Minerals

23 pages, 4396 KiB

Open AccessReview

Polymer/Clay Nanocomposites as Advanced Adsorbents for Textile Wastewater Treatment

by Adel Mokhtar, Boubekeur Asli, Soumia Abdelkrim, Mohammed Hachemaoui, Bouhadjar Boukoussa, Mohammed Sassi, Gianluca Viscusi and Mohamed Abboud

Minerals 2024, 14(12), 1216; https://doi.org/10.3390/min14121216 - 28 Nov 2024

Abstract

This review explores the removal of textile dyes from wastewater using advanced polymer/clay composites. It provides an in-depth analysis of the chemical and physical properties of these composites, emphasizing how the combination of polymers and clays creates a synergistic effect that significantly improves [...] Read more.

This review explores the removal of textile dyes from wastewater using advanced polymer/clay composites. It provides an in-depth analysis of the chemical and physical properties of these composites, emphasizing how the combination of polymers and clays creates a synergistic effect that significantly improves the efficiency of dye removal. The structural versatility of the composites, derived from the interaction between the layered clay sheets and the flexible polymer matrices, is detailed, showcasing their enhanced adsorption capacity and catalytic properties for wastewater treatment. The review outlines the key functional groups present in both polymers and clays, which are crucial for binding and degrading a wide range of dyes, including acidic, basic, and reactive dyes. The role of specific interactions, such as hydrogen bonding, ion exchange, and electrostatic attractions between the dye molecules and the composite surface, is highlighted. Moreover, the selection criteria for different types of clays such as montmorillonite, kaolinite, and bentonite and their modifications are examined to demonstrate how structural and surface modifications can further improve their performance in composite materials. Various synthesis methods for creating polymer/clay composites, including in situ polymerization, solution intercalation, and melt blending, are discussed. These fabrication techniques are evaluated for their ability to control particle dispersion, optimize interfacial bonding, and enhance the mechanical and chemical stability of the composites. Furthermore, the review introduces advanced characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), to help researchers assess the morphological, structural, and thermal properties of the composites, aligning these features with their potential application in dye removal. Additionally, the review delves into the primary mechanisms involved in the dye removal process, such as adsorption, photocatalytic degradation, and catalytic reduction. It also provides an overview of the kinetic and thermodynamic models commonly used to describe the adsorption processes in polymer/clay composites. The environmental and operational factors influencing the efficiency of dye removal, such as pH, temperature, and composite dosage, are analyzed in detail, offering practical insights for optimizing performance under various wastewater conditions. In conclusion, this review not only highlights the promising potential of polymer/clay composites for textile dye removal but also identifies current challenges and future research directions. It underscores the importance of developing eco-friendly, cost-effective, and scalable solutions to address the growing concerns related to water pollution and sustainability in wastewater management. Full article

(This article belongs to the Special Issue Environmental Pollution and Assessment in Mining Areas)

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16 pages, 5383 KiB

Open AccessArticle

Experimental Study on the Preparation of Cementitious Materials Through the Activation of Lead—Zinc Tailings

by Xu Wu, Xiuping Xu, Shuqin Li, Xiangmei Li, Dejian Pei, Xiaojun Yang, Xiankun Yu and Xiaoman Zhu

Minerals 2024, 14(12), 1215; https://doi.org/10.3390/min14121215 - 28 Nov 2024

Abstract

The pozzolanic activity of lead–zinc tailings (LZTs) was enhanced through mechanical grinding, enabling the preparation of a lead–zinc tailing based composite cementitious material (LZTCC) by combining LZTs with ground granulated blast furnace slag (GGBS), steel slag (SS), and desulfurized gypsum (DG). The compressive [...] Read more.

The pozzolanic activity of lead–zinc tailings (LZTs) was enhanced through mechanical grinding, enabling the preparation of a lead–zinc tailing based composite cementitious material (LZTCC) by combining LZTs with ground granulated blast furnace slag (GGBS), steel slag (SS), and desulfurized gypsum (DG). The compressive strength of LZTCC was evaluated under varying water–cement ratios (W/C) and LZTs dosages. The hydration mechanism was studied via phase composition and microstructural analyses of hydration products. The results revealed that the 28-day pozzolanic activity of LZTs improved to 76% after 2 h of mechanical grinding. LZTCC formulated with 60% LZTs, 22% GGBS, 8% SS, and 10% DG achieved compressive strengths of 13.8 MPa at 7 days and 15.7 MPa at 28 days under a W/C ratio of 0.4. XRD and SEM characterization demonstrated that AFt and amorphous C-S-H gel, along with the unreacted LZT particles, contributed to the overall microstructure, while the former two phases played a significant role in the strength development of LZTCC mortar due to their cementitious reactivity. Heavy metal pollution levels were minimized throughout the process, and the research results could provide a scientific basis for the harmless treatment and resource utilization of LZTs. Full article

(This article belongs to the Special Issue Metallurgy Waste Used for Backfilling Materials)

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11 pages, 2525 KiB

Open AccessArticle

Investigation of the Testing Method of Softening–Melting Properties of Iron-Bearing Materials

by Kai Fan, Xin Jiang, Xin Zhang, Qingyu Wang, Qiangjian Gao, Haiyan Zheng and Fengman Shen

Minerals 2024, 14(12), 1214; https://doi.org/10.3390/min14121214 - 28 Nov 2024

Abstract

The softening–melting properties of iron-bearing materials play a crucial role in the reduction process in the lumpy zone in the blast furnace (BF) and affect the height, thickness, and shape of the cohesive zone, as well as gas permeability in the BF. A [...] Read more.

The softening–melting properties of iron-bearing materials play a crucial role in the reduction process in the lumpy zone in the blast furnace (BF) and affect the height, thickness, and shape of the cohesive zone, as well as gas permeability in the BF. A novel softening–melting method was developed based on actual BF production practices, which consistently matches the reduction index and metallization degree observed in actual BF operations compared to the conventional methods. Under the novel softening–melting testing method, the characteristic temperatures (T₄₀ and T_S) increase by about 5 °C and 49 °C, respectively, compared to the conventional method. Additionally, the permeability index (S) of the sinter in the novel method is about 707 kPa·°C lower compared to the conventional method. Clearly, the novel method results in higher softening–melting characteristic temperatures for iron-bearing materials compared to the traditional method, more closely matching actual BF conditions. This approach can provide valuable insights for improving gas permeability and enhancing the reduction process of iron-bearing materials in the BF. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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17 pages, 2713 KiB

Open AccessArticle

Mineral Deposition on the Rough Walls of a Fracture

by Nathann Teixeira Rodrigues, Ismael S. S. Carrasco, Vaughan R. Voller and Fábio D. A. Aarão Reis

Minerals 2024, 14(12), 1213; https://doi.org/10.3390/min14121213 - 28 Nov 2024

Abstract

Modeling carbonate growth in fractures and pores is important for understanding carbon sequestration in the environment or when supersaturated solutions are injected into rocks. Here, we study the simple but nontrivial problem of calcite growth on fractures with rough walls of the same [...] Read more.

