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Minerals, Volume 11, Issue 8 (August 2021) – 123 articles

Cover Story (view full-size image): Carbonate skeletonized organisms such as bryozoans, mollusks, echinoderms, cnidarians, barnacles, serpulids, foraminifers, ostracods, and red algae occur in Antarctic marine biota today. Depending on the different carbonate polymorphs secreted and postmortem circumstances, their skeletal remains play a major role in reconstructions of former benthic environments. Information on Antarctic marine carbonates is, however, exiguous, especially regarding deep-sea habitats, generating a taphonomic bias in paleoecological reconstructions and entangling predictions on their fate in the face of climate change. Evidence on the current situation of living Antarctic carbonate factories represents a baseline to monitoring future effects of progressive ocean acidification and global warming. View this paper
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15 pages, 10985 KiB  
Article
The Role of Calcite Dissolution and Halite Thermal Expansion as Secondary Salt Weathering Mechanisms of Calcite-Bearing Rocks in Marine Environments
by Javier Martínez-Martínez, Anna Arizzi and David Benavente
Minerals 2021, 11(8), 911; https://doi.org/10.3390/min11080911 - 23 Aug 2021
Cited by 7 | Viewed by 2179
Abstract
This research focuses on the analysis of the influence of two secondary salt weathering processes on the durability of rocks exposed to marine environments: chemical dissolution of rock forming minerals and differential thermal expansion between halite and the hosting rock. These processes are [...] Read more.
This research focuses on the analysis of the influence of two secondary salt weathering processes on the durability of rocks exposed to marine environments: chemical dissolution of rock forming minerals and differential thermal expansion between halite and the hosting rock. These processes are scarcely treated in research compared to salt crystallisation. The methodology followed in this paper includes both in situ rock weathering monitoring and laboratory simulations. Four different calcite-bearing rocks (a marble, a microcrystalline limestone and two different calcarenites) were exposed during a year to a marine semiarid environment. Exposed samples show grain detachment, crystal edge corrosion, halite efflorescences and microfissuring. Crystal edge corrosion was also observed after the laboratory simulation during a brine immersion test. Calcite chemical dissolution causes a negligible porosity increase in all the studied rocks, but a significant modification of their pore size distribution. Laboratory simulations also demonstrate the deterioration of salt-saturated rocks during thermal cycles in climatic cabinet. Sharp differences between the linear thermal expansion of both a pure halite crystal and the different studied rocks justify the registered weight loss during the thermal cycles. The feedback between the chemical dissolution and differential thermal expansion, and the salt crystallisation of halite, contribute actively to the rock decay in marine environments. Full article
(This article belongs to the Special Issue 10th Anniversary of Minerals: Frontiers of Mineral Science)
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16 pages, 17908 KiB  
Article
Decoupling of Sr-Nd Isotopic Composition Induced by Potassic Alteration in the Shapinggou Porphyry Mo Deposit of the Qinling–Dabie Orogenic Belt, China
by Jun He, Xiaochun Xu, Zhongyang Fu, Yuhua An, Tianhu Chen, Qiaoqin Xie and Fukun Chen
Minerals 2021, 11(8), 910; https://doi.org/10.3390/min11080910 - 23 Aug 2021
Viewed by 1770
Abstract
In our previous study on petrogenesis of quartz syenite and granite porphyry, the host rocks of the Late Mesozoic Shapinggou Mo deposit in the Qinling–Dabie orogenic belt, we found that the initial Sr isotopic composition of the host rocks is strongly affected by [...] Read more.
In our previous study on petrogenesis of quartz syenite and granite porphyry, the host rocks of the Late Mesozoic Shapinggou Mo deposit in the Qinling–Dabie orogenic belt, we found that the initial Sr isotopic composition of the host rocks is strongly affected by the degree of K-alteration. Here, we provide further isotopic evidence of the host rocks and their minerals to investigate the geochemical behaviour of trace elements and isotopes during the alteration and to explain the phenomenon of decoupling of Sr–Nd isotopic composition. The quartz syenite and granite porphyry are altered by K-alteration in varying degrees and have high K2O and Rb contents and low Na2O, CaO, Sr, and Ba contents. Rock samples of both quartz syenite and granite porphyry have variable Rb/Sr ratios and initial 87Sr/86Sr values (even < 0.70) but contain quite homogeneous εNd(t) values (−12.8 to −14.8). Minerals from the rocks of moderate to intense K-alteration have very low initial 87Sr/86Sr values (even < −17), while those from the weakly altered rocks have 87Sr/86Sr(t) values of 0.7044 to 0.7084. The same phenomenon of the decoupling in Sr–Nd isotopic composition can be observed from several Mo deposits within the eastern Qinling–Dabie orogenic belt. This fact suggests similar hydrothermal features and a comparable origin for both the magmatic rocks and hydrothermal fluids in this belt. A comparison between porphyry Mo and porphyry Cu deposits shows that elements and the Rb–Sr isotope system have different behaviours during the K-alteration, implying distinct material sources and igneous rocks for porphyry Mo and porphyry Cu deposits, respectively. Full article
(This article belongs to the Section Mineral Deposits)
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21 pages, 4582 KiB  
Article
Geochemical Characterization of the Eocene Coal-Bearing Source Rocks, Xihu Sag, East China Sea Shelf Basin, China: Implications for Origin and Depositional Environment of Organic Matter and Hydrocarbon Potential
by Xiong Cheng, Dujie Hou, Xinhuai Zhou, Jinshui Liu, Hui Diao and Lin Wei
Minerals 2021, 11(8), 909; https://doi.org/10.3390/min11080909 - 23 Aug 2021
Cited by 3 | Viewed by 2699
Abstract
Eocene coal-bearing source rocks of the Pinghu Formation from the W-3 well in the western margin of the Xihu Sag, East China Sea Shelf Basin were analyzed using Rock-Eval pyrolysis and gas chromatography–mass spectrometry to investigate the samples’ source of organic matter, depositional [...] Read more.
Eocene coal-bearing source rocks of the Pinghu Formation from the W-3 well in the western margin of the Xihu Sag, East China Sea Shelf Basin were analyzed using Rock-Eval pyrolysis and gas chromatography–mass spectrometry to investigate the samples’ source of organic matter, depositional environment, thermal maturity, and hydrocarbon generative potential. The distribution patterns of n-alkanes, isoprenoids and steranes, high Pr/Ph ratios, abundant diterpanes, and the presence of non-hopanoid triterpanes indicate predominant source input from higher land plants. The contribution of aquatic organic matter was occasionally slightly elevated probably due to a raised water table. High hopane/sterane ratios and the occurrence of bicyclic sesquiterpanes and A-ring degraded triterpanes suggest microbial activity and the input of microbial organisms. Overwhelming predominance of gymnosperm-derived diterpanes over angiosperm-derived triterpanes suggest a domination of gymnosperms over angiosperms in local palaeovegetation during the period of deposition. The high Pr/Ph ratios, the plot of Pr/n-C17 versus Ph/n-C18, the almost complete absence of gammacerane, and the distribution pattern of hopanes suggest that the samples were deposited in a relatively oxic environment. Generally, fluctuation of redox potential is coupled with source input, i.e., less oxic conditions were associated with more aquatic organic matter, suggesting an occasionally raised water table. Comprehensive maturity evaluation based on Ro, Tmax, and biomarker parameters shows that the samples constitute a natural maturation profile ranging from marginally mature to a near peak oil window. Hydrogen index and atomic H/C and O/C ratios of kerogens suggest that the samples mainly contain type II/III organic matter and could generate mixed oil and gas. Full article
(This article belongs to the Special Issue Sedimentology and Geochemistry of Organic Matter)
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17 pages, 57101 KiB  
Article
Geochemical State of Wilga River Environment in Kraków (Poland)—Historical Aspects and Existing Issues
by Magdalena Strzebońska and Anna Kostka
Minerals 2021, 11(8), 908; https://doi.org/10.3390/min11080908 - 22 Aug 2021
Cited by 5 | Viewed by 2275
Abstract
Aquatic systems are a very important part of the environment, which requires special attention due to the constant deterioration of the quality and quantity of water globally. Aquatic environments in Poland are mostly affected by the mining and smelting industry, which is especially [...] Read more.
