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Article

Investigation of the Possibility of Obtaining High-Purity Carbon Materials and Recovering Valuable Metals from Shungite Rocks

by
Tatiana Aleksandrova
,
Anastasia Afanasova
*,
Nadezhda Nikolaeva
,
Artyem Romashev
,
Valeriya Aburova
and
Evgeniya Prokhorova
Department of Mineral Processing, Empress Catherine II Saint Petersburg Mining University, 199106 St. Petersburg, Russia
*
Author to whom correspondence should be addressed.
Minerals 2025, 15(1), 90; https://doi.org/10.3390/min15010090
Submission received: 16 December 2024 / Revised: 13 January 2025 / Accepted: 14 January 2025 / Published: 18 January 2025
(This article belongs to the Special Issue Advances in Physical Separation of Gold, Iron Ore and Rare Earth Minerals)
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Abstract

:
The increased consumption of strategic metals has led to the necessity to search for new and non-traditional sources of mineral raw materials. All this has resulted in the necessity to develop and justify new technological solutions for the integrated recovery of strategic metals and the associated production of high-purity carbon materials. The purpose of this work was to substantiate the possibility of obtaining high-purity shungite carbon materials and metal-bearing concentrate containing valuable metals from shungite rocks using high-gradient magnetic separation and flotation with the use of an apolar collector emulsion in a frother solution. The conducted investigations using a complex of analysis methods allowed us to justify the obtaining of a metal-bearing concentrate containing iron, titanium, copper and zirconium and carbon material of high purity. By using high-gradient magnetic separation, we obtained a metal-bearing concentrate with a yield of 17.35% and a total metal content of 63.61% broken down as follows: Fe2O3 recovery of 87.66%, TiO2 recovery of 56.03%, CuO recovery of 72.52% and ZrO2 recovery of 54.42%. By using flotation, we obtained a shungite carbon concentrate with a yield of 31.41%, made of 88.15% carbon with a content and recovery of 88.09% and a sulphur content of 0.084%. The conducted studies showed the possibility of using classical beneficiation operations in the processing of non-traditional mineral raw materials to obtain commercial products.

