The proposed additional funding is an excellent contribution to the implementation of GTK’s strategy. GTK’s goal is to renew and develop GTK Mintec’s digital laboratory and pilot plant complex serving domestic and international business and research during 2020–2025. The goal is to be the world’s leading pilot and research platform for circular economy and mineral processing.
GTK Mintec’s pilot plant and research laboratories specialize in serving e.g. the mining, metals and chemical industries, as well as the circular economy.
The Government’s fourth supplementary budget proposal is scheduled to be submitted to Parliament on Friday 5 June.
Director general Mika Nykänen, firstname.lastname@example.org, 029 503 2200
Head of the Circular Economy Solutions Unit Jouko Nieminen, email@example.com, 029 503 2180
The digitalization of Pilot Plant and Research Laboratories aims for the comprehensive development of Circular Economy Solutions units research environment in Outokumpu, Espoo and Kuopio. Basic guidelines for the development arise from GTK’s strategic goals for the years 2020 – 2023. The project is part of a programme that aims to increase our unit’s capabilities in utilising digitalization to the highest level, making it a pioneer in the field. Today, the work at the Outokumpu and Espoo sites includes a lot of manual data entry and sample data transfer, sample processing and result processing that are done by traditional methods and by sharing and working with individual excel sheets.
This project includes defining and implementation of future solutions, which will remarkedly ease and faster our operations in many different sectors starting from sample handling ending up to usability and analysis of the research results. There is a strong linkage to some investment projects. This development requires special knowhow and large investments, which will not be able without partnerships and external funding.
One main goal is to raise GTK Mintec’s position as a desired and recognized research, development and innovation partner for mineral processing on a global level. New digital platform for serving customers and researchers will be planned and created. GTK Mintec total development contains parts such as (1) renewal of spaces including offices, laboratories and pilot plant, (2) renewal of instrumentation and technologies in laboratories and pilot plant, (3) renewal of tailings area becoming as a new SMARTT smart tailings facility. In this digitalization development the main area is laboratory data flow management coupled with automation systems to enable the use of data streams for example in digital twin.
GTK’s self-financed project.
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SMARTT aims at developing the current GTK Mintec tailings facility into an instrumented Smart Tailings Facility with increased capacity for future operations. At the same time, new approaches and products will be developed based on instrumented long-term testing of mining wastes and structures at the SMARTT facility (WP 2). In addition, new and improved saleable products will be developed for tailings management, tailings optimization, process water recycling, effluent treatment, process mineralogy, and process development (WP 3). The suitability of tailings for use in 3D additive manufacturing will be determined, alongside the development of new geo-material inspired, mineral based 3D printed materials and products (WP4). All of the WPs thus contribute to GTK Mintec product and process development and to the fullest utilization of the Smart Tailings Facility concept, taking advantage of the new infrastructure developments at GTK Mintec. SMARTT closely interacts with the Digitalization project that develops data flows and processes for the new products developed in SMARTT as well as supports and integrates the data acquisition and management functions of the Smart Tailings Facility.
SMARTT is aligned with the goals of the Circular Economy Focus Area and the related S & I roadmap by developing saleable products that help make GTK an internationally recognized provider of solutions for sustainable use of mineral raw materials. These products and services all contribute to digitization, material stewardship, waste management, and water management.
GTK’s self-financed project.
The aim is to procure new flotation cells to the pilot plant at GTK Mintec in Outokumpu. The new flotation cells are part of a modernization and expansion of the services at GTK Mintec. This project includes, besides the flotation hardware, improved automation and new methods for process parameter measurement and process control. The new flotation cells will provide for more efficient beneficiation research and easier process planning. The upgrade of the research environment, including more comprehensive and up-to-date instrumentation, is necessary to be able to provide appropriate services to customers.
The project is a procurement project and GTK is the only participant.
Project is active from 1.8.2019 to 31.12.2021 and the total budget is 900 000 €.
Previous studies have demonstrated that Raman spectroscopy is an excellent tool for studying the degree of graphitization of carbonaceous material (CM), a method that in the case of metamorphic processes is independent of pressure but strongly dependent on temperature. Recently, natural graphite has come to be considered as a promising anode material for lithium ion batteries due to its high reversible capacity, appropriate charge/discharge profile and low cost. This text focuses on Raman measurements of graphite with examples from Rautalampi and Käpysuo, Central Finland. It briefly comprises the experimental background, an evaluation of the Raman data and the calculated graphitization degrees, which can be used to estimate the metamorphic crystallization temperatures of CM in the rocks.
