Hematite Content Research Articles

Separation of iron and carbon concentrates from thermal power plant solid waste using physical methods

This research study examined the physical enrichment processes of coal fly ash (CFA) from the 2nd thermal power plant in Almaty. Magnetic separator and flotation enrichment methods were used to separate the magnetite and carbon parts of coal fly ash, respectively. In the study, a laboratory magnetic separator separated hematite content from 4.49 to 5.57% by mass from ash residues of different fractions. Cheap and available kerosene and flotol-b were used as flotation reagents for flotation enrichment. The particle size of coal ash is 63-100 μm, and the amount of carbon concentrate is ~16.3% by weight. The remaining mineral of coal ash is an essential raw material for building materials.

Nonnegligible contribution of terrigenous sediment inputs from local small watersheds to west regions of the Pearl River Estuary, northern South China Sea shelf

As a crucial “sink” for terrigenous material entering the ocean, provenance of sediments within the coastal zone and continental shelf sea regions holds significant scientific importance in the investigation of global material cycling. Environmental magnetism was proved as an effective and rapid approach for sediment source identification. Detail and systematic magnetic measurements were performed for surface sediment samples collected from the mega Pearl River, local small rivers (Tan, Moyang and Jian rivers) of west Guangdong, coastal zone (CZ) and continental shelf (CS) to analyze the contribution of local small watersheds to marine sediments. The results indicate that detrital river input magnetite and hematite are coexisted in both CZ and CS sediments. Compared to CZ sediments, relatively higher concentration of hematite and finer grain size of magnetite are appeared at CS sediments. By comparing of magnetic parameters, it was inferred that magnetic minerals from the Pearl and Tan rivers are transported and deposited on the coastal zone by Guangdong longshore current. Meanwhile, sediment magnetic parameters in the Moyang and Jian Rivers are similar to the CS sediments, implying the two rivers-sourced materials were directly transported and deposited at the CS due to their narrow and restricted estuaries, and/or the CS preserves the residual deposits from the two rivers formed during the Last Glacial. Except for the Pearl River, sources of local small rivers significantly contribute to marine sediments at the coastal zone and continental shelf.

Thermal Studies of Fractionated Lignite and Brown Coal Fly Ashes.

Coal fly ash (CFA), a by-product of coal combustion, is a valuable raw material for various applications. However, the heterogeneous nature of the composition and properties of CFA provides challenges to its effective usage and utilisation. This study investigates the thermal behaviour of the fly ashes of lignite (FA1) and brown coal (FA2) and their fractions obtained by dry aerodynamic separation. Thermal analysis techniques, including thermogravimetry (TG), differential scanning calorimetry (DSC), and evolved gas analysis (EGA), were used to characterise the behaviour of the fly ash fractions while heating up to 1250 °C. The results reveal distinct differences in the thermal behaviour between ash types and among their different size fractions. For the FA1 ashes, the concentration of calcium-rich compounds and the level of recrystallisation at 950 °C increased with the decrease in particle size. The most abundant detected newly formed minerals were anhydrite, gehlenite, and anorthite, while coarser fractions were rich in quartz and mullite. For the FA2 ashes, the temperature of the onset of melting and agglomeration decreased with decreasing particle size and was already observed at 995 °C. Coarser fractions mostly remain unchanged, with a slight increase in quartz, mullite, and hematite content. Recrystallisation takes place in less extension compared to the FA1 ashes. The findings demonstrate that the aerodynamic separation of fly ashes into different size fractions can produce materials with varied thermal properties and reactivity, which can be used for specific applications. This study highlights the importance of thermal analysis in characterising fly ash properties and understanding their potential for utilisation in various applications involving thermal treatment or exposure to high-temperature conditions. Further research on advanced separation techniques and the in-depth characterisation of fly ash fractions is necessary to obtain materials with desired thermal properties and identify their most beneficial applications.