1. Introduction

The economic growth of any country is associated with the large-scale use of minerals as a source of high-tech materials and metals [1,2]. Due to the progressive depletion of and decrease in the quality of the mineral resource base, there is a continuous search for new technological solutions for the recovery, concentration and processing of minerals as well as new, non-traditional sources of valuable components [3,4,5].
  • General information about shungite rocks
Shungite rock can be one of the possible sources of high-tech materials and a number of strategic metals [6]. This object is unique in terms of its genesis, the structure of the constituent carbon (shungite non-crystalline natural non-graphitised carbon) and its reserves in the Earth’s crust [6,7].
Deposits of Precambrian carbon-bearing rocks, including shungite rocks, are found all over the world: in Australia, North America, Africa, Kazakhstan, Russia, and other areas and countries. One of the best-known and largest deposits of shungite rocks is the Zazhoginskoye deposit (Karelia Republic, Russia). To describe such carbon-containing formations, it is convenient to use the classification by carbon content: more than 25 wt. % C—high carbonaceous; 5–25 wt. % C—medium carbonaceous; less than 5 wt.% C—low carbonaceous. At the same time, regardless of the amount, carbon in shungite rocks is represented by different morphological forms: globular, bundle, flake and film [8]. But fullerenes, which practically do not occur in nature, are of the greatest industrial interest. In addition, shungite rocks contain such minerals as quartz, pyrite, biotite, potassium feldspar, albite, fluorapatite, chlorite, calcite, arsenopyrite, rutile, zircon, monazite, titanite, etc. [9]. However, due to the specific features of structure, texture, material composition and size of impregnation, their industrial exploitation requires the development of effective technologies and technological solutions for their beneficiation and processing, which is possible through the creation of new and the improvement of existing methods of separation and beneficiation of raw materials, including the use of physical–energetic and chemical methods of action to ensure the concentration of valuable components, taking into account the complexity of raw materials [10,11,12].
  • Analysis of current technologies for shungite rock beneficiation
The unique features of shungite rocks include not only their complexity but also the fact that depending on the structure, the composition and characteristics of the constituent minerals and the carbon distribution, they have different physical and chemical properties [13,14]. This makes it possible to use different separation methods (flotation, magnetic, gravitational and hydrometallurgical) for the recovery of valuable components at consecutive stages of shungite rock beneficiation and processing [6,15,16,17].
At present, there are no plants for beneficiation of shungite rocks. Some works are known in the field of research of enrichability of this type of raw materials. In the article [6], the authors cite studies on the possibility of obtaining high-carbon shungite, anthraxolite, quartz and sulphides using mechanical beneficiation methods and physical impacts. Efremov S. [16] in his work showed the principal possibility of obtaining a shungite concentrate (as a sorbent) using column flotation. Also in [15], the results are reviewed of studies on obtaining carbon-containing products by removing iron- and sulphur-containing impurities using methods of magnetic and flotation processing as well as leaching. A characteristic feature of shungite is the high value of its specific surface area (up to 30 m2/g) with an average pore diameter of 14 nm [15], which makes it possible to use it as a sorbent after the removal of impurities.
Therefore, the analysis of recent investigations has shown that one of the promising methods of shungite rock beneficiation is the combination of magnetic and flotation methods for the recovery of high-purity carbon materials (including fullerenes) and valuable metals. The use of magnetic separation enables the separation of magnetic (both strongly and weakly magnetic) minerals from shungite rocks. For the recovery of weakly magnetic sulphide particles, it is reasonable to use high-gradient magnetic separation. Depending on the coarseness of the recovered particles, the most commonly used tools are SLon high-gradient magnetic separators (designed to obtain high-quality magnetic products using a pulsating stream during the separation of both coarse and fine materials) and Jones high-intensity magnetic separators (designed for the recovery of ultrafine weakly magnetic minerals) [18].
Carbonaceous material, which is a part of shungite rocks, is naturally hydrophobic, has unique sorption properties and can be recovered by flotation [11]. For the flotation of naturally hydrophobic materials, apolar collectors are used, most often comprising petroleum products such as paraffin, diesel fuel, straw oil, etc. [15,19]. Insufficient investigation of their physical and chemical properties in the flotation process due to their complex chemical and group composition makes it urgent to conduct investigations of the properties of apolar collectors and flotation of shungite rock beneficiation using reasonable combinations of reagents for concentrating valuable components.
The flotation activity of apolar collectors depends on the degree of dispersion in the pulp during flotation, which determines the supply of these reagents in the form of a finely dispersed emulsion [20,21]. However, the use of only emulsification without the use of a stabiliser, including the use of low-viscosity hydrocarbons such as paraffin, does not lead to the required degree of reagent dispersibility in the pulp, which predetermines the necessity to investigate the physical parameters of the emulsion, such as dynamic viscosity, surface tension at the liquid–gas interface, stability, etc. [22,23,24]. The relevance of this problem is due to the possibility of using the emulsion of an apolar collector in the beneficiation of not only different types of carbon-containing raw materials [25,26,27] but also ores of non-ferrous metals, including copper–molybdenum ores [28,29].
As a stabilising component in the emulsification of apolar collectors, it is possible to use surfactants, which adsorb on the interface surface of liquids to form stabilised films that promote the formation of hydrate layers and prevent the coalescence of oil droplets. The hydrocarbon radical of the stabiliser is solvated by the oil phase, and the polar group of the stabiliser is hydrated by the polar phase, which contributes to the minimum free energy of the system [30]. As a stabilising component, different frothers can be used.
Currently, research in the field of shungite rock beneficiation is fragmented, and shungite rocks are used in practice in a non-enriched form (mainly for water purification) without taking into account the complex nature of raw materials. The works on the search for possible methods and technologies for obtaining carbon materials and concentrates containing valuable metals are very relevant. Consequently, the purpose of this work was to substantiate the possibility of obtaining high-purity shungite carbon materials and metal-bearing concentrates containing strategic metals from shungite rocks using high-gradient magnetic separation and flotation with the use of an apolar collector emulsion.

