By combining blockchain with physical tracking technologies, raw materials can potentially be traced throughout their global supply chains. Physical tracking technologies enable observing how raw materials move within the physical world, whereas blockchain translates these events into the digital world with an immutable record. This paper presents a taxonomy of different physical tracking technologies and examines if and how the combination of these technologies render raw material supply chains more transparent. Although academic literature highlights the theoretical benefits of combining these transformative technologies, large scale projects are still in their early stages. Following a brief literature review, this paper leverages an empirical approach to classify different tracking technologies, their fields of application and limitations, as well as how these technologies can enable supply chain transparency. Obviously, there is no single technology that can fulfil all requirements along complex supply chains. However, the relevant combination of respective technologies can help bridge gaps by increasing transparency within supply chains. Full article

Buildings and infrastructures can absorb CO₂ from the atmosphere because of the carbonation process that affects the calcium hydroxide of concrete elements. The aim of this research project is to initiate the absorption at casting by adding dry ice pellets to cement-based mortars. Test results demonstrate that the flexural and compressive strength of the mortars are not modified by this addition. Conversely, due to the presence of CO₂, the standard deviation of strength reduces with respect to that measured in plain mortars. Thus, carbon dioxide can be considered a valuable resource that improves the mechanical behavior of construction materials. Full article

Greece is considered as one of the most common producers of gypsum-anhydrite in Europe. The low content of impurities of these evaporite minerals, their big reserves and the low cost of logistics costs makes them exploitable and applicable for a range of industrial uses. The current study endeavors to present the petrographic, mineralogical, geochemical and qualitative features of evaporite samples from seven selected localities of western Greece (Zakynthos Island, Filiates-Thesprotia, Etoloakarnania and Kyllini region) and Crete Island. The studied evaporitic rocks are classified as a mixture of gypsum and anhydrite, where gypsum predominates. Other minerals present in minor amounts include celestite ± calcite ± dolomite ± magnesite ± sanidine and quartz. Celestite (SrSO₄) was detected in all studied samples. The highest celestite value (13.5%) corresponds to the region of Filiates, indicating that this deposit is prosperous for further research and potential Sr exploitation. Significant focus is also given on the assessment of the evaporite whiteness with respect to their mineralogical and geochemical composition. The aforementioned data aim to serve the dynamic Greek calcium sulphate industry by enhancing the evaporites’ prospects of industrial use, providing potential applications for those not already exploited. Full article

Microbiologically induced corrosion (MIC) leads to the degradation/deterioration of concrete pipes, due to the formation of gypsum. Magnesium hydroxide powders may protect the concrete surface by maintaining alkaline pH values at the surface, or by neutralizing the biogenic produced sulfuric acid. An accelerated sulfuric acid spraying test in a custom-made spraying chamber used to examine the consumption of magnesium hydroxide coating, which was applied on poly (methyl methacrylate) plates, instead of applying it on concrete substrates. In that way, only the magnesium hydroxide coating can interact with the acid and can be examined separately. Surface pH measurements and the mass changes were daily conducted, during the four-day accelerated spraying test. The mineralogical phases of the surface were determined by using X-ray Diffraction (XRD) measurements. Full article

This study examines the removal of p-CBA via the application of heterogeneous catalytic ozonation in the presence of 13 minerals. The solids were used as raw materials or after hydrophilic/hydrophobic modification. The optimal minerals were zeolite, calcite, dolomite, and thermally treated talc. The kinetic study showed that the decomposition of ozone followed a first-order kinetic model for all ozonation systems, whereas the kinetic model of p-CBA removal depended on the materials that were applied. The catalytic degradation of p-CBA followed a second-order kinetic model, while in the presence of non-catalytic materials; the p-CBA abatement was in best agreement with the pseudo-second-order kinetic model, as single ozonation. Full article

Among the wastes produced in a refinery are solids containing water, in particular: (i) bottom sludge accumulated in storage tanks and (ii) sludge agglomerated during the processing of crude oil. Potentially useful industrial secondary resources, co-processed with clays lead to the manufacturing of novel ceramic building products. Among the expected advantages, resulting to industrial symbiosis, is the inclusion of ashes and residual metals from the wastes within the ceramic structure, leading to the inertization of inorganic ingredients, through the thermal processing of clay to building ceramic products. Full article

The Italian zeolitic tuffs have been intensely exploited by family companies and are used, mainly, as building, insulation and decorative stone, whereas the fine powder resulted during the cutting of the blocks is used for feedstock and soil amendment. XRD, XRF and SEM/EDS techniques have been applied to study the zeolitic samples collected from quarries of Naples, Bolsena and Sorano areas. Two different types of chabazite, have been identified; a Ca-rich and a Ca, Mg, K, Na-rich, both accompanying K- and Na-rich phillipsite probably due to the chemistry of the original volcanic glass, but also to the presence of alkali and alkaline earths-rich pore fluids. All tuffs studied exhibit shoshonitic affinity and trachytic composition. The occurrence of glassy tuffs above those zeolitized tuffs studied, is a characteristic model for an early zeolite diagenesis of the volcanic glass in open hydrological systems. Full article

The Pedersen Process was developed at the beginning of the 20th century as an alternative process to the Bayer route for producing alumina Al₂O₃. A successful operation in an industrial environment took place in Norway from 1925 to 1969. It ended due to economic reasons. Having a smaller environmental footprint (no bauxite residue) and the ability to handle alternative raw materials makes the approach promising for grappling with future challenges in Europe. This paper shows the status of the ongoing European Commission-funded work and the outline of a first industrial process concept. Full article

The increase in world population and the expected global development of the world economy after the COVID-19 pandemic will continue to impose unprecedented pressure on securing the supply of minerals. The World Bank report “Minerals for Climate Action: The Mineral Intensity of the Clean Energy Transition” finds that the production of minerals such as graphite, lithium and cobalt could increase by nearly 500% by 2050, to meet the growing demand for clean energy technologies. Many of these critical minerals are found in the deep seabed, the only place on earth where mineral resources have not been exploited yet. There is a strong need to ensure that these critical minerals will be extracted in a sustainable way, verifying the protection of the marine environment and biodiversity. The regulatory, financial and engineering challenges for deep sea mining are considerable, but in fact are not considered prohibitive, taking into account the remarkable achievements in recent years. On the other hand, it is evident that the existing modern ecosystem-based management approaches cannot be applied to deep sea areas without detailed knowledge of the individual species and ecosystems; most of the species living on the deep-sea floor remain unknown up until now. There is a need for the development of a new environmental management approach for each specific area. The successful procedures of Natura 2000 can be followed, and the necessary information on the existing environmental conditions has to be collected separately at every site for a minimum period of 10–15 years. Natura 2000, the world’s largest ecological network united under a single, uniform regulatory framework, is regarded as one of the conservations success stories in the global effort to protect biodiversity. Full article

Greece is gifted with geologic features that promote geothermal heat flow. Geothermal energy exploration began in the late 60s, culminating in the first geothermal energy law in 1984 and the introduction of geothermal energy as a mineral resource under the amendment of the Greek Mining Code. Since then, low- and high-temperature geothermal activities followed their separate ways, with a modest utilization of the energy product in the primary sector (agriculture, aquaculture) and attempts for electricity production stalled since the mid-1990s. The adoption of green policies by both the EU and Greece, the acceptance of global warming as an existing threat, the adhesion to CO2 reduction goals, energy efficiency and the application on renewable energy solutions as means to combat the increase in global temperature have led to an increasing interest in the utilization of the geothermal energy applications. This paper presents the new legal framework for geothermal energy established by Law 4602/2019, as introduced by the Greek Ministry of Environment and Energy, Directorate-General for Mineral Raw Materials and discusses its scope and goals set by the implementation of its provisions. The paper offers a roadmap to successfully test those new policies and regulatory provisions and, finally, it maps the interfaces of stakeholders and geothermal industry in an attempt to highlight the steps of the necessary administrative procedures towards the facilitation of viable geothermal projects. Full article

The pillar stability factor (PSF) is calculated in three different mining stages for a sublevel open stoping mining project located in northern Botswana. Several three-dimensional finite element models were developed by varying the stope span. Pillar strength was estimated using the Lunder and Pakalnis equation and pillar stress was obtained from the numerical models. As mining progresses, both the first and second mining stages meet the rib pillar stability factor requirement for safe extraction. Geometrical improvements are suggested in the mining layout for the third mining stage to achieve the required PSF, which is based on international practices. Full article

Machine learning is constantly gaining ground in the mining industry. Machine learning-based systems take advantage of the computing power of personal, embedded and cloud systems of today to rapidly build models of real processes, something that would have been impossible or extremely time-consuming a couple of decades ago. The widespread access to the internet and the availability of cheap and powerful cloud computing systems led to the development and acceptance of tools to automate resource modelling processes or optimise mine scheduling, using machine learning methodologies. The domain modelling system discussed in this paper, called DomainMCF, has been developed by Maptek, using artificial neural network technology. In the application presented in this paper, DomainMCF is used to model the spatial distribution of marble quality categorical parameters, and the results are combined to produce a final marble quality classification using drillhole and quarry face samples from an operational marble quarry in NE Greece. DomainMCF was made available for this study as a cloud processing service through an early access program for individuals or companies interested in testing its capabilities and suitability in various modelling scenarios and geological settings. The resulting marble product classifications are compared with those produced by the already established classification system that is based on a more conventional estimation method. The produced results show that DomainMCF can be effectively applied to the modelling of marble quality spatial distribution and similar domaining problems. Full article

The EU’s demand for numerous mineral raw materials is growing intensively, while the security of their supplies (mostly form outside the EU) is often at high risk. This is especially the case for critical raw materials (CRMs). Poland is now and may be in the future the most important supplier of numerous mineral raw materials to other EU countries. This is especially the case for coking coal, copper, silver and elemental sulfur. This article briefly evaluates the current and future possibilities for the supply of these raw materials from Poland to the EU market. Full article

In surface mines, various activities (e.g., excavations, loading and unloading of material, moving vehicles on unpaved haul roads, etc.) represent significant sources of fugitive dust. The estimation of dust generation from each individual source is a basic step in planning and implementation decision-making systems regarding the air quality of the surrounding area. Typically, this can be obtained by using emission factor or prediction-type equations. A detailed study was carried out at four surface lignite mines to determine PM emission factors and to develop the prediction-type equations of various surface mining activities. In this work, the data, method and results referring to the stacker, one of and the significant fugitive dust emissions source in mining operations are presented and analyzed. Full article

The gradual elimination of rich and surficial-located Ni reserves mandates the assessment regarding the gradual switch from open-pit mines to underground mining schemes. This could allow for the continuation of the steady ore supply and furthermore could assist in minimizing the environmental footprint of the exploitations. This paper investigates the possibility of adopting an underground exploitation scheme and provides data on the preliminary feasibility of the endeavor for the Vrysakia deposit that was selected as a model project. It was found that such solutions proved to be technically sound, also yielding considerable results from a financial viewpoint. Full article

Coal and lignite regions are on the way to reinvent themselves. In this work, three aspects related to the reclamation and exploitation of these mining areas are analyzed, focusing on the role of geotechnical engineering. Firstly, the slope stability of lignite excavations is examined during the water filling reclamation practice. Secondly, the effect of extreme rainfall is studied on the slope stability of abandoned lignite mines. Finally, aspects of the potential reclamation of a waste dump by a highway or a railroad are investigated. Overall, the three studies underline the importance of geotechnical engineering in the transition to a post-lignite era. Full article

Kaolin is an industrial mineral used in a wide variety of applications due to its crystalline structure, mineral and elemental composition. After kaolin undergoes heat treatment in a specific temperature range, metakaolin, which exhibits a strong pozzolanic reaction, is formed. This paper examines the effects of different kaolin qualities on the thermal activation process of metakaolin production. The qualities of kaolin depend on the impurities they contain, such as mica, feldspar and quartz. In this study, four different samples of kaolin are investigated. Each sample was heat treated in a lab-scale rotary kiln in order to study the chemical, structural and morphological changes that occurred and their influence on pozzolanic activity. The parameters being considered in the experimental process were the temperature and the duration of the treatment. Thus, the calcination process for each of the four kaolin types was carried out at 600, 650 and 700 °C for 3 h. The occurred changes were monitored using XRD, FTIR and DTA analysis. Additionally, the reactivity of all thermally treated samples was evaluated based on the Chapelle test. The results showed that the fewer the impurities, the easier the transformation of the material to metakaolin. The optimum result was the metakaolin, which originated from the purest quality of kaolin and was comparable to the commercial product. Finally, the pozzolanic activity of the thermally activated samples also depended on the purity of the kaolin. Full article

