Electron Microscopy-energy Dispersive X-ray Spectroscopy Research Articles

Durability properties of ambient-cured fly ash-phosphogypsum blended geopolymer mortar in terms of water absorption, porosity, and sulfate resistance

This paper aimed to investigate the durability of ambient-cured fly ash-phosphogypsum blended geopolymer mortar (GPM) when exposed to a water and sulfate environment at different durations. Water absorption, porosity, and sulfate resistance tests were conducted to determine the durability. The GPM was prepared at 0 wt%, 30 wt%, and 40 wt% PG replacement of fly ash content in the mixture. The mix proportions were determined experimentally at 10 M sodium hydroxide, alkaline liquid/precursor of 0.4, sodium silicate/sodium hydroxide of 1.5, and binder/aggregate of 1.0. The samples were immersed in potable water and magnesium sulfate solution. The changes in weight, length, and compressive strength were monitored. Scanning electron microscopy-energy dispersive X-ray spectroscopy was used to analyze the structure and composition. The findings showed that GPM with 30 wt% phosphogypsum added had lower water absorption, porosity, and sulfate attack than GPM with 0 wt% phosphogypsum attributed to the formation of hydrated gels leading to a dense microstructure and improved strength. The changes in weight, length, and strength variations trend for GPM were within optimal performance standards. This has implications for the practical application of GPM in construction where it can be used as an alternative to Portland cement mortar in sulfate-rich environments.

Effect of traps and conductive pathways on electron emission from copper broad-area composite emitters

This study investigates electron emission from copper broad-area emitters (CBAEs) and copper broad-area composite emitters (CBACEs) based on the principles of trapping and conductive pathways. Emission current measurements were conducted on two CBACEs, which consisted of copper coated with a 300–400 μm epoxy resin and subjected to high voltages up to 15 kV. The research specifically examines the ‘switch-on’ and collapse phenomena occurring within the epoxy layer. Field emission microscopy (FEM) was utilized in a high-vacuum environment ( 10−6 mbar) to observe these effects. A comprehensive model is developed to explain the formation of conductive pathways within the epoxy layer, allowing electrons transfer from traps to the surface. This model treats the composite emitter as a trap-rich capacitor. The study also clarifies the effects of trap density and epoxy layer thickness on the collapse process. To gain a deeper understanding of the model, changes in the I-V curve were examined. Simulations, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) images, and Fourier transform infrared spectroscopy (FTIR) analysis were employed to understand the collapse mechanism of the epoxy collapse. Additionally, Nyquist and Cole–Cole plots were analyzed across frequencies ranging from 1 to 106 Hz before and after applying a high electric field on the samples, revealing changes in the capacitive component and the role of diodes in the formation of conductive channels.

Removal of Pb(II) and Cd(II) from a Monometallic Contaminated Solution by Modified Biochar-Immobilized Bacterial Microspheres.

Lead (Pb) and cadmium (Cd) are toxic pollutants that are prevalent in wastewater and pose a serious threat to the natural environment. In this study, a new immobilized bacterial microsphere (CYB-SA) was prepared from corn stalk biochar and Klebsiella grimontii by sodium alginate encapsulation and vacuum freeze-drying technology. The removal effect of CYB-SA on Pb(II) and Cd(II) in a monometallic contaminated solution was studied. The results showed that the removal of Pb(II) and Cd(II) by CYB-SA was 99.14% and 83.35% at a dosage of 2.0 g/L and pH = 7, respectively, which was 10.77% and 18.58% higher than that of biochar alone. According to the Langmuir isotherm model, the maximum adsorption capacities of Pb(II) and Cd(II) by CYB-SA at 40 °C were 278.69 mg/g and 71.75 mg/g, respectively. A combination of the kinetic model, the isothermal adsorption model, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analyses showed that the main adsorption mechanisms of CYB-SA encompass functional group complexation, ion exchange, electrostatic attraction and physical adsorption. The findings of this study offer practical and theoretical insights into the development of highly efficient adsorbents for heavy metals.