2. Materials and Methods

2.1. Materials

Shungite rocks from the Zazhoginskoye deposit in the Karelia Republic, Russia, were selected as the subject of this investigation. The initial mass of the sample that was −60 + 0 mm in size was 100 kg. The material was crushed in a jaw crusher to a size range of −10 + 0 mm in the laboratory. The sample was then averaged using the coning and quartering method, and representative samples of 1 kg each were selected for further research. Table 1 presents the composition of the studied samples.
An analysis of the results presented in Table 1 shows that for the studied samples, the SiO2 content is 39.97%, which agrees well with the fact that the main mineral in the gangue is quartz. For shungite rocks, the presence of such components—impurities as Ti, V, Zr, Sr, Cr, Y, Ni, etc.—is noted. According to a review of the literature, shungite rocks contain mainly quartz; their accessory minerals are sericite, pyrite, chlorite, biotite, sphalerite, chalcopyrite, zircon and others [12,17]. Using a Shimadzu XRD-7000 analyser (Shimadzu Corporation, Kyoto, Japan), the mineral composition of the sample was determined (Table 2).
The studied shungite rock samples belong to a high-carbon type, and the texture of the samples is veined. Figure 1 shows the dissemination of sulphide minerals (mainly pyrite and pyrrhotite) and quartz in shungite rocks.
To investigate the possibility of obtaining high-purity shungite carbon materials from shungite rock beneficiation products, we used the following instruments: a Shimadzu EDX 7000 X-ray fluorescence analyser (Shimadzu Corporation, Kyoto, Japan), a Vega 3 LMH electron microscope (TESCAN, Brno, Czech Republic) equipped with an Oxford Instruments (Oxfordshire, UK) INCA Energy 250/X-max 20 energy-dispersive microanalyser, a Mastersizer 2000 particle-size analyser (Malvern Instruments, Malvern, UK), and a SNO-17 muffle furnace (Tula-Term, Tula, Russia).

2.2. Methods

2.2.1. Experimental Investigations of Magnetic Separation

Experiments of high-gradient magnetic separation were carried out on a Slon 100 vertical high-gradient magnetic separator (Outotec, Espoo, Finland). The scheme of the magnetic separation experiments is presented in Figure 2.
Initial samples of −0.5 + 0 mm coarseness were prepared for the experiment by sequential crushing on jaw and roll crushers. Data on the particle-size distribution of the sample after crushing were obtained by sieving the crushed products on sieves with aperture sizes of 500 μm, 425 μm, 300 μm, 150 μm and 63 μm (Figure 3). The distribution of material by size in the sample is quite homogenous: there are fine, medium and coarse size classes in the sample in almost equal amounts.
The weight of the sample in each experiment was equal to 100 g. Variable parameters of the high-gradient magnetic separator were as follows: the size of the matrix rods (1, 3 and 6 mm), the intensity of the magnetic field (0.1, 0.5 and 1.1 Tesla) and the pulsation frequency of the pulp (30, 34 and 38 Hz). The separation was carried out in one stage. Magnetic and non-magnetic fractions after separation were dried, weighed and analysed (for elemental and particle-size distribution). To confirm the obtained data and repeatability, each experiment was carried out three times.

2.2.2. Experimental Investigations of Flotation

To substantiate the emulsion composition, investigations of dynamic viscosity and surface tension at the liquid–gas interface were carried out using an SV-10 vibro-viscometer (A&D Company Ltd., Tokyo, JAPAN) and a DCAT 9 tensiometer (DataPhysics, Filderstadt, Germany). The temperature of both the liquid and emulsions during viscosity measurements was 20 °C. Emulsification of the emulsion was carried out using an I100-6/1 ultrasonic unit (LLC “Ultrasonic technique—INLAB”, Saint-Petersburg, Russia) with a power of 630 W; the treatment time was three minutes and the ultrasonic frequency was 22 kHz. Flotation experiments were carried out using a laboratory pneumo-mechanical flotation machine (Laarmann Group, Roermond, The Netherlands). To justify the reagent regime, flotation experiments were carried out on shungite rock (Figure 4) after grinding to a particle size of 60% of the −71 µm class.
Flotation experiments (Figure 5) on the justified reagent regime were carried out on the tailings of magnetic separation after grinding to a particle size of 60% of the −71-micron class.
The weight of the sample in each experiment was equal to 200 g. Distilled water was used for the flotation experiments. The flotation parameters were as follows: air flow rate—1.2 L/min; impeller speed—1100 rpm; flotation time—7 min. Agitation time with reagents was three minutes each, and lime was added in the grinding. As an apolar collector, straw oil was chosen, and as a frother, Neonol AF 9-12. Neonol AF 9-12 is a complex mixture of oxyethylated phenols with alkyl groups and a propylene base in trimers. After flotation, the products were dried and analysed for elemental and particle-size distribution. To confirm the obtained data and repeatability, each experiment was carried out three times.

