Mineral Phases Research Articles

Coal structure evaluation and morphological properties that affect the coal usage in industries

AbstractThe contemporary research article is central to understanding coal structure evaluation and the morphological development impacting its utilization in different applications. Through Mineral Liberation Analysis (MLA) designs high content phyllosilicates minerals and swelling clay minerals were rationalized to provides a novel insight into enhanced coal beneficiation and the benefits of coal by-product re-utilization progressions that encourage safer environments and economic sustainability. This work commences with collection of five (5) different coal samples from the central district region in Botswana, sample characterization deploying Thermogravimetric coal analysis (TGA), x-ray fluorescence spectroscopy (XRF), x-ray diffraction (XRD), scanning electron microscopy (SEM) and the Hardgrove Grindability Index (HGI) test that was directed to quantification of the coal hardness and fracture toughness during milling. The cumulative objective was to understand the correlation that exists between the natural composition of the coal sample and their adaptation and application in various carbonaceous products. A solid connection was thus identified in the sulfur and phosphorus weight percentage inclusions in all the coal materials hence higher significance in sphalerite mineral phases (Zn, Fe) S critically increased the fracture toughness and hardness properties. Moreover, mineral amalgams intrinsic to the coal maceral such as aluminum oxides (Al2O3), silicate (SiO2), calcites (CaO), Iron oxide (Fe2O3), potassium feldspars (K − AlSi3O8), albite (Na − AlSi3O8), and anorthite (Ca − Al2Si2O8) compounds in alkali feldspars were detected in larger quantities. The coal industry has attracted much industrial attention to manufacturing foundations producing cement, ceramic tiles, paving bricks, and material synthesis and will continue to supply other economic sectors in the conceivable future. Graphical Abstract

Chalcopyrite CuFeS2: Solid-State Synthesis and Thermoelectric Properties

The optimal conditions for synthesizing a pure chalcopyrite CuFeS2 phase were thoroughly investigated through the combination of mechanical alloying (MA) and hot pressing (HP) processes. The MA process was performed at a rotational speed of 350 rpm for durations ranging from 6 to 24 h under an Ar atmosphere, ensuring proper mixing and alloying of the starting materials. Afterward, MA-synthesized chalcopyrite powder was subjected to HP at temperatures between 723 K and 823 K under a pressure of 70 MPa for 2 h in a vacuum. This approach aimed to achieve phase consolidation and densification. A thermal analysis via differential scanning calorimetry (DSC) revealed distinct endothermic peaks at the range of 740–749 K and 1169–1170 K, corresponding to the synthesis of the chalcopyrite phase and its melting point, respectively. An X-ray diffraction (XRD) analysis confirmed the successful synthesis of the tetragonal chalcopyrite phase across all samples. However, a minor secondary phase, identified as Cu1.1Fe1.1S2 (talnakhite), was observed in the sample hot-pressed at the highest temperature of 823 K. This secondary phase could result from slight compositional deviations or local phase transformations at elevated temperatures. The thermoelectric properties of the CuFeS2 samples were evaluated as a function of the HP temperatures. As the HP temperature increased, the electrical conductivity exhibited a corresponding rise, likely due to enhanced densification and reduced grain boundary resistance. However, this increase in electrical conductivity was accompanied by a decrease in both the Seebeck coefficient and thermal conductivity. The reduction in the Seebeck coefficient could be attributed to the higher carrier concentration resulting from improved electrical conductivity, while the decrease in thermal conductivity was likely due to reduced phonon scattering facilitated by the grain boundaries. Among the samples, the one that was hot-pressed at 773 K displayed the most favorable thermoelectric performance. It achieved the highest power factor of 0.81 mWm−1K−1 at 523 K, indicating a good balance between the Seebeck coefficient and electrical conductivity. Additionally, this sample achieved a maximum figure-of-merit (ZT) of 0.32 at 723 K, a notable value for chalcopyrite-based thermoelectric materials, indicating its potential for mid-range temperature applications.

