Scanning Electron Microscopy And Energy Dispersive Spectroscopy Research Articles

α/β-TCP silicate glass-ceramic obtained by sol–gel: Structure and in vitro bioactivity

A glass-ceramic in the CaO–P2O5–SiO2 system, which contains two polymorphic modifications of tricalcium phosphate – whitlockite, β-Ca3(PO4)2 and α-Ca3(PO4)2, has been synthesized by the sol–gel method and thermal treatment up to 1200°C. The phase composition and microstructure of the glass-ceramic were investigated with X-ray diffraction analysis (XRD), Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). An in vitro bioactivity test of the glass-ceramic in a simulated body fluid (SBF) was conducted for up to 21 days. α-Ca3(PO4) dissolved almost completely in SBF after 7 days. The experimental results of XRD, FTIR, SEM and EDS clearly validated the ability of the glass-ceramic samples to form a layer of hydroxyapatite on their surface in an SBF environment. We also studied the cytotoxic effect of the glass-ceramic on murine bone marrow (BM) cells and pre-osteoclasts in vitro. The glass-ceramic reduced the viability of BM cells in a dose-dependent manner being less toxic at concentrations below 0.1mg/ml. It modestly affected the viability of pre-osteoclasts cultured in osteoclast differentiation media. The obtained sample increased the percentage of pre-osteoclasts expressing the receptors involved in osteoclastogenesis (RANK) and apoptosis (TRAIL). In conclusion, the glass-ceramic showed the potential to affect the survival/differentiation of pre-osteoclasts at early stage of osteoclastogenesis. It might be suitable for tissue engineering including implants coating or scaffold as it can interfere with early stage of osteoclastogenesis which is required for proper bone remodelling and repair upon a long-term application of biomaterials.

Carboxymethyl Scleroglucan Synthesized via O-Alkylation Reaction with Different Degrees of Substitution: Rheology and Thermal Stability.

This paper presents the methodology for synthesizing and characterizing two carboxymethyl EOR-grade Scleroglucans (CMS-A and CMS-B). An O-Alkylation reaction was used to insert a hydrophilic group (monochloroacetic acid-MCAA) into the biopolymer's anhydroglucose subunits (AGUs). The effect of the degree of the carboxymethyl substitution on the rheology and thermal stability of the Scleroglucan (SG) was also evaluated. Simultaneous thermal analysis (STA/TGA-DSC), differential scanning calorimetry (DSC), X-ray Diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning Electron Microscopy, and Energy Dispersive Spectroscopy (SEM/EDS) were employed to characterize both CMS products. FTIR analysis revealed characteristic peaks corresponding to the carboxymethyl functional groups, confirming the modification. Also, SEM analysis provided insights into the structural changes in the polysaccharide after the O-Alkylation reaction. TGA results showed that the carboxymethylation of SG lowered its dehydroxylation temperature but increased its thermal stability above 300 °C. The CMS products and SG exhibited a pseudoplastic behavior; however, lower shear viscosities and relaxation times were observed for the CMS products due to the breakage of the SG triple helix for the chemical modification. Despite the viscosity results, the modified Scleroglucans are promising candidates for developing new engineering materials for EOR processes.

Sintered magnesium ferrite particles in decolorization of anthraquinone dye AV 109: Combination of adsorption and fenton process

Magnesium ferrite (MgFe2O4) particles were synthetized by sol-gel method and used in the decolorization of the Acid Violet 109 (anthraquinone dye, AV109) water solutions' by combination of adsorption and heterogeneous Fenton process. The material's morphology and elemental analysis of the surface were revealed by Scanning electron microscopy and Energy Dispersive Spectroscopy (SEM/EDS). The X-Ray Diffraction (XRD) technique was used to analyze the crystallographic phase. In the first part of the decolorization experiment, the adsorption ability of the synthesized particles was investigated. During the adsorption study influence of pH was investigated. In the second part of the decolorization experiment, the effects of the various parameters on the Fenton process were studied such as the initial concentrations of hydrogen peroxide, dye, and magnesium ferrite particles. Influence of magnesium ferrite particles structure, pH value and reaction temperature were also investigated. The decolorization reaction was followed by UV-Visible (UV-Vis) spectrophotometry. At optimal conditions, the dye decolorization was 99.1% (55.4% by adsorption and 43.7% by the Fenton process). Both the adsorption and the Fenton process obey second-order kinetics.