Copper-Based Metal–Organic Framework: Synthesis, Characterization and Evaluation for the Hydrogenation of Furfural to Furfuryl Alcohol

AbstractA novel Cu-MOF was synthesized at room temperature from commercially available and inexpensive reagents. The pre-catalyst was characterized using X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, inductively coupled plasma-optical emission spectroscopy, Fourier transform-infrared spectroscopy, powder X-ray diffraction, Brunauer-Emmet-Teller (BET) and scanning electron microscopy-energy dispersive X-ray spectroscopy. The Cu-MOF was characterized as microporous material with BET surface area and pore volume of 7.47 m2/g and 0.27 cm3/g, respectively, and is stable in most solvents. The MOF was evaluated as a heterogeneous catalyst for the hydrogenation of furfural to furfuryl alcohol (FA). Cu-MOF exhibited a high conversion of FF (76%) with selectivity towards FA (100%) at 140 °C, 50 bar for 24 h. The MOF was reused four consecutive times with a loss in catalytic performance. The decrease in catalytic activity could be attributed to the formation of inactive Cu(0) as revealed by HR-TEM and XPS studies. The HR-TEM of spent Cu-MOF showed a uniform particle size diameter of 3.5 nm. This work is significant in providing new strategies for the design and fabrication of highly selective MOF catalysts for the FF upgrading.

Geochemical characterization and reserve estimation of the economic heavy minerals of Sonadia Island, Bangladesh

The goal of the current study is to understand the elemental concentration, reserve assessment, mineralogical composition, and distribution of heavy minerals in the dune sands, foreshore, and backshore of Sonadia Island, Southeast Bangladesh. The study area yielded a number of drill hole composite sand samples that were used for density and magnetic separation of heavy minerals. These samples were then subjected to petrographic characterization, grain counting, mineralogical analyses using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM–EDX), x-ray diffraction (XRD), and bulk sand geochemistry using X-ray fluorescence (XRF). The results of heavy liquid separation show that the total heavy mineral (THM) enrichments in foreshore sand (about 4.86%), backshore sand (about 9.03%), and dune sand (about 22.28%) are significantly higher. After characterizing the sand samples from Sonadia Island based on the abundance of each mineral species, the average content values relative to total economic heavy minerals (TEHM) were determined to be 38.14% ilmenite, 5.74% magnetite, 51.52% garnet, 1.01% zircon, 3.57% rutile, and 0.01% monazite. An SEM–EDX examination reveals that the elemental concentration of ZrO2 in zircon is 66.60%, while the average TiO2 content in rutile is ~ 95%, whereas TiO2 is 45% and the total Fe2O3 is 45.70% in ilmenite. Major phases including amphibole (tremolite) 45.9%, muscovite 15.6%, quartz 12.6%, garnet (almandine) 10.9%, dolomite 7.9%, ilmenite 4.1%, and kaolinite 1.3% are also identified by the XRD pattern. There are an estimated 19,794 tons of garnet in the foreshore sand, 47,324 tons in the backshore sand, and 276,868 tons in the dune sand within the reserve, making it the most prevalent heavy mineral. Ilmenite is the second most common heavy mineral, with quantities detected in the foreshore (15,016 tons), backshore (30,487 tons), and dune sand (215,092 tons).

Stabilization of Arsenic and Heavy Metal Contaminated Soil Using Fishery By-Products and Evaluation of Heavy Metal Uptake in Crops

Objectives : Heavy metals eluted from mine waste pollute surrounding soil and water systems, which can spread to crops and have a harmful effect on the human body. The purpose of this study was to evaluate the feasibility of recycling discarded mussel shells(MS) and manila clam shells (MC) as stabilizers for the immobilization of arsenic(As) and heavy metals(Pb, Zn) in soil.Methods : MS and MC were processed with -#10 mesh natural material, -#20 mesh natural material, and -#10 mesh calcined material and treated at 0-10 wt%. After 1 week or 4 weeks of wet curing, it was eluted with 0.1 N HCl and the concentrations of As, Pb, and Zn in the soil were analyzed through inductively coupled plasma optical emission spectroscopy(ICP-OES) analysis. In addition, red lettuce was cultivated in the stabilized soil and the concentration of heavy metals that were transferred to crops was evaluated. The stabilization mechanism was investigated by scanning electron microscopy-energy dispersive X-ray spectroscopy(SEM-EDX) analysis.Results and Discussion : The stabilization efficiency for arsenic and heavy metals was in the order of natural -#10 mesh < natural -#20 mesh < calcined -#10 mesh. The calcined stabilizer showed a high stabilization efficiency of 98% at a 2 wt% treatment level. Pb was not detected in the red lettuce grown in the stabiliz ed soil, and the standard for leafy vegetables (Pb-0.3 mg/kg or less) was satisfied according to the Ministry of Food and Drug Safety. The SEM-EDX analysis revealed that As was stabilized through Ca-As precipitation and heavy metals(Pb, Zn) were stabilized through pozzolanic reactions.Conclusion : Stabilizers developed from MS and MC can be effectively applied to the stabilization of As and heavy metal-contaminated soil, and are expected to be used as economical and environmentally friendly stabilizers.

