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Minerals, Volume 8, Issue 3 (March 2018)

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Cover Story (view full-size image) We evaluated the capability of two commercial HSZs, ZSM-5 (MFI topology), and Y zeolite (FAU [...] Read more.
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Open AccessArticle Estimating RMR Values for Underground Excavations in a Rock Mass
Minerals 2018, 8(3), 78; doi:10.3390/min8030078
Received: 30 January 2018 / Revised: 13 February 2018 / Accepted: 21 February 2018 / Published: 25 February 2018
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Abstract
During underground excavations for civil or mining engineering purposes, the variations in rock mass quality are important, especially for the design of the most suitable support to be applied to ensure stability. The aim of this investigation is to model the expected behavior
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During underground excavations for civil or mining engineering purposes, the variations in rock mass quality are important, especially for the design of the most suitable support to be applied to ensure stability. The aim of this investigation is to model the expected behavior of the ground, and thus to predict the scenarios indicating potential variations in the quality of the rock mass during underground excavation. When considering the rock mass rating (RMR) values observed at the excavation face in six study cases, which together total more than 27 km in length of underground excavation by drilling and blasting (D&B), and based on the observed RMR values at the face, the most probable value (1–100) is estimate for the RMR index at the five subsequent front advances. It is concluded that, up to about 20 m ahead of the current face, the quality of the rock mass for the next advances is close to the quality observed at the present face, and that, with increasing distance, there is a greater deviation of RMR values with respect to the quality observed at the current face. Full article
(This article belongs to the Special Issue Geological Modelling)
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Open AccessArticle Process Design Aspects for Scandium-Selective Leaching of Bauxite Residue with Sulfuric Acid
Minerals 2018, 8(3), 79; doi:10.3390/min8030079
Received: 11 January 2018 / Revised: 13 February 2018 / Accepted: 21 February 2018 / Published: 25 February 2018
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Abstract
Aiming at the industrial scale development of a Scandium (Sc)-selective leaching process of Bauxite Residue (BR), a set of process design aspects has been investigated. The interpretation of experimental data for Sc leaching yield, with sulfuric acid as the leaching solvent, has shown
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Aiming at the industrial scale development of a Scandium (Sc)-selective leaching process of Bauxite Residue (BR), a set of process design aspects has been investigated. The interpretation of experimental data for Sc leaching yield, with sulfuric acid as the leaching solvent, has shown significant impact from acid feed concentration, mixing time, liquid to solids ratio (L/S), and number of cycles of leachate re-usage onto fresh BR. The thin film diffusion model, as the fundamental theory for leaching, either with constant particle size for selective leaching, or with shrinking particle size for less- or non-selective leaching, interprets the relevant experimental data. In both cases, a concept for an unyielding core supplements the basic model. Especially for the selective leaching mild conditions, the simplest model version agrees with the experiments, since both prove 1st order kinetics, while for extreme conditions, a combined conversion rate model with diffusion and chemical reaction inside particles is proposed. The maximization of Sc recovery per unit of consumed solvent emerged as highly critical for the process economics. Full article
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Open AccessArticle Insights into Adsorption of Chlorobenzene in High Silica MFI and FAU Zeolites Gained from Chromatographic and Diffractometric Techniques
Minerals 2018, 8(3), 80; doi:10.3390/min8030080
Received: 9 January 2018 / Revised: 7 February 2018 / Accepted: 19 February 2018 / Published: 26 February 2018
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Abstract
In this work, the capability of two commercial high silica zeolites (HSZs), namely ZSM-5 and Y, for the removal of chlorobenzene (CB) from water was investigated by combining chromatographic and diffractometric techniques. The adsorption isotherms and kinetics of CB on ZSM-5 and Y
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In this work, the capability of two commercial high silica zeolites (HSZs), namely ZSM-5 and Y, for the removal of chlorobenzene (CB) from water was investigated by combining chromatographic and diffractometric techniques. The adsorption isotherms and kinetics of CB on ZSM-5 and Y zeolites were determined from batch tests. The adsorption kinetics were very fast; the time to reach equilibrium was less than 10 min. The equilibrium data of CB on the two HSZs showed dissimilarities that are particularly evident in the adsorption data concerning the low concentration range, where Y zeolite is characterized by low adsorption. On the contrary, at higher solution concentrations the adsorption capacity of Y is higher than that of ZSM-5. The crystalline structures of Y and ZSM-5 saturated with CB were investigated by X-ray diffraction (XRD) techniques. Rietveld refinement analyses of XRD data allowed for quantitative probing of the structural modifications of both zeolites after CB adsorption and provided insight into the preferred zeolite adsorption sites in both microporous materials. The refined framework–extraframework bond distances confirm that interactions between the selected organic contaminant and hydrophobic zeolites are mediated via co-adsorbed H2O. The occurrence of H2O–CB–framework oxygen oligomers explains variations in both the unit cell parameters and the shape of the channels, clearly confirming that water plays a very relevant role in controlling the diffusion and adsorption processes in hydrophobic zeolites. Full article
(This article belongs to the Special Issue Natural Zeolites)
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Open AccessArticle Size-Controlled Production of Gold Bionanoparticles Using the Extremely Acidophilic Fe(III)-Reducing Bacterium, Acidocella aromatica
Minerals 2018, 8(3), 81; doi:10.3390/min8030081
Received: 24 January 2018 / Revised: 14 February 2018 / Accepted: 22 February 2018 / Published: 26 February 2018
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Abstract
Recycling of gold-bearing “urban mine” resources, such as waste printed circuit boards (PCBs), is attracting an increasing interest. Some of the gold leaching techniques utilize acidic lixiviants and in order to eventually target such acidic leachates, the utility of the acidophilic Fe(III)-reducing heterotrophic
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Recycling of gold-bearing “urban mine” resources, such as waste printed circuit boards (PCBs), is attracting an increasing interest. Some of the gold leaching techniques utilize acidic lixiviants and in order to eventually target such acidic leachates, the utility of the acidophilic Fe(III)-reducing heterotrophic bacterium, Acidocella (Ac.) aromatica PFBC was evaluated for production of Au(0) bionanoparticles (bio-AuNPs). Au(III) ions (as AuCl4, initially 10 mg/L), were readily adsorbed onto the slightly-positively charged Ac. aromatica cell surface and transported into cytoplasm to successfully form intracellular bio-AuNPs in a simple one-step microbiological reaction. Generally, increasing the initial concentration of formate as e-donor corresponded to faster Au(III) bioreduction and a greater number of Au(0) nucleation sites with less crystal growth within 40–60 h: i.e., use of 1, 5, 10, or 20 mM formate led to production of bio-AuNPs of 48, 24, 13, or 12 nm in mean particle size with 2.3, 17, 62, and 97 particles/cell, respectively. Addition of Cu2+ as an enzymatic inhibitor significantly decreased the number of Au(0) nucleation sites but enhanced crystal growth of individual particles. As a result, the manipulation of the e-donor concentration combined with an enzyme inhibitor enabled the 3-grade size-control of bio-AuNPs (nearly within a normal distribution) at 48, 26 or 13 nm by use of 1 mM formate, 20 mM formate (+Cu2+) or 10 mM formate, respectively, from highly acidic, dilute Au(III) solutions. Full article
(This article belongs to the Special Issue Geomicrobiology and Biogeochemistry of Precious Metals)
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Open AccessArticle Peat-Forming Environments and Evolution of Thick Coal Seam in Shengli Coalfield, China: Evidence from Geochemistry, Coal Petrology, and Palynology
Minerals 2018, 8(3), 82; doi:10.3390/min8030082
Received: 3 November 2017 / Revised: 13 February 2018 / Accepted: 23 February 2018 / Published: 26 February 2018
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Abstract
Due to the importance of the wide occurrence of thick coal seams for Chinese coal resources, the origins of these seams have received considerable attention. Using the Early Cretaceous No. 5 coal seam with a thickness of 16.8 m in Inner Mongolia as
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Due to the importance of the wide occurrence of thick coal seams for Chinese coal resources, the origins of these seams have received considerable attention. Using the Early Cretaceous No. 5 coal seam with a thickness of 16.8 m in Inner Mongolia as a case study, this paper presents a systematic investigation of the coal petrology, geochemistry, and palynology of 19 coal samples to explain the origin and evolution of peat accumulation. The results indicate that the No. 5 coal seam is generally characterized by low rank (lignite), dominant huminite (average = 82.3%), intermediate ash yield (average = 16.03%), and sulfur content (average = 1.12%). The proportion of spores generally increases from the bottom to the top of the coal seam, whereas the proportion of pollen decreases. The vegetation in the coal seam is dominated by gymnosperms at the bottom and by ferns at the top. The paleographic precursor peat was most likely accumulated in the lakeshore where herbaceous and bushy helophytes were dominant. The total sulfur content was positively related to the huminite content. The sulfur content was possibly derived from bacterial action with sulfur brought in via marine incursions. Three overall declining-increasing values of carbon isotopes within the No. 5 coal seam possibly indicated three general cooling trends during peat accumulation. The environment of peat accumulation included three cycles, including one drying-wetting-drying in the bottom part and two drying-upwards cycles in the upper part. These cycles of the peat-accumulation environment could likely be ascribed to climate change because of their good agreement with humidity signals from plant types at that stage. Full article
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Open AccessArticle Geochemistry of Toxic Elements and Their Removal via the Preparation of High-Uranium Coal in Southwestern China
Minerals 2018, 8(3), 83; doi:10.3390/min8030083
Received: 9 January 2018 / Revised: 7 February 2018 / Accepted: 22 February 2018 / Published: 27 February 2018
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Abstract
High-uranium (U) coal is the dominant form of coal in Southwestern China. However, directly utilizing this resource can also harm the environment because this element is radioactive; it is, therefore, necessary to clean this kind of coal before burning. This research studied the
