Bauxite residues (BR) from the Bayer process to produce alumina are highly alkaline and saline, containing high-level toxic elements (such as vanadium (V)), which are soluble in water under the alkaline pH condition. Ecological engineering of the BR can significantly improve physicochemical, mineralogical, and biological conditions, leading to the productive growth of pioneer plants. However, it remains unknown the fate of vanadium in response to the eco-engineering-driven changes of mineralogy, geochemistry, and organic matter decomposition.

The primary distribution of V in the BR-technosols will be characterized in sequential extraction and fractionation. The results of sequential extraction over show that the main vanadium pools in BR-technosols are in the iron oxide and organic matter phases, which provoked an investigation into the controlling mechanisms and specific sorbents, through microstructural and spectroscopic analysis combined with multivariate analysis. The alkaline environment was found to be the main controlling factor leading to elevated bioavailable vanadium in the bauxite residue. Within the iron oxide phase, amorphous iron oxides are expected to play an important role in sorption and therefore the conversion of crystalline iron-bearing minerals to the amorphous phase during weathering will be a direction of concern during long-term rehabilitation. Organic matter under natural soil conditions is an important vanadium sorbent, and additional additions of organic matter did not observe a significant improvement in this study sample, but when combined with P additions, a significant reduction in pH occurred, as did water-soluble vanadium. More investigation needs to be stimulated in terms of the role of P in promoting the addition of organic matter.

The expected results will aid the risk assessment of the eco-engineered BR-technosols and necessary intervention to mitigate the identified risks of V pollution in seepage and surface runoff in the future. 

How to cite: Ren, C., Saha, N., Parry, D., and Huang, L.: Influence of exogenous organic matter and P synergies on the geochemical behavior of vanadium in the rehabilitation of bauxite residues, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-812, https://doi.org/10.5194/egusphere-egu22-812, 2022.

Sulfide-modified nanoscale zerovalent iron (S-nZVI) is attracting a lot of attention due to its ease of production and high reactivity with hexavalent chromium (Cr (VI)). However, until now, the most commonly used is the use of NaS2O4 sulfide nano zero valent iron. The study on the removal of hexavalent chromium from water by nanometer zero-valent iron with calcium sulfide is not comprehensive enough. Herein, the removal of high concentration of hexavalent chromium from wastewater by nanometer zero-valent iron with calcium sulfide and its structure were carefully investigated. Scanning electron microscopy (SEM) with EDS analysis demonstrated that sulfur was incorporated into the zero valent iron core and homogeneously distributed within the nanoparticles. S-nZVI had an optimal Cr (VI) removal capacity of 200mg/L, which was >100% higher than for pristine nZVI. Different molar ratio of polycalcium sulfide and zero-valent iron, initial zero-valent iron addition amount, initial pollutant concentration and initial pH value have different effects on the removal effect. While the S/Fe=0.2, 200mg/L initial Cr (VI) concentration, 2g/L S-nZVI additive amount, pH<5, have the optimum removal rate. Contrast to pristine nZVI, S-nZVI can efficiently sequester high concentration of hexavalent chromium from different contaminated groundwater matrices.

How to cite: Yu, J. and Li, Y.: Removal of High Concentration of Chromium Hexavalent Wastewater From Groundwater by S-NZVI, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1011, https://doi.org/10.5194/egusphere-egu22-1011, 2022.

The excess phosphate in water leads to eutrophication, and hence finding cost effective adsorbing material for removing phosphorus from water is of great significance. Meanwhile, Coal Gasification Coarse Slag (CGCS) as a general solid waste, poses a potential threat to the environment. To solve these problems, herein, a novel low cost and high-efficiency adsorbing material was synthesized from CGCS by a facile method. The (CGCS)/ZrOCl₂⋅8H₂O mass ratio of 5:4 (denoted as CGCS-Zr4) was selected from a series of adsorbents with different mass ratios for subsequent sorption researches. The performance for phosphorus removal and related adsorption mechanism were investigated. The results showed CGCS-Zr4 had good adsorption property within a broad pH range. The Langmuir isothermal model, the pseudo-second-order kinetic and intra-particle diffusion model described the experiment data well, indicating that 1) the reaction process was monolayer and chemical adsorption; 2) rate determining step were both boundary layer effect and intraparticle diffusion. The adsorption mechanism of phosphorus on CGCS-Zr3 could be mainly achieved by electrostatic attractions and coordination reactions, forming inner-sphere phosphate complexes. The experiment results suggest that using Coal Gasification Slag (CGS) for removing phosphate could be a promising method in the wastewater treatment and resource utilization of solid waste.