Aquatic systems are a very important part of the environment, which requires special attention due to the constant deterioration of the quality and quantity of water globally. Aquatic environments in Poland are mostly affected by the mining and smelting industry, which is especially visible in the south of the country, and one of such anthropogenically affected rivers is the Wilga—a small tributary of the Vistula River (the biggest river in Poland). For many years, the catchment area of the Wilga River accommodated a functioning industry that was based on the use of metals (fur, leather processing, foundry and galvanizing plants), as well as the “Solvay” Kraków Soda Works, which have left behind soda waste piles, and currently, along the course of the river, there are ongoing works connected with the construction of the “Łagiewnicka Route”, which required the relocation of a section of the Wilga river bed, among other things. To determine the general condition of the river, selected physico-chemical parameters were analysed in the water (pH, conductivity, anions: Cl, N-NO3, P-PO4 and SO4 and cations: Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr and Zn), suspended particulate matter and sediment (Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr and Zn). Samples were taken before the relocation of the river bed (2019) and after its relocation (2021). The obtained data were compared with recorded historical data and this revealed that over the years, the condition of the Wilga environment has improved significantly, especially in terms of the contamination of sediments with metals, the concentrations of which fell several ten-fold. This is attributed to the closure of most industrial plants located within the river’s catchment area and to the modernization and legal regulation of the functioning of the remaining plants. An effect of leachates from the soda waste piles on the waters of Wilga has been observed (in the form of higher pH, mineralization and concentration of chlorides), which has however gradually decreased over time. However, no visible impact of road transport on the river’s environment has been observed, or any impact of the construction works or the related relocation of the river bed for that matter. The river should still be classified as polluted, but the level of this pollution has decreased significantly and the qualitative composition of the pollution has also changed. Full article
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25 pages, 7667 KiB  
Article
Interaction of Corroding Iron with Eight Bentonites in the Alternative Buffer Materials Field Experiment (ABM2)
by Paul Wersin, Jebril Hadi, Andreas Jenni, Daniel Svensson, Jean-Marc Grenèche, Patrik Sellin and Olivier X. Leupin
Minerals 2021, 11(8), 907; https://doi.org/10.3390/min11080907 - 22 Aug 2021
Cited by 11 | Viewed by 2521
Abstract
Bentonite, a common smectite-rich buffer material, is in direct contact with corroding steel in many high-level radioactive waste repository designs. The interaction of iron with the smectite-rich clay may affect its swelling and sealing properties by processes such as alteration, redox reactions and [...] Read more.
Bentonite, a common smectite-rich buffer material, is in direct contact with corroding steel in many high-level radioactive waste repository designs. The interaction of iron with the smectite-rich clay may affect its swelling and sealing properties by processes such as alteration, redox reactions and cementation. The chemical interactions were investigated by analysing the Fe/clay interfaces of eight bentonite blocks which had been exposed to temperatures up to 130 °C for five years in the ABM2 borehole at the Äspö Hard Rock Laboratory managed by the Swedish Nuclear Fuel and Waste Management Co (SKB). Eleven interface samples were characterised by high spatial resolution methods, including scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and μ-Raman spectroscopy as well as by “bulk” methods X-ray diffraction, X-ray fluorescence and 57Fe Mössbauer spectrometry. Corrosion induced an iron front of 5–20 mm into the bentonite, except for the high-Fe bentonite where no Fe increase was detected. This Fe front consisted mainly of ferric (oxyhydr)oxides in addition to the structural Fe in the smectite fraction which had been partially reduced by the interaction process. Fe(II) was also found to extend further into the clay, but its nature could not be identified. The consistent behaviour is explained by the redox evolution, which shifts from oxidising to reducing conditions during the experiment. No indication of smectite alteration was found. Full article
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24 pages, 8836 KiB  
Article
An Investigation of the Adsorption of Xanthate on Bornite in Aqueous Solutions Using an Atomic Force Microscope
by Jinhong Zhang
Minerals 2021, 11(8), 906; https://doi.org/10.3390/min11080906 - 21 Aug 2021
Cited by 2 | Viewed by 2657
Abstract
An atomic force microscope (AFM) was applied to study of the adsorption of xanthate on bornite surfaces in situ in aqueous solutions. AFM images showed that xanthate, i.e., potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX), adsorbed strongly on bornite, and the [...] Read more.
An atomic force microscope (AFM) was applied to study of the adsorption of xanthate on bornite surfaces in situ in aqueous solutions. AFM images showed that xanthate, i.e., potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX), adsorbed strongly on bornite, and the adsorbate bound strongly with the mineral surface without being removed by flushing with ethanol alcohol. The AFM images also showed that the adsorption increased with the increased collector concentration and contact time. Xanthate adsorbed on bornite in a similar manner when the solution pH changed to pH 10. The AFM force measurement results showed that the probe–substrate adhesion increased due to the adsorption of xanthate on bornite. The sharp “jump-in” and “jump-off” points on force curve suggest that the adsorbate is not “soft” in nature, ruling out the existence of dixanthogen, an oily substance. Finally, the ATR-FTIR (attenuated total reflection-Fourier-transform infrared) result confirms that the adsorbate on bornite in xanthate solutions is mainly in the form of insoluble cuprous xanthate (CuX) instead of dixanthogen. This xanthate/bornite adsorption mechanism is very similar to what is obtained with the xanthate/chalcocite system, while it is different from the xanthate/chalcopyrite system, for which oily dixanthogen is the main adsorption product on the chalcopyrite surface. The present study helps clarify the flotation mechanism of bornite in industry practice using xanthate as a collector. Full article
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12 pages, 1600 KiB  
Article
Testing the Capacity of Staphylococcus equorum for Calcium and Copper Removal through MICP Process
by Sebastián Sepúlveda, Carla Duarte-Nass, Mariella Rivas, Laura Azócar, Andrés Ramírez, Javiera Toledo-Alarcón, Leopoldo Gutiérrez, David Jeison and Álvaro Torres-Aravena
Minerals 2021, 11(8), 905; https://doi.org/10.3390/min11080905 - 21 Aug 2021
Cited by 14 | Viewed by 2816
Abstract
This research focused on the evaluation of the potential use of a soil-isolated bacteria, identified as Staphylococcus equorum, for microbial-induced calcite precipitation (MICP) and copper removal. Isolated bacteria were characterized considering growth rate, urease activity, calcium carbonate precipitation, copper tolerance as minimum [...] Read more.
