Composition Of Iron Research Articles

CALPHAD-Based Modeling and Experimental Validation of Silicon Effect on the Solidification Behavior of Novel SiNb Cast Irons

AbstractThe low oxidation resistance of SiMo ductile cast irons used as exhaust manifold material at high temperatures necessitates the development of new generation ductile cast iron compositions. New alloy designs can be made using CALPHAD methodology, and solidification sequence, segregation and critical phase transformation temperatures can be determined, especially for the solidified bulk materials. Thus, in commercial practicality, castable compositions with a raised A1 temperature can be obtained. In this study, novel SiNb cast irons with varying silicon contents were developed as candidate materials for exhaust manifolds. Solidification sequence, microsegregation, phase transformations, equilibrium phases of hypereutectic compositions containing 4 to 7 wt pct Si were calculated by CALPHAD-based modeling. The bulk materials of the studied compositions were cast as Y blocks and metallurgical analyzes were carried out. Studies revealed that; (i) in the ferritic matrix of the cast irons, graphite, Nb-rich carbides and some pearlite existed, (ii) pearlite formation was due to the negative segregation of silicon and positive segregation of manganese during solidification, (iii) as silicon content increased the amount of silicon dissolved in ferrite phase increased in the solidified structure and as a result pearlite formation decreased at the cell boundaries, and amount of vermicular graphite increased, (iv) depending on the silicon content the critical A1 temperature varied between 860 °C to 1013 °C and these values were higher than that of SiMo cast iron. All these findings revealed that SiNb cast irons had phase stability at higher temperatures compared to SiMo cast iron.

ОЦІНКА НАПРУЖЕНОГО СТАНУ РОБОЧОГО ШАРУ ВАЛКІВ КОЕРЦИТИМЕТРИЧНИМ ЕКСПРЕС-МЕТОДОМ

The purpose of the work is the problem of researching the influence of chemical composition and structure on the indicators of operational stability of centrifugal two-layer rolling rolls made of high chromium cast iron by the coercimetric express method. In order to ensure the achievement of this goal, the following tasks were set and solved: conducting an analysis of the causes of the destruction of the surface layer of rolls; building a mathematical model for studying the influence of the chemical composition and structure of cast iron on the level of hardness and coercive force; using the coercimetric method to analyze the quality of rolled rolls. Conclusions. Forecasting the behavior of the rolls during operation is inextricably linked to the analysis of the main factors on which the level of properties and operational stability of the working layer depend. The properties of high-chromium alloys are closely related to the type of phases formed and their ratio. The amount of residual austenite and martensite in the structure of the alloy has the greatest influence on the properties of the alloy (in the studied interval of changes in the proportion of phases). The operational layer of two-layer high-chromium rolls is characterized by a high level of residual stresses. Exceeding the permissible level of stresses or their unfavorable distribution can cause premature destruction during the operation of the roll. With the help of the coercimetric express method, it is possible to solve a fairly wide range of tasks of quality control of rolls, related to the determination of the level and distribution of residual stresses in the working layer of the rolls. This is because the intensity of the process of formation of thermal cracks under conditions of thermo-cyclic loading largely depends on the level of residual compressive stresses. Too high a level of stresses or their unfavorable distribution can cause premature destruction of the working layer of the roll, because the typical type of destruction due to an unbalanced distribution of stresses is cracking. A local increase in the level of coercive force can be the basis of the prediction of crack formation.

Fischer-tropsch synthesis: effect of temperature and iron-cobalt ratio in Fe-Co/meso-HZSM-5 catalyst on liquid product distribution

