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15 pages, 5368 KiB  
Article
Radioiodide Sorption on Natural and Acid-Treated Zeolite
by Petr Belousov, Ekaterina Tyupina, Pavel Kozlov, Yulia Izosimova, Inna Tolpeshta, Tatiana Koroleva, Boris Pokidko, Victoria Krupskaya and Anastasia Rumyantseva
Minerals 2025, 15(5), 494; https://doi.org/10.3390/min15050494 - 7 May 2025
Viewed by 519
Abstract
This work is devoted to the study of the effect of acid treatment on the structural and textural properties of natural zeolite and its sorption activity with respect to radioiodide. To carry out the experiments, natural zeolite was treated with nitric acid of [...] Read more.
This work is devoted to the study of the effect of acid treatment on the structural and textural properties of natural zeolite and its sorption activity with respect to radioiodide. To carry out the experiments, natural zeolite was treated with nitric acid of various concentrations at 20 and 90 degrees. The following methods were used to study the samples: XRD, SEM, DTA, XRF, FTIR, BET, and CEC analyses. Experiments on the sorption and desorption of radioiodide were carried out. The obtained results indicate that acid treatment results in the gradual leaching of aluminum from the crystal lattice and a significant increase in the specific surface area and microporosity of the zeolite. At the same time, the morphology of clinoptilolite is not significantly changed. Additional studies have shown that acid treatment leads to the hydrophobization of zeolite channels and the formation of an amorphous aluminosilicate phase, which makes a significant contribution to the increase in the specific surface area and microporosity. It was found that, with an increase in the degree of dealumination of the zeolite, there is an increase in the sorption properties with respect to radioiodide. The maximum values of sorption capacity were obtained after treating the zeolite with a 1 M nitric acid solution at 90 °C. With a further increase in the concentration of acid, critical changes in the structure of the zeolite occur, leading to a sharp decrease in the sorption capacity. Iodide sorption is not associated with physical adsorption in the micropores of the zeolite and the newly formed amorphous phase. The main mechanism of the sorption appears to be the interaction with silanol and bridging hydroxyl groups on the surface of the zeolite and the amorphous aluminosilicate phase. Full article
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12 pages, 7594 KiB  
Article
Hydrothermal Synthesis of Kaolinite Group Minerals
by Tatiana Koroleva, Boris Pokidko, Ivan Morozov, Anastasia Nesterenko, Sofya Kortunkova, Mikhail Chernov, Dmitry Ksenofontov and Victoria Krupskaya
Materials 2025, 18(3), 472; https://doi.org/10.3390/ma18030472 - 21 Jan 2025
Cited by 2 | Viewed by 937
Abstract
Synthetic alumosilicates are used in many industrial applications, and the synthesis of clay minerals under different conditions allows us to understand the conditions of their formation. This study examined the impact of varying silica precursors, pH conditions and synthesis durations. Synthetic kaolinite group [...] Read more.
Synthetic alumosilicates are used in many industrial applications, and the synthesis of clay minerals under different conditions allows us to understand the conditions of their formation. This study examined the impact of varying silica precursors, pH conditions and synthesis durations. Synthetic kaolinite group mineral analogues were investigated by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Additionally, the crystallinity index was calculated. The impact of using different silica sources on the structural features of synthetic kaolinite group analogues was revealed. The use of a Nanosil precursor resulted in the formation of highly crystalline kaolinite. The most significant alterations in the course of synthesis were observed at different pH values. The formation of various synthetic analogues of minerals from the kaolinite group was observed: at a high pH, the formation of halloysite with a small admixture of kaolinite was observed. Conversely, the synthesis resulted in the formation of ordered kaolinite at a low pH. The crystallinity index of the resulting synthesized kaolinite analogues rises as the synthesis duration increases, while the quantity of non-crystallized material decreases. The changes in the crystallinity of kaolinite when using different silica precursors are related to the different homogenization of the material that occurs at the stage of alumosilica gel formation. Full article
(This article belongs to the Special Issue Application and Modification of Clay Minerals)
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22 pages, 2762 KiB  
Article
On the Question of Finding Relationship Between Structural Features of Smectites and Adsorption and Surface Properties of Bentonites
by Victoria Krupskaya, Sergey Zakusin, Olga Zakusina, Petr Belousov, Boris Pokidko, Ivan Morozov, Tatiana Zaitseva, Ekaterina Tyupina and Tatiana Koroleva
Minerals 2025, 15(1), 30; https://doi.org/10.3390/min15010030 - 29 Dec 2024
Cited by 1 | Viewed by 1285
Abstract
During the development of the disposal concept in a crystalline massif of the Russian Federation, a question arose regarding the selection of the most suitable types of bentonite for a buffer layer. Data on the composition, structure, surface, and adsorption properties of four [...] Read more.