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High-uranium (U) coal is the dominant form of coal in Southwestern China. However, directly utilizing this resource can also harm the environment because this element is radioactive; it is, therefore, necessary to clean this kind of coal before burning. This research studied the geochemistry of toxic elements and their partitioning during the preparation of high-U coal in China. The results show that high-U coals are mainly distributed in Southwestern China and are characterized by a high organic sulfur (S) content and vanadium (V)-chromium (Cr)-molybdenum (Mo)-U element assemblage. These elements are well-correlated with one another, but are all negatively related to ash yield, indicating that all four are syngenetic in origin and associated with organic materials. A mineralogical analysis shows that U in Ganhe and Rongyang coal occurs within fine-grained anatase, clay minerals, guadarramite, and pyrite, while V occurs in clay minerals, pyrite, and dolomite, and Cr occurs in dolomite. Other elements, such as fluorine (F), lead (Pb), selenium (Se), and mercury (Hg), mainly occur in pyrite. By applying a gravity separation method to separate minerals from coal, the content of the enrichment element assemblage of V-Cr-Mo-U in Rongyang coal is still shown to be higher than, or close to, that of the original feed because this element assemblage is derived from hydrothermal fluids during syngenetic or early diagenetic phases, but other elements (beryllium [Be], F, manganese [Mn], zinc [Zn], Pb, arsenic [As], Se, Hg) can be efficiently removed. Once cleaned, the coal obtained by gravity separation was subject to a flotation test to separate minerals; these results indicate that while a portion of V and Cr can be removed, Mo and U remain difficult to extract. It is evident that the two most commonly utilized industrialized coal preparation methods, gravity separation and flotation, cannot effectively remove U from coal where this element occurs in large proportions. Finally, dilute hydrochloric acid (HCl) leaching experiments show that the majority of Mo and a portion of V, Cr, and U are adsorbed in clay minerals and organic matter and, therefore, exist in an adsorbed state. In this state, these elements can be removed using the acid method. Thus, as U cannot be fully removed from coal, the use of high-U coals is not recommended. Full article
(This article belongs to the Special Issue Toxic Mineral Matter in Coal and Coal Combustion Products)
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Open AccessArticle Indications that Amorphous Calcium Carbonates Occur in Pathological Mineralisation—A Urinary Stone from a Guinea Pig
Minerals 2018, 8(3), 84; doi:10.3390/min8030084
Received: 29 January 2018 / Revised: 22 February 2018 / Accepted: 24 February 2018 / Published: 27 February 2018
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Abstract
Calcium carbonate is an abundant biomineral that is of great importance in industrial or geological contexts. In recent years, many studies of the precipitation of CaCO3 have shown that amorphous precursors and intermediates are widespread in the biomineralization processes and can also
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Calcium carbonate is an abundant biomineral that is of great importance in industrial or geological contexts. In recent years, many studies of the precipitation of CaCO3 have shown that amorphous precursors and intermediates are widespread in the biomineralization processes and can also be exploited in bio-inspired materials chemistry. In this work, the thorough investigation of a urinary stone of a guinea pig suggests that amorphous calcium carbonate (ACC) can play a role in pathological mineralization. Importantly, certain analytical techniques that are often applied in the corresponding analyses are sensitive only to crystalline CaCO3 and can misleadingly exclude the relevance of calcium carbonate during the formation of urinary stones. Our analyses suggest that ACC is the major constituent of the particular stone studied, which possibly precipitated on struvite nuclei. Minor amounts of urea, other stable inorganics, and minor organic inclusions are observed as well. Full article
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Open AccessArticle Depressing Iron Mineral by Metallic-Starch Complex (MSC) in Reverse Flotation and Its Mechanism
Minerals 2018, 8(3), 85; doi:10.3390/min8030085
Received: 31 January 2018 / Revised: 20 February 2018 / Accepted: 22 February 2018 / Published: 27 February 2018
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Abstract
A series of metallic-starch complex (MSC) solutions, synthesized by mixing relevant metallic ionic solutions with the caustic starch solution, were used as the flotation depressants to investigate their depressing effects on hematite ore. The MSC is a nano-sized colloidal complex which is configured
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A series of metallic-starch complex (MSC) solutions, synthesized by mixing relevant metallic ionic solutions with the caustic starch solution, were used as the flotation depressants to investigate their depressing effects on hematite ore. The MSC is a nano-sized colloidal complex which is configured by hydrophilic metallic hydroxide as the colloidal nucleus on which starch and hydroxyl complex are adsorbed, resulting in a larger molecule than starch itself. The flotation tests showed that the depressing abilities of various MSC (Fe3+, Zn2+, Pb2+ and Mg2+) on the iron minerals were higher than the caustic starch, and the order of depression ability was: Zn2+-starch > Pb2+-starch > Fe3+-starch > Mg2+-starch > caustic starch. Based on the adsorption analysis, the high depressing ability of the MSC arose from increasing the adsorption density of starch on iron minerals and slightly reducing the absorption of the collector dodecylamine. Adsorption behaviour also indicated that the adsorption of the MSC on mineral surfaces was thicker than the caustic starch, and among various MSC the adsorption of Fe3+-starch exhibited the thickest adsorption layer while that of Mg2+-starch the thinnest. Zeta potential indicated that with a weaker electronegativity than the caustic starch, MSC adsorbed onto iron minerals more easily, and the strong electrostatic adsorption with the aid of the hydrogen bonding and chemisorption agreed well with the high depressing ability of the MSC. Full article
(This article belongs to the Special Issue Flotation Chemistry)
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Open AccessArticle Selective Attachment of Leptospirillum ferrooxidans for Separation of Chalcopyrite and Pyrite through Bio-Flotation
Minerals 2018, 8(3), 86; doi:10.3390/min8030086
Received: 31 January 2018 / Accepted: 1 February 2018 / Published: 27 February 2018
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Abstract
The replacement of depressants used in sulfide mineral beneficiation, with bacteria and their metabolites, promises to reduce the environmental impact left by the mining industry. In this study, the attachment of Leptospirillum ferrooxidans, L.f, to chalcopyrite and pyrite was investigated through
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The replacement of depressants used in sulfide mineral beneficiation, with bacteria and their metabolites, promises to reduce the environmental impact left by the mining industry. In this study, the attachment of Leptospirillum ferrooxidans, L.f, to chalcopyrite and pyrite was investigated through Scanning Electron Microscopy (SEM). The impact of selective attachment, bacterial growth conditions, and extracellular polymeric substances (EPS) was investigated through bio-flotation. L.f exhibits selective attachment to pyrite between 0 h and 168 h exposure via an indirect contact mechanism. Separation of chalcopyrite from pyrite was achieved through exposing the minerals for 72 h with an L.f culture grown on either HH media, chalcopyrite, or pyrite. The results produced 80.4, 43.4, and 47.4% recovery of chalcopyrite, respectively. However, EPS supernatant extracted from L.f grown on chalcopyrite, conditioned for 48 h, provided the best separation efficiency by the selective depression of pyrite resulting in 95.8% Cu recovery. Polysaccharide-rich EPS selectively attaches to pyrite within 48 h, depressing its floatability and ensuring successful separation with a PIPX collector. Full article
(This article belongs to the Special Issue Flotation Chemistry)
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Open AccessArticle Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology
Minerals 2018, 8(3), 87; doi:10.3390/min8030087
Received: 29 September 2017 / Revised: 21 February 2018 / Accepted: 23 February 2018 / Published: 27 February 2018
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Abstract
The Chadormalu magnetite-apatite deposit in Bafq metallogenic province, Central Iran, is hosted in the late Precambrian-lower Cambrian volcano-sedimentary rocks with sodic, calcic, and potassic alterations characteristic of iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) ore systems. Apatite occurs as scattered irregular veinlets
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The Chadormalu magnetite-apatite deposit in Bafq metallogenic province, Central Iran, is hosted in the late Precambrian-lower Cambrian volcano-sedimentary rocks with sodic, calcic, and potassic alterations characteristic of iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) ore systems. Apatite occurs as scattered irregular veinlets and disseminated grains, respectively, within and in the marginal parts of the main ore-body, as well as apatite-magnetite veins in altered wall rocks. Textural evidence (SEM-BSE images) of these apatites shows primary bright, and secondary dark areas with inclusions of monazite/xenotime. The primary, monazite-free fluorapatite contains higher concentrations of Na, Si, S, and light rare earth elements (LREE). The apatite was altered by hydrothermal events that led to leaching of Na, Si, and REE + Y, and development of the dark apatite. The bright apatite yielded two U-Pb age populations, an older dominant age of 490 ± 21 Ma, similar to other iron deposits in the Bafq district and associated intrusions, and a younger age of 246 ± 17 Ma. The dark apatite yielded a U-Pb age of 437 ± 12 Ma. Our data suggest that hydrothermal magmatic fluids contributed to formation of the primary fluorapatite, and sodic and calcic alterations. The primary apatite reequilibrated with basinal brines in at least two regional extensions and basin developments in Silurian and Triassic in Central Iran. Full article
(This article belongs to the Special Issue Fundamentals and Frontiers in Mineralogy)
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Open AccessArticle Structural Characterization of the Body Frame and Spicules of a Glass Sponge
Minerals 2018, 8(3), 88; doi:10.3390/min8030088
Received: 6 February 2018 / Revised: 20 February 2018 / Accepted: 24 February 2018 / Published: 27 February 2018
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Abstract
The nanostructure (atomic-scale structure) and water species in the body frame and spicules of the marine glass sponge, Euplectella aspergillum, collected from the sea floor around Cebu Island was characterized in detail by thermogravimetric differential thermal analysis, nuclear magnetic resonance spectroscopy, Raman
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The nanostructure (atomic-scale structure) and water species in the body frame and spicules of the marine glass sponge, Euplectella aspergillum, collected from the sea floor around Cebu Island was characterized in detail by thermogravimetric differential thermal analysis, nuclear magnetic resonance spectroscopy, Raman and infrared spectroscopies, and X-ray diffraction method. The structural features of the nanostructure in the body frame and spicules were essentially similar to each other, although these were different from those of inorganic amorphous silica materials, such as silica gel and silica glass. In addition, the averaged short and medium range structures of the sponge may be similar to those of tridymite. The water content and water species included in the body frame and spicules were almost the same. More than half of the contained water was physisorbed water molecules, and the rest was attributed to Q3 and Q2 silanol groups. Most of the water species may be present at the surface and involved in hydrogen bonding. Full article
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Open AccessArticle Mapping of Trace Elements in Coal and Ash Research Based on a Bibliometric Analysis Method Spanning 1971–2017
Minerals 2018, 8(3), 89; doi:10.3390/min8030089
Received: 8 December 2017 / Revised: 22 February 2018 / Accepted: 23 February 2018 / Published: 28 February 2018
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Abstract