The Fischer-Tropsch synthesis converted hydrogen and carbon monoxide into linear hydrocarbons as liquid fuel. Iron and cobalt were used as polymerization catalyst, that impregnated on HZSM-5. The Fe-Co/HZSM-5 could be applied as bifunction catalyst which combined polymerizing synthesis gas and long chain hydrocarbon cracking for making biofuel. The objective of this study is observing the effect of temperature and composition of iron and cobalt combination, supported by HSZM-5 (Fe-Co/HZSM-5) catalyst on fuel product composition. The results obtained from this study would be used to find optimum condition for various iron and cobalt ratio in the catalyst. The mesoHZSM-5 was prepared from ammonium ZSM-5 over calcination, desilication, and dispersion. The mixed solution consisted of Co(NO3)2.6H2O and Fe(NO3)3.9H2O were used as precursor for incipient wetness impregnation on HZSM-5. The catalyst performance was observed in a continuous fixed bed reactor using Fe-Co/meso-HZSM-5 catalyst with synthesis gas at various composition iron and cobalt ratio (10–40 % wt. Fe in Co), various temperature (225–275 °C) at 20 bars. All catalysts were reduced in situ in the reactor. The 10Fe-90Co/mesoHZSM-5 catalyst was more suitable for FTS at 250 °C with alkane (20.49 %) as the main product and alcohol as the by-product (79.51 %). The others catalysts composition of 20–40 % Fe (by weight) in Fe-Co were more suitable for FTS at 225–250°C because under these conditions, alkanes as the main product were obtained in relatively higher compositions compared to other compounds. The mechanism of paraffins, olefins, aldehydes and alcohols formation in this FTS reaction followed the hydrogen assisted CO dissociation with CO-insertion mechanism

Effect of the Printing Angle on the Microstructure and Tensile Performance of Iron-Reinforced Polylactic Acid Composite Manufactured Using Fused Filament Fabrication

This work emphasizes an innovative approach utilizing 3D imaging technology based on synchrotron radiation to assess the microstructure of second-phase iron particles and the porous structure within 3D-printed PLA/magnetic iron composites at different printing angles. The study examines how these observations relate to the material’s ductility when processed using fused filament fabrication. In particular, this study examines the impact of one processing parameter, specifically the printing angle, on the microstructure and mechanical behaviour of a polylactic acid (PLA)–iron (PLI) composite designed for magnetic actuation. Fused filament fabrication is employed to produce PLI tensile specimens, with varied printing angles to create different layups. X-ray microtomography is utilized to analyse the microstructure, while tensile mechanical properties are evaluated for all composites, with findings discussed in relation to printing angle conditions. Scanning Electron Microscopy is used to examine the fractography of broken specimens. Results indicate that the printing angle significantly influences the tensile properties and mechanical anisotropy of 3D-printed PLI composites, with an optimal 45°/45° layup enhancing tensile performance. These findings suggest that 3D-printed PLI composites offer a cost-efficient means of producing bio-sourced, light-adaptive materials with intricate magnetic actuation capabilities. By quantifying the modulation of mechanical properties based on printing parameters that influence microstructural arrangement, the research sheds light on a novel aspect of composite material characterization.

Catalytic activation of persulfate by nanoscale zero-valent iron-derived supported boron-doped porous carbon for bisphenol A degradation.

In this study, boron-doped porous carbon materials (BCs) with high surface areas were synthesized employing coffee grounds as carbon source and sodium bicarbonate and boric acid as precursors; afterward, nanoscale zero-valent iron (nZVI) and BCs composites (denoted as nZVI@BCs) were further prepared through reduction of FeSO4 by NaBH4 along with stirring. The performance of the nZVI@BCs for activating persulfate (PS) was evaluated for the degradation of bisphenol A (BPA). In comparison with nZVI@Cs/PS, nZVI@BCs/PS could greatly promote the degradation and mineralization of BPA via both radical and non-radical pathways. On the one hand, electron spin resonance and radical quenching studies represented that •OH, SO4•-, and O2•- were mainly produced in the nZVI@BCs/PS system for BPA degradation. On the other hand, the open circuit voltages of nZVI@BCs and nZVI@Cs in different systems indicated that non-radical pathway still existed in our system. PS could grab the unstable unpaired electron on nZVI@BCs to form a carbon material surface-confined complex ([nZVI@BCs]*) with a high redox potential, then accelerate BPA removal efficiency via direct electron transfer. Furthermore, the performances and mechanisms for BPA degradation were examined by PS activation with nZVI@BC composites at various conditions including dosages of nZVI@BCs, BPA and PS, initially pH value, temperature, common anions, and humid acid. Therefore, this study provides a novel insight for development of high-performance carbon catalysts toward environmental remediation.