Sintered magnesium ferrite particles in decolorization of anthraquinone dye AV109: Combination of adsorption and fenton process

Magnesium ferrite (MgFe2O4) particles were synthetized by sol-gel method and used in the decolorization of the Acid Violet 109 (anthraquinone dye, AV109) water solutions' by combination of adsorption and heterogeneous Fenton process. The material's morphology and elemental analysis of the surface were revealed by Scanning electron microscopy and Energy Dispersive Spectroscopy (SEM/EDS). The X-Ray Diffraction (XRD) technique was used to analyze the crystallographic phase. In the first part of the decolorization experiment, the adsorption ability of the synthesized particles was investigated. During the adsorption study influence of pH was investigated. In the second part of the decolorization experiment, the effects of the various parameters on the Fenton process were studied such as the initial concentrations of hydrogen peroxide, dye, and magnesium ferrite particles. Influence of magnesium ferrite particles structure, pH value and reaction temperature were also investigated. The decolorization reaction was followed by UV-Visible (UV-Vis) spectrophotometry. At optimal conditions, the dye decolorization was 99.1% (55.4% by adsorption and 43.7% by the Fenton process). Both the adsorption and the Fenton process obey second-order kinetics.

Preparation of alkali-activated nickel slag-based cemented tailings backfill: Workability, strength characteristics, localized deformation and hydration mechanism

To solve the problems of high magnesium nickel slag (HMNS) and tailing stacks with large storage and environmental pollution, alkali-activated HMNS-based cementitious materials were prepared by using NaOH, phosphogypsum (PG), HMNS and ground granulated blast furnace slag (GGBFS), and cemented tailings backfill (CTB) was prepared using tailings as aggregates. The workability, strength characteristics, localized deformation and hydration mechanism of CTB were studied. Based on the digital speckle correlation method (DSCM), the localized deformation of CTB was analyzed. The hydration mechanism of CTB was analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry-differential scanning calorimetry (TGDSC), mercury intrusion porosimetry (MIP) and scanning electron microscopy and energy dispersive spectroscopy (SEMEDS). The results showed that the optimal mix proportions for the cementitious material were 8%, 30%, 6%, and 0.38 for PG content, GGBFS content, alkali dosage, and water/binder ratio, respectively. The best performance of CTB was achieved when the bone glue ratio (BGR) and mass concentration (MC) were 5:1 and 79%, respectively; the slump, slump flow, and consistency of CTB decreased continuously with increasing BGR and MC; the layering degree, bleeding rate, and linear shrinkage of CTB continuously increased with increasing BGR, and decreased with increasing MC; the unconfined compressive strength of CTB increased with increasing maintenance age and MC and decreased with increasing BGR; when the BGR was small (3:1), CTB exhibited shear failure, and when the BGR was large (6:1), CTB exhibited tensile failure. The main hydration products of CTB were C-S-H gel, M-S-H gel, ettringite (AFt), Ca(OH)2 and CaCO3. In the early stage of curing, CTB has more pores, fewer hydration products and a relatively loose internal structure, flocculation, sheet, network and needle rod hydration products coated tailing particles, porosity decreased, and CTB became dense.

The beneficial reuse of contaminated sediment: Long-term assessment of fly ash and lime-based mixtures

In recent decades, sediment has been recognised as a problematic resource due to its potentially harmful effects and the large quantities present in water bodies. There is a need to properly manage large quantities of dredged sediments so that they can be used as a resource and not necessarily treated as a waste product. This research investigates the effects of ageing and maturation of solidified/stabilized mixtures of contaminated sediment with fly ash and lime. The effects of ageing on the microstructural properties and chemical integrity of mixtures were studied for 7 days, 28 days, and 7 years using scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), X-ray diffraction analysis (XRD), and DIN (German Standard Procedure for Water, Wastewater and Sediment Testing (Group S)) and TCLP (Toxicity Characteristic Leaching Procedure) leaching tests. The results of the microstructure and strength analysis showed that the use of fly ash and lime as binders promoted the permanent structural integrity of the sediment. The treated sediment with 20 wt% fly ash and 10 wt% lime (F20L10) achieved higher overall strength compared to the mixture containing only 30 wt% fly ash (F30). The speciation and redistribution of metals and As in the treated sediment mixtures during the long-term evaluation indicate a strong reduction in their mobility. This material can be considered environmentally friendly and can be used as a fill material in road construction. The investment and operating costs are justified in this solution for sediment management. However, it is important to monitor the produced material over time to ensure that it remains effective and sustainable in the long term.