3. Results and Discussion

To substantiate the possibility of obtaining high-purity carbon materials and metal-bearing concentrates from shungite rocks on the basis of combined magnetic separation and flotation, the following investigations were carried out:
  • Investigation of the possibility of obtaining a metal-bearing concentrate containing strategic metals from shungite rock using high-gradient magnetic separation;
  • Investigation of the possibility of recovering high-purity shungite carbon material in a flotation concentrate using an apolar collector emulsion.

3.1. Investigation of the Possibility of Obtaining a Metal-Bearing Concentrate Containing Strategic Metals from Shungite Rock Using High-Gradient Magnetic Separation

In addition to carbon, shungite rocks contain quartz, pyrite, biotite, potassium feldspar, apatite, chlorite and calcite; furthermore, arsenopyrite, rutile, zircon, titanite, etc., are noted as accessory minerals. These minerals have different magnetic susceptibilities (Figure 6), which suggests the possibility of using high-gradient magnetic separation as an economical and environmentally friendly method for their separation from carbon.
Investigations on the recovery of weakly and strongly magnetic minerals were carried out on a Slon high-gradient magnetic separator, and we varied the main technological factors to justify the choice of the regime for obtaining a collective concentrate containing such metals as iron, titanium, copper and zirconium and a carbon-containing product. In the first stage, the influence of magnetic field induction on obtaining a collective metal-bearing concentrate from shungite rocks was studied (Figure 7a). The experimental conditions were as follows: diameter of rods in the matrix—6 mm; pulsation frequency of the pulp—30 Hz; values of magnetic field induction—0.1, 0.5 and 1.1 Tesla.
The results of the conducted research (Figure 7a) have shown that initially, iron-containing minerals were extracted into the collective concentrate. However, as the magnetic field induction increased to a value of 1.1 Tesla, minerals containing titanium, copper and zirconium also entered the concentrate. At the minimum induction value, the maximum Fe2O3 content (54.16%) was observed, which was due to the very low yield of the magnetic fraction (0.81%).
In the second stage, the influence of the size of the rods in the matrix on the possibility of recovering iron, titanium, copper and zirconium was investigated (Figure 7b). The experimental conditions were as follows: magnetic field induction—1.1 Tesla; pulp pulsation frequency—30 Hz; diameter of rods in the matrix—1, 3 and 6 mm.
An analysis of the results presented in Figure 7b showed that the optimum diameter of rods in the matrix was 3 mm, because at this size, the maximum total metal content (47.97%) was achieved in the concentrate. It was also noted that with the increasing diameter of the rods in the matrix, the values of metal recovery decreased.
In the third stage, the effect of pulp pulsation on the recovery of metals in the concentrate was studied (Figure 7c). The experimental conditions were as follows: magnetic field induction—1.1 Tesla; diameter of rods in the matrix—3 mm; frequency of pulsation of the pulp—30, 34 and 38 Hz.
The results of the conducted investigations on magnetic separation indicate an increase in the content of recoverable metals with increasing pulsation frequency; also, the recovery of Fe2O3 increases with increasing pulsation frequency (from 20.50% to 87.66%) (Figure 7c). At the same time, the recovery of TiO2 and ZrO2 first increases then slightly decreases. The analysis of the obtained results showed that the optimum value of pulsation frequency for obtaining the purest concentrate is 38 Hz.
Figure 8 displays the results of determining the particle size of the magnetic fraction using a laser particle-size analyser.
Analysis of the data presented in Figure 8 shows that 80% of the product has a grain size of—453 microns, while less than 10% has a grain size of less than 38.7 microns. Figure 9 and Table 3 show the results of the investigation of the magnetic concentrate using scanning electron microscopy.
Thus, the conducted investigations allowed us to establish the optimal parameters of shungite rock beneficiation to obtain a metal-bearing concentrate containing iron, titanium, copper and zirconium and a carbon-containing product: diameter of matrix rods—3 mm; magnetic field induction—1.1 Tesla; —pulp pulsation frequency—38 Hz. The metal-bearing concentrate had the following composition: yield—17.35%; total content—63.61%; Fe2O3 recovery—87.66%; TiO2 recovery—56.03%; CuO recovery—72.52%; ZrO2 recovery—54.42%.

