Mode Of Occurrence Research Articles

Exploring default-interventionist interaction of thinking activity types on probability problem-solving

This research aims to determine the thinking activity types dominated by a mental process in producing answers characterized by automatic, unconscious, and subjective-empirical processes (system 1) in solving problems so that the default-interventionist interaction occurs. This research novelty is the formulation of the contents and thinking activity arrangement adapted to students' thinking when solving problems. The problem used in this research is a mathematical problem that triggers students to produce answers quickly with confidence that the answers are correct at a high level. Another problem is about probability because the mode of occurrence of students' learning difficulties at the secondary school level occurs when learning the concept of probability. This is qualitative research with a case study approach. The research subjects were students of Mathematics Education in semester 1. The results showed that thinking activity one could condition the occurrence of type 1 default-interventionist interaction. Thinking activity two could condition the occurrence of type 2 default-interventionist interaction. Thinking activity three could condition the occurrence of type 3 default-interventionist interaction. This research concluded that the default-interventionist interaction occurred because the content and arrangement of the thinking activity conditioned the subjects to pay attention to information gradually and change the subjects’ beliefs. Lecturers were recommended to produce, develop, and research thinking activities on topics other than probability at various levels of education. The default-interventionist interaction was essential to be conditioned when system one dominated students' thinking, causing difficulties.

Geochemistry of the Leatherwood coal in eastern Kentucky with an emphasis on enrichment and modes of occurrence of rare earth elements

The Middle Pennsylvanian (Bolsovian) Leatherwood coal in the central part of eastern Kentucky is a moderately thick, moderate-S seam that has been one of the major energy resources in the region. Much of the seam profile consists of clarain, dull clarain, and durain with some brighter lithologies at the base of the seam and in the upper portion of the coal at one site. A previous study emphasized petrographic trends. In this investigation, the geochemistry of the coal is examined. Some elements, such as Ge and Ga, are enriched at 2× and 5× the World hard coal averages in the coal lithotypes adjacent to rock (roof, floor, partings). Arsenic and other chalcophile elements (Zn, Co, Ni) tend to be concentrated at the top and bottom of the seam profiles and below partings, generally in the coals with the highest pyritic sulfur content. Manganese enrichments occur in bright clarain lithologies at one site. No coal lithology reaches a 5× the World hard coal average, but samples between the 2× and 5× World hard coal averages tend to be at the top and bottom of the coal seam. Most coal samples tend to have a light rare earth element (LREE) enrichment. The basal lithotype at all sites, though, has a heavy REE enrichment and, via inference from the Zr and TiO2 concentrations, a smaller influx of detrital minerals than the basal lithotypes in many Appalachian coals. While the nature of REE associations is complicated by the high volatile A bituminous coal rank, the relatively high concentrations of the heavy REE suggest an original, albeit possibly not exclusive, organic association for those elements.

Field and petrological characteristics of PGE-rich podiform chromitites: Implications for efficient exploration

Two distinct types of podiform chromitites have been extensively described within the mantle sections of Neoproterozoic ophiolites in Saudi Arabia and Phanerozoic ophiolites in Oman. The first type is concordant with the foliation plane of the harzburgite host, generally lensoidal in shape and is characterized by its low platinum-group elements (PGE) contents. The second type occurs as discordant or dike-like bodies and predominantly rich in PGE. In addition to their mode of occurrence, several lines of evidence can be employed to differentiate these two types of chromitites, both in the field and during laboratory investigations. Concordant PGE-poor chromitites are typically homogeneous in appearance (with regards to chromite grains distribution) and massive, featuring chromian spinel (Cr-spinel) with olivine as the dominant silicate inclusions. In contrast, discordant PGE-rich chromitites are often heterogeneous in appearance, exhibiting a semi-massive to disseminated, and are rich in both hydrous (amphiboles) and anhydrous (clinopyroxene) silicate inclusions. Discordant dunite veins, sharing similar petrological characteristics, are consistently associated with PGE-rich chromitites, with Cr-spinel containing a notable abundance of clinopyroxene inclusions. Compared to podiform chromitites found worldwide, concordant chromitites have lower to intermediate PGE contents (typically < 500 ppb), display a gently sloping negative trend in PGE patterns, contain very few platinum-group mineral (PGM) grains, and exhibit a wide compositional range of Cr-spinel (Cr# = Cr/(Cr + Al) atomic ratio, varying from 0.5 to 0.9). In contrast, discordant chromitites have higher PGE contents (commonly > 500 ppb), show a strong decoupling between the IPGE (Os, Ir, Ru) and PPGE (Rh, Pt, Pd) subgroups of the PGE distribution patterns, contain numerous PGM grains, and consist of high-Cr varieties (Cr# mostly > 0.6). In-situ analysis of clinopyroxene inclusions within Cr-spinel of discordant chromitites and associated dunite veins revealed characteristic U-shaped rare-earth elements (REE) patterns. This suggests the involvement of a hydrous SiO2-rich melt in the formation of PGE-rich chromitites and their associated discordant dunites. The wide range of Os-isotope composition of the Os-rich PGM, spanning from sub-chondritic to supra-chondritic 187Os/188Os values in the PGE-rich chromitites serves as further evidence for the heterogeneous hydrous melting process that led to the formation of these chromitites. These features, encompassing field and petrological characteristics, can be attributed to variations in the tectonic setting during the formation of podiform chromitites and can serve as valuable guidelines for PGE exploration.