Magnesia is mainly produced from carbonate sources (magnesite (MgCO₃)), and seawater brines (MgCl₂). The calcination of magnesite and the precipitation of brine using quicklime (CaO) are processes that have significant CO₂ footprints, even before considering the burning of hydrocarbons required to meet the energy demand. There are also significant amounts of silica-based magnesia raw materials available worldwide, such as serpentine, dunite, and olivine. It is possible to produce synthetic MgO of high purity using a HCl-based process. HCl can be fully recycled and reused. If a carbon-neutral heating source such as electricity, synthetic fuel, or plasma is used for the pyrohydrolysis process, the result is the production of MgO via a carbon-neutral process. Full article

Surface mining activities support socioeconomic development but also cause significant landscape alteration and degradation. By definition, the concept of landscape requires observers; thus, the way mining landscapes are actually observed needs to be taken into consideration for mitigating visual nuisance from open pit mines. This paper utilizes eye tracking techniques for recording and rendering the actual attention patterns of observers, along with saliency models that ‘predict’ the focus of attention in mining landscape photographs. As it turns out, saliency models can aid in reliably anticipating the attention focus across a range of different mining landscapes. Full article

In this study, life cycle assessment and life cycle costing results about piezoelectric and thermoelectric materials for energy harvesters (EHs) are extracted from the literature and evaluated. This study serves as a basis for comparing current EHs with innovative EHs that will be developed within the Horizon 2020 FAST SMART project. FAST—SMART aims at increasing the performance of current EHs while reducing at the same time: The use of rare elements and toxic substances; resources and energy consumption; environmental impact and costs; paving the way for the adoption of new and more environmental-friendly systems for energy harvesting. Full article

In mine design and planning, the identification of an appropriate Post-Mining Land Use (PMLU) is necessary and crucial to achieve environmental quality, socio-economic renewal, and social acceptance of mining projects. In this context, Multi-Criteria Decision Making (MCDM) methods support decision-makers and stakeholders, identifying the relevant factors and criteria, so that, different available alternatives can be evaluated, compared, and contrasted with each other. With the vision to enable its wide application, 15 mine profiles are identified which, combined with selected MCDM methods and relevant factors, results in a Multi-Criteria Decision Analysis (MCDA) framework for PMLU. In this preliminary framework, the MCDM methods selected are SIMUS, TOPSIS, and SMARTER. They serve different problems and, therefore, are used in different profiles: SIMUS is applied to complex profiles, TOPSIS to the lesser ones, and SMARTER is used due to its capacity of assigning weights to criteria based on Ranking Order Centroid calculations. This preliminary MCDA structure gives the possibility to include the complexity (technical and decisional) and a participatory process, for all stakeholders involved concerning PMLU. Full article

The main goal of this study was to identify potential chemical elements present in three types of polymetallic mine waste, stored in the old mine site of São Domingos, located in the Iberian Pyrite Belt, Alentejo, Southern Region of Portugal. This study involves the characterization of potential resources in those mine residues, bearing in mind that its reprocessing can facilitate the environmental remediation and rehabilitation activities which are underway at the site. X-ray Fluorescence (XRF) and micro (μ)-XRF 2D mapping surveys were performed. Univariate and multivariate data analysis reveal that differences in compositions are mainly related with element concentration per type of waste. Image processing and clustering analysis allowed the recognition of distinct elemental spatial distribution patterns. Some of these residues, although classified as archeological-industrial heritage materials may present toxicity to the ecological environment and to human health. This fact enhances, therefore, geoethical doubts regarding its remining and exploitability. In this context, a multi-criteria decision analysis considering two geoethical alternatives was performed. Full article

The extensive consumption of aluminum, combined with the shortage of the existing raw materials, and particularly bauxite, necessitates the exploitation of alternative raw materials for the production of alumina. The present paper focuses on the possible use of kaolin, as an abundant, cheap and high-aluminum content raw material, in alumina production, via the application of the Aranda-Mastin technology in the leaching step. From this point of view, leaching experiments were conducted on untreated kaolin and thermally treated, metakaolin, applying atmospheric pressure, temperature of 90 °C and with an aqueous solution of a low HCl concentration as the leaching agent. Leaching, in the aforementioned conditions, is an industrially applied process, characterized by highly efficient aluminum dissolution in the case of metakaolin with low silicon dissolution at a short retention time, but with respectively lower achieved results for untreated kaolin. In order to raise the aluminum dissolution rate from untreated material, temporal and subsequently chemical intensification was applied. The analysis indicated a higher aluminum dissolution rate, up to 70%, with the application of a high acid concentration of leaching agent, performed for a long retention time that could be further improved. Full article

Mining activity is the second biggest producer of waste in the European Union (EU), so to develop processes that allow the reuse of waste and the consequent creation of markets for these secondary raw materials are relevant for a desirable transition to a circular economy. Copper waste such as cakes, tailings, pyrite roasting residues, or slags present very different physical characteristics and hazards. There are two important aspects to consider for the residue of hazardous determination and its reuse: the particle size and the leaching behavior. Also, the reactive or non-reactive property of the waste depends on their origin, which is important for new applications. Based on these parameters (and other specifics for each application), the intention of this paper is to review and study the different applications of copper residues, aiming for new possibilities of cement-based construction materials with added value that allow to economically justify the use of cement. Full article

The closure of surface mines is a complex framework characterized by extended reclamations of post-mining sites towards an environmentally friendly and sustainable land-use system development with beneficial returns to society and the economy. The paper demonstrates the critical mine closure problem, draws research questions, and introduces the IDEF0 (Integrated DEFinition Function) process modelling method as a low-cost and easy development tool for use by mining experts to perform strategic planning of sustainable mine reclamation and repurposing projects. A case study for the method applied in a Greek lignite mine is presented. Full article

X-ray transmission (XRT) and computed tomography (CT) was used on five samples from the Niaz porphyry Cu–Mo deposit in Iran, representing different alteration zones. Analysis of three-dimensional CT data revealed structural information and groups of elements with low, medium and high attenuation, which were assigned to minerals previously determined by scanning electron microscopy. Thus, the mineralization can be located, and the metal/waste ratio can be estimated, leading to more precise ore body modelling and process parameter determination. CT is useful for selected samples as it is time consuming. XRT can be used as real-time process on conveyor belts. Full article

This study focuses on the investigation of possible relations betweenthe physical mechanical properties of natural stones from various places in Greece, i.e., limestones, marbles, sandstones and schists. Specimens were prepared to perform laboratory tests according to the applicable EN. Overall and “by stone type” correlation equations were established between flexural strength under concentrated load valueswithout and either after freeze–thaw cycling or thermal shock, indicating a linear and a powerrelationship, respectively. A power function was establishedbetween flexural strength under a concentrated load and under a constant moment. Results have also shown that water absorption increases linearly with open porosity. Full article

Underground bauxite mining exploitation is a challenging environment for ventilation. In this paper, such a complex underground ventilation network is modeled in detail using the Ventsim software. The network and its characteristics are selected and developed through the software, followed by their calibration and validation against actual measurements of both airflow quantity and quality which have been carried out at the mine site. This model constitutes the base of the new ventilation design for the future mine expansion. The recommendations and the characteristics for the optimization of the new proposed design are finally presented in detail. Full article

The separation of graphite from cathode active materials containing Co, Ni, and Mn, and the metals Cu and Al by flotation was tested and evaluated with a black mass sample of crushed spent Li-ion batteries. The metals, Cu and Al, were mostly (>90%) concentrated by sieving into an oversize fraction (+0.25 mm). Graphite and the cathode active materials in the oversize fraction (+0.25 mm) were effectively separated from the metals, Cu and Al, by flotation. Pre-treatment by roasting at a temperature of 350–450 °C improved the flotation efficiency of graphite from the cathode active materials for the undersize fraction (−0.25 mm). Full article

Industrial minerals are at the forefront of innovation and play an essential role in many innovative applications. Their functionalities and properties make them very versatile materials which are essential to many industries. A combination of properties such as heat capacity, density, price, availability, and eco-friendliness are exceptional and crucially advantageous of industrial minerals utilisation as thermal energy storage (TES) systems. This technology stocks thermal energy by heating or cooling a storage medium so that the stored energy can be used at a later time for heating and cooling applications and power generation. In this context, the utilisation of industrial minerals as carriers for impregnating phase change materials (PCM) can deliver new innovative products acting as short-term energy storage systems for construction applications to the market. TES is a technology that can solve the existing mismatch of energy supply and demand and improve buildings’ system performance by smoothing temperature fluctuations, as well as improving the reliability of the heating and/or cooling source. However, the most recent publications in this area are focused on PCM-enhanced building components thermal and kinetics analysis rather than focusing on the building component scale. This study is focused on the industrial minerals-PCM application as part of the building’s envelope, aiming to determine the benefits for buildings in terms of thermal energy performance and renewable energy penetration based on real data, harvested by an intelligent monitored building in Lavrion Technological and Cultural Park operated solely for research activities. Full article

The effect of freeze–thaw cycling on the slip resistance of dimension stones was investigated. Slip and frost resistance of limestones, granites and marbles were determined via pendulum tester in dry and wet conditions and controlled freeze–thaw cycles, respectively. Unpolished surfaces under dry conditions (mainly granites and marbles) were positively affected by freezing-thawing. In wet surfaces no significant change was observed. Polished surfaces were not affected even after 100 freeze–thaw cycles. Electron microscopy showed increased wear, hence roughness, of unpolished surfaces after freezing–thawing; homogeneity of polished surfaces prevented slip resistance from being significantly affected. Full article

This paper presents a discussion on Quebec’s pegmatite lithium resources and potential markets. It also evaluates the opportunities of lithium battery production for electric vehicles (EV) in the province while reducing greenhouse gas emissions. The paper shows that mining Quebec’s lithium ore deposits would be sufficient to satisfy the province’s lithium demand and also for exporting abroad lithium-ion batteries. By considering only the projects whose final product is LMH or LCE, Quebec would be able to produce between 10 and 21 million lithium-ion batteries for electric vehicles with a greenhouse gas emissions footprint of only 43% of the international average value due to Quebec’s hydro power. Finally, considering Quebec’s lithium mining project economics, the increased future demand for lithium would render Quebec’s lithium pegmatite projects competitive compared with those reported for brine projects. Full article

The estimation of the stability conditions, over-breaks, and spalling failures, which could inflict potential external dilution, is a key parameter so as to ensure the optimal design of the exploitation and its cost effectiveness The research undertaken aims at correlating established empirical approaches for the estimation of the stability condition with numerical analysis that identifies and measures the depth of failure. A number of analyses have been conducted and the results obtained yield promising results that can be transformed to direct mathematical expressions applied for the early estimation of dilution rates. Furthermore, through the research, an initial proposal is made for a dilution-based stability graph that could be utilized for the early identification of dilution. Full article

The aim of this work is to highlight the contribution of geological maps and mapping to industrial scale design. To achieve this goal, the site selection of a new quarry area is used as an example. For the development of a new quarry, the materials to be mined must meet specific requirements, mainly acceptable quality, adequate reserves, environmental restrictions, and economic viability. Geological maps of various scales were used in all stages of this research project. Initially, geological surveillance maps (1:50,000), which formed the basis for the sampling, were used. Finally, this research project was completed with the detailed mapping of two candidate areas for the development of the new quarry. Full article

The Pedersen process is a method to produce alumina from Al-containing sources, and it is a more material-efficient method than the current commercial Bayer process, since the formation of bauxite residue (red mud) is avoided, and the bauxite can be holistically consumed. The smelting reduction (SR) part of the Pedersen process yields pig iron and a calcium aluminate slag, and the latter is a feedstock material for alumina extraction via alkaline leaching. In the present study, three different bauxite ores (Greek, Turkish and Jamaican) were smelted with lime to ease the process and control the slag chemistry and coke for the carbothermic reduction of iron oxides. The slags produced were analyzed with XRD, XRF, and EPMA to identify the phases and chemical compositions. According to the results, the slags composed of Al-containing leachable phases. Moreover, it is shown that the amount and distribution of both the leachable and non-leachable phases in the slags depend on the ore chemical composition. The results are discussed regarding the characteristics and potential leachability of the slags. Standard leaching tests were performed to examine the actual leachability. Full article