The highest potential for finding flake graphite, which is the economically most valuable form of graphite, is restricted to areas of high metamorphic grade, such as upper amphibolite and granulite facies terrains. The best locality to study the setting of the graphite deposits is the enclosing schist and gneiss rocks in Rautalampi and Käpysuo areas, which are situated in the Savo Schist Belt (SSB), and adjacent to the Archean craton (Lahtinen, R. 1994).
The Raman spectra were obtained from 35 petrographic thin sections of graphite-bearing rocks and 6 polished sections of cleaned graphite flotation concentrate. It was therefore possible to perform in situ point measurements and detailed studies on the textural relationships between graphite flakes and the surrounding mineral matrix. Raman investigations of graphite flakes were performed using a Renishaw inVia Qontor confocal Raman microscope w/ Leica DM 2500M 5x, 20x, 50x, 100x, equipped with a multiline argon-ion laser (785/532 nm) at the GTK Mintec mineral processing laboratory, Outokumpu (Fig. 1). Spectra were collected using the 532 nm laser at room temperature in backscattering geometry with a laser power of about 5 mW (to avoid graphite damage) and a spectral resolution of approximately 2 cm-1. Spectra were calibrated using the 520.6 cm-1 line of a silicon wafer.
Rock specimens were also studied using optical microscopy, scanning electronic microscopy (SEM), X-ray powder diffraction (XRD) and X-ray fluorescence (XRF). The graphite flotation was carried out by combining a simple rougher flotation step with five stages of cleaning in the laboratory of the Geological Survey of Finland (GTK) at Outokumpu. Figure 2 illustrates the experimental procedure of graphite mineralogy and the beneficiation process.
Graphite was found in two main rock types in the sampling area: quartz-mica schist and feldspathic biotite gneiss (Fig. 3a, b). The petrography studies indicate that the graphite-bearing rocks consist of quartz, feldspar and graphite with biotite. The feldspar is variably retrogressed to sericite, and biotite is retrogressed to chlorite (Fig. 3c–f). The graphite flakes vary in size and are up to 1.2 mm in length (Fig. 3c, d). The flakes are both evenly distributed in the rock and concentrated in fractures and along the foliation. Three graphite morphologies were observed: (1) euhedral to subhedral, large (>1 mm) and tabular flakes (Fig. 3c); (2) subhedral, small (0.2–1 mm) deformed graphite flakes intergrown with chlorite (Fig. 3d, e); and (3) fine-grained, or less commonly, acicular, highly lustrous graphite grains (Fig. 3d). The first two morphologies locally have alkali feldspar reaction rims in contact with plagioclase and quartz, and commonly have biotite intergrowths (Fig. 3c, d). The fourth morphology is non-pleochroic and oriented parallel to the foliation (Fig. 3d). The SEM images also demonstrate that all the samples consist of flaky graphite, i.e., that each graphite flake consists of several layers, with regular and irregular flake edges and clean flake surfaces (Fig. 3e, f).
X-ray diffraction data on flake graphite from Rautalampi and Käpysuo yielded interlayer spacings between successive carbon layers (d002) very close to that of the ideal hexagonal graphite structure. XRD results indicated minor differences in the interlayer spacing of graphite, ranging from 3.352 to 3.357 Å depending on the crystal morphology. From these values, the crystallite sizes along the stacking direction of the carbon layers within the structure are in the range of 1200 to 750 Å.
The X-ray fluorescence (XRF) analysis for the raw ore and contents of the gangue minerals is presented in Table 1, showing that the main compositions are SiO2, Al2O3, Fe2O3, CaO, K2O, MgO, SO3 and Na2O. In addition, the raw ore was analysed to have carbon content of 15.5%.
Table 1. Chemical and mineralogical composition of the raw ore (wt%).
The Raman shift for graphite is divided into first- and second-order regions after Reich &Thomsen (2004). The first-order region lies in the range of 1100 to 1800 cm-1, and the main graphite band, the G band, is at ~1582 cm-1. This band is inherent in graphite lattices. For more poorly crystalline graphite, additional bands are recognizable at ~1355 cm-1 and ~1622 cm-1. The band at ~1355 cm-1 is referred to as the main defect band (D1 band). This band occurs when defects are present in the carbon aromatic structure (Beny-Bassez & Rouzaud, 1985). It is also sensitive to graphite intercalations (Dresselhaus et al., 1988). The D2 band at ~1622 cm-1 appears as a shoulder peak of the G band and is also absent in highly crystalline graphite (Beyssac et al., 2002).