The role of intrinsic soil properties in the compressive strength and volume change behavior of unstabilized earth mortars

Despite the growing interest in earthen construction, there is critical lack of reliable experimental data on the soil properties which mostly affect the engineering characteristics of the dried building material. Therefore, the main objective of this research was to explore the influence of some of these properties, namely clay fraction content, Specific Surface Area (SSA), Cation Exchange Capacity (CEC), chemical and mineralogical composition and various forms of iron and calcium carbonate on earth mortars. The initial trigger for this research was the extraordinary compressive strength of four earth mortars prepared with different soils. So, these four soils, along with seven others from previous research, were thoroughly examined using soil science techniques to investigate the link between soil properties and compressive strength and linear shrinkage of earth mortars. A relationship between the compressive strength to CEC ratio and dry density was found, highlighting the decisive role of clay activity as expressed by CEC, in earthen materials properties. According to linear regression and dominance analysis, the strongest correlation was exhibited by SSA followed by CEC, demonstrating that compressive strength is largely dependent on these two properties. Less strong correlation was found for clay fraction content, while poorly ordered/amorphous iron oxides were found to correlate with strength and shrinkage, but their contribution requires further research. Regarding the mineralogical properties, it was found that the mortars that achieved the highest strengths contained poorly crystalline smectite clays. Finally, even significant differences in soil chemical composition did not necessarily lead to different mortar properties.

Facilitating Se(VI) adsorption and electron transfer by introducing αFeOOH to sulfidated zero-valent iron

Sulfidation of zerovalent iron (SZVI) enhances electron transfer ability due to the formation of FeSx, which facilitates pollutant removal. However, for pollutants that are difficult to adsorb onto SZVI, the longer electron transfer distance results in inefficient removal. The presence of iron (hydr)oxides on ZVI and SZVI is inevitable, and it can adsorb highly mobile pollutants (such as Se(VI)). Here, we regulated the composition of iron (hydr)oxides on ZVI and SZVI surfaces by aging treatment, which improves their Se(VI) removal performance. Based on this, αFeOOH which has a strong affinity for Se(VI), is introduced onto SZVI to synthesize the high-quality composite SZVI-αFeOOH. The characterization results showed that Fe-OH from αFeOOH and FeSx successfully combined and uniformly distributed on SZVI-αFeOOH, creating active sites, and the Se(VI) removal rate (kobs = 0.2211 min−1) increased ∼ 7.4 times over SZVI (kobs = 0.0297 min−1). The adsorption and reduction of Se(VI) were optimized by regulating the mass ratio of αFeOOH to SZVI. In addition, different initial Se(VI) concentrations and solution pH were designed to explore the effects on Se(VI) removal and evaluate the best removal reaction condition. The mechanism of Se(VI) removal by SZVI-αFeOOH is as follows: Se(VI) is firstly adsorbed on αFeOOH, which shortens the electron transfer distance, and then the absorbed Se(VI) is reduced to readily immobilized states by SZVI. This work proposes a targeted strategy to modify SZVI to efficiently remove pollutants with strong mobile and difficult adsorption.

Determination of 17 phthalate esters in water using GC–MS combined with magnetic solid phase extraction with Fe3O4@GO

In this study, a new technique was developed which combines magnetic solid phase extraction (MSPE) and gas chromatography-mass spectrometer (GC–MS), for the analysis of 17 phthalate esters (PAEs). First, a composite of iron (used as the magnetic part) and graphene oxide (GO) was synthesized for application in MSPE. Scanning electron microscop, X-ray diffraction and infrared spectroscopy were used to characterize this material. Finally, magnetic graphene oxide (Fe₃O₄@GO) was used to extract PAEs from water samples. Various parameters relevant to the extraction were optimized, such as the amount of adsorbent employed, adsorption time, luent solvent types and volume, and sample pH. These optimum conditions resulted in calibration curves for the 17 PAEs, showing linear relationships between concentration and response at concentrations of 25 to 2500 µg L⁻¹ with correlation coefficients from 0.9983 to 1.000. Limit of detection and limit of quantitationfor the PAEs ranged from 0.030 to 0.12 µg L⁻¹ and 0.10–0.40 µg L⁻¹, respectively. The recovery rates for these compounds in spiked samples were ranging from 81.5% to 109% with relative standard deviation less than 6.12%. The effectiveness of method was further demonstrated by its use in detecting 17 PAEs in samples of drinking and bottled water. Compounds such as DEP, DIBP, DBP, and DCHP were identified. These results thus highlight the suitability of Fe₃O₄@GO as an adsorbent for concentrating and purifying PAEs in water samples.