Characteristics of Solid Mineral Phase Transitions During Sulfuric Acid Production from Gaseous-Sulphur-Reduced Gypsum

The acid co-production of cement is a prominent research focus for the large-scale, high-value utilization of phosphogypsum in the context of dual-carbon strategies. This paper builds on extensive research conducted by its authors on the co-production of sulphoaluminate cement clinker through acid production from gaseous-sulphur-reduced phosphogypsum. The solid mineral phase transformations occurring in the kiln during this process are systematically studied, and the effects of various calcination regimes (temperature, time, and atmosphere) on the evolution of clinker mineral phases are elucidated. This paper provides basic data support for the gas-sulfur-reduced phosphogypsum-acid cogeneration of sulfoaluminate cement clinker processes, and promotes the realization of the large-scale high-value utilization of phosphogypsum resources. The generation of the clinker mineral phase anhydrous calcium sulphoaluminate (C4A3S̅) begins at 1100 °C. Increasing the calcination temperature and extending the calcination time promote C4A3S̅ formation. However, when the calcination temperature exceeds 1350 °C, C4A3S̅ decomposes, leading to the formation of low-activity C2AS. In a CO atmosphere, the main mineral phases in the clinker transform into C2AS and 12CaO·7Al2O3, owing to the decomposition of CaSO4, which inhibits C4A3S̅ formation. At calcination temperatures exceeding 1300 °C, a significant amount of C2AS appears in the calcined material, and 12CaO·7Al2O3 begins to form.

AUGITE-BASED CERAMICS OBTAINED BY SOLID-STATE SINTERING OF LOESS

Loess from the Danubian Plain (Bulgaria) was used as the raw material for the solid-state synthesis of ceramics.The mineral phase composition of the loess fraction used was determined by powder X-ray phase analysis, and the chemical composition by X-ray fluorescence analysis. The semi-quantitatively determined mineral phases are quartz, plagioclase, K-feldspar, mica, carbonates (calcite and dolomite), chlorite and amphibole. The major oxides of the chemical composition of loess fraction are (in wt. %): SiO2 - 53,61; Al2O3 - 12.57; Fe2O3 - 7.05; P2O5 - 0,23; TiO2 - 1.37; CaO - 19.36; and MgO - 1.48. Experiments were performed with sintering of pure loess without additives, and with addition of MgO and Na2O in order to obtain a composition corresponding to that of the pyroxene augite - (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6. Ceramics were obtained at three temperatures: 1000, 1100 and 1200°C. The phase composition, spectral characteristics and colour coordinates of the obtained ceramics were determined. The results show that when magnesium and sodium are added to the loess raw material, the ceramics obtained after sintering at 1100 and 1200°C have a predominant content of augite and have a yellow-beige colour.

El Zorro: early Jurassic intrusion-related gold (IRG) mineralization in the oldest, western-most segment of the Andean Cordillera of Northern Chile

AbstractThe El Zorro gold district is the most recent gold discovery in the Coastal Cordillera of northern Chile. Ternera is the largest deposit in the district with total resources currently estimated at 1.282 Moz. New geology, geochemistry and geochronology data indicate that hydrothermal mineralization is mostly hosted within felsic to intermediate, ilmenite-bearing calc-alkaline dikes and stocks of the Upper Triassic to Lower Jurassic Relincho Pluton, and some of the adjacent Devonian to Carboniferous metasediments of the Chañaral Epimetamorphic Complex. Sheeted veins, veinlets, and fault zones with quartz, low amounts of pyrite, pyrrhotite and arsenopyrite, and local calcite are surrounded by narrow haloes of albite-biotite-quartz ± sulfides-K-feldspar-sericite-chlorite. Gold (mostly in the veins) is associated with elevated W-Bi and also As-Te-Sn, and not with iron enrichment or base metals, even though this system is proximal (~ 20 km) to IOCG and IOA deposits of the Coastal Cordillera. The main phase of gold mineralization occurred soon after emplacement of tonalitic dikes and granodiorite from the Relincho and Cuevitas plutons (U–Pb zircon between ~ 205 and 190 Ma), about 80 m.y. later than the development of orogenic fabrics. An absolute upper age limit is provided by compositionally distinct ore-cutting mafic dikes dated at 175–170 Ma (U–Pb apatite). The deposit falls into the intrusion-related gold category, as indicated by the cutting of earlier orogenic fabrics, the metal and alteration associations, and the spatial and temporal connection to reduced ilmenite-series intrusions, which are also very similar geochemically to the ‘type-locality’ IRG intrusions of the Tintina Belt in Yukon/Alaska. The El Zorro gold district represents the oldest and geologically western-most mineralizing event in the Central Andes of northern Chile, consistent with its time–space placement within the tectonic framework of easterly-younging mineralization and igneous activity in the Chilean Cordillera.