The second-order region from 2200 to 3400 cm-1 includes several bands at ~2400 cm-1, ~2700 cm-1 and ~2900 cm-1, depending on the degree of graphite crystallinity. The S1 band at ~2700 cm-1 splits into two bands at high crystallinities. It is therefore the most important indicator band for graphite crystallinities in the second-order region.
In general, Raman spectra for well-crystallised graphite include the existence of D1 and D2 bands in the first-order region (Wopenka & Pasteris, 1993). Thus, the relative intensity ratio of D and G bands (R1 = D1/G) can be used as an indicator of the degree of graphite crystallinity, and these values can be applied to calculate the La value of the crystal size (Tuinstra & Koenig, 1970; Pimenta et al., 2007). To estimate the peak of the metamorphic temperature, Beyssac et al. (2002) employed the parameter R2, defined as the area ratio (R2 = D1 ⁄ (G + D1 + D2), and proposed the formula TGr (°C) = −445 x R2 + 641 as a thermometer for Raman spectroscopy of carbonaceous material (RSCM) for regional metamorphic rocks in the range of 330–640 °C. Spectral parameters were determined by a background fitting process and the corresponding data are presented in Figures 4 and 5 and Table 2. The dataset of Table 2 includes mean values for the centre position, the FWHM of the D1 and G bands, values for the D1/G intensity and peak area (D1⁄ (G + D1 + D2) ratios, the La value and the calculated graphitization temperature.
The average intensity (R1) and peak area (R2) ratios for the studied graphite flakes in more than 50 graphite-bearing rocks range from 0.09 to 0.90 for R1 and 0.18 to 0.48 for R2. As the degree of graphitization increases, the graphite band (G band) in the Raman spectra becomes sharper and the disorder band (D band) derived from turbostratic graphite structures becomes weaker relative to those of low-grade graphite (Nakamura & Akai, 2013; Bernard et al., 2010). Temperature estimates for the studied graphite flakes from the “graphitic schists” of the Rautalampi and Käpysuo areas in Central Finland range from 430–560 °C. In sample RTL_PH3_52.95, with the highest temperature of 560 °C, the Raman spectra of graphite flakes show a strong G band with quite a broad D1 band and an almost undetectable D2 band, implying that the graphite flake is well crystalline, and both R1 and R2 ratios show decreased values (0.09 and 0.18, respectively). We refer to this type of graphite metamorphosed at around 450 °C to 560 °C as high grade (Fig. 4a,b).
The shapes of the Raman spectra of graphite flakes for sample RTL_PH6_127.6 (Fig. 5) are very similar to those of high-grade graphite samples, but exhibit high intensities of D1 and D2 bands, while both the D1/G intensities and area ratios (R2) show abrupt increases (Fig. 5a, b). These results are in agreement with the suggestion above that the values of the D1/G intensity (R1) and area ratios (R2) display parallel trends, which increase along with the decreasing metamorphic temperature from 0.60 to 0.90 and 0.42 to 0.48, respectively. We refer to this type of graphite metamorphosed at around 450 °C to 430 °C as medium-grade graphite.
Figure 5 shows the relationships between Raman spectrum parameters, R1 and R2 ratios and the estimated temperature, with the R2 ratios having a decreasing trends with temperature. This indicates that the values of the D1/G intensity and area ratios show parallel trends, which decrease as a function of increasing metamorphic temperature from 0.9 to 0.09 and 0.48 to 0.18, respectively (Fig. 6a). It also implies that the graphitization temperature tends to increase as the graphite crystallinity increases. The values of the centre positions of the D1 and G bands slightly decrease with increasing metamorphic temperature from 1352 to 1348 cm−1 and 1581 to 1579 cm−1 (Fig. 6b).
Table 2. Average parameters obtained from the Raman spectra of thermochemically extracted graphite cuboids from different localities. R1 = D1/G peak intensity (i.e., peak height) ratio, R2 = D1/(G + D1+D2) peak area ratio, TGr (°C)= −445 x R2 + 641 (Beyssac et al., 2002).
|Samples||Peak Position||FWHM||R1||R2||La(Å)*||TGr (°C)*|
*La (Å) and TGr (°C) are calculated by ID/IG = C(λ)La (nm) (Tuinstra and Koenig equation) and the thermometer following Beyssac et al. (2002), respectively.