How to cite: Yang, B. and Li, Y.: A novel Zirconium-modified Coal Gasification Coarse Slag for phosphate adsorption, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1041, https://doi.org/10.5194/egusphere-egu22-1041, 2022.

In the framework of the H2020 ETN SULTAN (European Training Network for the Remediation and Reprocessing of Sulfidic Mining Waste Sites) project, the release of metal(loid)s from different building materials, in which mining waste (including mine tailings and waste rock) was used as a raw material, was investigated. The waste rock and mine tailings originated from an active Cu-Zn mine and were characterized by a high content of Cu, Zn, Pb, and As. Part of the waste rock was cleaned by flotation before use, while the mine tailings were used without pre-cleaning. 

Bricks, clinkers, cements, and inorganic polymers in which from 14 wt% up to 100 wt% of primary raw materials had been replaced by mine tailings or (cleaned) waste rock, were subjected to various leaching tests: (i) a single batch leaching test (EN 12457-2), (ii) the Toxicity Characteristic Leaching Procedure (TCLP), and (iii) a cascade leaching test (NEN 7349). The influence of the processing of the mine waste, the pH of the leachates, and the mineralogical composition of the building materials on the immobilisation of metal(loid)s were assessed.

Clinkers and cements were the most efficient building materials to immobilise all metal(loid)s, even when uncleaned waste materials were used as a raw material. For the inorganic polymer produced from uncleaned mine waste rock, the leaching of Zn, Pb, Cu, and As was a point of concern, promoted by the alkaline pH of this material. The bricks had a lower release of metal(loid)s  compared to the inorganic polymers, which also showed the importance of an efficient cleaning procedure before using the mine waste as a raw material.

How to cite: Cappuyns, V., Adrianto, L. R., and Helser, J.: Immobilisation of metal(loid)s in building materials made with mine waste, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1736, https://doi.org/10.5194/egusphere-egu22-1736, 2022.

In recent decades, the recovery of materials and energy from waste materials has received attention, with the aim of finding a sustainable solution to reduce the exploitation of natural resources and reduce the use of landfills, stimulating a growing interest in the reuse of waste. In recent years new digital technologies continuously require rare metals, the abundance of which in the earth's crust is limited, and, for this, they are classified with me as critical raw materials. The Green Deal requirements call for improvements in the treatments for the extraction of raw materials also, and above all, from the gangues and waste materials from mining activities. Quarrying and processing of granite, for example, produce large amounts of waste residues, that besides being a loss of resources, improper disposal of these wastes results in pollution of the soil, water and air around the dumpsites.

This work aims to investigate the magnetic properties of mineral constituents of Buddusò Granites (Northern Sardinia) through the use magnetic separator in conjunction with gravity pre-concentration steps, using a shaking table to concentrate the valuable minerals and eliminate the undesired gangue minerals. These can be preliminary treatments for the possible use of granite scraps from quarries in the granite quarrying district of Buddusò as secondary raw materials. The granite waste samples were initially crushed using a jaw crusher and subsequently sieved to retain the part of the material with a grain size between 0.850 mm and 0.125 mm at a laboratory scale. The material was subjected to a preliminary separation process using a shaking table and obtaining seven subsamples were obtained starting from the initial one. Gravity separation was carried out in this work to discard the light gangues and obtain heavy mineral concentrate. The concentration process using shaking table is controlled by a number of operating variables, such as feed rate, wash water, feed pulp density, deck slope, amplitude particle size range, and as well as particle shape and the shape of the deck, play an important part in table separations. The sub-samples obtained by gravimetric separation were first placed to dry in an oven at 105 ° C for 24 hours and then has been treated by magnetic separation, which has been carried out in this work to separate paramagnetic (weakly magnetic) materials from non-magnetic materials. Each subsample, after being quartered, was then subjected to magnetic separation using the Frantz instrument, to separate the magnetically susceptible minerals from the others. This operation was first performed at low magnetic field strength to separate minerals with lower susceptibility and subsequently performed at high magnetic field strength to separate minerals with higher susceptibility.

According to Raslan et al., 2021, the preliminary results obtained, it is clear that the combination of gravity pre-concentration, using a shaking table, combined with magnetic separation, using dry high-intensity magnetic separator, is able to successfully concentrate heavy, paramagnetic and diamagnetic minerals phases, all of them with high mining potential.

How to cite: Vaccaro, C., Aquilano, A., Telloli, C., and Marrocchino, E.: Gravity and Magnetic Separation for Recycling of Granite Scraps in the Buddusò Quarrying District (Northern Sardina, Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2020, https://doi.org/10.5194/egusphere-egu22-2020, 2022.