Magnetic triiron tetraoxide/biochar–loaded nanoscale zero-valent iron for chromium(VI) removal from aqueous solution

BackgroundTo inhibit the agglomeration of nanoscale zero-valent iron (nZVI or Fe0), increase its stability and facilitate electron transfer, magnetic triiron tetraoxide/biochar (MBC) was used as the carrier to load nZVI. Consequently, a new pathway was created for electron transfer from nZVI to triiron tetraoxide (Fe3O4) and then to contaminants, thereby improving the chemical reactivity of nZVI. MethodsMagnetic triiron tetraoxide/biochar–loaded nanoscale zero-valent iron (nZVI@MBC) composites were prepared for chromium(VI) adsorption. Different influencing aspects were studied, including the loading percentage of nZVI, solution pH, co-existing anions(PO43−, SO42−, Cl−, NO3−), temperature and reusability. Furthermore, the adsorption isotherms, kinetics and thermodynamics for Cr(VI) removal were performed. Significant findingsnZVI@MBC exhibited an adsorption amount of 117.25 mg g−1 at the optimal conditions (dosage 0.4 g L−1, initial concentration 50 mg L−1, temperature 30 °C, nZVI loading percentage onto MBC 5.0 wt% and pH 2). The adsorption data obeyed the pseudo-second-order kinetics model and followed the Langmuir isotherm, thermodynamic characteristics revealed that Cr(VI) adsorption onto nZVI@MBC was a spontaneous endothermic process. After four recycles, the Cr(VI) removal efficiency remained higher than 70 %, exhibiting a good reusable ability. The mechanisms were confirmed to be physical adsorption, chemical reduction and co-precipitation processes.

Experimental Study of a Representative Sample to Determine the Chemical Composition of Cast Iron.

In metallurgical practice, the material is considered of adequate quality if it meets the customer's expectations. It is necessary to take representative samples and perform quality testing to avoid financial and intangible losses. Sample contamination and matrix and surface quality play a significant role in the accuracy of chemical analyses. The purpose of this paper is to point out the advantages of specific methods of taking samples, such as immersion and spoon sampling of molten metal, and, in the experimental part, to assess the impacts of factors affecting the quality of the sampling. The influence of time of final sampling on determining the true amount of magnesium during a single melt and the influence of duration of mixing of molten cast iron on the accuracy of chemical analysis of the control sample were investigated. It is important that the time between the modification and casting of the liquid cast iron from the casting ladle be as short as possible. This is because the magnesium burns out and thus the chemical analysis of the sample taken is not accurate. Another important factor is ensuring the melt before sampling is homogenized and has the minimum prescribed temperature (1420 °C). Increasing sample collection time will cause changes in its chemical composition.

Synthesis and environmental applications of biochar-supported nano-zero-valent iron composites: a review

Synthesis and environmental applications of biochar-supported nano-zero-valent iron composites: a review

Effects of NbC addition on mechanical and tribological properties of AlCrFeNi medium-entropy alloy

AlCrFeNi medium-entropy alloy (MEA) without expensive Co has demonstrated superior properties over the well-known AlCoCrFeNi high-entropy alloy. We added NbC particles to the MEA to make NbC-reinforced MEA alloys or MEA-matrix composites, and evaluated their wear resistances and mechanical properties. The materials showed considerably improved performance. To well judge the NbC-MEA for realistic applications, the wear resistance of the NbC-MEA samples was compared with those of a few industrial wear-resistant materials, e.g., high-Cr cast iron (HCCI) and WC-Co composites. It was demonstrated that the MEA samples with 40–60 vol% NbC exhibited markedly higher wear resistance than the reference materials, and the MEA demonstrated high superiority over the widely used Co as the metal-matrix for developing wear-resistant metal-matrix composites (MMCs).

