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Minerals, Volume 7, Issue 6 (June 2017) – 21 articles

Cover Story (view full-size image): We report on a tuff derived from alkali mafic volcanic ash with relatively high concentrations of critical metals, including Nb, Ta, Zr, Hf, rare earth elements, and Y in southwestern China. The clay mineralogy of the tuff profile changes vertically due to the change in the depositional environment. Although the original volcanic ash was mainly deposited in a continental environment, marine water may have percolated to the uppermost layers of the ash bed during early diagenesis, leading to the formation of concretions of concentric rings of kaolinite and illite. View the paper
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Review
Microbial Diversity and Community Assembly across Environmental Gradients in Acid Mine Drainage
Minerals 2017, 7(6), 106; https://doi.org/10.3390/min7060106 - 20 Jun 2017
Cited by 35 | Viewed by 3209
Abstract
Microorganisms play an important role in weathering sulfide minerals worldwide and thrive in metal-rich and extremely acidic environments in acid mine drainage (AMD). Advanced molecular methods provide in-depth information on the microbial diversity and community dynamics in the AMD-generating environment. Although the diversity [...] Read more.
Microorganisms play an important role in weathering sulfide minerals worldwide and thrive in metal-rich and extremely acidic environments in acid mine drainage (AMD). Advanced molecular methods provide in-depth information on the microbial diversity and community dynamics in the AMD-generating environment. Although the diversity is relatively low and in general inversely correlated with the acidity, a considerable number of microbial species have been detected and described in AMD ecosystems. The acidophilic microbial communities dominated by iron/sulfur-oxidizing microbes vary widely in their composition and structure across diverse environmental gradients. Environmental conditions affect the microbial community assembly via direct and indirect interactions with microbes, resulting in an environmentally dependent biogeographic pattern. This article summarizes the latest studies to provide a better understanding of the microbial biodiversity and community assembly in AMD environments. Full article
(This article belongs to the Special Issue Biogeochemistry of Acid Mine Drainage)
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Article
Heterotrophic Microbial Stimulation through Biosolids Addition for Enhanced Acid Mine Drainage Control
Minerals 2017, 7(6), 105; https://doi.org/10.3390/min7060105 - 19 Jun 2017
Cited by 14 | Viewed by 2894
Abstract
The effective control and treatment of acid mine drainage (AMD) from sulfide-containing mine wastes is of fundamental importance for current and future long-term sustainable and cost-effective mining industry operations, and for sustainable management of legacy AMD sites. Historically, AMD management has focused on [...] Read more.
The effective control and treatment of acid mine drainage (AMD) from sulfide-containing mine wastes is of fundamental importance for current and future long-term sustainable and cost-effective mining industry operations, and for sustainable management of legacy AMD sites. Historically, AMD management has focused on the use of expensive neutralising chemicals to treat toxic leachates. Accordingly, there is a need to develop more cost-effective and efficient methods to prevent AMD at source. Laboratory kinetic leach column experiments, designed to mimic a sulfide-containing waste rock dump, were conducted to assess the potential of organic waste carbon supplements to stimulate heterotrophic microbial growth, and supress pyrite oxidation and AMD production. Microbiological results showed that the addition of biosolids was effective at maintaining high microbial heterotroph populations and preventing AMD generation over a period of 80 weeks, as verified by leachate chemistry and electron microscopy analyses. This research contributes to the ongoing development of a cost effective, multi-barrier geochemical-microbial control strategy for reduced mineral sulfide oxidation rates at source. Full article
(This article belongs to the Special Issue Biogeochemistry of Acid Mine Drainage)
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Article
The Influence of Ca2+ and pH on the Interaction between PAHs and Molybdenite Edges
Minerals 2017, 7(6), 104; https://doi.org/10.3390/min7060104 - 17 Jun 2017
Cited by 11 | Viewed by 2202
Abstract
Nonpolar hydrocarbon oils are widely used as collectors for floating molybdenite. However, they can only adsorb on molybdenite faces and not on molybdenite edges, resulting in limited molybdenite recovery, especially in processed water containing a high amounts of Ca2+. In this [...] Read more.
Nonpolar hydrocarbon oils are widely used as collectors for floating molybdenite. However, they can only adsorb on molybdenite faces and not on molybdenite edges, resulting in limited molybdenite recovery, especially in processed water containing a high amounts of Ca2+. In this study, the influence of Ca2+ and pH on the adsorption of polycyclic aromatic hydrocarbons (PAHs), as part of composite collection on molybdenite edges, was studied. It was found that PAHs could only adsorb on molybdenite edges in the presence of Ca2+. Ca2+ reacted with molybdenite edges to form CaMoO4 precipitates. Then, CaMoO4 precipitates interacted with PAHs to form a structure of π–cation–π by (1) the cation–π interaction, (2) the π–π interaction and (3) the electrostatic interaction. It was also found that CaMoO4 precipitates on molybdenite edges promoted the adsorption of PAHs. The more the CaMoO4 precipitates, the easier the PAHs adsorption occurred. As a result, the high amount of Ca2+and low pH enhanced the adsorption of PAHs on molybdenite edges. This study provides insights into reducing the deleterious effect of Ca2+ on fine molybdenite flotation. Full article
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Article
Optimization Mechanism of Additive of Composite Sodium Salts on Vanadium Oxidation of Siliceous Shale
Minerals 2017, 7(6), 103; https://doi.org/10.3390/min7060103 - 17 Jun 2017
Cited by 3 | Viewed by 2275
Abstract
The promotion of strengthening of vanadium oxidation by compound additive of sodium salts is described from the changes of the vanadium valence state and mineral phase. The results are as follows: during the roasting process, dehydroxy mica converts to the melt, which the [...] Read more.