During the development of the disposal concept in a crystalline massif of the Russian Federation, a question arose regarding the selection of the most suitable types of bentonite for a buffer layer. Data on the composition, structure, surface, and adsorption properties of four promising deposits have been obtained. The correlations between genesis and specific surface area (SSA) revealed in this study indicate that bentonites of volcanogenic-sedimentary origin have lower SSA in comparison with those of sedimentary and hydrothermal origin. The main contribution to the charge of the 2:1 layer is made by isomorphic substitutions in the tetrahedral sheet, which directly affects the sorption properties of bentonites. The influence of smectite structure on adsorption properties have been described. In particular, the dependencies between the layer charge and cation exchange capacity (CEC) have been analyzed. At the same time, the research indicates that, unlike the CEC, the specific surface area of a deposit is determined by its geological history. Special attention is being paid to refining methodological approaches for deriving crystal chemical formulae of smectites, which will be needed in the future for modelling changes in bentonite over a long-term perspective. Full article
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18 pages, 3430 KiB  
Article
Glauconite-Based Nanocomposites with Zn/Cu/B: Multifunctional Micronutrient Fertilizers
by Ivan Khitrin, Prokopiy Maximov, Evan Dasi, Kanipa Ibraeva, Konstantin Ponomarev, Natalia Maximova, Peter Belousov, Alexey Ruban and Maxim Rudmin
Minerals 2025, 15(1), 12; https://doi.org/10.3390/min15010012 - 26 Dec 2024
Cited by 2 | Viewed by 1090
Abstract
The full potential of glauconite-based nanocomposites as micronutrient fertilizers remains underexplored, particularly their interaction with Zn, Cu, and B. Despite the promising applications, the mechanisms of nutrient sorption and their effects on plant growth require further investigation, especially concerning structural changes and nutrient [...] Read more.
The full potential of glauconite-based nanocomposites as micronutrient fertilizers remains underexplored, particularly their interaction with Zn, Cu, and B. Despite the promising applications, the mechanisms of nutrient sorption and their effects on plant growth require further investigation, especially concerning structural changes and nutrient delivery efficiency. This study investigates the modification of glauconite with Zn, Cu, and B solutions to create multifunctional nanocomposites with enhanced properties. It was established that the activation process preserves the primary globular–lamellar morphology of glauconite while introducing structural changes. Nanocomposites were synthesized using chemical activation and characterized using XRD, SEM-EDS, TEM, FTIR, and BET analyses. Agrochemical tests evaluated their effects on oat growth under controlled conditions. Nanocomposites with zinc sulfate exhibited an increase in specific surface area and mesoporosity, enhancing sorption capacity and facilitating the formation of inner-sphere complexes on the mineral’s basal surface. Modification with copper led to the formation of secondary phases, such as sulfates, on the surfaces of microflakes and globules while preserving the crystalline structure with inner-sphere coordination of Cu2+. Boron-modified nanocomposites were characterized by localized restructuring, pore channeling, and an increase in mesopore diameter, along with the formation of outer-sphere complexes relative to the basal surface of glauconite. Thermogravimetric and calorimetric analyses with mass spectrometry revealed specific endothermic and exothermic effects, particularly in Zn-modified samples, confirming changes