Coal is the most important fossil energy used in China. The environmental impact of trace elements released in coal combustion has become one of the hottest issues in recent years. Based on a software named CiteSpace, and social network analysis (SNA), a bibliometric
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Coal is the most important fossil energy used in China. The environmental impact of trace elements released in coal combustion has become one of the hottest issues in recent years. Based on a software named CiteSpace, and social network analysis (SNA), a bibliometric analysis of research into trace elements in coal and ash field during 1971–2017 is presented with the information of authors, countries, institutions, journals, hot issues and research trends in the present study. The study results indicate that: (1) Shifeng Dai, Robert B Finkelman, Guijian Liu and James C Hower have a large number of publications with great influence. (2) China (29.8%) and USA (22.2%) have high productivity in total publications. China and the USA correlate closely in the cooperative web system. (3) China University of Mining and Technology and Chinese Academy of Sciences take the leading position in the quantity of publications among all research institutions. (4) Energy and fuels, engineering and environmental science are three disciplines with the most studies in this field. (5) International Journal of Coal Geology, Fuel, Energy and Fuels and Fuel Processing Technology are the top four journals with the most publications in this field. (6) The enrichment origin and modes of occurrence of trace elements are the mainstream research related to trace elements in coal and ash. The environmental problems caused by coal combustion have promoted the development of trace elements in coal research, and human health is getting more and more popular in recent years. The study findings provide a better understanding of features of trace elements in coal and ash research, which could be taken as a reference for future studies in this field. Full article
(This article belongs to the Special Issue Toxic Mineral Matter in Coal and Coal Combustion Products)
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Open AccessArticle Sequential Transformation Behavior of Iron-Bearing Minerals during Underground Coal Gasification
Minerals 2018, 8(3), 90; doi:10.3390/min8030090
Received: 31 December 2017 / Revised: 11 February 2018 / Accepted: 12 February 2018 / Published: 28 February 2018
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Abstract
Detailed mineralogical information from underground coal gasification (UCG) is essential to better understand the chemical reactions far below the surface. It is of great scientific significance to study the mineral transformation and identify the typical minerals in certain process conditions, because it may
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Detailed mineralogical information from underground coal gasification (UCG) is essential to better understand the chemical reactions far below the surface. It is of great scientific significance to study the mineral transformation and identify the typical minerals in certain process conditions, because it may help to ensure the stable operation of gasification processes and improve the utilization efficiency of coal seams. The transformation of iron-bearing minerals has the typical characteristics during the UCG process and is expected to indicate the process parameters. In this paper, UCG progress was subdivided into pyrolysis, reduction and oxidation stages, and the progressive coal conversion products were prepared. Two types of lignite with different iron contents, Ulankarma and Ulanqab coals, were used in this study. The minerals in the coal transformation products were identified by X-ray diffraction (XRD) and a scanning electron microscope coupled with an energy-dispersive spectrometer (SEM-EDS). The thermodynamic calculation performed using the phase diagram of FactSage 7.1 was used to help to understand the transformation of minerals. The results indicate that the transformation behavior of iron-bearing minerals in the two lignites are similar during the pyrolysis process, in which pyrite (FeS2) in the raw coal is gradually converted into pyrrhotite (Fe1−xS). In the reduction stage, pyrrhotite is transformed into magnetite (Fe3O4) and then changes to FeO. The reaction of FeO and Al2O3 in the low iron coal produces hercynite above 1000 °C because of the difference in the contents of Si and Al, while in the high iron coal, FeO reacts with SiO2 to generate augite (Fe2Si2O6). When the temperature increases to 1400 °C, both hercynite and augite are converted to the thermodynamically-stable sekaninaite. Full article
(This article belongs to the Special Issue Toxic Mineral Matter in Coal and Coal Combustion Products)
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Open AccessArticle Density Functional Theory Study of Arsenate Adsorption onto Alumina Surfaces
Minerals 2018, 8(3), 91; doi:10.3390/min8030091
Received: 1 February 2018 / Revised: 23 February 2018 / Accepted: 23 February 2018 / Published: 1 March 2018
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Abstract
Atomistic modeling of mineral–water interfaces offers a way of confirming (or refuting) experimental information about structure and reactivity. Molecular-level understanding, such as orbital-based descriptions of bonding, can be developed from charge density and electronic structure analysis. First-principles calculations can be used to identify
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Atomistic modeling of mineral–water interfaces offers a way of confirming (or refuting) experimental information about structure and reactivity. Molecular-level understanding, such as orbital-based descriptions of bonding, can be developed from charge density and electronic structure analysis. First-principles calculations can be used to identify weaknesses in empirical models. This provides direction on how to propose more robust representations of systems of increasing size that accurately represent the underlying physical factors governing reactivity. In this study, inner-sphere complex geometries of arsenate on hydrated alumina surfaces are modeled at the density functional theory (DFT)–continuum solvent level. According to experimental studies, arsenate binds to alumina surfaces in a bidentate binuclear (BB) fashion. While the DFT calculations support the preference of the BB configuration, the optimized geometries show distortion from the ideal tetrahedral geometry of the arsenic atom. This finding suggests that steric factors, and not just coordination arguments, influences reactivity. The Osurf–As–Osurf angle for the more favorable arsenate configurations is closest to the ideal tetrahedral angle of 109.5°. Comparing the results of arsenate adsorption using a small cluster model with a periodic slab model, we report that the two model geometries yield results that differ qualitatively and quantitatively. This relates the steric factors and rigidity of the surface models. Full article
(This article belongs to the Special Issue Molecular Simulation of Mineral-Solution Interfaces)
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Open AccessArticle A Fluid Inclusion Study of the Brookbank Deposit, Northwestern Ontario: A Transition from Mesothermal to Epithermal Gold Deposition
Minerals 2018, 8(3), 92; doi:10.3390/min8030092
Received: 9 October 2017 / Revised: 16 February 2018 / Accepted: 21 February 2018 / Published: 1 March 2018
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Abstract
The Brookbank and Cherbourg Zone gold deposits are located in the Beardmore–Geraldton greenstone belt of the Wabigoon Subprovince of the Archean Superior Province of the Canadian Shield. Brookbank is a shear zone deposit, whereas the Cherbourg Zone, joined by a shear zone to
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The Brookbank and Cherbourg Zone gold deposits are located in the Beardmore–Geraldton greenstone belt of the Wabigoon Subprovince of the Archean Superior Province of the Canadian Shield. Brookbank is a shear zone deposit, whereas the Cherbourg Zone, joined by a shear zone to the Brookbank, is a fissure vein deposit, presumably formed by the same ore-depositing fluid. A total of 375 fluid inclusions, all with low salinity (generally <1 °C freezing point depression) and presence of CO2, from the two deposits were studied. Cross-cutting relationships delineated three stages of vein formation: (1) pre-ore, (2) ore stage and (3) post-ore. Stage 1 inclusions homogenized at ca. 230 °C with low salinity, although at Brookbank a high temperature episode at ca. 360 °C was noted. Stage 2 homogenized at ca. 266 °C at the Cherbourg Zone and over a range 258–269 °C with somewhat higher salinity. Eutectic temperatures indicate that the fluid composition was within the MgCl2-NaCl-H2O system. Fluid immiscibility was prominent in that inclusions homogenized to liquid and vapor at the same temperature were observed. The majority of inclusions from Brookbank homogenized to vapor, whereas those from the Cherbourg Zone homogenized to liquid, marking the transition from mesothermal to epithermal lode gold deposition. Stage 3 fluid inclusions from the Cherbourg Zone homogenized at slightly elevated temperatures and contained fluid possibly representing metastable hydrates of KCl. These post-ore fluids may have been the source of potassium feldspar alteration that overprinted earlier alteration assemblages. Full article
(This article belongs to the Special Issue Geochemistry and Mineralogy of Hydrothermal Metallic Mineral Deposits)
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Open AccessArticle Platy Galena from the Viburnum Trend, Southeast Missouri: Character, Mine Distribution, Paragenetic Position, Trace Element Content, Nature of Twinning, and Conditions of Formation
Minerals 2018, 8(3), 93; doi:10.3390/min8030093
Received: 15 December 2017 / Revised: 11 February 2018 / Accepted: 23 February 2018 / Published: 2 March 2018
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Abstract
The Viburnum Trend of southeast Missouri is one of the world’s largest producers of lead. The lead occurs as galena, predominantly in two crystallographic forms, octahedrons and cubes. Many studies have shown that octahedral galena is paragentically early, the more abundant of the
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The Viburnum Trend of southeast Missouri is one of the world’s largest producers of lead. The lead occurs as galena, predominantly in two crystallographic forms, octahedrons and cubes. Many studies have shown that octahedral galena is paragentically early, the more abundant of the two crystal forms, and is commonly modified in the cube. Those studies also have shown that the cubic form is paragenetically later, less abundant than the octahedrons, and may exhibit minor octahedral modifications. Viburnum Trend galena crystals that exhibit a platy form have received almost no study. The reason for their lack of study is the rarity of their occurrence. This communication discusses their character, mine distribution, paragenetic position, trace element contents, nature of twinning, and speculated conditions of formation. It also compares their character to similar platy galena occurrences in Germany, Bulgaria, Russia, Mexico, and notes their occurrence at the Pine Point District in the Northwest Territories of Canada and at the Black Cloud mine in Colorado. Flat, platy galena crystals have been recognized to occur in very small amounts in the Magmont, Buick, Fletcher, Brushy Creek, and Sweetwater mines in the Viburnum Trend. In contrast, platy galena has never been observed to occur at the Casteel, West Fork, #27, #28, and #29 mines in the Trend. The platy crystals have formed early in the paragenetic sequence of the ores, prior to and coated by subsequently deposited druzy quartz and cubic galena. Spinel twinning of the octahedron produces flat platy crystals. The platy galena crystals of the Viburnum Trend are very similar in crystal morphology to platy galena crystals interpreted to be spinel twins in the Gonderbach Ag mine in NW Germany, the Dalnegorsk Pb-Zn (skarn deposit) mine in SE Russia, the Madan ore field of skarn Pb-Zn-Ag deposits of southern Bulgaria, and the large Naica skarn Pb mine of northern Mexico. The crystallization of certain crystal forms of galena has been ascribed to the incorporation of elevated contents of trace elements in some lead districts. Analysis of Viburnum platy galena crystals shows that they contain very low levels of trace elements: 3.1 ppm Ag, <2 ppm Bi, <2 ppm Sb, and <2 ppm As. Thus, elevated trace element content is not the cause for the development of Viburnum platy galena. It is speculated that the Viburnum spinel-twinned galena crystals were the result of rapid crystallization from oversaturated hydrothermal ore fluids. Full article