A novel polymer coated magnetic activated biochar-zeolite composite for adsorption of polystyrene microplastics: Synthesis, characterization, adsorption and regeneration performance

A magnetic activated biochar-zeolite composite (MACZ) was produced and coated with polyethyleneglycol (PEG) and polyethylenimine (PEI) to produce (PMACZ) and enhance its electrostatic properties for the adsorption of 2 µm and 15 µm microplastics. Produced adsorbents were characterized with scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), Brunauer-Emmett-Teller (BET), zeta sizer, vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Equilibrium and kinetic laboratory tests were conducted to evaluate the adsorption behaviour. A response surface analysis (RSM) was conducted on a central composite design to evaluate the effects of pH and temperature on adsorption. Zeta potential results showed PEG/PEI can induce positive charges on adsorbents. Adsorption kinetic followed a pseudo-second-order model with R2 of 99 %. The results of isotherm studies indicated a correlation with the Temkin model with a maximum R2 of 98 %. The results showed a maximum adsorption capacity of 736 mg/g and 769 mg/g for PMACZ on 2 µm and 15 µm microplastic, respectively. Optimization results indicated a pH of 4 and a temperature of 28 and 24 for maximum adsorption of 2 µm and 15 µm microplastics. ANOVA analysis showed pH has a higher impact on adsorption. The produced material can be regenerated for a minimum of 4 cycles. Also the effect of ion matrixes, sea salt, tap water and waste water effluent on adsorption of MACZ and PMACZ has been investigated.

Study on the effect of structural sodium dissolution on the physical properties of red mud treated by sulfuric acid

Red mud is a strong alkaline solid waste produced by the alumina industry. Although it has found frequent use in building applications, its sodium content causes unwanted effects like “Frost”, demanding the removal of Na+ from red mud. Effective removal of Na+ can result in improving the performance of red mud as a material and increase its applicability. However, the removal of Na+ remains a key problem that needs to be addressed. In this paper, a comprehensive and systematic study has been carried out on the commonly used method of sulfuric acid dealkalization and its influence on the physical properties of red mud has been investigated. The variation of mineral phase content species in red mud and the mechanism of Na+ removal during acid leaching has been studied by regulating the sulfuric acid concentration. The red mud residues have been characterized using a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and Brunauer Emmett Teller (BET) based on nitrogen adsorption–desorption. The results show that the Na+ leaching yield gradually increases with the increase in sulfuric acid concentration. Further, the Na-H, Na-O, Si-O, and Ca-O bonds in the main Na+ assigned mineral phase cancrinite are broken in a certain order based on the differences of bond energies at different acid concentrations. The results of this study can help to successfully address the issue of treatment of Na+ in bauxite slag and lessen the environmental contamination brought on by the subsequent discharge of waste liquid. Additionally, after treatment, the discharged waste liquid might be converted into usable products. The findings of this work have crucial implications for future-focused research in addition to offering a plausible pathway for ion alterations throughout the red mud dealkalization process.

Micromechanical Contrast of Ordos Basin Sandstone‐Mudstone Interbedded Layered Rocks

AbstractLayered rocks are heterogeneous media composed of multiscale minerals with contrasting geomechanical properties. It remains unclear how the mechanical responses of constituent minerals among different adjacent layers vary in a microscale. Based on the grid nanoindentation tests assisted by high‐resolution scanning electron microscopy and energy‐dispersive spectroscopy techniques, we quantified the mechanical responses of various minerals in an interbedded sandstone‐mudstone core sample and provided visual mineralogies and indentation patterns of different adjacent layers. Results show that the Young's modulus, hardness, and elasticity index of quartz and dolomite decrease, whereas their fracture toughness and plastic work ratio increase from the sandstone layer to the mudstone layer. Quartz displays elastic‐dominated deformations in the sandstone layer whereas transforms into medium‐plastic deformations in the mudstone layer. The mean values of Young's modulus, hardness, and elasticity index of quartz in the sandstone layer are 1.28, 2.00, and 1.56 times higher than that in the mudstone layer, respectively. Dolomite and phyllosilicate minerals show prominently plastic‐dominated deformations in each layer. When an indenter encounters multiple minerals simultaneously, the mechanical responses are determined by the softer phases and irregular indent impressions are generated. Shear and radical cracks are prone to occur in the elastic‐dominated minerals, while chipping damage is induced in the plastic‐dominated minerals. This work provides new insights and fundamental understandings in geomechanical properties contrasts in multilayered rocks, and can facilitate the geomechanical modeling and upscaling schemes in multilayered formations.