The effect of thermal aging on microhardness and SEM/EDS for characterisation bioactive filling materials

BackgroundThe aim of this study is to evaluate the surface microhardness, surface chemical composition of bioactive restorative materials pre- and post- thermal aging.MethodA total of 200 disc-shaped samples were prepared by using the materials: Cention N, ACTIVA BioActive Restorative, Equia Forte HT Fil, Glass Fill glass carbomer cement (GCP), and Fuji II LC. Vickers microhardness test were used to measure surface hardness. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM/EDS) was used to determine the characterization of the microstructures and elemental analysis of the materials. These measurements were repeated after thermal aging. One-Way ANOVA test, Bonferroni test and the Games-Howell test was used for data analysis. The significance level was accepted as 0.05.ResultsCention N had the highest vickers microhardness value before thermal cycle. The highest fluoride ion ratio among the materials before thermal aging was detected in the Equia Forte HT Fil and Fuji II LC groups. While a decrease in fluorideF ion was detected in all groups except the Cention N group after thermal aging. It is observed that ACTIVA BioActive Restorative has a more microporous and rougher surface in the scanning electron microscopy image after the thermal cycle than in the image before the thermal cycle.ConclusionsThe chemical properties of the materials and the properties of the filler particles may be related to the differences in the mechanical properties, surface characterizations and ion releases of the materials Thermal aging affected the microhardness, surface characteristics and elemental mass ratios of the studied materials. Alkasite bioactive materials are more similar to composite restorative materials and show better mechanical properties than other materials, but do not have the same effect on fluoride release.Clinical relevanceMost of the bioactive materials showed a decrease in the fluoride ion ratio after thermal aging, while no difference was found in the ion exchange of alkasite materials. Material selection should be made more carefully in caries-active individuals whose fluoride release is clinically important.

Chemical composition, mutagenicity, and cytotoxicity of urban submicron particulate matter (PM1) in Agra, India

This study, conducted in Agra, India, examined the mass concentrations, chemical compositions, and seasonal variations of submicron particles (PM1). The concentrations of metals, water-soluble inorganic ions (WSIs) including anions (F−, Cl−, NO₃−, SO₄2−) and cations (Ca2+, K+, Mg2+, NH₄+, Na+), organic carbon (OC) and elemental carbon (EC) and polycyclic aromatic hydrocarbons (PAHs) in PM1 extract were determined using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), Ion Chromatography, Thermogravimetric Analysis and Gas Chromatography-Mass Spectrometry (GC–MS) respectively. For morphological observation of PM1 particles, Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray spectrometry (FESEM-EDS) was used. The annual average concentration of PM1 was 82.9 ± 33.4 μg/m3, which exceeds the World Health Organisation's (WHO) safe limit for PM2.5 of 5 μg/m3 by a factor of 17. The PM1 mass composition included metals (31 %), WSIs (28 %), OC and EC (9.8 %), and PAHs (0.4 %). Winter recorded the highest PM1 concentration (96.1 ± 25.8 μg/m3), followed by post-monsoon, summer, and monsoon seasons. The average concentration of PAHs was 364.6 ± 226.6 ng/m3. Positive Matrix Factorization (PMF) identified traffic, emissions from biomass/coal and wood combustion, industrial/stationary sources, and secondary aerosols as potential contributors. The Ames test revealed the presence of frameshift mutations and base pair substitutions, especially in winter and post-monsoon. Additionally, PM1 exhibited cytotoxic effects on V-79 cells, with heightened toxicity during winter and prolonged exposure in other seasons. This study underscores the urgent need to address local emission sources and establish regulatory standards for PM1 in urban areas.