(This article belongs to the Special Issue Fundamentals and Frontiers in Mineralogy)
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Open AccessArticle A Preliminary Investigation into Separating Performance and Magnetic Field Characteristic Analysis Based on a Novel Matrix
Minerals 2018, 8(3), 94; doi:10.3390/min8030094
Received: 1 January 2018 / Revised: 31 January 2018 / Accepted: 26 February 2018 / Published: 2 March 2018
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Abstract
The matrix is the agglomeration carrier of magnetic mineral particles in high-gradient magnetic separation (HGMS). Its structural parameters have a great influence on the distribution of the magnetic field in the separation space, and therefore affect the separation effect. This paper introduces a
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The matrix is the agglomeration carrier of magnetic mineral particles in high-gradient magnetic separation (HGMS). Its structural parameters have a great influence on the distribution of the magnetic field in the separation space, and therefore affect the separation effect. This paper introduces a novel matrix called a screw thread rod matrix, which has the dual advantages of the rod matrix and the grooved magnetic plate, i.e., the advantages of better slurry fluidity through the matrix and higher magnetic field gradient at the sharp corners. This research on the novel matrix was performed from the following three aspects: the description of components of the matrix, the effect of structural parameters of the matrix on separation performance of fine hematite ore tailings in Northeast China, and the numerical analysis of the magnetic induction properties of different kinds of magnetic matrices based on three-dimensional structural characteristics. Compared with the smooth rod matrix, the proposed screw thread rod matrix enhances the inhomogeneity of the axial magnetic induction intensity on the surface of the matrix. Accordingly, the recovery of fine-grained iron minerals is improved through the resulting combined effect of the radial curvature of the rod and the inhomogeneous magnetic field in the axial direction. Furthermore, the best moderate distance between equidistant ring-shaped bulges (ERB) as well as the best column gap between adjacent rod elements were determined, respectively. Full article
(This article belongs to the Special Issue Sustainable Mineral Processing Technologies)
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Open AccessArticle Fossilization History of Fossil Resin from Jambi Province (Sumatra, Indonesia) Based on Physico-Chemical Studies
Minerals 2018, 8(3), 95; doi:10.3390/min8030095
Received: 27 December 2017 / Revised: 23 February 2018 / Accepted: 27 February 2018 / Published: 2 March 2018
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Abstract
A unique specimen of fossil resin originating from the Dipterocarpaceae tree family found in Miocene brown coal deposits in Jambi Province (Sumatra, Indonesia) was investigated via microscopic observations, microhardness testing and infrared and Raman spectroscopic methods. Its form is rare in nature, being
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A unique specimen of fossil resin originating from the Dipterocarpaceae tree family found in Miocene brown coal deposits in Jambi Province (Sumatra, Indonesia) was investigated via microscopic observations, microhardness testing and infrared and Raman spectroscopic methods. Its form is rare in nature, being an aggregate of three varieties of resin differing in colour, transparency and internal structure. This suggests the formation of the resins at different stages. Further alteration processes, including fossilization and maturation of the resin in a swamp environment resulted in stepwise aromatization of the cyclohexane ring in steroids and cross-linking through formation of ester bonds as well as carbon–carbon bonds between steroid molecules. The various environmental and geological conditions affecting the formation processes of the resins were recorded in their physico-chemical properties. Additionally, heating conditions accelerated by volcanism were proposed as a factor determining the maturation grade of the resin. Full article
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Open AccessArticle Micropore Structure of Cement-Stabilized Gold Mine Tailings
Minerals 2018, 8(3), 96; doi:10.3390/min8030096
Received: 28 December 2017 / Revised: 14 February 2018 / Accepted: 22 February 2018 / Published: 2 March 2018
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Abstract
Mine tailings have often to be stabilized by mixing them with cementing agents. In this study, the pore structure of gold tailings stabilized with Portland cement was evaluated by means of mercury intrusion porosimetry. The investigation was conducted on samples prepared with different
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Mine tailings have often to be stabilized by mixing them with cementing agents. In this study, the pore structure of gold tailings stabilized with Portland cement was evaluated by means of mercury intrusion porosimetry. The investigation was conducted on samples prepared with different fractions of tailings and cement as well as on samples activated with elevated temperature curing and chemical (CaCl2) addition. It was observed that all mixed samples exhibit a mono-modal pore size distribution, indicating that the cement-stabilized tailings are characterized by a single-porosity structure. The results also showed that the higher fraction of tailings and cement leads to a dense and finer pore structure. The total porosity of mixture samples decreases with increasing curing temperature and CaCl2 concentration due to the acceleration of hydration reaction. Full article
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Open AccessArticle The Role of ε-Fe2O3 Nano-Mineral and Domains in Enhancing Magnetic Coercivity: Implications for the Natural Remanent Magnetization
Minerals 2018, 8(3), 97; doi:10.3390/min8030097
Received: 27 January 2018 / Revised: 16 February 2018 / Accepted: 26 February 2018 / Published: 2 March 2018
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Abstract
A natural ε-Fe2O3 nano-mineral (luogufengite) has been discovered in young basaltic rocks around the world. Transmission electron microscopy (TEM) observed euhedral or subhedral luogufengite nano-minerals with crystal sizes ranging from 10 to 120 nm in the basaltic rocks. The magnetic
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A natural ε-Fe2O3 nano-mineral (luogufengite) has been discovered in young basaltic rocks around the world. Transmission electron microscopy (TEM) observed euhedral or subhedral luogufengite nano-minerals with crystal sizes ranging from 10 to 120 nm in the basaltic rocks. The magnetic property of treated scoria sample (containing 75.3(5) wt % luogufengite) showed a saturation remanence of 11.3 emu g−1 with a coercive field of 0.17 tesla (T) at room temperature. Luogufengite-like nano-domains were also observed in natural permanent magnets (lodestone) and Fe-Ti oxides (ilmenite-magnetite series) with strong remanent magnetization. The structure of luogufengite-like domains (double hexagonal close-packing) is associated with the interfaces between the (111) plane of cubic magnetite and the (0001) plane of rhombohedral hematite or ilmenite. Stacking faults and twin boundaries of magnetite/maghemite can also produce the luogufengite-like domains. The nano-domains oriented along the magnetic easy axis play an essential role in enhancing the magnetic coercivity of lodestone and Fe-Ti oxide. We conclude that the luogufengite nano-minerals and nano-domains provide an explanation for coercivity and strong remanent magnetization in igneous, metamorphic rocks and even some reported Martian rocks. These nano-scaled multilayer structures extend our knowledge of magnetism and help us to understand the diverse magnetic anomalies occurring on Earth and other planetary bodies. Full article
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Open AccessArticle Biosynthesis of Schwertmannite and Goethite in a Bioreactor with Acidophilic Fe(II)-Oxidizing Betaproteobacterium Strain GJ-E10
Minerals 2018, 8(3), 98; doi:10.3390/min8030098
Received: 12 February 2018 / Revised: 28 February 2018 / Accepted: 1 March 2018 / Published: 4 March 2018
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Abstract
Iron oxide minerals, schwertmannite and goethite, which are naturally occurring in acidic environments are attractive nanostructured materials because of the potential diverse applications. Although the biosynthesis of schwertmannite by acidophilic Fe(II)-oxidizing microorganisms has been investigated, little is known about goethite biosynthesis under acidic
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Iron oxide minerals, schwertmannite and goethite, which are naturally occurring in acidic environments are attractive nanostructured materials because of the potential diverse applications. Although the biosynthesis of schwertmannite by acidophilic Fe(II)-oxidizing microorganisms has been investigated, little is known about goethite biosynthesis under acidic conditions. To examine a biological approach to the synthesis of these minerals, bioreactor experiments were conducted with a newly isolated acidophilic betaproteobacterium. The bioproducts were characterized by powder X-ray diffraction, cryogenic Mössbauer spectroscopy, and electron microscopy. The cultures growing at 25 °C and pH 3.0 or at 37 °C and pH 2.5 oxidized Fe(II) and precipitated schwertmannite rapidly. Increasing pH at each temperature resulted in the concomitant production of goethite, and 90% pure goethite was obtained at 37 °C and pH 3.5. The goethite phase was nano-sized and had relatively large specific surface area (133 m2·g−1), leading to high sorption capacity for metal oxyanions. Schwertmannite was also a good adsorbent for oxyanions, regardless of the smaller specific surface area. Our results indicate that these acidophilic microbial cultures serve as a simple rapid system for the synthesis of nanostructured goethite as well as schwertmannite. Full article
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Open AccessArticle Interaction of Freshwater Diatom with Gold Nanoparticles: Adsorption, Assimilation, and Stabilization by Cell Exometabolites
Minerals 2018, 8(3), 99; doi:10.3390/min8030099
Received: 22 January 2018 / Revised: 27 February 2018 / Accepted: 1 March 2018 / Published: 5 March 2018
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Abstract
The rising concern about the potential toxicity of synthetic gold nanoparticles (AuNPs) in aquatic environments requires a rigorous estimation of physico-chemical parameters of reactions between AuNPs and major freshwater microorganisms. This study addresses the interaction of 10-nm size, positively charged AuNPs