Enhancement of magnetization roasting of hematite ore by high voltage pulse discharge

High voltage pulse discharge (HVPD) is a new type of crushing technology with good application. Existing studies have focused on the crushing characteristics, with less reports on follow-up work. This study magnetization roasts hematite ore after mechanical crushing and HVPD, analyzing the difference in the roasting effect between the two crushing methods by establishing a new system of HVPD-magnetization roasting. For a roasting temperature of 500 °C, roasting time of 30 min and number of pulses of 100 times, the grade and recovery of magnetic separation concentrate obtained from HVPD products after secondary separation were 64.69% and 82.05% respectively, which were 0.28 and 1.96 percentage higher than those of mechanical crushing. X-ray diffraction (XRD), vibrating sample magnetometry (VSM), Brunauer-Emmett-Teller (BET), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) were used to analyze the process and showed that the specific surface area, pore volume and average pore size of the HVPD products were improved. Grain boundary fracture and burn marks were present in the HVPD products.

Alternating Current Electrolytic Extraction of Transition Metals from NMC532 using Rotating Disc Cyclic Voltammetry in Dilute Chloride Solution

The rising application of portable electric devices has led to the rapid accumulation of electronic wastes such as lithium-ion batteries. These wastes pose significant environmental threats when improperly disposed of and contain valuable metals that could supplement the supply chain and reduce the need for certain conflict minerals. Recycling methods that limit the potential for environmental damage and improve separation of transition metals are vital to the sustainability of battery based electrical storage. Conventional aqueous recycling of lithium battery electrode materials utilizes oxidizing acids and a chemical reducing agent. This study investigates if chemical oxidizing and reducing agents may be aided or replaced by the application of an alternating electric field to reduce surface metal oxides and subsequently accelerate reoxidation with a solubilizing anion. The electrolytic leaching mechanics of commercial battery cathode material (NMC532) in dilute hydrochloric acid were investigated using rotating disc cyclic voltammetry (RDE-CV), solution analysis with inductively coupled plasma mass spectrometry (ICP-MS), and residue analysis with scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). We found evidence that applying an alternating electric field allows for adjustment of leaching rates for different transition metals based on electrochemical cell parameters. By applying up to one volt oscillating between reducing and oxidizing polarity, the relative molar leaching rate of nickel and manganese drastically increased while that of cobalt slightly decreased. Future research will be required to determine how this effect translates to different leaching systems and its applicability to an industrial scale process.The authors acknowledge financial support from the NSF IUCRC program for the “Center for solid-state electric power storage” (#2052631) and support from the South Dakota Board of Regents for the “Governor’s Research Center (GRC) for electrochemical energy storage”.

Effect of sulfuric acid pretreatment on flotation performance of calcite and fluorite

Difficulty in separating calcite and fluorite owing to their similar surface properties is the focus of research in the field of mineral processing. To increase the selectivity difference between these two minerals, sulfuric acid was introduced as a surface pretreatmentand, and aluminium sulfate was used as the flotation depressant. The effects of H2SO4 pretreatment on calcite and fluorite flotation performance and the mechanisms thereof were studied by combining microflotation experiments, solution chemical calculations, scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy, and density functional theory (DFT). Microflotation experiments showed that sulfuric acid pretreatment significantly reduced the flotation recovery of calcite to less than 10%, while it had little effect on fluorite, where the recovery reached greater than 80%. SEM-EDS and FT-IR analyses showed that, after sulfuric acid treatment, the surface composition of calcite was converted from CaCO3 to CaSO4, while the fluorite surface remained almost unchanged. DFT calculations showed that CaSO4 was more hydrophilic than CaCO3; therefore, it was more likely to interact with water molecules. The presence of water molecules affected the adsorption of the sodium oleate (NaOL) collector on the mineral surface. Therefore, the calcite surface adsorption ability of NaOL after sulfuric acid pretreatment was weakened, resulting in a significant decrease in flotation recovery.