Analysis, classification and remediation of defects in material extrusion 3D printing

Additive manufacturing technologies (or 3D printing) have emerged as powerful tools for creating a diverse array of objects, promising a paradigm shift in production methodologies across industries. In chemistry, it allows the manufacturing of reactors with complex topology. However, the benefits of these technologies can be diminished by the use of suboptimal parameters or inferior materials, leading to defects that significantly degrade the quality and functionality of the resulting products. The formulation of effective preventive strategies remains hampered by an incomplete understanding of defect formation. Given this, our review provides a comprehensive exploration of defects that arise during the Fused Filament Fabrication (FFF) — one of the most prevalent 3D printing methods. The defects are systematically classified according to several key characteristics, including size, type, mode of occurrence, and location. Each common defect is discussed in detail, describing its external manifestation, root causes, the impact on the properties of printed parts, and potential preventive measures. Our findings unveil the complex interplay between material properties, printing parameters, and cooling dynamics in the defect formation process. This classification has significant practical relevance, providing a solid basis for the development of strategies to minimize defects and improve the quality of 3D printed products. It provides valuable insights for a wide audience, including researchers investigating chemical processes and additive manufacturing technologies, 3D printing engineers, 3D printer operators, and quality assurance engineers involved in production quality control. In addition, our review points the way forward for future research in this area. There is a crucial need for the development of advanced machine learning and artificial intelligence models that can predict defect formation based on given printing parameters and material properties. Future investigations should also focus on the discovery of novel materials and refining of printing parameters to achieve superior quality of FFF 3D printed products. This is the first review on defect analysis, classification, and prevention methods in 3D printing. This review serves as a cornerstone for these future advances, promoting a deeper understanding of defect formation and prevention in additive manufacturing.&lt;br&gt; The bibliography includes 180 references .

Heavy minerals as indicators of source material in soils on carbonates

The origin of the soils formed on carbonate rocks remains uncertain, as they are probably of polygenetic origin. Of particular interest are the elevated contents of some trace elements detected in these soils, as they can hardly be attributed to insoluble residues of carbonate rock. The aim of this study was to uncover the relationship between heavy minerals in bedrock and soil and to identify other sources that influence the mineral and chemical composition of soil. We investigated representative samples of soils and dolomite bedrock as well as sandstones and marlstones from the nearby flysch basin as an expected source of the aeolian contribution. XRD and SEM/EDS showed that mineral diversity is higher in soils compared to the dolomites. Heavy minerals found in dolomite insoluble residue include sphalerite, Ti-oxide (probably rutile), zircon, fluorite, pyrite, minerals of REE phosphates and apatite group, interpreted as terrigenous detrital material. The mineral composition of soil heavy fraction is only partly following insoluble residues of bedrock and indicates possible aeolian contribution. Comparison with nearby flysch sandstones and marlstones showed similarities in mineralogical diversity by the presence of chromite and Fe-Cr(Mn) oxides (probably carmichaelite). Other minerals present in soils and flysch layers, such as Ti-oxide (probably rutile), zircon, REE phosphates, and pyrite grains, however, show similarities in mode of occurrence and transport indications. Signs of aeolian transport on the grains detected in soils were further confirmed by SEM/EDS.