This research focused on the evaluation of the potential use of a soil-isolated bacteria, identified as Staphylococcus equorum, for microbial-induced calcite precipitation (MICP) and copper removal. Isolated bacteria were characterized considering growth rate, urease activity, calcium carbonate precipitation, copper tolerance as minimum inhibitory concentration (MIC) and copper precipitation. Results were compared with Sporosarcina pasteurii, which is considered a model bacteria strain for MICP processes. The results indicated that the S. equorum strain had lower urease activity, calcium removal capacity and copper tolerance than the S. pasteurii strain. However, the culture conditions tested in this study did not consider the halophilic feature of the S. equorum, which could make it a promising bacterial strain to be applied in process water from mining operations when seawater is used as process water. On the other hand, copper removal was insufficient when applying any of the bacteria strains evaluated, most likely due to the formation of a copper–ammonia complex. Thus, the implementation of S. equorum for copper removal needs to be further studied, considering the optimization of culture conditions, which may promote better performance when considering calcium, copper or other metals precipitation. Full article
(This article belongs to the Special Issue Biomineralization Applied to Water Treatment)
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14 pages, 1981 KiB  
Article
Construction and Demolition Waste Recycling through Conventional Jig, Air Jig, and Sensor-Based Sorting: A Comparison
by Carlos Hoffmann Sampaio, Weslei Monteiro Ambrós, Bogdan Grigore Cazacliu, Josep Oliva Moncunill, Moacir Medeiros Veras, Gérson Luis Miltzarek, Luis F. O. Silva, Ariane Salvador Kuerten and Maria Alejandra Liendo
Minerals 2021, 11(8), 904; https://doi.org/10.3390/min11080904 - 21 Aug 2021
Cited by 14 | Viewed by 3587
Abstract
The paper presents a comparison of the concentration methods conventional jig, air jig, and sensor-based sorting to treat construction and demolition waste. All tests were made with concrete, brick, and gypsum particles and the tests aim to separate these materials into different size [...] Read more.
The paper presents a comparison of the concentration methods conventional jig, air jig, and sensor-based sorting to treat construction and demolition waste. All tests were made with concrete, brick, and gypsum particles and the tests aim to separate these materials into different size ranges, depending on the method. The equipment tested, conventional jig, air jig, and sensor-based sorting present good results to concentrate construction and demolition waste particles, with different concentrations and mass recoveries. The results show particularly good mass recoveries and particle concentration for conventional jig, especially for concrete and gypsum particles. Sensor-based sorting should preferably use concentration circuits for best results. Full article
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22 pages, 11554 KiB  
Article
Mineralogy and Geochemistry of Seabed Sediments of the Chiloé–Taitao Area, Southern Chile, and Implications for Ore Deposits
by Marisol Pérez, Marcelo García, Brian Townley and Katja Deckart
Minerals 2021, 11(8), 903; https://doi.org/10.3390/min11080903 - 21 Aug 2021
Cited by 1 | Viewed by 3084
Abstract
The oceanic seabed contains a variety of mineral resources related exclusively to submarine environments. Limited information has been documented for the seabed offshore of Chile, which is particularly interesting due to its geodynamic context and large area. Mineralogical and geochemical analyses of 16 [...] Read more.
The oceanic seabed contains a variety of mineral resources related exclusively to submarine environments. Limited information has been documented for the seabed offshore of Chile, which is particularly interesting due to its geodynamic context and large area. Mineralogical and geochemical analyses of 16 sites within the Chiloé–Taitao area, from 83 to 3388 m in depth, were carried out. The most abundant minerals are quartz, feldspars, pyroxenes, amphiboles, epidote, and biotite, with lower quantities of zircon, white mica, olivine, pyrite, magnetite, ilmenite, and hematite. Framboidal pyrites are mainly present at >900 m depth, and could be associated with methane hydrates, which have been reported in the area and its surroundings. Tenorite, sphalerite, tennantite, cordierite, birnessite, and tellurobismuthite were revealed by XRD analysis at low concentrations but at many sites. Birnessite, a Fe–Mn nodule-forming mineral, was widely detected, and Pearson correlations showed elemental associations related to the presence of Mn oxides. Samples did not evidence Fe–Mn nodules, probably due to the redox and depth conditions. Nonetheless, it is probable that to the west, polymetallic nodules are present in deeper zones. In the southern part of the area, reflective grains were identified, with up to 58.3 wt.% Cu; these grains might be derived from the continent or formed by in situ diagenetic precipitation. Full article
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4 pages, 205 KiB  
Editorial
Editorial for Special Issue “Novel and Emerging Strategies for Sustainable Mine Tailings and Acid Mine Drainage Management”
by Carlito Baltazar Tabelin, Kyoungkeun Yoo and Jining Li
Minerals 2021, 11(8), 902; https://doi.org/10.3390/min11080902 - 20 Aug 2021
Cited by 2 | Viewed by 2044
Abstract
Climate change is one of the most pressing problems facing humanity this century [...] Full article
13 pages, 3259 KiB  
Article
Evaluation of Dispersion of Lead-Bearing Mine Wastes in Kabwe District, Zambia
by Shinsaku Nakamura, Toshifumi Igarashi, Yoshitaka Uchida, Mayumi Ito, Kazuyo Hirose, Tsutomu Sato, Walubita Mufalo, Meki Chirwa, Imasiku Nyambe, Hokuto Nakata, Shouta Nakayama and Mayumi Ishizuka
Minerals 2021, 11(8), 901; https://doi.org/10.3390/min11080901 - 20 Aug 2021
Cited by 6 | Viewed by 2506
Abstract
Dispersion of lead (Pb) in mine wastes was simulated for reproducing Pb contamination of soil in Kabwe District, Zambia. Local weather data of year 2019 were monitored in situ and used for the simulations. The plume model, weak puff model, and no puff [...] Read more.
Dispersion of lead (Pb) in mine wastes was simulated for reproducing Pb contamination of soil in Kabwe District, Zambia. Local weather data of year 2019 were monitored in situ and used for the simulations. The plume model, weak puff model, and no puff model were adopted for calculation of Pb dispersion under different wind conditions. The results showed that Pb dispersion from the Kabwe mine was directly affected by wind directions and speeds in the dry season, although it was not appreciably affected in the rainy season. This may be because the source strength is lower in the rainy season due to higher water content of the surface. This indicates that Pb dispersion patterns depend on the season. In addition, the distribution of the amount of deposited Pb-bearing soils around the mine corresponded to the distribution of Pb contents in soils. These results suggest that Pb contamination in soils primarily results from dispersion of fine mine wastes. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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22 pages, 5648 KiB  
Article
Petrography and Shock Metamorphism of the Lunar Breccia Meteorite NWA 13120
by Zhipeng Xia, Bingkui Miao, Chuantong Zhang, Hongyi Chen, Lanfang Xie, P. M. Ranjith, Yikai Zhang and Bowen Si
Minerals 2021, 11(8), 899; https://doi.org/10.3390/min11080899 - 20 Aug 2021
Cited by 1 | Viewed by 3514
Abstract
Lunar meteorites are the fragments of rocks that fell on Earth because of the impacts of asteroids on the Moon. Such rocks preserve information about the composition, evolutionary process, and shock history of the lunar surface. NWA 13120 is a recently discovered lunar [...] Read more.