Mineral raw materials prices have been shown to be affected by macroeconomic factors such as aggregate demand and commodity-specific factors (e.g., supply shocks). In addition, it has been shown that certain mineral raw material prices co-move, meaning that they behave similarly during expansion and contraction phases of the international business cycles. In order to assess the behavior similarity of the prices of different mineral raw materials, we propose a method that utilizes extracted features of time series price data and unsupervised learning techniques to create clusters of price movements having similar long-term behavior. Full article

Radon (Rn), a natural colorless, odorless, noble radioactive gas, with a half-life of 3.8 days, is an important source of natural ionizing radiation. It originates from the initial concentrations of uranium and its transmuted daughters in rocks, soil, and finally, waters and tends to be concentrated in closed spaces such as underground mines. The concentration of radon in mines contributes significantly to the increase in the dose of ionizing radiation received by humans visiting, accessing, working in these areas. The comparison of radon concentration in active and inactive mining sites, its effect on human health, and the different concentrations’ upper limits, applicable by state, are discussed in this paper. Full article

The development of a truly circular economy necessitates the recovery and recycling of resources from secondary streams. In this work, we studied the extraction of metals from printed circuit boards (PCBs) using choline chloride: ethylene glycol deep eutectic solvents: Cu, Ni, Zn, and Sn were selectively extracted from the PCBs, with >75% extraction after 72 h for Cu, Ni, and Sn, and circa. 45% extraction for Zn. This solvometallurgical approach promises to minimize the use of water and acid/base reagents in processing. The results show a considerable ability to compete with current methods of metal extraction and therefore generate a strong potential to attain the goal of a sustainable circular economy via zero-waste green urban mining. Full article

Aqueous solvents, despite being effective in the electrodeposition of metals with positive reduction potential, fail to deposit metals with negative reduction potential due to their narrow electrochemical potential window. Deep eutectic solvents (DESs), a class of ionic liquids, are a promising alternative of inexpensive, biodegradable, non-toxic anhydrous solvents that present wide electrochemical potential windows. The present work reports on the potential of choline chloride/ethylene glycol DES in the electrodeposition of Fe–Mn alloys. Cyclic voltammetry tests showed that increasing the quantity of Mn in the bath composition decreases the deposition current of the alloy. Full article

Electrolysis experiments to produce Al-Sc alloys were carried out in galvanostatic mode using a cryolitic melt with a NaF/AlF₃ molar ratio of 2.2 at 980 °C, using both synthetic and waste feeds. After elucidation of the cryolite electrolyte bath chemistry when adding Sc₂O₃, small-laboratory scale trials allowed for the demonstration of the process and the study and for the optimisation of the electrolysis parameters. Experiments in large-scale electrolysis cells allowed us to run long-term trials in continuous operation, while the on-line monitoring of the cell off-gases ensured the environmentally benign performance of the process. The aluminium product obtained contained 0.6–2.6 wt% Sc, depending on the current density applied. The material is suited to prepare Al-Sc master alloys for 3D printing powders. Full article

Proper waste management is an essential part of the efficient use of natural resources and sustainable economic growth. One of the largest waste streams in the European Union and in Poland is waste from extractive industries. Appropriate treatment of this waste stream should therefore be a priority, based on the applicable waste hierarchy. The use of the waste management hierarchy was confirmed by the analyzed data. Despite the growing demand for mineral resources, the amount of generated extractive waste is decreasing and waste recovery is increasing. The paper presents the main challenges in the management of waste from the mining industry in Poland, taking into account not only the existing regulations but also future actions resulting from the Polish Road Map toward the transition to a circular economy. Full article

The production of Al-alloys is mainly based on electrolytic pure Al alloyed with the necessary other elements, which are added in high purity into the melt pool during smelting processes. This fact is responsible for high costs and emissions during aluminum production. The usage of aluminum scrap in its downstream production processes provides multiple benefits since it reduces the overall cost of aluminum production by preserving raw materials through the utilization of scrap streams. This work provides some indicative examples with the aim to propose and demonstrate alternative ways to exploit aluminum waste for the production of aluminum alloys. Full article

Future investment feasibility studies concerning post-mining repurposing utilities and economic transitions should focus on regional water resource management and the hydraulic protection of any utilities. Satellite images in different bands and Digital Elevation Models (DEM) of the Ptolemais basin were processed, leading to a more accurate estimation of the runoff ratio and percolation ratio. Furthermore, the saturated and unsaturated areas were delineated, leading to the recognition of potential artificial ground water recharge zones and zones where appropriate hydraulic protection measures are necessary. Full article

To tackle the challenge of bauxite residue (BR), generated during the alumina production, as well as to recover some of its metal content, three combinatory H₂-based processes were utilized. Firstly, Greek BR was mixed with NaOH to produce water soluble Na-aluminates and was roasted under pure H₂ gas in order to reduce the Fe⁺³ content. Then the first process combined water leaching and magnetic separation, the second water leaching and melting and the last included wet magnetic separation. The water media resulted in the dissolution of Na-aluminate phases and the production of Al, Na-ion rich leachates. From these, pregnant leaching solutions recovery of Al was 78%, 84% and for the third case it reached 91%. Concerning Na recovery, it could reach 94%. Both melting process and magnetic separation aimed for Fe recovery from the material. The former case however still needs to be optimized, here its concept is introduced. The magnetic fraction, after the dry magnetic separation, varied in Fe content from 31.57 wt.% to 38.50 wt.%, while after the wet magnetic separation it reached 31.85 wt.%. Full article

Pumice quarried by LAVA MINING AND QUARRYING SA from Yali Island, Dodecanese, is used in domestic and foreign markets mainly as concrete lightweight aggregate, masonry unit constituents, road substrate, and loose soil stabilization. It is a porous natural volcanic rock with low density, low thermal and noise transmission, and the highest strength among all the natural or artificial lightweight materials of mineral origin. Nowadays, pumice is of additional interest as it has a reduced CO₂ footprint because thermal energy is not needed for its expansion compared with the artificial lightweight aggregates. In this context, HERACLES GROUP in collaboration with Sika Hellas has launched a new product containing pumice stone under the brand name GUNITECH^®. GUNITECH^® is an innovative bagged material for spraying concrete applications. It is a ready lightweight concrete, for building repairs certified as EN 1504-3. Full article

The geological education in Greece is essentially rooted in the second half of the 19th century, since 1836, when secondary education was established in Greece. Although geology is referred to in all educational programs, its field was not taught before 1880, due to the lack of competent teachers and suitable books. Geological education in Greece was established as a ”necessary” science at the end of the above century, during Greece’s opening phase of mining activity. In particular, the first attempt to exploit lignite deposits began in Aliveri (Evia) in 1873, but the intensive exploitation in Aliveri began after the First World War, reaching an annual production of 23,000 tons by the end of 1927. Respectively, lignite mining began in Ptolemais in the 1950s and Megalopolis in the 1960s. In the present paper, the correlation of the lignite mining activity in Greece for electricity generation with the content of geoscience textbooks is investigated since it is widely accepted that education is directly linked to economic development. Full article

The Raw Materials (RM) sector is linked to Sustainable Development Goals (SDGs), impacting their implementation throughout the whole RM value chain (e.g., mining, processing, metallurgy, recycling, etc.). This study aims to identify and rank the most significant SDGs for this sector, from the perspective of key stakeholders, academics, university students, professionals, and industry representatives, in three East and South-East Europe (ESEE) countries: Poland, Greece, and Slovakia. Within this framework, 423 stakeholders from the above groups provided their views in a survey with structured questionnaires. The results were analysed, based on the stakeholders’ groups and the role of the sector in the countries examined. Overall, the SDGs 9-Industry, Innovation, and Infrastructure-, 8-Decent Work and Economic Growth-, and 7-Affordable and Clean Energy- were highly ranked by the stakeholders, indicating a strong link between these SDGs and the RM sector. Full article

The rapid penetration of Artificial Intelligence (AI) and all related developments of the fourth industrial revolution is paving the way for a more sophisticated production sequence that strives for higher quality, lower emissions and lower cost production. This work reviews and discusses these developments and correlates them with state-of-the-art changes in materials engineering. We highlight penetration paradigms of modern computation tools. These technologies sound very promising in terms of maximizing the production efficiency of modern industries and, thus, minimizing the required energy input, greenhouse gas emissions and leading the way to a more ecofriendly economy. Full article

The rapid technology advancement and the significant decline of investment costs in wind and solar energy generation have opened up a significant opportunity to build these facilities on closed opencast mines or mines in the phase of closure around the world, where large available areas are almost ideal for such projects. In that sense, it is necessary to give an analysis of the possible application of wind and/or solar energy production in the Republic of Serbia’s mines, as well as the dynamics of such a generally ambitious and long-term project with conceptual solutions. Full article

This study presents experimental results for the development of a process for the recovery of indium and gallium from EoL CIGS (CuGa_1−xIn_xSe₂) panels. The process consists of a thermal treatment of the panels, followed by a hydrometallurgical treatment, where quantitative leaching of In, Ga, Mo, Cu and Zn is achieved. The elements are subsequently separated and recovered from the leachate by solvent extraction. For the development of the process, samples of EoL CIGS PV panels were used, which contained a thin film of Mo (metal base electrode), sputtered on the supporting soda-lime glass and covered by the thin film containing In, Ga, Cu and Se (1 μm). These films were detected by SEM-EDS in polished sections. The thermal treatment at 550 °C for 15 min, in excess of air, led to the successful disintegration of ethyl vinyl acetate (EVA) and delamination of the thin film-coated glass from the front protective glass. The glass fragments coated by the thin film contained the following: Se: 0.03–0.05%; In: 0.02%; Cu: 0.05%; Ga: 0.004–0.006%; and Mo: 0.04%. Following thermal treatment, thin film-coated glass fragments of about 1.5 cm × 1.5 cm were used in acid leaching experiments using HNO₃, HCl and H₂SO₄. Quantitative leaching of Cu, Ga, In, Mo, Zn and Cu was achieved by HNO₃ at ambient temperature. The effects of pulp density and acid concentration on the efficiency of metal leaching were investigated. Part of Se volatilized during the thermal treatment, whereas the rest was insoluble and separated from the solution by filtration. Finally, the separation of the elements was achieved via solvent extraction by D2EHPA. Full article

At the end of surface mining activities, the remnant voids are of great concern regarding rehabilitating the final open pits. The investigation of the sustainability of pit lakes in post-mining regions constitutes a challenging research problem. This paper aims to highlight the effectiveness of pit lakes as a rehabilitation factor. In this framework, several cases worldwide and in Greece were examined in detail and evaluated. The results indicate that mine pit lakes must be evaluated as dynamic systems, natural or artificial, which demand rational mine water management to ensure their sustainability. Specifically in Greece, it is of great importance during the transition to the post-lignite era. Full article

The Pedersen process is an alumina production process, which combines pyrometallurgical and hydrometallurgical methods. In the pyrometallurgical stage, limestone is calcined and CO₂ is generated. This off-gas can be captured with a high CO₂ concentration. At the end of the hydrometallurgical process, aluminum hydroxides, like bayerite, are precipitated using CO₂. In this paper, experimental work on precipitation of aluminum hydroxides through the addition of a mixture of CO₂, O₂ and N₂ is presented. The parameters varied, as were the percentages of each gas and the temperature. The indicators measured were the time until the beginning of precipitation and the time that the precipitation lasts. These tests simulate the use of a smelter furnace off-gas in the precipitation stage of the Pedersen process and have shown promising results. Full article

This study aimed to investigate the statistical correlation between the static and dynamic Young’s modulus of prasinites, a metabasic rock type that outcrops at various localities in the southern part of the Attica peninsula. A total of 39 cylindrical specimens was prepared and an extensive experimental program was carried out to determine the static and dynamic deformational properties for each specimen. Using ordinary least squares regression techniques, a new empirical linear equation was established between the aforementioned properties that can be used in the study region, or elsewhere where metabasic rocks with similar characteristics are investigated. Full article