Fate of fluorine in stratified samples from BGL gasifier at Hailar Chemical Plant, Inner Mongolia: An intermediate process perspective

This study investigated the fate of Fluorine (F) during the super high temperature (2000 °C) gasification process by analyzing 23 stratified samples inside the British Gas Lurgi (BGL) gasifier in production. Through sequential chemical extraction (SCEP), ion selective electrode (ISE), scanning electron microscope with energy dispersive spectrometer (SEM-EDS), high-resolution transmission electron microscope with energy dispersive spectrometer (HRTEM-EDS) and X-ray diffraction (XRD), this article complements the intermediate forms of transformation of F, in addition to the methods of deduction of the fate of F through input and output.Overall, the concentration of fluorine gradually decreases with increasing temperature and ≈1200 °C (14th layer) is the key temperature for its volatilisation. This may be related not only to the volatility of organic matter, but also to the significant contribution from the melting of a large amount of silicate and aluminosilicate minerals in the sample.In addition, the fluorine concentration remained stable from layer 14 to layer 27 (≈2000 °C), rather than continuing to evaporate, due to the formation of a new, stable mode of fluorine occurrence: Ca-P-F-Si minerals have been identified. The free and active SiO2, possibly derived from the melting of quartz and kaolinite, played a key role in preventing the melting of fluorapatite. The mechanism of formation of the new refractory materials (Ca-P-F-Si minerals) needs to be further validated by laboratory and computer simulations.

Advocating the Use of Bayesian Network in Analyzing the Modes of Occurrence of Elements in Coal.

Modes of occurrence of elements in coal are important because they can be used not only to understand the origin of inorganic components in coal but also to determine the impact on the environment and human health and the deposition process of coal seams as well. Statistical analysis is one of the commonly used indirect methods used to analyze the modes of occurrence of elements in coal, among which hierarchical clustering is widely used. However, hierarchical clustering may lead to misleading results due to its limitation that it focuses on the clusters of elements rather than a single element. To tackle this issue, we use the first part of a well-known Bayesian network structure learning algorithm, i.e., Peter-Clark (PC) algorithm, to explore the relationships of the coal elemental data and then infer modes of occurrence of elements in coal. A data set containing 95 Late Paleozoic coal samples from the Datanhao and Adaohai mines in Inner Mongolia, China, is used for the performance evaluation. Analytical results show that many instructive and surprising insights can be concluded from the first part of the PC algorithm. Compared with the hierarchical clustering algorithm, the first part of the PC algorithm demonstrates superiority in analyzing the modes of occurrence of elements in coal.

Effects of different types of inorganic potassium in biomass on volatile-char interactions for co-pyrolysis of coal and biomass

Co-gasification of biomass and coal has many advantages. However, the volatile-char interaction during co-pyrolysis, which is the first step of co-gasification, significantly changes the properties and the structure of biochar, thus affecting gasification. The present work investigated the effect of the interaction between the volatile from a coal and the biochar of K-salt-doped (K2CO3, K2SO4 and KCl) pine wood in a lab-scale, fixed-bed reactor at 600, 700 and 800 °C to understand how the occurrence mode of inorganic K in biomass alters the volatile-char interaction during co-pyrolysis. The volatile-char interaction has insignificant effects on the biochar of pine wood without the doping of K salts while it has significant effects on the biochar of K-salt-doped pine wood, especially for K2CO3 and K2SO4. The volatile-char interaction significantly increases the formation of C-O-K bonds, the content of oxygen containing compounds and the aromaticity of the biochar for K2CO3-doped and K2SO4-doped pine wood. In contrast, the evident presence of C-O-K bonds can only be found for KCl-doped pine wood at 800 °C after the volatile-char interaction. The increase in the pyrolysis temperature and the presence of the volatile-char interaction make the carbon structure of the biochar of K2SO4-doped and KCl-doped pine wood less ordered and generate more active sites. However, although the char order is lower and the number of active sites is higher for the biochar of K2CO3-doped pine wood than for that of K2SO4-doped and KCl-doped pine wood, the volatile-char interaction has insignificant effects on improving the activity of its biochar. Lastly, the volatile-char interaction causes insignificant additional release of K from the biochar. This may indicate that significant amounts of stable C-O-K bonds have been formed in the biochar to retain K.