in dehydration energetics. Agricultural tests on oats (Avena sativa) demonstrated the effectiveness of Cu- and B-modified nanocomposites in improving plant growth parameters, including a 7% increase in plant height and a 6.4% increase in dry weight. Zn-modified nanocomposites showed high germination rates (up to 100%) at low dosages but require optimization to avoid phytotoxicity at higher concentrations. The findings highlight the potential of adapting nanocomposites for targeted nutrient release. Additionally, glauconite nanocomposites have potential applications in restoring degraded soils, treating polluted runoff, and developing slow-release agrochemical systems. Full article
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24 pages, 5939 KiB  
Article
Bismuth Sulfosalts from the Nistru Metallogenetic Field, Baia Mare Zone, NW Romania
by Floarea Damian, Gheorghe Damian, Nigel J. Cook, Vsevolod Yu. Prokofiev and Peter András
Minerals 2024, 14(11), 1182; https://doi.org/10.3390/min14111182 - 20 Nov 2024
Viewed by 1343
Abstract
An association of bismuth sulfosalts coexisting with native gold is described from a sulfide-rich copper vein in the Nistru area, Baia Mare metallogenetic district, NW Romania. This mineralization is hosted within a Neogene calc-alkaline subvolcanic porphyry quartz-micromonzodiorite stock on the southern border of [...] Read more.
An association of bismuth sulfosalts coexisting with native gold is described from a sulfide-rich copper vein in the Nistru area, Baia Mare metallogenetic district, NW Romania. This mineralization is hosted within a Neogene calc-alkaline subvolcanic porphyry quartz-micromonzodiorite stock on the southern border of the Gutâi Mountains. Cu+Au+Bi mineralization represents the inner part of a zoned vein of a type specific to the SE part of the Nistru orefield. The Pb-Zn and Au-Ag veins are located towards the external zone at the boundary of the stock with the surrounding rocks. Bismuth sulfosalts are mainly represented by bismuthinite derivatives and members of the lillianite homologous series. Cosalite, matildite and wittichenite are also present in subordinate amounts. Bi-rich members of the bismuthinite-aikinite series (from krupkaite to bismuthinite) are predominant. A phase with the empirical formula CuPbBi7S12 was also identified and could potentially be a new bismuthinite derivative. The lillianite homologous series is represented by phases with composition between Gus73 and Gus59, with a dominance of members closer to gustavite (Gus97–79) and less abundant members closer to lillianite (Gus49). Native gold and Bi-sulfosalts are closely associated with the main sulfides (pyrrhotite, pyrite, chalcopyrite) and quartz, indicating simultaneous crystallization. Fluid inclusion data for quartz indicate a temperature interval between 205 and 247 °C. The assemblage within this vein was deposited from a low-salinity fluid (0.4–2.6 wt.% NaCl equiv.) and density from 0.80 to 0.87 g/cm3. Full article
(This article belongs to the Section Mineral Deposits)
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21 pages, 30921 KiB  
Article
New Porphyry Copper–Molybdenum Ore Occurrence in Arganaty Granites of the Eastern Balkhash (Kazakhstan): Geology, Geochemistry, and Mineralogy
by Adilkhan Baibatsha, Ilya Vikentyev, Daulet Muratkhanov and Kanat Bulegenov
Geosciences 2024, 14(9), 237; https://doi.org/10.3390/geosciences14090237 - 2 Sep 2024
Viewed by 1928
Abstract
In the Balkhash region of Kazakhstan, there are numerous copper and copper–molybdenum deposits, including superlarge Aktogay, Aidarly, Kounrad, and large Sayak deposits. Despite the proximity to these ore districts, the Arganaty district of the Eastern Balkhash region has not attracted significant interest in [...] Read more.