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The rising concern about the potential toxicity of synthetic gold nanoparticles (AuNPs) in aquatic environments requires a rigorous estimation of physico-chemical parameters of reactions between AuNPs and major freshwater microorganisms. This study addresses the interaction of 10-nm size, positively charged AuNPs with periphytic freshwater diatoms (Eolimna minima). The adsorption experiments on viable cells were performed in 10 mM NaCl and 5 mM NaCl + 5 mM NaHCO3 solution at a variable pH (3–10), at an AuNPs concentration from 1 µg/L to 10,000 µg/L, and an exposure time from a few minutes to 55 days. Three types of experiments, adsorption as a function of time (kinetics), pH-dependent adsorption edge, and constant-pH “Langmuirian” type isotherms, were conducted. In addition, long-term interactions (days to weeks) of live diatoms (under light and in the darkness) were performed. The adsorption was maximal at a pH from 3 to 6 and sizably decreased at a pH of 6 to 10. Results of adsorption experiments were modeled using a second order kinetic model, a Linear Programming Model, Freundlich isotherm, and a ligand binding equation for one site competition. The adsorption of AuNPs(+) most likely occurred on negatively-charged surface sites of diatom cell walls such as carboxylates or phosphorylates, similar to previously studied metal cations. Under light exposure, the AuNPs were stabilized in aqueous solution in the presence of live cells, probably due to the production of exometabolites by diatoms. The adsorbed amount of AuNPs decreased after several days of reaction, suggesting some AuNPs desorption. In the darkness, the adsorption and assimilation were stronger than under light. Overall, the behavior of positively charged AuNPs at the diatom–aqueous solution interface is similar to that of metal cations, but the affinity of aqueous AuNPs to cell exometabolites is higher, which leads to the stabilization of nanoparticles in solution in the presence of diatoms and their exudates. During photosynthetic activity and the pH rising above 9 in the vicinity of diatom cells, the adsorption of AuNPs strongly decreases, which indicates a decreasing potential toxicity of AuNPs for photosynthesizing cells. The present study demonstrates the efficiency of a thermodynamic and kinetic approach for understanding gold nanoparticles interaction with aquatic freshwater peryphytic microorganisms. Full article
(This article belongs to the Special Issue Geomicrobiology and Biogeochemistry of Precious Metals)
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Open AccessArticle Reflectance Spectral Features and Significant Minerals in Kaishantun Ophiolite Suite, Jilin Province, NE China
Minerals 2018, 8(3), 100; doi:10.3390/min8030100
Received: 28 January 2018 / Revised: 27 February 2018 / Accepted: 28 February 2018 / Published: 5 March 2018
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Abstract
This study used spectrometry to determine the spectral absorption of five types of mafic-ultramafic rocks from the Kaishantun ophiolite suite in Northeast China. Absorption peak wavelengths were determined for peridotite, diabase, basalt, pyroxenite, and gabbro. Glaucophane, actinolite, zoisite, and epidote absorption peaks were
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This study used spectrometry to determine the spectral absorption of five types of mafic-ultramafic rocks from the Kaishantun ophiolite suite in Northeast China. Absorption peak wavelengths were determined for peridotite, diabase, basalt, pyroxenite, and gabbro. Glaucophane, actinolite, zoisite, and epidote absorption peaks were also measured, and these were used to distinguish such minerals from other associated minerals in ophiolite suite samples. Combined with their chemical compositions, the blueschist facies (glaucophane + epidote + chlorite) and greenschist facies (actinolite + epidote + chlorite) mineral assemblage was distinct based on its spectral signature. Based on the regional tectonic setting, the Kaishantun ophiolite suite probably experienced the blueschist facies metamorphic peak during subduction and greenschist facies retrograde metamorphism during later slab rollback. Full article
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Open AccessArticle Dissolved Silica Effects on Adsorption and Co-Precipitation of Sb(III) and Sb(V) with Ferrihydrite
Minerals 2018, 8(3), 101; doi:10.3390/min8030101
Received: 9 January 2018 / Revised: 28 February 2018 / Accepted: 2 March 2018 / Published: 5 March 2018
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Abstract
Elevated antimony concentrations in aqueous environments from anthropogenic sources are becoming of global concern. In this respect iron oxides are known to strongly adsorb aqueous antimony species with different oxidation states, but the effect of silica on the removal characteristics is not well
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Elevated antimony concentrations in aqueous environments from anthropogenic sources are becoming of global concern. In this respect iron oxides are known to strongly adsorb aqueous antimony species with different oxidation states, but the effect of silica on the removal characteristics is not well understood despite being a common component in the environment. In this study, ferrihydrite was synthesized at various Si/Fe molar ratios to investigate its adsorption and co-precipitation behaviors with aqueous antimony anionic species, Sb(III) and Sb(V). The X-ray diffraction analyses of the precipitates showed two broad diffraction features at approximately 35° and 62° 2θ, which are characteristics of 2-line ferrihydrite, but no significant shifts in peak positions in the ferrihydrite regardless of the Si/Fe ratios. The infrared spectra showed a sharp band at ~930 cm−1, corresponding to asymmetric stretching vibrations of Si–O–Fe bonds which increased in intensity with increasing Si/Fe molar ratios. Further, the surface charge on the precipitates became more negative with increasing Si/Fe molar ratios. The adsorption experiments indicated that Sb(V) was preferentially adsorbed under acidic conditions which decreased dramatically with increasing pH while the adsorption rate of Sb(III) ions was independent of pH. However, the presence of silica suppressed the adsorption of both Sb(III) and Sb(V) ions. The results showed that Sb(III) and Sb(V) ions were significantly inhibited by co-precipitation with ferrihydrite even in the presence of silica by isomorphous substitution in the ferrihydrite crystal structure. Full article
(This article belongs to the Special Issue Environmental Mineralogy)
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Open AccessArticle Large-Scale Consumption and Zero-Waste Recycling Method of Red Mud in Steel Making Process
Minerals 2018, 8(3), 102; doi:10.3390/min8030102
Received: 14 February 2018 / Revised: 27 February 2018 / Accepted: 1 March 2018 / Published: 6 March 2018
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Abstract
To release the environmental pressure from the massive discharge of bauxite residue (red mud), a novel recycling method of red mud in steel making process was investigated through high-temperature experiments and thermodynamic analysis. The results showed that after the reduction roasting of the
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To release the environmental pressure from the massive discharge of bauxite residue (red mud), a novel recycling method of red mud in steel making process was investigated through high-temperature experiments and thermodynamic analysis. The results showed that after the reduction roasting of the carbon-bearing red mud pellets at 1100–1200 °C for 12–20 min, the metallic pellets were obtained with the metallization ratio of ≥88%. Then, the separation of slag and iron achieved from the metallic pellets at 1550 °C, after composition adjustment targeting the primary crystal region of the 12CaO·7Al2O3 phase. After iron removal and composition adjustment, the smelting-separation slag had good smelting performance and desulfurization capability, which meets the demand of sulfurization flux in steel making process. The pig iron quality meets the requirements of the high-quality raw material for steel making. In virtue of the huge scale and output of steel industry, the large-scale consumption and zero-waste recycling method of red mud was proposed, which comprised of the carbon-bearing red mud pellets roasting in the rotary hearth furnace and smelting separation in the electric arc furnace after composition adjustment. Full article
(This article belongs to the Special Issue Towards Sustainability in Extractive Metallurgy)
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Open AccessArticle Froth Image Acquisition and Enhancement on Optical Correction and Retinex Compensation
Minerals 2018, 8(3), 103; doi:10.3390/min8030103
Received: 17 December 2017 / Revised: 22 February 2018 / Accepted: 2 March 2018 / Published: 6 March 2018
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Abstract
To well monitor and optimize the flotation production, a computer vision and image analysis system is used. In such a system, the first important step is to acquire the froth surface images in high quality. Froth imaging quality is hard to control, and
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To well monitor and optimize the flotation production, a computer vision and image analysis system is used. In such a system, the first important step is to acquire the froth surface images in high quality. Froth imaging quality is hard to control, and the industrial field noise, froth 3D properties, complex textures, and mixed colors can also cause the flotation image to be difficult to segment and process. To acquire high quality images, a new system for image acquisition of the lead flotation is studied. The system constructs the free-form surface lens based on the non-imaging optics theory, which can improve the optical efficiency of the lens and the uniformity of light sources, and can reduce flare effects. For the compensation, an improved MSR (Multi-Scale Retinex) adaptive image algorithm is proposed to increase the brightness and intensity contrast for small bubbles, and to enhance texture details and froth weak edges by analyzing the Retinex output characteristics of the shaded area and improving the gain function. Under the condition of the optimal parameters, the image acquisition system can obtain uniform illumination and reduce different noises. Experiments show that the new froth image acquisition system increases Signal/Noise by 14%, contrast by 21%, and image segmentation accuracy by 26% in an image. Full article
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Open AccessArticle Mineralogical and Geochemical Compositions of the Lopingian Coals in the Zhongliangshan Coalfield, Southwestern China
Minerals 2018, 8(3), 104; doi:10.3390/min8030104
Received: 10 January 2018 / Revised: 25 February 2018 / Accepted: 27 February 2018 / Published: 6 March 2018
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Abstract
The mineralogical and geochemical compositions of the Lopingian coals from an exploratory drill core (ZK4-1) in the Zhongliangshan Coalfield, southwestern China are reported in this paper. The Zhongliangshan coals are medium volatile bituminous in rank (random vitrinite reflectance, average 1.38%), characterized by a
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The mineralogical and geochemical compositions of the Lopingian coals from an exploratory drill core (ZK4-1) in the Zhongliangshan Coalfield, southwestern China are reported in this paper. The Zhongliangshan coals are medium volatile bituminous in rank (random vitrinite reflectance, average 1.38%), characterized by a medium-ash yield (26.84%) and high sulfur content (3.38%). Minerals in the Zhongliangshan coals are mainly composed of clay assemblages (kaolinite, the illite/smectite mixed layer (I/S) and chamosite), pyrite, quartz, carbonate minerals (calcite, marcasite, ankerite, and dolomite), and anatase, followed by rutile, jarosite, natrojarosite, bassanite, gypsum and K-feldspar, with traces of apatite, rhabdophane and barite. Compared with the average concentrations of the world hard coals, some trace elements including Li, V, Co, Cu, Se, Y, Zr, Nb, rare earth elements (REE), Cd, Ta, Hf and Hg, are enriched in the Zhongliangshan coals. The modes of occurrence of chamosite, barite, rhabdophane, quartz and calcite in the Zhongliangshan coals indicate that the coals have probably been affected by the injection of low-temperature hydrothermal fluids. Based on the concentrations of Sc, V, Cr, Co, Ni, Cu and Zn, the ratios of Al2O3/TiO2 and the upper continental crust-normalized rare earth element and yttrium (REY) distribution patterns of the Zhongliangshan coals, the dominant sediment source regions are the Leshan–Longnvsi Uplift, Hannan Upland, and Dabashan Uplift, with a small proportion of terrigenous materials from the Kangdian Upland. The K7 and the upper portion of K1 coals have the potential as raw materials for the recovery of REY. Full article
(This article belongs to the Special Issue Toxic Mineral Matter in Coal and Coal Combustion Products)
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Open AccessArticle C14–22 n-Alkanes in Soil from the Freetown Layered Intrusion, Sierra Leone: Products of Pt Catalytic Breakdown of Natural Longer Chain n-Alkanes?