Separation of lanthanides erbium and ytterbium on indium electrodes by modulated potential selective extraction in molten salts and a thermodynamic and kinetic analysis of the process

The main purpose of this paper is to study the extraction and separation of key fragment elements based on the electrolytic refining process of spent fuel dry reprocessing. Firstly, the electrochemical mechanisms of Er(III) and Yb(III) in LiCl-KCl molten salts were investigated on W and In film electrodes with applied cyclic voltammetry (CV), square wave voltammetry (SWV) and open circuit potential (OCP) at 773 K. The results indicated that the reduction behaviour of In(III) and Yb(III) ions were a two-step transfer process and Er(III) ions was a one-step transfer process. Then, the kinetic parameters in electrochemical processes were calculated on an In electrode with different temperatures. The OCP approach was used to determine the equilibrium potential of Er(III)/Er(0) in the temperature range of 773 K∼848 K, and thermodynamic parameters of the In3Er alloy were provided. Based on electrochemical behaviour results, the electrochemical extraction of Er(III) and Yb(III) from LiCl-KCl-ErCl3 molten salts and LiCl-KCl-YbCl3 molten salts at liquid In electrodes was performed by constant potential and constant current electrolysis, respectively. The electrolysis products were determined by X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM-EDS), the primary intermetallic compounds generated in the alloys were In3Er and In3Yb. The average extraction rates for Er(III) and Yb(III) were 94.70% and 96.54%, respectively, according to inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis. Er(III) and Yb(III) were selectively extracted and separated from LiCl-KCl-ErCl3-YbCl3 molten salts by potentiostatic control on the basis of the previously studied Lns (Er and Yb) extraction on In electrodes. The separation rate of Er(III) and Yb(III) by electrochemical selective deposition was 94.21%.

Optimization of Microalgae Biomass Yield using Chlorella Sp. and Spirulina Sp. Cultivation in secondary treated wastewater effluent

Conventional method for domestic wastewater treatment could be inefficient due to active organic loadings and high population. Thus, the treated wastewater still contains high nutrient of nitrogen, phosphorus, and ammonia that can lead to the eutrophication and threaten biodiversity in long run. This study is aimed to concentrate on the capability of microalgae, Chlorella sp. and Spirulina sp. cultivated with secondary treated wastewater effluent for nutrients removal and biomass yield. The secondary treated wastewater effluent sample was collected and analysed the nutrient characterization of total nitrogen (TN = 2.78 mg/L) and total phosphorus (TP = 2.13 mg/L) using standard method by APHA. The optimization of the best dilution of secondary treated wastewater effluent and the microalgae ratio of Chlorella sp. and Spirulina sp. were run by Research Surface Methodology (RSM). The optimum results were found which 100% of Chlorella sp. mixed with 50% of Spirulina sp. cultivated with 70% of secondary treated wastewater effluent dilution. The highest results obtained from microalgae biomass yield was 0.22 g/L. While the NPK were analysed using scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) obtained 0.6 wt% and 0.3 wt% for phosphorus (P) and potassium (K) respectively. Subsequently, the potential traits as a biofertilizer was positively observed based on these responses. This study shows Chlorella sp. and Spirulina sp. was able to grow in wastewater and have ability to become biofertilizer with phosphorus and potassium content.