The promotion of strengthening of vanadium oxidation by compound additive of sodium salts is described from the changes of the vanadium valence state and mineral phase. The results are as follows: during the roasting process, dehydroxy mica converts to the melt, which the composite system mainly contains Na, K, Al, Si, and O. Under the action of NaCl-Na2CO3, ion exchange between sodium and potassium promotes the crystallization of albite from the melt. Na2CO3 enhances the reactivity of quartz. The albite reacts with activated quartz, which promotes the migration of sodium ions and the generation of vanadate. Under the action of NaCl-Na2SO4, The crystallization of spinel in the melt is promoted and that of the albite is inhibited. Under the action of Na2SO4-Na2CO3, the permeability of ore is deteriorated. The ion exchange process and the vanadium oxidation is inhibited from the melt. The composite additive with three sodium salts shows a stronger promoting effect on vanadium oxidation. The contribution of NaCl and Na2CO3 to V(V) in roasted slag was the highest among three sodium salts. With a certain ratio of NaCl and Na2CO3, the low content of Na2SO4 did not significantly affect the V(V) content in roasted slag. Full article
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Article
Flotation Separation of Scheelite from Fluorite Using Sodium Polyacrylate as Inhibitor
Minerals 2017, 7(6), 102; https://doi.org/10.3390/min7060102 - 16 Jun 2017
Cited by 17 | Viewed by 2790
Abstract
The depressing properties of sodium polyacrylate (PA-Na) for scheelite and fluorite were studied by micro-flotation tests, infrared spectroscopy (IR), zeta potentials, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The flotation results reveal that the selective depression effect of PA-Na is better [...] Read more.
The depressing properties of sodium polyacrylate (PA-Na) for scheelite and fluorite were studied by micro-flotation tests, infrared spectroscopy (IR), zeta potentials, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The flotation results reveal that the selective depression effect of PA-Na is better than that of sodium silicate, and PA-Na can depress fluorite more effectively than scheelite. The flotation recovery of scheelite and fluorite keeps at about 75% and 10%, respectively, at the pulp pH 9.3~9.6 and PA-Na concentration from 30 to 50 mg/L. IR spectra results suggest that PA-Na has a chemical effect on the surface of scheelite and fluorite. The zeta potential of fluorite becomes more negative than that of scheelite after PA-Na addition. XPS analysis deduces the occurrence of chemisorption between PA-Na and mineral surfaces, and the chemisorption of PA-Na on fluorite is stronger than on scheelite. DFT demonstrates that the absolute value of the adsorption energy in the presence of PA-Na is larger on the fluorite {111} surface than on the scheelite {111} surface. Thus, fluorite is more readily depressed than scheelite, which remarkably matches the micro-flotation test results. Full article
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Article
Mineralogy of Zn–Hg–S and Hg–Se–S Series Minerals in Carbonate-Hosted Mercury Deposits in Western Hunan, South China
Minerals 2017, 7(6), 101; https://doi.org/10.3390/min7060101 - 15 Jun 2017
Cited by 3 | Viewed by 2257
Abstract
Among the Zn–Hg–S and Hg–Se–S series minerals, Hg-bearing sphalerite and metacinnabar are uncommon in ore deposits, but they are useful indicators of temporal variation of ore forming fluids, as well as presenting metallurgical implications for Hg-bearing deposits. To understand the Hg–Zn–Se mineralization system [...] Read more.
