Stone industry plays a significant role in the global economy. The 2015 production was placed in the order of 82.6 million tons with a percentage of the waste extraction and processing amount to over 70% of the gross quantity. Carbonate stones (such as marble, limestone and travertine) account for 58 % of the whole production of dimension stone, serving as primary materials for construction and ornamental uses since ancient times. Approximately 50% of waste is generated during mining operation and around 15% during processing. The disposal of marble powder, a very fine material produced by the marble industry, is one of today's global environmental problems affecting stone industry. Even if the ultra-fine calcareous particles contained in marble sludge have applications in most major industries, thanks to their chemical and physical characteristics, in most cases these materials are landfilled because of the difficulties in recovering, mainly related to local legislation and lack of appropriate protocols.
The need to reduce the use of non-renewable natural resources and, at the same time, to minimize the negative impacts on the environment, has led to an increasing interest in recovery and recycling, in line with the expressed EU policy in the Europe 2020 strategy to reduce Europe's efficiency and in the EU strategy for sustainable development. The Carrara marble basin is one of the most emblematic cases in the Italian stone industry, and it includes about one hundred quarries of colored and white marble, exploited from Roman times. Even if the new technologies have improved efficiency in quarrying and reduced the production of waste, around 50% of the extracted marbles in the Carrara basin still result in waste. Modern cutting technologies generate greater amount of finer materials and sawing residue, varying in size from sand to silt. Due to this very fine particle, it’s easy to see how this characteristic can cause problems with the stability of landfills, with consequent difficulties for their management. The aim of this research is to provide a comparison between different characteristics of marble fine waste in Carrara, both sludges deriving from quarry-cutting and stone processing, to demonstrate the feasibility of their recovery and utilization in different industrial application (i.e., mineral fillers, high value-CaCO3 products, building sector). The results obtained from analysis are promising and could lead to a possible reuse of the materials, in line with the circular economy approach. The reuse of marble waste can bring the double benefit of giving a new value to this by-product and, at the same time, partially eliminate the environmental problem caused by it. The combination of all these insights could lead to sustainable mining of the ornamental stones industry.

How to cite: Tazzini, A., Gambino, F., Casale, M., and Dino, G. A.: Circular economy in extractive industry: challenge and chance to recover fine particles produced in marble quarries exploitation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-652, https://doi.org/10.5194/egusphere-egu24-652, 2024.

Rare Earth Elements (REE) are considered to be highly "critical" by the European Commission because the concentration of global supply and their use in a wide range of emerging technologies (e.g. smart phones, electric cars and wind turbines) and this at a time of increasing geopolitical tensions. According to the European Commission’s assessment, the demand for rare earth elements is expected to increase more than fivefold by 2030. Today, Europe is dependent on imports of these minerals, where China completely dominates the market, a factor which increases the vulnerability of European industry. Alternative sources of REE in Europe, such as recovery of quarrying and processing waste, are being considered.

This research, part of an italian project NODES, wich has received funding (PNRR) from the EU, about circular economy and recovery of mineral waste, focuses on the possibility to recover REE from extractive waste. The investigated area cover Piedmont Region in northern Italy. Waste materials from gneisses and granites (ranging from blocks up to residual sludge) used as dimension stones were characterized for volume, chemistry, mineralogy, and texture.

Based on the first analyses carried out, the most interesting contexts are those related to gneisses in Luserna Stone and Verbano Cusio Ossola quarrying area and to quartzites of Monte Bracco quarrying area.

Thanks to a proper treatment activity (grinding, screening and magnetic separation), these materials, present in past extractive waste facilities and in extractive waste coming from exploitation and working activities, could be used to recovery of REE. After the first phase, connected to “waste” characterisation, the following activities will be linked to processing of the richest samples to exploit (at Laboratory level) REE, and to economic issues.

An additional step will include leaching extraction tests (always at laboratory scale) to identify the best and most sustainable technique to extract and separate REE from the sampled extractive waste.

Key words: Rare Earth Elements, Critical Raw Materials, Supply-chain, extractive waste, mining waste, leaching, magnetic separation.

How to cite: Casale, M., Zhao, X., Khelifi, F., Cavallo, A., Padoan, E., Yang, K., and Dino, G. A.: Alternative ways to supply Rare Earth Elements: extractive waste recovery., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-948, https://doi.org/10.5194/egusphere-egu24-948, 2024.