In the Balkhash region of Kazakhstan, there are numerous copper and copper–molybdenum deposits, including superlarge Aktogay, Aidarly, Kounrad, and large Sayak deposits. Despite the proximity to these ore districts, the Arganaty district of the Eastern Balkhash region has not attracted significant interest in terms of exploration for many years. Our recent work has identified previously undetected copper–molybdenum mineralization in the granites of the Arganaty massif and has provided a new perspective on the economic potential of this area. In this study, based on the geology, mineralogy, and geochemistry of the Arganaty granites using data from XRF and ICP-MS methods, we reassessed the geological structure and prospectivity of this area. Our investigations have found that the intrusive rocks of the Arganaty massif belong to I-type granites and were formed in a subduction setting rather than a collision setting, as was previously believed. This also indicates the high prospects of the territory in the context of the possible discovery of large Cu or Cu–Mo deposits. Full article
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12 pages, 508 KiB  
Article
Interval Iterative Decreasing Dimension Method for Interval Linear Systems and Its Implementation to Analog Circuits
by Gülnur Çelik Kızılkan and Büşra Yağlıpınar
Mathematics 2024, 12(17), 2655; https://doi.org/10.3390/math12172655 - 27 Aug 2024
Viewed by 858
Abstract
The iterative decreasing dimension method (IDDM) is an iterative method used to solve the linear algebraic system Ax=f. Such systems are important in modeling many problems in applied sciences. For a number of reasons, such as estimated measurements made [...] Read more.
The iterative decreasing dimension method (IDDM) is an iterative method used to solve the linear algebraic system Ax=f. Such systems are important in modeling many problems in applied sciences. For a number of reasons, such as estimated measurements made for modeling, errors arising from floating point calculations, and approximation methods used for solutions, it becomes necessary to study intervals in the solutions of systems of linear equations. The objective of this paper is to utilize IDDM to achieve resolution in the interval linear system (ILS). During the calculations, the Kaucher space is considered an extended classical interval space. The solutions of Barth-Nuding and Hansen interval linear systems, which are commonly used in the literature to test the solutions of ILSs, are obtained with the interval iterative decreasing dimension method for interval linear systems (I-IDDM). Since IDDM is a variation method of Gaussian elimination, a comparative analysis of the results with the interval Gaussian elimination method (I-GEM) is performed. It has been demonstrated that our approach, I-IDDM, produces better outcomes than I-GEM. I-IDDM is also used to investigate the analog circuit problem, where interval analysis is crucial. Full article
(This article belongs to the Section E: Applied Mathematics)
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14 pages, 4332 KiB  
Article
Impacts of Impurity Removal Chemical Pretreatment Procedures on the Composition and Adsorption Properties of Bentonites
by Tatiana Koroleva, Victoria Krupskaya, Ekaterina Tyupina, Ivan Morozov, Pavel Kozlov, Boris Pokidko, Sergey Zakusin and Tatiana Zaitseva
Minerals 2024, 14(8), 736; https://doi.org/10.3390/min14080736 - 23 Jul 2024
Cited by 1 | Viewed by 1513
Abstract
This work is based on a detailed study of samples from three industrial bentonite deposits in Russia (10th Khutor, Zyryanskoe) and Kazakhstan (Taganskoe). The samples of the listed bentonites were undergoing stage-by-stage purification from carbonates, organic matter, and non-clay iron-bearing phase procedures. The [...] Read more.