Among the Zn–Hg–S and Hg–Se–S series minerals, Hg-bearing sphalerite and metacinnabar are uncommon in ore deposits, but they are useful indicators of temporal variation of ore forming fluids, as well as presenting metallurgical implications for Hg-bearing deposits. To understand the Hg–Zn–Se mineralization system of the Tongren–Fenghuang Hg Belt (TFHB), the Zn–Hg–S and Hg–Se–S series minerals of the Chashula Hg–Zn and Dongping Hg–Ag–Se carbonate-hosted deposits were studied by microscopic observation, electron-probe microanalysis, and X-ray diffraction analysis. Observations show that the Chashula and Dongping deposits experienced two stages of mineralization (Stages 1 and 2). The pyrite, sphalerite I (Hg-poor sphalerite), and quartz formed in Stage 1, while the Zn-bearing cinnabar, sphalerite II (Hg-bearing sphalerite), cinnabar, selenium metacinnabar, and Ag minerals formed in Stage 2. The Hg-bearing sphalerite, containing 13.36–22.26 wt % Hg (average 18.73 wt % Hg), replaces sphalerite I (0.00–1.31 wt % Hg). The Hg-bearing sphalerite of the Dongping Hg–Ag–Se deposit contains lower Hg (10.12–14.67 wt % Hg) than that of the Chashula deposit. The unit cell a of the Hg-bearing sphalerite gradually increases with increasing Hg content. The texture of the Zn-bearing cinnabar shows it is not stable and easily breaks down to Hg-bearing sphalerite and cinnabar through the chemical reaction: (Hg,Zn)S → (Zn,Hg)S + HgS. Selenium metacinnabar intergrowths with tetrahedrite and miargyrite were found only in the Dongping deposit. The selenium metacinnabar contains 76.57–83.97 wt % Hg, and extensive isomorphic substitution of Se and S (6.81–19.21 wt % Se, 4.14–10.32 wt % S). Based on our mineralogical studies, the Zn, Hg, Hg–Zn, and Hg–Se mineralization styles in the TFHB are interpreted as the product of different stages in the mineralization process. Full article
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Article
The Hydrothermal Fluid Evolution of Vein Sets at the Pipeline Gold Mine, Nevada
Minerals 2017, 7(6), 100; https://doi.org/10.3390/min7060100 - 13 Jun 2017
Cited by 4 | Viewed by 2496
Abstract
The origin of sediment-hosted Nevada gold deposits has been highly debated, especially regarding the relative contribution of multiple mineralizing events, particularly relating to the Cretaceous. We examined the Pipeline gold mine in north-central Nevada, focusing on data from the four vein sets in [...] Read more.
The origin of sediment-hosted Nevada gold deposits has been highly debated, especially regarding the relative contribution of multiple mineralizing events, particularly relating to the Cretaceous. We examined the Pipeline gold mine in north-central Nevada, focusing on data from the four vein sets in this atypical deposit where there is evidence for Cretaceous gold mineralization. Only the third, a quartz-sericite-pyrite-calcite vein set, has any link with the alteration styles and gold mineralization within the Pipeline deposit. Our geochemical results from fluid inclusion microthermometry and gas analysis show that the fluids from which quartz deposited were sourced from condensing magmatic volatiles and were trapped at ~300 °C and 2 kbar lithostatic pressure (~8 km). 40Ar/39Ar dating of sericite demonstrates that the quartz-sericite-pyrite veins formed at ~92 Ma, matching the dates of gold-associated epigenetic illite. Ore fluids enriched in CO2 and H2S caused decarbonation thereby releasing Fe2+ that reacted with H2S to form pyrite. Decreasing H2S destabilized gold bisulfide complexes and deposited gold. We conclude that this process can occur in a single Cretaceous event in advance of potential Tertiary mineralization. Full article
(This article belongs to the Special Issue Fluid Inclusions: Study Methods, Applications and Case Histories)
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Article
The Role of Organic Matter in the Formation of High-Grade Al Deposits of the Dopolan Karst Type Bauxite, Iran: Mineralogy, Geochemistry, and Sulfur Isotope Data
Minerals 2017, 7(6), 97; https://doi.org/10.3390/min7060097 - 12 Jun 2017
Cited by 6 | Viewed by 2354
Abstract
Mineralogical and geochemical analyses of the Dopolan karstic bauxite ore were performed to identify the characteristics of four bauxite horizons, which comprise from top to bottom, bauxitic kaolinite, diaspore-rich bauxite, clay-rich bauxite, and pyrite-rich bauxite. Diaspore, kaolinite, and pyrite are the main minerals; [...] Read more.
Mineralogical and geochemical analyses of the Dopolan karstic bauxite ore were performed to identify the characteristics of four bauxite horizons, which comprise from top to bottom, bauxitic kaolinite, diaspore-rich bauxite, clay-rich bauxite, and pyrite-rich bauxite. Diaspore, kaolinite, and pyrite are the main minerals; böhmite, muscovite, rutile, and anatase are the accessory minerals. The main minerals of the Dopolan bauxite deposit indicate slightly acidic to alkaline reducing conditions during bauxitization. Immobile elements (Nb, Ta, Zr, Hf, and rare earth elements) are enriched in the diaspore-rich horizon, which also has the highest alumina content, whereas redox sensitive elements (e.g., Cr, Cu, Ni, Pb, Zn, Ag, U, and V) are enriched in the lowest horizon of pyrite-rich bauxite. The presence of a high content of organic matter was identified in different horizons of bauxitic ore from wet chemistry. The presence of organic matter favored Fe bioleaching, which resulted in Al enrichment and the formation of diaspore-rich bauxite. The leached Fe2+ reacted with the hydrogen sulfur that was produced due to bacterial metabolism, resulting in the formation of the pyrite-rich horizon towards the bottom of the Dopolan bauxite horizons. Biogeochemical activity in the Dopolan bauxitic ore was deduced from the reducing environment of bauxitization, and the deposition of framboidal and cubic or cubic/octahedral pyrite crystals, with large negative values of δ34S of pyrite (−10‰ to −34‰) and preserved fossil cells of microorganisms. Full article
(This article belongs to the Special Issue Organo-Mineral Interactions)
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Article
Effect of Additives on Arsenic, Boron and Selenium Leaching from Coal Fly Ash
Minerals 2017, 7(6), 99; https://doi.org/10.3390/min7060099 - 10 Jun 2017
Cited by 13 | Viewed by 2858
Abstract
The establishment of an inexpensive leaching control method to prevent the leaching of trace elements from fly ash is required for the utilization of large-scale fly ash as an embankment material. This study examined the effects of the additives on suppressing As, B, [...] Read more.