Rare earth elements and yttrium have attracted considerable attention in recent decade due to their crucial roles in modern technology, particularly in the production of electronics, magnets, and batteries. These elements are of particular importance for developed and developing countries, as they play a significant role in clean energy as well as their growth and development. The concentration, distribution, and modes of occurrence of rare earth elements and yttrium in coal from the Oligocene formation in the Makum coalfield were investigated in this study. The study found that the coal samples from the Makum coalfield have a low ash and high sulfur content. Furthermore, the study revealed that the total concentration of rare earth elements and yttrium in the coal samples ranged from 1.48 to 77.61 ppm, with an average of 27.49 ppm. Based on the analysis of the coal samples. Average concentration of rare earth elements and yttrium in the Makum coalfield, as observed in this study, is lower than the concentration found in world average coals. it was observed that the 60ft coal seam had a higher average LREE/HREE ratio compared to the 20ft and 8ft coal seams. This indicates variations in the distribution patterns of rare earth elements and yttrium within the different coal seams. Coals from this region show a positive europium anomaly and have a weak negative cerium anomaly, indicating a significant marine influence during their formation. The sequential leaching used in this study provided valuable insights into the modes of occurrence of rare earth elements and yttrium in the coal samples from the Makum coalfield. Having a comprehensive understanding of the proportions of rare earth elements and yttrium in different forms, such as organic, silicate-aluminate, acid soluble, ion-exchangeable, and water soluble, is crucial for the development of effective methods and technologies for the extraction of these critical elements from coal.

How to cite: Sharma, S., Das, D., Tiwari, P., and Mondal, R.: Rare earth elements and yttrium in Oligocene coals of Makum coalfield, Assam (North-east India), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7191, https://doi.org/10.5194/egusphere-egu24-7191, 2024.

Municipal Solid Waste Incineration (MSWI) plants are of great concern, generating solid by-products, namely Fly Ash (FA) and Bottom Ash (BA). These MSWI residues have received significant attention for environmental concerns and the recovery of valuable elements, minerals, and secondary raw materials. The potential recovery of elements in MSW are crucial for circular economy and environmental sustainability (Han et al, 2021; Funari et al, 2016). Therefore, available types of fly ashes samples, i.e., lime- and soda-doped fly ash from bag filters following electrostatic precipitation, and quenched BA samples were sampled during pre- (2013, 2020) and post-pandemic period (2021, 2022) from two grate-furnace MSWI plants, located in Ferrara (FE) and Forlì (FC) cities in Italy. The sample preparation and elemental analysis were performed at ALS Scandinavia laboratory as a part of an international research collaboration between University of Bologna, Luleå University of Technology, and ALS Scandinavia. In this study, we aimed to determine and compare the elemental composition in MSWI samples by Inductively Coupled Plasma-Sector Field Mass Spectrometry (ICP-SFMS) to assess metal abundance by enrichment factor and elemental flows using substance flow analysis and MSWI systems’ mass balance (Brunner and Rechemberg, 2004). Our results showed that recovery of valuable elements (Al, Fe, Si, Zn, and Cu) was high after strong digestion method for all the FA and BA samples. Overall, little variation in elemental composition of FA and BA in both selected periods (pre-pandemic vs post-pandemic) suggests a similar input flow of urban waste. Enrichment factors (EF) show enrichment of Zn, Cu, Al, Fe, Mg, Ca, Na, K, and potentially toxic elements like Pb, Cd in both FA and BA. The chondrite normalized REE patterns of FA and BA are relatively similar suggesting that the BA and FA feeding material are mostly geogenic materials, with possible anthropogenic fluctuation for Ce, Tb, and Yb. The upper continental crust (UCC) normalization patterns were consistent for most elements. In contrast, Ba, K, P, and La patterns vary, likely showing an anthropogenic signal. Mass balance assessment showed that the waste streams can host from low to high concentration of strategic elements as an alternative source of value in the circular economy.