Lunar meteorites are the fragments of rocks that fell on Earth because of the impacts of asteroids on the Moon. Such rocks preserve information about the composition, evolutionary process, and shock history of the lunar surface. NWA 13120 is a recently discovered lunar breccia meteorite having features of strong shock, which is composed of lithic and mineral clasts in a matrix of very fine-grained (<10 μm) and recrystallized olivine-plagioclase with a poikilitic-like texture. As the most abundant lithic clasts, the crystalline impact melt (CIM) clasts can be divided into four types according to their texture and mineral composition: (1) anorthosites or troctolitic anorthosite with a poikilitic-like texture, but the mineral content is different from that of the matrix; (2) anorthosites containing basaltic fragments and rich in vesicles; (3) troctolitic anorthosite containing metamorphic olivine mineral fragments; (4) troctolitic anorthosite containing troctolite fragments. Based on the petrology and mineralogy, NWA 13120 is a lunar meteorite that was derived from the ferrous anorthosite suite (FANs) of the lunar highlands, while its texture suggests it is a crystalline impact melt breccia. In addition, we infer that the parent rock of NWA 13120 is a lunar regolith breccia enriched in glass fragments. During the shock process, at pressures of more than 20 GPa, all plagioclase fragments were transformed into maskelynites, and olivine fragments occurred metamorphism. The post-shock temperature led to the partial melting of the basaltic fragments. Subsequently, all glass with diverse components in the parent rock were devitrified and recrystallized, forming the common olivine-plagioclase poikilitic-like texture and different CIM clasts. Meanwhile, the devitrification of maskelynite formed the accumulation of a large number of plagioclase microcrystals. Therefore, NWA 13120 is a meteorite of great significance for understanding the local shock metamorphism of lunar rocks on the lunar surface. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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19 pages, 5149 KiB  
Article
Interpreting the Chemical Variability of Iron Smelting Slag: A Case Study from Northeastern Madagascar
by Mélissa Morel and Vincent Serneels
Minerals 2021, 11(8), 900; https://doi.org/10.3390/min11080900 - 19 Aug 2021
Cited by 4 | Viewed by 3043
Abstract
The archaeological remains of a metallurgical workshop were excavated at Amboronala (northeast of Madagascar/1000–1200 CE). The bulk mineralogical (X-ray Diffraction) and chemical (X-ray Fluorescence) data on ores, building materials, and slag are used to carry out a mass balance calculation. The results show [...] Read more.
The archaeological remains of a metallurgical workshop were excavated at Amboronala (northeast of Madagascar/1000–1200 CE). The bulk mineralogical (X-ray Diffraction) and chemical (X-ray Fluorescence) data on ores, building materials, and slag are used to carry out a mass balance calculation. The results show an important variability from one smelt to the other, reflecting a poorly controlled process. During each smelt, a given amount of building material contributes to the formation of the slag, and the conditions of reduction allow the extraction of a given amount of metal. These two main factors influence the composition of the slag independently and variably. This finding allows to make some inference on the origin of the technique and the organization of the production can be made. Full article
(This article belongs to the Special Issue Mineralogy, Trace Elements and Isotopic Tracers in Archaeometallurgy)
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19 pages, 3201 KiB  
Article
Elemental Enrichment in Shallow Subsurface Red Sea Coastal Sediments, Al-Shuaiba, Saudi Arabia: Natural vs. Anthropogenic Controls
by Ibrahim M. Ghandour and Mohammed H. Aljahdali
Minerals 2021, 11(8), 898; https://doi.org/10.3390/min11080898 - 19 Aug 2021
Cited by 3 | Viewed by 2219
Abstract
Geochemical analysis of the 23 sediment samples collected from a short (0.6 m long) core retrieved from the coastal creek that was previously connecting the northern and southern Al-Shuaiba Lagoons, Red Sea, Saudi Arabia, was accomplished to assess the elemental enrichment levels and [...] Read more.
Geochemical analysis of the 23 sediment samples collected from a short (0.6 m long) core retrieved from the coastal creek that was previously connecting the northern and southern Al-Shuaiba Lagoons, Red Sea, Saudi Arabia, was accomplished to assess the elemental enrichment levels and the natural and anthropogenic driving forces for this enrichment. Statistical analysis and upcore variation in elemental concentrations enabled subdivision of the core formally into three units, lower, middle, and upper. The enriched elements in the lower and middle units display poor to negative correlations with the enriched elements in the upper unit. The lower unit is enriched in elements (Mo, As, U, and Re) suggesting deposition under anoxic conditions, possibly related to the Medieval Climate Anomaly. The middle unit is enriched in the carbonate-related constituents (CaCO3, Ca, and Sr). The upper unit is enriched in elements that co-vary significantly with Al suggesting increased terrigenous supply associated with the construction of the road between the two lagoons. The enrichment of elements in the lower and middle units is naturally driven, whereas the enrichment of lithogenic elements in the upper unit, though of geogenic origin, is induced after the road construction. Full article
(This article belongs to the Special Issue Environment and Geochemistry of Sediments)
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21 pages, 22743 KiB  
Article
Effect of Fine Aggregate Particle Characteristics on Mechanical Properties of Fly Ash-Based Geopolymer Mortar
by Heng Li, Pengpeng Gao, Fang Xu, Tao Sun, Yu Zhou, Jing Zhu, Chao Peng and Juntao Lin
Minerals 2021, 11(8), 897; https://doi.org/10.3390/min11080897 - 19 Aug 2021
Cited by 15 | Viewed by 2999
Abstract
This research aimed to investigate the effect of fine aggregate particles on mechanical properties of fly ash-based geopolymer mortar. In this work, seven kinds of river sand particles were designed based on different fine aggregate characteristics. The fineness modulus was adopted to quantitatively [...] Read more.
This research aimed to investigate the effect of fine aggregate particles on mechanical properties of fly ash-based geopolymer mortar. In this work, seven kinds of river sand particles were designed based on different fine aggregate characteristics. The fineness modulus was adopted to quantitatively describe the gradation of sands. The fluidity, compressive, flexural, and tensile strengths of geopolymer mortar with different sand gradations were analyzed by laboratory tests. Furthermore, the composition and morphology of fly ash-based geopolymer mortar was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The reasonable gradation range and filling effect of sand were obtained. The results show that fluidity and compressive and flexural strengths of geopolymer mortar both improve with the increase of the fineness modulus, while specific surface area and voidage are opposite. The tensile strength of mortar largely lies on the interface properties between the geopolymer binder and fine aggregates. When the pass rate of the key sieving size 1.18 mm is 75–95%, the pass rate of the key sieving size 0.15 mm is 15–25%, the fineness modulus is 2.2–2.6 and the appropriate filling coefficient of geopolymer paste is around 1.0–1.15, the comprehensive performance of geopolymer mortar is the best. This research paper could provide a basis for the design of geopolymer mortar based on fly ash, and it is of great significance for its popularization and application. Full article
(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications)
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24 pages, 4216 KiB  
Article
Leaching of Ca-Rich Slags Produced from Reductive Smelting of Bauxite Residue with Na2CO3 Solutions for Alumina Extraction: Lab and Pilot Scale Experiments
by Michail Vafeias, Amalia Bempelou, Eirini Georgala, Panagiotis Davris, Efthymios Balomenos and Dimitrios Panias
Minerals 2021, 11(8), 896; https://doi.org/10.3390/min11080896 - 19 Aug 2021
Cited by 7 | Viewed by 2567
Abstract
Sustainable utilization of Bauxite Residue (BR) is currently one of the greatest challenges being tackled by the alumina industry, due to its high production rates and limited reuse options. The present work is concerned with the use of BR as a candidate metallurgical [...] Read more.
