Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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27 pages, 9168 KiB  
Article
A Multiphysics Model for the Near-Field Evolution of a Geological Repository of Radioactive Waste
by Uy Vo, Mamadou Fall, Julio Ángel Infante Sedano and Thanh Son Nguyen
Minerals 2023, 13(12), 1535; https://doi.org/10.3390/min13121535 - 10 Dec 2023
Viewed by 984
Abstract
The safety and robustness of Deep Geological Repositories (DGRs) are of paramount importance for the long-term management of spent nuclear fuel from electricity generation. The introduction of a multi-barrier system, which includes the host rock formation and an engineered barrier system (including the [...] Read more.
The safety and robustness of Deep Geological Repositories (DGRs) are of paramount importance for the long-term management of spent nuclear fuel from electricity generation. The introduction of a multi-barrier system, which includes the host rock formation and an engineered barrier system (including the bentonite buffer), has been a widely used approach to ensure the safety of DGRs. The assessment of the long-term safety of DGRs involves the mathematical modeling of the coupled thermal–hydraulic–mechanical–chemical (THMC) processes that occur in the near-field of the DGRs and their impact on the behaviour and engineering properties of the bentonite buffer. This paper presents a review of the THMC-coupled processes that arise in the bentonite buffer as well as a mathematical model governing such coupled processes. The model is verified against existing analytical solutions and validated against measured data of a thermal diffusion experiment in a sand bentonite column. Also, scoping analyses were performed to assess the influence of coupled THM processes on solute transport in clayrocks. The results of the numerical model closely matched those of the analytical solutions and experimental data demonstrating the capability of the provided mathematical model as well as the numerical approach in enhancing our comprehension of DGR behaviour. This enhanced comprehension will be valuable for safety prediction and assessment in the context of DGRs. The work presented in this paper is part of the Canadian Nuclear Safety Commission’s (CNSC) regulatory research to gain independent knowledge on the safety of the geological disposal of radioactive waste. Full article
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20 pages, 4412 KiB  
Article
Gas Barrier Properties of Multilayer Polymer–Clay Nanocomposite Films: A Multiscale Simulation Approach
by Andrey Knizhnik, Pavel Komarov, Boris Potapkin, Denis Shirabaykin, Alexander Sinitsa and Sergey Trepalin
Minerals 2023, 13(9), 1151; https://doi.org/10.3390/min13091151 - 30 Aug 2023
Viewed by 832
Abstract
The paper discusses the development of a multiscale computational model for predicting the permeability of multilayer protective films consisting of multiple polymeric and hybrid layers containing clay minerals as fillers. The presented approach combines three levels of computation: continuous, full atomic, and quantitative [...] Read more.
The paper discusses the development of a multiscale computational model for predicting the permeability of multilayer protective films consisting of multiple polymeric and hybrid layers containing clay minerals as fillers. The presented approach combines three levels of computation: continuous, full atomic, and quantitative structure–property correlations (QSPR). Oxygen and water are chosen as penetrant molecules. The main predictions are made using the continuum model, which takes into account the real scales of films and nanoparticles. It is shown that reliable predictions of the permeability coefficients can be obtained for oxygen molecules, which is not always possible for water. The latter requires the refinement of existing QSPR methods and interatomic interaction potentials for the atomistic level of calculations. Nevertheless, we show that the maximum effect on permeability reduction from the addition of clay fillers to the hybrid layer can be achieved by using nanoparticles with large aspect ratios and a high degree of orientational order. In addition, the use of the hybrid layer should be combined with the use of polymer layers with minimal oxygen and water permeability. The constructed model can be used to improve the properties of protective coatings for food and drug storage and to regulate the gas permeability of polymeric materials. Full article
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15 pages, 9202 KiB  
Article
Response of High Swelling Montmorillonite Clays with Aqueous Polymer
by Guru Prasad Panda, Alireza Bahrami, T. Vamsi Nagaraju and Haytham F. Isleem
Minerals 2023, 13(7), 933; https://doi.org/10.3390/min13070933 - 13 Jul 2023
Cited by 2 | Viewed by 1314
Abstract
Expansive clays containing mineral montmorillonite exhibit swelling and shrinkage due to variations in the moisture content, leading to significant distresses. There has been a growing interest in chemical and polymer additives treated for high swelling montmorillonite clays in recent years. However, limited attention [...] Read more.
Expansive clays containing mineral montmorillonite exhibit swelling and shrinkage due to variations in the moisture content, leading to significant distresses. There has been a growing interest in chemical and polymer additives treated for high swelling montmorillonite clays in recent years. However, limited attention has been paid to the effect of polyacrylamide on the soil’s swelling behavior. Moreover, nontraditional methods of the soil treatment are applied for the rapid stabilization of soil. In this article, polyacrylamide polymer is used as an additive to expansive clays to control the swelling phenomenon. Three different percentages—2.5%, 5%, and 7.5%—of polymer are blended with oven-dried soil to determine Atterberg limits, compaction features, and swelling characteristics. Additionally, electrical impedance measurement is conducted on treated soil samples with different moisture contents. The electrical resistance of soils and polymer-treated soils is measured based on the electrical resistivity correlation of soils. Tests results for soils stabilized with polyacrylamide show that swelling is significantly reduced with increasing the additive content. Moreover, the addition of polymer improves resistivity of soil. Aqueous polyacrylamide can be utilized as an effective stabilization additive to enhance properties of expansive clays. Full article
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14 pages, 5951 KiB  
Article
Melting Behaviour under Pressure of Kaolinite Clay: A Nanoscale Study
by Brahim Khalil Benazzouz and Ali Zaoui
Minerals 2023, 13(5), 679; https://doi.org/10.3390/min13050679 - 16 May 2023
Cited by 2 | Viewed by 1094
Abstract
In this study, the curves of variation of melting temperature as a function of pressure were determined for pressures up to 20 GPa using molecular dynamics (MD) calculations. The CLAYFF force field is used for the simulated PT curve of the clay kaolinite [...] Read more.
In this study, the curves of variation of melting temperature as a function of pressure were determined for pressures up to 20 GPa using molecular dynamics (MD) calculations. The CLAYFF force field is used for the simulated PT curve of the clay kaolinite structure. For this purpose, we have adopted the Z-method to determine the melting point (Tm) and superheat limit temperature (TLS) for different densities in kaolinite clay. In addition, various quantities, such as the radial distribution function (RDF), the mean square displacement (MSD), and the diffusion coefficient were evaluated in order to ensure the solid behaviour at the superheat limit temperature and the liquid behaviour at the melting point for the equilibrated structure of kaolinite. Full article
(This article belongs to the Special Issue Feature Papers in Clays and Engineered Mineral Materials)
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21 pages, 4470 KiB  
Article
Surfactant Intercalation in Li-Al-Based Binary and Ternary Layered Double Hydroxides by the Microwave-Assisted Rapid Ion-Exchange Process and Its Application in Iodine Adsorption
by Dileep Kumar Yadav, Sitharaman Uma and Rajamani Nagarajan
Minerals 2023, 13(3), 303; https://doi.org/10.3390/min13030303 - 21 Feb 2023
Cited by 2 | Viewed by 1260
Abstract
Recognizing the extreme speeds of reactions with microwaves, anionic forms of surfactants (sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS)) have been intercalated successfully by ion-exchange reactions in binary Li-Al and ternary Li-M-Al (M = Mg, Co, Ni, Cu, and Zn) layered double [...] Read more.
Recognizing the extreme speeds of reactions with microwaves, anionic forms of surfactants (sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS)) have been intercalated successfully by ion-exchange reactions in binary Li-Al and ternary Li-M-Al (M = Mg, Co, Ni, Cu, and Zn) layered double hydroxide (LDH) systems with the aid of microwaves. The samples have been characterized extensively. The basal spacings of 28.2 and 30.4 Å have been estimated for Li-Al-DS and Li-Al-DBS LDH samples, respectively, suggesting a perpendicular arrangement of DS and DBS anions in the interlayer space. The characteristic vibration bands of both LDH and the surfactant (DS and DBS) in the FTIR spectra confirmed the binding mode of surfactant molecules within the interlayers. DS-intercalated Li-Al LDH showed lower thermal stability than the DBS-intercalated sample. The nitrate-intercalated Li-M-Al (M = Mg, Co, Ni, Cu, and Zn) LDHs were ion-exchanged with SDS and SDBS to yield DS-and DBS-intercalated systems. The expanded basal spacings and a change in crystallite morphology confirmed the vertical intercalation of DS and DBS in Li-M-Al LDHs. ICP-AES and elemental analyses determined the metal contents and the surfactant content. FTIR spectra of intercalated samples confirmed the surfactant’s presence in the interlayer. The presence of Co, Ni, and Cu in Li-M-Al LDHs has been confirmed from UV-visible spectra. The Li-Al-DBS sample adsorbed iodine efficiently from methanol solutions, and the Langmuir model could explain the adsorption data in a better way. The adsorption followed pseudo-second-order kinetics. Full article
(This article belongs to the Section Clays and Engineered Mineral Materials)
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21 pages, 3515 KiB  
Review
Application of Clay Materials for Sorption of Radionuclides from Waste Solutions
by Bhupendra Kumar Singh and Wooyong Um
Minerals 2023, 13(2), 239; https://doi.org/10.3390/min13020239 - 08 Feb 2023
Cited by 6 | Viewed by 2109
Abstract
The wide application of nuclear resources in various fields has resulted in the production of radioactive waste, which poses a serious threat to lives and the environment. Nuclear waste contains long-lived radionuclides and, due to its mobility in environments, the proper management of [...] Read more.
The wide application of nuclear resources in various fields has resulted in the production of radioactive waste, which poses a serious threat to lives and the environment. Nuclear waste contains long-lived radionuclides and, due to its mobility in environments, the proper management of generated waste is necessary. To impede the mobility of radionuclides in environments, various materials have been tested as suitable sorbents under different experimental conditions. In this review, we thoroughly discuss some key and recent contributions to the application of natural clays (NCs) and modified/functionalized clays (MCs) for the sorption of various radionuclides in their cationic and anion forms from (simulated) waste solutions under different experimental conditions. More specifically, we discuss the key developments toward the use of natural clays for the efficient sorption of various radioactive contaminates. Later, this review targets the modification/functionalization of natural clays using various organic moieties to improve their removal capacities for various radionuclides/hazardous ions present in waste solutions. Finally, we summarize the major aspects and highlight the key challenges to be addressed in future studies to further enhance the application of clays and clay-based materials for selective and effective removal of various radionuclides from waste solutions. Full article
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31 pages, 8188 KiB  
Article
Investigating the Capabilities of Various Multispectral Remote Sensors Data to Map Mineral Prospectivity Based on Random Forest Predictive Model: A Case Study for Gold Deposits in Hamissana Area, NE Sudan
by Abdallah M. Mohamed Taha, Yantao Xi, Qingping He, Anqi Hu, Shuangqiao Wang and Xianbin Liu
Minerals 2023, 13(1), 49; https://doi.org/10.3390/min13010049 - 28 Dec 2022
Cited by 8 | Viewed by 2300
Abstract
Remote sensing data provide significant information about surface geological features, but they have not been fully investigated as a tool for delineating mineral prospective targets using the latest advancements in machine learning predictive modeling. In this study, besides available geological data (lithology, structure, [...] Read more.