References

• Funari, V., Bokhari, S.N.H., Vigliotti, L., Meisel, T. and Braga, R., 2016. The rare earth elements in municipal solid waste incinerators ash and promising tools for their prospecting. Journal of Hazardous materials, 301, pp.471-479.
• Han, S., Ju, T., Meng, Y., Du, Y., Xiang, H., Aihemaiti, A. and Jiang, J., 2021. Evaluation of various microwave-assisted acid digestion procedures for the determination of major and heavy metal elements in municipal solid waste incineration fly ash. Journal of Cleaner Production, 321, p.128922.
• Brunner, P.H., Rechberger, H., 2004. Methodology of MFA. In: Practical Handbook of Material Flow Analysis. Lewis Publishers, Boca Raton London New York Washington, D.C., pp. 34–166, ISBN: 1-5667-0604-1.

How to cite: Ghani, J., Rodiouchkina, K., Rodushkin, I., Dinelli, E., Funari, V., Aiglsperger, T., Alakangas, L., and Engström, E.: Recovery of Metals from Municipal Solid Waste Incineration Plants Wastes: A Comparative Case Study of Pre- and Post-Pandemic Periods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21695, https://doi.org/10.5194/egusphere-egu24-21695, 2024.

Within the FINEST project (https://finest-project.de/) we tackle the use and management of finest particulate anthropogenic material flows in a sustainable circular economy. Subproject 3 "FINEST Disperse Metals" has set itself the goal of safely mixing various fine and ultra-fine-grained material flows that accumulate as waste during various industrial processes and extracting metallic raw materials from them in a subsequent multi-stage pyrometallurgical process, as well as generating a safe slag that can be disposed of without monitoring.

The idea of mixing different fine-grained waste streams arose from the experience that the search for economically and ecologically sustainable forms of recycling for the individual types of waste often failed despite promising approaches. This is usually due to individual parameters of the chemical or phase composition. The mixing we are aiming for allows us to select the technological parameters much more freely and to react to the rapid changes that are typical of waste streams.

We will implement this concept using three different material streams:

• So-called shredder fines from plastics, car and WEEE recycling
• Metallurgical fly ash from non-ferrous metallurgy
• Quarry dust and dust from concrete recycling.

The experimental work is preceded by a comprehensive characterization of the material flows in terms of chemical and phase composition, general physical parameters such as particle size distribution, particle shapes and flowability as well as any potential hazards. Based on this, both the mixing behavior and the pyrometallurgical parameters are modeled.

We use quarry dust for two main purposes. Their main contribution is to act as slag formers in the pyrometallurgical processing of the mixtures in the plasma furnace. This should be combined with the lowest possible liquidus temperatures and viscosities of the slag system. We are currently using four different quarry dusts from active quarries in the Free State of Saxony for our investigations (1 granite, 2 granodiorites and 1 amphibolite) as well as material from the concrete recycling of an extensive demolition project in Dresden.

Optimized mixing ratios between the individual quarry dusts and various metallurgical flue dusts were determined as part of the modeling using FactSage^TM.  The behavior during mixing of the material flows was initially investigated theoretically using model materials. The mixing steps were visualized using X-ray computed tomography.

How to cite: Renno, A. D., Hossain, M. N., Baecke, A. M., Kabir, A., and Dirlich, S.: Quarry dust an essential component in the pyrometallurgical recovery of valuable materials from mixed fine-grained waste, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19639, https://doi.org/10.5194/egusphere-egu24-19639, 2024.

Laterite ore deposits in Brazil and other tropical countries harbor large amounts of nickel and cobalt resources, along with other critical raw materials. The conventional methods of recovering nickel and cobalt, such as pyrometallurgy or high-pressure acid leaching, entail high energy, reagent costs, and expensive equipment. To address this, the German-Brazilian project BioProLat aims to develop an integrated, low-energy, and environmentally friendly biohydrometallurgical process for metal recovery from Brazilian laterite ores.

The process involves leveraging acidophilic bacteria that use sulfur as an electron donor, coupling sulfur oxidation to the reduction of ferric iron, ultimately converting insoluble metal compounds into water-soluble forms. This generates sulfuric acid, creating the necessary acidic conditions to keep iron and other metals soluble. Laboratory-scale bioreactor experiments optimized parameters like pH, temperature, and a suitable bacterial consortium for bioleaching nickel and cobalt. Results from aerobic bioleaching of laterite with a consortium of Acidithiobacillus thiooxidans strains showed an extraction of 85% for both cobalt and nickel. Mineralogical and geochemical analyses were conducted to identify mineral phases, which are attacked by bioleaching, and estimate the portions of cobalt and nickel released by bioleaching of different mineral phases. The goal is to scale up the optimized process, converting untapped ores and limonite stockpiles into valuable resources and unlocking new raw material reserves by enhancing metal recovery from existing mines.