Mineral composition of xenoliths of transformed tholeiitic basalts in ore-hosting rocks of the Rudnogorskoe iron ore deposit, Eastern Siberia

Research subject. Variously-altered tholeiitic basalt xenoliths in ore-hosting rocks from the Rudnogorskoe iron ore deposit, the Angaro-Ilim region of Eastern Siberia. Aim. To identify the sequence of mineral transformations during the formation of magnetite ores. Materials and methods. The mineral composition of weakly-altered and hematitized xenoliths of tholeiitic basalts in skarned rocks and relics of basaltic hyaloand lithoclasts in varying degrees magnetitized volcaniclastites were studied. Minerals were identified using a powder X-ray diffractometer with the determination of the quantitative ratios of mineral phases by SHIMADZU XRD-6000 and DRON-2.0 diffractometers and using the microscopic (Olympus BX51) and electron microscopic (Tescan Vega 3 sbu with an Oxford Instruments Xact energy-dispersive analyzer) and IR spectroscopic (Spectrum One IR Fourier-spectrometer and a Multiscope microscope, PerkinElmer) research methods. Results. In xenoliths of weakly-altered tholeiitic basalts, volcanic glass is smectitized and partially replaced by secondary aggregates of chlorite and carbonate. In hematitized xenoliths, the smectite-hematite mineral association contains skarn epidote and garnet. Smectite aggregates, partially transformed into magnetite mass, are present in the magnetitized volcaniclastites. The studied smectites are classified as saponite according to the obtained values of basal reflections d001 in the range of 14.76–15.23 Å and calculated crystal chemical formulas. The differences in the morphology, chemical composition, and IR spectrometric characteristics of smectites reflect the varying degrees of transformation of the tholeiitic basalts in multi-stage ore-forming processes.

Unlocking underground hydrogen storage potential: Geochemical characterization of North Dakota's geological formation

Underground hydrogen storage offers a promising solution for sustainable energy, with geologic formations such as salt caverns, aquifers, and depleted hydrocarbon reservoirs identified as suitable options for safely storing hydrogen. Some studies have been carried out to investigate hydrogen-rock-fluid interactions. However, none have simultaneously combined experimental analysis and geochemical modeling of the equilibrium and kinetic reactions using a well-characterized North Dakota carbonate formation as a case study to investigate its geochemical characterization and implications. This research explores the mineralogical and fluid composition of specific depleted hydrocarbon reservoirs in North Dakota while investigating the intricate geochemical interplays between hydrogen gas, fluid, and rock formations. This study focused on the Red River Formation, a primary hydrocarbon-producing entity in North Dakota, to unveil its potential for underground hydrogen storage (UHS). This formation's stratigraphic complexity and extensive hydrocarbon yield underscores its significance. We conducted experiments combining analytical tests and geochemical modeling using core samples from the Red River Formation. X-ray diffraction (XRD), X-ray fluorescence (XRF) spectroscopy, and scanning electron microscopy (SEM) techniques were employed to decipher mineralogical and elemental constituents. This study covers areas such as the Bicentennial, Coyote Creek, Horse Creek, and Medicine Poll Hills Fields and identified common minerals such as calcite, dolomite, anhydrite, and quartz, along with essential elements such as oxygen, magnesium, aluminum, and silicon. Geochemical simulations were also performed to evaluate the equilibrium and kinetic reactions expected during hydrogen gas injection into this formation. Our findings revealed stable mineral phases, the absence of detrimental environmental impacts, promising prospects for hydrogen storage in the studied carbonate reservoirs without geochemical alterations and promising a sustainable pathway toward net-zero carbon emissions.

Automated identification of soil functional components based on NanoSIMS data

NanoSIMS technique allows to investigate the micro-spatial organization in complex structures in multiple scientific fields such as material science, cosmochemistry, and biogeochemistry. In soil biogeochemistry applications, NanoSIMS-based approaches aim to disentangle the interactions of organic matter (OM) and mineral phases in the heterogeneous soil microstructure. Investigating the spatial arrangement of distinct organic and mineral functional components is necessary to understand how these components interact and contribute to biogeochemical processes in soil systems. Identifying soil functional components within NanoSIMS measurements necessitates advanced and efficient data processing tools capable of accessibility and automation. We have developed a pre-processing tool to streamline NanoSIMS data preparation and handling. The tool is provided as an open-source software toolbox (NanoT). In addition, a two-step unsupervised segmentation method was developed to identify soil functional components based on NanoSIMS analyses. To illustrate the segmentation method, here we describe its application to two exemplary NanoSIMS measurements. This allows to distinguish mineral- and OM-dominated regions, as well as different mineral phases. To improve the detection of iron oxides and aluminosilicates, the 56Fe16O− channel was separately processed. The presented NanoSIMS-based processing workflow helps to disentangle functional components within a biogeochemically-diverse microstructure in soils and further warrants applications to a wide range of complex environmental samples.