Source of inorganic components in the Middle Jurassic inertinite-rich coals of the Southern Ordos Basin, China: With emphasis on formation of Sr- and Ba-bearing minerals

The Middle Jurassic coal seams located in the southern Ordos Basin display notably high concentrations of barium (Ba) and strontium (Sr). To acquire a comprehensive understanding of the source and occurrence of the elevated contents of Ba- and Sr-bearing minerals and their formation mechanism in the coal, a suite of petrological, mineralogical, and geochemical analyses was conducted on the Middle Jurassic coals of the Gaojiapu mine (No. 4 Coal) from the Binchang mining area, using optical microscopy, field emission-scanning electron microscopy, X-ray diffraction, X-ray fluorescence, and inductively coupled plasma mass spectrometry. The results indicate that the No. 4 Coal is a high volatile B bituminous coal, which is characterized by low ash, medium sulfur, and high inertinite contents. The modes of occurrence of minerals identified in the coal, including calcite, dolomite, pyrite, quartz, kaolinite, anatase, barite, and celestine, indicate that the No. 4 Coal may have been subjected to multiple stages of solutions injection. Barium and Sr in the investigated coals are significantly enriched, exhibiting maximum values of 19738 μg/g and 9932 μg/g, respectively, while concentrations of other trace elements are generally depleted. Barite and celestine, generally coexisting with carbonate minerals, commonly occur as cell- and fracture-fillings. Furthermore, the strong correlation coefficients (r) for Ba vs. Ca + Mg and Sr vs. Ca + Mg (0.78 and 0.61, respectively) indicate that most barite and celestine have a close association with carbonate minerals of epigenetic origin. The highly elevated concentrations of Ba and Sr are thought to be primarily derived from solutions leaching barite deposits developed in the Qinling Orogenic Belt, which is located in the south of the Ordos Basin. When mapped spatially, the distributions of Ba and Sr concentrations are fan-shaped, decreasing from the NW to the SE of the mining area. Meteoric water containing dissolved CO2 induced partial dissolution of carbonate rocks, and during this process, selected metal ions (e.g., Ca2+, Mg2+, Al3+, Si2+, Fe2+, Ba2+, and Sr2+) were redistributed and subsequently migrated along fracture zones to the coal seam. The fracture systems and abundant cavities within inertinite in the coal provided sufficient space and conduits for solutions migration.

A NEW VARIETY OF CHLADNIITE FROM VOLCANIC EXHALATIONS. GENETIC CRYSTAL CHEMISTRY OF CHLADNIITE

A new, unusual Fe-free and As5+-enriched variety of chladniite, a rare phosphate of the fillowite group was found in exhalations of the active Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. It belongs to the high-temperature (500–750°С) paragenesis with calciojohillerite, fluorapatite, metathénardite, diopside, enstatite, forsterite and hematite. This genetic type is novel for fillowite-group minerals. The crystal structure of Tolbachik chladniite is solved, R1 = 4.32%. It is trigonal, R–3, a = 14.9831(2), c = 42.8050(7) Å, V = 8322.1(3) Å3. The structural formula is: M13(Na0.56\(\square \)0.44)\(_{2}^{{M21}}\)(Na0.81Ca0.19)\(_{2}^{{M31}}\) (Na0.97\(\square \)0.03)\(_{6}^{{M12}}\)(Ca0.64Na0.36)\(_{6}^{{M1}}\)MnM2(Mg0.54Ca0.46)M3–9Mg\(_{{30}}^{{M10}}\)(Mg0.94Ca0.06)\(_{6}^{{M11}}\)Mg6(P33.53As2.47)O144 (Z = 3). The crystal chemical features of chladniite and their correlation with mode of occurrence are discussed for all chladniite findings known in meteorites and terrestrial objects of different genetic types.

Role of evaporites in sodium metasomatism and formation of albite-rich rocks in IOCG provinces