With growing demand for renewable and clean energy technologies, the need in rare earth metals is increasing. Scandium, which is often considered a rare earth element (REE), is a critical metal mainly used in solid oxide fuel cells (SOFCs) and high strength aluminum alloys used in aerospace and 3D printing applications. Furthermore, scandium supply is limited due to its scarcity and the high cost of its production in Asia and Russia while Europe has no production of scandium. Therefore, scandium extraction from alternative resources such as secondary resources located in Europe is of great concern. Within this context, this work provides a condensed state-of-art review of the issue of scandium recovery from industrial wastes. Priority was given to addressing the technological and economic challenges associated with the recovery of scandium from the said residues, with particular emphasis on the bauxite residue from alumina production, which represents nearly 5 million tons on dry basis per year in Europe. Full article

The current study presents an effort to develop a sustainable hydrometallurgical process for the recovery of copper from waste printed circuit boards (PCBs) to be applied at local small to medium industrial units. The process aims to separate and recover copper from filter dust produced during the crushing of PCBs using a hammer mill in a recycling facility. Due to the high plastic content in the dust (approximately 30% w/w), the metal fraction was separated gravimetrically, and the material originated consisted mainly of Cu (23.8%), Fe (17.8%), Sn (12.7%), Pb (6.3%), Zn (3.4%), Al (3.3%), Mn (1.6%), and Ni (1.5%). Prior to copper recovery, the dust was leached with HCl as a pretreatment step. During this step, more than 80% of iron, zinc, and tin were leached out. The resulting solid consisted mainly of Cu (37.6%) and Fe (10.7%), leading to a copper enrichment of around 60% in the powder. The leaching of copper was conducted in a two-step process using H₂SO₄ as a leaching agent with the addition of H₂O₂ as an oxidizing agent. The experimental conditions had low energy requirements (no heating or agitation needed). The leaching of Cu reached 98%. Despite the pretreatment step, the concentration of other metals (Fe, Zn, Ni) in the pregnant solution was too high to proceed to electrowining. Therefore, the organic solvent ACORGA M5640 was selected for the extraction of copper from the pregnant solution. The extraction was conducted in two stages at pH equilibrium 1.5, and the loaded organic phase was stripped with HCl in two steps. The strip liquor was suitable for electrowinning. Full article

In the quarry sector, the reduction of landfill material may be obtained not only by finding a suitable recovery of the material as a by-product, but also by identifying the best available cutting technique to be used on the basis of the physical, chemical, and mechanical characteristics of the stones. The choice of the best cutting technique could lead to high efficiency and performance, high quality of the cut surfaces, and a very low environmental impact by reducing energy consumption, decreasing the concentration of heavy metals in the sludge, and producing less waste. In this context, an analysis of the procedures for cutting different types of ornamental stones into slabs together with the evaluation of sludge production for the different cutting methods has been carried out. Two types of analysis were carried out in parallel: evaluation of the stones workability and calculation of the amount of sludge produced in the three different cutting technologies and from the cutting of blocks. A comparison was carried out on the quality of the sludge produced, on type and quantity of metals present, taking into account the different cutting technologies. The performed tests were: chemical analysis, magnetic separation test, and SEM analysis of the metal fraction. The study could provide stone producers with a technological, scientific instrument to identify the best cutting techniques for the processing of their stones, in order to obtain a high-efficiency process, optimize the recovery process, increase the economic advantages, and evaluate the possible reuse of the sludge through a proactive waste management strategy. Full article

Iron and steel production contributes to ~10% of global CO₂ emissions. In recent decades, different scenarios and low-emission pathways have been taken up by steelmaking industries with the collaboration of universities and research institutes to tackle this problem. One of the most promising novel methods to replace the current steelmaking process is the low-temperature electrolysis of iron oxide. This technology is currently being developed under the H2020 ΣIDERWIN project, a European project led by ArcelorMittal, the world’s leading steel and mining company. The ΣIDERWIN project aims at developing an innovative electrochemical process to transform iron oxide into steel metal plates. This process produces steel by electrolysis without direct CO₂ emissions. In this operation, electrical energy and iron oxide are converted into chemical energy consisting of separated iron metal from the oxygen gas. It is a disruptive innovation that entirely shifts the way steel is presently produced. One of the advantages of this process is the fact that, in addition to iron oxide (hematite), it is possible to feed this process with other iron-containing raw materials. An alternative raw material which is being studied to be used in this process is bauxite residue (BR), the waste material from the Bayer process for alumina production. The iron oxide of the conversion of bauxite residue to metallic iron is under investigation, and insights are showing that it could follow up the electrochemical route for sustainable iron production. This research deals with the effect of the current density and temperature on current efficiency comparing two different raw materials, pure iron oxide–hematite and bauxite residue. Full article

ROBOMINERS is a new project funded under the European Union’s Research and Innovation Programme Horizon 2020, which aims at employing a bio-inspired robot, focused on the prospect of mineral exploration and extraction within Europe. ROBOMINERS’ innovative approach combines the creation of a new mining ecosystem through the development of a bioinspired robotic miner prototype, able to explore and mine mineral deposits which are currently considered uneconomic due to their small size and difficulty of access. The main objectives of the project include the creation of a European database of potentially suitable locations for the deployment of this novel technology. The building of the pan-EU mineral deposits database is considered vital for the development of the project as it will provide essential information related to deposit type and commodities, spatial and temporal distribution, and location of exploration targets. Several deposits have been reviewed and examined in Greece as potential targets suitable for the ROBOMINERS technology, after considering the specific restrictions and requirements of the project. The main targets have been determined and arranged according to the different aspects required by the applicability of the ROBOMINERS innovative technology. Full article

Synthetic nesquehonite with a Mg(HCO₃)OH·2H₂O chemical formula is a solid product of CO₂ mineralization with cementitious properties. It constitutes an “MHCH” (magnesium hydroxy-carbonate hydrate) phase and, along with dypingite and hydromagnesite, is considered to be a promising permanent and safe solution for CO₂ storage with potential utilization as a supplementary material in “green” building materials. In this work, synthetic nesquehonite-based mortars were evaluated in terms of their compressive strengths. Nesquehonite was synthesized by CO₂ mineralization under ambient conditions (25 °C and 1 atm). A saturated Mg²⁺ solution was used at a pH of 9.3. The synthesized nesquehonite was subsequently studied by means of optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Impurity-free nesquehonite formed elongated fibers, often around a centerpiece, creating a rosette-like structure. The synthesized nesquehonite was mixed with reactive magnesia, natural pozzolan, standard aggregate sand and water to create a mortar. The mortar was cast into 5 × 5 × 5 silicone mold and cured in water for 28 days. A compressive strength of up to 22 MPa was achieved. An X-ray diffraction study of the cured mortars revealed the formation of brucite as the main hydration crystalline phase. Carbon dioxide mineralized nesquehonite is a very promising “green” building material with competitive properties that might prove to be an essential part of the circular economy industrial approach. Full article

The treatment of end-of-life printed circuit boards (EoL PCBs) presents a contemporary recycling challenge with significant environmental, economic and social dimensions. This reality has attracted interest in the development of sustainable treatment processes, founded on mineral processing and metallurgical processes. The present paper reviews the applications of mineral processes in the treatment of end-of-life printed circuit boards (magnetic, electromagnetic, gravity and flotation processes), highlighting their strengths, weaknesses and limitations in the processing of EoL PCBs. Full article

Phoshpogypsum (PG) is an environmentally hazardous industrial by-product of the fertilizer industry with an annual production of 300 Mt, with a utilization rate of only 15%. In this work, we propose a novel use-case for PG. The latter is combined with a commercial-grade paraffin to fabricate composite phase change materials (CPCMs), for thermal energy storage applications. CPCMs are fabricated following a comminution and sintering process. The fabricated materials exhibit a stable latent heat (75 J/g) after 96 cycles (25 to 100 °C), with a maximum average specific heat capacity of 1.54 J/gK at 60% paraffin content. The thermal conductivity is found to be 75% higher than pure paraffin, while the energy storage density is only 14% lower. Full article

The electrochemical behavior of Ti³⁺ in LiCl-LiF-TiF₃ salt was investigated by cyclic and square wave voltammetries at 853 K. Both methods confirm the presence of a single reduction wave of Ti³⁺ ions to metal, at a potential of −2.3 V vs. Cl₂/Cl⁻. The closeness of the potentials of TiC_xO_y dissolution and Ti³⁺/Ti⁴⁺ wave is an issue during the electrorefining of the anode. A low current density has to be applied to stay within the titanium oxycarbide dissolution and avoid the formation of Ti⁴⁺. The titanium deposition was studied by electrorefining of a titanium metal plate in LiCl-LiF-TiF₃ (0.62 mol/kg). The cathodic deposit analysis by XRD and SEM confirms the formation of titanium metal with an average grain size of 150 µm. The faradic deposition yields are above 85% and constant between 60 and 160 mA/cm². Full article

The most important Greek ornamental stone types are marbles, limestones, schists, slates, travertines and sandstones. Since ancient times, quarryinghas been connected to history and civilisation, i.e., the white “Pentelikon” marble being famous for the construction of Parthenon (Acropolis). Greek marble industry is a dynamic sector, among the top world producers of dimension stones, concerning both the volume of production and exports. This paper describes the current status of the major ornamental stone producing areas in Greece and presents typical average values of physical mechanical properties of the extracted stones, determined in LITHOS laboratory. Full article

The present paper gives the thus far unpublished results of a pilot-scale heap leaching test of a Greek low-grade nickel oxide ore, aiming at verifying, at a large scale, the amenability of Greek laterites to heap leaching by the HELLAS (Heap Leaching LAteriteS) process, developed at the National Technical University of Athens for the first time worldwide and patented by some of the authors as early as in 1991. The test was conducted at the site of Aghios Ioannis mine of G.M.M.S.A. LARCO in 2006–2008 and was financed and supervised by the Institute of Geology and Mineral Exploration (I.G.M.E). The ore sample, 800 t, was from the “Triada” deposit of LARCO, in Euboea, and contained 0.73% nickel, 0.06% cobalt, 35.6% iron and 15% silicon. The ore was ground to −18 mm and the leaching agent was 2N (100 g/L) sulphuric acid solution. The nickel and cobalt recoveries obtained at the time of termination but not completion of the test, after four leaching cycles and 114 days of irrigation, were 60 and 36%, respectively. The corresponding nickel and cobalt concentrations in the produced leach liquor were 3.4 and 0.17 g/L, respectively. The value of the ratio Fe/Ni in the leach liquor was 10/1, much lower than the value 45/1 in the ore, thus showing the selectivity of the leaching of nickel over iron in the Greek ores by the above method. The consumption of sulphuric acid was 66 kg H₂SO₄/kg Ni recovered. The preliminary feasibility study, that followed the test, confirmed the economic viability of the integrated HELLAS process for the low-grade nickel oxide ores of Greece. Full article

Bauxite Metallurgical Residue (BR) is a highly alkaline and very fine-grained by-product of the Bayer process for alumina production. Its huge global annual production has resulted in increasing accumulation of BR, causing deposition problems and serious environmental issues. RM contains oxides and salts of the main elements Fe, Al, Ca, Na, Si, Ti, and rare earths—REEs (Sc, Nd, Y, La, Ce, Ds)—many of which have been categorised by EU as critical metals (CMs). The valorisation of BR as a low-cost secondary raw material and metal resource could be a route for its reduction, introducing the waste into the economic cycle. REEScue constitutes a research project that aims to instigate the efficient exploitation of European bauxite residues, resulting from alumina production from Greece (MYTILINEOS SA), Turkey (ETI Aluminium), and Romania (ALUM SA), containing appreciable concentrations of scandium and REEs, through the development of a number of innovative extraction and separation technologies that can efficiently address the drawbacks of the existing solution. The consortium consists of three alumina producers from Greece (MYTILINEOS SA), Turkey (ETI Aluminium), and Romania (ALUM SA) and two academic partners from Greece (National Technical University of Athens) and Turkey (Necmettin Erbacan University). We present preliminary characterization results of three different BR samples that originate from the three aluminium industries, in respect of bulk chemical analysis (XRF, ICP), mineralogical investigation (XRD), and morphological observation through microscopy. Full article

Hydrogen will presumably become an important substitute for carbon as a reductant in the metallurgical industry for processes such as steel production. However, the challenge to supply enough CO₂-free hydrogen for metallurgical processes has not been resolved yet. This paper reviews different production technologies for hydrogen and their advantages and drawbacks. Additionally, it will highlight the development of plasma technology to produce hydrogen and carbon black which has been taking place at SINTEF during the last 30 years. Full article