The establishment of an inexpensive leaching control method to prevent the leaching of trace elements from fly ash is required for the utilization of large-scale fly ash as an embankment material. This study examined the effects of the additives on suppressing As, B, and Se leaching from coal fly ash using Ca(OH)2, paper sludge ashes (PS Ash 3, PS Ash 4 and PS Ash 5), and filter cake (FC). PS Ash and FC are waste generated in the papermaking and lime industry processes and contain high levels of calcium. The treated fly ash H (FAH) and the resulting mixtures were subjected to a leaching test as per the Environmental Agency of Japan Notifications No. 13. The results indicate that the leaching concentrations of As, B, and Se could be greatly reduced in FAH with the highest effect given by Ca(OH)2, followed by PS Ash 3 and PS Ash 5. Ca(OH)2 greatly reduced both the leaching concentrations of As, B, and Se by about 91–100%, while PS Ash 3 reduced the As and B leaching concentrations by approximately 89–96% and 83–92%, respectively; and PS Ash 5 reduced the Se leaching concentration by about 87–96%. FC did not have any impact on As and B leaching, but reduced Se leaching by about 58–78%. A reason for the decrease in leaching concentrations of As, B, and Se may be the precipitation with calcium or the formation of ettringite. The presence of leached Ca and Na ions are key factors affecting the decrease of As, B, and Se leaching concentrations from fly ash. The utilization of PS Ash 3 and PS Ash 5 as inexpensive additives is a promising method to control the leaching of As, B, and Se into the environment. Full article
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Article
Mineralogical Characteristics and Preliminary Beneficiation of Nickel Slag from Reduction Roasting-Ammonia Leaching
Minerals 2017, 7(6), 98; https://doi.org/10.3390/min7060098 - 09 Jun 2017
Cited by 12 | Viewed by 2648
Abstract
The reduction roasting ammonia leaching process (RRAL) originally defined by Caron (1950) has been extensively applied to treat low grade nickel laterite and a large amount of slag-containing some valuable metals, has been generated and accumulated over the years since then. However, there [...] Read more.
The reduction roasting ammonia leaching process (RRAL) originally defined by Caron (1950) has been extensively applied to treat low grade nickel laterite and a large amount of slag-containing some valuable metals, has been generated and accumulated over the years since then. However, there are no reports on how to utilize it based on its essential properties. In this investigation, the textural and mineralogical characterization of the typical nickel slag from RRAL in Western Australia was performed by X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The results show that the nickel slag is dominated by magnetite, maghemite, gangue minerals and minor Cr-spinel. The magnetite and maghemite possess simple distribution relationship with other minerals and their particles are highly variable with most over 50 μm, which are easily able to be recovered. In term of the complex association and distribution feature of chromium and nickel minerals, it is very difficult to recovery them. Meanwhile, an economically viable extraction process was proposed to preliminarily utilize the nickel slag based on textural and mineralogical characteristics of the slag, and the magnetic concentrate, assaying about 62% iron grade at over 75% recovery rate, was obtained through the recommended method. Full article
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Article
Mechanism of Surrounding Rock Failure and Crack Evolution Rules in Branched Pillar Recovery
Minerals 2017, 7(6), 96; https://doi.org/10.3390/min7060096 - 08 Jun 2017
Cited by 9 | Viewed by 1941
Abstract
To study the mechanism of surface collapse and crack evolution in a roadway chain failure process in the pillar recovery of Hongling lead zinc ore in Inner Mongolia Province, China, microseismic monitoring technology, moment tensor theory, and numerical simulation are used for the [...] Read more.