3.2. Investigation of the Possibility of Recovering High-Purity Shungite Carbon Material into Flotation Concentrate Using an Apolar Collector Emulsion

Table 4 presents the results of investigations into the measurements of surface tension values at the liquid–gas (L-G) interface (σL-G) and dynamic viscosity (η) for the investigated liquids and solutions.
The interpretation of the results presented in Table 4 shows that the surface tension value for distilled water is 72.04 mN/m. Straw oil belongs to the group of reagents with high viscosity, equal to 21.0 mPa·s, the surface tension at the liquid–gas interface being 30.24 mN/m. The investigated Neonol solutions are classified as surfactants due to their decreased σL-G value relative to pure distilled water. Decreasing the concentration of Neonol AF 9-12 solution from 10% to 1% results in a decrease in the surface tension value from 30.22 mN/m to 29.44 mN/m. It is worth noting that for Neonol, the dynamic viscosity increases, so for the 1% solution, it is 1.93 mPa·s, while for the 10% solution, it is 21.4 mPa·s.
Table 5 shows the results of the investigation of the effect of the mass ratio of straw oil to Neonol in the emulsion composition using 5% Neonol solution on the values of surface tension at the liquid–gas interface and dynamic viscosity.
Due to the high viscosity of straw oil, emulsions after emulsifying by ultrasound are quite stable, and the values of surface tension and dynamic viscosity are quite close at different ratios (Table 5). Taking into account the need for a large consumption of the apolar collector during flotation with a small consumption of the frother, the mass ratio of straw oil to Neonol of 30:70 for the preparation of the emulsion was chosen for investigation. It should be noted that the viscosity of the obtained emulsion was 39.6 mPa·s, which suggests the presence of an additive contribution of the components that occurs during the preparation of the emulsion, since the viscosity of the emulsion was higher than the viscosity of each of the components. The surface tension at the liquid–gas interface of the emulsion was 30.15 mN/m.
To justify the consumption of the collector emulsion, an investigation of shungite rock flotation was carried out in which we varied the reagent consumption from 500 to 3000 g/t. Figure 10a shows the results of the investigation of the effect of straw oil emulsion consumption in Neonol on the concentrate yield and content and the recovery of shungite carbon in the concentrate.
An analysis of the data presented in Figure 10a indicates that with increasing emulsion consumption, there is an increase in concentrate yield, which is logical. At the same time, it should be noted that at a consumption above 1500 g/t, there is a decrease in the content of carbon in the concentrate, and the recovery increases insignificantly. At a consumption rate of 1500 g/t, the carbon content and recovery are 55.06% and 66.78%, while at an emulsion consumption rate of 2000 g/t, they are 53.64% and 66.81%, respectively. Figure 10b shows the results of the investigation of the effect of straw oil emulsion consumption on the silicon oxide and sulphur content and recovery in the concentrate.
The interpretation of the results presented in Figure 10b shows that the decrease in carbon content is due to the contamination of the concentrate with silicates and sulphides. The recovery of sulphur in the concentrate increased from 44.40% to 46.04% when the consumption of the emulsion increased from 1500 g/t to 2000 g/t. Silicate recovery had lower values and increased from 17.94% to 18.93% under similar conditions. Thus, to improve the quality of the concentrate, it is worth reducing the recovery of sulphides in it by adding lime to depress the Fe sulphide. Figure 10c shows the results of the investigation of lime consumption on the content and recovery of silicon oxide and sulphur in the concentrate. It should be noted that in the absence of lime, the pH at flotation was 7.8. The addition of lime in an amount of 250 g/t led to an increase in the pH of up to 9.9, while at the addition of lime at flotation with a consumption of 500 g/t, the pH increased up to 11.0. Increasing the lime consumption to 1000 g/t and 1500 g/t resulted in pH levels of 11.5 and 11.9, respectively.