Modeling carbonate growth in fractures and pores is important for understanding carbon sequestration in the environment or when supersaturated solutions are injected into rocks. Here, we study the simple but nontrivial problem of calcite growth on fractures with rough walls of the same mineral using kinetic Monte Carlo simulations of attachment and detachment of molecules and scaling approaches. First, we consider wedge-shaped fracture walls whose upper terraces are in the same low-energy planes and show that the valleys are slowly filled by the propagation of parallel monolayer steps in the wedge sides. The growth ceases when the walls reach these low-energy configurations so that a gap between the walls may not be filled. Second, we consider fracture walls with equally separated monolayer steps (vicinal surfaces with roughness below 1 nm) and show that growth by step propagation will eventually clog the fracture gap. In both cases, scaling approaches predict the times to attain the final configurations as a function of the initial geometry and the step-propagation velocity, which is set by the saturation index. The same reasoning applied to a random wall geometry shows that step propagation leads to lateral filling of surface valleys until the wall reaches the low-energy crystalline plane that has the smallest initial density of molecules. Thus, the final configurations of the fracture walls are much more sensitive to the crystallography than to the roughness or the local curvature. The framework developed here may be used to determine those configurations, the times to reach them, and the mass of deposited mineral. Effects of transport limitations are discussed when the fracture gap is significantly narrowed. Full article

(This article belongs to the Special Issue Mineral Dissolution and Precipitation in Geologic Porous Media)

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19 pages, 1871 KiB

Open AccessArticle

Recovery of Metals from Titanium Ore Using Solvent Extraction Process: Part 1—Transition Metals

by Nelson Kiprono Rotich, Irena Herdzik-Koniecko, Tomasz Smolinski, Paweł Kalbarczyk, Marcin Sudlitz, Marcin Rogowski, Hagen Stosnach and Andrzej G. Chmielewski

Minerals 2024, 14(12), 1212; https://doi.org/10.3390/min14121212 - 28 Nov 2024

Abstract

Solvent extraction of metals from Ti ore was investigated with a view of enhancing extraction yields by changing the concentration of the ligands, the rate of mixing, the pH, and the temperature of the solution. Norwegian Ti ore was leached with 5M HNO [...] Read more.

Solvent extraction of metals from Ti ore was investigated with a view of enhancing extraction yields by changing the concentration of the ligands, the rate of mixing, the pH, and the temperature of the solution. Norwegian Ti ore was leached with 5M HNO₃ alongside 10% ascorbic acid to obtain a pregnant solution containing transition metals and some rare earth elements (REEs). Part Two of the study will address the recovery of the REEs in the ore. The elemental analysis of solid and aqueous samples was done by two models of total reflection X-ray fluorescence spectrometers (S2 PICOFOX, Bruker Corporation, Berlin, Germany; and T-STAR, Bruker Corporation, Berlin, Germany). The same analysis was repeated using an inductively coupled plasma-mass spectrometer (Perkin Elmer Sciex ELAN DRC II, Perkin Elmer, Waltham, MA, USA). The extraction process and parameters were examined by ICP-MS. The extraction efficiencies were studied under different conditions through the use of various concentrations of ligands at different pHs, temperatures, and mixing rates of the solution. At pH 1.0, 22.5 °C, and a mixing rate of 1400 rpm, the selectivity of 150 g/L trioctyl methyl ammonium chloride (Aliquat 336) was 99% Ti⁴⁺, 94% V⁴⁺, and 82% Hf⁴⁺, while 99% of Co²⁺ was recovered at pH 0.8. The extraction efficiency of triethyl phosphate (10% TEP) was 58% Cu²⁺, 68% Mn²⁺, and 63% V⁴⁺ at 55 °C, 1400 rpm, and without a pH change. Tributyl phosphate (10% TBP) was able to retrieve 87% Cu²⁺ and 78% Zn²⁺ at pH 1.3, 1400 rpm, and 22.5 °C, and 80% Ti⁴⁺ at pH 1.2. A 10% solution of 2,4,6-tris (allyloxy)-1,3,5-triazine (TAOT) demonstrated 61% Mn²⁺ and 56% Hf⁴⁺ extraction at pH 1.3, 22.5 °C, and 1400 rpm. Under the same conditions, 10% methyl salicylate (MS) was able to recover 56% Hf⁴⁺ at pH 1.3. Using 1400 rpm, di (2-ethylhexyl) phosphoric acid (10% D2EHPA) was found to selectively extract 87% Hf⁴⁺ at 22.5 °C without a pH change, and around 99% Co²⁺, Ti⁴⁺, and Fe²⁺ at pH 1.3. This study provides valuable insights into optimizing solvent extraction conditions for transition metals’ recovery and serves as a precursor to future research on the extraction of REEs from Ti ores. This process is relevant from the environmental and economic perspectives since it provides the best approach to recycling metals to reduce the rate of raw ore mining. Full article

(This article belongs to the Special Issue Characterization of Minerals and Raw Materials Resources Replenishment)

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The findings were obtained from analyzing the aqueous phases produced by leaching Ti. The analysis was performed before solvent extraction to assess the sample’s composition. Full article ">Figure 2
The results show the application of the S2 PICOFOX TXRF spectrometer to measure Ti ore samples leached by nitrate solution. Full article ">Figure 3
The spectrum displaying the outcome from the T-STAR Mo X-ray tube used to measure the Ti ore dissolved in nitrate solution. Full article ">Figure 4
The spectrum demonstrates the outcome from the W-Bremsstrahlung X-ray tube used to measure the Ti ore leached using nitrate solution. Full article ">Figure 5
The outcomes from TXRF ((A)—T-STAR and (B)—S2 PICOFOX) assessments on the aqueous phases produced by leaching Ti ore. The analysis was done before the solvent extraction stage. Full article ">Figure 6
The recovery of the metals from the nitrate solution at different concentrations of the ligands. (A) Extraction of Hf, Ti, and Fe using different concentrations of D2EHPA; (B) Recovery of Co and Hf using different concentrations of MS; (C) Recovery of Co, Cu, Mn, Zn, V, Ni, and Fe using different concentrations of TEP; (D) Recovery of Co, Hf, Cu, Mn, V and Ni using different concentrations of Aliquat 336; (E) Extraction of Hf, Cu, Mn, Zn and Ni using different concentrations of TBP; (F) Recovery of Co, Hf, Cu, Mn, and Zn utilizing different concentrations of TAOT. The metal recovery by each extractant improved with increasing ligand concentration, attributable to a higher number of binding sites. Full article ">Figure 7
The dependence of the extraction efficiencies on pH changes of the nitrate solutions. (A) Extracting Co, Hf, V, and Ti using 150 g/L of Aliquat 336 at pH values ranging from 0.8 to 1.3; (B) Recovering Co, Hf, Cu, Mn, and V with 10% TEP at different pH levels ranging from 0.8 to 1.3; (C) Recovering Co, Mn, Ti, Ni, and Fe using 10% D2EHPA at varying pH values ranging from 0.8 to 1.3; (D) Recovering Co and Hf with 10% MS at different pH levels ranging from 0.8 to 1.3; (E) Using 10% TAOT to recover Co, Hf, Cu, and Mn at different pH values ranging from 0.8 to 1.3; (F) Recovering Co, Cu, Zn, Ti, and Fe with 10% TBP at various pH values ranging from 0.8 to 1.3. Each ligand demonstrated distinct extraction efficiencies with pH change. Full article ">Figure 8
The influence of the temperature on the extraction of the metals from the nitrate solutions of Ti ore. (A) Extraction of Mn, V, and Ni using 2 to 10% MS at 35, 45 and 55 °C; (B) Recovery of Hf, Ti and Fe using 2 to 10% D2EHPA at 35, 45 and 55 °C; (C) Extracting Hf, Cu, Mn, and Zn utilizing 30 to 150 g/L of Aliquat 336 at 35, 45 and 55 °C; (D) Extraction of Cu, V, and Mn using 2 to 10% TEP at 35, 45 and 55 °C; (E) Extraction of Cu, Zn, Fe, and Mn using 2 to 10% TBP at 35, 45 and 55 °C; (F) Recovering Hf, Mn, V, Cu, Zn, Ni and Fe using 2 to 10% TAOT at 35, 45 and 55 °C. The ligands exhibited varying extraction efficiencies for different metal ions, with recovery rates generally improving at higher solution temperatures. Full article ">Figure 9
The recovery of the metals at different mixing rates of the solutions. (A) Extraction of Co, Zn, and Cu using 2 to 10% TAOT at mixing rates of 250, 600, and 1000 rpm; (B) Recovery of Cu and Zn with 30 to 150 g/L of Aliquat 336 at mixing rates of 250, 600, and 1000 rpm; (C) Extracting Cu, Zn, Mn, and Ni using 2 to 10% TBP at mixing rates of 250, 600, and 1000 rpm; (D) Extracting Co and Hf with 2 to 10% MS at mixing rates of 250, 600, and 1000 rpm; (E) Extracting Fe, Ti, and Hf using 2 to 10% D2EHPA at mixing rates of 250, 600, and 1000 rpm; (F) Extracting Zn, V, and Ni with 2 to 10% TEP at mixing rates of 250, 600, and 1000 rpm. The ligands showed varying extraction efficiencies for different metal ions, with higher mixing rates resulting in improved recoveries. Full article ">