This work is based on a detailed study of samples from three industrial bentonite deposits in Russia (10th Khutor, Zyryanskoe) and Kazakhstan (Taganskoe). The samples of the listed bentonites were undergoing stage-by-stage purification from carbonates, organic matter, and non-clay iron-bearing phase procedures. The conducted research revealed changes in the composition of bentonites already at the first stage of purification, which, however, were not noted for all bentonites, as well as a change in the forms of Fe in smectite structure. The latter is probably associated with changes in cis- and trans-vacant positions. Sorption characteristics with respect to 137Cs are determined using the localization and charges in the smectite layer and the slight changes during purification, along with the specific surface area indicators. Full article
(This article belongs to the Special Issue Adsorption Properties and Environmental Applications of Clay Minerals)
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23 pages, 19609 KiB  
Article
Transformation of the Geological Environment under the Influence of Liquid Radioactive Waste (Russian Experience in Studying Historical Nuclear Disposal)
by Victoria Krupskaya, Sergey Zakusin and Mikhail Chernov
Minerals 2024, 14(3), 252; https://doi.org/10.3390/min14030252 - 28 Feb 2024
Viewed by 1544
Abstract
Due to various historical events, in the Russian Federation, in addition to the radioactive waste storage facilities used in world practice, there are various nuclear and radiation hazardous facilities that require special procedures for monitoring and decommissioning. One of these facilities is the [...] Read more.
Due to various historical events, in the Russian Federation, in addition to the radioactive waste storage facilities used in world practice, there are various nuclear and radiation hazardous facilities that require special procedures for monitoring and decommissioning. One of these facilities is the disposal site for LRW on the territory of the JSC Siberian Chemical Plant, where specially prepared waste is injected into sand reservoirs lying at depths of 300–350 m between clayey strata. This study examines in detail the features of the lithological and mineral composition of reservoir sands and aquitards. The processes of environmental transformation in reservoir sands, which lead to changes in the composition and structure of rocks, were characterized. These processes manifest themselves in the form of the development of leaching zones and their “healing” with newly formed smectite, the destruction of terrigenous grains, including the development of cracks, and the growth of newly formed smectite in the pore space of reservoirs. The forms of occurrence and localization of authigenic smectite formed as a result of technogenic impact are described. It has been shown that, despite the obvious impact of highly reactive solutions accompanying liquid radioactive waste, the insulating properties of the geological environment are maintained and even improved to some extent. Full article
(This article belongs to the Special Issue Adsorption Properties and Environmental Applications of Clay Minerals)
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30 pages, 13354 KiB  
Article
Gold and Arsenic in Pyrite and Marcasite: Hydrothermal Experiment and Implications to Natural Ore-Stage Sulfides
by Elena V. Kovalchuk, Boris R. Tagirov, Sergei E. Borisovsky, Maximilian S. Nickolsky, Evgeniya E. Tyukova, Nina V. Sidorova, Vladimir B. Komarov, Anna A. Mezhueva, Vsevolod Yu. Prokofiev and Ilya V. Vikentyev
Minerals 2024, 14(2), 170; https://doi.org/10.3390/min14020170 - 4 Feb 2024
Cited by 8 | Viewed by 2918
Abstract
Hydrothermal synthesis experiments were performed in order to quantify the states of Au and As in pyrite and marcasite. The experiments were performed at 350 °C/500 bar and 490 °C/1000 bar (pyrite–pyrrhotite buffer, C(NaCl) = 15 and 35 wt.%). The synthesis products [...] Read more.