An analysis of the results presented in Figure 10c shows that with increasing lime consumption, there is a significant decrease in the content and recovery of sulphide minerals in the concentrate, as evidenced by the decrease in technological parameters for sulphur. Without the addition of a depressor, the S recovery in the concentrate is 44.40% with a grade of 1.668%; furthermore, when the consumption is increased to 1.5 kg/t, the content and recovery decrease to 0.248 and 5.12%, respectively, while the pH increases from 6.87 to 10.58. Silicon oxide recovery also decreases, which is most likely due to the close association of quartz and sulphides in the shungite rock beneficiation studied, which was also observed in the high-gradient magnetic separation.
Figure 10d shows the results of the investigation of the effect of the depressor on the concentrate yield, content and recovery of carbon and zircon oxide. A decrease in carbon recovery was noted at a lime consumption above 1000 g/t, while at a consumption of 500 g/t, the purest concentrate with a low recovery of gangue was obtained: the recovery values of SiO2 and S were 13.07% and 7.70%, and the carbon recovery was 95.73% with a 77.49% content. The interpretation of the results presented in Figure 10d shows that the concentrate yield decreases with increasing lime consumption, which is associated not only with pyrite depression but also with increasing water hardness due to a large number of calcium ions, which leads to the deterioration of foaming and, as a consequence, a decrease in all technological parameters. The obtained high-purity concentrate containing shungite carbon is unique and can be modified [32] and used as a sorbent, including for minimising the effects of environmental disasters [26,33,34].
Based on the analysis of the obtained flotation data, the following parameters were determined for obtaining shungite concentrate: application of emulsion of straw oil in 5% Neonol solution at a ratio of 30:70 with a consumption of 1500 g/t and a lime consumption of 500 g/t.
In order to substantiate the possibility of using the combined scheme of magnetic–flotation beneficiation, experiments were carried out using reasonable parameters. Table 6 presents the results of shungite rock beneficiation using high-gradient magnetic separation and flotation with the justified emulsion composition and reagent consumption.
Figure 11 shows the results of the determined particle-size distribution of the shungite flotation concentrate using a laser particle-size analyser.
An analysis of the data presented in Figure 11 indicates that during flotation, mainly fine particles at 90% and of the class of −34.7 microns were extracted in the concentrate. In paper [35], it is indicated that Neonol has dispersant properties, which allows the increase of the recovery of fine grades in flotation. It is also noted that due to the formation of aggregates, the recovery and entrainment of gangue may increase [36]. An analysis of the flotation data (Table 6) allows us to determine the recovery of zirconium oxide and titanium oxide in addition to carbon, which is equal to 9.86% and 22.47%, respectively. The highest contents in shungite concentrate are also noted for zinc oxide and copper oxide (represented in shungite rocks by sulphides), which suggests the association of zirconium with sulphide minerals. It has been noted that a significant number of trace elements are associated with sulphides [7,9]. To decrease the recovery of silicate-group gangue minerals, selectively active depressors can be used [37,38,39].
As a result of our investigations, the following parameters for the separation of a metal-bearing concentrate containing strategic metals using high-gradient magnetic separation were substantiated: diameter of matrix rods—3 mm; magnetic induction—1.1 Tesla; pulsation frequency of pulp—38 Hz. The flotation parameters for the recovery of shungite carbon substance into a carbon concentrate on the basis of the application of an emulsion of straw oil in 5% Neonol solution at a ratio of 30:70 with a consumption of 1500 g/t and lime consumption of 500 g/t were substantiated.