Minerals 2018, 8(3), 105; doi:10.3390/min8030105
Received: 26 January 2018 / Revised: 26 February 2018 / Accepted: 27 February 2018 / Published: 6 March 2018
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Abstract
Soil above a platinum-group element (PGE)-bearing horizon within the Freetown Layered Intrusion, Sierra Leone, contains anomalous concentrations of n-alkanes (CnH2n+2) in the range C14 to C22 not readily attributable to an algal or lacustrine origin. Longer chain
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Soil above a platinum-group element (PGE)-bearing horizon within the Freetown Layered Intrusion, Sierra Leone, contains anomalous concentrations of n-alkanes (CnH2n+2) in the range C14 to C22 not readily attributable to an algal or lacustrine origin. Longer chain n-alkanes (C23 to C31) in the soil were derived from the breakdown of leaf litter beneath the closed canopy humid tropical forest. Spontaneous breakdown of the longer chain n-alkanes to form C14–22 n-alkanes without biogenic or abiogenic catalysts is unlikely as the n-alkanes are stable. In the Freetown soil, the catalytic properties of the PGE (Pt in particular) may lower the temperature at which oxidation of the longer chain n-alkanes can occur. Reaction between these n-alkanes and Pt species, such as Pt2+(H2O)2(OH)2 and Pt4+(H2O)2(OH)4 can bend and twist the alkanes, and significantly lower the Heat of Formation. Microbial catalysis is a possibility. Since a direct organic geochemical source of the lighter n-alkanes has not yet been identified, this paper explores the theoretical potential for abiogenic Pt species catalysis as a mechanism of breakdown of the longer n-alkanes to form C14–22 alkanes. This novel mechanism could offer additional evidence for the presence of the PGE in solution, as predicted by soil geochemistry. Full article
(This article belongs to the Special Issue Geomicrobiology and Biogeochemistry of Precious Metals)
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Open AccessArticle Fossilized Bacteria in Fe-Mn-Mineralization: Evidence from the Legrena Valley, W. Lavrion Mine (Greece)
Minerals 2018, 8(3), 107; doi:10.3390/min8030107
Received: 17 December 2017 / Revised: 2 March 2018 / Accepted: 6 March 2018 / Published: 8 March 2018
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Abstract
The primary mineralization in the famous Lavrion mine in the Lavreotiki area, Attica (Greece), associated with a granodiorite intrusion of Upper Miocene age and composed of massive sulphide Pb-Zn-Ag ores [sphalerite, pyrite and galena (B.P.G)], has been extensively studied. The present study is
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The primary mineralization in the famous Lavrion mine in the Lavreotiki area, Attica (Greece), associated with a granodiorite intrusion of Upper Miocene age and composed of massive sulphide Pb-Zn-Ag ores [sphalerite, pyrite and galena (B.P.G)], has been extensively studied. The present study is focused on thin, hard, dark brown to black Fe-Mn crusts (a few mm to cm in thickness) in the Legrena valley, SW Lavreotiki, aiming to provide new insights on that type of Fe-Mn-mineralization. The scanning electron microscope (SEM)/energy dispersive spectroscopy (EDS) data presented revealed the presence of fine rounded fragments, resembling nodules (up to 200 μm) and fossilized bacteriomorphic Fe-Mn-oxides/hydroxides, within brecciated and foliated zones of carbonate rocks. They exhibit unusual features when compared to the common massive Fe-Mn mineralization with regards the following: (a) the extensive occurrence of bacteriomorphic Fe-oxides/hydroxides and their micro-textures; and (b) the minor elements (K, Na, P, S, Ca, As and Cl). The occurrence of abundant bacteriomophic Fe-Mn-oxides/hydroxides in the samples from the Legrena valley may reflect their catalytic role in the redox reactions during ore-forming processes. The characteristic features of that type of Fe-Mn mineralization seems to be the result of multistage supergene processes superimposed over initial hydrothermal stages. Such a multistage remobilization and precipitation of metals along open space surfaces on karstified carbonates during a subsequent stage of their initial precipitation may be widespread in the Attica region, Greece. Full article
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Open AccessArticle Mineralogy and Physico-Chemical Data of Two Newly Discovered Halloysite in China and Their Contrasts with Some Typical Minerals
Minerals 2018, 8(3), 108; doi:10.3390/min8030108
Received: 22 January 2018 / Revised: 17 February 2018 / Accepted: 24 February 2018 / Published: 8 March 2018
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Abstract
We report in this article the systematical acquisition of physico-chemical parameters for two newly discovered halloysite (Hal) minerals from Shiyan and Tongling in China. As the comparative reference, the data from Hal in Linfen, Chenxi, and the salt lake in Australia (samples were
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We report in this article the systematical acquisition of physico-chemical parameters for two newly discovered halloysite (Hal) minerals from Shiyan and Tongling in China. As the comparative reference, the data from Hal in Linfen, Chenxi, and the salt lake in Australia (samples were abbreviated as Hal-AU, Hal-SY, Hal-LF, Hal-CX and Hal-TL, respectively) were also investigated using X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared spectroscopy (FTIR), differential scanning calorimetry-thermogravimetry (DSC-TG), X-ray fluorescence, surface zeta potential measurements and N2 adsorption-desorption isotherms. The newly found minerals were probably formed in hydrothermal leaching and sedimentary circumstances. The Hal-SY contains 7 Å-halloysite and dickite, while Hal-TL contains 10 Å-halloysite with some alunite (similar with Hal-CX). Other impurities found in the samples include quartz, gibbsite, iron oxide and anatase. All of them showed tubular morphology with diameter in the range of 30–90 nm and a length of 300–2500 nm, while the Hal-SY has the largest inner diameter to about 150 nm. Specific surface areas varied from 26.0~59.0 m2·g−1. In addition, maximum CEC (cation exchange capacity) of the newly found Hal was about 40 cmol/kg, while that of Hal-AU was relatively low (8 cmol/kg) due to the sedimentary nature of Salt Lake circumstances. The surface charge was predominantly negative over most of the relevant pH range (>2.0). It can be concluded that the different morphology and impurity content of halloysite will greatly affect the surface area, pore volume, and cationic exchange capacity (CEC) of the minerals. Full article
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Open AccessArticle New Mineral with Modular Structure Derived from Hatrurite from the Pyrometamorphic Rocks of the Hatrurim Complex: Ariegilatite, BaCa12(SiO4)4(PO4)2F2O, from Negev Desert, Israel
Minerals 2018, 8(3), 109; doi:10.3390/min8030109
Received: 19 February 2018 / Revised: 5 March 2018 / Accepted: 5 March 2018 / Published: 8 March 2018
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Abstract
Ariegilatite, BaCa12(SiO4)4(PO4)2F2O (R3¯m, a = 7.1551(6) Å, c = 41.303(3) Å, V = 1831.2(3) Å3, Z = 3), is a new member of the
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Ariegilatite, BaCa12(SiO4)4(PO4)2F2O (R 3 ¯ m, a = 7.1551(6) Å, c = 41.303(3) Å, V = 1831.2(3) Å3, Z = 3), is a new member of the nabimusaite group exhibiting a modular intercalated antiperovskite structure derived from hatrurite. It was found in a few outcrops of pyrometamorphic rocks of the Hatrurim Complex located in the territories of Israel, Palestine and Jordan. The holotype specimen is an altered spurrite marble from the Negev Desert near Arad city, Israel. Ariegilatite is associated with spurrite, calcite, brownmillerite, shulamitite, CO3-bearing fluorapatite, fluormayenite-fluorkyuygenite and a potentially new mineral, Ba2Ca18(SiO4)6(PO4)3(CO3)F3O. Ariegilatite is overgrown and partially replaced by stracherite, BaCa6(SiO4)2[(PO4)(CO3)]F. The mineral forms flat disc-shaped crystals up to 0.5 mm in size. It is colorless, transparent, with white steaks and vitreous luster. Optically, ariegilatite is uniaxial, negative: ω = 1.650(2), ε = 1.647(2) (λ = 589 nm). The mean composition of the holotype ariegilatite, (Ba0.98K0.01Na0.01)Σ1(Ca11.77Na0.08Fe2+0.06Mn2+0.05Mg0.04)Σ12(Si3.95Al0.03Ti0.02)Σ4(P1.70C0.16Si0.10S6+0.03V0.01)Σ2F2.04O0.96, is close to the end-member formula. The structure of ariegilatite is described as a stacking of the two modules {F2OCa12(SiO4)4}4+ and {Ba(PO4)2}4− along (001). Ariegilatite, as well as associated stracherite, are high-temperature alteration products of minerals of an early clinker-like association. These alterations took place under the influence of pyrometamorphism by-products, such as gases and fluids generated by closely-spaced combustion foci. Full article
(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)
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Open AccessArticle Predicting Cyanide Consumption in Gold Leaching: A Kinetic and Thermodynamic Modeling Approach
Minerals 2018, 8(3), 110; doi:10.3390/min8030110
Received: 18 January 2018 / Revised: 14 February 2018 / Accepted: 5 March 2018 / Published: 8 March 2018
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Abstract
The consumption of cyanide during processing operations is a major economic cost in the extraction of gold from its ores, while the discharge of cyanide wastes may result in significant environmental pollution. Many factors influence the levels of consumption and discharge of cyanide,
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The consumption of cyanide during processing operations is a major economic cost in the extraction of gold from its ores, while the discharge of cyanide wastes may result in significant environmental pollution. Many factors influence the levels of consumption and discharge of cyanide, including ore mineralogy and lixiviant solution chemistry. This paper proposes a robust methodology to estimate leaching cyanide consumption due to oxidation and reactions with gold, chalcopyrite and pyrite minerals forming various cyanide complexes, cyanate, thiocyanate and hydroxide precipitates of copper and iron. The method involves concurrent modelling of both the oxidation and leaching kinetics of minerals and the chemical speciation of the lixiviant solutions. The model was calibrated by conducting cyanide leaching experiments on pyrite, chalcopyrite, pyrite + chalcopyrite, pyrite + chalcopyrite + gold and pyrite + chalcopyrite + gold + quartz systems and determining the total Cu, Fe, Au and CN concentrations in solution. We show that this model can successfully estimate the formation of cyanide complexes and, hence, the consumption of cyanide. Full article
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Open AccessArticle Geochronology and Genesis of the Xitian W-Sn Polymetallic Deposit in Eastern Hunan Province, South China: Evidence from Zircon U-Pb and Muscovite Ar-Ar Dating, Petrochemistry, and Wolframite Sr-Nd-Pb Isotopes