Comparative Reports on Pleurotus Sajor-caju Cultivated on Local Wood Wastes in Ibadan Metropolis, Nigeria

Cultivation of Pleurotus species, an Oyster mushroom is now becoming well known due to its taste, medicinal and nutritional values. It is capable of degrading agricultural wastes efficiently and even grows at different temperature ranges. Relatively, Pleurotus species has shorter life span and the fruiting bodies are rarely attacked by pests and diseases unlike the other edible mushrooms. Therefore, the aim of this research is to access the influence of mineral constituents of five local wood wastes (Anogeissus leiocarpa, Pouteria altissima, Vitellaria paradoxa, Cordia milleni and Triplochiton scleroxylon) in Ibadan metropolis on the growth, fruiting body yield and proximate analysis of cultivated oyster mushroom (P. sajor-caju). Data of Carbon/Nitrogen ratio (11.10 – 11.60) found reveal composition of Magnesium (0.035 mg), Potassium (0.053 mEq/l), Manganese (0.0013 mg), Copper (0.00050 g/m3), Iron (0.00275 mol/L), Phosphorus (0.027 mmol/L), Organic carbon (32.10 mg/L C), Organic matter (55.3 t/ha) and total nitrogen (2.77 mg/L) contributed greatly to the high crude protein, fats and ash contents of mushroom   cultivated  on T. Scleroxylon. However, insignificant contents of sodium (0.2 mg), Calcium (0.2 mmol/L) and Magnesium (0.013 mg) in Pouteria altissima led to the general inadequate performance of (P. sajor-caju) in yields. The fresh mean weight of (P. sajor-caju) was from 8.00 g – 27.53 g. The heaviest weight was obtained from T. scleroxylon followed by V. paradoxa, C. milleni, while Anogeissus leiocarpa gave the lightest weight. Hence, T. scleroxylon will be suggested for cultivating P. sajor-caju because of its positive impact on the yield, crude fibre, and protein content of the experimented mushroom.

Proximate, Minerals and Vitamins Analyses of Some Common Foods in Nigeria

Nutritional composition is a key factor that must be considered in our daily choice of diets. Hence, the need for nutritional analysis of these five (5) common Nigerian solid foods (poundo yam, semovita, corn flour, cassava flour, and wheat flour). The flour samples were chemically analysed for proximate and Mineral elements: magnesium, iron, sodium and calcium composition, using the methods described by Association of Analytical chemist. Vitamin A content was determined by spectrophotometric method while Vitamin C content was determined using the spectrometric method coupled with DNPH procedures. The result revealed that Poundo yam had the highest carbohydrate content (82.695%) and least in the following parameters; moisture (7.55%), calcium (30.075mg), iron (9.20mg), sodium (15.565mg), and magnesium (26.185mg) among other samples. Semovita has the highest protein content (16.3%), vitamin A (0.52mg) and vitamin C (3.61mg). Wheat flour was rated highest in ash (1.82%) and sodium (25.3mg) contents respectively. It was also observed that wheat flour had the least content of vitamin A (0.09mg). Corn flour was highest in crude fat (5.5%). Cassava flour had the highest crude fibre (1.9%), calcium (228.55mg), iron (17.85mg) and magnesium (88.55mg), and turned out to be least in protein (1.025%) and vitamin C (0.44mg) content.

Determination of macro and micronutrients in diferentes species of ora-pro-nóbis and comparison with conventional vegetable

The aim of this work was to determine the proximate composition and contents of iron, copper, manganese, phenolic compounds, phytic acid, total titratable acidity and pH of three species of ora-pro-nóbis (OPN): Pereskia aculeata Miller (PA), Pereskia aculeata var. godseffiana (PAG) and Pereskia grandifolia Haworth (PG) from domestic cultivation. Furthermore, compare the results obtained with a conventional vegetable kale (CM) (Brassica oleracea L. acephala) and evaluate the interrelationships through Principal Component Analysis (PCA). The ora-pro-nóbis species were statistically different from the CM in terms of total titratable acidity, pH, phenolic compounds, iron and copper at a significance level of 5%. The CM and PA showed statistical similarities in relation to protein, carbohydrate and manganese content at a significance level of 5%, while for PA and PG samples statistical similarities were observed for moisture and phytic acid at a significance level of 5%. For OPN species, the minerals concentrations varied from 15.26 ± 6.40 to 25.52 ± 4.72 mg Fe 100 g-1, 1.23 ± 0.81 to 5.31 ± 6.57 mg Cu 100 g-1, 12.00 ± 6.31 to 17.72 ± 13.13 mg Mn 100 g-1. ACP demonstrated that the PAG sample made the greatest contribution to the study, having in its composition the highest levels of iron, copper, phytic acid and moisture. Therefore, the species of ora-pro-nóbis evaluated in this work, even in residential cultivation conditions, proved to be potential sources of minerals, mainly iron, especially the species Pereskia aculeata var. godseffiana. In this way, the evaluation of the proximate and mineral composition of unconventional food plants is relevant for understanding the nutritional composition and increasing the consumption of these vegetables, in their use for food enrichment, as well as in helping to reduce the population's food insecurity.