To study the mechanism of surface collapse and crack evolution in a roadway chain failure process in the pillar recovery of Hongling lead zinc ore in Inner Mongolia Province, China, microseismic monitoring technology, moment tensor theory, and numerical simulation are used for the inversion of rock mass fracturing, the destruction type classification of crack, and the mechanism of surrounding rock. Research shows the following: (1) the rock mass fracturing is first produced within the +955 m level, before extending through the hanging wall to the ground surface. Then, many shear failures occur in the ground surface of the footwall, extending downwards in an arc-shaped path to the +905 m level. Finally, the surface gradually collapses with large-scale shear failures. (2) The mechanism of surface collapse is as follows: after the recovery of pillars in the +905 m level, tensile cracks generated in the top of orebody #2 extend upwards and obliquely. Analogously, shear cracks are generated in the top of orebody #1, extending upwards. After the recovery of pillars in the +855 m level, the marble interlayer is destroyed and sinks, and many tensile cracks and shear cracks exist and incise in the ground surface, which cause the ground surface to collapse. (3) The mechanism of crack evolution is as follows: after the recovery of 5107 pillars, the footwall haul road in the +905 m level was damaged and collapsed by the cut-through cracks. Those cracks then continue to extend upwards and converge with the slanting shear cracks in the +905 m level, which form a triangular failure in the footwall rock. Finally, the failure causes the tensile and shearing cracks in the haulage way of the +955 m level to extend and connect, which forms the haulage way chain failure. Full article
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Article
Precipitation of Carbonate Minerals Induced by the Halophilic Chromohalobacter Israelensis under High Salt Concentrations: Implications for Natural Environments
Minerals 2017, 7(6), 95; https://doi.org/10.3390/min7060095 - 08 Jun 2017
Cited by 27 | Viewed by 2381
Abstract
The precipitation of carbonate minerals induced by halophilic bacteria has aroused wide concern. The study aimed to investigate the characterization and process of biomineralization in high salt systems by halophilic Chromohalobacter israelensis LD532 (GenBank: KX766026) bacteria, isolated from the Yinjiashan Saltern in China. [...] Read more.
The precipitation of carbonate minerals induced by halophilic bacteria has aroused wide concern. The study aimed to investigate the characterization and process of biomineralization in high salt systems by halophilic Chromohalobacter israelensis LD532 (GenBank: KX766026) bacteria, isolated from the Yinjiashan Saltern in China. Carbonate minerals were induced in magnesium sulfate and magnesium chloride medium, respectively. The mineral phase, morphology, and elemental composition of minerals were analyzed using X-ray p owder diffraction, scanning electron microscopy, and energy dispersive X-ray detection. Cells and ultrathin slices were studied using high resolution transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray detection. The carbonic anhydrase and ammonia released from LD532 bacteria increased pH of the medium and promoted the carbonate precipitation. Magnesium calcite and aragonite were induced by LD532 bacteria in magnesium chloride medium at an Mg/Ca molar ratio of 2, while Magnesium calcite and monohydrocalcite were precipitated in magnesium sulfate medium at the same Mg/Ca ratio, only monohydrocalcite were formed in both control groups. The morphologies and compositions of minerals in MgSO4 and MgCl2 solutions displayed significant differences, indicating different Mg2+ could affect physiological and biochemical activities of LD532 bacteria and thus affect the mineral deposition. Further study showed the nucleation sites were located on extracellular polymeric substances and intracellular vesicles of LD532 bacteria. This study is beneficial to the mechanism of carbonate biomineralization in natural salt environments. Full article
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Article
Characterization and Separation Studies of a Fine Sedimentary Phosphate Ore Slime
Minerals 2017, 7(6), 94; https://doi.org/10.3390/min7060094 - 07 Jun 2017
Cited by 8 | Viewed by 2255
Abstract
Detailed characterization and recovery of apatite from a sedimentary phosphate ore slime of a gravity plant of Yichang, China, were investigated. The phosphate ore slime consisted mainly of apatite, quartz, dolomite, and clay. To start with, the ore slime was characterized in sufficient [...] Read more.
Detailed characterization and recovery of apatite from a sedimentary phosphate ore slime of a gravity plant of Yichang, China, were investigated. The phosphate ore slime consisted mainly of apatite, quartz, dolomite, and clay. To start with, the ore slime was characterized in sufficient detail to reveal that it is extremely fine in distribution with a d50 of 65 μm. Other different characterizations, such as apatite grain size distribution, apatite liberation, particle density distribution, and theoretical grade recovery, were also analyzed by mineral liberation analyser (MLA). Based on the results, a new gravity-flotation process, which was comprised of spiral gravity and reverse flotation, was proposed to process the slime. In the new process, the apatite was firstly recovered by two-stage spiral gravity, avoiding direct flotation. The gravity concentrate was the feed for the reverse flotation. A phosphate concentrate of 30.51% P2O5 with a P2O5 recovery of 89.00% can be produced from the slime analyzing 24.25% P2O5. Compared to the conventional direct-reverse flotation process, it was found that the reagent cost of the new gravity-flotation process was lower a quarter than that of the direct-reverse flotation flowsheet. Full article
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Article
PbSO4 Leaching in Citric Acid/Sodium Citrate Solution and Subsequent Yielding Lead Citrate via Controlled Crystallization
Minerals 2017, 7(6), 93; https://doi.org/10.3390/min7060093 - 06 Jun 2017
Cited by 9 | Viewed by 3034
Abstract
Lead citrate is a key precursor for the green recycling of spent lead acid battery paste in a citric acid/sodium citrate (CA/SC) solution. In this study, the main paste component, PbSO4, was leached and crystallized to yield lead citrate. Results showed [...] Read more.