Hydrothermal Iron-oxide-Cu-Au (IOCG) deposits are important exploration targets for a number of metals of economic importance. Voluminous sodium metasomatism is ubiquitous in most IOCG provinces. The origin of the metasomatic fluid responsible for the formation of albite-rich rocks in such terranes is contentious; both evaporite-derived fluid and magmatic fluid have been advocated. The Singhbhum IOCG province in India is known for hosting several polymetallic deposits from which U, Cu, and apatite-magnetite are mined as principal commodities together with Ni, Au, Ag, Se, Te, Mo, and low-Ti magnetite as by-products. Voluminous albite-rich rocks occur at several sites along the mineralized belt. Metasomatic albite schist comprising predominantly albite and quartz at Pathargora contains tourmaline intricately associated with albite. Based on textures and mineralogical associations, tourmaline is classified as: tur1: coarse nodular tourmaline ± albite ± magnetite aggregate; tur2: disseminated fine-grained tourmaline in a schistose matrix; and tur3: tourmaline + biotite + magnetite + apatite clots. All tourmaline belongs to the alkali group and most to the dravite sub-group. Very low concentrations of Li (avg 3.8 ppm), Zn (avg 6 ppm) and Mn (avg 21 ppm) but high V (avg 2130 ppm) and Ni (avg 306.5 ppm) in tur1 core (tur1c) co-genetic with albite contrast with what is reported in magmatic/magmatic-hydrothermal tourmaline of granitic affinity. The δ11B values of tourmaline are mostly positive, ranging between –4.0 and 9.2 ‰ (avg 4.0 ± 3.0; n = 79); values of tur1 cores are 4.9–9.2 ‰. Previous fluid inclusion studies described the presence of halite and barite daughter crystals in primary fluid inclusions and demonstrated the involvement of a high-temperature (≥450 °C) and high-salinity (≥50 wt% NaCl equivalent) brine in the formation of cores of tur1. Calculated δ11B values of the hydrothermal fluid in equilibrium with tur1c range from 7.3 to 11.5 ‰ (for a crystallization temperature of 450 °C). Based on the textural setting of the tur1c-albite assemblage, geochemical and boron isotope composition of tur1c, and evidence of a high saline brine, we propose that the albite schist is the product of Na-metasomatism by brines that derived major constituents from the dissolution of marine evaporite. The inferred paleo-latitude and geological environment of sedimentation related to the host lithologies are consistent with the evaporitic model. We further suggest that a similar mechanism might have played an important role in the formation of albite-rich rocks in other IOCG provinces where the involvement of evaporite-derived fluids in mineralization/alteration have been demonstrated. Similar major element, trace element and positive boron isotope (1.5–6.3 ‰) composition of tur3 suggest similar source of fluid as that of tur1c, and tur3 formed either during the same alteration event or during a separate fluid pulse. On the other hand, the mode of occurrence, very low trace element concentration and weakly negative to positive δ11B (−4 to 2.3 ‰) value of tur2 suggest their metamorphic origin.

A new method for pre-enrichment of gallium and lithium based on mode of occurrence in coal gangue from Antaibao surface mine, Shanxi Province, China

The presence of a notable concentrations of gallium (Ga) and lithium (Li) in coal gangue, an industrial solid waste, has attracted widespread attention. However, utilization of these resources remains an economic challenge. This study entailed an investigation of the potential of the pre-enrichment of Ga and Li in coal gangue so as to effectively utilize coal gangue resources. The modes of occurrence of Ga and Li in coal gangue were studied using a sequential chemical extraction procedure (SCEP), mineral phase composition, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and elemental content composition. The results indicate that the main mineral components of the coal gangue are mica, quartz, pyrite, and clay. Ga and Li are mainly associated with Al-containing minerals, such as mica and clay. Further, the main noncarrier minerals are quartz and pyrite. Ga and Al exhibit a high degree of correlation, whereas Li exhibits a predominant association with Al and Ti. Ga and Li are also negatively correlated with Fe and Sr. Moreover, sorting experiments demonstrated that the separation of Ga and Li from pre-enriched coal gangue is an effective and environmentally friendly method. This allowed for the discarding of 31.25% of the waste rock, with an Fe content of 32.69%. The concentrate products can potentially be high-quality raw materials for Ga and Li refining facilities, whereas the tailing products can serve as an effective source of iron ore raw materials.

Catalytic Effect of Reactive Extraneous Mineral Composites on Char and Tar Distribution during Pyrolysis of Highveld Partially Oxidized Fine-Coal Reject and Its Beneficiated Residues.

In this study, the South African partially oxidized fine-coal reject (FCR), which is associated with human health and environmental problems and sustains high disposal expenses, was subjected to density-separation, chemical fractionation, and demineralization experiments to isolate and evaluate the mode of occurrence of mineral-matter (MM) effects on the FCR pyrolysis. A unique composite of two reactive oxides (i.e., MgO and Fe2O3) and a hydrated oxide [i.e., Ca(OH)2] representing major extraneous coal-minerals were blended with either FCR, demineralized FCR, and its beneficiated samples to evaluate the yields of pyrolytic products and activation energy following a novel procedure. The properties of FCR samples and their pyrolytic products were determined by different analyses. Results indicate that the reactive oxides and a hydrated oxide composite addition increased the average activation energy (332.0-476.5 kJ/mol) for FCR due to the initial Ca(OH)2 decomposition and Fe2O3 reduction that took place under pyrolysis conditions. The FCR mineral-rich sink fractions achieved the highest carbon conversion (char yield = 78.8% and tar yield = 5.1%) compared to those of other samples (e.g., <1.9 g/cm3 float char yield = 87.3% and tar yield = 2.3%) evaluated due to higher proportions of calcite/dolomite/pyrite cleats and nonmineral inorganics (Ca, Mg, Na, and Fe) which catalyzed the pyrolysis reactions. On the other hand, CaCO3, CaMg(CO3)2, and metakaolinite formations in the char derived from a blend of reactive oxides and a hydrated oxide composite and FCR interfere with the pyrolysis reactions. Also, deoxygenation reactions were impeded by oxygen present in the reactive oxides and a hydrated oxide composite. The potent catalytic effects of cleat minerals and the extraneous minerals associated with cracking of heavy tars to lighter fractions open opportunities to further understand the mode of occurrence of MM present in FCR during utilization in global pyrolysis. This may reduce waste disposal costs, health-hazards, air-pollution, and FCR volumes and augments feed-coals.