Sustainable utilization of Bauxite Residue (BR) is currently one of the greatest challenges being tackled by the alumina industry, due to its high production rates and limited reuse options. The present work is concerned with the use of BR as a candidate metallurgical raw material for iron (Fe) production and aluminum (Al) extraction. In more detail, at first, BR undergoes reductive smelting to extract its Fe content and produce a slag of mainly calcium aluminate composition. In a second step, Al contained in the calcium aluminate phases is extracted hydrometallurgically by leaching with a Na2CO3 aqueous solution. The focus of the current study is the optimization of this leaching process, and it was performed in two stages. The first was a laboratory scale investigation on the main parameters affecting the extraction rate of Al. The second stage was performed in pilot scale and incorporated observations and suggestions based on the laboratory scale investigation. Laboratory work showed that more than 50% of aluminum could be easily extracted in less than 1 h, in 5% S/L, at 70 °C and with an 20% excess of Na2CO3. Pilot scale work, by successfully applying the suggestions derived from laboratory scale work, achieved an average Al extraction of 68% from a 10% S/L pulp, with a slag of optimized composition in relation to the one used in the laboratory scale. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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19 pages, 9455 KiB  
Article
Towards Sustainability Pathway with Bio-Derived Platinum and Palladium Catalyst for Furfural Hydrogenation—A Novel Greener Approach in Catalysis
by Babatunde J. Akinbile, Leah C. Matsinha, Banothile C. E. Makhubela and Abayneh A. Ambushe
Minerals 2021, 11(8), 895; https://doi.org/10.3390/min11080895 - 19 Aug 2021
Cited by 4 | Viewed by 2445
Abstract
The use of living plants to recover precious metals with potential catalytic activity is still at the infant stage. In this study, selective hydrogenation of furfural to furfuryl alcohol using novel bio-ore catalysts recovered from the end stage of phytomining process is demonstrated. [...] Read more.
The use of living plants to recover precious metals with potential catalytic activity is still at the infant stage. In this study, selective hydrogenation of furfural to furfuryl alcohol using novel bio-ore catalysts recovered from the end stage of phytomining process is demonstrated. The phytomining process was carried out in the green house by artificially contaminating cassava (Manihot esculenta) plant with 500 mg/L palladium (Pd) and platinum (Pt) solutions for a period of eight weeks. After harvesting, concentrations of metals as high as 78 ± 0.047 and 1276 ± 0.036 µg/g of Pd and Pt, respectively, were detected in the calcinated root of cassava. The produced bio-ore catalysts; @PdCassCat and @PtCassCat were fully characterized with the following techniques: transmission electron microscopy (TEM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), powder X-ray diffraction (pXRD), N2-sorption, and UV-visible spectroscopy techniques and directly applied as catalysts for hydrogenation of furfural to furfuryl alcohol. The reaction was conducted under an optimized condition (furfural (10 mmol), triethylamine (Et3N) (10 mmol), formic acid (20 mmol), temperature (160 °C), catalyst amount (40 mg)) realizing a yield of 76.5% and 100% furfuryl alcohol using @PdCassCat and @PtCassCat, respectively. The catalytic activities of the @PdCassCat and @PtCassCat were excellent as well as recyclable up to four and five times, respectively. Full article
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14 pages, 964 KiB  
Article
Holistic Pre-Feasibility Study of Comminution Routes for a Brazilian Itabirite Ore
by Juliana Segura-Salazar, Natasha de S. L. Santos and Luís Marcelo Tavares
Minerals 2021, 11(8), 894; https://doi.org/10.3390/min11080894 - 18 Aug 2021
Cited by 5 | Viewed by 2845
Abstract
Comminution is an essential step in processing itabirite ores, given the need to liberate silica and other contaminants from the iron minerals for downstream concentration and then pellet feed production. In general, these ores in Brazil are not particularly hard to crush and [...] Read more.
Comminution is an essential step in processing itabirite ores, given the need to liberate silica and other contaminants from the iron minerals for downstream concentration and then pellet feed production. In general, these ores in Brazil are not particularly hard to crush and grind, but both capital (CAPEx) and operating (OPEx) expenditures in this stage of preparation can be critical for the project, in particular due to uncertainties in iron ore prices. Several circuits have been designed and are in operation for this type of ore in Brazil; however, it is not yet clear which technologies are more cost-effective and in which configuration they should be applied. This work critically analyzes four comminution circuits for an undisclosed case study. For these circuits, CAPEx, OPEx, and some environmental sustainability indices, as well as qualitative technical criteria, were used in the comparisons. This work concludes that two of these process routes, especially those based on more energy-efficient technologies (and one of these still rarely explored even at bench-scale), have demonstrated to be very attractive from multiple standpoints. Full article
(This article belongs to the Special Issue Process Optimization in Mineral Processing)
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19 pages, 5706 KiB  
Article
Research on Automatic Construction Method of Three-Dimensional Complex Fault Model
by Chi Zhang, Xiaolin Hou, Mao Pan and Zhaoliang Li
Minerals 2021, 11(8), 893; https://doi.org/10.3390/min11080893 - 18 Aug 2021
Cited by 3 | Viewed by 2002
Abstract
Three-dimensional complex fault modeling is an important research topic in three-dimensional geological structure modeling. The automatic construction of complex fault models has research significance and application value for basic geological theories, as well as engineering fields such as geological engineering, resource exploration, and [...] Read more.
Three-dimensional complex fault modeling is an important research topic in three-dimensional geological structure modeling. The automatic construction of complex fault models has research significance and application value for basic geological theories, as well as engineering fields such as geological engineering, resource exploration, and digital mines. Complex fault structures, especially complex fault networks with multilevel branches, still require a large amount of manual participation in the characterization of fault transfer relationships. This paper proposes an automatic construction method for a three-dimensional complex fault model, including the generation and optimization of fault surfaces, automatic determination of the contact relationship between fault surfaces, and recording of the model. This method realizes the automatic construction of a three-dimensional complex fault model, reduces the manual interaction in model construction, improves the automation of fault model construction, and saves manual modeling time. Full article
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17 pages, 5397 KiB  
Article
Controlled Hydrothermal Precipitation of Alunite and Natroalunite in High-Aluminum Vanadium-Bearing Aqueous System
by Luyao Wang, Nannan Xue, Yimin Zhang and Pengcheng Hu
Minerals 2021, 11(8), 892; https://doi.org/10.3390/min11080892 - 18 Aug 2021
Cited by 8 | Viewed by 2317
Abstract
During the acid leaching process of black shale, with the destruction of the aluminosilicate mineral structure, a large amount of aluminum (Al) is leached, accompanied by the release of vanadium (V). To separate aluminum from the vanadium-containing solution, the precipitation behavior of aluminum [...] Read more.