Mechanism Analysis for the Enhancement of Low-Temperature Impact Toughness of Nodular Cast Iron by Heat Treatment.

The low-temperature impact toughness of nodular cast iron can be significantly enhanced by heat treatment, and thus meet the severe service requirements in the fields of high-speed rail and power generation, etc. In order to explore the enhancement mechanism, microstructure, hardness, composition and other characteristics of as-cast and heat-treated nodular cast iron is systematically tested and compared by optical microscopy, microhardness tester, EBSD, SEM, electron probe, and impact toughness testing machine in this study. The results show that heat treatment has little effect on the morphology and size of graphite in nodular cast iron, ignores the effect on the grain size, morphology, and distribution of ferritic matrix, and has little effect on the hardness and exchange of elements, while it is meaningful to find that heat treatment brings about significant decrease in high-angle grain boundaries (HAGB) between 59° and 60°, decreasing from 10% to 3%. Therefore, the significant enhancement of low-temperature impact toughness of nodular cast iron by heat treatment may result from the obvious decrease in HAGB between 59° and 60°, instead of other reasons. From this perspective, the study can provide novel ideas for optimizing the heat treatment process of nodular cast iron.

Synergistic redox and adsorption for enhanced Roxarsone removal: Heterogeneous Fenton-Like reaction with a novel composite of nanoscale zero-valent iron supported on γ-aluminum oxide

Roxarsone (ROX), a livestock growth enhancer, poses environmental and health hazards due to its remarkable stability, making traditional degradation methods ineffective. To tackle this issue, a novel Fenton-like composite, composed of nanoscale zero-valent iron supported on γ-aluminum oxide (nZVI/γ-Al2O3), was synthesized to boost ROX degradation. Results demonstrated nearly complete mineralization of the ROX organic matrix within just 180 min, facilitated by the Lewis acidity sites of γ-Al2O3. Significantly, this composite exhibited selective adsorption of released AsO43− ions on its surface, forming FeAsO4 and Fe-As-Al complexes. It also established an internal redox cycle involving Fe(0), Fe(II), and Fe(III), ensuring a continuous and efficient generation of primary reactive oxygen species (·OH and O2·−). Thus, a simultaneous redox process occurred on the composite surface can be attributed to the synergy of the reducibility of nZVI and the oxidation catalyzed by ·OH and O2·−. Initially, the nitro group of ROX was reduced by nZVI, forming more hydrophilic o-aminophenol, favoring subsequent oxidation and mineralization. Simultaneously, the As-C bonds in ROX were oxidized, yielding AsO43−, which was subsequently adsorbed over extended reaction times. This innovative approach offers a potential solution for treating wastewater contaminated with metalloid-organic composite pollutants, addressing the environmental and health concerns associated with ROX residues.

Iron and Molybdenum Isotope Application for Tracing Industrial Contamination in a Highly Polluted River

Rivers adjacent to industrial zones usually suffer from severe pollution issues. Industrial wastewater that has undergone sewage treatment processes may be legally discharged into rivers under water quality permits. Previous studies have frequently employed isotopic tracers to identify potential contaminants for pollution control. Conventional radiogenic isotopes utilized in tracing studies cannot discern whether the source is untreated (primary) industrial wastewater, which can have serious impact to the environment. By analyzing the iron (Fe) and molybdenum (Mo) isotopic compositions in original industrial wastewater and treated effluent, this study aims to investigate whether the heavily polluted Agongdian River is contaminated by the untreated wastewater. Based on the results from this study, the original industrial wastewater exhibits higher concentrations of metallic elements and heavier Fe and lighter Mo isotopic compositions, compared to the treated effluent. Consequently, it appears that Agongdian River water indeed exhibits evidence of untreated industrial wastewater. Furthermore, the volume of original industrial wastewater entering the river can be estimated from these results. This research offers a more precise and accurate approach to monitor potential industrial wastewater pollution in natural water bodies, contributing to the goal of environmental protection and sustainable development.