Mineralogical and geochemical compositions of the early permian coal in the Huixiang Mine, Dengfeng Coalfield, Henan, China: Occurrence modes and origins of NH4-illite

In this study, we investigated the mineralogy and geochemistry of the Pennsylvanian No. 21 coal seam at the Huixiang Mine in the Dengfeng Coalfield, North China by employing a range of analytical techniques, including electron probe micro-analysis, X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, and X-ray powder diffraction. The No. 21 coal in Huixiang Mine is classified as semi-anthracite and is characterized by a low total sulfur and ash contents. The predominant minerals identified in the Huixiang coal are NH4-illite, kaolinite, calcite, and chlorite, alongside trace amounts of Al-hydroxide minerals, zircon, and pyrite. Coalification in the Huixiang Mine has been primarily influenced by the heat generated by gravity-gliding tectonic movements since the Yanshan period, and the presence of hydrothermal fluids. During the coalification process, organic nitrogen undergoes thermal ammoniation, releasing NH4+ ions that subsequently react with kaolinite, leading to the formation of NH4-illite. Concurrently, when kaolinite is converted into NH4-illite, the released Si and excess Al may provided the necessary material for the formation of Al-hydroxide minerals and chamosite. The coal in the Huixiang Mine is slightly enriched with Li, Zr, Nb, Ta, and Th, rendering it a promising candidate for potential industrial recovery. The strong correlation of these elements with ash content suggested that their presence was largely influenced by terrestrial material input, attributable to the source materials originating in the North Qinling Orogenic Belt.

Rare Earth Element Characteristics in Coal Ash from the Jungar Energy Gangue Power Plant, Inner Mongolia, China

The coal and coal-bearing measures in the Jungar Coalfield in Inner Mongolia are characterized by rare earth element (REE) enrichment. Combustion in coal-fired power plants can lead to further enrichment of REEs in coal ash, which serves as a new potential source for REE extraction and smelting. Further, investigating the content, modes of occurrence, and transformation behavior of REEs during coal combustion may help in better understanding REE differentiation during coal combustion and facilitate the development of economically feasible REE recovery technologies. Therefore, in this study, we analyzed coal ash from the Jungar Energy Gangue Power Plant in Inner Mongolia via inductively coupled plasma mass spectrometry, X-ray diffraction, and scanning electron microscopy combined with energy-dispersive spectroscopy. Our results showed that the REE content of the feed coal was 220 μg/g, slightly higher than the average for global coal. Additionally, fly ash had a higher REE content (898 μg/g) than bottom ash, and its rare earth oxide content was approximately 1152 μg/g, which meets the industrial requirements. Bottom and fly ashes contained similar minerals; however, their relative abundances were different. Specifically, mullite, quartz, calcite, and gypsum were slightly more abundant in fly ash than in bottom ash, whereas amorphous solids were slightly more abundant in bottom ash than in fly ash. Furthermore, fly ash, dominated by Si- and Al-rich minerals, was composed of irregular particles of different shapes and sizes. It also contained monazite and REE fluoro-oxides, which possibly originated from the feed coal and had mineral structures that remained unchanged during coal combustion. Thus, the REE fluoro-oxides possibly resulted from the conversion of bastnaesite in the feed coal during combustion and thereafter became attached to the edge of the Si–Al minerals in the fly ash.