The modified RSCM thermometer is a promising method that can be readily applied to obtain metamorphic temperature estimates. Beyssac et al. (2202) established that the thermometer is relatively insensitive to the thermal resetting and provides reliable estimates of peak metamorphic temperatures. In the Raman spectra of most of the studied samples, the highly crystallized graphite flakes (R1 = 0.1–0.4) with a high temperature range of c. 480–560 °C are characterized by a low intensity of the D1 band. By comparison, the intensity of this band in low crystallized graphite flakes (R1 = 0.5–0.9) is significantly higher, with a medium temperature range of c. 430–470 °C, beingcomparable with that of the G band. The FWHM values of the G bands (FWHMG = 16 cm-1) of the graphite flakes are roughly two times lower than those of the D1 bands (FWHMG = 40 cm-1). This evidence clearly indicates that most of the studied graphite is of high crystallinity, irrespective of the degree of hydrothermal alteration.
Beny-Bassez, C. & Rouzaud, J. N. 1985. Characterization of carbonaceous materials by correlated electron and optical microscopy and Raman microspectroscopy. Scanning Electron Microscopy 1985(1), 119-132. https://www.researchgate.net/publication/279904217
Bernard S., Beyssac O., Benzerara K., Findling N., Tzvetkov G., and Brown G.E., Jr. 2010. XANES, Raman and XRD study of anthracene-based cokes and saccharose-based chars submitted to high-temperature pyrolysis. Carbon 48:2506–2516. https://www.sciencedirect.com/science/article/pii/S0008622310001892
Beyssac, O., Goffe, B., Chopin, C., Rouzaud, J.N. 2002. Raman spectra of carbonaceous material from metasediments: A new geothermometer. J. Metamorph. Geol., 20, 859–871. https://onlinelibrary.wiley.com/doi/full/10.1046/j.1525-1314.2002.00408.x
Dresselhaus, M. S., Dresselhaus, G., Sugihara, K., Spain I. L. and Goldberg, H. A. 1988. Graphite Fibers and Filaments, Vol. 5 of Springer Series in Materials Science, Springer-Verlag, Berlin.
Lahtinen, R. 1994. Crustal evolution of the Svecofennian and Karelian domains during 2.1-1.79 Ga, with special emphasis on the geochemistry and origin of 1.93-1.91 Ga gneissic tonalities and associated supracrustal rocks in the Rautalampi area, central Finland. In: Lahtinen, R. Crustal evolution of the Svecofennian and Karelian domains during 2.1−1.79 Ga, with special emphasis on the geochemistry and origin of 1.93-1.91 Ga gneissic tonalites and associated supracrustal rocks in the Rautalampi area, central Finland. Geological Survey of Finland, Bulletin 378, 1–128. Available at: http://tupa.gtk.fi/julkaisu/bulletin/bt_378.pdf
Nakamura, Y. & Akai, J. 2013. Microstructural evolution of carbonaceous material during graphitization in the Gyoja-yama contact aureole: HRTEM, XRD and Raman spectroscopic study, · Journal of Mineralogical and Petrological Sciences, 108(3), 131-143. DOI:10.2465/jmps.120625
Pimenta, M.A., Dresselhaus, G., Dresselhaus, M.S., Cançado, L.G., Jorio, A. and Saito, R. 2007. Studying disorder in graphite-based systems by Raman spectroscopy. Physical chemistry chemical physics, 9, 1276-1291.
Reich, S. & Thomsen, C. 2004. Raman spectroscopy of graphite. Philosophical Transactions: Mathematical, Physical & Engineering Sciences, November 15, 2004, vol. 362, no. 1824, pp. 2271-2288(18). https://www.ifkp.tu-berlin.de
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Text: Thair Al-Ani and Akseli Torppa
Thair Al-Ani completed his Ph.D. in geochemistry and mineralogy at the University of Baghdad in 1996. He has worked as a senior scientist at the Geological Survey of Finland (GTK) since September 2003. Dr Thair Al-Ani has over 14 years of experience of academic teaching at Tripoli University, Libya (1997–2001) and Baghdad University, Iraq (1988–1997). Currently, he is engaged in many projects focusing on GTK strategies relating to graphite, lithium and cobalt as raw materials in lithium-ion battery technologies and other applications for renewable energy.
Akseli Torppa completed his M.Sc. in geology and mineralogy at the University of Helsinki in 2003. He has worked at the Geological Survey of Finland (GTK) since June 2008. Akseli Torppa has 16 years of research experience in mineralogy, geochemistry, isotope geochemistry, Precambrian and applied geology, and mining environmental issues. Since 2018, he has worked as a member of the mineralogy research group at GTK Mintec in Outokumpu, using advanced research instruments and software such as MLA, XRD and Raman. A. Torppa’s current research interests include environmental geology and process mineralogy.