Materials Proceedings

In situ analysis techniques of ore and drill core samples provide fast results that can be used to facilitate the decision-making process during the geochemical exploration of ore deposits. This study applies the use of two portable devices, pXRF and Laser-Induced Breakdown Spectroscopy (pLIBS), to a small manganese oxide deposit situated in the Rhodope metamorphic complex, Kato Nevrokopi, northern Greece. The study provides an example of exploration of a variety of manganese minerals, including Mn-oxides, Mn-carbonates, and Mn-silicates. It tests the accuracy of mineral identification using these two techniques. The application of pXRF helped in the elemental identification of critical trace metals in certain Mn minerals and showed that there is Ag enrichment in the ore, which is associated with the mineral hetaerolite (ZnMn₂O₄). From the LIBS analysis, it can be seen that Mn minerals with different Mn valences (+2, +3, and +4) display distinct spectra. This observation will be further examined by expanding the sampling pool of the spectra of manganese oxides. It is postulated that the presence of trace elements in Mn minerals may differ according to the valence of the Mn, which in turn affects the LIBS signals of the sample. Full article

Bauxite residue (BR), an alkaline industrial waste, is a major byproduct of the alumina production process known as the Bayer process. The Bayer process generates a byproduct known as bauxite residue (red mud). This residue was leached with sulfuric acid in a pilot plant of Mytilineos S.A to recover scandium. Scandium was selectively recovered in pilot-scale experiments using ion exchange. This process generated a raffinate solution containing various dissolved impurities such as aluminum, sodium, calcium, iron, and mainly sulfate ions. The regeneration of the raffinate solution can reduce the cost of the process and minimize the use of H₂SO₄. The potential of raffinate recycling as a technology for reducing the usage of H₂SO₄ in the leaching process was evaluated by neutralizing bauxite residue with a raffinate solution before the leaching step. This study aimed to investigate the feasibility of using a raffinate solution for the neutralization of BR, enabling its reuse and improving the process’s environmental sustainability. The neutralization process decreases the pH value of BR pulp with 50% w/v pulp density from 11 to 6. Experimental investigations were carried out to assess the leaching behavior of bauxite residue compared to neutralized bauxite residue (NBR) using sulfuric acid. The obtained results were compared to evaluate the effectiveness of NBR as a substitute for bauxite residue in the leaching process. The consumption of acid during the leaching of neutralized BR was three times less than the BR leaching. An X-ray diffraction (XRD) analysis of BR and NBR was conducted to determine the mineralogical phases of the materials. The results of the study provide valuable insights into potential ways to reduce the cost of the BR leaching process, while also improving its environmental impact by recycling valuable materials. Full article

CPG (CO₂ Plume Geothermal) has recently emerged as a promising technology to combine the extraction of geothermal energy with underground CO₂ storage, thus achieving double positive results. The idea is to inject CO₂ in its supercritical form to create a plume and replace the reservoir brine, which is continuously circulated to transfer heat from the reservoir to surface facilities. Apart from the positive aspects of this technology, including the reduced energy to inject and lift the working fluid as well as its enhanced mobility in the reservoir and reduced environmental footprint, there are also negative issues that must be handled by adequately studying the geological field/reservoir and appropriately designing the production system. In this work, we present a finite volume numerical simulation that can study a geothermal reservoir from its geological origin to the dynamic simulation of CO₂ injection and estimate the geothermal energy extraction. It is shown that the system performance is strongly related to the selected schedule, and optimizing it in conjunction with the related cost is of the utmost importance for the Final Investment Decision to be taken and for the viability of such multipurpose projects under a sustainable future. Full article