How to cite: Hetz, S. and Schippers, A.: Stirred-tank reactor bioleaching of nickel and cobalt from Brazilian laterite ores, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17463, https://doi.org/10.5194/egusphere-egu24-17463, 2024.

How to cite: Falabella, F., Pepe, A., Oštir, K., and Calò, F.: Use of Interferometric Synthetic Aperture Radar Techniques as a remote tool for Mineral Extraction Sites Monitoring , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16673, https://doi.org/10.5194/egusphere-egu24-16673, 2024.

The importance of rare earth elements (REEs) in high-tech industries and the growing demand for raw materials have spurred interest in exploring unconventional deposits. Sedimentary phosphorite deposits are among the most prospective, with REE extraction as a P by-product. However, these ores are highly diverse regarding ΣREE content, distribution, and nature of phosphatic materials. This study focuses on the Estonian phosphorites of the Baltic paleobasin, which constitute one of Europe's largest phosphate rock reserves and are characterised by phosphatic shell fragments deposited in nearshore settings.

Geochemical investigations were conducted on carbonate-cemented phosphorites from Toolse and Aseri deposits. The determination of REE distribution and uptake mechanisms within apatites and carbonates was addressed by LA-ICP-MS in situ imaging technique developed by Drost et al. (2018), which allows identification and discrimination of mineral phases by integrating semiquantitative compositional data through the stepwise elemental distribution. Diagenetic enrichment stages were assessed using the following pathfinder elements as pooling channels: Sr and U.

Shelly apatites have homogenous REE-distribution patterns, MREE-enriched up to 15-fold compared to the PAAS, with positive Y and Ce anomalies indicative of an early digenetic overprint traceable by the Sr distribution. The average REE content in studied apatite is 2149ppm. However, the extent of diagenetic overprint and enrichment varies locally. In Toolse, shells show lesser recrystallised textures, and the Sr- and U-depleted stages allow the tracing of pristine signals prior to deposition. In Aseri, U-sorting reveals a second, alteration-driven enrichment in which fragment edges present a ΣREE up to 7020ppm. This alteration stage is less pronounced in Toolse, where REE content reaches only 4150ppm. The distinction between Sr and U-driven enrichment is less evident due to the lower input of hydrogenic or lithogenic REE carriers. The carbonates from both localities were found to be REE depleted compared to PAAS.

Based on these observations, the compositions of the apatite species could be distinguished and modelled to characterise the deposit. The diagenetic enrichment of REE was mainly driven by the upwelling of nutrient-rich waters, Fe and Mn-(oxyhydr)oxide reductive desorption, and secondary phosphatisation and homogenisation of shells. Fluctuations of redox gradients and Fe-Mn cycles led to slight local REE variability. Developing euxinic conditions and lithogenic input endorsed a later alteration-driven uptake, resulting in highly REE-rich edges. Despite differences in enrichment level, the two deposits' REE distribution patterns are similar. Main REEs are Ce (33%), Y (21%), La (12%), Nd (16%) and Dy (3%), and are considered among the most critical elements. On average, U concentrations are 92ppm in Aseri and 31ppm in Toolse, and toxic elements (Cd, Zn, Th) are found in trace amounts.

The study introduces a combined technique based on LA-ICP-MS and empirical distribution function data analyses as a powerful, accurate, cost-effective tool for determining REE distributions. It allows visualisation at different scales, representative measurements and a first approach to semi-quantifying elements. The method could provide insights into factors that control genesis in low-grade sedimentary ores and determine their potential valorisation routes.

How to cite: Graul, S., Monchal, V., Rateau, R., Joosu, L., Moilanen, M., Ndiaye, M., and Hints, R.: LA-ICP-MS imaging technique application on Estonian sedimentary phosphorites: Revealing REE enrichment stages and advanced ore characterisation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7319, https://doi.org/10.5194/egusphere-egu24-7319, 2024.