Remote sensing data provide significant information about surface geological features, but they have not been fully investigated as a tool for delineating mineral prospective targets using the latest advancements in machine learning predictive modeling. In this study, besides available geological data (lithology, structure, lineaments), Landsat-8, Sentinel-2, and ASTER multispectral remote sensing data were processed to produce various predictor maps, which then formed four distinct datasets (namely Landsat-8, Sentinel-2, ASTER, and Data-integration). Remote sensing enhancement techniques, including band ratio (BR), principal component analysis (PCA), and minimum noise fraction (MNF), were applied to produce predictor maps related to hydrothermal alteration zones in Hamissana area, while geological-based predictor maps were derived from applying spatial analysis methods. These four datasets were used independently to train a random forest algorithm (RF), which was then employed to conduct data-driven gold mineral prospectivity modeling (MPM) of the study area and compare the capability of different datasets. The modeling results revealed that ASTER and Sentinel-2 datasets achieved very similar accuracy and outperformed Landsat-8 dataset. Based on the area under the ROC curve (AUC), both datasets had the same prediction accuracy of 0.875. However, ASTER dataset yielded the highest overall classification accuracy of 73%, which is 6% higher than Sentinel-2 and 13% higher than Landsat-8. By using the data-integration concept, the prediction accuracy increased by about 6% (AUC: 0.938) compared with the ASTER dataset. Hence, these results suggest that the framework of exploiting remote sensing data is promising and should be used as an alternative technique for MPM in case of data availability issues. Full article
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17 pages, 5133 KiB  
Article
Simple and Rapid Synthesis of Organically Modified Natural Acid Clay for the Adsorption of Anionic and Cationic Dyes
by Tomohiro Iwasaki
Minerals 2023, 13(1), 41; https://doi.org/10.3390/min13010041 - 27 Dec 2022
Cited by 5 | Viewed by 2345
Abstract
A simple method for organically modifying a natural acid clay (Japanese acid clay) rapidly with alkylamine has been developed. Japanese acid clay mainly consists of acidic montmorillonite and was successfully modified with decylamine in water at room temperature for a short time period [...] Read more.
A simple method for organically modifying a natural acid clay (Japanese acid clay) rapidly with alkylamine has been developed. Japanese acid clay mainly consists of acidic montmorillonite and was successfully modified with decylamine in water at room temperature for a short time period (10 min) using an ultrasonic bath without any pretreatments. The structure of the modified clay changed from exterior surface modification to intercalation with an increase in the decylamine content. The equilibrium adsorption capacity for the anionic dye methyl orange (MO) increased with increasing decylamine content. The adsorption kinetics and isotherm were well described by the pseudo-second-order and Langmuir models, respectively. Better MO adsorption was obtained under the conditions of high dosage, low pH value, and low temperature. The adsorbent was also found to have good adsorption for not only MO but also other anionic dyes (Congo red and eosin Y) and cationic dyes (methylene blue, crystal violet, and rhodamine B). In particular, the decylamine-intercalated clay adsorbent exhibited a high level of adsorption capacity for Congo red and crystal violet. The results demonstrate that the synthesis process can provide a simple and cost-effective organoclay as an adsorbent with high performance for the removal of anionic and cationic dyes. Full article
(This article belongs to the Special Issue Raw and Organically Modified Clays and Their Various Application)
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12 pages, 2665 KiB  
Article
The Earliest Generation of Diamond: The First Find of a Diamond Inclusion in Kimberlitic Olivine
by Lyudmila Pokhilenko, Nikolay Pokhilenko, Vladimir Malkovets and Taisia Alifirova
Minerals 2023, 13(1), 36; https://doi.org/10.3390/min13010036 - 26 Dec 2022
Viewed by 3840
Abstract
Today, it is known that the majority of diamonds are crystallized mostly from a metasomatic agent close in the main characteristics to carbonatite melts acting upon mantle rocks, and therefore, diamonds are located in the interstitial space of these rocks. So far, diamond [...] Read more.
Today, it is known that the majority of diamonds are crystallized mostly from a metasomatic agent close in the main characteristics to carbonatite melts acting upon mantle rocks, and therefore, diamonds are located in the interstitial space of these rocks. So far, diamond has never been found included in other kimberlitic or xenolithic minerals. We have found a diamond inclusion inside the kimberlitic olivine grain, which is the first find of its kind. The diamond crystal is to have been captured by the growing olivine at quite high temperatures (more than 1400 °C) early in the history of the cratonic lithospheric mantle formation. The event had taken place long before the depleted peridotite cooled down to the temperature of the Middle Archean cratonic geotherm corresponding to the diamond stability field at depths where carbonatite melts can react with depleted peridotite, making it a diamond-bearing rock. On the one hand, this find provides evidence that diamonds can crystallize from the high-temperature silicate melt with some carbonate component. On the other hand, the diamond was found coexisting with a sulfide inclusion in the same olivine, i.e., crystallization from a sulfide melt may be another way of diamond formation. Full article
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13 pages, 1672 KiB  
Review
Advances in Carbon Nanomaterial–Clay Nanocomposites for Diverse Applications
by Jayanta S. Boruah and Devasish Chowdhury
Minerals 2023, 13(1), 26; https://doi.org/10.3390/min13010026 - 23 Dec 2022
Cited by 3 | Viewed by 1691
Abstract
Clay materials are widely used in sheet-type platforms with peculiar characteristics and diverse applications. However, due to some disadvantages—such as weak mechanical strength and low reactivity—they are often subjected to modifications. Such tuning leads to better output than pure clay materials. This review [...] Read more.
Clay materials are widely used in sheet-type platforms with peculiar characteristics and diverse applications. However, due to some disadvantages—such as weak mechanical strength and low reactivity—they are often subjected to modifications. Such tuning leads to better output than pure clay materials. This review describes some of the clay hybrids in the form of nanocomposites with carbon nanomaterials. Generally, graphene oxide or its derivatives—such as reduced graphene oxide, carbon nanotubes, carbon dots, carbon nanoclusters, and polymeric components—have been utilized so far to make efficient clay composites that have applications such as catalysis, wastewater treatment for toxin removal, cargo delivery, stimulus-responsive advanced tools, optoelectronics, mechanically stable films for filtration, etc. It is interesting to note that nearly all of these applications tend to show the efficacy of modified clay nanocomposites as being significantly greater than that of pure clay, especially in terms of mechanical strength, loading capacity, increased surface area, and tunable functionality. According to the literature, the evidence proves the beneficial effects of these clay nanocomposites with carbon nanomaterials. Full article
(This article belongs to the Special Issue Recent Advances in Clay-Based Nanocomposites)
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23 pages, 60457 KiB  
Article
Multi-Dimensional Data Fusion for Mineral Prospectivity Mapping (MPM) Using Fuzzy-AHP Decision-Making Method, Kodegan-Basiran Region, East Iran
by Ali Shabani, Mansour Ziaii, Mehrdad Solimani Monfared, Adel Shirazy and Aref Shirazi
Minerals 2022, 12(12), 1629; https://doi.org/10.3390/min12121629 - 17 Dec 2022
Cited by 9 | Viewed by 1831
Abstract
Analyzing and fusing information layers of exploratory parameters is a crucial stride for increasing the accuracy of pinpointing mineral potential zones in the reconnaissance stage of mineral exploration. Remote sensing, geophysical, geochemical, and geology data were analyzed and fused for identify metallic mineralization [...] Read more.
Analyzing and fusing information layers of exploratory parameters is a crucial stride for increasing the accuracy of pinpointing mineral potential zones in the reconnaissance stage of mineral exploration. Remote sensing, geophysical, geochemical, and geology data were analyzed and fused for identify metallic mineralization in the Kodegan-Basiran region (East Iran). Landsat 7 Enhanced Thematic Mapper Plus (ETM+), aeromagnetic data, geological data, and geochemical stream sediment samples were utilized. The study area contains some copper indices and mines. Thus, the main focus of this study was identifying the zones with high potential for metallic copper mineralization. A two-stage methodology was implemented in this study: First, extraction of the exploratory parameters related to metallic mineralization and second is data fusion by the hybrid fuzzy-analytic hierarchy process (Fuzzy-AHP) method. Hydrothermal alterations and iron oxides in the area were mapped by applying the optimum index factor (OIF), band ratio (BR), and least squared fit (LS-Fit) to ETM+ data. Intrusive masses were positioned as one of the effective parameters in identifying metallic mineralization zones using the gradient tensor method to assess aeromagnetic data. In order to determine the threshold concentration and the location of mineralization anomalies, the K-means clustering algorithm, vertical geochemical zonality (Vz) index, as well as concentration-area (C-A) multi fractal and singularity analysis were implemented on the geochemical data. In conclusion, the potential zones of metallic mineralization in the Kodegan-Basiran region were displayed in a mineral prospectivity map (MPM) derived from the Fuzzy-AHP decision-making method. Finally, to validate the prospectivity map of metallic mineralization, a control area was selected and surveyed by collecting mineralogical, petrological, and stream sediment samples. Field works confirmed the mineralization of Cu and Fe sulfides, oxides, and hydroxides. The high potential areas identified in the MPM can be considered as targets for future Cu exploration in the Kodegan-Basiran area. Full article
(This article belongs to the Special Issue AI-Based GIS for Pinpointing Mineral Deposits)
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11 pages, 2341 KiB  
Article
In Situ Raman Spectroscopy and DFT Studies of the Phase Transition from Zircon to Reidite at High P–T Conditions
by Yue Gao, Zhi Zheng, Xia Zhao, Yuegao Liu, Jiangzhi Chen, Yan Li, Mengjun Xiong, Xiaotao Zu and Shenghua Mei
Minerals 2022, 12(12), 1618; https://doi.org/10.3390/min12121618 - 15 Dec 2022
Cited by 2 | Viewed by 1385
Abstract
Zircon (ZrSiO4) provides a good pressure-holding environment for ultra-high-pressure metamorphic minerals during crust exhumation due to its high incompressibility and chemical stability. At high pressure, the zircon can transform to reidite. Previous studies show much higher phase-transition pressures at room temperature [...] Read more.
Zircon (ZrSiO4) provides a good pressure-holding environment for ultra-high-pressure metamorphic minerals during crust exhumation due to its high incompressibility and chemical stability. At high pressure, the zircon can transform to reidite. Previous studies show much higher phase-transition pressures at room temperature than those at high temperature (>1000 K) due to kinetic hindrance. To further investigate the kinetics of the zircon–reidite phase transition at relatively low temperatures, the phase boundary at 298–800 K was determined using a diamond anvil cell combined with in situ Raman spectra. The results show that reidite becomes thermodynamically more stable compared with zircon at 8 GPa at room temperature, and the slope of the phase boundary at 298–800 K abruptly differs from that of previous studies at 1100–1900 K. Compared with the equilibrium phase boundary calculated by the density functional theory, it indicates that the kinetic effect of the zircon–reidite phase transition is obvious, and there exists a sufficiently large energy driving force provided by an overpressure to overcome the activation energy barrier below a critical temperature of approximately 880 K. The temperature dependence of overpressure is about 0.023 GPa/K. Full article
(This article belongs to the Special Issue High-Pressure Physical and Chemical Behaviors of Minerals and Rocks)
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17 pages, 2612 KiB  
Article
Comparative Life Cycle Assessment of Conventional and Dry Stack Tailings Disposal Schemes: A Case Study in Northern China
by Kun Wang, Zheng Zhang, Liyi Zhu, Xiuzhi Yang, Miao Chen and Chao Yang
Minerals 2022, 12(12), 1603; https://doi.org/10.3390/min12121603 - 14 Dec 2022
Cited by 2 | Viewed by 1523
Abstract
Alternative tailings disposal technologies can be effective solutions to mining waste safety and environmental problems. The current decision-making processes for tailings disposal schemes lack consideration of environmental impacts. Based on a case study of an open-pit iron mine in northern China, this study [...] Read more.