Progressive development of stylolites in cryptocrystalline quartz

Stylolites are common dissolution structures in carbonate rocks in the upper crust and document a coupled physical-chemical feedback during pressure solution in rocks. By applying high-resolution electron-based analysis we investigate a rare example of stylolites in cryptocrystalline quartz (novaculite) from western Sichuan Basin, China. The investigated stylolites exhibit an increased amplitude from the tip toward the center, which correlates with the maturity of stylolites and thus provides an excellent opportunity to infer the dynamic processes operating during stylolite formation. Microstructurally, stylolites are characterized by a concentration of biotite and hematite, dissolving irregular quartz grains, and the occurrence of dissolution porosity. By investigating the progressive co-variations between stylolite amplitude and microstructure characteristics from the stylolite tip toward the center, we demonstrate, for the first time, the evidence of stylolite growth through anticracks. It is inferred that stylolites in cryptocrystalline quartz originate from the propagation of mode I micro-cracks around pre-existing biotite, followed by pore-scale dissolution. Both processes, micro-cracking and dissolution, are interacting and co-evolving via a self-organization fashion during shortening. Our study contributes to the ongoing debate about whether stylolites are conduits or barriers for fluid flow.

Ballistic resistance and microwave absorbing properties of a composite made of aramid fabric impregnated with polyethylene glycol and hematite nanoparticles

The ballistic resistance and microwave absorption of a composite of aramid fabric impregnated with polyethylene glycol and hematite nanoparticles was investigated for different hematite concentrations between 0 and 17 wt%. Different damage and energy absorbing mechanisms during ballistic impact were identified: cone formation on the back face of the target, tensile failure of primary yarns and deformation of secondary yarns. In terms of energy absorption, the best results were achieved with 7 wt% hematite, while the smallest depth of penetration (DOP) was observed for a composite with 9 wt% hematite. A scanning electron microscope (SEM) image of the composite with 7% hematite after the ballistic test showed that the main energy absorption mechanism was deformation of secondary yarns. The microwave absorption was measured using the waveguide technique in the frequency range from 8 to 12 GHz. The results showed that the dielectric loss ɛ”/ɛ’ is maximum for a concentration of 3% hematite, while the magnetic loss µ”/µ’ is maximum for a concentration of 11 wt% hematite. A reasonable compromise between ballistic resistance and microwave absorption seems to be a composite with 7 wt% hematite.

Hematite-Gamma Alumina-based Solid Catalyst Development for Biodiesel Production from Palm Oil

This research investigated the performance of hematite-gamma alumina (Fe2O3/γ-Al2O3) catalyst in biodiesel production from palm oil. A full factorial experimental design was utilized to analyze the effect of hematite content, catalyst loading, and methanol-to-oil ratio on catalyst performance. From the experiment, biodiesel in the range of 73.6 to 87.6% FAME content was obtained. It was concluded that the catalyst composition, the methanol-to-oil ratio, and the catalyst loading have a significant effect on the FAME content of the biodiesel. Hematite has strong affinity for fatty acids, so a larger hematite surface area will result in a higher fatty acid absorption capacity. The addition of excess methanol can reduce the contact inhibition between the reactants and the active site of the catalyst, thereby increasing the conversion rate of the reaction. Moreover, a higher amount of catalyst loading can result in an increase in the FAME content when accompanied by an increase in the hematite content of the catalyst.

A New Perspective on the Applicability of Diffuse Reflectance Spectroscopy for Determining the Hematite Content of Fe-Rich Soils in the Tropical Margins of China

Hematite and goethite are widely occurring chromogenic iron oxides in soils and sediments that are sensitive to climatic dry/wet shifts. However, only by accurately quantifying the content or ratio of hematite and goethite can they be applied reliably to palaeoclimate reconstruction. Compared to the Loess Plateau of China, hematite in the soils of southern China has not been sufficiently studied. We used diffuse reflectance spectroscopy (abbreviation DRS, including the first-derivative curves and the second-derivative curves of the Kubelka–Munk remission functions), combined with ignition at 950 °C, and X-ray fluorescence (XRF) to quantify the hematite content of four tropical-margin iron-rich soil profiles with different matrix compositions in the Leizhou Peninsula, China. We also examined the application of hematite quantification parameters in soils with different matrix compositions under the same climatic conditions. Our main findings are as follows: (i) DRS first-derivative curves can reflect the presence of goethite and hematite in soils, and their relative contents can be compared within the same profile. (ii) The second-derivative curve of the Kubelka–Munk remission functions can reflect the relative proportions of goethite and hematite and provide information about the degree of Al substitution. (iii) Combined with calibration equations, soil redness can reliably quantify the hematite content, but it is necessary to consider the effect of mucilage envelopes in the process of hematite formation. Additionally, we summarize various methods used for quantifying hematite, and the influence of soil matrix compositions, with the aim of providing a reference for hematite quantification elsewhere. We also propose a new indicator (ΔHmRed/HmRed) to help detect iron hydroxide/iron oxide changes in soils.