17 pages, 1952 KiB

Open AccessArticle

Assessment of Mercury Uptake by Plants in Former Cinnabar Mining Areas

by Milan Bauštein, Jiřina Száková, Luka Stefanović, Jana Najmanová, Jiřina Sysalová and Pavel Tlustoš

Minerals 2024, 14(12), 1211; https://doi.org/10.3390/min14121211 - 28 Nov 2024

Abstract

Assessment of the plant’s ability to take up mercury (Hg) from polluted soil was affected by location, plant family, and species in two former cinnabar mining areas in the Czech Republic. At each location, seven sampling points were marked out in the vicinity [...] Read more.

Assessment of the plant’s ability to take up mercury (Hg) from polluted soil was affected by location, plant family, and species in two former cinnabar mining areas in the Czech Republic. At each location, seven sampling points were marked out in the vicinity of former shafts and dumpsites connected to the mining activity, where representative soil samples and dicotyledonous plants were collected. The individual locations were characterized by specific plant communities, where, in most cases, different plant species were found within one family at both locations. The total Hg content in the soil, as well as gaseous elemental mercury (GEM_soil-air), confirmed elevated levels of this element in the mining-affected environment, with high variability of the data. The low Hg accumulation ability of plants, especially the low root–shoot translocation in most of the plant species, indicated the predominant occurrence of excluders. Among the families, the results showed the exceptional position of the Fabaceae family regarding soil Hg pollution, as the highest Hg content in both shoots and roots was determined for Onobrychis viciifolia. Therefore, the behavior of Fabaceae plants in polluted soil, the mechanisms of their tolerance to high Hg content, and their Hg accumulation ability deserve further research. Full article

(This article belongs to the Special Issue Geochemical Characteristics and Contamination Risk Assessment of Soil)

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The total Hg contents in the roots and shoots of plants at both locations, regardless of plant species and family; n = 54 for Jedová Hora, and n = 36 for the Horní Luby location. Horizontal lines drawn inside the boxes indicate the median, x indicates the average, and the points outside the whisker boundaries are outliers. The boxplots marked by the same letter do not significantly differ at p < 0.05. Full article ">Figure 2
The total Hg contents in the roots and shoots of plants at the Jedová Hora location according to the individual plant families; n = 54. Horizontal lines drawn inside the boxes indicate the median, x indicates the average, and the points outside the whisker boundaries are outliers. Full article ">Figure 3
The total Hg contents in roots and shoots of plants at the Horní Luby location according to the individual plant families; n = 36. Horizontal lines drawn inside the boxes indicate the median, x indicates the average, and the points outside the whisker boundaries are outliers. Full article ">Figure 4
The BAF values of plants at both locations, regardless of the plant species and family; n = 54 for Jedová Hora, and n = 36 for the Horní Luby location. Horizontal lines drawn inside the boxes indicate the median, x indicates the average, and the points outside the whisker boundaries are outliers. The boxplots marked by the same letter did not significantly differ at p < 0.05. Full article ">Figure 5
The TF values of plants at both locations, regardless of the plant species and family; n = 54 for Jedová Hora, and n = 36 for the Horní Luby location. Horizontal lines drawn inside the boxes indicate the median, x indicates the average, and the points outside the whisker boundaries are outliers. The boxplots marked by the same letter did not significantly differ at p < 0.05. Full article ">

16 pages, 6805 KiB

Open AccessArticle

Five Years of Leaching Experiments to Evaluate Land Spreading of a Modified Bauxite Residue Before and After Treatment of Acid Mine Drainage: Sand or Soil Capping and Revegetation

by Patricia Merdy, Alexandre Parker, Chen Chen and Pierre Hennebert

Minerals 2024, 14(12), 1210; https://doi.org/10.3390/min14121210 - 27 Nov 2024

Abstract

The global generation of bauxite residue necessitates environmentally responsible disposal strategies. This study investigated the long-term (5-year) behavior of bauxite residue whose pH was lowered to 8.5, called modified bauxite residue (MBR), using lysimeters to test various configurations: raw MBR or used MBR [...] Read more.

The global generation of bauxite residue necessitates environmentally responsible disposal strategies. This study investigated the long-term (5-year) behavior of bauxite residue whose pH was lowered to 8.5, called modified bauxite residue (MBR), using lysimeters to test various configurations: raw MBR or used MBR (UMBR) previously applied for acid mine drainage remediation, sand or soil capping, and revegetation. Throughout the experiment and across all configurations, the pH of the leachates stabilized between 7 and 8 and their salinity decreased. Their low sodium absorption ratio (SAR) indicated minimal risk of material clogging and suitability for salt-tolerant plant growth. Leaching of potentially toxic elements, except vanadium, decreased rapidly after the first year to low levels. Leachate concentrations consistently remained below LD50 for Hyalella azteca and were at least an order of magnitude lower by the experiment’s end, except for first-year chromium. Sand capping performed poorly, while revegetation and soil capping slightly increased leaching, though these were negligible given the low final leaching levels. Revegetated MBR shows promise as a suitable and sustainable solution for managing bauxite residues, provided the pH is maintained above 6.5. This study highlights the importance of long-term assessments and appropriate management strategies for bauxite residue disposal. Full article

(This article belongs to the Special Issue Geochemical Characteristics and Contamination Risk Assessment of Soil)

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21 pages, 9812 KiB

Open AccessArticle

A Fuzzy Gold Mineral Prediction Model Integrating with Knowledge-Driven and Data-Driven: A Case Study of the Hatu Region in Xinjiang, China

by Yajie Feng, Yongzhi Wang, Cheng Wang, Jiangtao Tian, Shibo Wen, Yanbin Zhou and Yigao Cheng

Minerals 2024, 14(12), 1209; https://doi.org/10.3390/min14121209 - 27 Nov 2024

Abstract

As mineral resources become increasingly scarce, the search for potential ore deposits presents a significant challenge in geological exploration. Subjective factors often constrain traditional knowledge-driven approaches, while purely data-driven methods may overlook the geological significance of data relationships, potentially compromising the accuracy and [...] Read more.