Hydrothermal synthesis experiments were performed in order to quantify the states of Au and As in pyrite and marcasite. The experiments were performed at 350 °C/500 bar and 490 °C/1000 bar (pyrite–pyrrhotite buffer, C(NaCl) = 15 and 35 wt.%). The synthesis products were studied by EPMA, LA-ICP-MS, and EBSD. The EPMA was applied for simultaneous determinations of Au, As, Fe, and S, with a Au detection limit of 45–48 ppm (3σ). The analyses were performed along profiles across zonal grains. The concentrations of As and Au up to 5 wt.% and 8000 ppm, respectively, were determined in pyrite and up to 6 wt.% and 1300 ppm in marcasite. In pyrite, the Au concentration decreases with fluid salinity and temperature increases. Strong positive Au–As correlation and strong negative Au–Fe and As–S correlation were identified in pyrite. Comparison of the correlations with theoretical lines implies Au–As clustering. The cluster stoichiometry is inferred to be [AuAs10]. Most probably, As in pyrite presents in the form of clusters and in the As→S solid solution. Incorporation of Au in As-rich pyrite can be controlled by the reductive deposition mechanism. In marcasite, the concentrations of Au are not correlated with the As content. The [AuAs10] clusters enrich the {210}, {113}, and {111} pyrite faces, where the former exhibits the highest affinity to Au and As. The affinity of {110} and {100} forms to Au and As is lower. Implication of the experimental results to data for natural auriferous pyrite shows that the increase of Au content at C(As) > 0.5–1 wt.% is caused by the incorporation of the Au-As clusters, but not because of the formation of Au→Fe solid solution. Therefore, the concentration of “invisible” gold in pyrite is dictated solely by the hydrothermal fluid chemistry and subsequent ore transformations. Full article
(This article belongs to the Special Issue Microanalysis Applied to Mineral Deposits)
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16 pages, 2982 KiB  
Article
Directed Evolution of 4-Hydroxyphenylpyruvate Biosensors Based on a Dual Selection System
by Hongxuan Du, Yaoyao Liang, Jianing Li, Xinyao Yuan, Fenglin Tao, Chengjie Dong, Zekai Shen, Guangchao Sui and Pengchao Wang
Int. J. Mol. Sci. 2024, 25(3), 1533; https://doi.org/10.3390/ijms25031533 - 26 Jan 2024
Cited by 5 | Viewed by 2404
Abstract
Biosensors based on allosteric transcription factors have been widely used in synthetic biology. In this study, we utilized the Acinetobacter ADP1 transcription factor PobR to develop a biosensor activating the PpobA promoter when bound to its natural ligand, 4-hydroxybenzoic acid (4HB). To [...] Read more.
Biosensors based on allosteric transcription factors have been widely used in synthetic biology. In this study, we utilized the Acinetobacter ADP1 transcription factor PobR to develop a biosensor activating the PpobA promoter when bound to its natural ligand, 4-hydroxybenzoic acid (4HB). To screen for PobR mutants responsive to 4-hydroxyphenylpyruvate(HPP), we developed a dual selection system in E. coli. The positive selection of this system was used to enrich PobR mutants that identified the required ligands. The following negative selection eliminated or weakened PobR mutants that still responded to 4HB. Directed evolution of the PobR library resulted in a variant where PobRW177R was 5.1 times more reactive to 4-hydroxyphenylpyruvate than PobRWT. Overall, we developed an efficient dual selection system for directed evolution of biosensors. Full article
(This article belongs to the Special Issue Whole-Cell System and Synthetic Biology)
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27 pages, 3491 KiB  
Article
Multi-Level Perceptions on Higher Education Development for Sanitation and Hygiene Management in Nigeria
by Peter Emmanuel Cookey, Mayowa Abiodun Peter-Cookey, Iloma Unwobuesor Richard and Damir Brdanovic
Hygiene 2023, 3(4), 465-491; https://doi.org/10.3390/hygiene3040035 - 23 Nov 2023
Viewed by 2517
Abstract
Providing safely managed sanitation/hygiene requires key competencies for education, training, service delivery, enterprise development and management, product and infrastructure design and development, construction and installation, governance, financing, research, etc. These strategic sanitation capacities will have to be built from higher education’s academic and [...] Read more.