4. Conclusions

Shungite rocks present an unconventional source of strategic metals as well as shungite carbon. Two concentrates were obtained by using magnetic separation and flotation with justified regime parameters: metal-bearing and flotation shungite concentrates. The metal-bearing concentrate is a product that can be used for the further recovery of metals, e.g., Zr, Cu, etc., using, for example, leaching.
Shungite carbon is a porous material (average pore size 14 nm) with a high value of its specific surface area (up to 30 m2/g), which makes it possible to use it also in the removal of impurities during wastewater treatment. The sequential application of magnetic separation and flotation for the purification of shungite rocks of harmful impurities (mainly sulphides) allows us to obtain high-purity material, which can be used as a sorbent. It is also worth noting that shungite carbon is almost the only source of fullerene and graphene. Consequently, it is possible to use the obtained shungite concentrate as a source of unique allotropic modifications of carbon.
A promising direction for further investigations is the development and scientific substantiation of metal recovery from metal-bearing concentrates and an increase in the porosity of shungite carbon using various influences.

Author Contributions

T.A. conceived and designed the experiments and analysed the data; N.N. and A.A. implemented and processed the analysis results; A.R., V.A. and E.P. performed the experiments. All authors have read and agreed to the published version of the manuscript.

Funding

This work was carried out within a grant from the Russian Science Foundation (Project N 23-47-00109).

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Minerals 15 00090 g001
Figure 1. Dissemination of sulphide minerals and quartz in shungite rocks (a) and shungite rock sample (b).
Figure 1. Dissemination of sulphide minerals and quartz in shungite rocks (a) and shungite rock sample (b).
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Minerals 15 00090 g002
Figure 2. Scheme of magnetic separation experiments.
Figure 2. Scheme of magnetic separation experiments.
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Minerals 15 00090 g003
Figure 3. Granulometric characterisation of the sample.
Figure 3. Granulometric characterisation of the sample.
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Figure 4. Scheme of flotation experiments.
Figure 4. Scheme of flotation experiments.
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Minerals 15 00090 g005
Figure 5. Scheme of experiments with sequential magnetic separation and flotation.
Figure 5. Scheme of experiments with sequential magnetic separation and flotation.
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Minerals 15 00090 g006
Figure 6. Scale of specific magnetic susceptibility for minerals included in shungite rocks [31].
Figure 6. Scale of specific magnetic susceptibility for minerals included in shungite rocks [31].
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Minerals 15 00090 g007
Figure 7. Results of investigation of the influence of high-gradient magnetic separation parameters (a)—magnetic field intensity; (b)—diameter of matrix rods; (c)—pulp pulsation frequency) on shungite rock beneficiation.
Figure 7. Results of investigation of the influence of high-gradient magnetic separation parameters (a)—magnetic field intensity; (b)—diameter of matrix rods; (c)—pulp pulsation frequency) on shungite rock beneficiation.
Minerals 15 00090 g007
Minerals 15 00090 g008
Figure 8. Results of investigation of particle-size distribution of magnetic product after high-gradient magnetic separation.
Figure 8. Results of investigation of particle-size distribution of magnetic product after high-gradient magnetic separation.
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Minerals 15 00090 g009aMinerals 15 00090 g009b
Figure 9. Microphotograph of the magnetic fraction obtained under the following parameters: diameter of matrix rods—3 mm; magnetic field induction—1.1 Tesla; pulsation frequency of the pulp—38 Hz.
Figure 9. Microphotograph of the magnetic fraction obtained under the following parameters: diameter of matrix rods—3 mm; magnetic field induction—1.1 Tesla; pulsation frequency of the pulp—38 Hz.
Minerals 15 00090 g009aMinerals 15 00090 g009b
Minerals 15 00090 g010
Figure 10. Results of investigation of the influence of flotation parameters ((a,b)—emulsion consumption; (c,d)—lime consumption) on shungite rock beneficiation.
Figure 10. Results of investigation of the influence of flotation parameters ((a,b)—emulsion consumption; (c,d)—lime consumption) on shungite rock beneficiation.