Supply risk and economic importance are the key aspects controlling the metals classified as critical. Several of the critical metals are also classified as rare based on their restricted geological availability. In Europe, numerous mineralizations have been reported as being enriched in critical, strategic, and rare metals, and could potentially facilitate the production of these metals as by-products. Within this context, this paper reviews the critical and rare metals incorporated in the vein-type mineralization hosted in the Vertiskos unit in Greece. Several Cenozoic polymetallic mineralizations hosted in quartz veins and metamorphic rocks, which are enriched in Cu–As–Pb–Bi–Ag–Au–Te or in Sb-W are being reported in the region. The polymetallic mineral assemblages are characterized by base metal sulfides—Bi-sulfosalts, Bi-sulfotellurides, and tellurides—associated with Au and Ag. On the contrary, Bi-Te mineral phases are lacking or are completely absent from the Sb-W mineralization. The highest critical metals enrichments are reported from Kolchiko and include Bi (995 ppm), Co (320 ppm) and W (844 ppm). Gold is up to 28.3 ppm in Koronouda, while Ag reaches up to 2433 ppm in Laodikino. Full article

Coal bottom ash is used globally in various applications in the construction industry to reduce its negative environmental impacts. In this study, the potential utilization of lignite bottom ash from four power plants in Greece in concrete manufacturing was evaluated through granulometric, chemical, and mineralogical analyses. The particle-size distribution of bottom ash obtained from dry sieving resembles that of sand, making bottom ash suitable for replacing fine aggregates in the production of concrete. Its chemical composition, determined with selective point analyses energy dispersive spectroscopy (EDS), reveals high amounts of silica and alumina indicating pozzolanic properties, and high calcium contents suggesting hydraulic/cementitious character. Mineralogical characterization, obtained from powder X-Ray diffraction analyses (XRD), displays the prevalence of amorphous matter, calcite, quartz, aluminosilicate minerals, and portlandite, implying a beneficial pozzolanic and hydraulic activity in concrete manufacturing. Full article

Risk management (RM) as a management technique has developed significantly over the past 20 years globally to address risks. RM is often linked to financial, reputational, and quality risks. The purpose of this article is to shed light on how the extractive sector manages environmental and occupational safety and health (OSH) risks through a number of interviews with extractive industries. These interviews were held as part of the European Commission project “Elaboration of Guidelines for Best Risk Management Approaches in the Extractive Sector” in order to investigate synergies between the areas of the environment and OSH for an effective and integrated risk management approach that stimulates improved performance, leading to overall risk reduction. The interviews revealed how the sector addresses risks, which methodologies are most used, and how risk management is applied in each of the main stages of the extractive value chain. According to these interviews, companies seem to actively search to find corrective measures. On an operational level, most extractive companies use a combination of RM tools and custom-made risk management practices, predominantly for internal use and not for licensing. The extractive sector believes that society’s acceptance is a key element to being licensed to operate. Thus, the management of risks from the perspective of providing high OSH standards and, at the same time, achieving the lowest impact on the environment are key to a productive operation. Full article

In this work, electrodialysis (ED) and electro-electrodialysis (EED) were investigated as technologies for the recovery of Sb from wastes and effluents generated during the pyrometallurgical processing of copper sulfide minerals and the hydrometallurgical treatment of low-copper-content mixed minerals. This work addresses the challenge of applying electrochemical methods for recovering these valuable materials and recycling highly concentrated acid solutions used in the latter separation stages of the electrorefining process. The electrochemical characterization of the solutions was conducted, and the electrodeposition of Sb and Bi was performed in electrochemical cells. Also, the implementation of membrane processes in the recovery of such materials was investigated. Full article

Acid sulfate waters originated from acid rock drainage (ARD), affecting the La Silva stream (El Bierzo, Spain), present anomalously high values of rare earth elements and yttrium (REY). These REY are maintained dissolved along the water stream as sulfate ions forming complexes like REYSO₄⁺ and REY(SO₄)²⁻. Negatively charged REY complexes seem to have an affinity for iron precipitates found along the La Silva stream and its tributaries since their surface is positively charged at this low pH. The presence of iron-oxidizing bacteria in iron precipitates addresses the possibility of their implication in this REY immobilization and its potential use in (bio)remediation and strategic metal industry applications. Full article