The feedback from international practice has shown that the installation of photovoltaic (PV) parks on abandoned dumps is one of the best environmental and economical solutions. This paper discusses the site selection criteria for the installation of PV systems on dumps. When installing the PV systems, different environmental, technical, and economic criteria should be respected. The ground movement and combustion hazards in the dumps appear to be the main constraints and limitations for the installation of photovoltaic panels. This paper presents several examples of the installation of photovoltaic panels on coal-lignite dumps in France. However, the number of projects is still very limited compared to the identified potential. Full article

Rare Earth Elements and Yttrium (REY) constitute an important family of metals, with a wide range of applications and a massive impact on global industry. Studies have verified that the REY exist at significant concentrations in coal fly (CFA) and bottom ash (CBA). In the present contribution, the feasibility of CFA and CBA from the thermal power plant of PPC Meliti, Florina as a possible REY source is examined. Results are presented on the chemical and mineralogical analysis of the samples along with characterization of the initial material. Size separation results are also presented, as the first step in a subsequent beneficiation process for potential REY recovery. Full article

It is evident that the increased focus on energy transition, will increase the demand for gas as it is the transitional fuel to the net zero CO₂ emission era. The West Katakolo field is the only oil and gas discovery in Western Greece, and it is operated by Energean. The three offshore West Katakolo wells have defined both the oil and the gas zones, while onshore exploration wells have penetrated biogenic gas-saturated Plio-Pleistocene sands. This study assesses the gas generation potential of the local Plio-Pleistocene and Triassic sources using thermal maturity modelling based on the available legacy data, with limitations being addressed by running several case-scenarios. In conclusion, this study supports the generation of thermogenic and biogenic gas from the Triassic and Plio-Pleistocene sources respectively, demonstrating the importance of maturity modelling in hydrocarbon exploration, applied on the Katakolo case; a potential gas source to facilitate the energy transition in Greece. Full article

Grecian Magnesite S.A., located in Gerakini, Chalkidiki, N. Greece, is a magnesite mining company, which produces and commercializes several Mg-based products. For production purposes, water is applied in large quantities for several uses. As a result, 5 × 10⁶–7 × 10⁶ m³ of wastewater, consisting mainly of muddy water, is produced from the magnesite ore washing facilities each year. In this study, the environmental impact of mining and industrial activities is examined, and the water management issues are addressed through its recovery. Water recovery reaches up to 96% (v/v), whereas the remaining sludge waste is safely deposited in tailings ponds. Full article

The objective of this effort is to study the effect that the combination of fly ash (FA) with a liquid corrosion inhibitor has on the mechanical degradation of 316L rebars embedded in concrete specimens during salt fog testing for a period of four months, as well as the porosity of concrete. Partial replacement of Ordinary Portland Cement (OPC) by FA (0–25%) did not significantly affect the tensile properties of 316L except a small decrease in the elastic modulus and % elongation with FA increasing. Both FA and FA-liquid inhibitor combination resulted in significant reductions in the porosity of the reinforced concrete after 4 m of salt fog testing. Full article

A set of samples with different textures from the sedimentary Fe–Ni deposits of Central Euboea, Greece, were studied with XRD and SEM-EDS to investigate the relationships between phyllosilicates present. The deposits are characterized by the coexistence of smectite, corrensite, R0 mixed-layer chlorite-smectite and discrete chlorite, which indicates disequilibrium conditions. It is suggested that chlorite, the main Ni-host in the deposits, formed by conversion of smectite (nontronite and possibly stevensite), via corrensite and R0 Chl-Sme during diagenesis. This is the first report for chloritization of Fe-rich dioctahedral smectite during diagenesis. Full article

Neodymium-Iron-Boron (NdFeB) based permanent magnets are indispensable in today’s technology-driven society. Moreover, their use is likely to increase since they are key in clean energy applications such as wind turbines, hybrid/electric vehicles, and electric bikes. They contain critical raw materials as rare earth elements are used. Indeed, permanent magnets are considered strategic materials by the EU, and their recycling represents a potential secondary supply to decrease the import dependence. The VALOMAG project is developing a technical solution to recover rare earth (RE) based permanent magnets by dismantling end-of-life (EoL) products such as computer hard disc drives, electric motors, and generators from electric vehicles and wind turbines. It also assesses two short loop recycling technologies: Hydrogen Decrepitation (HD) or Hydrogenation–Disproportionation–Desorption–Recombination (HDDR) and strip-casting for high and medium quality magnet wastes; and hydrometallurgical processes for EoL low-quality magnets. Moreover, Life Cycle Assessment (LCA) and Process Integration with a Flowsheet simulation tool will integrate the whole recycling value chain (collection, dismantling, physical and chemical treatment options, and re-manufacturing) and assess the environmental impact and processes efficiency. A market study on the types and expected future quantities for the scrap magnets and the characterisation of the EoL magnets from hard disc drives (HDD) will be presented as preliminary results. Pre-treatment and sorting of 2.5 tons of NdFeB magnets scraps were carried out, and the two short loop recycling routes and the hydrometallurgical route are under investigation at the lab and pilot scale. The results will be used to develop a process integration and to assess the three routes through LCA. Full article

Six ordinary Portland cement (OPC) clinkers and one white cement clinker were analyzed with the Rietveld method, using ZnO internal standard (IC), to determine the presence of amorphous matter (AM). All clinkers contain abundant AM and have lower silicate phase contents when compared with the same clinkers analyzed without IC, whereas the abundances of the aluminate and ferrate phases were not affected by AM. The white cement clinker had the highest AM content. Determination of AM is important for complete characterization of the OPC clinker and might contribute to a better understanding of the mechanical properties of the clinker. Full article

The present work aims to map kaolin occurrences on the Kefalos peninsula, SW Kos Island, Greece, through the elaboration of ASTER satellite imagery. The island of Kos is located on the eastern edge of the South Aegean Active Volcanic Arc (SAAVA) and is characterised by its complex geologic structure. During Plio-Pleistocene, the voluminous eruption of the Kos Plateau Tuff was recorded on Kefalos; the largest quaternary eruption in the Mediterranean. Kaolin is the product of hydrothermal alteration of the Pliocene volcanic rocks with rhyolitic composition. Our study emphasises the usefulness of satellite imagery combined with the Mixture Tuned Matched Filtering (MTMF) technique to detect occurrences of industrial minerals, kaolin-group minerals in this case, either in terms of raw mineral exploitation or by mapping hydrothermal alteration. Full article

The concepts of sustainability and waste utilization have received urgent attention in the European construction industries. Material selection plays a vital role in the manufacturing process of sustainable building construction. The general objective of this study is the transformation of waste diabase mud into a value-added product. The diabase mud was characterized, and different parameters were selected for the cement, as well as the metakaolin in the mixture. This paper includes analytical research results of a geopolymer paste embedded with diabase mud waste material as its precursor, and a combination of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) as its alkaline activators to form a geopolymeric system. The compressive strength of the optimum mix sample was recorded as 14.0 MPa at 72 h. The embedding of a diabase mud into a geopolymer resulted in a viable composite for use in the construction industry. Full article

Underground coal mining Atmospheric Monitoring Systems (AMS) have been implemented for real-time or near real-time monitoring and evaluation of the mine atmosphere and related parameters such as gas concentration (e.g., CH₄, CO, O₂), fan performance (e.g., power, speed), barometric pressure, ambient temperature, humidity, etc. Depending on the sampling frequency, AMS can collect and manage a tremendous amount of data, which mine operators typically consult for everyday operations as well as long-term planning and more effective management of ventilation systems. The raw data collected by AMS need considerable pre-processing and filtering before they can be used for analysis. This paper discusses different challenges related to filtering raw AMS data in order to identify and remove values due to sensor breakdowns, sensor calibration periods, transient values due to operational considerations, etc., as well as to homogenize time series for different variables. The statistical challenges involve the removal of faulty values and outliers (due to systematic problems) and transient effects, gap-filling (by means of interpolation methods), and homogenization (setting a common time reference and time step) of the respective time series. The objective is to derive representative and synchronous time series values that can subsequently be used to estimate summary statistics of AMS and to infer correlations or nonlinear dependence between different data streams. Identification and modeling of statistical dependencies can be further exploited to develop predictive equations based on time series models. Full article

In the era of Industry 4.0, gender discrimination still exists especially in be male-dominated workplaces, such as the stone sector. Combating gender discrimination in the stone sector is a demanding task that calls for integrated planning and targeted interventions. This paper presents the results of the “WinSTONE” Erasmus+ project, aiming at the development of suitable training tools for the integration of women in the stone industry. Based on the main challenges, as well as on the emerging opportunities for women in the sector, a training methodology is being developed to deal with the actual needs. Full article

Despite EU climate objectives and raw material needs, there is a growing concern caused by the limited direct access to primary sources and supplies of valuable raw materials, and by the heavy reliance on imports. Member states are encouraged to design and implement effective policies to improve domestic access to raw materials and to promote green energy, thus advancing European competitiveness, particularly for high tech products, emerging innovations and quality of life. The Greek Ministry of Environment and Energy, Secretariat-General for Energy and Mineral Raw Materials (MRM), Directorate-General for MRM, as an important stakeholder in the management of the raw material value chain that focuses on developing and providing a transparent and stable regulatory framework for mining and quarrying exploration and exploitation, ensures its efficient implementation in line with the principle of sustainability and facilitates strategic investments in knowledge, technology and innovation, therefore enhancing development benefits to local communities and society more generally. Full article

The EU aluminium production from, e.g., bauxite is one of the backbones to support Europe’s green and digital transition. In support of sustainable bauxite exploration and mining, Laser Induced Breakdown Spectroscopy (LIBS) was used on the major facies of the karst bauxite deposits of SODICAPEI (Southern France). Our results showed that LIBS is a very promising technology to define the bottom and top layer of bauxite ores and to access critical parameters crucial for bauxite mining and processing. First LIBS tests were made on scandium standards to find appropriate Sc emission lines for future applications. Full article

Minerals and metals are essential to the economic and social development of our society, and they are critical to modern life. The continuous exploitation of mineral resources has led to a large amount of waste, which has a large impact on the environment. One of the main streams of wastes in mining is mine tailings, which are produced in mineral processing plants. The mining industry must enhance its contribution to achieving sustainable development by incorporating the sustainable development goals into its operations. The objective of this article is to define targets and indicators for mine tailings management to achieve the sustainable development goals, defined in the 2030 Agenda for Sustainable Development by the United Nations. The result of this study is a collection of indicators proposed to measure the progress of mine tailings management towards sustainable development. Full article

The mineral raw materials’ resource efficiency is currently recognized in Europe as the way for the future development of the European mining economies. With this aim, a West Balkan Mineral Register was created in the EIT Raw Materials RESEERVE Project, including Primary and Secondary Raw Materials of six Eastern and South-Eastern Europe (ESEE) countries, i.e., Albania, Bosnia and Herzegovina, Croatia, Montenegro, North Macedonia, and Serbia. Within the Project, a Strengths, Weaknesses, Opportunities, and Threats (SWOT) and Gap Analysis was also performed for the development of the raw material sector in the region. This paper summarizes the main strengths to be exploited, i.e., the significant geological potential, the presence of critical raw materials (e.g., Sb, Co, REEs) in primary and secondary raw materials, and the challenges to address, i.e., compliance of resources/reserves classification with international standards, integration of state’s mineral policy with spatial planning strategies, improvement of the business environment, capacity building of the raw materials workforce and enhancement of the public acceptance of the sector, in order to achieve the sustainable development of the mineral resources of the six ESEE countries. These opportunities comply with the objectives of the EU Raw Materials Initiative and are expected to contribute in the further enhancement of those economies in transition for the upcoming years. Full article

The treatment of Wastes of Electrical and Electronic Equipment (WEEE) is a significant source of secondary raw materials. Ferrous and non-ferrous metals, electronic equipment, and plastics are among these materials. One of the most common metals sourced out of WEEE is stainless steel. Dishwashers are common sources of stainless steel, so large amounts of stainless steel can be recovered from them. In this project, dishwashers were submitted to size reduction via shredding, and the shredded products went through a magnetic separator (which separates all the magnetic ferrous components), an eddy current sensor (which separates all the non-ferrous components) and an induction sorting sensor (which removed all the metallic fractions). This procedure led to the following two streams: one with stainless steel, boards, and cables and another stream mainly including plastic. In the next stage, the stainless-steel stream passed through a high-intensity magnetic separator, leading to a magnetic and a non-magnetic stream. Thereafter, hand sorting was applied to both streams which aimed to increase the recovery from each stream. Full article