High-resolution climate change during the Marine Isotope Stage 3 revealed by Zhouqu loess in the eastern margin of the Tibetan Plateau

A consensus has not yet been reached on effects of climate change and driving mechanisms between the Tibetan Plateau (TP) and adjacent monsoonal areas during the Marine Isotope Stage 3 (MIS 3). Loess–paleosol sequences from the TP provide valuable information about the MIS 3 environmental history. Detailed color index and a diffuse reflectance spectral (DRS) analysis of Zhouqu (ZQ) loess from the Western Qinling Mountains were conducted to investigate climate change on the eastern margin of the TP during the MIS 3. Our results show that the variations in color index and iron oxide content in ZQ loess are mainly caused by the pedogenesis and climate conditions. The lightness (L*) value and hematite (Hm) content were used to reconstruct the precipitation history and temperature changes, respectively. The reconstructed records revealed that climate change during the MIS 3 was characterized by high frequency and large amplitude, with millennial-scale changes superimposed on orbital-scale changes. Warm–humid climate occurred in the late MIS 3, while the early climate of MIS 3 was relatively cold–dry. The Indian summer monsoon (ISM) and temperature variations during the MIS 3 mainly occurred due to obliquity and precession. The North Atlantic cooling led to the southward movement of the Intertropical Convergence Zone, and the downstream cooling of the atmosphere by the westerly jet could result in events on a millennial-scale in the eastern margin of the TP. The interhemispheric forcing may play an important role in driving the strong summer monsoon in the late MIS 3.

The implementation of dust mineralogy in COSMO5.05-MUSCAT

Abstract. Mineral dust aerosols are composed of a complex assemblage of various minerals depending on the region in which they originated. Given the different mineral composition of desert dust aerosols, different physicochemical properties and therefore varying climate effects are expected. Despite the known regional variations in mineral composition, chemical transport models typically assume that mineral dust aerosols have uniform composition. This study adds, for the first time, mineralogical information to the mineral dust emission scheme used in the chemical transport model COSMO–MUSCAT. We provide a detailed description of the implementation of the mineralogical database, GMINER (Nickovic et al., 2012), together with a specific set of physical parameterizations in the model's mineral dust emission module, which led to a general improvement of the model performance when comparing the simulated mineral dust aerosols with measurements over the Sahara region for January–February 2022. The simulated mineral dust aerosol vertical distribution is tested by a comparison with aerosol lidar measurements from the lidar system PollyXT, located at Cape Verde. For a lofted mineral dust aerosol layer on 2 February at 05:00 UTC the lidar retrievals yield a dust mass concentration peak of 156 µg m−3, while the model calculates the mineral dust peak at 136 µg m−3. The results highlight the possibility of using the model with resolved mineral dust composition for interpretation of the lidar measurements since a higher absorption in the UV–Vis wavelengths is correlated with particles having a higher hematite content. Additionally, the comparison with in situ mineralogical measurements of dust aerosol particles shows that more of them are needed for model evaluation.