38 Physicochemical Characterisation and Potential Health Effects of Tyre Wear Particles

Abstract Tyre wear is an increasing source of ambient particulate matter pollution in the UK and around the world. Currently, tyre wear accounts for 11% of total particulate matter (PM2.5) in the UK, and over the next 10 years that figure is projected to steadily increase, with UK brake and tyre emissions projected to reach 6 kilotonnes by 2030. Being able to reliably identify and monitor tyre wear PM in ambient sources is of increasing importance due to its potential human health effects. Here we present a series of characterisation experiments on tyre particles, size-fractionated using a dynamometer. Chemical and elemental composition has been determined by inductively coupled plasma mass spectrometry (ICP-MS) and two dimensional gas chromatography time of flight mass spectrometry (GCxGC-TOF-MS), with particle morphology studied using a scanning electron microscope and energy dispersive spectroscopy (SEM-EDS) and an electrical low pressure impactor (ELPI). The potential health effects of these particles have then been assessed in vitro using human bronchial epithelial cells following the IARC characteristics of carcinogenicity, specifically looking at (pro)inflammatory cytokines, cytotoxicity and mitochondrial function. Tyre wear particles have the ability to reduce mitochondrial function significantly from doses as low as 5μg/ml after 24 hours, with the induction of cytokines and chemokines currently being profiled. Additionally, a representative elemental and chemical fingerprint of tyre rubber has now been established. By understanding the composition and morphology of these particles, we can begin to detect them in atmospheric samples, and using in vitro models, understand their potential health effects.

Antagonistic impact on cadmium stress in alfalfa supplemented with nano-zinc oxide and biochar via upregulating metal detoxification.

Eco-toxicological estimation of cadmium induced damages by morpho-physiological and cellular response could be an insightful strategy to alleviate negative impact of Cd in agricultural crops. The current study revealed novel patterns of Cd-bioaccumulation and cellular mechanism opted by alfalfa to acquire Cd tolerance under various soil applied zinc oxide nanoparticles (nZnO) doses (0, 30, 60, 90mgkg-1), combined with 2% biochar (BC). Herein, the potential impact of these soil amendments was justified by decreased Cd and increased Zn-bioaccumulation into roots by 38 % and 48 % and shoots by51 % and 72 % respectively, with co-exposure of nZnO with BC. As, the transmission electron microscopy (TEM) and scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) ultrastructural observations confirmed that Cd-exposure induced stomatal closure, and caused damage to roots and leaves ultrastructure as compared to the control group. On the contrary, the damages to the above-mentioned traits were reversed by a higher nZnO dose, and the impact was further aggravated by adding BC along nZnO. Furthermore, higher nZnO and BC levels efficiently alleviated the Cd-mediated reductions in alfalfa biomass, antioxidant enzymatic response, and gaseous exchange traits than control. Overall, soil application of90mgkg-1 nZnO with BC (2 %) was impactful in averting Cd stress damages and ensuring better plant performance. Thereby, applying soil nZnO and BC emerge as promising green remediation techniques to enhance crop tolerance in Cd-polluted soil.

Comprehensive kinetic study for Fischer–Tropsch reaction over KMoFe/CNTs nano‐structured catalyst

AbstractThe kinetics of the Fischer–Tropsch (FT) reaction was evaluated through detailed experimentation with a KMo bimetallic promoted Fe catalyst supported on carbon nanotubes (CNTs). The kinetic tests were conducted in a fixed‐bed reactor under operating conditions of P = 6.9–41.3 bar, T = 543–563 K, H2/CO = 1, gas hourly specific velocity (GHSV) = 2000 h−1. This study aimed to investigate the mechanism prevailing in CO activation and the rate equation for CO consumption during FT reactions over a 0.5K5Mo10Fe/CNTs catalyst. To evaluate the synergistic effects of Fe, Mo, and K phases on the catalyst activity, both fresh and spent catalysts were thoroughly characterized using X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy and energy‐dispersive spectroscopy (SEM‐EDS), X‐ray absorption near edge structure (XANES), and extended X‐ray absorption fine structure (EXAFS) to ascertain the different phases (active sites) present and relevant interactions. Based on the adsorption of carbon monoxide and hydrogen, 22 possible mechanisms for monomer formation were proposed for FT synthesis in accordance with the Langmuir–Hinshelwood–Hougen–Watson (LHHW) and Eley–Rideal (ER) adsorption theories. The best fit kinetic model was identified through a multi‐variable non‐linear regression analysis. The selected mechanistic model was based on carbide formation approach, where H2‐assisted adsorption of CO was considered for the derivation. Kinetic parameters such as activation energy, adsorption enthalpies of H2, and CO were estimated to be 65.0, −13.0, and −54.0 kJ/mol, respectively. Considering the developed kinetic model, the effects of reaction temperature and pressure were assessed on Fischer–Tropsch synthesis (FTS) product distribution. Additionally, the kinetic model was compared with the typical Anderson–Schulz–Flory model, suggesting the effects of water‐gas‐shift and the existence of additional formation pathway such as secondary re‐adsorption of olefins for heavier hydrocarbons.