The aim of this paper is to study and compare the Global Reporting Initiative (GRI) standard widely used in the Sustainability Reporting of the Raw Material (RM) Industry with the recently emerged European Sustainability Reporting Standards (ESRS). The Non-Financial Reporting Directive (NFRD), 2014, that initially set the requirements for NFR to companies with more than 500 employees, will be replaced by 2024 with the new European Corporate Sustainability Reporting Directive (CSRD) 2023. As of 2024, large undertakings, as well as small and medium-sized undertakings that are public-interest entities, will be required to publish reports on their environmental and social impacts, replacing the NFRD. Within this framework, the present paper aims to review and compare the two standards, GRI and ESRS, given that due to the forthcoming Directive, a significantly higher number of companies, as compared to the entities subjected to NFRD, including large and SME companies of the RM sector, will have to prepare the procedures for the implementation of the new standards. Moreover, it has been reported that EFRAG-GRI organizations have started planning the new standard update. Taking into account the extensive use of the GRI indicators in sustainability reporting, the article highlights both their similarities and differences with the first set of 12 draft ESRS. From this study, it was mainly concluded that the two sustainability reporting standards present several similarities; thus, companies already using GRI are expected to seamlessly adapt to the new standard. Full article

Rare-earth elements (REEs), which are indispensable for high technology and renewable energy, are becoming more significant due to their distinct properties (e.g., catalytic, metallurgical, magnetic, etc.) and their diverse applications in a wide range of contemporary technologies, environmental initiatives, and economic domains. In the pursuit of an environmentally friendly, sustainable, circular approach, recycling and utilizing secondary rare-earth resources as potential reservoirs of REEs may present an alternative to primary mining, addressing future raw material demands. Secondary REE sources include various products such as fluorescent lamps, light-emitting diodes (LEDs), magnets, wind turbines, electric motors, and batteries. Powders used in fluorescent lamps contain approximately 3% phosphorus, and these powders comprise a high ratio of precious REEs such as Y, Eu, La, Ce, and Tb. This study involves the recovery of yttrium from end-of-life fluorescent lamps. The composition of the end-of-life fluorescent lamp was analyzed using X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques subsequent to grinding. The leaching process was conducted to investigate the effects of leach parameters on the efficiency of the reaction. In the subsequent phase of the study, a solution obtained with the optimum leaching efficiency was subjected to the purification of Y using the solvent extraction (SX) method. The effect of each different extractant and pH values on Y-recovery were investigated for SX process. Yttrium oxide powders were characterized by XRF and ICP(OES) techniques, and high-purity Y₂O₃ powders were obtained with high yield. Full article

The unique magnetic, optical, and electrical properties of rare earth elements (REEs) have become essential in modern high technology. Considering the necessity of technology, efficient management and utilization of rare earth resources are of great importance. Even though there are more than 250 rare earth minerals around the world, the number of minerals that can be economically processed does not exceed three. Among these minerals, bastnaesite has a significant impact on scientific advancement and social progress. This project aims to contribute to the establishment of a sustainable supply chain for REE in Türkiye and Europe by conducting research and development activities to leverage the utilization of REEs found in our country. The primary objective of this project is to extract rare earth oxides from complex ore in the Eskişehir Beylikova region, which holds the largest reserve potential discovered in our country, and to refine these metal oxides to produce metals that can be used in magnet manufacturing. The project encompasses five main work packages over three years: project management, ore enrichment, solvent extraction-based purification, utilization of REOs and metals in additive materials, and magnet production. Full article