Agglomeration and transformation of different types of inorganic potassium in biomass during co-gasification with coal

Co-gasification of biomass and coal has many advantages, which also mitigates some of the ash-related problems induced by potassium (K) in biomass. However, this effect varies with the occurrence mode of inorganic K in biomass, which varies with the species of biomass. Therefore, the present work investigated the effect of a bituminous coal on the transformation of K and the ash chemistry of bed agglomeration (without considering the effect of fluidization) during co-gasification (steam and CO2 atmospheres) for different types of inorganic K (K2CO3, K2SO4 and KCl) in biomass. The results show that for both K2CO3 and K2SO4 in biomass, K is mainly retained as KAlSiO4 and K2SO4 in the gasification ash with KAlSiO4 being the dominant phase. In addition, for K2CO3 in biomass, more KAlSiO4 and less K2SO4 are formed under the steam atmosphere than under the CO2 atmosphere. However, the K retention of the ash or the agglomerate for both K2CO3 and K2SO4 in biomass is similar and is much higher than that for KCl in biomass, which tends to release and to induce other ash-related problems. In addition, both the organic compounds of coal and the gasification atmosphere significantly alter the reaction between coal with KCl in biomass: The majority of KCl reacts with coal to form KAlSiO4, the formation of which is quite limited for the coal ash; More K is retained in the ash and more KAlSiO4 is formed under the steam atmosphere than under the CO2 atmosphere. Lastly, although co-gasification with coal (silica sand as the bed material) cannot stop the formation of agglomerates for K2CO3, K2SO4 and KCl in biomass, these agglomerates are more easily to be broken than those produced from the gasification of biomass alone, thus mitigating bed agglomeration in fluidized-bed reactors.

Selective sequential extraction and microanalysis for revealing distribution, occurrence mode, and removal potential of arsenic in phosphate ore

Arsenic (As) is a common impurity extensively existing in phosphate ore and it has to be removed using complicated operations during the phosphorus chemical process. To investigate the occurrence mode of As would be beneficial to evaluate the separation of As from phosphate ore in the flotation process. In the current study, selective sequential extraction (SSE) and microanalysis were employed to reveal the distribution and occurrence modes of As in a phosphate ore sample. The SSE results indicated that As in the phosphate ore was dispersed in fractions of carbonate minerals (18.27 %), oxides/hydroxides (ca. 38 %), and sulfide minerals (22.07 %). In addition, 3.05 % of As could be extracted in the exchangeable and soluble fraction. Microanalysis of scanning electron microscope (SEM), transmission electron microscope (TEM), and electron probe micro-analyzer (EPMA) revealed the main arsenic-containing minerals by means of energy dispersive spectrometer (EDS) or wavelength dispersive spectrometer (WDS). Results showed that all of iron oxides/hydroxides phases, all of rhodochrosite particles, and parts of pyrite were arsenic-containing, with the average contents of As measured to be 0.142, 0.052, and 0.047 %, respectively. Consequently, arsenic amounts in the phosphate ore descended in the order of iron oxides/hydroxides > pyrite > rhodochrosite. These arsenic-containing minerals/phases could be removed through different beneficiation methods, such as flotation and chemical minerals processing. The findings of this study provide a mineralogical insight into developing potential techniques to remove As from phosphate ores.

Organic petrography and palynofacies of the Upper Cretaceous (Campanian-Maastrichtian) organic rich strata of the Quseir-Safaga Region, Eastern Egypt

The Campanian-Maastrichtian organic-rich rocks in the Quseir – Safaga Region in the Eastern Desert of Egypt have growing economic importance. This economic importance is discussed in many of previous studies by many of different geological tools that lacked the petrographic examination of organic matter occurrence modes. The organic petrography provides the essential tools for microscopic analysis to study the organic matter that are applied for the first time in the present study. The palynofacies and organic petrography are used in the present study to investigate the nature of the organic matter and the paleoenvironmental settings that controlled their distribution in the Duwi and Dakhla formations in the Younis and Mohamed Rabah areas (Egypt). The study of dinoflagellate cysts allowed the identification of the biostratigraphically characteristic assemblages of the Campanian – Maastrichtian in the Eastern Desert including Assemblage II/I (in Duwi Formation) and Assemblage III (in Dakhla Formation) that were identified in Egyptian oil shales of this time range. The identified assemblages are correlated with local and regional studies to delineating the formal biozonation. The organic matter in the Duwi Formation comprises rich fluorescent amorphous organic matter, prasinophytes, sporomorphs, dinocysts as well as a minor terrigenous component of phytoclasts. In the Dakhla Formation, the fluorescent AOM is found to be highly mixed with Botryococcus in addition to prasinophytes and marine palynomorphs. The paleoenvironmental analysis indicates deposition in distal anoxic to proximal suboxic marine conditions with high paleoproductivity. The results are confirmed with the inorganic geochemical composition of redox sensitive elements. The analysis reveals that the Younis section is differentiated into two palynofacies types (proximal, suboxic high productivity in the Duwi Formation and distal anoxic in the Dakhla Formation). The Mohamed Rabah section, one palynofacies type is recognized that is proximal, suboxic high productivity. The principal component analysis is used to interpret the distribution of organic matter abundances. The kerogen types are distinguished based on the area percentages of the fluorescent organic matter and application of kerogen plots. The samples of both formations fall within oil prone kerogen type II. The spore coloration and measured vitrinite reflectance indicate immature kerogen in the studied sections. The organic matter in the studied rocks comprises hydrogen rich compounds that can be treated for direct composition or retorted to extract shale oil. The heavy metals concentrations are significant and present technology will increase its economic value.