Polymer Composites of Low-Density Polyethylene (LDPE) with Elongated Hematite (α-Fe2O3) Particles of Different Shapes

Due to the intensive search for new types of advanced polymer materials for targeted applications, this work offers insight into the properties of low-density polyethylene/hematite composites. The specific feature of this study lies in the use of elongated hematite particles of different shapes. Uniform ellipsoid-, peanut- and rod-shaped hematite particles were hydrothermally synthesized and incorporated into the polymer matrix of low-density polyethylene (LDPE). LDPE/hematite composites are prepared by melt mixing. Hematite particles are characterized by scanning electron microscopy (SEM) and powder X-ray diffraction (PXRD). The pure LDPE polymer and LDPE/hematite composites were studied by FT-IR and UV-Vis-NIR spectroscopy and by thermogravimetric analysis (TGA). The determination of the mechanical and barrier properties was also carried out. The obtained results indicate the influence of the elongated particles on the improvement of LDPE properties. An increase in thermal stability and UV-absorption was observed as well as the improvement of mechanical and barrier properties. The improvement of the composites’ properties in comparison to the pure LDPE is especially visible in the composites prepared with low content of hematite (0.25%). LDPE/hematite composites have promising characteristics for application as packaging materials with enhanced mechanical, thermal and barrier properties as well as UV-protective materials.

Novel Bi-Functional MoS2/α-Fe2O3 Nanocomposites for High Photocatalytic Performance

In this study, 3-dimensional molybdenum disulfide (MoS2) structures, integrated with hematite (α-Fe2O3) nanoparticles, were fabricated under a convenient two-step hydrothermal route. The fabricated photocatalytic nanocomposites consist of well-arranged MoS2 flakes, resembling spherical flower-like morphology, and the nanoparticulate α-Fe2O3 structures decorate the 3D network. By raising the α-Fe2O3 weight ratio, the composites’ specific surface area and morphology were not affected, regardless of the partial cover of the cavities for higher hematite content. Moreover, the crystallinity examination with XRD, Raman, and FTIR techniques revealed that the precursor reagents were fully transformed to well-crystalized MoS2 and Fe2O3 composites of high purity, as no organic or inorganic residues could be detected. The photocatalytic oxidation and reduction performance of these composites was evaluated against the tetracycline pharmaceutical and the industrial pollutant hexavalent chromium, respectively. The improvement in the removal efficiencies demonstrates that the superior photoactivity originates from the high crystallinity and homogeneity of the composite, in combination with the enhanced charge carriers’ separation in the semiconductors’ interface.

Geochemical Characterization of Sedimentary Materials (Limestone, Gypsum, Coal, and Iron Ore) along the Nile River Basin, South Wollo, Ethiopia

Sedimentary rocks are produced by the weathering of preexisting rocks and the subsequent transportation and deposition of the weathering products. Among the sedimentary rocks, especially limestone is a crucial raw material for cement production. The purpose of this study was to characterize the valuable industrial raw materials, limestone, gypsum, clay, coal, and iron ore, along with the Nile River basin. For sample collection, a random sampling method was applied. Different analytical methods were carried out for complete oxide analysis such as LiBO2 fusion, HF attack, and gravimetric, calorimetric, and atomic absorption spectroscopy (AAS). The percentages of oxides detected in this study are in the range of acceptable values (high content of CaO ranging from 47.3 to 50.4% and less content of SiO2 ranging from 8.72 to 11.24%) for good proposal as a potential raw material for cement production. The most dominant and wide-range coverage of limestone along with the Nile basin, particularly near Arsema Monastery, was found as matured limestone. The petrographic analysis of gypsum, sandstone, and clay samples indicated that all the samples taken from Wegidi revealed that the high percentage of gypsum ranges from 90 to 95%. Sandstone is dominantly preset in Kelala to Jamma road along with Beto River with high content of SiO2 ranging from 61 to 95%. The results of this study indicate that the treated coal samples are relative to high calorific value, fixed carbon, and low ash content. Coal and iron ore from Jamma revealed that high calorific value is 4929.24 and hematite content is 52.2, respectively. The result of this study revealed that a huge amount of limestone reservoir is detected in Borena Wereda, Amhara, Ethiopia.

Characterization and properties of Chinese red clay for use as ceramic and construction materials.