To achieve the European milestone of climate neutrality by 2050, the decarbonisation of energy-intensive industries is essential. In 2022, global energy-related CO₂ emissions increased by 0.9% or 321 Mt, reaching a peak of over 36.8 Gt. A large amount of these emissions is the result of fossil fuel usage in the motorised equipment used in mining. Heavy diesel vehicles, like excavators, wheel loaders, and dozers, are responsible for an estimated annual CO₂ emissions of 400 Mt of CO₂, accounting for approximately 1.1% of global CO₂ emissions. In addition, exhaust gases of CO₂ and NO_x endanger the personnel’s health in all mining operations, especially in underground environments. To tackle these environmental concerns and enhance environmental health, extractive industries are focusing on replacing fossil fuels with alternative fuels of low or zero CO₂ emissions. In mining, the International Council on Mining and Metals has committed to achieving net zero emissions by 2050 or earlier. Of the various alternative fuels, hydrogen (H₂) has seen a considerable rise in popularity in recent years, as H₂ combustion accounts for zero CO₂ emissions due to the lack of carbon in the burning process. When combusted with pure oxygen, it also accounts for zero NO_x formation and near-zero emissions overall. To this end, this study aims to examine the overall environmental performance of H₂-powered motorised equipment compared to conventional fossil fuel-powered equipment through Life Cycle Assessment. The assessment was conducted using the commercial software Sphera LCA for Experts, following the conventionally used framework established by ISO 14040:2006 and 14044:2006/A1:2018 and the International Life Cycle Data Handbook, consisting of (1) the goal and scope definition, (2) the Life Cycle Inventory (LCI) preparation, (3) the Life Cycle Impact Assessment (LCIA) and (4) the interpretation of the results. The results will offer an overview to support decision-makers in the sector. Full article

Iron and alumina can be separated from bauxite residue and calcite self-hardened reduced pellets through simultaneous magnetic separation and alkali leaching. Bauxite residue and calcite self-hardened pellets were reduced non-isothermally by hydrogen gas to obtain metallic iron. Thereafter, the fine grounded reduced pellet powder was leached with a simultaneous magnetic stirrer, while two different leaching processes were applied. In a magnetic stirring alkali-leaching process, the simultaneous leaching and magnetic separation by Na₂CO₃ solution was carried out. In another process, the reduced pellets were leached into water with gradual magnetic separation followed by the addition of Na₂CO₃ solution. X-ray diffraction, scanning electron microscopy, X-ray fluorescence, and inductively coupled plasma mass spectroscopy were used to conduct phase analysis, microstructural analysis, compositional analysis, and elemental analysis of the leaching solutions, respectively. It was found that, there was an increase in iron in the magnetic fraction as compared to a nonmagnetic fraction in both the leaching processes; however, the iron recovery is more noticeable in the magnetic alkali leaching process. The recovery of alumina depends upon the amount of mayenite formation during reduction. The greater the amount of mayenite and the lower the amount of gehlenite, the greater the alumina recovery will be. The simultaneous alkali leaching and magnetic separation lead to greater unlocking of the reduced matrix and to greater iron and alumina recovery compared to magnetic water leaching followed by alkaline leaching. Full article

Mine optimisation and anticipation of ore behaviour in the mineral processing and separation circuits are major economic drivers for all mining operations. Recent methodological developments with the inception of geometallurgy across multiple commodities have highlighted the importance of mineralogy in addition to elemental grades. In the last few decades, many quantitative tools have been developed, mostly SEM-based such as QEMSCAN^®, and used to provide the quantitative mineralogical compositions of samples. Their main drawback is the time and cost associated with sample preparation, acquisition time, and data QA/QC. The combined XRF-XRD of the SOLSA (Sonic On-Line drilling and Sampling Analysis) analytical solution brings a new methodology able to produce quantitative mineralogical and geochemical data at a speed compatible with a production environment. Its range of applications covers the entire life of a mining operation, from the initial exploration stage to mineral processing control, as well as waste management and environmental monitoring. Full article