Alternative tailings disposal technologies can be effective solutions to mining waste safety and environmental problems. The current decision-making processes for tailings disposal schemes lack consideration of environmental impacts. Based on a case study of an open-pit iron mine in northern China, this study adopted the life cycle assessment (LCA) method to compare the environmental impacts of three tailings disposal schemes of conventional slurry disposal technology (CSDT), dry stack disposal technology (DSDT) by belt conveyance and DSDT by truck transport. The results indicated that (1) the environmental impacts of the CSDT scheme were lowest under the premise that water consumption was ignored; (2) the environmental impacts of the DSDT scheme by belt conveyance mainly originated from its transport process, indicating that the tailings storage facilities (TSFs) site planning could be crucial in design decision making; (3) the environmental impacts of the DSDT scheme by truck transport mainly originated from the energy consumption of dry stacking equipment; and (4) the DSDT scheme by truck transport was eventually found to be preferable and implemented in the case study, after comprehensively considering the LCA results, TSF safety and remaining capacity, and social and policy uncertainties. It is therefore recommended to conduct LCA of environmental impacts in the decision-making process for the sustainable design of TSFs. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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29 pages, 10190 KiB  
Article
Exploring Platinum Speciation with X-ray Absorption Spectroscopy under High-Energy Resolution Fluorescence Detection Mode
by Clément Laskar, Elena F. Bazarkina, Maria A. Kokh, Jean-Louis Hazemann, Stéphane Foulon, Olivier Leynaud, Elsa Desmaele and Gleb S. Pokrovski
Minerals 2022, 12(12), 1602; https://doi.org/10.3390/min12121602 - 13 Dec 2022
Cited by 1 | Viewed by 2613
Abstract
Critical to interpreting platinum chemical speciation using X-ray absorption spectroscopy (XAS) is the availability of reference spectra of compounds with known Pt redox and coordination. Here we compare different techniques for Pt LIII-edge X-ray absorption near edge structure (XANES) and extended [...] Read more.
Critical to interpreting platinum chemical speciation using X-ray absorption spectroscopy (XAS) is the availability of reference spectra of compounds with known Pt redox and coordination. Here we compare different techniques for Pt LIII-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectral regions for a large set of Pt-O-Cl-S reference compounds of known structures. The measurements were conducted in HERFD (high-energy resolution fluorescence detection, high-resolution or HR) mode, as well as in two conventional modes such as transmission (TR) and nominal-resolution total fluorescence yield (TFY or NR). Samples analyzed here included Pt0 (TR), PtIIS (HR), PtIVS2 (TR), K2PtIICl4 (HR + TR), K2PtIVCl6 (HR + TR), PtIVO2 (HR + TR), C6H12N2O4PtII (HR + TR), and aqueous solutions of K2PtIICl4 and H2PtIVCl6 (NR + TR), as well as (NH4)2PtIV(S5)3 (HR + TR). XANES spectra in HERFD mode offer a better energy resolution than in conventional modes, allowing a more accurate identification of Pt redox state and coordination geometry. EXAFS spectra in all three modes for a given compound yield identical within errors values of Pt-neighbor interatomic distances and mean square relative displacement (MSRD, σ2) parameters. In contrast, both TR and NR spectra on the one hand and HR spectra on the other hand yield distinct amplitude reduction factor (S02) values, 0.76 ± 0.04 and 0.99 ± 0.07 (1 standard error), respectively. This study contributes to the development of an open-access XAS database SSHADE. Full article
(This article belongs to the Special Issue Electron Microbeam and X-ray Techniques: Advances and Applications)
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12 pages, 1997 KiB  
Article
Chenowethite, Mg(H2O)6[(UO2)2(SO4)2(OH)2]·5H2O, a New Mineral with Uranyl-Sulfate Sheets from Red Canyon, Utah, USA
by Anthony R. Kampf, Jakub Plášil, Travis A. Olds, Chi Ma and Joe Marty
Minerals 2022, 12(12), 1594; https://doi.org/10.3390/min12121594 - 12 Dec 2022
Cited by 1 | Viewed by 1399
Abstract
The new mineral chenowethite, Mg(H2O)6[(UO2)2(SO4)2(OH)2]·5H2O, was found in efflorescence crusts on tunnel walls at the Blue Lizard, Green Lizard and Markey uranium mines in Red Canyon, San [...] Read more.
The new mineral chenowethite, Mg(H2O)6[(UO2)2(SO4)2(OH)2]·5H2O, was found in efflorescence crusts on tunnel walls at the Blue Lizard, Green Lizard and Markey uranium mines in Red Canyon, San Juan County, Utah, USA. The crystals are long, thin blades up to about 0.5 mm long, occurring in irregular sprays and subparallel groups. Chenowethite is pale green yellow. It has white streak, vitreous to silky luster, brittle tenacity, splintery and stepped fracture and two cleavages: {010} perfect and {001} good. It has a hardness (Mohs) of about 2 and is nonfluorescent in both long- and short-wave ultraviolet illumination. The density is 3.05(2) g/cm3. Optically, crystals are biaxial (−) with α = 1.530(2), β = 1.553(2) and γ = 1.565(2) (white light). The 2V is 72(2)° and dispersion is r > v (slight). The optical orientation is X = b, Y = a, Z = c and the mineral exhibits weak pleochroism in shades of pale green yellow: X < Y < Z. The Raman spectrum is consistent with the presence of UO22+, SO42− and OH/H2O. The empirical formula from electron microprobe analysis and arranged in accordance with the structure is (Mg0.71Fe2+0.09Co0.05Ni0.04)∑0.89(H2O)6[(UO2)2(SO4)2(OH)2]·[(H2O)4.78(NH4)0.22]∑5.00. Chenowethite is orthorhombic, space group Cmcm; the unit-cell parameters are a = 6.951(2), b = 19.053(6), c = 16.372(5) Å, V = 2168.19(7) Å3 and Z = 4. The crystal structure of chenowethite (R1 = 0.0396 for 912 I > 2σI reflections) contains [(UO2)2(SO4)2(OH)2]2− sheets that are topologically equivalent to those in deliensite, feynmanite, greenlizardite, johannite, meitnerite and plášilite. Full article
(This article belongs to the Special Issue The Crystal Chemistry and Mineralogy of Critical Metals)
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15 pages, 5848 KiB  
Article
Interaction between PEO and Kaolinite in Flocculating: An Experimental and Molecular-Simulation Study
by Xin Tian, Xiaomin Ma, Xianshu Dong, Yuping Fan, Ming Chang and Na Li
Minerals 2022, 12(12), 1585; https://doi.org/10.3390/min12121585 - 10 Dec 2022
Viewed by 1148
Abstract
In this paper, the flocculation properties of polyethylene oxide (PEO) on kaolinite and the mechanism of adsorption on kaolinite anisotropic substrates were explored. As revealed by the experimental results, the settling rate and removal rate of kaolinite increased with increasing PEO concentration, but [...] Read more.
In this paper, the flocculation properties of polyethylene oxide (PEO) on kaolinite and the mechanism of adsorption on kaolinite anisotropic substrates were explored. As revealed by the experimental results, the settling rate and removal rate of kaolinite increased with increasing PEO concentration, but too high PEO concentration would cause the small particles to stabilize and become difficult to settle. Furthermore, to probe deep into the interactions between PEO and kaolinite anisotropic substrates, the morphology of adsorbed PEO, interfacial adsorption structure, and dynamic behavior of water molecules were determined by quartz crystal microbalance with dissipation (QCM-D) and molecular dynamics (MD) simulations. The adsorption amount of PEO on different mineral surfaces is in the order of kaolinite > alumina > silica, and the thickness of the adsorption structure formed by alumina is greater than that of silica. As illustrated by the MD simulation results, the adsorption of PEO reduces the concentration of water molecules attached to the kaolinite surface. The PEO forms a double-layer adsorption structure on the 001 surface, while forming a tight monolayer adsorption structure on the 001¯ surface, weakening the interaction between the surface and the water molecules. The above results demonstrate that the adsorption of PEO effectively weakened the hydration dispersion of kaolinite and promoted the agglomeration of kaolinite particles. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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19 pages, 9012 KiB  
Article
Fusion of Multispectral Remote-Sensing Data through GIS-Based Overlay Method for Revealing Potential Areas of Hydrothermal Mineral Resources
by Saad S. Alarifi, Mohamed Abdelkareem, Fathy Abdalla, Ismail S. Abdelsadek, Hisham Gahlan, Ahmad. M. Al-Saleh and Mislat Alotaibi
Minerals 2022, 12(12), 1577; https://doi.org/10.3390/min12121577 - 09 Dec 2022
Cited by 9 | Viewed by 2281
Abstract
Revealing prospective locations of hydrothermal alteration zones (HAZs) is an important technique for mineral prospecting. In this study, we used multiple criteria inferred from Landsat-8 OLI, Sentinel-2, and ASTER data using a GIS-based weighted overlay multi-criteria decision analysis approach to build a model [...] Read more.
Revealing prospective locations of hydrothermal alteration zones (HAZs) is an important technique for mineral prospecting. In this study, we used multiple criteria inferred from Landsat-8 OLI, Sentinel-2, and ASTER data using a GIS-based weighted overlay multi-criteria decision analysis approach to build a model for the delineating of hydrothermal mineral deposits in the Khnaiguiyah district, Saudi Arabia. The utilized algorithms revealed argillic, phyllic, and propylitic alteration characteristics. The HAZs map resulted in the identification of six zones based on their mineralization potential, providing a basis for potential hydrothermal mineral deposit assessment exploration, which was created by the fusion of mineral bands indicators designated very low, low, moderate, good, very good, and excellent and covers 31.36, 28.22, 20.49, 10.99, 6.35, and 2.59%. Based on their potential for hydrothermal mineral potentiality, the discovered zones match gossans related to sulfide mineral alteration zones, as demonstrated by previous studies. Full article
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37 pages, 2914 KiB  
Review
The Role of Microorganisms in the Nucleation of Carbonates, Environmental Implications and Applications
by Ana Robles-Fernández, Camila Areias, Daniele Daffonchio, Volker C. Vahrenkamp and Mónica Sánchez-Román
Minerals 2022, 12(12), 1562; https://doi.org/10.3390/min12121562 - 03 Dec 2022
Cited by 14 | Viewed by 3217
Abstract
Microbially induced carbonate precipitation (MICP) is an important process in the synthesis of carbonate minerals, and thus, it is widely explored as a novel approach with potential for many technological applications. However, the processes and mechanisms involved in carbonate mineral formation in the [...] Read more.
Microbially induced carbonate precipitation (MICP) is an important process in the synthesis of carbonate minerals, and thus, it is widely explored as a novel approach with potential for many technological applications. However, the processes and mechanisms involved in carbonate mineral formation in the presence of microbes are not yet fully understood. This review covers the current knowledge regarding the role of microbial cells and metabolic products (e.g., extracellular polymeric substances, proteins and amino acids) on the adsorption of divalent metals, adsorption of ionic species and as templates for crystal nucleation. Moreover, they can play a role in the mineral precipitation, size, morphology and lattice. By understanding how microbes and their metabolic products promote suitable physicochemical conditions (pH, Mg/Ca ratio and free CO32− ions) to induce carbonate nucleation and precipitation, the manipulation of the final mineral precipitates could be a reality for (geo)biotechnological approaches. The applications and implications of biogenic carbonates in areas such as geology and engineering are presented and discussed in this review, with a major focus on biotechnology. Full article
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16 pages, 4766 KiB  
Article
Crystal Engineering in Antisolvent Crystallization of Rare Earth Elements (REEs)
by Jonathan Sibanda, Jemitias Chivavava and Alison Emslie Lewis
Minerals 2022, 12(12), 1554; https://doi.org/10.3390/min12121554 - 01 Dec 2022
Cited by 2 | Viewed by 1981
Abstract
Antisolvent crystallization is a separation technology that separates the solute from the solvent by the addition of another solvent, in which the solute is sparingly soluble. High yields are achieved by using higher antisolvent-to-aqueous ratios, but this generates higher supersaturation, which causes excessive [...] Read more.