As mineral resources become increasingly scarce, the search for potential ore deposits presents a significant challenge in geological exploration. Subjective factors often constrain traditional knowledge-driven approaches, while purely data-driven methods may overlook the geological significance of data relationships, potentially compromising the accuracy and reliability of predictions. To address these issues, this study proposes a novel mineral prediction model that integrates fuzzy comprehensive evaluation with both knowledge-driven and data-driven approaches (FCEKDD), resulting in an optimized comprehensive mineral prediction model based on multi-source geoscience data. This model establishes comprehensive exploration indicators based on expert knowledge and quantitatively assesses these indicators through fuzzy evaluation methods to evaluate mineralization potential, thereby delineating exploration targets within the study area. Ultimately, a three-layer predictive framework is constructed using the C-A fractal method. Experimental results indicate that 57.1% of known mineral points are within the primary prediction zone, thus demonstrating the model’s high predictive accuracy. Comparisons with a random forest model reveal that the FCEKDD model has advantages in addressing geoscience data uncertainty and interpreting geological phenomena. This research validates the reliability and applicability of the proposed model in mineral exploration mapping, providing an effective solution for future mineral resource exploration. Full article

(This article belongs to the Section Mineral Exploration Methods and Applications)

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12 pages, 2307 KiB

Open AccessArticle

Experimental Study on the Influence of Rotational Speed on Grinding Efficiency for the Vertical Stirred Mill

by Biliang Tang, Bo Cheng, Xianzhou Song, Haonan Ji, Yijiang Li and Zhaohua Wang

Minerals 2024, 14(12), 1208; https://doi.org/10.3390/min14121208 - 27 Nov 2024

Abstract

The rotational speed of the agitator is one of the important parameters that affect the grinding efficiency of the vertical stirred mill. Increasing the speed will improve the grinding effect, but it will increase energy consumption, and determining a reasonable speed setting is [...] Read more.

The rotational speed of the agitator is one of the important parameters that affect the grinding efficiency of the vertical stirred mill. Increasing the speed will improve the grinding effect, but it will increase energy consumption, and determining a reasonable speed setting is a system issue. The effects of different speeds on energy consumption, product particle size, and grinding efficiency were analyzed in this study. An experimental vertical stirred mill was used to grind iron ore, and five different speed parameters from 175 rpm to 350 rpm were set as variables. It was found that increasing the rotational speed will increase the grinding effect, but it will trigger more energy consumption. A new evaluation index to comprehensively reflect the grinding efficiency of the mill, which was defined as the ability of a mill to grind the same product per unit of time and energy consumption, was proposed. The grinding efficiency was calculated when the particle size of iron ore powder decreased to −45, −38, and −28 μm at different speeds. It can be seen that the growth rate of energy consumption is faster than that of the percentage of particle size, which leads to a continuous decrease in grinding efficiency with the increase in rotational speed. If high processing capacity is pursued within a certain period of time, high speed can be chosen, but it will result in energy loss. On the contrary, the low speed can be chosen, if considering grinding economy. Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation: 3rd Edition)

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Experimental prototype and internal structure of the cylinder: (a) experimental prototype; (b) schematic diagram of the internal structure of the cylinder. Full article ">Figure 2
Particle size distribution of feed samples. Full article ">Figure 3
Experiment torque of Group A during 30 min. Full article ">Figure 4
Relationship between the torque and speed of the agitator. Full article ">Figure 5
The energy consumption of the mill: (a) the variation law of energy consumption over time; (b) the variation law of energy consumption over the speed of the agitator. Full article ">Figure 6
The variation law of particle size over various times and speeds: (a) −45 μm; (b) −38 μm (c) −28 μm; (d) particle size of P80. Full article ">Figure 7
The variation law of energy consumption with rotational speed when the particle size reaches the same percentage. Full article ">Figure 8
The variation law of grinding efficiency with rotational speed: (a) −45 μm; (b) −38 μm; (c) −28 μm. Full article ">Figure 9
The variation law of energy consumption, percentage of particle size, and grinding efficiency with rotational speed. Full article ">

15 pages, 10534 KiB

Open AccessArticle

Genetic Type and Formation Evolution of Mantle-Derived Olivine in Ultramafic Xenolith of Damaping Basalt, Northern North China Block

by Cun Zhang, Fan Yang, Zengsheng Li, Leon Bagas, Lu Niu, Xinyi Zhu and Jianjun Li

Minerals 2024, 14(12), 1207; https://doi.org/10.3390/min14121207 - 27 Nov 2024

Abstract

Olivine in deep-seated ultramafic xenoliths beneath the North China Block serves as a crucial proxy for decoding the compositions, properties, and evolution of the lithospheric mantle. Here, we conduct an investigation on olivine (including gem-grade) hosted in ultramafic xenoliths from Damaping basalt in [...] Read more.

Olivine in deep-seated ultramafic xenoliths beneath the North China Block serves as a crucial proxy for decoding the compositions, properties, and evolution of the lithospheric mantle. Here, we conduct an investigation on olivine (including gem-grade) hosted in ultramafic xenoliths from Damaping basalt in the northern part of the North China Block. This contribution presents the results from petrographic, Raman spectroscopic, and major and trace elemental studies of olivine, with the aim of characterising the formation environment and genetic type of the olivine. The analysed olivine samples are characterised by high Mg# values (close to 91%) possessing refractory to fertile features and doublet bands with unit Raman spectra beams of 822 and 853 cm⁻¹, which are indicative of a forsterite signature. Major and trace geochemistry of olivine indicates the presence of mantle xenolith olivine. All the analytical olivine assays ≤0.1 wt % CaO, ~40 wt % SiO₂, and ≤0.05 wt % Al₂O₃. Furthermore, olivine displays significantly different concentrations of Ti, Y, Sc, V, Co, and Ni. The Ni/Co values in olivine range from 21.21 to 22.98, indicating that the crystallisation differentiation of basic magma relates to oceanic crust recycling. The V/Sc values in mantle/xenolith olivine vary from 0.54 to 2.64, indicating a more oxidised state of the mantle. Rare earth element (REE) patterns show that the LREEs and HREEs of olivine host obviously differentiated characteristics. The HREE enrichments of olivine and the LREE depletion of clinopyroxene further assert that the mantle in the Damaping area underwent partial melting. The wide variations of Mg# values in olivine and the Cr# values in clinopyroxene, along with major element geochemistry indicate transitional characteristics of different peridotite xenoliths. This is possibly indicative of a newly accreted lithospheric mantle interaction with an old lithospheric mantle at the time of the basaltic eruption during the Paleozoic to Cenozoic. Full article

(This article belongs to the Section Mineral Deposits)

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31 pages, 13140 KiB

Open AccessArticle

Transformation of Mackinawite to Interlayered Greigite-Pyrrhotite and Pyrite in the Gaoping Submarine Canyon Sediments off Southwestern Taiwan

by Ko-Chun Huang and Wei-Teh Jiang

Minerals 2024, 14(12), 1206; https://doi.org/10.3390/min14121206 - 26 Nov 2024

Abstract

Iron monosulfides and neoformed pyrite below the sulfate–methane transition zone (SMTZ) of rapidly accumulating turbiditic sediments from the Gaoping submarine canyon off southwestern Taiwan were examined by SEM-EDS-EBSD, HRTEM, and HAADF STEM to investigate their microstructural characteristics and processes of formation and transformation. [...] Read more.