Cooperative stabilization of calcium carbonate powder, blast furnace slag, and white cement in composite concrete: Volume variation and hydration behavior

Volume stability was an important property of white concrete in long-term service. The purpose of this research is that volume stability of composite concrete was advanced by synergy of calcium carbonate powder and blast furnace slag, and its related hydration behavior was revealed. The results manifested that the early shrinkage, dry shrinkage, and creep of calcium carbonate powder-blast furnace slag-based white concrete (C20) were the lowest as content of calcium carbonate powder and blast furnace slag were 20 % and 10 %. Furthermore, early shrinkage, dry shrinkage, creep, and 120-days compressive strength of C20 were 52.49 %, 24.83 %, 22.47 %, and 82 MPa respectively, which superior to those of others white concrete. These results indicated that the long-term volume stability and strength of C20 was optimal. Information of hydration heat showed that accumulate hydration heat about C20 was minimum (226.91 J/g). This find proved that the effects of thermal expansion and cooling shrinkage on the volume of C20 were ameliorated efficiently. The results of microstructure, mineral phase, and pore structure demonstrated that dense degree of white concrete was boosted by flocculation gel product and rod ettringite. Therefore, the volume stability of white composite concrete could be enhanced by synergy of calcium carbonate powder, blast furnace slag, and white cement.

Adaptability analysis of H2-rich gas injection and sintered ore performance with different raw material ratios

As a source substitution technology that reduces pollutants emission and optimizes sinter properties, H2-rich gas injection-assisted iron ore sintering holds significant practical value. This study analyzed the adaptability of this technology to different ore blend ratios and basicity levels by comparing sintering indexes, pore structure, mineral phase composition, and metallurgical performance before and after H2-rich gas injection. The carbon emission reduction following H2-rich gas injection was calculated. The results indicate that increasing the proportion of high-silica, low-alumina ore (Ore-A) and basicity, along with H2-rich gas injection, can effectively enhance sinter yield and quality, but shrink the pore structure of sinter. Under H2-rich gas injection conditions, decreasing Ore-A ratios and increasing basicity can augment SFCA phase formation and mineral phase uniformity, thereby improving the anti-pulverization ability and reductivity of the sinter. H2-rich gas injection presents better adaptability to sintered ore with lower Ore-A ratio and basicity, which can achieve greater improvements in the sintering indexes, RDI, and RI. For a 265 m2 sinter plant producing sinter with 18 wt.% Ore-A and 2.0 basicity, annual CO2 emissions can be reduced by approximately 40,000 t.

Zircon and garnet U-Pb dating reveals the mineralization history of volcanic-related skarn iron deposits

The genesis of skarn garnet in volcanic-related skarn iron deposits is controversial because of the absent or ambiguous spatiotemporally related intrusions. In this study, we present combined LA-ICP-MS garnet U-Pb and SHRIMP zircon U-Pb ages to determine the spatiotemporal relationship between skarn garnet and a potentially related intrusion or causative volcanic rock. Three types of garnet (Grt1, Grt2, and Grt3) are identified in the Yamansu deposit, and Grt1 yields a lower intercept age of 326 ± 9 Ma (n = 32, MSWD = 0.3). SHRIMP zircon U-Pb dating of the associated volcanic rock yields a weighted mean age of 327 ± 3 Ma (n = 10, MSWD = 1.4), suggesting an isochronous relationship between the volcanic rock and Grt1. Grt2 and Grt3 yield lower intercept ages of 316 ± 6 Ma (n = 22, MSWD = 1.4) and 315 ± 6 Ma (n = 35, MSWD = 1.5), respectively. However, the zircon U-Pb weighted mean age of 252 ± 4 Ma (n = 5, MSWD = 0.8) obtained from the associated intrusion is obviously younger than the skarn age and the previously reported ore-forming age, implying no temporal relationship between mineralization and the intrusion. More significantly, precise 206Pb/238U weighted mean ages of 325 ± 9 Ma (n = 15, MSWD = 0.3), 316 ± 8 Ma (n = 11, MSWD = 0.4), and 319 ± 7 Ma (n = 12, MSWD = 0.5) were obtained from Grt1, Grt2, and Grt3, respectively, and we find that andradite-rich garnet with high U and ΣREE concentrations has the potential to yield the more precise U-Pb ages. The combined garnet and zircon U-Pb ages reveal that the hydrothermal skarn and mineralization in volcanic-related skarn iron deposits are related to volcanic activity rather than intrusions. Multiple episodes of volcanic-related hydrothermal activity may have caused multiple phases of skarn formation and mineralization in volcanic-related skarn iron deposits.