Impregnation Effect of Synthesized Fe3O4 Nanoparticles on the Jabon Wood’s Physical Properties

This study focused on characterizing synthetic magnetite (Fe3O4-NP) and evaluating the impregnated jabon wood’s physical properties. The co-precipitation method used for the synthesis of Fe3O4-NP, namely by mixing the iron solution (n/n Fe2+:Fe3+=1:2) with the strong base of sodium hydroxide (NaOH) (MG-S) and weak base of ammonium hydroxide (NH4OH) (MG-W) as precursors. The impregnation stage uses parameters of a -0.5 bar vacuum for half an hour and 2 bar pressure for 2 hours with magnetite concentrations of 1; 2.5; 5% w/v in a demineralized water solvent. Scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) and Fourier transform infrared spectrometry (FTIR) confirmed the presence of Ferrum content and Fe-O functional group in both Fe3O4-NPs produced. The Fe3O4-NP size was also measured via the X-ray diffraction analysis, namely 34.54 nm for the MG-S and 39.24 nm for the MG-W. Magnetic strength obtained was 7.51 mT for the MG-S and 8.58 mT for the MG-W. The impregnated jabon wood’s physical properties also improved with indications of an increase in wood density, weight percent gain (WPG), bulking effect (BE), anti-swelling efficiency (ASE), and a decrease in water absorption (WA). The results showed the best treatments were MG-S 2.5% and MG-W 5%.

Effects of irradiation on interfacial strength and microstructure of double-layer mullite and alumina coating on SiC

Silicon carbide (SiC) ceramics hold great potential for use in nuclear-reactor components due to characteristics such as high-temperature strength and low activation. Despite their resistance against corrosion in harsh environments, they suffer elevated corrosion rates under particle irradiation. Thin anti-corrosion coatings, such as mullite bond layers and alumina top layers, are essential to enhance the irradiation stability of SiC. The objective of this study was to evaluate the irradiation stability of a double-layer coating developed to enhance the corrosion resistance of SiC in nuclear applications. The coating, which comprised a mullite bond layer and an alumina top layer, was applied to a SiC substrate using laser chemical vapor deposition. Irradiation experiments were conducted at 300 °C with 5.1-MeV Si ions up to 10 displacements per atom. To assess the interfacial strength, a novel testing method, called the double-notch shear compression testing method, was developed based on ASTM standards and was implemented using a nanoindenter. This approach enabled precise measurements of the mechanical integrity at the interfaces of the coating under irradiation. The results showed an increase in the interfacial strength at the SiC/mullite and alumina/mullite interfaces with irradiation. Microstructural analysis of the fracture surface through scanning electron microscopy–energy-dispersive X-ray spectroscopy revealed that cracks propagated within the mullite layer, indicating the presence of mullite on the fracture surface. Transmission electron microscopy (TEM) images indicated that a 2-µm-thick transition layer existed at the SiC/mullite interface but not at the alumina/mullite interface. The TEM–electron energy loss spectroscopy suggested that the Al-O bonding structures in the transition layer were changed from tetrahedral (AlO4) to octahedral (AlO6) through irradiation, and this structural transition may directly affect the strength.

Construction of MIL-100(Fe)-DMA material for efficient adsorption of Sr and Cs ions from radioactive wastewater

A novel metal-organic framework (MOF) material, MIL-100(Fe)-DMA, was synthesized using the solvothermal method. The structure of the MOF was characterized using scanning electron microscopy-energy dispersive X-ray spectroscopy, N2 adsorption–desorption isotherms, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy. Batch adsorption experiments were performed to investigate the effects of initial Sr2+ and Cs+ concentrations, adsorption time, pH, and coexisting cations on the adsorption performance of the material. The adsorption mechanism was further elucidated using adsorption kinetics and isotherm models. The results indicated that the adsorption of Sr2+ and Cs+ does not significantly affect the MOF material structure. As reaction time and initial ion concentration increased, the adsorption capacity of MIL-100(Fe)-DMA for Sr2+ and Cs+ increased rapidly and then gradually reached equilibrium. Optimal adsorption occurred under alkaline conditions, with maximum adsorption capacity observed at pH = 8. The adsorption process for Sr2+ and Cs+ was well described by the pseudo-second-order kinetic model, the Weber–Morris model, and the Langmuir adsorption isothermal model. The adsorption process was mainly identified as monolayer chemical adsorption, influenced by multiple factors. Characterization combined with density functional theory calculations revealed that the unsaturated carboxylic acid groups on the surface of the MOFs play a crucial role in the interaction with Sr2+ and Cs+.