Antisolvent crystallization is a separation technology that separates the solute from the solvent by the addition of another solvent, in which the solute is sparingly soluble. High yields are achieved by using higher antisolvent-to-aqueous ratios, but this generates higher supersaturation, which causes excessive nucleation. This results in the production of smaller particles, which are difficult to handle in downstream processes. In this work, the effect of varying the organic (antisolvent)-to-aqueous (O/A) ratio and seed loading on the yield, particle size distribution, and morphology of neodymium sulphate product, during its recovery from an aqueous leach solution using antisolvent crystallization, was investigated. A batch crystallizer was used for the experiments, while ethanol was used as an antisolvent. Neodymium sulphate octahydrate [Nd2(SO4)3.8H2O] seeds were used to investigate the effect of seed loading. It was found that particle sizes increased as the O/A ratio increased. This was attributed to the agglomeration of smaller particles that formed at high supersaturation. An O/A ratio of 1.4 resulted in higher yields and particles with a plate-like morphology. The increase in yield was attributed to the increased interaction of ethanol molecules with the solvent, which reduced the solubility of neodymium sulphate. Increasing the seed loading resulted in smaller particle sizes with narrow particle size distribution and improved filtration performance. This was attributed to the promotion of crystal growth and suppression of agglomeration in the presence of seeds. Full article
(This article belongs to the Special Issue Recent Developments in Mineral Processing at University of Cape Town)
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22 pages, 2710 KiB  
Article
Impacts of Crystalline Host Rock on Repository Barrier Materials at 250 °C: Hydrothermal Co-Alteration of Wyoming Bentonite and Steel in the Presence of Grimsel Granodiorite
by Amber Zandanel, Kirsten B. Sauer, Marlena Rock, Florie A. Caporuscio, Katherine Telfeyan and Edward N. Matteo
Minerals 2022, 12(12), 1556; https://doi.org/10.3390/min12121556 - 01 Dec 2022
Cited by 2 | Viewed by 2462
Abstract
Direct disposal of dual-purpose canisters (DPC) has been proposed to streamline the disposal of spent nuclear fuel. However, there are scenarios where direct disposal of DPCs may result in temperatures in excess of the specified upper temperature limits for some engineered barrier system [...] Read more.
Direct disposal of dual-purpose canisters (DPC) has been proposed to streamline the disposal of spent nuclear fuel. However, there are scenarios where direct disposal of DPCs may result in temperatures in excess of the specified upper temperature limits for some engineered barrier system (EBS) materials, which may cause alteration within EBS materials dependent on local conditions such as host rock composition, chemistry of the saturating groundwaters, and interactions between barrier materials themselves. Here we report the results of hydrothermal experiments reacting EBS materials—bentonite buffer and steel—with an analogue crystalline host rock and groundwater at 250 °C. Experiment series explored the effect of reaction time on the final products and the effects of the mineral and fluid reactants on different steel types. Post-mortem X-ray diffraction, electron microprobe, and scanning electron microscopy analyses showed characteristic alteration of both bentonite and steel, including the formation of secondary zeolite and calcium silicate hydrate minerals within the bentonite matrix and the formation of iron-bearing clays and metal oxides at the steel surfaces. Swelling clays in the bentonite matrix were not quantitatively altered to non-swelling clay species by the hydrothermal conditions. The combined results of the solution chemistry over time and post-mortem mineralogy suggest that EBS alteration is more sensitive to initial groundwater chemistry than the presence of host rock, where limited potassium concentration in the solution prohibits conversion of the smectite minerals in the bentonite matrix to non-swelling clay species. Full article
(This article belongs to the Section Clays and Engineered Mineral Materials)
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14 pages, 528 KiB  
Article
On the Sorption Mode of U(IV) at Calcium Silicate Hydrate: A Comparison of Adsorption, Absorption in the Interlayer, and Incorporation by Means of Density Functional Calculations
by Ion Chiorescu, Alena Kremleva and Sven Krüger
Minerals 2022, 12(12), 1541; https://doi.org/10.3390/min12121541 - 30 Nov 2022
Cited by 5 | Viewed by 1626
Abstract
Calcium silicate hydrate (C-S-H) is the main product of cement hydration and has also been shown to be the main sorbing phase of actinide ions interacting with cement. U(IV) has been chosen as an exemplary actinide ion to study actinide sorption at C-S-H [...] Read more.
Calcium silicate hydrate (C-S-H) is the main product of cement hydration and has also been shown to be the main sorbing phase of actinide ions interacting with cement. U(IV) has been chosen as an exemplary actinide ion to study actinide sorption at C-S-H as U is the main element in highly active radioactive waste and because reducing conditions are foreseen in a deep geological repository for such waste. U(IV) surface adsorption, absorption in the interlayer, and incorporation into the calcium oxide layer of C-S-H has been modeled quantum mechanically, applying a density functional approach. For each sorption mode various sites have been considered and a combined dynamic equilibration and optimization approach has been applied to generate a set of representative stable sorption complexes. At the surface and in the interlayer similar U(IV) hydroxo complexes stabilized by Ca2+ ions have been determined as sorbates. Surface adsorption tends to be preferred over absorption in the interlayer for the same type of sites. Incorporation of U(IV) in the CaO layer yields the most favorable sorption site. This result is supported by good qualitative agreement of structures with EXAFS results for other actinides in the oxidation state IV, leading to a new interpretation of the experimental results. Full article
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13 pages, 2912 KiB  
Article
Global Trend for Waste Lithium-Ion Battery Recycling from 1984 to 2021: A Bibliometric Analysis
by Yaoguang Guo, Yujing Liu, Jie Guan, Qianqian Chen, Xiaohu Sun, Nuo Liu, Li Zhang, Xiaojiao Zhang, Xiaoyi Lou and Yingshun Li
Minerals 2022, 12(12), 1514; https://doi.org/10.3390/min12121514 - 27 Nov 2022
Cited by 1 | Viewed by 2621
Abstract
With the massive use of lithium-ion batteries in electric vehicles and energy storage, the environmental and resource problems faced by used lithium-ion batteries are becoming more and more prominent. In order to better resource utilization and environmental protection, this paper employs bibliometric and [...] Read more.
With the massive use of lithium-ion batteries in electric vehicles and energy storage, the environmental and resource problems faced by used lithium-ion batteries are becoming more and more prominent. In order to better resource utilization and environmental protection, this paper employs bibliometric and data analysis methods to explore publications related to waste lithium-ion battery recycling from 1984 to 2021. The Web of Science core set from the SCIE online database was used for this article. These findings demonstrate a considerable increase trend in the number of publications published in the subject of recycling used lithium-ion batteries, with a natural-sciences-centric focus. Argonne National Lab, Chinese Academy of Sciences, and China Academic and Scientific Research Center are the top three institutions in terms of quantity of papers published. The affiliated journals corresponding to these three institutions also have high impact factors, which are 106.47, 44.85, and 58.69, respectively. In comparison to comparable institutes in other nations, the American Argonne National Laboratory supports 223 research articles in this area. China and the US make up the majority of the research’s funding. The two key aspects of current lithium-ion battery recycling research are material structure research and environmentally friendly recycling. Nevertheless, high-capacity lithium-ion batteries, waste lithium-ion integrated structures, and gentle recycling of spent lithium-ion batteries will be the major aspects of study in the future. It is hoped that the above analysis can bring new ideas and methods to the field of waste lithium-ion battery recycling and provide a basis for the subsequent research and application of waste lithium-ion battery recycling. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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13 pages, 7078 KiB  
Article
Estimation of Final Product Concentration in Metalic Ores Using Convolutional Neural Networks
by Jakub Progorowicz, Artur Skoczylas, Sergii Anufriiev, Marek Dudzik and Paweł Stefaniak
Minerals 2022, 12(12), 1480; https://doi.org/10.3390/min12121480 - 22 Nov 2022
Cited by 1 | Viewed by 1175
Abstract
Although artificial neural networks are widely used in various fields, including mining and mineral processing, they can be problematic for appropriately choosing the model architecture and parameters. In this article, we describe a procedure for the optimization of the structure of a convolutional [...] Read more.
Although artificial neural networks are widely used in various fields, including mining and mineral processing, they can be problematic for appropriately choosing the model architecture and parameters. In this article, we describe a procedure for the optimization of the structure of a convolutional neural network model developed for the purposes of metallic ore pre-concentration. The developed model takes as an input two-band X-ray scans of ore grains, and for each scan two values corresponding to concentrations of zinc and lead are returned by the model. The whole process of sample preparation and data augmentation, optimization of the model hyperparameters and training of selected models is described. The ten best models were trained ten times each in order to select the best possible one. We were able to achieve a Pearson coefficient of R = 0.944 for the best model. The detailed results of this model are shown, and finally, its applicability and limitations in real-world scenarios are discussed. Full article
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16 pages, 5484 KiB  
Article
Magnetic Nanosorbents Based on Bentonite and CoFe2O4 Spinel
by Nataliya Khodosova, Lyudmila Novikova, Elena Tomina, Larisa Belchinskaya, Alexander Zhabin, Nikolay Kurkin, Victoria Krupskaya, Olga Zakusina, Tatiana Koroleva, Ekaterina Tyupina, Alexander Vasiliev and Pavel Kazin
Minerals 2022, 12(11), 1474; https://doi.org/10.3390/min12111474 - 21 Nov 2022
Cited by 3 | Viewed by 1700
Abstract
New magnetic nanocomposite sorbents were obtained by doping natural bentonite with nanosized CoFe2O4 spinel (10 and 20 wt.%). Nanocrystals of cobalt ferrite were synthesized by a citrate burning method. The structure and physical-chemical properties of the composites were characterized by [...] Read more.
New magnetic nanocomposite sorbents were obtained by doping natural bentonite with nanosized CoFe2O4 spinel (10 and 20 wt.%). Nanocrystals of cobalt ferrite were synthesized by a citrate burning method. The structure and physical-chemical properties of the composites were characterized by XRD, XRF, TEM, BET, FTIR and Faraday balance magnetometry. During the formation of nanocomposites, 10–30 nm particles of cobalt ferrite occupied mainly the interparticle space of Fe-aluminosilicate that significantly changed the particle morphology and composite porosity, but at the same time retained the structure of the 2:1 smectite layer. A combination of two functional properties of composites, adsorption and magnetism has been found. The adsorption capacity of magnetic nanosorbents exceeded this parameter for bentonite and spinel. Despite the decrease in the adsorption volume, pore size and specific surface area of the composite material relative to bentonite, the sorption activity of the composite increases by 12%, which indicated the influence of the magnetic component on the sorption process. FTIR data confirmed the mechanism of formaldehyde sorption by the composite sorbent. The production of a magnetic nanosorbent opens up new possibilities for controlling the sorption processes and makes it possible to selectively separate the sorbent from the adsorption medium by the action of a magnetic field. Full article
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32 pages, 6210 KiB  
Article
Prospectivity Mapping of Heavy Mineral Ore Deposits Based upon Machine-Learning Algorithms: Columbite-Tantalite Deposits in West- Central Côte d’Ivoire
by Kassi Olivier Shaw, Kalifa Goïta and Mickaël Germain
Minerals 2022, 12(11), 1453; https://doi.org/10.3390/min12111453 - 17 Nov 2022
Viewed by 3169
Abstract
This study aimed to model the prospectivity for placer deposits using geomorphic and landscape parameters. Within a geographic information system (GIS), spatial autocorrelation analysis of 3709 geochemical samples was used to identify prospective and non-prospective targets for columbite-tantalite (Nb-Ta) placer deposits of Hana-Lobo [...] Read more.