Fractionation of iron and titanium isotopes by ilmenite and the isotopic compositions of lunar magma ocean cumulates

Basaltic volcanism on the Moon produced low- and high-Ti mare basalt suites that are also distinct with respect to their iron, titanium, and magnesium isotopic compositions. Here, the equilibrium fractionation of Fe and Ti isotopes between ilmenite and melt was experimentally investigated in order to evaluate the role of ilmenite in generating the isotopic compositional variability among the lunar mare basalts. Ilmenite crystallization experiments were conducted using two bulk compositions: an ilmenite-saturated basaltic andesite and an ilmenite-saturated Apollo 14 black glass, and the Fe and Ti isotopic compositions of the experimental ilmenites and glass (quenched melt) were analyzed using solution MC-ICPMS after hand-picking. Additionally, Nuclear Resonant Inelastic X-ray Scattering (NRIXS) measurements on synthetic ilmenite were conducted and compared to previous NRIXS measurements on synthetic lunar glasses in order to derive temperature-dependent equilibrium ilmenite-melt Fe isotopic fractionations. Experimentally determined ilmenite-melt fractionations were then incorporated into a lunar magma ocean crystallization model that tracks the major element and isotopic compositional evolution of lunar magma ocean cumulates and residual liquid. There is good agreement between the Fe equilibrium isotopic fractionation measured by NRIXS and the laboratory equilibration experiments, and we find that the isotopic fractionation is sensitive to ilmenite compositional differences (0 vs. 10% Fe3+). Further, the light Ti isotopic composition of ilmenite relative to the melt (Δ49Ti=ilmenite-melt−0.09±0.03‰ at 1100∘C) is consistent with the higher coordination of Ti in ilmenite relative to melts and results of previous studies. The modeled Ti isotopic compositions for lunar magma ocean cumulates display Ti isotopic variability sufficient to explain the low- and high-Ti mare basalt sources. However, the difference in Fe isotopic composition between the low- and high-Ti mare basalts cannot be attributed solely to ilmenite fractionation. Instead, Fe isotopic fractionation by additional products of lunar magma ocean crystallization, such as clinopyroxene, is required to generate the inferred Fe and Mg isotopic variability in the lunar mantle. Alternatively, the Fe and Mg isotopic compositions of the lunar mare basalts may indicate Fe-Mg interdiffusion has occurred in the Ti-rich component of the mare basalt source regions via reaction between ilmenite cumulates and the olivine- and pyroxene-rich lunar mantle.

Efficient removal of tetracycline in water using modified eggplant straw biochar supported green nanoscale zerovalent iron: synthesis, removal performance, and mechanism.

A novel NaOH modified eggplant straw biochar supported green nanoscale zerovalent iron (P-nZVI/ESBC) composite was synthesized and its removal performance and reaction mechanism for tetracycline (TC) in water were investigated. Multiple characterizations showed that the prepared P-nZVI/ESBC composite contained oxygen-containing functional groups (hydroxyl, carbonyl, and carboxyl groups) and Fe species (nZVI and its oxides). The dosage of composite, temperature, and solution pH significantly affected the removal capacity of the P-nZVI/ESBC composite for TC. The Avrami fraction-order kinetic model and Sips adsorption isotherm model can fit well the removal process of TC by the P-nZVI/ESBC composite, indicating that the adsorption behavior of TC involved multiple adsorption mechanisms and chemical adsorption might occur. The maximum adsorption capacity of the P-nZVI/ESBC composite for TC was 304.62 mg g-1. The adsorption and reductive degradation were the dominant mechanisms of TC removal by the P-nZVI/ESBC composite. This work offers abundant information on the application of eggplant straw to manufacture biochar-based composites for the efficient removal of antibiotic contaminants from aquatic environments.