During the acid leaching process of black shale, with the destruction of the aluminosilicate mineral structure, a large amount of aluminum (Al) is leached, accompanied by the release of vanadium (V). To separate aluminum from the vanadium-containing solution, the precipitation behavior of aluminum ions (Al3+) was investigated under hydrothermal conditions with the formation of alunite and natroalunite. In the solution environment, alunite and natroalunite are able to form stably by the Al3+ hydrolysis precipitation process at a temperature of 200 °C, a pH value of 0.4 and a reaction time of 5 h. When Al3+ was precipitated at a K/Al molar ratio of 1, the aluminum precipitation efficiency and the vanadium precipitation efficiency were 64.77% and 1.72%, respectively. However, when Al3+ was precipitated at a Na/Al molar ratio of 1, the precipitation efficiency of the aluminum decreased to 48.71% and the vanadium precipitation efficiency increased to 4.36%. The thermodynamics and kinetics results showed that alunite forms more easily than natroalunite, and the reaction rate increases with increasing temperature, and the precipitation is controlled by the chemical reaction. Vanadium loss increases as the pH value increases. It can be deduced that the ion state of tetravalent vanadium (VO2+) was transformed into the ion state of pentavalent vanadium (VO2+) in the hydrothermal environment. The VO2+ can be adsorbed on the alunite or natroalunite as a result of their negative surface charges, ultimately leading to vanadium loss. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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18 pages, 10539 KiB  
Article
Seismic Data Interpretation and Identification of Hydrocarbon-Bearing Zones of Rajian Area, Pakistan
by Naveed Ahmad, Sikandar Khan, Eisha Fatima Noor, Zhihui Zou and Abdullatif Al-Shuhail
Minerals 2021, 11(8), 891; https://doi.org/10.3390/min11080891 - 18 Aug 2021
Cited by 4 | Viewed by 6690
Abstract
The present study interprets the subsurface structure of the Rajian area using seismic sections and the identification of hydrocarbon-bearing zones using petrophysical analysis. The Rajian area lies within the Upper Indus Basin in the southeast (SE) of the Salt Range Potwar Foreland Basin. [...] Read more.
The present study interprets the subsurface structure of the Rajian area using seismic sections and the identification of hydrocarbon-bearing zones using petrophysical analysis. The Rajian area lies within the Upper Indus Basin in the southeast (SE) of the Salt Range Potwar Foreland Basin. The marked horizons are identified using formation tops from two vertical wells. Seismic interpretation of the given 2D seismic data reveals that the study area has undergone severe distortion illustrated by thrusts and back thrusts, forming a triangular zone within the subsurface. The final trend of those structures is northwest–southeast (NW–SE), indicating that the area is part of the compressional regime. The zones interpreted by the study of hydrocarbon potential include Sakessar limestone and Khewra sandstone. Due to the unavailability of a petrophysics log within the desired investigation depths, lithology cross-plots were used for the identification of two potential hydrocarbon-bearing zones in one well at depths of 3740–3835 m (zone 1) and 4015–4100 m (zone 2). The results show that zone 2 is almost devoid of hydrocarbons, while zone 1 has an average hydrocarbon saturation of about 11%. Full article
(This article belongs to the Special Issue Studies of Seismic Reservoir Characterization)
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28 pages, 50476 KiB  
Article
Comparison between Siliceous Concretions from the Ionian Basin and the Apulian Platform Margins (Pre-Apulian Zone), Western Greece: Implication of Differential Diagenesis on Nodules Evolution
by Nicolina Bourli, Maria Kokkaliari, Nikolaos Dimopoulos, Ioannis Iliopoulos, Elena Zoumpouli, George Iliopoulos and Avraam Zelilidis
Minerals 2021, 11(8), 890; https://doi.org/10.3390/min11080890 - 18 Aug 2021
Cited by 7 | Viewed by 2920
Abstract
Siliceous concretions (nodules), from two different geological settings—the Apulian platform margins in Kefalonia island, and the Ionian Basin in Ithaca, Atokos, and Kastos islands—have been studied both in the field and in the laboratory. Nodule cuttings are mainly characterized by the development of [...] Read more.
Siliceous concretions (nodules), from two different geological settings—the Apulian platform margins in Kefalonia island, and the Ionian Basin in Ithaca, Atokos, and Kastos islands—have been studied both in the field and in the laboratory. Nodule cuttings are mainly characterized by the development of a core, around which a ring (rim) has been formed. Mineralogical study, using X-ray powder diffraction (XRPD) analysis, showed that the rim is usually richer in moganite than the core. Homogeneous concretions, without discernible inner core and outer ring, were observed generally in both settings. Mineralogical analysis of the selected siliceous concretions from Kefalonia island showed the presence mostly of quartz and moganite, while calcite either was absent or participated in a few samples in minor/trace abundances. Moganite was generally abundant in all the samples from Kefalonia island. Concretions from the Ionian Basin showed a variation in the quartz, moganite, and calcite contents. Mineralogical differences were recognized both between the different studied geodynamic settings and internally in the same setting, but with different stages of development. The above-mentioned differential diagenesis on nodules evolution could be related to the presence and/or abundance of stylolites, later fluid flows, restrictions from one area to another due to synchronous fault activity, and the composition of substances dissolved in fluids. Moreover, the development of concretions produced secondary fractures in the surrounding area of the nodule-bearing rocks. Full article
(This article belongs to the Special Issue The Mineralogy of the Siliceous Concretions)
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22 pages, 12878 KiB  
Article
Dynamic Properties of Thermal Shock Treated Sandstone Subjected to Coupled Dynamic and Static Loads
by Xiang Li, Si Huang, Tubing Yin, Xibing Li, Kang Peng, Xiaodong Fan, Wengang Dang and Linchong Huang
Minerals 2021, 11(8), 889; https://doi.org/10.3390/min11080889 - 18 Aug 2021
Cited by 7 | Viewed by 2169
Abstract
In deep rock engineering, the rock mass can be subjected to thermal stress caused by sudden changes in temperature, which is referred to as thermal shock (TS). To study the effect of TS on heated sandstone, three cooling methods are used to provide [...] Read more.
In deep rock engineering, the rock mass can be subjected to thermal stress caused by sudden changes in temperature, which is referred to as thermal shock (TS). To study the effect of TS on heated sandstone, three cooling methods are used to provide different cooling rates. Then the coupled dynamic and static loading tests are carried out on the heated sandstone by means of a modified split Hopkinson pressure bar (SHPB) system. The test results show that as the heating level increases, the dry density, P-wave velocity, and the dynamic combined strength of the heated sandstone decrease, while specimen porosity increases. Particularly, a sharp change in the physical properties of sandstone can be observed at 650 °C, which is believed to be caused by the α-β transition of quartz at 573 °C. At each heating level of the test, the damage caused by the higher cooling rate to the heated sandstone is more than that caused by the lower cooling rate. The different failure modes of sandstone with increasing temperature are analyzed. The mechanism of TS acting on heated sandstone is discussed, and two typical fracture patterns reflecting the action of TS are identified through SEM. Full article
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22 pages, 4262 KiB  
Article
Periodically Released Magmatic Fluids Create a Texture of Unidirectional Solidification (UST) in Ore-Forming Granite: A Fluid and Melt Inclusion Study of W-Mo Forming Sannae-Eonyang Granite, Korea
by Jung Hun Seo, Yevgeniya Kim, Tongha Lee and Marcel Guillong
Minerals 2021, 11(8), 888; https://doi.org/10.3390/min11080888 - 18 Aug 2021
Cited by 6 | Viewed by 2875
Abstract
The Upper Cretaceous Sannae-Eonyang granite crystallized approximately 73 Ma and hosted the Sannae W-Mo deposit in the west and the Eonyang amethyst deposit in the east. The granite contained textural zones of miarolitic cavities and unidirectional solidification texture (UST) quartz. The UST rock [...] Read more.