This study aimed to model the prospectivity for placer deposits using geomorphic and landscape parameters. Within a geographic information system (GIS), spatial autocorrelation analysis of 3709 geochemical samples was used to identify prospective and non-prospective targets for columbite-tantalite (Nb-Ta) placer deposits of Hana-Lobo (H-L) Geological Complex (West- Central Côte d’Ivoire, West Africa). Based on mineralization system analysis, hydrologic, geomorphologic and landscape parameters were extracted at the locations of the identified targets. Supervised automatic classification approaches were applied, including Random Forest (RF), K-Nearest Neighbors (KNN) and Support Vector Machines (SVM) to find a prospectivity model complex enough to capture the nature of the data. Metrics such as cross-validation accuracy (CVA), Receiver Operating Characteristic (ROC) curves, Area Under Curve (AUC) values and F-score values were used to evaluate the performance and robustness of output models. Results of applying machine-learning algorithms demonstrated that predictions provided by the final RF and KNN models were very close (κ = 0.56 and CVA = 0.69; κ = 0.54 and CVA = 0.68, respectively) and those provided by the SVM models were slightly lower with κ = 0.46 and CVA = 0.63. Independent validation results confirmed the slightly higher performance of both KNN and RF prospectivity models, compared to final SVM. Sensitivity analyses of both KNN and RF prospectivity models for medium and high-grade Nb-Ta deposits show a prediction rate of up to 90%. Full article
(This article belongs to the Special Issue AI-Based GIS for Pinpointing Mineral Deposits)
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21 pages, 7728 KiB  
Article
Mineralogical and Geochemical Characteristics of the H-Pit of the Chatree Gold Deposit, Central Thailand: A Case Study for Assessment of Acid Rock Drainage and Heavy Metal Sources
by Sirawit Kaewpaluk, Abhisit Salam, Thitiphan Assawincharoenkij, Takayuki Manaka, Sopit Poompuang and Surachat Munsamai
Minerals 2022, 12(11), 1446; https://doi.org/10.3390/min12111446 - 15 Nov 2022
Cited by 1 | Viewed by 1896
Abstract
H-pit is one of the significant ore lenses of the Chatree mine in Thailand. Au-Ag mineralization mainly occurs as veins, stockworks, and minor breccias hosted by volcanic and volcaniclastic rocks. Disseminated pyrites are commonly present near mineralized veins in the hanging wall zone. [...] Read more.
H-pit is one of the significant ore lenses of the Chatree mine in Thailand. Au-Ag mineralization mainly occurs as veins, stockworks, and minor breccias hosted by volcanic and volcaniclastic rocks. Disseminated pyrites are commonly present near mineralized veins in the hanging wall zone. This study aims to assess the acid rock drainage (ARD) potential and heavy metal content from the H-pit area. The results indicate that hanging wall rock is a potential acid-forming (PAF) material related to disseminated pyrite formed by hydrothermal alteration. In contrast, the footwall and ore zone materials are classified as non-acid forming (NAF). Because the ore zone has calcite in the veins, it may help buffer the material’s acidity. The results of heavy metal analysis reveal that the ore zone has significantly higher contents of As, Cd, Cu, Pb, and Zn than those in the hanging wall and footwall zones. Moreover, the hanging wall and footwall materials have exceeding values for As, Cd, and Zn compared to those in typical igneous rocks. These heavy metals are interpreted to be sourced from (1) the primary composition in base metal sulfides (e.g., Cu, Pb, and Zn), (2) the substitution of trace elements in sulfides (e.g., As and Cd), and (3) the substitution of trace elements in calcite (e.g., Mn), as evidenced in the EPMA results. In conclusion, the hanging wall rocks in this study containing high sulfur in proximity to the ore zone are a PAF material with heavy metal contaminant sources, whereas the footwall and ore zone materials have a lower potential to be such sources at the Chatree mine. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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22 pages, 5301 KiB  
Article
Evaluation of Different Dispersants on the Dispersion/Sedimentation Behavior of Halloysite, Kaolinite, and Quartz Suspensions in the Enrichment of Halloysite Ore by Mechanical Dispersion
by Emrah Durgut, Mustafa Cinar, Mert Terzi, Ilgin Kursun Unver, Yildiz Yildirim and Orhan Ozdemir
Minerals 2022, 12(11), 1426; https://doi.org/10.3390/min12111426 - 10 Nov 2022
Cited by 4 | Viewed by 1753
Abstract
In this study, the dispersion properties of pure halloysite, kaolinite, and quartz minerals in halloysite ore were determined in the absence and presence of dispersants (sodium silicate, STPP, SHMP). First of all, the samples were characterized by chemical, mineralogical, BET, FTIR, and TEM [...] Read more.
In this study, the dispersion properties of pure halloysite, kaolinite, and quartz minerals in halloysite ore were determined in the absence and presence of dispersants (sodium silicate, STPP, SHMP). First of all, the samples were characterized by chemical, mineralogical, BET, FTIR, and TEM analyses. Afterward, the physico-chemical properties of these minerals were investigated by zeta potential measurements and dispersion/sedimentation experiments in the absence and presence of the dispersants. The zeta potential measurements showed that the surface charges of all minerals changed from negative to positive as the PH changed from basic to acidic. The presence of dispersants at natural pHs indicated that the mineral surface charges tended to become more negative as the concentration increased in the zeta potential measurements. SHMP showed the most effect on the zeta potential. In the dispersion/sedimentation experiments, settling was slowed down with the use of dispersants. Finally, the dispersion properties of halloysite ore in the presence of dispersants were explored using mechanical dispersion and pulp viscosity experiments based on the amount of material passing to <38 μm size and the chemical changes in the materials. As a result of the mechanical dispersion tests carried out in the presence of dispersants (sodium silicate, STPP, SHMP), 71.3% of the material with 30.8% Al2O3 and 50.5% SiO2 content passed to <38 μm size without using dispersant, and 73.2% of <38 μm sized material with 35.5% Al2O3 and 46.1% SiO2 content was gained in the use of 7.5 kg/ton SHMP, which was determined as the optimum within the scope of the study. In conclusion, dispersant use enhanced the mechanical dispersion effect for plastic clay mineral separation from hard minerals in an aqueous medium. Full article
(This article belongs to the Special Issue Nanotubular and Nanofibrous Clay Minerals)
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14 pages, 5179 KiB  
Article
Microbial Mat Stratification in Travertine Depositions of Greek Hot Springs and Biomineralization Processes
by Christos Kanellopoulos, Vasiliki Lamprinou, Artemis Politi, Panagiotis Voudouris, Ioannis Iliopoulos, Maria Kokkaliari, Leonidas Moforis and Athena Economou-Amilli
Minerals 2022, 12(11), 1408; https://doi.org/10.3390/min12111408 - 04 Nov 2022
Cited by 4 | Viewed by 2495
Abstract
The study of microbial mats in extreme environments is of high scientific interest from geological, ecological, and geomicrobiological aspects. These mats represent multilayer bio-structures where each taxonomic group dominates a specific vertical layering distribution resulting from its growth and metabolic activity. In the [...] Read more.
The study of microbial mats in extreme environments is of high scientific interest from geological, ecological, and geomicrobiological aspects. These mats represent multilayer bio-structures where each taxonomic group dominates a specific vertical layering distribution resulting from its growth and metabolic activity. In the present study, microbial mats in a hot spring environment from Aedipsos (Euboea Island, Greece) resulting in the creation of thermogenic travertine, were studied through an interdisciplinary approach. The mineralogical composition was determined by optical microscopy, XRD, and SEM-EDS microanalysis, and the identification of Cyanobacteria was made primarily on morphological characteristics. The main mineral phase in the studied samples is calcite and, to a less extent, aragonite, with several trace elements in the mineral-chemistry composition, i.e., up to 1.93 wt. % MgO, up to 0.52 wt. % SrO, up to 0.44 wt. % Na2O, up to 0.17 wt. % K2O, and up to 3.99 wt. % SO3. The dominant facies are lamination and shrubs, which are the most common among the facies of thermogenic travertines of the area. Several layers were identified, (i) a top mainly abiotic layer consisting of calcium carbonate micritic crystals, (ii) a second biotic layer–the Cyanobacteria layer, dominated by the species Leptolyngbya perforans, (iii) a third biotic layer where Leptolyngbya perforans, Chloroflexus and other bacteria occur, and (iv) a deeper abiotic part with several layers where no photosynthetic microorganisms occur. In the upper layers, nineteen (19) species of Cyanobacteria were identified, classified in the orders Chroococcales (37%), Synechococcales (31%), Oscillatoriales (16%), and Spirulinales (6%). Among the identified Cyanobacteria, there are typical thermophilic and limestone substrate species. These Cyanobacteria are found to participate in the biomineralization and biologically-influenced processes, i.e., (i) filamentous Cyanobacteria are trapping calcium carbonate crystals, and diatoms, (ii) extracellular polymeric substances (EPS) create crystal retention lattice contributing to the biomineralization process, and (iii) filamentous sheaths of Cyanobacteria are calcified, resulting in the creation of calcium carbonate tubes. Full article
(This article belongs to the Special Issue Bio-Geochemistry of Heavy Metals/Metalloids)
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17 pages, 2088 KiB  
Article
Oxidative Dissolution of Low-Grade Ni-Cu Ore and Impact on Flotation of Pentlandite
by Benjamin Musuku, Eija Saari and Olli Dahl
Minerals 2022, 12(11), 1406; https://doi.org/10.3390/min12111406 - 03 Nov 2022
Cited by 2 | Viewed by 1657
Abstract
This paper investigated the effect of mineral surface oxidation on the floatability of Kevitsa low-grade Ni-Cu ore. Physicochemical measurements, ethylene diamine tetra acetic acid (EDTA) extraction, and oxygen uptake experiments were carried out with slurry and recycled process water samples obtained from the [...] Read more.
This paper investigated the effect of mineral surface oxidation on the floatability of Kevitsa low-grade Ni-Cu ore. Physicochemical measurements, ethylene diamine tetra acetic acid (EDTA) extraction, and oxygen uptake experiments were carried out with slurry and recycled process water samples obtained from the Kevitsa Cu-Ni sequential concentrator plant. The pH of recycled process water, copper flotation feed, and nickel flotation feed dropped by 0.7, 0.4, and 0.7 points, respectively, from May to July. The oxygen demand increased from recycled process water to the copper flotation feed, then dropped for the nickel flotation feed. The nickel flotation feed Redox potential (ORP) was lowest for July, while EDTA extractable metals increased from May to July. There was a 20% drop in nickel recoveries from May to July. Based on ORP measurements of the nickel flotation feed, good nickel flotation takes place in a moderately oxidizing (75–170 mV) and alkaline (9.2–9.7 pH) environment. Therefore, the ORP/pH of the nickel flotation feed is important to the nickel flotation. The results showed that at the Kevitsa plant, the grinding process is an electrochemically active environment, which, together with the incoming recycled process water quality, defines the degree of mineral surface oxidation for flotation. The increasing corrosiveness of the recycled process water increased mineral surface oxidation and depressed pentlandite flotation. Laboratory flotation experiments confirmed the observed poor plant flotation response when the corrosiveness of recycled process water increased. Total dissolved solids (TDS) was proven to be a reliable online parameter for the corrosiveness of the recycled process water and was inversely proportional to the pentlandite recovery. The findings of this study may help the plant develop ways to enable a timely response to changes in recycled process water quality to prevent harmful impacts on pentlandite flotation. Full article
(This article belongs to the Special Issue Water within Minerals Processing, Volume II)
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11 pages, 10332 KiB  
Article
Methodology and Model to Predict HPGR Throughput Based on Piston Press Testing
by Giovanni Pamparana, Bern Klein and Mauricio Guimaraes Bergerman
Minerals 2022, 12(11), 1377; https://doi.org/10.3390/min12111377 - 29 Oct 2022
Cited by 3 | Viewed by 2199
Abstract
Sizing High-Pressure Grinding Rolls (HPGR) requires a large quantity of material, making it not attractive and costly to be considered for new mining projects regardless of their energy consumption reduction benefits. Ongoing efforts are being made at the University of British Columbia to [...] Read more.