Study on the effect and mechanism of coarse magnetite on the flotation of fine-grained hematite

Lean hematite ore is one of the refractory iron ores in China due to its fine crystal size, deep oxidation degree and complex mineral composition. With the deep mining of mine ore, the disseminated particle size of iron minerals is finer, and the ore properties are more complex and difficult to be separated. Therefore, the research on high-efficiency beneficiation technology of fine-grained lean hematite ore is the requirement and important direction of the development of refractory iron ore beneficiation. In this paper, the carrier flotation method is used to comprehensively recover hematite, and the addition of coarse-grained magnetite can effectively improve the recovery rate of fine-grained hematite. The flotation results show that when the ratio of magnetite to hematite is 1: 1, the recovery rate of iron ore can reach more than 96.34%, and the efficient recovery is realized. Based on the results of pure mineral test, the carrier flotation test of Anshan lean hematite ore was carried out. The results show that the reverse flotation concentrate product with TFe grade of 67.88% and total iron recovery of 84.81% can be obtained, and the TFe grade of the reverse flotation tailings is 24.20%. It can be seen that compared with the traditional process, the grade of carrier flotation tailings is 2.37 percentage points lower than that of the original reverse flotation tailings; the carrier reverse flotation process can effectively improve the recovery rate of iron concentrate. In addition, the theoretical analysis of carrier flotation was carried out by contact angle, zeta potential, mineral phase microscope, SEM and XPS. It was found that the collision probability between fine mineral particles and bubbles was low, which limited the recovery of fine mineral particles in the flotation process. Fine-grained hematite can be non-selectively attached to the carrier particles, thereby affecting the adsorption of starch on it, thereby improving the recovery rate of fine particles; The carrier reverse flotation can further improve the flotation efficiency by gravity and shear force. Carrier reverse flotation provides a new idea for effective recovery of iron ore.

In-situ trace element and sulfur isotope compositions of Multi-Stage sulfides in the Buzhu orogenic gold (Antimony) Deposit, southern Tibet: Implications for the metallogenic process

The Buzhu gold (antimony) deposit, located within the gold-antimony polymetallic belt of southern Tibet in the Tethys Himalayan belt, is a recently discovered medium-sized gold polymetallic deposit. The orebody consists primarily of gold-bearing quartz sulfide veins. Currently, the metallogenic mechanism of the deposit remains largely unexplored. Utilizing results from the mineralogical observation of principal ore minerals, LA-ICP-MS trace element analysis, and in-situ sulfur isotope analysis of pyrite, investigations reconstruct the evolution process of pyrite-arsenopyrite and constrain the metallogenic process of the Buzhu gold (antimony) deposit. It has been discovered that the gold-bearing sulfides in the Buzhu gold (antimony) deposit are primarily pyrite and arsenopyrite. Pyrite can be categorized into six generations: framboidal pyrite Py0, dissolution cavity pyrite Py1a (some exhibiting oscillatory zoning), disseminated pyrite Py1b, euhedral pyrite Py2a, irregular pyrite Py2b, and Py3. Arsenopyrite, on the other hand, can be classified into three generations: early arsenopyrite Apy0, disseminated arsenopyrite Apy1, and euhedral Apy2. The analysis of δ34S in pyrite throughout the ore-forming process indicates sulfur derives from multiple sources, with Py0 indicative of a biological sulfur source. The evolutionary process of pyrite, supported by trace element analysis, suggests that the remaining pyrite derives from sedimentary fluid transformation, with sulfur primarily sourced from metamorphic sediments. Elemental spectrum analysis and BSE observations indicate that the Buzhu gold (antimony) deposit primarily undergoes two distinct stages of mineralization: the initial stage is the gold-antimony mineralization phase, during which antimony precipitates in the fissures of Py1a as stibnite, while gold is primarily found in Py1-Apy1 as invisible gold, with the highest gold content in Apy1 (28.20–60.13 ppm, average 40.51 ppm). The subsequent stage of mineralization is characterized by gold mineralization, with gold primarily residing in the internal fissures of Apy2 as micron silver gold ore. The evolution characteristics of gold-bearing sulphide and the solubility curve of Au indicate that gold mainly derives from gold-bearing unsaturated fluid, rather than from early framboidal pyrite Py0 (0.52–1.06 ppm, average 0.79 ppm). Only a minor fraction of gold (originating from early sediments) in Py0 was liberated and integrated into subsequent pyrites. The content of antimony in Py0 significantly reduces after dissolution, suggesting that antimony predominantly originates from Py0 (206–440 ppm, average 335 ppm). Throughout the genesis of the Buzhu gold (antimony) deposit, the gold constituent underwent a sequence of pre-enrichment, re-enrichment, liberation, and precipitation. The processes of coupled dissolution-reprecipitation (CDR) and boiling fostered the reactivation and reenrichment of gold. The recrystallization into cubic pyrite led to the expulsion of gold from the pyrite lattice, and fluid oxidation resulting from multistage fluid boiling, coupled with a decrease in sulfur fugacity, led to gold precipitation.