The Upper Cretaceous Sannae-Eonyang granite crystallized approximately 73 Ma and hosted the Sannae W-Mo deposit in the west and the Eonyang amethyst deposit in the east. The granite contained textural zones of miarolitic cavities and unidirectional solidification texture (UST) quartz. The UST rock sampled in the Eonyang amethyst mine consisted of (1) early cavity-bearing aplitic granite, (2) co-crystallization of feldspars and quartz in a granophyric granite, and (3) the latest unidirectional growth of larger quartz crystals with clear zonation patterns. After the UST quartz was deposited, aplite or porphyritic granite was formed, repeating the prior sequence. Fluid and melt inclusions occurring in the UST quartz and quartz phenocrysts were sampled and studied to understand the magmatic-hydrothermal processes controlling UST formation and W-Mo mineralization in the granite. The composition of melt inclusions in the quartz phenocrysts suggested that the UST was formed by fractionated late-stage granite. Some of the melt inclusions occurring in the early-stage UST quartz were associated with aqueous inclusions, indicating fluid exsolution from a granitic melt. Hypersaline brine inclusions allowed the calculation of the minimum trapping pressure of 80–2300 bars. Such a highly fluctuating fluid pressure might be potentially due to a lithostatic-hydrostatic transition of pressure-attending fluid loss during UST formation. Highly fluctuating lithostatic-hydrostatic pressures created by fluid exsolution allowed shifting of the stability field from a quartz-feldspar cotectic to a single-phase quartz. The compositions of brine fluid assemblages hosted in the quartz phenocrysts deviated from the fluids trapped in the UST quartz, especially regarding the Rb/Sr and Fe/Mn ratios and W and Mo concentrations. The study of melt and fluid inclusions in the Eonyang UST sample showed that the exsolution of magmatic fluid was highly periodic. A single pulse of magmatic fluids of variable salinities/densities might have created a single UST sequence, and a new batch of magmatic fluid exsolution would be required to create the next UST sequence. Full article
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14 pages, 6420 KiB  
Article
Effects of Kaolin Additives in Fly Ash on Sintering and Properties of Mullite Ceramics
by Marta Valášková, Veronika Blahůšková and Jozef Vlček
Minerals 2021, 11(8), 887; https://doi.org/10.3390/min11080887 - 17 Aug 2021
Cited by 12 | Viewed by 2530
Abstract
The effective utilization of fly ash (FA) as a raw material for ceramics production is performed on the FA-kaolin mixtures containing kaolins 10% by mass. The mixtures in comparison with FA and three raw kaolins were annealed to mullite ceramics at temperatures of [...] Read more.
The effective utilization of fly ash (FA) as a raw material for ceramics production is performed on the FA-kaolin mixtures containing kaolins 10% by mass. The mixtures in comparison with FA and three raw kaolins were annealed to mullite ceramics at temperatures of 1000, 1100, 1200 and 1300 °C. The main aims were to contribute to the discussion on the effect of impurity of Na,K-feldspars in kaolins and Fe2O3 in FA on sintering procedure, porous ceramics properties and mullite structural properties. The phases were characterized using X-ray diffraction and thermogravimetry DTA/TGA methods. Mercury intrusion porosimetry was used for characterization of porosity of ceramic samples. Results evidenced the influence of feldspars in kaolins and Fe2O3 in FA on the sintering temperatures and properties of mullite ceramics. The fully FA-based ceramic sintered at 1100 °C exhibited post-sintering properties of bulk density 2.1 g/cm3; compressive strength 77.5 MPa; and porosity, 2% in comparison with the FA/kaolin-based ceramics properties of bulk density 2.2 g/cm3; compressive strength, 60–65 MPa; and porosity from 9.3 to 16.4% influenced by Na,K-feldspars. The best structural and mechanical characteristics were found for the FAK3 sample, supported by the high content of kaolinite and orthoclase in the kaolin K3 additive. The FAK3 annealed at 1100 °C exhibited good compressive strength of 87.6 MPa at a porosity of 10.6% and density of 2.24 g/cm3 and annealed at 1300 °C the compressive strength of 41.3 MPa at a porosity of 19.2% and density of 1.93 g/cm3. Full article
(This article belongs to the Special Issue Clay Minerals and Waste Fly Ash Ceramics)
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14 pages, 2694 KiB  
Article
Research on Strength Prediction Model and Microscopic Analysis of Mechanical Characteristics of Cemented Tailings Backfill under Fractal Theory
by Hongwei Deng, Tao Duan, Guanglin Tian, Yao Liu and Weiyou Zhang
Minerals 2021, 11(8), 886; https://doi.org/10.3390/min11080886 - 16 Aug 2021
Cited by 7 | Viewed by 1695
Abstract
In order to further study the internal relationship between the microscopic pore characteristics and macroscopic mechanical properties of cemented tailings backfill (CTB), in this study, mine tailings and ordinary Portland cement (PC32.5) were selected as aggregate and cementing materials, respectively, and different additives [...] Read more.
In order to further study the internal relationship between the microscopic pore characteristics and macroscopic mechanical properties of cemented tailings backfill (CTB), in this study, mine tailings and ordinary Portland cement (PC32.5) were selected as aggregate and cementing materials, respectively, and different additives (anionic polyacrylamide (APAM), lime and fly ash) were added to backfill samples with mass concentration of 74% and cement–sand ratios of 1:4, 1:6 and 1:8. After 28 days of curing, based on the uniaxial compressive strength test, nuclear magnetic resonance (NMR) porosity test and the fractal characteristics of pore structure, the relationships of the compressive strength with the proportion and fractal dimension of pores with different radii were analyzed. The uniaxial compressive strength prediction model of the CTB with the proportion of harmless pores and the fractal dimension of harmful pores as independent variables was established. The results show that the internal pores of the material are mainly the harmless and less harmful pores, and the sum of the average proportions of the two reaches 73.45%. Some characterization parameters of pore structure have a high correlation with the compressive strength. Among them, the correlation coefficients of compressive strength with the proportion of harmless pores and fractal dimension of harmful pores are 0.9219 and 0.9049, respectively. The regression results of the strength prediction model are significant, and the correlation coefficient is 0.9524. The predicted strength value is close to the actual strength value, and the predicted results are accurate and reliable. Full article
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14 pages, 2512 KiB  
Article
Vibrational and Thermodynamic Properties of Hydrous Iron-Bearing Lowermost Mantle Minerals
by Jiajun Jiang, Joshua M. R. Muir and Feiwu Zhang
Minerals 2021, 11(8), 885; https://doi.org/10.3390/min11080885 - 16 Aug 2021
Viewed by 2200
Abstract
The vibrational and thermodynamic properties of minerals are key to understanding the phase stability and the thermal structure of the Earth’s mantle. In this study, we modeled hydrous iron-bearing bridgmanite (Brg) and post-perovskite (PPv) with different [Fe3+-H] defect configurations using first-principles [...] Read more.