Minerals 2018, 8(3), 111; doi:10.3390/min8030111
Received: 6 February 2018 / Revised: 22 February 2018 / Accepted: 24 February 2018 / Published: 8 March 2018
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Abstract
The recently explored Xitian tungsten-tin (W-Sn) polymetallic ore field, located in Hunan province, South China, is one of the largest ore fields in the Nanling Range (NLR). Two major metallogenic types appeared in this ore field, skarn- and quartz vein-type. They are distributed
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The recently explored Xitian tungsten-tin (W-Sn) polymetallic ore field, located in Hunan province, South China, is one of the largest ore fields in the Nanling Range (NLR). Two major metallogenic types appeared in this ore field, skarn- and quartz vein-type. They are distributed within Longshang, Heshuxia, Shaiheling, Hejiangkou, Goudalan, and so on. Hydrothermal zircons from two altered granites yielded U-Pb ages of 152.8 ± 1.1 Ma, and 226.0 ± 2.8 Ma, respectively. Two muscovite samples from ore-bearing quartz vein yielded 40Ar/39Ar plateau ages of 156.6 ± 0.7 Ma, 149.5 ± 0.8 Ma, respectively. Combined with the geological evidence, two metallogenic events are proposed in the Xitian ore field, with skarn-type W-Sn mineralization in Late Triassic (Indosinian) and quartz vein/greisen type W-Sn mineralization in Late Jurassic (Yanshanian). The relatively low Ce/Ce* ratios and high Y/Ho ratios in zircons from two altered granites indicate that the hydrothermal fluids of two metallogenic events are characterized by low oxygen fugacities and enrichment in F. The similar chondrite-normalized patterns between the skarn and Xitian Indosinian granites and Sr-Nd-Pb isotopic compositions of wolframite suggest that the metal sources for both types W-Sn mineralization are derived from a crustal source. Full article
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Open AccessArticle Intercalation and Exfoliation of Kaolinite with Sodium Dodecyl Sulfate
Minerals 2018, 8(3), 112; doi:10.3390/min8030112
Received: 24 January 2018 / Revised: 26 February 2018 / Accepted: 7 March 2018 / Published: 9 March 2018
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Abstract
Kaolinite (Kaol) was intercalated with dimethyl sulfoxide (DMSO) and subsequently methanol (MeOH) to prepare intercalation compounds Kaol-DMSO and Kaol-MeOH. Kaol-MeOH was used as an intermediate to synthesize Kaol-sodium dodecyl sulfate (SDS) intercalation compound (Kaol-SDS) via displacement reaction. The ultrasonic exfoliation of Kaol-SDS produced
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Kaolinite (Kaol) was intercalated with dimethyl sulfoxide (DMSO) and subsequently methanol (MeOH) to prepare intercalation compounds Kaol-DMSO and Kaol-MeOH. Kaol-MeOH was used as an intermediate to synthesize Kaol-sodium dodecyl sulfate (SDS) intercalation compound (Kaol-SDS) via displacement reaction. The ultrasonic exfoliation of Kaol-SDS produced a resultant Kaol-SDS-U. The samples were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), thermal analysis, scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and particle size analysis. The results revealed that the intercalation of sodium dodecyl sulfate into kaolinite layers caused an obvious increase of the basal spacing from 0.72–4.21 nm. The dehydroxylation temperature of Kaol-SDS was obviously lower than that of original kaolinite. During the intercalation process of sodium dodecyl sulfate, a few kaolinite layers were exfoliated and curled up from the edges of the kaolinite sheets. After sonication treatment, the kaolinite layers were further transformed into nanoscrolls, and the exfoliated resultant Kaol-SDS-U possessed a smaller particle size close to nanoscale. Full article
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Open AccessArticle Evaluation of Microwave Intensified Vanadium Bearing-High Carbonaceous Shale Acid Extraction Process
Minerals 2018, 8(3), 113; doi:10.3390/min8030113
Received: 11 January 2018 / Revised: 2 February 2018 / Accepted: 5 March 2018 / Published: 9 March 2018
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Abstract
The microwave assisted leaching of the vanadium bearing-high carbonaceous shale process was investigated using surface response methodology (RSM) based on Box–Behnken design (BBD). The effect of important factors such as CaF2 usage, H2SO4 concentration, leaching time and microwave power,
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The microwave assisted leaching of the vanadium bearing-high carbonaceous shale process was investigated using surface response methodology (RSM) based on Box–Behnken design (BBD). The effect of important factors such as CaF2 usage, H2SO4 concentration, leaching time and microwave power, as well as the interactive coefficients, the signification of the model and factors were analyzed. With the condition of 9.8 wt % CaF2, 23.0 vol % H2SO4, 170.6 min and 350 W, the actual values of vanadium (V) leaching efficiency in microwave heating (MH) and conventional heating (CH) were 85.43% and 79.64%, which agreed well with the predicted values. Meanwhile, the influence order of the factors in MH and CH was CaF2 dosage > H2SO4 concentration > leaching time. Microwave was an efficacious impetus for V extraction, but the microwave power itself was not a significant factor when the temperature of leaching system was high enough. The further characterization of mineral components before and after leaching confirmed that the prior dissolving of muscovite and pyrite in MH was intensified, while both minerals were in fine grains and filled with black carbon. The selective heating of carbon and pyrite sequenced the large temperature gradient between solids and liquids, which accelerated the dissolving reaction of muscovite with CaF2 present in MH condition. Full article
(This article belongs to the Special Issue Towards Sustainability in Extractive Metallurgy)
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Open AccessArticle Comprehensive Analysis of External Dependency in Terms of Material Criticality by Employing Total Material Requirement: Sulfuric Acid Production in Japan as a Case Study
Minerals 2018, 8(3), 114; doi:10.3390/min8030114
Received: 14 January 2018 / Revised: 7 February 2018 / Accepted: 7 March 2018 / Published: 12 March 2018
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Abstract
Securing stable material supply is of paramount importance since materials are fundamental to the economy and human well-being. The domestic production to consumption ratio has conventionally been utilized as a main index for external dependency in terms of material supply security and its
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Securing stable material supply is of paramount importance since materials are fundamental to the economy and human well-being. The domestic production to consumption ratio has conventionally been utilized as a main index for external dependency in terms of material supply security and its criticality. However, the conventional approach confines its application to raw materials, which potentially risks reaching short-sighted conclusions in the policy-making process. Beyond the conventional analysis of external dependency, the development of a more applicable approach for every material is of paramount importance to consider the diversification of external dependency more comprehensively and to aid the analysis of overall material criticality. As such, this paper establishes a new methodology for analyzing external dependency related to every material and product by using the concept of total material requirement (TMR). Applying the methodology, the external dependency of sulfuric acid production in Japan is evaluated as a case study. Previously unexamined elements associated with external dependency in the conventional approach are revealed by this new comprehensive approach. The new approach may be of use to policymakers in designing more sophisticated and well-grounded material securement policy. Full article
(This article belongs to the Special Issue Critical Minerals: Methodologies and Case Studies)
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Open AccessArticle Fundamental Flotation Behaviors of Chalcopyrite and Galena Using O-Isopropyl-N-Ethyl Thionocarbamate as a Collector
Minerals 2018, 8(3), 115; doi:10.3390/min8030115
Received: 31 January 2018 / Revised: 8 March 2018 / Accepted: 12 March 2018 / Published: 13 March 2018
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Abstract
Copper and lead are two important and widely used metals in industry. Chalcopyrite (CuFeS2) is associated with galena (PbS) in ore, and it has been a research hotspot in separating galena from chalcopyrite by flotation. In this study, the flotation behaviors
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Copper and lead are two important and widely used metals in industry. Chalcopyrite (CuFeS2) is associated with galena (PbS) in ore, and it has been a research hotspot in separating galena from chalcopyrite by flotation. In this study, the flotation behaviors of chalcopyrite and galena were studied through flotation tests, adsorption measurements, solution chemistry calculation, Fourier transform infrared spectroscopy (FTIR) and molecular dynamics (MD) simulations. The results show that the floatability of chalcopyrite is better than that of galena in the presence of O-isopropyl-N-ethyl thionocarbamate (IPETC), and the recovery difference between chalcopyrite and galena is about 20% when IPETC is 7 × 10−4 mol/L at pH 9.5, while the floatability difference between the two minerals is significant. Competitive adsorption of OH and IPETC on mineral surfaces leads to lower floatability of galena than that of chalcopyrite. IPETC is able to remove the hydration layer on mineral surfaces and then adsorb on active sites. The floatability of minerals is enhanced with the increase of their hydrophobicity. This study provides a reference to separate galena from chalcopyrite. Full article
(This article belongs to the Special Issue Flotation Chemistry)
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Open AccessArticle Zeolite Synthesized from Coal Fly Ash Produced by a Gasification Process for Ni2+ Removal from Water
Minerals 2018, 8(3), 116; doi:10.3390/min8030116
Received: 24 January 2018 / Revised: 12 March 2018 / Accepted: 13 March 2018 / Published: 14 March 2018
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Abstract
There are increasing demands and great potential of coal gasification in China, but there is a lack of studies focused on the disposal and utilization of coal fly ash produced by the gasification process. In this study, a coal fly ash sample derived