Density functional theory study on vanadium selective leaching separation from iron in stone coal via Fe2O3 (001) surface passivation

When vanadium is extracted from stone coal, iron impurities readily precipitate and reduce the purity of the vanadium product. Thus, separating vanadium from iron impurities at source is essential. The mechanism of surface passivation of Fe2O3 (001) for the selective leaching separation of vanadium from iron in stone coal was established in the present work. Analysis of mineral phase transformation and microscopic morphology indicates that Fe2O3 in stone coal can undergo a reaction with HF and F-. Subsequently, the hematite surface was covered with FeF3 passivation layer, resulting in the inhibition of hematite dissolving reaction. The results of density functional theory (DFT) computations demonstrate that the HF and F- can reform the Fe2O3 (001) surface via sedimentary behavior at mineral interface, and the adsorption energy can be down to -99.93kJ/mol for the F- adsorption configuration. During sulfuric acid leaching with CaF2 as an aiding agent, the transfer of electrons from Fe atoms to F atoms can weaken the stable Fe-F bonds and decrease the reactive activation of Fe atoms in Fe2O3. This study demonstrates the separation of vanadium from iron by means of hematite passivation in the attendance of fluoride at the atomic level of analysis.

Polymetallic red mud direct materialization strategy towards zero waste emission: Electromagnetic wave absorption conversion and sodium solidification

Red mud is an industrial hazardous alkaline solid waste, whereas it is rich in polymetallic components showing a high comprehensive utilization value. Direct materialization of red mud towards zero waste emission is a more reasonable and environmentally friendly strategy. In this work, a novel materialization approach of red mud via converting the polymetallic constituents into functional ferrite material by phase reconstruction with MnO2 was proposed. The mineral phase reconstruction, microstructure evolution, reaction interface observation, electromagnetic property, and the materialization conversion mechanism were investigated. It was found that the complicated phases in red mud were transferred to simple forms including the magnetic ferrites (Ca/Na/Al/Ti-bearing Mn ferrite) and weakly magnetic silicates ((Na,Al,Ca)2SiO3) after phase reconstruction. The reconstructed red mud after sintering at 1200 ℃ for 120min in air atmosphere had satisfactory electromagnetic property. Magnetism study demonstrated the soft magnetic property with maximum saturation magnetization of 34.22emu/g and coercivity of only 7.0Oe. Compared with the original red mud, effective electromagnetic wave absorption with reflection loss (RL) values of the reconstructed red mud below -20 dB were satisfied across a wider frequency bandwidth of 5-18GHz, and the minimum RL value was lower as -32.4dB with a thinner veneer thickness of 15mm, highlighting its excellent electromagnetic wave absorption performance. Moreover, Na solidification behaviors indicated that Na was solidified in the sintered product, which can reduce the possible environmental hazards of red mud alkalinity. The novel materialization treatment with zero waste emission exhibits a favorable application prospect with a large red mud batching ratio about 50wt%.

Preliminary investigation on spent garnet as a novel supplementary cementitious material