The occurrence pattern of natural hydrogen in the Songliao Basin, P.R. China: Insights on natural hydrogen exploration

The exploration of natural hydrogen offers a promising path towards achieving energy transition and environmental protection. To gain knowledge on the occurrence of natural hydrogen in the Songliao Basin, rock samples from the hydrogen-rich intervals in the Denglouku Formation and Yingcheng Formation of Well SK-2 in the Songliao Basin were analyzed using XRD, SEM, nitrogen adsorption, and high-pressure hydrogen adsorption measurements (under 25 °C, 0–18 MPa). The results revealed that hydrogen adsorption mainly depended on pore structure. Hydrogen predominantly existed in adsorbed form in mesoporous and microporous pores. The amount of adsorbed hydrogen in rocks decreases with elevated temperature and increases with pressure. Hydrogen migration to the formations primarily occurred through faults, and sandstone mainly contained free hydrogen. Understanding the occurrence and accumulation mode of natural hydrogen in Well SK-2 contributes to the development of exploration methods and utilization of this valuable resource.

Origin of chamosite and berthierine: Implications for volcanic-ash-derived Nb-Zr-REY-Ga mineralization in the Lopingian sequences from eastern Yunnan, SW China

Clay minerals are generally used as pivotal indicators to reveal diagenetic parameters such as temperature and pH in hydrothermal ore-forming systems. Within the Late Permian Nb-Zr-REY-Ga-mineralized horizons in eastern Yunnan, the elevated enrichment of critical metals has been considered to be closely associated with abundant clay minerals. In this paper, the identification, abundance, morphology, modes of occurrence, and chemical compositions of two phyllosilicate minerals, namely chamosite (chlorite group) and berthierine (serpentine-kaolinite group) were analyzed by XRD (X-ray diffraction) and SEM-EDS (scanning electron microscopy equipped with an energy dispersive X-ray spectrometer). The results show that chamosite mainly occurs as massive and book-like aggregates, while berthierine occurs in various forms, including coarse granular, spherulitic, sheaf-like, sharp-angular, and vermicular aggregates. The modes of occurrence and scatter plots of Mg/(Mg + Fe) vs. Al/(Al + Fe + Mg) of chamosite indicate a Fe-Mg-rich siliceous hydrothermal origin. In the Al/Si-Mg/Fe diagram, analysis points for berthierine are distributed in the partially overlapping fields of hydrothermal ore, laterite/bauxite, and marine, indicating that the formation of berthierine was influenced by various geological factors. Based upon its chemistry and modes of occurrence, berthierine mainly originated by direct precipitation from Fe-Mg-rich siliceous hydrothermal fluids, but in some cases, it was derived from the replacement of precursor minerals and the in-situ alteration of volcanic fragments. A scenario of the transformation mechanism of clay minerals in the Nb-Zr-REY-Ga-rich horizons is proposed. Airborne volcanic glasses and primary minerals were initial altered in-situ into vermicular kaolinite and angular berthierine in the early diagenetic stage. Subsequently, some vermicular kaolinite and the oolitic berthierine crystallized from solutions underwent gradual illitization, and some pre-existing minerals (e.g., albite, kaolinite, and illite) were altered into berthierine, while a proportion of chamosite transformed from berthierine through an interstratified berthierine/chamosite (B/C) in the middle to late diagenetic stages. Throughout all stages of diagenesis, the chamosite, berthierine, and their intermediate phases precipitated directly from Fe-Mg-rich siliceous hydrothermal fluids. Moreover, the diagenetic temperature revealed by chamosite is from ∼200 to ∼302℃, indicating that the Nb-Zr-REY-Ga mineralization and chamosite formation occurred under low-temperature thermal alteration conditions.