Iron monosulfides and neoformed pyrite below the sulfate–methane transition zone (SMTZ) of rapidly accumulating turbiditic sediments from the Gaoping submarine canyon off southwestern Taiwan were examined by SEM-EDS-EBSD, HRTEM, and HAADF STEM to investigate their microstructural characteristics and processes of formation and transformation. Within a few meters below the SMTZ, mackinawite (Mkw) is largely replaced by interlayered greigite-pyrrhotite (Grg-Po) with {111}_Grg//{001}_Po and ⟨110⟩_Grg//⟨110⟩_Po, followed by pyrite neoformation in clusters of disseminated matrix grains consisting of coalescing pyrite microcrystals, arrays of polycrystalline interlayer pyrite grains between the cleavage planes of layer silicates, with each grain’s core having inclusions of interlayered Grg-Po locally containing relict Mkw, and amassed pyrite microcrystals on the surface of porous interlayered Grg-Po micronodules. In the deeper sediments, neoformed pyrite is absent and Mkw is largely preserved, with partial replacement by interlayered Grg-Po having an overall topotactic relationship of ⟨110⟩_Grg//⟨110 ⟩_Po//⟨100⟩_Mkw and {111}_Grg//(001)_Po//~{011}_Mkw and a sharp reaction front without transitional profiles. The mineral grain boundaries and structural discontinuities with Mkw resulting from extensive interlayering between Grg {111} cubic close-packed segments and Po {001} hexagonal close-packed layers could serve as conduits for fluid flow and mass transport to drive the replacement reaction. The conversion of Mkw to metastable interlayered Grg-Po is inferred to occur through interface-coupled dissolution–reprecipitation processes associated with partial oxidation while the partial replacement of interlayered Grg-Po ± minor relict Mkw by pyrite microcrystals with irregular grain boundaries and orientations probably occurred via a dissolution–precipitation mechanism. Mkw could be initially formed by sulfate reduction driven by anaerobic oxidation of methane in reactive iron-rich sediments in paleo-SMTZs and subsequently transformed into interlayered Grg-Po followed by pyrite neoformation in the sulfidization front below the SMTZ or recent SMTZs in the Gaoping submarine canyon sediments. Full article

(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)

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Figure 1
Sampling location of the MD178-10-3291 sediment core on the west bank of the Gaoping submarine canyon in the lower-slope domain offshore SW Taiwan. DF = the deformation front; LSD = the low-slope domain; USD = the upper-slope domain; OOST = the out-of-sequence thrust; GWR = the Good Weather ridge; FLR = the Fangliao ridge. Full article ">Figure 2
Scanning electron micrographs of (a) a cluster of disseminated pyrite grains (Py) in the sediment matrix and an interlayered Grg-Po (Grg*) micronodule fringed with neoformed pyrite (1434–1439 cmbsf); (b) an enlargement of the small black frame area in (a); (c) arrays of interlayer pyrite grains between the cleavage planes of a chlorite stack (1434–1439 cmsbf); (d) a magnification of interlayered Grg-Po (+ relict Mkw) inclusions (Grg* + Mkw) in the core of a pyrite grain in the frame area in (c); (e) an iron-monosulfide micronodule consisting of dense aggregates of Mkw in association with lesser interlayered Grg-Po and relict layer silicates (2037–2042 cmbsf); and (f) an enlargement of the framed area in (e) exhibiting interweaved microtextures. The areas selected for EBSD analyses or FIB-TEM specimen preparation are indicated in (a,d,f). Full article ">Figure 3
EBSD phase and inverse pole figure (IPF) maps of (a,b) disseminated matrix pyrite grains, (c,d) arrays of interlayer pyrite grains, and (e,f) amassed pyrite microcrystals in a portion of an interlayered Grg-Po micronodule in the 1434–1439 cmbsf sediment. Layer silicate and Grg-dominant areas were unindexed (different gray-scale levels) due to poor EBSD signals. For conciseness, only pyrite was indexed and is displayed in color. Most pyrite grains consist of multiple microcrystals of different crystal orientations implied by different colors in the IPF maps. Color legends for mineral phases in the phase maps and pyrite orientations in the IPF maps are inserted in (a,b), respectively. Py = pyrite; Sd = siderite; Qz = quartz; Ab = albite. Mineral identification was assisted by EDS. Full article ">Figure 4
TEM micrographs of Grg-dominant inclusions in the core of an interlayer pyrite grain in the 1434–1439 cmbsf sediment, illustrating (a) multiple anhedral pyrite crystals (Py) enclosing Grg-dominant interlayered Grg-Po microcrystals (Grg*) and relict chlorite layers (Chl) and (b) infiltrative pyrite growth around a subhedral Grg-dominant crystal (the lower left corner in a) oriented in the 〈001〉Grg zone and a number of small Grg-dominant microcrystals largely elongated along 〈110〉Grg with parallel {001}Grg. Full article ">Figure 5
Electron micrographs of an interlayered Grg-Po microcrystal enclosed within an interlayer pyrite grain at 1434–1439 cmbsf: (a) the subhedral outline of a Grg-dominant composite microcrystal (the upper-right frame of <a href="#minerals-14-01206-f004" class="html-fig">Figure 4</a>a) bordered by {001}Grg faces with a slight elongation along 〈110〉Grg or equivalent directions; (b) the corresponding diffraction pattern having parallel Grg and Po 〈110〉 zones with the Grg <math display="inline"><semantics> <mrow> <mover> <mi>h</mi> <mo>¯</mo> </mover> </mrow> </semantics></math>hh and <math display="inline"><semantics> <mrow> <mover> <mi>h</mi> <mo>¯</mo> </mover> </mrow> </semantics></math>hl reflection rows overlain by the Po 00l and <math display="inline"><semantics> <mrow> <mover> <mi>h</mi> <mo>¯</mo> </mover> </mrow> </semantics></math>hl reflection rows, respectively; (c) {111} lattice-fringe image (frame (c) in (a)) with nonperiodic contrast features; (d) HAADF-STEM image of part of the microcrystal in (a) displaying rhombic domains of Grg framed by relatively bright Po (001) layers parallel to Grg {111}, consistent with an occurrence of interlayered Grg-Po; (e) high-magnification Fourier filtered HAADF-STEM image of the composite microcrystal illustrating rhombic arrays of bright spots corresponding to the projected 〈110〉-parallel edge-sharing octahedral chains of Grg intervened by Po {001} octahedral layers parallel to {111} of the Grg domains; and (f) Fourier filtered HAADF-STEM image (frame (f) in (a)) showing an area with ~0.5 nm {001}Mkw lattice fringes consistent with an enclosure of relict Mkw by interlayered Grg-Po. Full article ">Figure 6
TEM micrographs of part of an iron-monosulfide micronodule in the 1434–1439 cmbsf sediment: (a) the micronodule is associated with microfissures and neoformed pyrite; (b) pyrite neoformation in a fissure of the micronodule (black arrow in a); (c) occurrence of relict phyllosilicate layers (arrowed) and 〈110〉-elongated Grg-Po composite microcrystals in an alternating manner, locally associated with infiltrative growth of neoformed pyrite; (d) the diffraction pattern of an elongated Grg-Po microcrystal (Grg and Po 〈110〉 zones) having <math display="inline"><semantics> <mrow> <mover> <mi>h</mi> <mo>¯</mo> </mover> </mrow> </semantics></math>hh and <math display="inline"><semantics> <mrow> <mover> <mi>h</mi> <mo>¯</mo> </mover> </mrow> </semantics></math>hl reflection rows of Grg superimposed by the 00l and <math display="inline"><semantics> <mrow> <mover> <mi>h</mi> <mo>¯</mo> </mover> </mrow> </semantics></math>hl reflection rows of Po, respectively; (e,f) nonperiodic {111}-parallel contrast features ascribed to the interlayering of Po (001) layers within the Grg-dominant microcrystals. Full article ">Figure 7
Electron micrographs of part of an iron-monosulfide micronodule in the 2037–2042 cmbsf sediment: (a) HAADF-STEM image of an elongated iron-monosulfide aggregate consisting of mackinawite (Mkw) and interlayered Grg-Po (Grg-Po); (b) the elongation of the composite grain parallel to Grg 〈110〉 and mackinawite 〈010〉 as implied by the corresponding diffraction pattern in the Grg 〈110〉 and mackinawite 〈100〉 directions; (c,d) HAADF-STEM images of frames (c,d) in a illustrating zigzag boundaries between mackinawite and interlayered Grg-Po defined by Grg {111} and mackinawite {011} and in part by planar boundaries parallel to Grg and Mkw {001}; (e,f) TEM images of interlayered Grg-Po elongated along 〈110〉Grg with crossed contrast features parallel to Grg {111} and Po (001) in the absence of Mkw. Full article ">Figure 8
Electron micrographs of oriented Mkw and interlayered Grg-Po in an iron-monosulfide micronodule in the 2037–2042 cmbsf sediment: (a) TEM image of the growth microtextures of Mkw and interlayered Grg-Po (Grg*) in a composite grain of the micronodule; (b) the corresponding diffraction pattern with 〈100〉Mkw//〈110〉Grg//〈110〉Po, (001)Mkw//(001)Grg, and (001)Po//{111}Grg; (c,d) 〈100〉-oriented Mkw (frame c in a) having dislocations in {001} lattice fringes in company with 〈110〉-oriented Grg-dominant domains having crossed {111} fringes (frame (d) in (a)) with varied contrast due to oriented growth of intertwined Po (001) layers; (e,f) Fourier filtered HAADF-STEM images of topotactic interfaces between Mkw and interlayered Grg-Po domains. Full article ">Figure 9
Schematic diagram of crystallographic relationships among Mkw, Grg, and Po viewed from [110]Grg, [110]Po, and [100]Mkw with close-packed planes of sulfur atoms (•) labeled by A, B, and C to indicate sulfur stacking sequences. Rhombic domains of Grg consist of ccp planes of sulfur atoms and alternating [110]Grg-projected columns of edge-sharing octahedral sites fully (●) and half (●) occupied by iron, in association with double columns of tetrahedral iron sites (each half occupied by iron) at open rhombuses. Po slabs are composed of hcp planes of sulfur atoms and (001)Po layers of [110]Po-projected edge-sharing octahedral sites fully (●) and partially (●) occupied by iron. Mkw (distorted ccp sulfur) is made up of (001)Mkw tetrahedral iron sheets connected by van der Waals forces. It is important to note the presence of compulsory structural discontinuities between intersecting Po layers and at intersections between Mkw and Grg and Po due to the mixed occurrence of of different sulfur stacking sequences. Full article ">