Providing safely managed sanitation/hygiene requires key competencies for education, training, service delivery, enterprise development and management, product and infrastructure design and development, construction and installation, governance, financing, research, etc. These strategic sanitation capacities will have to be built from higher education’s academic and professional programmes structured and designed to produce skilled and knowledgeable professionals and practitioners. This study aims to investigate the quality of the sanitation/hygiene management content of Environmental Health programmes; the adequacy of the existing central curricula; and the perception of environmental health sanitation/hygiene-trained professionals to determine the next phase for building knowledge and capacity of sanitation professionals in Nigeria through higher education institutions. A multi-level mixed method concurrent study was used for sampling and data collection with a multi-level perception analysis to examine the perceptions of students, lecturers and graduate alumni, as well as employers/supervisors and clients/service users of sanitation/hygiene-related graduates. The main findings of this paper show a limited understanding of the concepts of contemporary issues of sanitation/hygiene management like sustainable sanitation, citywide inclusive sanitation, regenerative sanitation, circular bioeconomy, etc.; the central/national teaching and curricula were found to be seriously out of date; and clients/service users were dissatisfied with the skills and knowledge levels of the graduates. The study concludes by recommending a national sanitation management higher education pathway to guide the provision of integrated sanitation/hygiene management education at higher education institutions (HEIs), to build an effective, efficient, competent and sufficient workforce for the country. Full article
(This article belongs to the Section Environmental Health)
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14 pages, 11248 KiB  
Article
Zinc-Intercalated Halloysite Nanotubes as Potential Nanocomposite Fertilizers with Targeted Delivery of Micronutrients
by Prokopiy Maximov, Evan Dasi, Natalia Kalinina, Alexey Ruban, Boris Pokidko and Maxim Rudmin
Materials 2023, 16(20), 6729; https://doi.org/10.3390/ma16206729 - 17 Oct 2023
Cited by 7 | Viewed by 1983
Abstract
This study reports on the development of nanocomposites utilizing a mineral inhibitor and a micronutrient filler. The objective was to produce a slow release fertilizer, with zinc sulfate as the filler and halloysite nanotubes as the inhibitor. The study seeks to chemically activate [...] Read more.
This study reports on the development of nanocomposites utilizing a mineral inhibitor and a micronutrient filler. The objective was to produce a slow release fertilizer, with zinc sulfate as the filler and halloysite nanotubes as the inhibitor. The study seeks to chemically activate the intercalation of zinc into the macro-, meso-, and micropores of the halloysite nanotubes to enhance their performance. As a result, we obtained three nanocomposites in zinc sulfate solution with concentrations of 2%, 20%, and 40%, respectively, which we named Hly-7Å-Zn2, Hly-7Å-Zn20, and Hly-7Å-Zn40. We investigated the encapsulation of zinc sulfate in halloysite nanotubes using X-ray diffraction analysis, transmission electron spectroscopy, infrared spectroscopy (FTIR), and scanning electron microscopy with an energy-dispersive spectrometer. No significant changes were observed in the initial mineral parameters when exposed to a zinc solution with a concentration of 2 mol%. It was proven that zinc was weakly intercalated in the micropore space of the halloysite through the increase in its interlayer distance from 7.2 to 7.4. With an increase in the concentration of the reacted solution, the average diameter of the nanotubes increased from 96 nm to 129 nm, indicating that the macropore space of the nanotubes, also known as the “site”, was filled. The activated nanocomposites exhibit a maximum fixed content of adsorbed zinc on the nanotube surface of 1.4 wt%. The TEM images reveal an opaque appearance in the middle section of the nanotubes. S SEM images revealed strong adhesion of halloysite nanotubes to plant tissues. This property guarantees prolonged retention of the fertilizer on the plant surface and its resistance to leaching through irrigation or rainwater. Surface spraying of halloysite nanotubes offers accurate delivery of zinc to plants and prevents soil and groundwater contamination, rendering this fertilizer ecologically sound. The suggested approach of activating halloysite with a zinc solution appears to be a possible route forward, with potential for the production of tailored fertilizers in the days ahead. Full article
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17 pages, 12062 KiB  
Article
Montbrayite from the Svetlinsk Gold–Telluride Deposit (South Urals, Russia): Composition Variability and Decomposition
by Olga V. Vikent’eva, Vladimir V. Shilovskikh, Vasily D. Shcherbakov, Tatyana N. Moroz, Ilya V. Vikentyev and Nikolay S. Bortnikov
Minerals 2023, 13(9), 1225; https://doi.org/10.3390/min13091225 - 18 Sep 2023
Cited by 4 | Viewed by 1749
Abstract
A rare gold–telluride montbrayite from the large Svetlinsk gold–telluride deposit (South Urals, Russia) was comprehensively studied using optical microscopy, scanning electron microscopy, electron microprobe analysis, reflectance measurements, electron backscatter diffraction, and Raman spectroscopy. Significant variations in the composition of the mineral were revealed [...] Read more.