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Minerals 15 00090 g011
Figure 11. Results of determination of particle-size distribution of shungite flotation concentrate.
Figure 11. Results of determination of particle-size distribution of shungite flotation concentrate.
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Table 1. Composition of the studied samples of shungite rocks.
Table 1. Composition of the studied samples of shungite rocks.
ComponentCSiO2CaOFe2O3Al2O3K2OSTiO2As2O3
Content [%]31.4339.970.76011.908.532.241.4320.6570.551
ComponentMnOZnOCuOZrO2V2O5SrOCr2O3Y2O3NiO
Content [%]0.2200.0380.0250.0360.0690.0650.0350.0120.033
Table 2. Mineral composition of the studied samples of shungite rock.
Table 2. Mineral composition of the studied samples of shungite rock.
MineralContent [%]MineralContent [%]
Carbon (shungite)31.4Pyrite, pyrrhotite2.8
Quartz35.9Calcite2.1
Serizite, hydromica14.2Arsenopyrite1.9
Garnet, iron oxide6.2Rutile0.9
Chlorite, biotite, zircon, apatite, etc.4.2Sulphide (chalcopyrite, sphalerite, etc.)0.4
Table 3. Elemental composition of Figure 9.
Table 3. Elemental composition of Figure 9.
Number of SpectraContent, wt. [%]
COFeSSiMgAlKCuZrNiCa
Spectrum 129.117.9328.7419.953.724.071.97-0.98--3.53
Spectrum 237.865.7325.8628.101.21-0.240.17-0.84--
Spectrum 349.788.7018.7118.543.09-0.400.19-0.58--
Spectrum 427.531.9233.0936.810.21-----0.42-
Table 4. Results of investigation of the values of dynamic viscosity and surface tension of the investigated liquids and solutions at the liquid–gas interface.
Table 4. Results of investigation of the values of dynamic viscosity and surface tension of the investigated liquids and solutions at the liquid–gas interface.
Liquid PhaseσL-G, mN/mη, mPa·s
Straw oil30.2421.0
Distilled water72.041.01
Neonol (1% solution)29.441.93
Neonol (2% solution)29.992.34
Neonol (5% solution)30.137.26
Neonol (10% solution)30.2221.4
Table 5. Results of investigation of the influence of the mass ratio of straw oil to Neonol in the emulsion composition on the values of the dynamic viscosity and surface tension of the investigated liquids.
Table 5. Results of investigation of the influence of the mass ratio of straw oil to Neonol in the emulsion composition on the values of the dynamic viscosity and surface tension of the investigated liquids.
The Mass Ratio of Straw Oil to Neonol20:8030:7040:6050:5060:40
σL-G, mN/m30.1430.1530.1630.1830.18
η, mPa·s36.339.639.839.939.9
Table 6. Results of shungite rock beneficiation using high-gradient magnetic separation and flotation using apolar collector emulsion.
Table 6. Results of shungite rock beneficiation using high-gradient magnetic separation and flotation using apolar collector emulsion.
ProductYield [%]Content [%]
CSiO2CaOFe2O3STiO2ZnOCuOZrO2
Metal-bearing concentrate17.352.9112.760.1260.147.4322.120.150.110.11
Carbon concentrate31.4188.155.990.092.120.0840.470.020.020.01
Tailings51.246.3269.641.391.570.2280.280.010.0090.03
Shungite rocks100.0031.4339.780.7611.901.4320.660.040.030.04
Product Recovery [%]
CSiO2CaOFe2O3STiO2ZnOCuOZrO2
Metal-bearing concentrate 1.615.572.7487.6690.0556.0367.7772.5254.42
Carbon concentrate 88.094.733.725.591.8422.4716.3618.579.86
Tailings 10.3189.7193.546.758.1121.5015.878.9135.72
Shungite rocks 100.00100.00100.00100.00100.00100.00100.00100.00100.00
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Aleksandrova, T.; Afanasova, A.; Nikolaeva, N.; Romashev, A.; Aburova, V.; Prokhorova, E. Investigation of the Possibility of Obtaining High-Purity Carbon Materials and Recovering Valuable Metals from Shungite Rocks. Minerals 2025, 15, 90. https://doi.org/10.3390/min15010090

AMA Style

Aleksandrova T, Afanasova A, Nikolaeva N, Romashev A, Aburova V, Prokhorova E. Investigation of the Possibility of Obtaining High-Purity Carbon Materials and Recovering Valuable Metals from Shungite Rocks. Minerals. 2025; 15(1):90. https://doi.org/10.3390/min15010090

Chicago/Turabian Style

Aleksandrova, Tatiana, Anastasia Afanasova, Nadezhda Nikolaeva, Artyem Romashev, Valeriya Aburova, and Evgeniya Prokhorova. 2025. "Investigation of the Possibility of Obtaining High-Purity Carbon Materials and Recovering Valuable Metals from Shungite Rocks" Minerals 15, no. 1: 90. https://doi.org/10.3390/min15010090

APA Style

Aleksandrova, T., Afanasova, A., Nikolaeva, N., Romashev, A., Aburova, V., & Prokhorova, E. (2025). Investigation of the Possibility of Obtaining High-Purity Carbon Materials and Recovering Valuable Metals from Shungite Rocks. Minerals, 15(1), 90. https://doi.org/10.3390/min15010090

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