Lead citrate is a key precursor for the green recycling of spent lead acid battery paste in a citric acid/sodium citrate (CA/SC) solution. In this study, the main paste component, PbSO4, was leached and crystallized to yield lead citrate. Results showed that the leaching of PbSO4 in citric acid/sodium citrate solution was remarkably enhanced by an increase in temperature from 35 °C to 95 °C and an increase in sodium citrate (SC) concentration from 50 to 650 g/L. In comparison, increasing the citric acid/sodium citrate molar ratio inhibited this leaching. Controlled crystallization through cooling the solution or adjusting the pH of the solution can effectively produce lead citrate crystals. The X-ray diffraction patterns of four products obtained in a comparison test were all consistent with Pb3(C6H5O7)2. However, the scanning electron microscopy analysis suggested that the morphology was distinct from rods to sheets, which were mainly affected by the temperature variation. Full article
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Article
Origin of Minerals and Critical Metals in an Argillized Tuff from the Huayingshan Coalfield, Southwestern China
Minerals 2017, 7(6), 92; https://doi.org/10.3390/min7060092 - 05 Jun 2017
Cited by 22 | Viewed by 2735
Abstract
This paper reports the minerals in an argillized tuff from the Lvshuidong mine, Huayingshan Coalfield, southwestern China. The clay assemblages of the samples are mainly kaolinite, varying proportions of illite and trace chlorite. Other minerals include various proportions of pyrite, small proportions of [...] Read more.
This paper reports the minerals in an argillized tuff from the Lvshuidong mine, Huayingshan Coalfield, southwestern China. The clay assemblages of the samples are mainly kaolinite, varying proportions of illite and trace chlorite. Other minerals include various proportions of pyrite, small proportions of carbonates (calcite and ankerite), anatase, rutile, hematite, florencite and rare analcite. The clay mineralogy of the tuff profile changes vertically due to the change in the depositional environment. Although illite is minor in the middle and lower parts of the profile, it is relatively abundant in a few topmost samples where the proportion of illite is comparable to that of kaolinite. This is probably because the original volcanic ash was mainly deposited in a continental environment, but marine water may have percolated to the uppermost layers of the ash bed during early diagenesis, leading to the formation of concretions of concentric rings of kaolinite and illite. The samples of this study are derived from alkali mafic volcanic ash with relatively high concentrations of critical metals, including Nb, Ta, Zr, Hf, rare earth elements and Y. Full article
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Article
Selenide Mineralization in the Příbram Uranium and Base-Metal District (Czech Republic)
Minerals 2017, 7(6), 91; https://doi.org/10.3390/min7060091 - 04 Jun 2017
Cited by 20 | Viewed by 3440
Abstract
Selenium mineralization in the Příbram uranium and base-metal district (Central Bohemia, Czech Republic) bound to uraninite occurrences in calcite hydrothermal veins is extremely diverse. The selenides antimonselite, athabascaite, bellidoite, berzelianite, brodtkorbite, bukovite, bytízite, cadmoselite, chaméanite, clausthalite, crookesite, dzharkenite, eskebornite, eucairite, ferroselite, giraudite, hakite, [...] Read more.
Selenium mineralization in the Příbram uranium and base-metal district (Central Bohemia, Czech Republic) bound to uraninite occurrences in calcite hydrothermal veins is extremely diverse. The selenides antimonselite, athabascaite, bellidoite, berzelianite, brodtkorbite, bukovite, bytízite, cadmoselite, chaméanite, clausthalite, crookesite, dzharkenite, eskebornite, eucairite, ferroselite, giraudite, hakite, klockmannite, naumannite, permingeatite, příbramite, sabatierite, tiemannite, and umangite were found here, including two new mineral phases: Hg-Cu-Sb and Cu-As selenides. Those selenides—and in some cases their sulphidic equivalents—are characterized using wavelength-dispersive spectroscopy, reflected light, powder X-ray diffraction, single crystal X-ray diffraction, Raman spectroscopy, and electron backscatter diffraction. The selenide mineralization in the Příbram uranium district is bound to the border of the carbonate-uraninite and subsequent carbonate-sulphidic stages. Selenides crystallized there at temperatures near 100 °C in the neutral-to-weakly-alkaline environment from solutions with high oxygen fugacity and a high Se2/S2 fugacity ratio. Full article
(This article belongs to the Special Issue Se-Bearing Minerals: Structure, Composition, and Origin)
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Article
Crystallization of Jarosite with Variable Al3+ Content: The Transition to Alunite
Minerals 2017, 7(6), 90; https://doi.org/10.3390/min7060090 - 01 Jun 2017
Cited by 8 | Viewed by 2359
Abstract
This study focused on the formation of the jarosite-alunite solid solution at relatively low temperature, 90 °C. It was found that the transition from jarosite to alunite results in significant changes in the powder X-ray diffraction pattern, the infrared spectrum and thermal behavior [...] Read more.