A rare gold–telluride montbrayite from the large Svetlinsk gold–telluride deposit (South Urals, Russia) was comprehensively studied using optical microscopy, scanning electron microscopy, electron microprobe analysis, reflectance measurements, electron backscatter diffraction, and Raman spectroscopy. Significant variations in the composition of the mineral were revealed (in wt%): Au 36.98–48.66, Te 43.35–56.53, Sb 2.49–8.10, Ag up to 4.56, Pb up to 2.04, Bi up to 0.33, Cu up to 1.42. There are two distinct groups with much more-limited variation within the observed compositional interval (in wt%): (1) Au 36.98–41.22, Te 49.35–56.53, Sb 2.49–5.57; (2) Au 47.86–48.66, Te 43.35–44.92, Sb 7.15–8.10. The empirical formula calculated on the basis of 61 apfu is Au16.43–23.28Sb1.79–6.09Te32.01–38.89Ag0–3.69Bi0–0.14Pb0–0.90Cu0–1.96. Two substitution mechanisms for antimony are proposed in the studied montbrayite grains: Sb→Au (2.5–5.6 wt% Sb) and Sb→Te (7–8 wt% Sb). The dependence of the reflection spectra and Raman spectra on the antimony content and its substitution mechanism, respectively, was found in the mineral. The slope of the reflectance spectra decreases and the curve in the blue–green region of the spectrum disappears with increasing Sb content in montbrayite. Raman spectra are reported for the first time for this mineral. The average positions of the peak with high-intensity are ~64 cm−1 and ~90 cm−1 for montbrayite with Sb→Te and Sb→Au, respectively. Two grains of montbrayite demonstrate decomposition according to two schemes: (1) montbrayite (7 wt% Sb) → native gold + calaverite ± altaite, and (2) montbrayite (5 wt% Sb) → native gold + tellurantimony ± altaite. A combination of melting and dissolution–precipitation processes may be responsible for the formation of these decomposition textures. Full article
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23 pages, 21306 KiB  
Article
Typomorphic Features and Source of Native Gold from the Sykhoi Log Area Placer Deposits, Bodaibo Gold-Bearing District, Siberia, Russia
by Alexander Lalomov, Antonina Grigorieva, Alexei Kotov and Lidiya Ivanova
Minerals 2023, 13(5), 707; https://doi.org/10.3390/min13050707 - 22 May 2023
Cited by 12 | Viewed by 2678
Abstract
The Bodaibo gold-bearing district in the Lena gold province of Siberia is one of the largest and oldest placer gold-bearing provinces in the world. Approximately 1650 tons of gold has been extracted from the region. Precise studies on the source of these unique [...] Read more.
The Bodaibo gold-bearing district in the Lena gold province of Siberia is one of the largest and oldest placer gold-bearing provinces in the world. Approximately 1650 tons of gold has been extracted from the region. Precise studies on the source of these unique placer deposits are lacking and still controversial. Native gold from four different locations was gathered to investigate its morphology, chemical signatures, structure and inclusions. Some data on primary bedrock mineralization were obtained from the published literature. The linear weathering crusts developed along the zones of disjunctive dislocations near the Sukhoi Log gold deposit were researched. If they coincided with zones of low-grade veinlet-disseminated gold–quartz–sulphide mineralization with small gold grain sizes, a supergene replacement of primary mineralization was known to have occurred, accompanied by the formation of gold-rich rims and an increase in the size, content and purity of gold. Such mineralization associated with linear weathering crusts can be a source of local eluvial–proluvial placers, while placers of large valleys are formed due to low-sulphide gold–quartz lodes. Full article
(This article belongs to the Special Issue Native Gold as a Specific Indicator Mineral for Gold Deposits)
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