Mechanical Properties and Microstructure Analysis of Cement Mortar Mixed with Iron Ore Tailings

In order to study the feasibility and sand substitution mechanism of cement mortar mixed with iron ore tailings (IOT), iron ore tailings cement mortars (referred to as IOTC) with IOT content of 0%, 25%, and 50% were made and tested. First, the basic properties of IOT used were measured to verify the theoretical feasibility. Second, the uniaxial compressive and tensile strengths, as well as the crack resistance performance of IOTC under different curing ages and different sand substitution rates were tested. Third, the techniques of inductively coupled plasma atomic emission spectrometry (ICP-OES), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) were used to study the influence of curing age and different sand substitution rates on the chemical, mineralogical, and microstructural characteristics of IOTC. The sand substitution mechanism of IOT was then discussed. The research results proved the feasibility of using IOT to substitute standard sand in cement mortar. Within substitution rate of 0–50%, the mechanical properties increased with the increase of substitution rate. Though limited chemical effects were found by adding IOT, in comparison with standard sand mortar, more hydration products were found and the pore size distribution was changed for IOTC, which corresponds to its mechanical improvement.

Structure and Chemical Composition of ca. 10-Million-Year-Old (Late Miocene of Western Amazon) and Present-Day Teeth of Related Species.

Molecular information has been gathered from fossilized dental enamel, the best-preserved tissue of vertebrates. However, the association of morphological features with the possible mineral and organic information of this tissue is still poorly understood in the context of the emerging area of paleoproteomics. This study aims to compare the morphological features and chemical composition of dental enamel of extinct and extant terrestrial vertebrates of Crocodylia: Purussaurus sp. (extinct) and Melanosuchus niger (extant), and Rodentia: Neoepiblema sp. (extinct) and Hydrochoerus hydrochaeris (extant). To obtain structural and chemical data, superficial and internal enamel were analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (SEM-EDS). Organic, mineral, and water content were obtained using polarizing microscopy and microradiography on ground sections of four teeth, resulting in a higher organic volume than previously expected (up to 49%). It is observed that both modern and fossil tooth enamel exhibit the same major constituents: 36.7% Ca, 17.2% P, and 41% O, characteristic of hydroxyapatite. Additionally, 27 other elements were measured from superficial enamel by inductively coupled mass spectrometry (ICP-MS). Zinc was the most abundant microelement detected, followed by Pb, Fe, Mg, and Al. Morphological features observed include enamel rods in the rodent teeth, while incremental lines and semiprismatic enamel were observed in the alligator species. The fossil enamel was in an excellent state for microscopic analyses. Results show that all major dental enamel’s physical, chemical, and morphological features are present both in extant and extinct fossil tooth enamel (>8.5 Ma) in both taxa.

Immobilization mechanism of cesium in geopolymer: Effects of alkaline activators and calcination temperature

Geopolymer is always regarded as a promising material for the immobilization of radioactive waste. In the present study, the stabilization of Cs in geopolymers activated by NaOH and Na2SiO3 solutions and calcined at various temperatures was studied via toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope and energy dispersive spectroscopy (SEM-EDS), solid-state nuclear magnetic resonance (SSNMR), and N2 adsorption-desorption isotherm. For both NaOH-activated and Na2SiO3-activated geopolymers, the leaching concentrations of Cs decreased with the increase of calcination temperature. Specifically, most of the amorphous substance was crystallized to nepheline at 1000 °C for NaOH-activated geopolymer, and Cs+ can be incorporated into the structure of nepheline, contributing to the reduction of Cs leaching concentration. However, the amorphous structure was still maintained for Na2SiO3-activated geopolymer even after calcination at 1000 °C. It has been deduced that the main structure of Na2SiO3-activated geopolymer after calcination at 1000 °C should be in short-range order and Cs+ can be locked in a micro “crystal” structure. In addition, the change of specific surface area was not fully consistent with the decreasing trend of Cs leaching concentration. Therefore, the inner structure and the specific surface area of geopolymer should have a combined effect on the leaching behavior of Cs. This study can provide new insights into the application of geopolymer to immobilize radionuclides.