Sizing High-Pressure Grinding Rolls (HPGR) requires a large quantity of material, making it not attractive and costly to be considered for new mining projects regardless of their energy consumption reduction benefits. Ongoing efforts are being made at the University of British Columbia to predict the behaviour of the HPGR using a low quantity of material on a piston-and-die press apparatus. Although the energy requirements and size reduction predictive models are already developed, there is still a need to predict the HPGR throughput on a small-scale test. This paper presents a new model to predict the HPGR throughput based on the previously developed model to predict the operational gap by using less than 2 kg of sample. The throughput model was developed using machine learning techniques and calibrated using pilot-scale HPGR tests and piston press tests. The resulting model has an R2 of 0.91 with an average prediction error of ±4.2%. The developed methodology has the potential to fill the gap of the missing throughput model. Further pilot-scale HPGR testing is required to continue validating the model. Full article
(This article belongs to the Special Issue Experimental and Numerical Studies of Mineral Comminution)
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18 pages, 2428 KiB  
Article
A Combined Extended X-ray Absorption Fine Structure Spectroscopy and Density Functional Theory Study of Americium vs. Yttrium Adsorption on Corundum (α–Al2O3)
by Nina Huittinen, Sinikka Virtanen, André Rossberg, Manuel Eibl, Satu Lönnrot and Robert Polly
Minerals 2022, 12(11), 1380; https://doi.org/10.3390/min12111380 - 29 Oct 2022
Viewed by 1472
Abstract
Adsorption reactions on mineral surfaces are influenced by the overall concentration of the adsorbing metal cation. Different site types (strong vs. weak ones) are often included to describe the complexation reactions in the various concentration regimes. More specifically, strong sites are presumed to [...] Read more.
Adsorption reactions on mineral surfaces are influenced by the overall concentration of the adsorbing metal cation. Different site types (strong vs. weak ones) are often included to describe the complexation reactions in the various concentration regimes. More specifically, strong sites are presumed to retain metal ions at low sorbate concentrations, while weak sites contribute to metal ion retention when the sorbate concentration increases. The involvement of different sites in the sorption reaction may, thereby, also be influenced by competing cations, which increase the overall metal ion concentration in the system. To date, very little is known about the complex structures and metal ion speciation in these hypothetical strong- and weak-site regimes, especially in competing scenarios. In the present study, we have investigated the uptake of the actinide americium on corundum (α–Al2O3) in the absence and presence of yttrium as competing metal by combining extended X-ray absorption fine structure spectroscopy (EXAFS) with density functional theory (DFT) calculations. Isotherm studies using the radioactive 152Eu tracer were used to identify the sorption regimes where strong sites and weak sites contribute to the sorption reaction. The overall americium concentration, as well as the presence of yttrium could be seen to influence both the amount of americium uptake by corundum, but also the speciation at the surface. More specifically, increasing the Am3+ or Y3+ concentrations from the strong site to the weak site concentration regimes in the mineral suspensions resulted in a decrease in the overall Am–O coordination number from nine to eight, with a subsequent shortening of the average Am–O bond length. DFT calculations suggest a reduction of the surface coordination with increasing metal–ion loading, postulating the formation of tetradentate and tridentate Am3+ complexes at low and high surface coverages, respectively. Full article
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60 pages, 13465 KiB  
Review
Order–Disorder Diversity of the Solid State by NMR: The Role of Electrical Charges
by Luis Sánchez-Muñoz, Pierre Florian, Zhehong Gan and Francisco Muñoz
Minerals 2022, 12(11), 1375; https://doi.org/10.3390/min12111375 - 29 Oct 2022
Viewed by 1759
Abstract
The physical explanations and understanding of the order–disorder phenomena in the solid state are commonly inferred from the experimental capabilities of the characterization techniques. Periodicity is recorded according to the averaging procedure of the conventional reciprocal-space techniques (RSTs) in many solids. This approach [...] Read more.
The physical explanations and understanding of the order–disorder phenomena in the solid state are commonly inferred from the experimental capabilities of the characterization techniques. Periodicity is recorded according to the averaging procedure of the conventional reciprocal-space techniques (RSTs) in many solids. This approach gives rise to a sharp trimodal view including non-crystalline or amorphous compounds, aperiodic crystals and periodic crystals. However, nuclear magnetic resonance (NMR) spectroscopy offers an alternative approach that is derived from the distinct character of the measurements involved at the local scale. Here, we present a sequence of progressive order–disorder states, from amorphous structures up to fully ordered mineral structures, showing the great diversity existing in the solid state using multinuclear NMR spectroscopy. Some examples in glasses and products of their crystallization are used, as well as several minerals (including beryl-group and feldspar-group minerals) at magnetic fields up to 35.2 T, and some examples from literature. This approach suggests that the solid state is a dynamic medium, whose behavior is due to atomic adjustments from local compensation of electrical charges between similar structural states, which explains Ostwald’s step rule of successive reactions. In fully ordered feldspar minerals, we propose that the electronic structure of the elements of the cavity site is involved in bonding, site morphology and feldspar topology. Furthermore, some implications are derived about what is a mineral structure from the point of view of the NMR experiments. They open the possibility for the development of the science of NMR Mineralogy. Full article
(This article belongs to the Special Issue NMR Spectroscopy in Mineralogy and Crystal Structures)
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18 pages, 3742 KiB  
Article
Alkali-Activated Metakaolins: Mineral Chemistry and Quantitative Mineral Composition
by Marta Valášková, Zdeněk Klika, Jozef Vlček, Lenka Matějová, Michaela Topinková, Helena Pálková and Jana Madejová
Minerals 2022, 12(11), 1342; https://doi.org/10.3390/min12111342 - 23 Oct 2022
Cited by 3 | Viewed by 1605
Abstract
The reaction products resulting from the alkali-activation of metakaolin are impacted by the composition of the initial kaolin, and amount of alkali-activated kaolinite and water. The present study focused on analyzing these parameters on the metakaolins calcined at 800 °C from three kaolins, [...] Read more.
The reaction products resulting from the alkali-activation of metakaolin are impacted by the composition of the initial kaolin, and amount of alkali-activated kaolinite and water. The present study focused on analyzing these parameters on the metakaolins calcined at 800 °C from three kaolins, and the metakaolins’ alkali activation for 2, 3 and 28 days. The first objective was to evaluate the mineral chemistry and quantitative mineral phase composition from the bulk chemical analysis using the chemical quantitative mineral analysis (CQMA) procedure and conduct a comparison of the chemistry of the metakaolins after alkali activation for 28 days according to the elements Al, Si, Na and K, using the leaching test in distilled water. The second task was to search for possible relationships between the quantitative number of phases in alkali-activated metakaolins and compressive strength. The main methods used for the characterization of material were X-ray fluorescence, X-ray diffraction, thermal TG/DTA and infrared spectroscopy. Metakaolins alkali activated for 28 days contained crystalline quartz, muscovite, orthoclase, and unreacted metakaolinite contained zeolite A (Z-A), hydrosodalite (HS) and thermonatrite (TN) in the amorphous/weakly crystalline phase. The compressive strengths (CS) from 6.42 ± 0.33 to 9.97 ± 0.50 MPa are related positively to H2O+ and H2O bound in HS and TN. Full article
(This article belongs to the Special Issue Development in Geopolymer Materials and Applications)
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15 pages, 2863 KiB  
Article
Structural and Elastic Behaviour of Sodalite Na8(Al6Si6O24)Cl2 at High-Pressure by First-Principle Simulations
by Gianfranco Ulian and Giovanni Valdrè
Minerals 2022, 12(10), 1323; https://doi.org/10.3390/min12101323 - 20 Oct 2022
Cited by 2 | Viewed by 1987
Abstract
Sodalite Na8(Al6Si6O24)Cl2 (space group P4¯3n) is an important mineral belonging to the zeolite group, with several and manyfold fundamental and technological applications. Despite the interest in this mineral from [...] Read more.
Sodalite Na8(Al6Si6O24)Cl2 (space group P4¯3n) is an important mineral belonging to the zeolite group, with several and manyfold fundamental and technological applications. Despite the interest in this mineral from different disciplines, very little is known regarding its high-pressure elastic properties. The present study aims at filling this knowledge gap, reporting the equation of state and the elastic moduli of sodalite calculated in a wide pressure range, from −6 GPa to 22 GPa. The results were obtained from Density Functional Theory simulations carried out with Gaussian-type basis sets and the well-known hybrid functional B3LYP. The DFT-D3 a posteriori correction to include the van der Waals interactions in the physical treatment of the mineral was also applied. The calculated equation of state parameters at 0 GPa and absolute zero (0 K), i.e., K0 = 70.15(7) GPa, K’ = 4.46(2) and V0 = 676.85(3) Å3 are in line with the properties derived from the stiffness tensor, and in agreement with the few experimental data reported in the literature. Sodalite was found mechanically unstable when compressed above 15.6 GPa. Full article
(This article belongs to the Section Clays and Engineered Mineral Materials)
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15 pages, 2058 KiB  
Article
Chemical and Mineralogical Characterization of Montevive Celestine Mineral
by Noemi Ariza-Rodríguez, Alejandro B. Rodríguez-Navarro, Mónica Calero de Hoces, Jose Manuel Martin and Mario J. Muñoz-Batista
Minerals 2022, 12(10), 1261; https://doi.org/10.3390/min12101261 - 05 Oct 2022
Cited by 5 | Viewed by 2381
Abstract
The Montevive celestine mineral deposit, set in the Granada Basin in a marine evaporitic uppermost Tortonian–lowermost Messinian sequence, is the largest reserve in Europe of this economically important strontium ore. Currently, the mine has a large amount of tailings resulting from the rejection [...] Read more.
