. The metamorphic rocks in the research area are included in the greenschist facies and amphibolite facies with regional metamorphism types as well as protoliths from igneous rocks in the form of basalt rock which were formed in the tholeiitic oceanic-island tectonic environment which is a convergent complex characterized by continental origin in the magma series in the form of the tholeiitic series and calc -alkaline series.