The escalating global demand for cement, a fundamental material in infrastructure development, has exacerbated environmental challenges, particularly through significant carbon dioxide (CO₂) emissions, which account for approximately 8.3 % of global anthropogenic CO₂ output. This research explores the potential of spent garnet powder, a byproduct of abrasive water jet machining, as a sustainable supplementary cementitious material (SCM) to mitigate these impacts. The spent garnet powder, characterized by a high concentration of silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), and iron oxide (Fe₂O₃), was subjected to rigorous analysis. X-ray Fluorescence (XRF) confirmed its chemical suitability for pozzolanic applications, while laser particle size analysis revealed a finer granulometry relative to Ordinary Portland Cement (OPC), which is advantageous for enhancing pozzolanic reactivity. Scanning Electron Microscopy (SEM) demonstrated the angular and irregular morphology of the garnet particles, which is conducive to improved interfacial bonding within the cement matrix. X-ray Diffraction (XRD) identified active mineral phases that are critical for promoting pozzolanic reactions, and Thermogravimetric Analysis (TGA) demonstrated the material’s superior thermal stability, with minimal decomposition at elevated temperatures. Fourier Transform Infrared Spectroscopy (FTIR) identified strong silicon-oxygen (Si-O) and aluminum-oxygen (Al-O) bond structures, indicative of robust pozzolanic potential. The Strength Activity Index (SAI) and Frattini tests further substantiated the pozzolanic activity, revealing that a 10 % replacement of OPC with SGP not only enhances compressive strength but also meets the stringent requirements of ASTM C618. Additionally, the economic analysis underscores the cost-effectiveness of utilizing spent garnet powder, presenting a viable strategy for reducing both production costs and CO₂ emissions in the cement industry. This study conclusively positions spent garnet powder as a highly promising supplementary cementitious material, with significant implications for advancing sustainable construction practices and reducing the environmental footprint of cement production.

Sapphirine + quartz assemblage from the Irumide Belt, northern Malawi: Implications for Mesoproterozoic ultrahigh-temperature metamorphism related to Rodinia assembly

The Irumide Belt sensu lato situated between the Bangweulu Block to the northwest and the Neoproterozoic Mozambique–Zambezi Belt to the southeast is a Mesoproterozoic orogenic belt that developed probably during the amalgamation of the supercontinent Rodinia. In this study, we present new petrological, geothermobarometric, and geochronological data of pelitic granulites and related rocks from the Jenda area in northern Malawi, and evaluate the timing and pressure–temperature (P–T) conditions of high-grade metamorphism. To the best of our knowledge, we are the first to report the occurrence of sapphirine + quartz association in pelitic granulite from the Irumide Belt sl. which provides a robust evidence of peak ultrahigh-temperature (UHT) metamorphism. The sapphirine occurs as poikiloblastic grains with rounded quartz inclusions in the absence of any retrograde minerals. The mineral phase equilibrium modeling constrains the peak UHT conditions of the pelitic granulites as 950–1000 °C and 7–8.5 kbar for sapphirine-bearing and ∼6 kbar and > 950 °C for sapphirine-free samples. These conditions are consistent with the results of ternary-feldspar geothermometry (900–1000 °C at 8 kbar). From the stability of rutile, we estimate a prograde pressure of >9 kbar, and the occurrence of retrograde cordierite and biotite suggests that the rocks went through P–T conditions of ∼6–7 kbar/∼775–825 °C, indicating a clockwise P–T path and defining high-pressure and UHT conditions. In-situ monazite Th–U–Pbtotal geochronology of the sapphirine-bearing rock yielded a weighted-mean age of 1022 ± 10 Ma which is considered to mark the timing of peak metamorphism. Sapphirine-free granulites also gave consistent ages of 1049 ± 13 Ma and 1048 ± 10 Ma, which are also comparable with published ages. We thus infer that the Irumide Belt sl. underwent regional high-pressure to UHT metamorphism at ca. 1.05 to 1.02 Ga possibly related to the main collisional event of the Bangweulu Block with an unknown craton or magmatic arc during the assembly of Rodinia supercontinent.

A Northgrippian sedimentary magnetic enhancement along the western margin of India

Sedimentary magnetic records of shelf region contains complex environmental evolution information, necessitating records from various global regions to accurately interpret its significance. A sediment core (SSD-39/GC-01) retrieved from the eastern Arabian Sea was analyzed to elucidate the geologic and climatic controls on the sediment rock magnetic and grain size properties. We report the first record of high energy sediment deposits linked with intense monsoon phases, sea level variations, and extreme natural events during the Northgrippian period (8.27 ka to 4.20 ka). The compilation of magnetic susceptibility profiles of six sediment cores from the western margin of India revealed the presence of multiple sedimentary intervals of enhanced magnetic susceptibility and most likely reflect periods of high sedimentation events controlled by the regional geologic and climatic processes. We identified two anomalous sedimentary magnetic zones (Z-II, Z-IV) marked by an elevated magnetite content and sediment grain size, which reflect the periods of high-sedimentation events on the shelf off Goa. A shift in the magnetic mineral composition, clastic grain size, calcium carbonate, and organic carbon content at ~1.8 ka (Z-I) indicate a abrupt change in monsoon intensity. The elevated organic content within Z-I indicate efficient preservation of labile organic matter which survived oxidation due to rapid sediment deposition. End-member modeling of rock magnetic and grain size properties enabled us to discriminate and quantify the contributions of terrigenous fluxes and post-depositional mineral phases to the bulk magnetic mineral assemblage. We demonstrate that rapid scanning of magnetic susceptibility of sediment cores has the potential to precisely detect the periods of increased continental (magnetic flux) inputs into the marine shelf system. The proposed magnetic mineralogical approach has wider scope to constrain the understanding of how shelf sedimentation responded to past geological and climatic conditions globally.