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There are increasing demands and great potential of coal gasification in China, but there is a lack of studies focused on the disposal and utilization of coal fly ash produced by the gasification process. In this study, a coal fly ash sample derived from a gasifier in Jincheng, China, was utilized as raw material for the synthesis of zeolite by alkali fusion followed by hydrothermal treatments. The effects of operation conditions on the cation exchange capacity (CEC) of synthesized zeolite were investigated. The synthesized zeolite with the highest CEC (270.4 meq/100 g), with abundant zeolite X and small amount of zeolite A, was produced by 1.5 h alkali fusion under 550 °C with NaOH/coal fly ash ratio 1.2 g/g followed by 15 h hydrothermal treatment under 90 °C with liquid/solid ratio 5 mL/g and applied in Ni2+ removal from water. The removal rate and the adsorption capacity of Ni2+ from water by the synthesized zeolite were determined at the different pH, contact time, adsorbent dose and initial Ni2+ concentration. The experimental data of adsorption were interpreted in terms of Freundlich and Langmuir equations. The adsorption of Ni2+ by the synthesized zeolite was found to fit sufficient using the Langmuir isotherm. More than 90% of Ni2+ in water could be removed by synthesized zeolite under the proper conditions. We show that the coal fly ash produced by the gasification process has great potential to be used as an alternative and cheap source in the production of adsorbents. Full article
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Open AccessArticle Experimental Study of CO2-Water-Mineral Interactions and Their Influence on the Permeability of Coking Coal and Implications for CO2-ECBM
Minerals 2018, 8(3), 117; doi:10.3390/min8030117
Received: 18 January 2018 / Revised: 6 March 2018 / Accepted: 14 March 2018 / Published: 19 March 2018
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Abstract
Coal permeability is one of the most critical parameters affecting gas flow behavior during coalbed methane (CBM) production. However, little research has been conducted on how permeability evolves after CO2 injection in coking coal. Hence, examining possible chemical interactions between coal minerals,
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Coal permeability is one of the most critical parameters affecting gas flow behavior during coalbed methane (CBM) production. However, little research has been conducted on how permeability evolves after CO2 injection in coking coal. Hence, examining possible chemical interactions between coal minerals, water, and injected CO2 can be very helpful to better characterize coking coal. In this study, coking coal specimens obtained from the Malan and Tunlan mines located in the Gujiao block of the Qinshui basin were treated with water and CO2 to achieve a better understanding of their dissolution kinetics, pore structure, and permeability. It was found that the relative carbonate mineral content decreases with time, while the relative clay mineral content increases after the reaction with CO2 and water. Scanning electron microscopy (SEM) confirmed these mineral alteration phenomena. Carbonate minerals (calcite, dolomite) dissolve faster than clay minerals (montmorillonite, illite and kaolinite). In particular, the dissolution rates of Ca2+ in carbonate minerals increases with decreasing temperature (25–45 °C) and pH (4.3–6.3), and the dissolution rate of Ca2+ ions in the calcite reaction solution is higher than that in the dolomite solution. In addition, the results of low-pressure nitrogen adsorption analysis showed that CO2 injection can enlarge smaller size pores into larger size pores and change the overall pore size distribution. Therefore, CO2 injection can increase the porosity of coal beds and ultimately their permeability, which in turn facilitates CBM production. Full article
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Open AccessArticle Near-Field Optical Examination of Potassium n-Butyl Xanthate/Chalcopyrite Flotation Products
Minerals 2018, 8(3), 118; doi:10.3390/min8030118
Received: 9 February 2018 / Revised: 14 March 2018 / Accepted: 15 March 2018 / Published: 19 March 2018
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Abstract
The present study introduces scattering-type scanning near-field infrared optical nanospectroscopy (s-SNIM) as a valuable and well-suited tool for spectrally fingerprinting n-butyl xanthate (KBX) molecules adsorbed to chalcopyrite (CCP) sample surfaces. The collector KBX is well known to float CCP and is used
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The present study introduces scattering-type scanning near-field infrared optical nanospectroscopy (s-SNIM) as a valuable and well-suited tool for spectrally fingerprinting n-butyl xanthate (KBX) molecules adsorbed to chalcopyrite (CCP) sample surfaces. The collector KBX is well known to float CCP and is used in beneficiation. We thus identified KBX reaction products both by IR optical far- and near-field techniques, applying attenuated total internal reflection Fourier-transform infrared spectroscopy (ATR FT-IR) in comparison to s-SNIM, respectively. The major KBX band around 880 cm−1 was probed in s-SNIM using both the tunable free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf facility, Germany, and table-top CO2 laser illumination. We then were able to monitor the KBX agglomeration in patches <500 nm in diameter at the CCP surface, as well as nanospectroscopically identify the presence of KBX reaction products down to the 10−4 M concentration. Full article
(This article belongs to the Special Issue Applications of Atomic Force Microscopy in Mineral Flotation)
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Open AccessArticle Comparative Study of the Mineral Composition and Its Connection with Some Properties Important for the Sludge Flocculation Process-Examples from Omarska Mine
Minerals 2018, 8(3), 119; doi:10.3390/min8030119
Received: 6 February 2018 / Revised: 3 March 2018 / Accepted: 15 March 2018 / Published: 20 March 2018
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Abstract
Studied sludge samples are composed of major goethite and quartz; less clay minerals; and minor magnetite, hematite, clinochlore and todorokite. They have quite similar qualitative, but different semi-quantitative compositions. There are similar particle size distributions between the samples, and the highest contents of
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Studied sludge samples are composed of major goethite and quartz; less clay minerals; and minor magnetite, hematite, clinochlore and todorokite. They have quite similar qualitative, but different semi-quantitative compositions. There are similar particle size distributions between the samples, and the highest contents of ~50% belongs to the finest classes of <6 μm. Among size classes within the samples, almost identical iron contents are present; indicating their similar mineral compositions, which make these systems very complex for further separation processes. Sludge II has a higher natural settling rate, due to its higher density and mineral composition. With addition of the flocculant, settling rates increase significantly with the increase of the liquid component in both of the samples. The effect of flocculant on the settling rate is different between samples, and depends on their mineral composition. The time of settling does not play a role in selectivity, to the ratio of the mass of floating and sinking parts, and iron content does not change with time. The content of iron partially increases by flocculation; therefore, this method should be considered as an appropriate one. Zeta potential values for sludge are mostly between those for goethite and quartz, indicating their particle mixture and intricately association. Full article
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Open AccessArticle The Use of Infrared Spectroscopy to Determine the Quality of Carbonate-Rich Diatomite Ores
Minerals 2018, 8(3), 120; doi:10.3390/min8030120
Received: 28 February 2018 / Revised: 15 March 2018 / Accepted: 17 March 2018 / Published: 20 March 2018
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Abstract
Diatomite, a rock formed by the accumulation of opaline diatom frustules, is a preferred raw material for the manufacturing of filters. Its uniqueness relies on the high porosity and inertness of the frustules. The presence of carbonates in some diatomite ores hinders these
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Diatomite, a rock formed by the accumulation of opaline diatom frustules, is a preferred raw material for the manufacturing of filters. Its uniqueness relies on the high porosity and inertness of the frustules. The presence of carbonates in some diatomite ores hinders these properties. The purpose of this study was to identify the type of carbonates and their association with the ore in a diatomite deposit, and to assess the suitability of determining the quality of the ore using techniques with potential for in-pit implementation. For this, run-of-mine samples were analysed using environmental scanning electron microscopy (ESEM) and infrared spectroscopy. The ESEM images showed that carbonate is present as cement and laminae. The infrared data revealed that the carbonate minerals correspond to aragonite and calcite, and that their occurrence is linked to the total amount of carbonate in the sample. By using a portable spectral instrument that uses diffuse reflectance, it was possible to classify the spectra of the ore samples based on the carbonate content. These results indicate that infrared technology could be used on-site for determining the quality of the ore, thus providing relevant information to assist the optimisation of mining and beneficiation activities. Full article
(This article belongs to the Special Issue Mineralogy of Quartz and Silica Minerals)
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Open AccessReview Trends in Structure and Thermodynamic Properties of Normal Rare Earth Carbonates and Rare Earth Hydroxycarbonates
Minerals 2018, 8(3), 106; doi:10.3390/min8030106
Received: 28 January 2018 / Revised: 22 February 2018 / Accepted: 23 February 2018 / Published: 7 March 2018
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Abstract
A general overview of the trends in structural and thermodynamic properties that have been identified within the hydrated normal rare earth carbonates and the rare earth hydroxycarbonates is presented. Based upon available literature, we demonstrate the trends in crystallographic unit cell parameters, thermal
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A general overview of the trends in structural and thermodynamic properties that have been identified within the hydrated normal rare earth carbonates and the rare earth hydroxycarbonates is presented. Based upon available literature, we demonstrate the trends in crystallographic unit cell parameters, thermal stability, aqueous solubility, and thermochemical properties. These trends can be attributed to both the unique chemistry and strong similarity of the rare earth elements. There are also inconsistent trends that signal research needs to better understand the structure–energy relationships of the rare earth carbonates. Full article
(This article belongs to the Special Issue Rare-Earth Carbonates)
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