Calcium aluminate slag produced by the aluminothermic reduction of silica is tested as a candidate raw material for the hydrometallurgical production of pure aluminium chloride hexahydrate (ACH) through leaching with hydrochloric acid. The crystallization of ACH follows by sparging the pregnant liquor with hydrochloric gas. Almost total extraction of Al is achieved with the use of azeotropic HCl acid solution (5.9 M) at 80 °C and 1 h retention time. A pregnant liquor with approximately 20 wt% AlCl₃ is produced as a base for ACH crystallization by sparging it with gaseous HCl. The ACH produced is re-dissolved and crystallized three to four times until high purity is achieved. High purity ACH acts as a precursor for producing High Purity Alumina (HPA), a high added value material used in LEDs and lithium-ion batteries and other niche applications. Full article

Scandium (Sc) applications in solid oxygen fuel cells, aeronautics and heat exchange systems are forecasted to increase significantly without a sufficient continuous Sc supply for Europe. ScaVanger is an EU project for upscaling Sc extraction and purification technologies from various TiO₂ pigment production residues. High purity Sc₂O₃ and ScF₃ will be produced at competitive prices for the EU market. The ScaVanger process is expected to result in a 10% higher production rate and higher product purity as processing starts with a unique cleaning process of actinides. The first plant at a major European TiO₂ pigment production site will be supplying about 30 t/a of Sc₂O₃. Full article

Various anti-corrosion coatings used on commercially available NdFeB-type magnets were comparatively examined for their durability and suitability for magnet reprocessing by hydrogen-assisted recycling (HPMS). Layer thickness and structure were determined by systematic microstructural analysis, and a standardized corrosion test was used to assess the durability of each layer. Chemical composition of the coatings was analyzed using SEM/EDS and ICP-OES. HPMS behavior was investigated using in situ video monitoring. The results of the presented investigations are an important contribution for the implementation of a sorting and labeling system to support and facilitate a commercially viable recycling of permanent magnets on an industrial scale. Full article

Almost all post exploitation open pit mines in the world are shaped as a final reservoir intended to be filled with water. In Europe, the creation of water lakes is the most common way of reclaiming post open pit mines. The safety and the security of mine lakes is one of the priorities of mine regions. One of the main hazards identified is the slope stability of lake banks. To develop a reliability methodology for assessing the long-term stability of flooded open pit mines, a large-scale numerical model of the lake was carried out and was applied on Lake Most, which is one of the largest mining lakes in Europe (Czech Republic). The large-scale numerical model was built, based on the site observations, large scale LiDAR data and geotechnical data. The results highlighted the reliability of the methodology to combine the geometric model with the geological model to create a large-scale numerical model, and to identify local and potentially instable zones. Full article

Resource estimation is commonly performed in separate domains that are defined using different criteria depending on the type and geometry of the deposit, the mining method used, and the estimation method applied. The validity of estimation domains can be critical to the quality of produced resource estimates as they control various steps of the estimation process, including sample and block selection. Estimation domains also affect statistical and geostatistical analyses because they define what estimation practitioners will consider as statistically separate distributions of data. Sometimes, samples from different estimation domains share similar grade properties close to the contact between domains, a situation known as a soft boundary. In such cases, it can be useful to include samples from different domains at short distances from the boundary. Contact profile analysis is a technique that allows for the measurement of the relationship between grades on either side of the contact between two estimation domains. As discussed in the study presented in this paper, contact profile analysis can help validate the defined estimation domains and control the application depth of any soft boundaries found between domains. Full article

A novel roofing tile was developed containing various types of nanoparticles of titanium dioxide (TiO₂). Experiments were conducted using three types of TiO₂ nanoparticles with and without polyethylene glycol (PEG). All types of newly developed nanomaterials were characterized using X-ray diffractometry. Particle size distribution analysis was performed and specific surface area was determined using the Brunauer–Emmet–Teller method. SEM imaging was used for the morphological characterization of nanoparticles. Commercial ceramic roofing tiles underwent a dip-coating procedure to obtain the desired photocatalytic surface. The TiO₂ anatase samples exhibited greater surface areas of nanoparticles, thus providing potentially the highest photocatalytic efficiency. Full article

Bauxite residuals from abandoned mining sites are both an environmental challenge and a possible source of secondary raw materials. Processing of multispectral and hyperspectral images with the best available techniques can help to produce multiscale spatial maps of elements inside and around the mining sites. The authors propose a procedure for mapping elements concentration using multiple data sets at different scales and resolutions. A comparison between multispectral Sentinel-2 images and hyperspectral PRISMA processing is performed over some case studies of bauxite residues in the Mediterranean area. Specifically, a case study from Italy is composed regarding artificial canyons created by past artisanal mining activities and by stockpiles of extracted bauxite. Hyperspectral punctual measurements (spectroradiometer surveys) were taken in various zones of the bauxite site, where infield topsoil samples were also taken for X-ray fluorescence chemical analysis. Final concentration maps were estimated by performing geostatistical techniques. Full article

In this study we present a generic probabilistic risk assessment methodology to evaluate the risk associated with flooding process of a pit. We use the bow-tie analysis to analyze the critical events (we focus on slope failures) and the systemic risk assessment methodology to estimate the risk for the population, for the environment and for the infrastructure. Furthermore, we perform a spatial analysis of the risk by discretizing the affected area into squares, by estimating the risk in each one and finally by creating the risk map. The methodology is implemented by specialized software that has been created in a Matlab environment for the deduction of such risk assessments. The developed methodology was applied in the area of the pit lake Most in Czech Republic. Full article

In the context of the complete phase-out of lignite-fired power plants and the corresponding surface mines, the central priority is to ensure a fair development transition for the lignite mining areas. In the context of the installation of renewable energy system projects in the surface lignite mines of Western Macedonia, this paper aims to analyze the challenges for developing photovoltaic projects in areas with different characteristics and to propose solutions for selecting suitable areas, based on corresponding analysis. The investigated parameters cover a wide range of spatial criteria. The results contribute to a pragmatic transition to green energy generation involving a circular economy and sustainable development. Full article

This article presents a methodology applied to the design of a tailor-made program for teaching staff that addresses the needs of high-level educational institutions in the Eastern and South-Eastern European (ESEE) region. The tailor-made program was implemented as a one-week online course for 22 “Trainees” from six ESEE universities earlier in 2021. “Trainees” from six participating universities are currently developing acceleration programs, planned to occur continuously until 2024, increasing the percentage of the trained academic staff to >50% at each of the six universities. During that period, 240 students will benefit from 140 improved RawMaterials-related courses, improving their learning and understanding. Full article

In a world depicted by rapid growth and consumerism, where pressing societal issues such as, the critical climate crises, resources exploitation in developing countries and much more, it is essential to educate all citizens about raw materials, their uses and about responsible production and consumption. Developing life-long learning wider society programmes is an essential tool to educate the population starting with the youngest members of society (pre-school) to adulthood (life-long learning) with a special focus on the life-world orientation from a learners’ perspective. The wider society learning flagship project, ‘Raw Matters Ambassadors at Schools’ (RM@Schools), is an innovative programme funded by the European Institute of Innovation & Technology (EIT) which promotes science education and careers in the raw materials sector. Since the project’s commencement in 2016, it has gained stronger European representation with a current total of 32 partners from 18 countries. This includes the consortium members from a parallel funded programme, RM@SchoolsESEE. This project aims at extending best practices and diversifying the current portfolio to East and Southeast European countries. What makes this project so innovative is in the programme and individual learning pathways. Considering a multidisciplinary and cultural perspective, a framework was developed to assist in forming raw materials ambassadors through engaging programmes for school pupils from aged 10 up to 19 years old and through the development of educational hands-on toolkits that range from experiments to game-based tools and much more. In particular, and as a way to increase impact, the project aims to mentor teenagers from all educational disciplines between the ages of 14–19 years old to become ‘Young RM Ambassadors’. This approach utilises state-of-the-art teaching and learning methods resulting in peer-to-peer knowledge exchange and dissemination. Built into the programme is a continuous feedback loop that involves stakeholders from all sides of the knowledge triangle: educators, pupils, professionals and researchers. Full article

Tungsten is a scarce and valuable metal with a wide range of applications. Currently, the recovery of tungsten from scheelite concentrates involves the use of strong acids, alkalis, and/or high temperatures (roasting). Deep Eutectic Solvents (DES) are proposed as an environmentally friendly alternative for the leaching process aiming to extract the tungsten contained. In this work, high grade scheelite concentrate (W 57%) was the material used for the investigation. After an exhaustive DES screening, choline chloride-oxalic acid (ChCl/OA)-based DES showed the best leaching performance. An optimization of the leaching variables (temperature, time, liquid/solid ratio, ChCl/OA ratio) was carried out. A W extraction yield as high as 95% was achieved at certain operating conditions. Full article

A lack of lifelong learning courses on raw materials in Eastern and Southeastern Europe (ESEE) results in lower levels of innovativeness for this region’s professionals. The consortium of Dubrovnik International ESEE Mining school—DIM ESEE project (2016–2020) conducted several questionnaire campaigns in order to establish the main needs, challenges, and current status of innovation utilization among raw materials professionals in the ESEE region. Based on these results, the DIM consortium developed four annual 3-day workshops within the new project, DIM ESEE-2: Implementing innovations, which would secure relevant content delivered by expert lecturers for an affordable price. Full article

Although subsurface traps have been regularly explored for hydrocarbon exploration, natural gas and CO₂ storage has drawn industrial attention over the past few decades, thanks to the increasing demand for energy resources and the need for greenhouse gas mitigation. With only one depleted hydrocarbon field in Greece, saline aquifers, salt caverns and sedimentary basins ought to be evaluated in furtherance of the latter. Within this study the potential of the Greek subsurface for underground storage is discussed. An overview and re-evaluation of the so-far studied areas is implemented based on the available data. Lastly, a pragmatic approach for the storage potential in Greece was created, delineating gaps and risks in the already proposed sites. Based on the above details, a case study for CO₂ storage is presented, which is relevant to the West Katakolo field saline aquifer. Full article

The level of innovativeness within the higher education systems of east and southeast Europe and their graduates is still assessed as modest or moderate. Besides the general socio–economic context and the inherited institutional management types, this deficiency stems from a lack of generic skills crucial for increasing the innovation capacity of the universities. TrainESEE v.2 project suggests that significant changes should be already put in place within the applied teaching methodology, but also highlights the importance of developing project development and management skills, innovation, entrepreneurial skills, and finally competences needed to strengthen science to business cooperation. Full article

The feasibility of using low-environmental-impact leaching media to recover valuable metals from lithium ion batteries (LIBs) has been evaluated. Several deep eutectic solvents (DES) were tested as leaching agents in the presence of different type of additives (i.e., H₂O₂). The optimization of Co recovery was carried out by investigating various operating conditions, such as reaction time, temperature, solid (black mass) to liquid (DES) ratio, additive type, and concentration. Leaching with final selected DES choline chloride (33%), lactic acid (53%), and citric acid (13%) at 55 °C achieved an extraction yield of more than 95% for the cobalt. The leaching mechanism likely begins with the dissolution of the active material in the black mass (BM) followed by chelation of Co(II) with the DES. The results obtained confirm that those leaching media are an eco-friendly alternative to the strong inorganic acids used nowadays. Full article

This paper describes a study case of the Science and Technology Museum “Pedagogical Competence Programme” for students of the Department of Geology. It highlights an experimental approach of the museum for designing museum educational programmes with students. The museum succeeded from one side to develop a new program to offer to schools using participatory design and from the other to offer university students pedagogical experience through innovative, non-formal educational programmes, new ways to approach school students at all levels, cultivate their special skills, and enhance their knowledge, in order to familiarise them with the popularisation of science. Full article