The Montevive celestine mineral deposit, set in the Granada Basin in a marine evaporitic uppermost Tortonian–lowermost Messinian sequence, is the largest reserve in Europe of this economically important strontium ore. Currently, the mine has a large amount of tailings resulting from the rejection of a manual dry screening of high-grade celestine mineral. This visual and density screening was carried out in the early days of mining (1954–1973). Concentrating the celestine mineral and increasing the ore recovery rate would reduce mine operation costs and the generation of new tailings, reducing the impact on the environment. In order to define more adequate concentration methods, we have used complementary analytical techniques such as optical (OM) and scanning and transmission electron microscopy (SEM and TEM), energy-dispersive X-rays (EDXs), X-ray fluorescence (XRF), and X-ray diffraction (XRD) to fully characterize the morphology, microstructure, chemistry, and mineralogy of the celestine mineral. The low-grade mineral is made of prismatic celestine crystals that are replacing a matrix of micro sparry calcite. Other minority minerals are strontianite, dolomite, quartz, and clays (kaolinite, paragonite, and illite). There is also a certain amount of iron oxides and hydroxides (mainly magnetite) associated with clays. We showed that the concentration of low-grade celestine mineral can be achieved through a low-cost and eco-friendly method based on grinding and size separation. The coarser fractions (>5 mm) have more celestine (up to 12 percent units higher than the starting unprocessed mineral) due to the selective loss of calcite and minority minerals (quartz, clays, and iron oxides) that are mainly found in the finer fraction (<1 mm). This process can make mine exploitation more sustainable, reducing the generation of residues that negatively impact the environment. Full article
(This article belongs to the Section Mineral Exploration Methods and Applications)
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34 pages, 31457 KiB  
Article
Coastal Environment Impact on the Construction Materials of Anfushi’s Necropolis (Pharos’s Island) in Alexandria, Egypt
by Abdelrhman Fahmy, Eduardo Molina-Piernas, Javier Martínez-López, Philip Machev and Salvador Domínguez-Bella
Minerals 2022, 12(10), 1235; https://doi.org/10.3390/min12101235 - 28 Sep 2022
Cited by 1 | Viewed by 3108
Abstract
The only example and reference of Ptolemaic Alexandrian tombs, with clear integrations of Egyptian-style scenes and decorations, is considered an endangered archaeological site due to different coastal environmental risks in Alexandria and the absence of maintenance. Anfushi’s Necropolis is located near the western [...] Read more.
The only example and reference of Ptolemaic Alexandrian tombs, with clear integrations of Egyptian-style scenes and decorations, is considered an endangered archaeological site due to different coastal environmental risks in Alexandria and the absence of maintenance. Anfushi’s Necropolis is located near the western harbour (Island of Pharos) and dates back to the 2nd century BC. Sea level rises, earthquakes, flooding, storminess, variations in temperature, rainfall, and wind are the factors that have the largest effect on the destruction and decay of Anfushi’s Necropolis building materials. This paper’s main objectives were to characterize this necropolis’s building materials and assess its durability problems and risks regarding the coastal environment. Additionally, the vector mapping of its architectural and structural elements was applied for documentation and recording purposes for the necropolis. To achieve these aims, field (recording and photographs), desk (engineering drawing and mapping), and laboratory works (X-ray diffraction, X-ray fluorescence, binocular microscopy, polarizing microscopy, and scanning electron microscopy) were carried out. The results confirmed the probabilistic risk of sea level rises and its impact on the submergence of Anfushi’s Necropolis. The structural deficiencies of the tombs were caused by the effect of earthquake tremors along with anthropogenic factors. In addition, chemical and microscopic investigations showed that salt weathering (halite and gypsum) induced the decay of the building materials. Full article
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23 pages, 6309 KiB  
Article
Paleoenvironmental Conditions and Factors Controlling Organic Carbon Accumulation during the Jurassic–Early Cretaceous, Egypt: Organic and Inorganic Geochemical Approach
by Ahmed Mansour, Thomas Gentzis, Ibrahim M. Ied, Mohamed S. Ahmed and Michael Wagreich
Minerals 2022, 12(10), 1213; https://doi.org/10.3390/min12101213 - 26 Sep 2022
Cited by 2 | Viewed by 1681
Abstract
The Jurassic–Early Cretaceous was a time of variable organic carbon burial associated with fluctuations of marine primary productivity, weathering intensity, and redox conditions in the pore and bottom water at paleo-shelf areas in north Egypt. This time interval characterized the deposition of, from [...] Read more.
The Jurassic–Early Cretaceous was a time of variable organic carbon burial associated with fluctuations of marine primary productivity, weathering intensity, and redox conditions in the pore and bottom water at paleo-shelf areas in north Egypt. This time interval characterized the deposition of, from old to young, the Bahrein, Khatatba, Masajid, and Alam El Bueib Formations in the north Western Desert. Although several studies have been devoted to the excellent source rock units, such as the Khatatba and Alam El Bueib Formations, studies on paleoenvironmental changes in redox conditions, paleoproductivity, and continental weathering and their impact on organic carbon exports and their preservation for this interval are lacking. This study presents organic and inorganic geochemical data for the Jurassic–Lower Cretaceous sediments from the Almaz-1 well in the Shushan Basin, north Western Desert. A total of 32 cuttings samples were analyzed for their major and trace elements, carbonates, and total organic carbon (TOC) contents. Data allowed the reconstruction of paleoenvironmental conditions in the southern Tethys Ocean and assessment of the changes in paleo-redox, paleo-weathering, and marine primary productivity, and the role of sediment supply. Additionally, factors that governed the accumulation of organic matter in the sediment were interpreted. Results showed that the Khatatba Formation was deposited during a phase of enhanced marine primary productivity under prevalent anoxia, which triggered enhanced organic matter production and preservation. During the deposition of the Khatatba Formation, significant terrigenous sediment supply and continental weathering were followed by a limited contribution of coarse clastic sediment fluxes due to weak continental weathering and enhanced carbonate production. The Bahrein, Masajid, and Alam El Bueib Formations were deposited during low marine primary productivity and prevalent oxygenation conditions that led to poor organic matter production and preservation, respectively. A strong terrigenous sediment supply and continental weathering predominated during the deposition of the Bahrein Formation and the lower part of the Alam El Bueib Formation compared to the limited coarse clastic supply and continental weathering during the deposition of the carbonate Masajid Formation and the upper part of the Alam El Bueib Formation. Such conditions resulted in the enhanced dilution and decomposition of labile organic matter, and, thus, organic carbon-lean accumulation in these sediments. Full article
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15 pages, 7043 KiB  
Review
On the Origin of New and Rare Minerals Discovered in the Othrys and Vermion Ophiolites, Greece: An Overview
by Maria Economou-Eliopoulos and Federica Zaccarini
Minerals 2022, 12(10), 1214; https://doi.org/10.3390/min12101214 - 26 Sep 2022
Viewed by 1342
Abstract
In this contribution we review the mineralogical characteristics of five new and rare minerals discovered in the Othrys and Vermion ophiolites located in Greece, with the aim to better understand their origin. Three new minerals, namely tsikourasite Mo3Ni2P(1+x) [...] Read more.
In this contribution we review the mineralogical characteristics of five new and rare minerals discovered in the Othrys and Vermion ophiolites located in Greece, with the aim to better understand their origin. Three new minerals, namely tsikourasite Mo3Ni2P(1+x) (x < 0.25), grammatikopoulosite NiVP and eliopoulosite V7S8, were found in the chromitite from the Agios Stefanos deposit, whereas arsenotučekite Ni18Sb3AsS16 was discovered in the Eretria (Tsangli) chromium mine, located in the Othrys ophiolite complex. The formation of the new phosphides tsikourasite and grammatikopoulosite and the sulfide eliopoulosite from Agios Stefanos took place after the precipitation of the host chromitite. Very likely, they formed at lower pressure in an extremely low fO2 and reducing environment during the serpentinization that affected the host ophiolite. The origin of arsenotučekite in chromitites coexisting with Fe–Ni–Cu-sulfide mineralization and magnetite at the Eretria (Tsangli) mine, is believed to be related to a circulating hydrothermal system. The most salient feature of theophrastite Ni(OH)2 and associated unnamed (Ni,Co,Mn)(OH)2 with a varying compositional range and a concentrating development, as successive thin layers, composed by fine fibrous crystals. The extremely tiny crystals of these hydroxides and the spatial association of mixed layers of Ni-silicides with theophrastite may reflect the significant role of the interaction process between adjacent layers on the observed structural features. The scarcity in nature of the new minerals reviewed in this paper is probably due to the required extreme physical-chemical conditions, which are rarely precipitated. Full article
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12 pages, 2454 KiB  
Article
Prediction of the Adsorption Behaviors of Radionuclides onto Bentonites Using a Machine Learning Method
by Do-Hyeon Kim and Jun-Yeop Lee
Minerals 2022, 12(10), 1207; https://doi.org/10.3390/min12101207 - 25 Sep 2022
Cited by 2 | Viewed by 1742
Abstract
This study builds a model to predict distribution coefficients (Kd) using the random forest (RF) method and a machine learning model based on the Japan Atomic Energy Agency Sorption Database (JAEA-SDB). A database of ten input variables, including the distribution coefficient, [...] Read more.
This study builds a model to predict distribution coefficients (Kd) using the random forest (RF) method and a machine learning model based on the Japan Atomic Energy Agency Sorption Database (JAEA-SDB). A database of ten input variables, including the distribution coefficient, pH, initial radionuclide concentrations, solid–liquid ratio, ionic strength, oxidation number, cation exchange capacity, surface area, electronegativity, and ionic radius, was constructed and used for the RF model calculation. The calculation parameters employed in this work included two different hyperparameters, the number of decision trees and the maximum number of variables to divide each node, together with the random seeds inside the RF model. The coefficients of determination were derived with various combinations of hyperparameters and random seeds, and were employed to assess the RF model calculation result. Based on the results of the RF model, the distribution coefficients of 22 target nuclides (Am, Ac, Co, Cm, Cd, Cs, Cu, Na, Np, Ni, Nb, U, Sr, Sn, Pb, Pa, Pu, Po, I, Tc, Th, and Zr) were predicted successfully. Among the various input variables, pH was found to make the highest contribution to determining the distribution coefficient. The novelty of this study lies in the first application of the machine learning method for predicting the Kd value of bentonites, using JAEA-SDB. This study has established a model for reliably predicting the distribution coefficient for various radionuclides that is intended for use in evaluating the Kd value in arbitrary aqueous conditions. Full article
(This article belongs to the Special Issue The Role of Clays in Geological Disposal of Radioactive Waste)
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17 pages, 3760 KiB  
Article
Geochemical and Sr-Isotopic Study of Clinopyroxenes from Somma-Vesuvius Lavas: Inferences for Magmatic Processes and Eruptive Behavior
by Valeria Di Renzo, Carlo Pelullo, Ilenia Arienzo, Lucia Civetta, Paola Petrosino and Massimo D’Antonio
Minerals 2022, 12(9), 1114; https://doi.org/10.3390/min12091114 - 31 Aug 2022
Cited by 3 | Viewed by 2158
Abstract
Somma-Vesuvius is one of the most dangerous active Italian volcanoes, due to the explosive character of its activity and because it is surrounded by an intensely urbanized area. For mitigating the volcanic risks, it is important to define how the Somma-Vesuvius magmatic system [...] Read more.
Somma-Vesuvius is one of the most dangerous active Italian volcanoes, due to the explosive character of its activity and because it is surrounded by an intensely urbanized area. For mitigating the volcanic risks, it is important to define how the Somma-Vesuvius magmatic system worked during the past activity and what processes took place. A continuous coring borehole drilled at Camaldoli della Torre, along the southern slopes of Somma-Vesuvius, allowed reconstructing its volcanic and magmatic history in a previous study. In this work, the wide range of chemical (Mg# = 92–69) and isotopic (87Sr/86Sr = 0.70781–0.70681) compositions, collected on single clinopyroxene crystals separated from selected lava flow units of the Camaldoli della Torre sequence, have been integrated with the already available bulk geochemical and Sr-isotopic data. The detected chemical and isotopic signatures and their variation through time allow us to better constrain the behavior of the volcano magmatic feeding system, highlighting that mixing and/or assimilation processes occurred before a significant change in the eruptive dynamics at Somma-Vesuvius during a period of polycyclic caldera formation, starting with the Pomici di Base Plinian eruption (ca. 22 ka). Full article
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22 pages, 10057 KiB  
Article
Geochemical Indication of Functional Zones at the Archaeological Sites of Eastern Europe
by Marianna Kulkova
Minerals 2022, 12(9), 1075; https://doi.org/10.3390/min12091075 - 25 Aug 2022
Cited by 4 | Viewed by 1403
Abstract
The article considers a new approach for determining the functional zones of the prehistoric archaeological sites in Eastern Europe by the method of geochemical indication: the use of mathematical statistics for processing the geochemical data of cultural deposits at archaeological sites, and the [...] Read more.