This study involves the characterization and analysis of a Chinese red clay obtained from Hunan province to determine its suitability for manufacturing ceramic products. X-ray fluorescence analysis showed the clay has high silica (63.25 weight percent) and alumina (21.38 weight percent) content along with iron oxide, alkalis, and calcium acting as fluxes. X-ray diffraction (XRD) confirmed the presence of quartz, kaolinite, illite, and hematite as the major mineralogical phases. Scanning electron microscopy revealed loosely stacked, plate-shaped kaolinite particles exhibiting pseudohexagonal morphology. Particle size distribution shows a d50 of 12.7 μm and specific surface area is 21.3 m2/g. Differential thermal analysis-thermogravimetric analysis showed mass losses between 450-600°C and 950-1050°C corresponding to dehydroxylation and formation of a liquid phase, respectively. Dilatometry traced the onset of viscous flow sintering around 1000°C. Test bars produced from the clay were fired at 800°C, 900°C, 950°C, 1000°C, and 1050°C. The firing shrinkage increased from 2.5% at 800°C to 12.8% at 1050°C. Strength improved from 11.2 megapascals at 800°C to 42.3 megapascals at 1050°C due to densification and mullite formation. Hematite content caused the color to change from orange-red at 950°C to dark red at 1050°C. XRD analysis of fired specimens confirmed the presence of hematite and newly formed mullite and cristobalite phases. The results indicate the suitability of the clay for manufacturing bricks, roof tiles, and wall tiles using appropriate firing temperatures and cycles.

Thermal and Structural History of Impact Ejecta Deposits, Ries Impact Structure, Germany

AbstractThe Ries impact structure (Germany) contains well‐preserved ejecta deposits consisting of melt‐free lithic breccia (Bunte Breccia) overlain by suevite. To test their emplacement conditions, we investigated the magnetic properties and microstructures of 26 polymict breccia clasts and a stratigraphic profile from the clasts into the suevite at the Aumühle quarry. Remanent magnetization directions of the Bunte Breccia clasts fall into two groups: those whose directions mostly lie parallel to the reversed field during impact carried mostly by magnetite, and those whose directions vary widely among each clast carried by titanohematite. Basement clasts containing titanohematite acquired a chemical remanent magnetization (CRM) during the ejection process and then rotated during turbulent deposition. Clasts of sedimentary rocks grew magnetite after turbulent deposition, with CRM directions lying parallel to the paleofield. Suevite holds a thermal remanent magnetization carried by magnetite, except for ∼12 cm from the contact with the Bunte Breccia, where hematite concentrations increase due to hydrothermal alteration. These observations lead us to propose a three‐stage model of (a) turbulent deposition of the melt‐free breccia with clast rotation <580°C, (b) deposition of the overlying suevite, which acted as a semi‐permeable barrier that confined hot (<300°C) oxidizing fluids to the permeable breccia zone, and (c) prolonged hydrothermal activity producing further alteration which ended before the next geomagnetic reversal. Basement outcrops have significantly different magnetic properties than the Bunte Breccia basement clasts with similar lithology. Two basement blocks situated near the inner ring may have been thermally overprinted up to 550°C.

The Content of Magnetic Material in Black Sand of Yeh Gangga Beach

Yeh Gangga Beach is one of the black sand beaches in the Tabanan district. The abundant black sand on this beach stretches along the shoreline with varying grain sizes. This black sand characterizes the specific surface composition as iron sand deposits with high magnetic mineral content. The very high need and use of magnetic minerals in various fields prompt a study of the magnetic mineral content in the black sand of Yeh Gangga beach.The magnetic material content was determined by the extraction method which was expressed in terms of mass fraction. The grain size distribution was determined by the sieve method using a sieve shaker consisting of six mesh numbers, namely 30, 100, 170, 200, 270, and 325.The density of magnetic materials was determined by the principle of mass and volume ratio. The magnetic susceptibility was tested by using a Bartington MS2B susceptibility meter. Meanwhile, the characterization of the elements and their oxides used non-magnetic methods, namely the X-Ray Fluorescence test.The research results show that the magnetic material fraction of Yeh Gangga black sand reach 84.84% with 58.39% of the grains having sizes in the range 150r ≥90 μm. The magnetic susceptibility value is 28.26 10-6 m3/kg with an Fe element content of 85.15% w. The hematite (Fe2O3) content reaches 81.69%. This magnetic material has a density of 1914.43 kg/m3.