17 pages, 13556 KiB

Open AccessArticle

Structural Characteristics of E–W-Trending Shear Belts in the Northeastern Dabie Orogen, China: Evidence for Exhumation of High–Ultrahigh-Pressure Rocks

by Yongsheng Wang, Xu Zhang and Qiao Bai

Minerals 2024, 14(12), 1205; https://doi.org/10.3390/min14121205 - 26 Nov 2024

Abstract

The Dabie–Sulu Orogen hosts the largest area of ultrahigh-pressure (UHP) rocks in the world. There is still significant divergence regarding the exhumation process and mechanism of UHP rocks in the Dabie Orogen, which mainly resulted from the erosion of large volumes of rocks [...] Read more.

The Dabie–Sulu Orogen hosts the largest area of ultrahigh-pressure (UHP) rocks in the world. There is still significant divergence regarding the exhumation process and mechanism of UHP rocks in the Dabie Orogen, which mainly resulted from the erosion of large volumes of rocks in the Orogen during the post-collisional stage. Based on detailed field investigations, this study discovered the occurrence of E–W-trending sinistral shear belts that developed on the northeastern Dabie Orogen. These shear belts formed under greenschist facies conditions and are characterized by steep foliation and gentle mineral lineation. E–W-trending shear belts developed in HP rocks with metamorphic ages ranging from 227 to 219 Ma and were cut by the older phase of ductile shear belts of the Tan-Lu Fault Zone, indicating that they were formed around 219–197 Ma. Based on a comprehensive analysis of existing data, it can be concluded that E–W-trending shear belts were formed during the exhumation process of HP–UHP rocks. When HP rocks returned to the shallow crust and the lower UHP rocks continued to move, stress concentration occurred in the HP rocks and further resulted in the formation of E–W-trending shear belts. The development of E–W-trending shear belts indicates that HP–UHP rocks had essentially returned to the shallow crust by the Late Triassic, marking the near completion of the exhumation process. Full article

(This article belongs to the Special Issue Geochemistry and Geochronology of High-Grade Metamorphic Rocks)

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Figure 1
Geological sketch of the northeastern Dabie Orogen. (a) The location of the Central China Orogenic Belt. (b) A simplified tectonic framework of the Dabie Orogen (modified after Xu et al. [<a href="#B25-minerals-14-01205" class="html-bibr">25</a>]). (c) Detailed structural map of the Tongcheng massif. (d) Lower-hemisphere, equal-area stereograms of poles to the mylonitic foliation and plunges of mineral elongation lineation of the E–W-trending and NE–SW-trending shear belts in the northeastern Dabie Orogen. (e) Cross-sections showing tectonic framework of the Dabie Orogen (Section line in (b)). TLF: Tan-Lu Fault Zone; SMF: Shangcheng–Macheng Fault; XMSZ: Xiaotian–Mozitan shear zone; WSF: Wuhe–Shuihou Fault; HMF: Hualiangting–Mituo Fault; TMF: Taihu–Mamiao Fault; XSF: Xishui Fault; XGF: Xiangfan–Guangji Fault. Full article ">Figure 2
Field photos of gneisses and mylonites in the northeastern Dabie Orogen. (a) Development of brittle NE–SW-trending faults in gneisses with flat-lying foliation; (b) steeply chlorite-bearing ultramylonite and (c) granitic mylonite; (d) S-C structures in marble mylonite indicates sinistral shear; (e,f) development of E–W-trending shear zone in gneisses with flat-lying foliation. Full article ">Figure 3
Micrographs of mylonites from the E–W-trending shear belts in the northeastern Dabie Orogen. (a) Broken feldspar and recrystallized quartz; (b) fine-grain recrystallized quartz with a few larger quartz grains; (c) crossed polarizers and (d) single polarizers micrographs of ultramylonite, with banded chlorite, sericite and a few epidotes, with sinistral shear; (e) σ-type feldspar porphyroclasts in the ultramylonite indicating sinistral shear; (f) e-twin of calcite in the marble mylonite. Quartz within rectangular frame for EBSD testing. Qz: quartz; Fsp: feldspar; Pl: plagioclase; Ep: epidote. Full article ">Figure 4
Quartz CPO pattern of mylonites from E–W-trending shear belts in the northeastern Dabie Orogen. Lower-hemisphere, equal-area projection. n: measured grain numbers. X and Z are principal axes of finite strain. Thin sections are parallel with XZ plane. Full article ">Figure 5
Cathodoluminescence images of a selection of the dated zircons from mylonites in the eastern Dabie Orogen. Red circles indicate analytical sites. Full article ">Figure 6
Concordia diagrams and weighted mean ages of zircons from mylonites in the E–W-trending shear belts in the northeastern Dabie Orogen. Full article ">Figure 7
Schematic diagram of tectonic evolution during syn-collisional exhumation and post-collisional uplift. (a) During the Late Triassic to the Early Jurassic, the subducted SCB was exhumed to the shallow crust and resulted in the formation of a fold-and-thrust belt in the northern Yangtze Block and the Hefei foreland basin in the southern NCB. (b) Post-collisional uplift caused rocks overlying the ND unit to be eroded and rebuilt the tectonic framework of the Dabie Orogen. The diamond represents the outcrop location of HP–UHP rocks, and the numbers in parentheses are the ages when these HP–UHP rocks returned to the shallow crust. The dashed lines show the eroded part of units in the Dabie Orogen. Age data are from Liu et al. [<a href="#B10-minerals-14-01205" class="html-bibr">10</a>], Leech et al. [<a href="#B11-minerals-14-01205" class="html-bibr">11</a>], Ayers et al. [<a href="#B31-minerals-14-01205" class="html-bibr">31</a>], and the references therein. Please refer to the manuscript for abbreviated names. Full article ">Figure 8
Schematic model of the formation of E–W-trending shear belts in the northeastern Dabie Orogen during the Late Triassic. To highlight the relationship between the formation of E–W-trending shear belts and the exhumation process of HP–UHP rocks, we neglected other units within the orogen in this figure. Please refer to the manuscript for abbreviated names. Full article ">