The successful commercialization of the results of research works, R&D projects and inventions, as well as the cooperation between research centres, industry and business, is becoming commonplace and crucial in regional development. Regardless of the scientific level of the research results, the utility of these results and the adopted business model for their implementation are the key factors determining the market success. Currently, the recognized skills and competencies of academic staff at Eastern and Southeastern European universities in the field of the implementation and commercialization of scientific research results do not seem sufficient. This article presents the methodology, development and results of the tailor-made Science to Business transfer program implemented within the TrainESEEv.2 ‘Training the trainers in East and Southeast Europe’ project, with a focus on the Raw Materials sector needs. Full article

The deficit of graduates working in the core raw materials sectors will significantly impact raw materials organizations in European RIS regions. The RIS Internship programme aims to improve professional opportunities for RIS raw materials students, familiarize the future young professionals with the work environment and real-life challenges, and trigger their intrinsic interest for the development of a future career in the sector. The overall objectives of the programme are to increase the students’ entrepreneurial and business skills, boost the employment of the RM graduates within the hosting organizations, and leverage the regional brain drain. Eligible students and organizations are coming from core raw materials professions: mining, geosciences and geotechnology, geosciences, material science, extractive waste management, and metallurgy and recycling, all belonging to the STEM area. The territorial coverage includes European RIS countries: Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, the Czech Republic, Estonia, Greece, Hungary, Italy (southern part) Latvia, Lithuania, Montenegro, North Macedonia, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Turkey, and Ukraine. The programme was implemented via the recorded pretraining webinars of students and supervisors, the development of an RIS Internship guide for successful RIS Internship implementation, and an on-line matchmaking platform, making it structured and sustainable with minimum future investment. Full article

Chromite ore occurs mainly in ophiolitic mineral complexes and within ultrabasic rocks. As a result, the mining and enrichment processes applied to this ore lead to the production of large amounts of ultrabasic rocks, considered to be a waste stream. These wastes are mainly various structures of olivine and serpentine (i.e., hydrous structures of olivine). The ultrabasic rocks may be considered a by-product of this process, following the framework of the circular economy, but the presence of serpentine degrades their quality. In this work, it was proven that the thermal treatment of ultrabasic rock samples may eliminate the serpentine content. Full article

Magnetite deposits represent important iron ore resources. Selective sorting of valuables from gangue and targeting of potential critical metals that can be recovered from waste streams must be implemented from the exploration and excavation steps onwards. Optical and scanning electron microscopy, electron microprobe analysis, dual-energy X-ray transmission, and computed tomography were applied to determine the mineralogy and classify the iron oxides of different iron ore types. These characteristics can be used for sorting at the exploration and extraction steps to reduce unvaluable materials at the loading and hauling steps, which contribute about 50% of the greenhouse gas emissions of the iron ore mining and mineral processing sector. These data also contribute to fine-tuning mineral processing parameters. Full article

The steel manufacturing industry is one of the most concentrated anthropogenic carbon-emitting point sources that is still expected to increase further each year. Moreover, steel slags are also generated at a rate of 10–20% of the total crude steel production. The possibility to valorize both the flue gases and steel slags through mineral carbonation has garnered the spotlight in recent research on waste valorization and sustainable steel production practices. Mineral carbonation of steel slags leads to the stable adsorption of carbon dioxide onto the surface of the steel slags. Nonetheless, it is essential to assess whether the environmental benefits resulting from the mineral carbonation process would outweigh the environmental burdens associated with the transformation and carbonation processes. To this end, this study aims to illustrate the potential environmentally friendly industrial waste valorization pathway by performing life cycle assessment (LCA) to obtain the environmental impacts of carbonated steel slags. The environmental impacts are calculated by the ReCiPe 2016 midpoint methodology. Furthermore, contribution analysis for the carbonated slag production is provided. This study also illustrates a comparison of steel slag carbonation with pure carbon and flue gases by means of scenario analysis. The results of this study should provide insights into the possibility of employing mineral carbonation on industrial wastes in the metallurgical sector as well as highlight the possible areas of improvement for prospective scale-ups. To this end, the results of this study could contribute to the improvement of the environmental sustainability of the steel manufacturing sector. Full article