This study focused on the formation of the jarosite-alunite solid solution at relatively low temperature, 90 °C. It was found that the transition from jarosite to alunite results in significant changes in the powder X-ray diffraction pattern, the infrared spectrum and thermal behavior when the degree of substitution reached ≥50%. The initial Al/(Al + Fe) in solution, however, required to achieve these substitution levels in the solid is ≥90%. The morphology shows that the faceted jarosite form goes through an intergrown transition to a spherical morphology of pure alunite. This morphology has not been previously observed for alunite and most likely reflects the formation temperature. Rietveld analysis shows that the a lattice parameter obeys Vegard’s Rule while the c lattice parameter behavior is more complex. Empirical modelling of the incorporation of Fe into alunite supports the general trends found in the X-ray diffraction data for the behaviour of the a-axis with Al/Fe content. The dehydration of the Al3+ ion could be a significant contribution to the activation energy barrier to alunite formation as found for other minerals. Finally, dynamic light scattering showed that the nucleation behavior for jarosite and Fe-containing alunite are significantly different. Alunite appears to nucleate continuously rather than in a single nucleation event. Full article
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Article
Control of Acid Generation from Pyrite Oxidation in a Highly Reactive Natural Waste: A Laboratory Case Study
Minerals 2017, 7(6), 89; https://doi.org/10.3390/min7060089 - 30 May 2017
Cited by 8 | Viewed by 2137
Abstract
Laboratory kinetic leach column (KLC) tests were carried out to define the conditions required to control acid generation from a highly reactive, potentially acid-forming (PAF) iron ore waste rock. It was found that lime addition (0.1 wt % blended) plus either blending of [...] Read more.
Laboratory kinetic leach column (KLC) tests were carried out to define the conditions required to control acid generation from a highly reactive, potentially acid-forming (PAF) iron ore waste rock. It was found that lime addition (0.1 wt % blended) plus either blending of silicates (25 wt % K-feldspar and 25 wt % chlorite), or addition of a non-acid forming (NAF) top cover containing about 10% dolomite (PAF:NAF = 5:1 wt %), when watered/flushed with lime-saturated water, greatly reduced acid generation as compared to the control KLC (PAF alone, watered/flushed with Milli-Q water), but did not result in circum-neutral pH as required for pyrite surface passivation and effective acid and metalliferous drainage (AMD) mitigation. In contrast, the combined use of these treatments—blended lime and silicates with an NAF cover and watering/flushing with lime-saturated water—resulted in leachate pH of 12 (up to 24 weeks). Mass balance calculations for Ca2+ and scanning electron microscopy (SEM) analyses suggest that calcite or gypsum may have formed in the NAF-amended KLCs and lime with added silicate KLC. Although the combined approach in the form trialled here may not be practical or cost-effective, control of a highly reactive natural PAF waste by pyrite surface passivation appears to be possible, and an improved treatment methodology (e.g., slightly increased lime blending without the need for further lime watering/flushing) could usefully be examined in the future. Full article
(This article belongs to the Special Issue Biogeochemistry of Acid Mine Drainage)
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Article
Diagenesis and Reservoir Properties of the Permian Ecca Group Sandstones and Mudrocks in the Eastern Cape Province, South Africa
Minerals 2017, 7(6), 88; https://doi.org/10.3390/min7060088 - 30 May 2017
Cited by 30 | Viewed by 2940
Abstract
Diagenesis is one of the most important factors that affects reservoir rock property. Despite the fact that published data gives a vast amount of information on the geology, sedimentology, and lithostratigraphy of the Ecca Group in the Karoo Basin of South Africa, little [...] Read more.