Investigation of tool traverse speed on surface integrity of nano composites processed by friction stir process

This work examines the effects of different tool traverse speeds on the surface integrity of AA7075 reinforced with graphene oxide (GO), silicon carbide (SiC) and graphene nanoplatelets (GNPs) nanoparticles during Friction Stir Processing (FSP). Three different traverse speeds of 20, 25 and 30 mm/min, respectively, were used for FSP operations. The resulting nanocomposites were thoroughly analysed using methods including optical microscopy, tensile testing, fracture morphology analysis, microhardness testing, X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (FESEM-EDAX) and non-contact surface interferometry. The results show that the creation of a refined microstructure with equiaxed grains was aided by tool traverse speeds between 20 and 25 mm/min. Notably, an Ultimate Tensile Strength (UTS) of 358 MPa, microhardness of 139 HV, refined crystalline size of 47.162 nm and average roughness (Ra) of 1.53 μm were obtained with the AA7075+SiC nanocomposite under tool traverse speed of 25 mm/min. On the contrary, surface layer defects developed at a traversal speed of 30 mm/min. Through the use of mechanical stirring and severe plastic deformation (SPD), this study aids in changing the microstructure of the airplane frames.

Structural, morphological, and chemical composition of ternary ZrHfN thin films deposited by reactive co-magnetron sputtering

This study focuses on a deposited ternary zirconium hafnium nitride (ZrHfN) thin film prepared using the reactive co-magnetron sputtering technique. The effect of the nitrogen (N2) flow rate on the films' structural, morphological, and chemical composition was investigated. The gracing-incidence X-ray diffraction (GIXRD) showed that all ZrHfN thin films exhibited a crystalline face-centered cubic structure with a strong (111) orientation. With increasing the N2 flow rate, the film's crystallography changed based on thermodynamic theory. The films demonstrated uniformity and homogeneity in their ternary nitride composition, as confirmed by transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) mapping and electron probe microanalyzer (EPMA). Chemical state analysis using X-ray photoelectron spectroscopy (XPS) indicated the presence of both nitride and oxynitride species in all samples. Notably, the atomic concentration of the main elements (Zr, Hf, and N) remained relatively stable over the controlled N2 flow rate range. However, the N2 flow rate played a crucial role in forming hafnium nitride and oxynitride chemical states, whereas it did not significantly influence the Zr phases, dominated by Zr oxides. Additionally, the hardness of the ternary ZrHfN thin films exhibited enhancement comparable to typical ternary nitrides.

Characterization of field emission from oxidized copper emitters

In this work, the field electron emission from oxidized copper emitters was studied by aging with radii in the range of 80–300 nm. The samples were prepared by an electrochemical etching method using an H3PO4 solution. The samples were exposed to air for 30 d to form an oxide film owing to aging. Measurements were carried out under high vacuum conditions in the range of 10−6 mbar. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM- EDS) was used to calculate the emitter radius, study the purity of the samples, and detect the oxide layers. Current–voltage (I-V) characteristics were studied and analyzed using Murphy-Goode (MG) plots and rectification tests. Furthermore, the spatial distribution of the electron emission and current stability were recorded and used to analyze the electron emission behavior of the tip surface. The trap density was also studied when the oxide layer was 3 layers thick. The results show that the emitters passed the orthodoxy test at low voltages. It was found that traps play an important role in increasing the switch-on current as the area of the oxide layer increases. It was found that the emitter acts as a point capacitor based on the charging and discharging processes of the electrons in the traps. The emission pattern showed great stability, which opens up prospects for this type of emitter in industry.