51 pages, 6848 KiB

Open AccessReview

Potential Reuse of Ladle Furnace Slag as Cementitious Material: A Literature Review of Generation, Characterization, and Processing Methods

by Noureddine Ouffa, Mostafa Benzaazoua, Romain Trauchessec, Tikou Belem, Yassine Taha and Cécile Diliberto

Minerals 2024, 14(12), 1204; https://doi.org/10.3390/min14121204 - 26 Nov 2024

Abstract

Ladle furnace slag (LFS), a by-product of steel refining, shows a promising reuse pathway as an alternative additive or substitute for Portland cement due to its high alkalinity and similar chemical composition to clinkers. However, LFS is often stored in large, open surface [...] Read more.

Ladle furnace slag (LFS), a by-product of steel refining, shows a promising reuse pathway as an alternative additive or substitute for Portland cement due to its high alkalinity and similar chemical composition to clinkers. However, LFS is often stored in large, open surface areas, leading to many environmental issues. To tackle waste management challenges, LFS can be recycled as supplementary cementitious material (SCM) in many cementitious composites. However, LFS contains some mineral phases that hinder its reactivity (dicalcium silicate (γ-C₂S)) and pose long-term durability issues in the cured cemented final product (free lime (f-CaO) and free magnesia (f-MgO)). Therefore, LFS needs to be adequately treated to enhance its reactivity and ensure long-term durability in the structures of the cementitious materials. This literature review assesses possible LFS treatments to enhance its suitability for valorization. Traditional reviews are often multidisciplinary and explore all types of iron and steel slags, sometimes including the recycling of LFS in the steel industry. As the reuse of industrial by-products requires a knowledge of their characteristics, this paper focuses first on LFS characterization, then on the obstacles to its use, and finally compiles an exhaustive inventory of previously investigated treatments. The main parameters for treatment evaluation are the mineralogical composition of treated LFS and the unconfined compressive strength (UCS) of the final geo-composite in the short and long term. This review indicates that the treatment of LFS using rapid air/water quenching at the end-of-refining process is most appropriate, allowing a nearly amorphous slag to be obtained, which is therefore suitable for use as a SCM. Moreover, the open-air watering treatment leads to an optimal content of treated LFS. Recycling LFS in this manner can reduce OPC consumption, solve the problem of limited availability of blast furnace slag (GGBFS) by partially replacing this material, conserve natural resources, and reduce the carbon footprint of cementitious material operations. Full article

(This article belongs to the Special Issue Metallurgy Waste Used for Backfilling Materials)

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21 pages, 19488 KiB

Open AccessArticle

Influence of Chromite Ore Selection on the Pelletized Oxidative Sintering Process: A South African Case Study

by Yolindi van Staden, Stephanus Petrus du Preez, Johan Paul Beukes, Pieter Gideon van Zyl and Jason Groenewald

Minerals 2024, 14(12), 1203; https://doi.org/10.3390/min14121203 - 26 Nov 2024

Abstract

The smelting of chromite to produce ferrochrome (FeCr) and subsequently, stainless steel, is an energy-intensive carbothermic process. Various countries apply the Outotec FeCr process, which employs oxidative sintering in air to produce mechanically strong chromite pellets. During this process, iron (Fe) is liberated [...] Read more.

The smelting of chromite to produce ferrochrome (FeCr) and subsequently, stainless steel, is an energy-intensive carbothermic process. Various countries apply the Outotec FeCr process, which employs oxidative sintering in air to produce mechanically strong chromite pellets. During this process, iron (Fe) is liberated from the chromite spinel due to the elevated temperatures and oxidative nature of the process. It is well understood that oxidatively altered chromite requires less energy to be smelted when compared to non-oxidized chromite. This study showed that sintered pellets obtained from five South African pellet sintering plants had vastly different oxidative alteration penetrations. Additionally, sintered pellets from the same plant may also vary significantly. It was further shown that ores mined from various locations in South Africa had dissimilar sintering behaviors, suggesting that sintered pellets should be characterized before smelting to determine the extent of oxidative alteration. The benefit of a smelter consuming oxidized ore was also demonstrated by comparing the interaction between oxidized and non-oxidized chromite with a carbon (C) source. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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17 pages, 5681 KiB

Open AccessArticle

Geochemical Anomaly Detection and Pattern Recognition: A Combined Study of the Apriori Algorithm, Principal Component Analysis, and Spectral Clustering

by Mahsa Hajihosseinlou, Abbas Maghsoudi and Reza Ghezelbash

Minerals 2024, 14(12), 1202; https://doi.org/10.3390/min14121202 - 26 Nov 2024

Abstract

This study demonstrates the effectiveness of combining Principal Component Analysis (PCA) and the Apriori algorithm for feature selection, alongside Spectral clustering, to detect geochemical anomalies in Mississippi Valley-Type (MVT) Pb-Zn deposits in western Iran. First, PCA and Apriori enabled the identification of both [...] Read more.

This study demonstrates the effectiveness of combining Principal Component Analysis (PCA) and the Apriori algorithm for feature selection, alongside Spectral clustering, to detect geochemical anomalies in Mississippi Valley-Type (MVT) Pb-Zn deposits in western Iran. First, PCA and Apriori enabled the identification of both syngenetic and epigenetic components, which helped in recognizing elements associated with mineralization. These elements were then modeled using Spectral clustering to detect geochemical anomalies. Unlike traditional methods like k-means, Spectral clustering does not require spherical clusters and is adept at identifying clusters of arbitrary shapes. This made it particularly suitable for analyzing the irregular shapes of geochemical anomalies in the study area. By incorporating Spectral clustering, the method effectively separated geochemical groups, revealing the underlying structure of the data. This was crucial for identifying anomalous geochemical zones and delineating areas with a high potential for Pb-Zn mineralization. The performance of the Spectral clustering algorithm was thoroughly evaluated using the Silhouette Score, the Davies–Bouldin Index, and Dunn Index. Subsampling was employed to assess the algorithm’s stability, providing a comprehensive evaluation of its effectiveness in identifying geochemical anomalies and mapping mineralization potential. Full article

(This article belongs to the Section Mineral Exploration Methods and Applications)

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19 pages, 4401 KiB

Open AccessArticle

Characterization and Processing of Low-Grade Middle Group 2 Chromite Ore by Gravity Shaking Table and a Comparative SLon Magnetic Separation: A Case Study

by Inga Sixhuta, Ashma Singh, Phathutshedzo Khangale, Reinout Meijboom and Mpfunzeni Raphulu

Minerals 2024, 14(12), 1201; https://doi.org/10.3390/min14121201 - 26 Nov 2024

Abstract

Chromite is considered a strategic mineral in the global economy. It is mainly used as an essential raw material in the production of stainless steel and other metal alloys due to its corrosion and heat resistance properties. High-grade chromite resources are gradually depleting; [...] Read more.