Diagenesis is one of the most important factors that affects reservoir rock property. Despite the fact that published data gives a vast amount of information on the geology, sedimentology, and lithostratigraphy of the Ecca Group in the Karoo Basin of South Africa, little is known about the diagenesis of the potentially feasible or economically viable sandstones and mudrocks of the Ecca Group. This study aims to provide an account of the diagenesis of sandstones and mudstones from the Ecca Group. Twenty-five diagenetic textures and structures were identified and grouped into three stages that include early diagenesis, burial diagenesis and uplift-related diagenesis. Clay minerals are the most common cementing materials in the sandstones. Smectite, kaolinite, and illite are the major clay minerals that act as pore lining rims and pore-filling materials. A part of the clay minerals and detrital grains was strongly replaced by calcite. Calcite precipitates locally in the pore spaces and partially or completely replaced clay matrix, feldspar, and quartz grains at or around their margins. Precipitation of cements and formation of pyrite and authigenic minerals occurred during the early diagenetic stage. This process was followed by lithification and compaction which brought about an increase in tightness of grain packing, loss of pore spaces, and thinning of bedding thickness due to overloading of sediments and selective dissolution of the framework grains. Mineral overgrowths, mineral replacement, clay-mineral transformation, dissolution, deformation, and pressure solution occurred during burial diagenetic stage. After rocks were uplifted, weathered and unroofed by erosion, this resulted in decementation and oxidation of iron-rich minerals. The rocks of the Ecca Group were subjected to moderate-intense mechanical and chemical compaction during their progressive burial. Intergranular pores, secondary dissolution, and fractured pores are well developed in the sediments of the Ecca Group. The presence of fractured and dissolution pores tend to enhance reservoir quality. However, the isolated nature of the pore linkage makes them unfavorable producers of hydrocarbons, which at best would require stimulation. The understanding of the space and time distribution of diagenetic processes in these rocks will allow the development of predictive models of their reservoir quality, which may contribute to the reduction of risks involved in hydrocarbon (oil and gas) exploration. Full article
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Article
Synergetic Effect of the Mixed Anionic/Non-Ionic Collectors in Low Temperature Flotation of Scheelite
Minerals 2017, 7(6), 87; https://doi.org/10.3390/min7060087 - 26 May 2017
Cited by 14 | Viewed by 1785
Abstract
The synergetic effect of four octaphenyl polyoxyethyienes (TX) on low temperature flotation of scheelite at 9–11 °C was investigated through flotation experiments, and the adsorption mechanism was studied by way of surface tension, zeta potential, and adsorption measurement. The results show that the [...] Read more.
The synergetic effect of four octaphenyl polyoxyethyienes (TX) on low temperature flotation of scheelite at 9–11 °C was investigated through flotation experiments, and the adsorption mechanism was studied by way of surface tension, zeta potential, and adsorption measurement. The results show that the presence of the four octaphenyl polyoxyethyienes can improve scheelite flotation in a low concentration range, and their synergetic effects increase with the increase of the oxyethyl group (EO) number in their molecular structure, the mixed sodium oleate/TX-15 collector exhibits the best collecting performance for scheelite. Compared with sodium oleate alone, a larger reduced value of zeta potential is seen in the presence of the mixed collectors, and the adsorption of sodium oleate on the scheelite surface is enhanced for a constant sodium oleate concentration. Moreover, the synergetic effect of TX-15 can be well demonstrated through surface tension measurement, a lower critical micelle concentration (CMC) value of the mixed sodium oleate/TX-15 surfactant is obtained, indicating a higher surface property. Therefore, the mixed sodium oleate/TX-15 collector is suitable for low temperature flotation of scheelite. Full article
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Article
Coal-Based Reduction and Magnetic Separation Behavior of Low-Grade Vanadium-Titanium Magnetite Pellets
Minerals 2017, 7(6), 86; https://doi.org/10.3390/min7060086 - 23 May 2017
Cited by 9 | Viewed by 2199
Abstract
Coal-based reduction and magnetic separation behavior of low-grade vanadium-titanium magnetite pellets were studied in this paper. It is found that the metallization degree increased obviously with an increase in the temperature from 1100 °C to 1400 °C. The phase composition transformation was specifically [...] Read more.
Coal-based reduction and magnetic separation behavior of low-grade vanadium-titanium magnetite pellets were studied in this paper. It is found that the metallization degree increased obviously with an increase in the temperature from 1100 °C to 1400 °C. The phase composition transformation was specifically analyzed with X-ray diffraction (XRD). The microscopic examination was carried out with scanning electron microscopy (SEM), and the element composition and distribution were detected with energy dispersive spectroscopy (EDS). It is observed that the amounts of metallic iron particles obviously increased and the accumulation and growing tendency were gradually facilitated with the increase in the temperature from 1100 °C to 1400 °C. It is also found that the titanium oxides were gradually reduced and separated from ferrum-titanium oxides during reduction. In addition, with increasing the temperature from 1200 °C to 1350 °C, silicate phases, especially calcium silicate phases that were transformed from calcium ferrite at 1100 °C, were observed and gradually aggregated. However, at 1400 °C some silicate phases infiltrated into metallic iron, as it appears that the carbides, especially TiC, could probably contribute to the sintering phenomenon becoming serious. The transformation behavior of valuable elements was as follows: Fe2VO4 → VO → V → VC; FeTiO3 (→ FeTi2O5) → TiO2 → TiC; FeCr2O4 → Cr → CrC; FeTiO3 (→ FeTi2O5) → Fe0.5Mg0.5Ti2O5; (Fe3O4/FeTiO3→) FeO → Mg0.77Fe0.23O. Through the magnetic separation of coal-based reduced products, it is demonstrated that the separation of Cr, V, Ti, and non-magnetic phases can be preliminarily realized. Full article
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