Poly(ionic liquids-acrylic acid)-modified MIL-101(Cr) metal−organic frameworks: Preparation and efficient adsorption of europium☆

A novel composite material, Poly(IL-AA)@MIL-101(Cr), combining metal-organic framework, polymeric ionic liquid and acrylic acid, was synthesized for the selective and efficient adsorption of rare earths europium(III) (Eu3+). Characterization of the materials was carried out using techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET). The results demonstrate successful incorporation of the polymeric ionic liquid onto the material surface while preserving the crystal structure and morphology of MIL-101(Cr). Adsorption experiments were conducted to explore parameters including solution pH, initial Eu3+ concentration, and duration, with comprehensive analyses of adsorption kinetics, isotherms, and mechanisms. Findings reveal that Poly(IL1-AA)@MIL-101(Cr), Poly(IL3-AA)@MIL-101(Cr), and Poly(IL5-AA)@MIL-101(Cr) achieve adsorption equilibrium for Eu3+ at approximately 9 h with an equilibrium pH of 6.2. The adsorption of Eu3+ predominantly follows a pseudo-second-order kinetic model and Langmuir isotherm adsorption model. Moreover, the prepared composite material exhibits superior adsorption selectivity for Eu3+ over other metal ions in the mixture (K+, Mg2+, Ni2+, Co2+, Zn2+, La3+, and Nd3+). Even after five adsorption-desorption cycles, the composite material maintains satisfactory adsorption performance.

Enhancing CO2 Transport Across the PEG/PPG-Based Crosslinked Rubbery Polymer Membranes with a Sterically Bulky Carbazole-Based ROMP Comonomer.

A series of poly(ethylene glycol)-block-poly(propylene glycol) (PEG/PPG)- and 5,6-di(9H-carbazol-9-yl)isoindoline-1,3-dione (2CZPImide)-based crosslinked rubbery polymer membranes, denoted as PEG/PPG-2CZPImide (x:y), are prepared from the norbornene-functionalized PEG/PPG oligomer (NB-PEG/PPG-NB) and 2-(bicyclo[2.2.1]hept-5-en-2-ylmethyl)-5,6-di(9H-carbazol-9-yl)isoindoline-1,3-dione (2CZPImide-NB) via ring-opening metathesis polymerization (ROMP). The molar ratio (x:y) of the NB-PEG/PPG-NB (x) to 2CZPImide-NB (y) monomers is varied from 10:1 to 6:1. X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and pure gas permeability studies reveal that the comonomer 2CZPImide-NB successfully increases the d-spacing among the crystalline PEG/PPG segments, hence enhancing the diffusivity of gases through the membranes. The synthesized membranes exhibit good CO2 separation performance, with CO2 permeabilities ranging from 311.1 to 418.1 Barrer and CO2/N2 and CO2/CH4 selectivities of 39.4-52.0 and 13.4-16.0, respectively, approaching the 2008 Robeson upper bound. Moreover, PEG/PPG-2CZPImide (6:1), displaying optimal CO2 permeability and CO2/N2 and CO2/CH4 selectivities, shows long-term stability against physical aging and plasticization resistance up to 20 days and 10 atm, respectively.

Mineralogical and leaching characteristics of sulfur concentrate and hot filter residue from zinc–oxygen-pressure leaching

The mineralogical properties and environmental impact of sulfur concentrate and hot filter residue produced from the zinc–oxygen-pressure leaching were studied through a series of characterization, including X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP–OES), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM–EDS), particle size distribution (PSD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermogravimetry and differential thermal analysis (TG–DTA). Furthermore, short-term environmental activity was assessed using the toxic leaching procedure (TCLP). The results indicated that the sulfur concentrate exhibited a coarser particle size compared with the hot filter residue, primarily appearing as spindle-shaped element sulfur (S0). The hot filter residue contained spindle-shaped S0 and rod gypsum, alongside phases of sphalerite, pyrite, and copper–silver-containing phases encapsulated by S0, recovering valuable metals first requires the removal of S0. The surfaces of both sulfur concentrate and hot filter residue were composed of S, ZnS, Al-O, PbSO4, and SiO2. They exhibited thermal instability and some degree of water absorption, with vigorous burning observed at temperatures ranging from 200 °C to 380 °C. The leachates from these materials exhibited increased concentrations of elements such as zinc, lead, and cadmium surpassing permissible limits, highlighting the importance of their safe disposal for the stable production of zinc–oxygen-pressure systems.