Under the pressure of competition, primarily caused by the high price of carbon dioxide emission allowances, lignite production in Western Macedonia Lignite Centre dramatically reduced in the last decade. This development affects the ambient air quality of the greater lignite mine area, as evidenced by the reducing particulate matter concentrations and the number of exceedances of daily average concentrations per year. Moreover, differences in air quality measurements of monitoring stations, with regard to their distance from mining activities, now tend to be minimized. Based on these facts, it can be predicted that, after the phase-out of electricity generation activities, the ambient air quality will reach the levels that are typical for rural areas of Northern Greece well before the end of the mines’ land reclamation programs. Full article

This review presents a mineralogical and physicochemical comparison of coal seams located in the regions of Northwest and Central Greece. The comparison extends to the fly ash derivatives from the coal combustion for energy production, in the cases where data are available. Coal occurrences from Northwest Greece tend to exhibit higher content of rare earth elements (REE) compared to those of Central Greece. Moreover, fly ash products show similar trends in Light-REE compared to their coal parent rocks. The observed REE distribution seems to be correlated with the occurrence of specific minerals such as allanite, monazite, as well as with Fe-contents. Full article

Primary world nickel production in 2020 was 2430.7 kt Ni; 69% (1677.7 kt) of them came from oxidized nickel ores (laterites) and 31% from sulfides. Production-wise, 87.7% of the 1677.7 kt came from pyrometallurgical and 12.3% from hydrometallurgical processes. For a long time, Fe-Ni had a 20–40% Ni analysis, but in 2006 a new Fe-Ni quality came into the scene. This is the nickel pig iron (NPI) with 2.5–5.5% Ni that comes from laterite smelting in the blast furnace (B/F). Eventually, the advantages of the R/K-E/F process led to its dispersion in China and Indonesia and resulted in an NPI production with 3–12% Ni. The NPI production in these two countries climbed from zero in 2000, to 1060 kt Ni in 2020 and also stainless-steel production from 5.5% to 67.2%, respectively, of the world’s SS production. The integration of Ni industry with SS production, the economy of scale, the low labor cost, the high Ni content of Indonesian laterite, and the loose environmental laws, reduced significantly the NPI production cost. The addition of SS and/or electric energy production units for cost reduction has been adapted from other Fe-Ni producers, as well. Hellenic Minerals in Cyprus after two years of successful industrial tests is in the commissioning state of a Heap Leaching-Solvent Extraction-Crystallizer (HL-SX-CR) unit for NiSO₄.6H₂O production. The high demand for Ni and NiSO₄.6H₂O in the last few years has changed the prospects of Ni laterite hydrometallurgical processing. Regarding the R/K-E/F process used in Greek Fe-Ni, it is characterized by its worldwide acceptance and reliability (more than 77% of world Fe-Ni production comes from this process). Other advantages are the use of all types of laterites and fuels, it has a high metallurgical recovery, and the plant has its own port. However, it is a high energy-consuming process, and it does not recover Co. The Greek laterite, in particular, has the lowest Ni% among global Fe-Ni producers and because of this, electric energy (MWh/t Ni) and wages (wages/t Ni) per ton of Ni are high, making Larco’s viability difficult. The only way to overcome the issue with specific electricity consumption is to enrich the local ores by blending them with imported high grade Ni ores. Other negatives were the excessive electric energy price it had to pay to a dominant energy supplier and the very frequent changes of its administration. Full article

Pumice quarried by LAVA MINING & QUARRYING SA from Yali island, Dodecanese, is used, domestically and abroad, in applications such as concrete lightweight aggregate, masonry units constituent, road substrate, and loose soil stabilization. It is a porous natural volcanic rock with low density, low thermal and noise transmission, and higher strength among all the natural or artificial lightweight materials of mineral origin. Nowadays, pumice is of additional interest, as it has a reduced CO₂ footprint because thermal energy is not required for its expansion compared with artificial lightweight aggregates. In this context, HERACLES Group is launching a new product in the market under the brand name MASTER FLOOR^®, a commercial bagged product for floor or wall fillings with lightweight and insulating properties. Full article

Yeelimite is one of the main components of SulfoBelite (SB) and Calcium SulfoAluminate cements which are promising low carbon alternatives to Portland ones. In this study, stoichiometric yeelimite, obtained at different temperatures, was characterized by XRD, Q-XRD and SEM-EDS. Additionally, mortars of the synthetic yeelimite, with and without standard sand, were studied in terms of the development of strength over time. The main result is that high yeelimite content samples were prepared by mixing stoichiometric quantities of analytical-grade raw materials at 1330 °C for 3 h soaking time, followed by rapid cooling. Moreover, an increase in the formed yeelimite results in increased strength values that meet the requirements to be classified at CEM 32.5. Full article

A diesel particulate filter (DPF) can remove the diesel particulate matter from the incomplete combustion exhaust gases of diesel engine vehicles. The regeneration process of DPF is critical since the cost of the DPF/catalytic system for Euro 5/6 Diesel Cars has been calculated as half of the cost of the whole engine of the car. Nowadays, organic based solvents are used for regenerating filters while simultaneously revealing potential toxicity. As a result, there is a need for an innovative and environmentally friendly regenerating process. The studied reagents were citric acid, a deep eutectic solvent (DES) of choline chloride and lactic acid, sodium dodecyl-benzene sulfonate, and sodium hypochlorite. By this novel regenerating method, up to 90% of the organic compounds from diesel filters were removed. Full article

Three different types of biomass samples from Greece were studied (reed, olive kernel, and sawdust) and compared to lignite samples from coal deposits of Western Macedonia, Greece. All biomass samples exhibit higher calorific values (both as received and in dry basis) not only from the studied lignite but also from many other Greek coals. Despite its lower C content on a dry ash-free (daf) basis, the sawdust sample exhibits the highest calorific values, probably due to its lower total moisture content. It also exhibits the lower S and Cl content. As far as the ash content, reed and olive kernel presented higher values than the sawdust. Sylvite was identified in the biomass ashes. The presence of sylvite indicates the abundance of K in the organic matter that bonds with Cl and S during combustion. This explains the formation of arcanite that was identified in the reed and the olive kernel ashes. The presented differences in the composition of the ashes may lead to different environmental management or potential industrial applications. Full article

The research and development of high-entropy alloys (HEAs) and complex-concentrated alloys (CCAs) are growing rapidly, focusing on the enhanced properties of these alloys. However, so far, their manufacturing has not exceeded the laboratory scale. To meet this challenge, a combination of the processing characteristics and methods along with their sustainable production must be ensured. Moving towards a circular economy, this includes the utilization of low-cost, widely available scrap for the manufacturing of CCAs. Changing the raw materials, can ensure a cost-efficient production and paves the way to surpass major limitations in the industrial manufacturing of CCAs. Examples of a novel lightweight CCA design approach will be presented in this work. Full article

ERA-NET Cofund on Raw Materials (ERA-MIN) is a global, innovative and flexible pan-European network of research funding organisations, supported by EU Horizon 2020, that counts now with its third edition. ERA-MIN3 (2020–2025) builds on the experience of the FP7 ERA-NET ERA-MIN (2011–2015) and the still running H2020 ERA-MIN 2 (2016–2022). ERA-MIN aims to support the European Innovation Partnership on Raw Materials (EIP RM), the EU Raw Materials Initiative, the Circular Economy Action Plan and further develop the raw materials (RM) sector in Europe through funding of transnational research and innovation (R&I) activities. This is achieved through calls designed and developed specifically for the non-fuel, non-food raw materials sector. Full article

Circular Economy (CE) has grown prominence over the last two decades as a concept that presents solutions to some of the world’s most transversal sustainable development challenges and consequently its various business models such as Industrial Symbiosis (IS) have been identified as important tools for Sustainable Development (SD). Several authors have created a solid base to understand how CE contributes to SDGs achievement, nevertheless, there is a limited number of contributions in understanding how IS will contribute to achieving the SDGs. This paper aims to advance in the understanding of IS implementation within the scope of the achievement of SDGs, with a special focus on identifying which is the relevance of the IS to achieve the SDGs and which are the critical areas of contribution. To accomplish this objective, a research methodology integrated with a literature review and matching exercise was performed. The results of this study suggest that the extended IS implementation might collaborate with the achievement of 8 SDGs and 22 targets. Full article

It is now scientifically proven that specific categories of submarine raw materials, especially deep seas such as Mn and Fe oxides, polymetallic nodules, polymetallic sulfides (SMS) and some deep-sea sediment categories, can have significant potential for some critical metals for future use. One characteristic of these deposits is that although they often have lower Rare Earth Elements (REE) contents than the well-known land deposits, their sizes are very extensive, much higher than the land-based deposits. Therefore, the future use of these submarine formations as a source of REEs can be an important alternative to the exponentially growing demand for these strategic metals. These formations have significant potential to be a source of REEs in the markets when they are extracted as byproducts of the most critical metals such as copper, nickel, cobalt and manganese, from Mn nodules. To prove how realistic, the extraction of REE from those deposits is in market terms, we studied the economotechnical dimension and the potential or REEs compared to those of the well-known on-land REE deposits. Two studies are presented concerning the existing exploration pre-feasibility cases for REEs originated from two existing licences granted by the International Seabed Authority (ISA) in the Clarion Clipperton Zone (CCZ). The examination of these two cases has clearly shown that compared to the corresponding deposits of REE inland, the total basket prices of these submarine deposits are higher due to the higher contents of heavy REE such as Nd, Pr and Dy and Sm, Eu, Gd, Tb and Y in these marine deposits. Considering that the prices in the international markets for most of the REE oxides between 2019 and 2021 were very high, they gave these deposits even greater economic value. The significant advantage of the mining and metallurgical treatment of these manganese nodules and cobalt-rich manganese crusts is also related to the fact that REEs are not part of the crystal lattice of the minerals that host them, in contrast to what happens with land-based deposits. This makes their metallurgical processing more manageable and cheaper. This fact makes mining and metallurgical treatment economically favourable. On the other hand, the very low Th and U concentrations in these deep-sea deposits do not pose environmental risks in many well-known land-based REE deposits. Full article

Acid activation is a chemical modification of minerals and mainly smectites, in order to enhance their surface properties and reinforce their adsorption capacity for specific ions. Acid-activated clays and, more specifically, inorganic acid-activated calcium montmorillonites are mainly used in the bleaching process of vegetable oils, which are holding third place in the world food consumption after cereals and rice, in order to remove chlorophyll and other undesirable substances from the oils. This study proposes the use of oxalic acid for the acid activation of smectites, in order to modify their surface characteristics and create high-quality bleaching earths. In particular, aluminium and ferruginous smectites are treated with oxalic acid concentrations of 0.5, 0.7 and 1 M, and the structural modifications in the materials after treatment are observed through FTIR analysis, combined with the determination of the main structural metals’ extraction from the smectites. The results showed that ferruginous smectite is more susceptible to oxalic acid activation. The final product has developed vacant spaces in its structure to absorb other ions or molecules, although it retains the structure of smectite. Oxalic acid concentration of 0.5 M is sufficient for achieving this result. The materials produced through the oxalic acid activation are also compared with inorganic acid-activated smectites originating from the same deposits. Full article

Samples were collected from the argillic alteration zones in Sappes area, Thrace, Northern Greece and were examined for their mineralogical composition. Results showed that the sericite zone is the most widespread type of alteration in the studied area, followed by the transitional sericite–kaolinite zone and finally the pyrophyllite-rich zone. After determination of the spatial distribution of the different argillic alteration zones, selected samples were examined for their technological ceramic properties in order to evaluate their use in ceramic production. Preliminary results showed that after beneficiation processes, the clayey raw material from the alteration zones could be used in the ceramic industry. Full article

The area of the old arsenopyrites concentrate storage area is located at the Olympias Mining Facilities. The area was formed in the 1970s as a temporary storage area for the produced concentrate of gold-bearing arsenopyrite of Olympias. The total area is 11 hectares, and in the 1980s, the concentrate was removed from the site and arsenopyrite residues, which remained on the deforested surface, were major sources of pollution of the surface and ground waters of the wider area. The remediation and restoration works of this area were initiated by Hellas Gold as a priority immediately after taking over the Kassandra Mines property. After the restoration of the area, a nursery was installed with more than 1,000,000 plants. Full article