Chromite is considered a strategic mineral in the global economy. It is mainly used as an essential raw material in the production of stainless steel and other metal alloys due to its corrosion and heat resistance properties. High-grade chromite resources are gradually depleting; with the increasing chromite demand in metallurgical applications, studies have focused on exploring low-grade and alternative chromite sources. This study proposes a cost-effective processing flowsheet for the low-grade middle group 2 (MG2) chromite layer, a poorly explored chromatite seam within the South African bushveld igneous complex (BIC). The study involved mineralogical characterization followed by gravity and magnetic separation of the low-grade MG2 ore at 18.18% Cr₂O₃. Characterization by XRD and Auto-SEM revealed that the ore mainly consists of pyroxene, chromite, and feldspar, with other minerals in trace quantities. The gravity separation test by shaking table upgraded the chromite (Cr₂O₃) to 42.0% at high chromite recoveries, whereas the laboratory Slon wet high-intensity magnetic separation method (SLon WHIMS) upgraded the chromite in the feed to 42.95% grade at lower chromite recoveries. Desliming the sample before the gravity and magnetic separation tests significantly improved the separation. The magnetic separation tests further demonstrated that chromite within the MG2 layer is sensitive to magnetic separation due to its high iron content. The adapted flowsheet is proposed as a cost-effective flowsheet for processing the low-grade MG2 layer. The flow sheet can be optimized by conducting the SLon WHIMS tests at high intensities followed by fine gravity tests by spiral circuits to maximize the chromite recovery while achieving commercial chromite grades and a Cr:Fe ratio greater than 1.5. Full article

(This article belongs to the Special Issue Mineral Processing Technologies of Low-Grade Ores)

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17 pages, 3229 KiB

Open AccessArticle

Application of Machine Learning for Generic Mill Liner Wear Prediction in Semi-Autogenous Grinding (SAG) Mills

by Yusuf Enes Pural, Tania Ledezma, Marko Hilden, Gordon Forbes, Feridun Boylu and Mohsen Yahyaei

Minerals 2024, 14(12), 1200; https://doi.org/10.3390/min14121200 - 25 Nov 2024

Abstract

This study explores the application of machine learning techniques for predicting generic mill liner wear in semi-autogenous grinding (SAG) mills used in mineral processing. Various models were developed and compared using data from 143 liner measurements across 36 liner cycles from ten different [...] Read more.

This study explores the application of machine learning techniques for predicting generic mill liner wear in semi-autogenous grinding (SAG) mills used in mineral processing. Various models were developed and compared using data from 143 liner measurements across 36 liner cycles from ten different SAG mills. The research initially focused on individual mill modeling, employing simple linear regression, first-order kinetic approach, Multiple Linear Regression (MLR), tree-based methods (Decision Trees, Random Forests, XGBoost), and Multilayer Perceptron (MLP). Results showed that simple linear regression provided sufficient accuracy, with other methods only slightly improving performance. This study then developed a combined model using data from multiple mills. MLR and advanced machine learning techniques were applied for this generic model, with XGBoost emerging as the most successful. In the interpolation scenario involving a mill similar to those in the training data, the XGBoost model achieved a mean absolute percentage error (MAPE) of 5.27%. For the extrapolation scenario, with a mill larger than those in the training set, the MAPE increased slightly to 6.12%. These results demonstrate the potential of machine learning approaches in creating effective generic models for mill liner wear prediction. However, this study also highlights the potential for improving predictive models by incorporating additional key parameters such as liner and ball material properties. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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16 pages, 11454 KiB

Open AccessArticle

Discovery and Geological Significance of Neoproterozoic Bimodal Intrusive Rocks in the Dabie Orogen, China

by Linjing Li, Mingyi Hu, Lingyao Kong, Lin Wang and Qiqi Lyu

Minerals 2024, 14(12), 1199; https://doi.org/10.3390/min14121199 - 25 Nov 2024

Abstract

The Mingshan reservoir of the Dabie Orogen has a number of Neoproterozoic bimodal intrusive rocks. We focused on the zircon U-Pb chronology, Hf isotopes, and bulk-rock geochemistry of these rocks. The results showed the following: (1) The bimodal intrusive rocks mainly consist of [...] Read more.

The Mingshan reservoir of the Dabie Orogen has a number of Neoproterozoic bimodal intrusive rocks. We focused on the zircon U-Pb chronology, Hf isotopes, and bulk-rock geochemistry of these rocks. The results showed the following: (1) The bimodal intrusive rocks mainly consist of monzogranitic gneiss and plagioamphibolite, with zircon U-Pb ages of 785.0 ± 7.1 Ma and 787.3 ± 6.1 Ma, respectively. These ages indicate that they were formed in the late Qingbaikou epoch of the Neoproterozoic era. (2) The monzogranitic gneiss was dominated by peraluminous features and displayed a strong right deviation of REE (rare-earth element) patterns and a negative δEu anomaly. It is enriched in the LILEs (large-ion lithophile elements) Rb, Ba, and K, but slightly depleted in Nb, Sr, P, and Ti, with low 10,000* Ga/Al values, indicating that it is similar to Al-type granite. The plagioamphibolite belongs to the metaluminous, peraluminous series. It has a Mg^# (molar ratio of Mg to Mg + Fe) of 36.1~55.9 and is enriched in the LILEs Rb, Ba, and K, with a slight positive anomaly of Ba, and is depleted in Nb and Sr. (3) The monzogranite shows negative zircon εHf(t) values ranging from −13.4 to −7.2 and a Paleoproterozoic T_DM2(Hf) (two-stage depleted mantle model age) of 1969–2298 Ma. The zircon εHf(t) values and T_DM2(Hf) of the plagioamphibolite were concentrated around 2.9–5.7 and 1257–1410 Ma, respectively. The geochemistry and Hf isotopes show that the monzogranitic gneiss and plagioamphibolite have distinct magmatic sources. The plagioamphibolite formed from mantle and partial continental crustal materials. The monzogranitic gneiss, on the other hand, was formed as a result of the partial melting of the shallow ancient felsic crust caused by mafic rock heating or upwelling. Taking into account regional correlation, the middle Neoproterozoic bimodal intrusive rocks originated in the structural framework of an extensional setting. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

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19 pages, 14784 KiB

Open AccessArticle

Increasing Structural Diversity of the Early Growth Stages in Polynesian Pearls Reveals Biological Stress Suffered by the Grafts

by Jean-Pierre Cuif, Yannicke Dauphin, Marc Gèze, Cedrik Lo, Gergely Nemeth and Christophe Sandt

Minerals 2024, 14(12), 1198; https://doi.org/10.3390/min14121198 - 25 Nov 2024

Abstract

In Polynesian pearls produced using Pinctada margaritifera var. Cumingii, we investigated the structure of the early growth stages, from the nucleus surface up to the first deposition of the black nacre characteristic of this subspecies. Despite simultaneous grafting from the same donor [...] Read more.

In Polynesian pearls produced using Pinctada margaritifera var. Cumingii, we investigated the structure of the early growth stages, from the nucleus surface up to the first deposition of the black nacre characteristic of this subspecies. Despite simultaneous grafting from the same donor oyster and similar cultivation conditions, we observed the deposition of various non-nacreous pre-nacre structures. These unusual microstructures, which precede the return to black nacre, varied from immediate deposition onto the nucleus surface to increasing delays, depending on the graft’s position in the grafting series. Given the similar biological conditions of grafting and cultivation, we suggest that, in line with recent data demonstrating genomic sensitivity to environmental conditions, alterations in the graft cells produced during the increasing waiting period were transmitted to the pearl sacs and the early growth stages of the grafted pearls. Full article

(This article belongs to the Section Biomineralization and Biominerals)

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