Phase evolution and heavy metal solidification of cement desulphurized electrolytic manganese residue composite cementitious system under steam curing conditions based on thermodynamic simulation

The mechanical properties and microstructure of desulphurized electrolytic manganese (D-EMR) cement mortar under steam curing at 80 °C for 7 h and 7 days and standard curing for 3 days and 28 days were studied. The hydration products, microstructure and pore distribution were studied by Quantitative X-ray diffraction analysis (QXRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric-differential thermal analysis (TG-DTA) and backscattered electron (BSE). At the same time, the evolution of hydration products with age and the existence form of heavy metals under different curing conditions were simulated by GEMS thermodynamics. The results show that steam curing can promote the hydration reaction of cement and the secondary hydration of D-EMR. With the extension of steam curing time, the mechanical properties of the early stage are significantly improved. At a D-EMR content of 15 %, the compressive strength of D-EMR cement mortar after steam curing for 7 days is 1.15 times that of the control group under the same conditions, and the content of calcium hydroxide (CH) is 65.91 % of the control group. Steam curing can significantly improve the degree of C3S hydration of cement clinker and the secondary hydration of D-EMR, and increase the degree of polymerization of hydrated calcium silicate (C-S-H) gel. In addition, thermodynamic simulation showed that when the pH value was greater than 7.5, Mn2+ was mainly stable in the form of Mn(OH)2, MnOOH and Mn3O4, and there was no leaching risk. This will provide theoretical support for the use of D-EMR as a new type of supplementary cementitious material (SCM).

Electrokinetic in situ leaching of U from low-permeability uranium ore

In this study, the impacts of electrokinetic in situ leaching of uranium (EK-ISLU) on the pore structure and connectivity of the low-permeability uranium ore and its leaching efficiency were investigated. Our results demonstrated that a direct current field with an intensity of 7.5 V/cm increased the porosity by 7.07 % and enhanced the uranium leaching efficiency by 73.73 % using a sulfuric acid solution. Under electrical stimulation, the leaching agent exhibited uniform penetration ability through combined electromigration and electroosmosis effects, significantly improving the directed migration of the target ions. Various characterization techniques, such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), three-dimensional computed tomography (CT) pore scanning and Brunauer-Emmett-Teller (BET), showed that the electrokinetic-induced action overcame the preferential flow phenomena, promoted the dissolution of the target minerals and gangue rocks, and notably improved the pore structure to ultimately enhance the uranium leaching efficiency. Our results provide valuable insights for the development of innovative technologies aimed at efficiently recovering U from low-permeability uranium ores.

Contrasting shell thickness-dependent magnetic behaviors of CoFe2O4@Fe3O4 and Fe3O4@CoFe2O4 core/shell nanoparticles

The magnetic properties of bi-magnetic core/shell nanoparticles (NPs) have been a subject of extensive investigation. Yet, the role of shell thickness in hard/soft and soft/hard core/shell NPs, corresponding to conventional and inverse structures, remains incompletely elucidated. In this study, we synthesized two sets of core/shell NPs, namely Fe3O4@CoFe2O4 (IF@CF) and CoFe2O4@Fe3O4 (CF@IF), featuring a fixed core diameter of approximately 11 nm and varying shell thicknesses up to 5 nm. These NPs were synthesized via a seed-mediated particle growth approach. The formation of the core/shell configuration of typical NPs in both sets was directly verified through scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS) imaging. Notably, the saturation magnetization (MS) of IF@CF NPs exhibited a significant increase compared to that of the IF core across all shell thickness variations, whereas it remained largely unchanged for CF core and CF@IF NPs. Conversely, the coercivity (HC) showed an opposite trend in the two structures with increasing shell thickness. We observed the emergence of a transition from constricted to smooth hysteresis loops in the conventional structure when the shell thickness reached 5 nm. The systematic evolution of hysteresis loops with escalating shell thickness in both structures closely correlates with distinct magnetic reversal mechanisms, influenced significantly by interparticle interactions. Our study presents a pathway for modulating the magnetic properties of bi-magnetic core/shell NPs, thereby opening avenues for advanced applications in magnetic imaging, sensing, drug delivery, and magnetic hyperthermia.