The article considers a new approach for determining the functional zones of the prehistoric archaeological sites in Eastern Europe by the method of geochemical indication: the use of mathematical statistics for processing the geochemical data of cultural deposits at archaeological sites, and the identification of groups of interrelated chemical elements and compounds that reflects the processes of natural sedimentation and anthropogenic activity. It makes it possible to separate the lithological and anthropogenic components. This approach is important for the identification of geochemical element groups associated with different functional zones. The reconstructions were conducted at the Neolithic, Early Metal Age, and the Bronze-Early Iron Age sites in Eastern Europe. Abnormal concentrations of the association (P2O5antr, CaOantr and Srantr) in sediments are attributed to zones of accumulation of bone remains. Anomalous concentrations of a group of elements (K2Oantr, Rbantr) in deposits are associated with wood ash and fireplaces, ash residues from ritual activities, and fires. The group of elements (Ba, MnO, Corg) reflects the accumulation of humus and organic remains, and can characterize areas with food residues, skins, and rotten wood. With the help of the distribution of the main lithological elements (SiO2, Al2O3) in sediments, it is possible to reconstruct the paleorelief at the sites. Full article
(This article belongs to the Special Issue Environment and Geochemistry of Sediments)
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14 pages, 1481 KiB  
Article
Coal Feed-Dependent Variation in Fly Ash Chemistry in a Single Pulverized-Combustion Unit
by James C. Hower, John G. Groppo, Shelley D. Hopps, Tonya D. Morgan, Heileen Hsu-Kim and Ross K. Taggart
Minerals 2022, 12(9), 1071; https://doi.org/10.3390/min12091071 - 24 Aug 2022
Cited by 3 | Viewed by 1447
Abstract
Four suites of fly ash, all generated at the same power plant, were selected for the study of the distribution of rare earth elements (REE). The fly ashes represented two runs of single-seam/single-mine coals and two runs of run-of-mine coals representing several coal [...] Read more.
Four suites of fly ash, all generated at the same power plant, were selected for the study of the distribution of rare earth elements (REE). The fly ashes represented two runs of single-seam/single-mine coals and two runs of run-of-mine coals representing several coal seams from several mines. Plots of the upper continental crust-normalized REE, other parameters derived from the normalization, and the principal components analysis of the derived REE parameters (including the sum of the lanthanides plus yttrium and the ratio of the light to heavy REE) all demonstrated that the relatively rare earth-rich Fire Clay coal-derived fly ashes have a different REE distribution, with a greater concentration of REE with a relative dominance of the heavy REE, than the other fly ashes. Particularly with the Fire Clay coal-derived fly ashes, there is a systematic partitioning of the overall amount and distribution of the REE in the passage from the mechanical fly ash collection through to the last row of the electrostatic precipitator hoppers. Full article
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22 pages, 7810 KiB  
Article
Deep Learning Optimized Dictionary Learning and Its Application in Eliminating Strong Magnetotelluric Noise
by Guang Li, Xianjie Gu, Zhengyong Ren, Qihong Wu, Xiaoqiong Liu, Liang Zhang, Donghan Xiao and Cong Zhou
Minerals 2022, 12(8), 1012; https://doi.org/10.3390/min12081012 - 12 Aug 2022
Cited by 8 | Viewed by 2882
Abstract
The noise suppression method based on dictionary learning has shown great potential in magnetotelluric (MT) data processing. However, the constraints used in the existing algorithm’s method need to set manually, which significantly limits its application. To solve this problem, we propose a deep [...] Read more.
The noise suppression method based on dictionary learning has shown great potential in magnetotelluric (MT) data processing. However, the constraints used in the existing algorithm’s method need to set manually, which significantly limits its application. To solve this problem, we propose a deep learning optimized dictionary learning denoising method. We use a deep convolutional network to learn the characteristic parameters of high-quality MT data independently and then use them as the constraints for dictionary learning so as to achieve fully adaptive sparse decomposition. The method uses unified parameters for all data and completely eliminates subjective bias, which makes it possible to batch-process MT data using sparse decomposition. The processing results of simulated and field data examples show that the new method has good adaptability and can achieve recognition with high accuracy. After processing with our method, the apparent resistivity and phase curves became smoother and more continuous, and the results were validated by the remote reference method. Our method can be an effective alternative method when no remote reference station is set up or the remote reference processing is not effective. Full article
(This article belongs to the Special Issue Electromagnetic Exploration: Theory, Methods and Applications)
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18 pages, 2080 KiB  
Review
Data Quality in Geochemical Elemental and Isotopic Analysis
by V. Balaram and M. Satyanarayanan
Minerals 2022, 12(8), 999; https://doi.org/10.3390/min12080999 - 08 Aug 2022
Cited by 9 | Viewed by 2463
Abstract
Appropriate sampling, sample preparation, choosing the right analytical instrument, analytical methodology, and adopting proper data generation protocols are essential for generating data of the required quality for both basic and applied geochemical research studies. During the last decade, instrumental advancements, in particular further [...] Read more.
Appropriate sampling, sample preparation, choosing the right analytical instrument, analytical methodology, and adopting proper data generation protocols are essential for generating data of the required quality for both basic and applied geochemical research studies. During the last decade, instrumental advancements, in particular further developments in ICP-MS, such as the use of tandem ICP-MS, high-resolution mass spectrometry to resolve several interferences, and the use of the second path with a collision/reaction cell in multi-collector ICP-MS (MC-ICP-MS) to effectively resolve interferences, have brought in remarkable improvements in accuracy and precision in both elemental and isotopic analyses. The availability of a number of well-characterized geological certified reference samples having both elemental and isotopic data-enabled matrix-matching calibrations and contributed to the quality and traceability of the geochemical data in several cases. There have been some developments in the sample dissolution methods also. A range of quality issues related to sampling, packaging and transport, powdering, dissolution, the application of suitable instrumental analytical techniques, calibration methods, accuracy, and precision are addressed which are helpful in geochemical studies. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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25 pages, 5971 KiB  
Article
Origin of Historical Ba-Rich Slags Related to Pb-Ag Production from Jihlava Ore District (Czech Republic)
by Jaroslav Kapusta, Zdeněk Dolníček, Ondra Sracek and Karel Malý
Minerals 2022, 12(8), 985; https://doi.org/10.3390/min12080985 - 02 Aug 2022
Cited by 1 | Viewed by 1892
Abstract
The aim of this study was to characterize historical slags which originated during silver production from the Jihlava ore district, Czech Republic. The area was among the head producers of silver within the Lands of the Czech Crown in 13th–14th centuries. The mined [...] Read more.
The aim of this study was to characterize historical slags which originated during silver production from the Jihlava ore district, Czech Republic. The area was among the head producers of silver within the Lands of the Czech Crown in 13th–14th centuries. The mined ores had complex composition, being formed mostly by pyrite, sphalerite, galena, chalcopyrite, and accessory silver-rich minerals such as silver-bearing tetrahedrite (freibergite) or pyrargyrite, with gangue represented by quartz and Mn-rich carbonates or baryte. Large volumes of slags with contrasting composition were generated during the Pb-Ag production. Altogether, two main types of slags were identified in the district. The first type is characterized by high BaO contents (up to 34.5 wt.%) and dominancy of glass, minor quartz, and accessory amounts of Ba-rich feldspar (up to 93 mol.% of Cls), metal-rich inclusions, Ba-Pb sulphates and only rare pyroxene, wollastonite and melilite. The composition of the second group belongs to fayalitic slags containing glass, Fe-rich olivine, accessory pyroxene, feldspar, quartz, and inclusions of various metallic phases. Fluxes were derived from gangue (quartz, carbonates, baryte) or local host rocks for both types of slag. The calculated viscosity indexes reflect (with minor exceptions) medium-to-high effectivity of metal separation. Smelting temperatures were estimated from a series of ternary plots; however, more reliable estimates for both types of slags were obtained only from experimental determination of melting temperature and calculations using bulk/glass compositions (~1100–1200 °C). Full article
(This article belongs to the Special Issue Applications of Geochemistry in Archaeology)
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23 pages, 2489 KiB  
Review
Application of Raman Spectroscopy for Studying Shocked Zircon from Terrestrial and Lunar Impactites: A Systematic Review
by Dmitry A. Zamyatin
Minerals 2022, 12(8), 969; https://doi.org/10.3390/min12080969 - 29 Jul 2022
Cited by 3 | Viewed by 2142
Abstract
A highly resistant mineral, zircon is capable of preserving information about impact processes. The present review paper is aimed at determining the extent to which Raman spectroscopy can be applied to studying shocked zircons from impactites to identify issues and gaps in the [...] Read more.
A highly resistant mineral, zircon is capable of preserving information about impact processes. The present review paper is aimed at determining the extent to which Raman spectroscopy can be applied to studying shocked zircons from impactites to identify issues and gaps in the usage of Raman spectroscopy, both in order to highlight recent achievements, and to identify the most effective applications. Method: Following PRISMA guidelines, the review is based on peer-reviewed papers indexed in Google Scholar, Scopus and Web of Science databases up to 5 April 2022. Inclusion criteria: application of Raman spectroscopy to the study of shocked zircon from terrestrial and lunar impactites. Results: A total of 25 research papers were selected. Of these, 18 publications studied terrestrial impact craters, while 7 publications focused on lunar breccia samples. Nineteen of the studies were focused on the acquisition of new data on geological structures, while six examined zircon microstructures, their textural and spectroscopic features. Conclusions: The application of Raman spectroscopy to impactite zircons is linked with its application to zircon grains of various terrestrial rocks and the progress of the electron backscatter diffraction (EBSD) technique in the early 2000s. Raman spectroscopy was concluded to be most effective when applied to examining the degree of damage, as well as identifying phases and misorientation in zircon. Full article
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20 pages, 5195 KiB  
Article
Recovery of Rare Earth Elements from Mining Tailings: A Case Study for Generating Wealth from Waste
by Luver Echeverry-Vargas and Luz Marina Ocampo-Carmona
Minerals 2022, 12(8), 948; https://doi.org/10.3390/min12080948 - 28 Jul 2022
Cited by 16 | Viewed by 4568
Abstract
The growing demand for rare earth elements (REE) driven by their applications in modern technologies has caused the need to search for alternative sources of these elements as their extraction from traditional deposits is limited. A potential source of light rare earth elements [...] Read more.
The growing demand for rare earth elements (REE) driven by their applications in modern technologies has caused the need to search for alternative sources of these elements as their extraction from traditional deposits is limited. A potential source of light rare earth elements (LREE) may be the monazite present in the mining waste generated in the Bagre-Nechí mining district in Colombia due to the processing of sands containing alluvial gold. Consequently, in this research, a systematic evaluation has been carried out for the extraction of Ce, La, and Nd from a leach liquor obtained from monazite present in alluvial gold mining tailings. The leaching process carried out with HCl indicated the recovery of approximately 90% of La and Nd and 60% of Ce; the solvent extraction tests of these elements showed that increasing the contact time and pH of the leaching liquor positively affects the extraction of lanthanum, cerium, and neodymium, achieving extractions close to 100% with D2EHPA and to a lesser extent with Cyanex572. McCabe–Thiele diagrams for extraction with D2EHPA indicated the requirement of three stages for the extraction of Ce, La and Nd. Full article
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