This work aims to deliver the objective of developing an appropriate set of mathematical models and a relevant software program to calculate the voltage distribution and energy consumption of a Hall–Héroult reduction cell, together with a deeper understanding of the complex physical and chemical phenomena underlying the alumina electrolysis process. The work involves an analysis of the basic principles governing the alumina reduction process, the presentation of the sets of the applied mathematical equations to predict the main electrolysis bath physicochemical properties related to the cell voltage, the mass balance of the main cell material inputs and outputs, the energy consumption of the electrolysis cell and the estimation of the cell voltage distribution along the various cells consisting of elements. All the mathematical models were included in an easy-to-use software to enable the aluminium cell operators and engineers to introduce and retrieve all the necessary cell operational data and study the effect of the key process parameters on the cell energy performance. Full article

Flooding of post-mining voids is one of the most common methods of post-mining areas reclamation. The article presents selected post-mining lakes investigated within the research project “Risk assessment of final pits during flooding” (RAFF), co-financed by the Research Fund of Coal and Steel and the Polish Ministry of Education and Science. The main objectives of the project are focused on the development of comprehensive models that can be used for risk assessment purposes. The innovative outcomes of the project will help to elaborate methodologies and guidelines to improve the safety and security of the flooding of post-mining open pits as well as sustainable management of the environment. In this paper, the results of bathymetry surveys carried out on pit lake Lubstów belonging to the PAK Konin Lignite Mine SA are presented. Full article

The Circular Economy begins at the start of a product’s life cycle. Throughout the life of a product, both the design phase and the manufacturing processes have an influence on sourcing, resource consumption, and waste creation. Article 5.2 (a) and (b) of the Extractive Waste Directive (2006/21/EC) encompasses waste avoidance or reduction and its harmfulness, as well as encourages the recovery of extractive waste via recycling, reusing, or reclaiming, if this is ecologically in conformity with current environmental regulations and technically feasible. After many years of developing Extractive Waste Management Plans by the sector, substantial knowledge has been established across the entire EU that should enable the identification of best practices that merit more widespread implementation across the extractive sector. Two years ago, the European Commission authorized a study to shed light on the practices that strengthen the spirit of the Circular Economy in the field of mineral extraction and its resulting waste streams, applied technologies, and their environmental impacts. This study is focused on (a) the harmfulness of extractive waste generation and its prevention or reduction, (b) the recovery of extractive waste (by recycling, reusing, or reclaiming), as well as (c) the assurance of short- and long-term safe disposal of extractive waste. It is based on the exchange of information among the Member States and extractive industries associations, as well as contact with EU mining companies to determine the best practices used. The present article focuses on achieving a Circular Economy throughout the whole life cycle of an extractive operation and summarizes eight best practices promoting the Circular Economy followed by companies from the extractive sector. Full article

Risk management is a methodology through which industry can proactively manage risks (inclusive of potential opportunities and threats), which is a common practice for operators all over the world. For the extractive industries, due to the highly variable operating parameters, such as site-specific conditions, geographical location, local environmental conditions, behavior and characteristics of the ore, and the geological background of the deposit, Risk management (RM) is an essential tool. Risk management as a management technique has developed significantly over the past 20 years, with an array of different tools and techniques being increasingly used globally to address risks pertinent to the extractive sector. The sustainability of the extractive sector will be guided by the environmental, occupational safety and health, and the societal approval of the extractive operations, including the processing plants. Risk management is a holistic approach that assesses all risks associated with the facility’s construction, operation, and closure. This article attempts to highlight the advantages of the implementation of RM approaches by the extractive sector and intends to promote the idea that RM can act as a vehicle to optimize the overall safety and environmental performance of the extractive sector. Full article

Ongoing research into geothermal energy sources in Greece has indicated various high enthalpy reservoirs that have not yet been exploited, although the Aegean Sea volcanic arc has proven to be of great potential. Nevertheless, the recent roadmap for the utilization of renewable resources suggests that within next decade, geothermal energy will provide 630 GWh of electric power annually. The development of the Milos field by 2025 is ongoing. Clearly, the need for expertise on the setup and utilization of geothermal numerical reservoir simulation models is major. In this work, we examine the capabilities of the two main options—distributed and lumped parameter models—for the mathematical description and optimization of geothermal energy fields. We investigate their applicability to the high enthalpy fields in Greece by treating history matching and energy extraction optimization. Additionally, we examine their contribution to field management aiming at minimizing the operating cost and environmental effects as well as ensuring sustainable energy production. Full article

The acceleration of the global production and consumption of electronic devices and the concerns related to waste electrical and electronic equipment (WEEE) motivated this research. Printed circuit boards (PCB) can be found in almost all types of electronic devices, and their composition contains heavy metals that can cause environmental impacts due to improper disposal. However, on the other hand, there are elements with added value, such as copper, gold, silver, iron, aluminum and other critical raw materials, such as tantalum, that can be recovered. Metal recovery can conserve natural resources since it prevents new minerals from being extracted, being a great contribution to the circular economy. In this research, the PCB element composition was initially determined through the scanning electron microscope analysis. Then, the PCB was shredded in a cutting mill and classified in grain size classes by sieving. Afterwards, magnetic separation has been performed together with gravity and electrostatic separation of the non-magnetic fraction. In gravity separation, the metal recovery was satisfactory for the particle size −0.6 + 0.3 mm and for the particle size −1.18 + 0.6 mm. In electrostatic separation, the efficiencies obtained were higher for the smaller particle size (−0.3 mm). Full article

In this study, the application of adaptive fuzzy inference systems (ANFISs) and artificial neural networks (NNs) for grade and reserve estimation of a copper deposit was studied. More specifically, a feedforward NN with backpropagation and two Sugeno- type ANFIS were developed for grade and reserve estimation. Borehole assay data were used for training, validation, and testing of the NN and ANFIS. Grade estimates and tonnage–grade curves were produced and compared to those obtained using a geostatistical approach (Kriging). Full article

Serpentinized peridotite samples—considered nowadays as deposited waste at the magnesite mine of Gerakini (Chalkidiki, N. Greece)—were collected, and their chemical and mineralogical characterization analyzed with Energy-Dispersive X-ray Fluorescence (ED-XRF) and X-ray Diffractometry (XRD). Dry magnetic separation was used as a convenient enrichment method; however, no significant effect was shown in the chemical composition of separated (magnetic and non-magnetic) fractions, except for small increases in the olivine, antigorite and enstatite contents, which were observed in the non-magnetic fraction. Finally, the calcination of ground peridotites at 1520 °C, with the addition of CaO, Al₂O₃ and SiO₂, presented a negative effect on the structure of the products with regard to their main refractory properties. In contrast, the addition of Cr₂O₃ and ΜgO mineral oxides showed improved refractory properties when compared with the initial material. Full article

In this study, limestone (LS), kaolin (K) and bauxite residue (BR) were considered as potential raw meal ingredients for the preparation of ferrite-belite (cement) clinkers. A forecast of the mineralogical composition for the different clinker composition, based on the major oxides, i.e., CaO (C), SiO₂ (S), Al₂O₃ (A) and Fe₂O₃ (F) was obtained using thermodynamic modelling (FactSage). A phase field schematic representation was established for the three-component raw meal. The data obtained therein were used to compute the Bogue equations for the ferrite-belite cements. Based on this assumption, i.e., only four simultaneous linear equations each containing four different variables (crystalline phases) were used to formulate Bogue type equations. It was established that with increasing LS content from 33 wt% to 64 wt% and BR content decreasing from 66 wt% to 35 wt%, CF was only present at an LS content between 33–47%, followed by gehlenite up to LS content of 53% and rankinite at a LS content of about 55 wt%. Moreover, C₃A and lime were present in place of gehlenite and rankinite beyond LS content of 55 wt%. However, the belite and ferrite phases remained present throughout the entire clinker composition. Overall, this study provides the basic understanding required for the development of low carbon ferrite-belite clinkers. Full article

To enable the usage of non-ferrous metallurgy slags in alkali-activated materials (AAMs), the influence of the chemical composition of slags on durability must be better understood. In this work, two slags were synthesized with different MgO/(MgO + CaO) weight ratios to investigate the effect on the sulfate resistance (Na₂SO₄) of AAMs. Experimental results suggested that a higher MgO/(MgO + CaO) ratio does not lead to higher strength, but the trend of the mass change and compressive strength change of two AAMs is quite similar upon Na₂SO₄ exposure for 24 weeks. The leaching of elements (Na, Al, and Si) during Na₂SO₄ exposure is more significant in the early stage, while Ca leaching is more pronounced in the late stage. Full article

The treatment of spent nickel metal hydride batteries (NiMHs) of Lexus vehicles to recover nickel (Ni) and cobalt (Co) as well as rare earth elements (REEs) including La, Ce, Nd and Y was investigated. Co-extraction of Al, Fe, Cr and Cu has also been examined. Following batteries’ manual dismantling to remove metallic cases, outer plastics and current collectors, the remaining parts including cathodes of black coloured nickel (oxy)hydroxides, anodes consisting of a nickel-containing alloy (AB5 mischmetal type), and separators were simultaneously ground down to −5 mm using a hammer mill equipped with sieves. The fine (−1 mm) fraction of this product was further subjected to sulphuric acid leaching to recover the high-value elements contained. Acid consumption of 14 mol H₂SO₄ per kg of this fraction was found to be sufficient to decrease pH to less than 1. Leaching experiments were performed using 0.5, 1 and 2 M sulphuric acid solution at 5% pulp density and temperature 50, 75 or 95 °C. The optimum conditions for the extraction of all elements were 2M H₂SO₄ concentration and temperature of 75 °C with the exception of Ni extraction, which reached its highest value at 95 °C and 2M H₂SO₄ concentration. Extractions of 93.34% of Ni, 99.03% of Co and 100% of REEs were achieved at these conditions. Full article

Inorganic polymers are considered to have a much smaller CO₂ footprint than traditional Portland cements. The possible environmental impact reduction was calculated to be up to 77% of a CEMI ordinary Portland cement (OPC)-based mortar, while the CO₂ emissions were reduced by up to 83%. The highest contribution to the total CO₂ footprint of inorganic polymers is related to the manufacturing of alkali activators. Within this context, the current work discusses the synthesis of inorganic polymers made from Fe-rich precursor and alternative silicate solutions. The obtained results indicate that there is no significant difference between an inorganic polymer prepared from alternative and commercially available solutions, which confirms that the waste glass can be use as alternative raw material in the production of sodium silicate. Full article

The present study focused on investigating the high-temperature reduction of bauxite residue, also known as red mud. A series of reduction experiments on red mud was performed to investigate the influences of temperature (1400, 1450, and 1500 °C), reaction time (15, 30, and 60 min) and reductant addition (7 and 14% carbon). A reduction experiment using a combination of carbon and plastic in the form of linear low-density polyethylene (7% carbon and 5% LLDPE) was also tested. The experiments were carried out in a vertical tube furnace using a graphite crucible under an argon atmosphere. Phases formed after the reduction process was analyzed using a scanning electron microscope equipped with an energy dispersive spectroscopy detector. At 7% carbon addition for all reduction temperatures and times, the reduction process of red mud produced metal and slag. The metal mainly consisted of iron with main trace elements of Si, Ti, P, S, and V. The slag mainly consisted of Na₂O, Al₂O₃, SiO₂, CaO, and TiO₂ components with residual iron oxide of less than 3.5 wt.%. Increasing the carbon addition to 14% at 1450 °C significantly increased the Si content in metal up to 19.1 wt.% and significantly decreased Na₂O in slag to less than 0.1 wt.%. The experiment with 7% carbon + 5% LLDPE addition gave a similar reduction extent to the experiment with only 7% carbon addition. The combustion of the LLDPE occurred before the reduction took place, and hence the LLDPE did not significantly contribute to the reduction process. Full article

Scandium extraction from the Greek bauxite residue has been demonstrated at an industrial pilot plant at MYTILINEOS. This work comes as the result of the H2020 SCALE collaborative research project. By combining sulfuric acid leaching and II-VI Selective-Ion Recovery (SIR) technology, a 22 wt% Sc concentrate has been produced from the Greek Bauxite Residue that contains 70–100 mg/kg Sc. As detailed in this work, the year-long pilot campaign achieved low acid consumption, high Sc selectivity over Fe and Ti and high Sc-loading capacity of the SIR resin, setting the basis for a viable Sc extraction technology from bauxite residue. Furthermore, the neutralized bauxite residue from the leaching process can be used in cement production, enhancing the sustainability of the operation. Full article