Endochondral ossification: insights into the cartilage mineralization processes achieved by an anhydrous freeze substitution protocol

Growth plate cartilage (GP) serves as a dynamic site of active mineralization and offers a unique opportunity to investigate the cell-regulated matrix mineralization process. Transmission electron microscopy (TEM) provides a means for the direct observation of these mechanisms, offering the necessary resolution and chemical analysis capabilities. However, as mineral crystallinity is prone to artifacts using aqueous fixation protocols, sample preparation techniques are critical to preserve the mineralized tissue in its native form. We optimized cryofixation by high-pressure freezing followed by freeze substitution in anhydrous acetone containing 0.5% uranyl acetate to prepare murine GP for TEM analysis. This sample preparation workflow maintains cellular and extracellular protein structural integrity with sufficient contrast for observation and without compromising mineral crystallinity. By employing appropriate sample preparation techniques, we were able to observe two parallel mineralization processes driven by chondrocytes: 1) intracellular- and 2) extracellular-originating mineralized vesicles. Both mechanisms are based on sequestering calcium phosphate (CaP) within a membrane-limited structure, albeit originating from different compartments of the chondrocytes. In the intracellular originating pathway, CaP accumulates within mitochondria as globular CaP granules, which are incorporated into intracellular vesicles (500-1000 nm) and transported as granules to the extracellular matrix (ECM). In contrast, membrane budding vesicles with a size of approximately 100-200nm, filled with needle-shaped minerals were observed only in the ECM. Both processes transport CaP to the collagenous matrix via vesicles, they can be differentiated based on the vesicle size and mineral morphologies. Their individual importance to the cartilage mineralization process is yet to be determined. Statement of SignificanceWe do not fully understand the process by which epiphyseal cartilage mineralizes - a vital step in endochondral bone formation. Previous work has proposed that mitochondria and intracellular vesicles are storage sites for the delivery of mineral to collagen fibrils. However, these concepts are founded on results from in vitro models of mineralization; no prior work has observed mineral-containing intracellular vesicles or mitochondria in developing epiphyseal cartilage. Here we developed a new cryofixation preparation route for transmission electron microscopy (TEM) imaging that has disclosed a cell-regulated process of mineralization in epiphyseal cartilage. High resolution TEM images revealed an involvement of mitochondria and intracellular and extracellular vesicles in delivering transient mineral phases to the collagen fibrils to promote cartilage mineralization.

Effect of different calcination temperatures on clinker and hydration properties of solid waste-based calcium sulfoaluminate cement

Calcium sulfoaluminate (CSA) cement is a promising alternative to Portland cement for reducing CO2 emissions in the cement industry. In this study, solid-waste-based calcium sulfoaluminate cement (SWCSA) was synthesized from steel slag, phosphogypsum, carbide slag, and bauxite. The effects of calcination temperature (1190–1310 °C) on the properties of the SWCSA clinker before and after hydration were studied, and the hydration process was simulated. The main mineral phases of the clinker were C4A3S̅, C2S, and C4AF. During calcination, Fe³⁺ could replace Al3+ in C4A3S̅ to generate C4A3S̅-c. As the calcination temperature increased, the extent of Fe3+ substitution increased, resulting in more C4A3S̅-c, and the amount of C4AF decreased. The element distribution diagram shows the distribution of minor elements in different phases (such as Ti, Mg and K). In terms of physical properties, the SWCSA setting time was prolonged upon increasing the calcination temperature. Furthermore, SWCSA with the best 28 d compressive strength (89.7 MPa) was obtained at a low calcination temperature (1190 °C). During hydration, the initial SWCSA hydration rate was fast, a large amount of ettringite was generated, and the cumulative hydration heat was low. The ratio of the amount of ye'elimite consumed to the initial amount was positively correlated with the compressive strength. In addition, a relationship was observed between AFt/AH3 and the compressive strength. Overall, SWCSA could be prepared at a lower calcination temperature than conventional CSA, offering a new avenue for recycling industrial solid waste via a less-energy-intensive process to obtain high-performance cementitious materials.