Research on the Prediction Model of Loess Collapsibility in Xinyuan County, Ili River Valley Area

Collapsibility is a unique engineering geological property of loess. Choosing appropriate parameters to build the prediction model of loess collapsibility is an essential step toward solving the loess collapsibility problem. A case study was performed for the loess in Xinyuan County of the Yili River Basin, China. A large amount of data was collected from preliminary geotechnical tests in this region. Mathematical statistics were applied to analyse the correlations between the loess collapsibility and soil parameters. Multiple linear regression and neural network theories were adopted to build this region’s prediction model of loess collapsibility. The results showed that microscopically, the soils in this region were predominantly flocculated structures. The soil particles were flaky and in bracket contact, and the pores were round or irregularly shaped. Regarding the material composition, the soils were primarily composed of quartz and albite, with a low hematite content. In the study area, the correlation coefficients between the collapsibility coefficient of the loess vs. the density, dry density, saturation, porosity ratio, and porosity varied between 0.628 and 0.857, indicating a strong or very strong correlation. In terms of predicting loess collapsibility, the effectiveness of neural networks based on RBF (radial basis function) and multiple linear regression models was contrasted. The latter was discovered to be more appropriate, dependable, and accurate, with an accuracy percentage of 94.42%. Simultaneously, the model’s assessment index is 0.014 for the root mean squared error (RMSE), 0.962 for the correlation coefficient (CC), 0.919 for the Nash–Sutcliffe efficiency coefficient (NSE), and −1.494 percent for the percent bias (PBIAS). It works well for estimating whether local loess may collapse. Therefore, the RBF neural network model built in the present study has adequate precision and meets the engineering requirements. Our research sheds new light on loess collapsibility assessment in this region.

The Effect of Temperature on Molecular Structure of Medium-Rank Coal via Fourier Transform Infrared Spectroscopy.

Fourier transform infrared spectroscopy (FTIR) was used to study the molecular structure of four medium- and low-temperature heat-treated medium-rank coals. The FTIR spectral parameters, which consist of CH2/CH3, aromaticity (fa), aromatic carbon rate (fC), aromatic hydrogen rate (fH), oxygen-containing (C-O) rate (IR), organic matter maturity (M), and the degree of aromatic condensation (Dc), indicate different characteristics, including changes in the aromatic hydrocarbon structure, fatty hydrocarbon structure, hydroxyl structure, and oxygen-containing functional groups of medium-rank coal. The results show that with the increase in heat treatment temperature, the sulfur content in coal gradually decreases, but the C/H ratio gradually increases. Meanwhile, the content of kaolinite and pyrite in coal gradually decreases, whereas the content of dolomite and hematite gradually increases. With the increase in heat treatment temperature, the relative content of ether oxygen hydroxyl groups in the hydroxyl structure significantly decreases, but the relative content of self-associated hydroxyl groups increases. The relative content of alkyl ether (C-O) in oxygen-containing functional groups gradually increases, whereas the relative content of aromatic nucleus C=C vibration presents a trend of first increasing and then decreasing. In addition, -CH2- is the majority in the structure of fatty hydrocarbons, and the absorption peak intensity of asymmetric -CH3 stretching vibration increases with the increase in heat-treated temperature. The structure of aromatic hydrocarbons mainly consists of four substituted benzene rings (except for R-303.15 K), in which the relative content of the trisubstituted benzene ring decreases with the increase in heat treatment temperature. With the increase in the heat-treated temperature of medium-rank coal, Dc, fH, fC, and fa show a trend of first increasing and then decreasing, M and IR reveal a trend of first decreasing and then increasing, and CH2/CH3 present a gradually decreasing trend. In conclusion, during the increase in the heat treatment temperature of medium-rank coal, the length of the fatty side chains in the fatty hydrocarbon structure becomes shorter, the number of branch chains continuously increases, and the maturity and condensation degree of organic matter first increases and then decreases. On this basis, further research on the effect of coal gasification suggests combining various technologies such as 13C NMR, XRD, and TG-MS to obtain semi-quantitative structural information of molecules in coal from different perspectives.