The vibrational and thermodynamic properties of minerals are key to understanding the phase stability and the thermal structure of the Earth’s mantle. In this study, we modeled hydrous iron-bearing bridgmanite (Brg) and post-perovskite (PPv) with different [Fe3+-H] defect configurations using first-principles calculations combined with quasi-harmonic approximations (QHA). Fe3+-H configurations can be vibrationally stable in Brg and PPv; the site occupancy of this defect will strongly affect its thermodynamic properties and particularly its response to pressure. The presence of Fe3+-H introduces distinctive high-frequency vibrations to the crystal. The frequency of these peaks is configuration dependence. Of the two defect configurations, [FeSi+OH·] makes large effects on the thermodynamic properties of Brg and PPv, whereas [VMg+FeMg·+OH·] has negligible effects. With an expected lower mantle water concentrations of <1000 wt. ppm the effect of Fe3+-H clusters on properties such as heat capacity and thermal expansion is negligible, but the effect on the Grüneisen parameter γ can be significant (~1.2%). This may imply that even a small amount of water may affect the anharmonicity of Fe3+-bearing MgSiO3 in lower mantle conditions and that when calculating the adiabaticity of the mantle, water concentrations need to be considered. Full article
(This article belongs to the Special Issue Minerals under Extreme Conditions)
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18 pages, 5690 KiB  
Article
Adsorption of Selected Heavy and Precious Metals from Simulated Wastewater Using Fabricated Polyacrylonitrile (PAN) and Poly(4-Vinylpyridine) (P4VP) Monoliths
by Keziah E. Liebenberg, Abayneh A. Ambushe and Orpah Zinyemba
Minerals 2021, 11(8), 884; https://doi.org/10.3390/min11080884 - 16 Aug 2021
Cited by 1 | Viewed by 1812
Abstract
Adsorption has become an attractive method for the extraction and recovery of metals from wastewater effluents. This study involved the fabrication of mesoporous neat polyacrylonitrile (PAN) monoliths and composite polymer monoliths of PAN and poly-4-vinylpyridine (P4VP) as adsorbents for toxic elements (As(V), Cr(VI)) [...] Read more.
Adsorption has become an attractive method for the extraction and recovery of metals from wastewater effluents. This study involved the fabrication of mesoporous neat polyacrylonitrile (PAN) monoliths and composite polymer monoliths of PAN and poly-4-vinylpyridine (P4VP) as adsorbents for toxic elements (As(V), Cr(VI)) and the recovery of PGMs(Ru(III), Rh(III), Pd(II)) from simulated wastewater solutions. Fabrication of the mesoporous polymer monoliths was conducted using the non-solvent induced phase separation method (NIPS). The monoliths were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer–Emmett–Teller (BET). Adsorption studies were conducted using crushed monoliths saturated in 1 mg·L−1 simulated wastewater solutions. Spectroscopic analyses of the resulting filtrates were conducted using inductively coupled plasma-optical emission spectrometry (ICP-OES). In this study, the NIPS method was successfully optimized and mesoporous PAN, as well as composite polymer monoliths, were successfully fabricated. A concentration of 1 mg·L−1 of Ru(III) and Pd(II) was completely adsorbed by both monoliths. The mesoporous composite polymer monoliths exhibited the highest adsorption capacity for Rh(III), As(V), and Cr(VI). The mesoporous polymer monoliths showed great potential for use as wastewater cleaning aids as well as remediators of precious metals. Full article
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21 pages, 5959 KiB  
Article
The Mechanisms Forming the Five–Floor Zonation of Quartz Veins: A Case Study in the Piaotang Tungsten–Tin Deposit, Southern China
by Xiangchong Liu, Wenlei Wang and Dehui Zhang
Minerals 2021, 11(8), 883; https://doi.org/10.3390/min11080883 - 16 Aug 2021
Cited by 6 | Viewed by 2711
Abstract
It is common among many vein–type tungsten deposits in southern China that the thickness of ore veins increases from <1 cm to >1 m with increasing depth. A five–floor zonation model for the vertical trend of vein morphology was proposed in the 1960s [...] Read more.
It is common among many vein–type tungsten deposits in southern China that the thickness of ore veins increases from <1 cm to >1 m with increasing depth. A five–floor zonation model for the vertical trend of vein morphology was proposed in the 1960s and has been widely applied for predicting ore bodies at deeper levels, but the causative mechanisms for such a zonation remain poorly understood. The Piaotang tungsten–tin deposit, one of the birthplaces of the five–floor zonation model, is chosen as a case study for deciphering the mechanisms forming its morphological zonation of quartz veins. The vertical trend of vein morphology and its link to the W–Sn mineralization in Piaotang was quantified by statistical distributions (Weibull distribution and power law distribution) of vein thickness and ore grade data (WO3 and Sn) from the levels of 676 m to 328 m. Then, the micro–scale growth history of quartz veins was reconstructed by scanning electron microscope–cathodoluminescence (SEM–CL) imaging and in situ trace element analysis. The Weibull modulus α of vein thickness increases with increasing depth, and the fractal dimensions of both vein thickness and ore grade data (WO3 and Sn) decrease with increasing depth. Their vertical changes indicate that the fractures that bear the thick veins were well connected, facilitating fluid focusing and mineralization in mechanically stronger host rocks. Three generations (Q1–Q3) of quartz were identified from CL images, and the CL intensity of quartz is possibly controlled by the concentrations of Al and temperature. From the relative abundance of the Q1–Q3 quartz at different levels, the vertical trend of vein morphology in Piaotang was initially produced during the hydrothermal event represented by Q1 and altered by later hydrothermal events represented by Q2 and Q3. Statistical distributions of vein thickness combined with SEM–CL imaging of quartz could be combined to evaluate the mineralization potential at deeper levels. Full article
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23 pages, 8890 KiB  
Article
Experimental Study on Mechanical Properties of Paste Backfill with Flue-Gas Desulphurisation Gypsum under Combined Action of Dry–Wet Cycles and Chloride Erosion
by Sheng Wang, Feng Wang, Dawei Yin, Tianqi Jiang and Zhen Zhang
Minerals 2021, 11(8), 882; https://doi.org/10.3390/min11080882 - 15 Aug 2021
Cited by 5 | Viewed by 1897
Abstract
Flue-gas desulphurisation gypsum—a solid waste from power plants—can be used to prepare paste backfill for reducing costs. Most paste backfills are exposed to dry–wet cycles and chloride salt-rich water in mines. Therefore, the mechanical properties and damage mechanisms of paste backfill with desulphurised [...] Read more.
Flue-gas desulphurisation gypsum—a solid waste from power plants—can be used to prepare paste backfill for reducing costs. Most paste backfills are exposed to dry–wet cycles and chloride salt-rich water in mines. Therefore, the mechanical properties and damage mechanisms of paste backfill with desulphurised gypsum under the coupling action of erosion due to chloride with different concentrations and dry–wet cycles were investigated using methods such as visual observation, mass measurement, uniaxial compression, acoustic emission, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and field-emission scanning electron microscopy. With an increasing number of dry–wet cycles, the mass, elastic modulus, and strength of the paste backfill exhibited the trend of increasing first and then decreasing. The failure mechanism changed from mainly vertical fractures to the alternating development of vertical and horizontal fractures. The surface denudation effect of the specimens in a solution with a higher concentration was more severe under the same number of dry–wet cycles. In this study, the laws governing the mass change, strength change, degree of surface denudation, and failure pattern of desulphurised gypsum-filled specimens under different concentrations of chloride salt and different numbers of dry–wet cycles were derived. Full article
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