Falling water tables reduce peatland semiconductor minerals' capacity for preserving carbon

AbstractSemiconductor minerals in peatland play a significant role in the stability of the soil carbon pool. Nevertheless, the ecosystem‐scale importance of semiconductor minerals distribution and their influence on carbon stability in peatlands is still to be determined. Therefore, this study investigated the spatial distribution of semiconductor minerals and their photoelectrochemical activity (PA) in three peatlands with distinct water tables (Equisetum‐swamp [−2.0 cm], Caltha‐meadow [−8.0 cm], and Carex‐meadow [−13.8 cm]). The results indicate that the peatlands of the Qinghai‐Tibet Plateau mainly contain hematite (4.64 wt%), brookite (0.71 wt%), baddeleyite (0.23 wt‰), and zincite (0.10 wt‰); hematite content is the main mineral in peatland. And significantly increased with the decrease of the water table; the photoelectrochemical examination showed that the band gap of semiconductor minerals displayed Caltha‐meadow > Equisetum‐swamp > Carex‐meadow, and the carrier concentration displayed Carex‐meadow > Equisetum‐swamp > Caltha‐meadow, and Carex‐meadow exhibits a steady photocurrent density (0.3 μA/cm2) under light. This suggests that peat soils exhibit an improved photoelectric response with water table drawdown, which would promote the potential for soil carbon mineralization; structural equation model analysis showed that hematite had a significant positive effect on soil organic carbon (SOC), while the PA of semiconductor minerals had a significant negative effect on SOC. That is, semiconductor minerals can not only protect SOC by adsorption but also accelerate organic carbon mineralization by photo‐catalytic generation of reactive oxygen species. Therefore, the decrease in the water table increases the PA of semiconductor minerals, which will weaken the protective effect of semiconductor minerals on soil carbon through adsorption and other means.

Natural and thermally stimulated aging of nanosized powders of cobalt ferrospinel

This article presents the production of nanosized powders of cobalt ferrospinel through mechanochemical synthesis, resulting in an average particle size ranging from 3 to 15 nm. The elemental composition of the nanopowders, analyzed using X-ray fluorescent analysis, is found to be nonstoichiometric and can be represented by the formula: Co0.7±0.05Fe2.3±0.05O4 . When the duration of mechano­chemical synthesis exceeds 25 min, the spinel phase constitutes approximately 90 vol. % in the samples. Additionally, the samples contain hematite phases, the beta modification of iron hydroxide, and an X-ray amorphous phase. Natural aging at room temperature leads to significant changes in the phase composition of the nanopowders. Specifically, there is an increase in the content of spinel phase, while the content of hematite and the amorphous phase decrease significantly. Furthermore, the saturation magnetization and effective field of anisotropy of the cobalt ferrospinel nanopowders exhibit noticeable increments. Consequently, thermal aging of the powders accelerates the changes in phase composition, structural parameters, and magnetic properties, as well as enhances the transformation extent during the formation of cobalt ferrospinel.

Compressibility and small strain stiffness characteristics of silt-hematite mixtures

Iron mining waste is disposed of near mines and forms iron ore (hematite) tailings dams. Furthermore, the distinctive characteristics of hematite particles can affect the geotechnical properties of soil. This study aimed to experimentally examine the compressibility and small-strain stiffness of silt-hematite mixtures. Silt-hematite mixtures were prepared in an oedometer cell at a fixed relative density with different hematite contents (0% to 100% in weight). Vertical displacements and loads were measured with the oedometer, and shear and compression waves were measured using bender and piezo-disk elements, respectively. The results showed that the void ratio and compressibility increased, while the constrained modulus decreased with increasing hematite content as hematite formed porous aggregate owing to high van der Waals forces. The elastic wave velocities (Vs and Vp) and small-strain moduli (Gmax and Mmax) increased with increasing hematite content owing to hematite's high stiffness and coordination number. Furthermore, the elastic wave velocities of high hematite-content specimens were practically constant at low-stress levels (<20 kPa), because of the van der Waals forces being greater than the skeletal forces. This study suggests that the geotechnical properties of hematite-containing soils, hematite-coated soils, and iron ore tailings soils can be evaluated by the hematite ratio.