Raw materials and critical raw materials (e.g. REE, PGM) supply is a matter of concern and a global challenge to face in a sustainable way: they can be exploited from ore deposits and be recovered from landfills (both urban and industrial), extractive waste facilities, and/or from waste streams. In a modern perspective of circular economy, the rational exploitation of mineral resources is essential, as well as a recovery and valorization of extractive and processing waste. In this research we present preliminary results related to the recovery of Beola and Serizzo extractive and processing waste, two commercial varieties of gneiss (dimension stone), quarried in Piedmont (northern Italy) and exported worldwide. Both Beola and Serizzo are varieties of orthogneiss, the former being very foliated and suitable for splitting, the latter more massive and used as granite for flooring and cladding. The percentage of extractive waste from quarry sites represents about the 60% of the total exploited material: it is possible to estimate an amount of about 110,880 t/y. Another important waste, whose management is very challenging, is represented by residual sludge (EWC 010413): sludge production is estimated in about 17,700 t/y. A critical point is represented by the regulatory framework of waste materials, with a view to their possible recovery. The relatively monotonic mineralogical composition of the gneisses consists of quartz, feldspars (oligoclase and microcline), and fair amounts of micas (muscovite and biotite). Typical accessory minerals are allanite (an epidote variety rich in REE), chlorite, and zircon. If from a mineralogical point of view there is substantial equality between Beola and Serizzo, the main differences lie in grain size and texture (finer grain and mylonitic microstructure for Beola). In the same mining district also granites are extracted, whose waste, after a series of treatments to remove ferromagnetic minerals (mainly biotite), are successfully reused in the ceramic sector (quartz – feldspars mix). For these reasons, also Beola and Serizzo could also have similar applications, if they undergo suitable mineral processing.  After extensive sampling and a robust mineralogical (OM and XRD), chemical (XRF and ICP-MS) and mineral chemistry (SEM-EDS and WDS) database, we have a complete picture of the characteristics of the waste materials from the different quarries. The main criticalities for the recovery of quartz and feldspars are represented by the grain size (especially for Beola varieties) and the relative abundance of phyllosilicates, which is higher than for granites. However, some varieties lend themselves much more than others to possible recovery, both for reasons of grain size and for the lower amount of mica. All varieties of gneiss contain fair amounts of allanite: this is a potential ore mineral for REE. One of the most easily processed waste materials for allanite extraction and concentration is sawing sludge: with relatively simple separation processes it would be possible to concentrate the heavy fraction, which also includes monazite (another important REE ore mineral). The efficient recovery of quarrying waste could therefore contribute to both the industrial minerals (quartz and feldspars) and the ore minerals sectors (REE).

How to cite: Cavallo, A. and Dino, G. A.: Quartz, feldspars and REE from gneiss waste materials: an example from the VCO province (Piedmont, northern Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3156, https://doi.org/10.5194/egusphere-egu22-3156, 2022.

Historical disposal sites of red mud can be found all around Europe, most notably at Sardinia, in Hungary, or at many locations in East-Southeast Europe. Red mud contains dominantly iron, aluminum, and silicon oxides, with races of various metals and compounds that can still be reprocessed if appropriate methods are applied. Some of the promising methods include microorganisms, and in particular bacteria.

The main objective of the study was to determine whether prolonged bacterial activity changes the geochemistry of the red mud. The bacteria for the experiment were isolated through several selective steps from activated sludge of wastewater treatment plant and red mud from three different locations: Dobro Selo and Zvornik (Bosnia and Herzegovina), and Almásfüzitő (Hungary).

After successful isolation, the bacteria were applied to the homogenized red mud samples, with nutrient media and water added in different combinations and ratios. The experiment lasted for 6 months after the bacteria were first applied to the red mud samples. During this period, geochemical analyses of the red mud were carried out twice, after 4 weeks and after 24 weeks, while the analysis of bacterial survival and quantity in the red mud samples were carried after 4, 8, and 24 weeks. The goal of geochemical analyses was to determine whether the bacteria caused changes in the concentrations of the elements of interest in the red mud when used as cultivating substrate and whether the elements of interest became more available to the bacteria due to their growth and adaptation to the red mud.

Prior to geochemical analysis, subsamples were heated at 100°C for 60 minutes to induce bacteriolysis and filtered twice with MiliQ water (red band filter paper). The eluates were stored in plastic cuvettes and kept in a dark place at 4°C until analysis (HR-ICP-MS). The filter papers containing the treated red mud were dried, sealed, and stored for further geochemical analysis of total major and trace element concentrations by ICP-MS and mineralogical (XRPD) analyses. Detailed results of the geochemical and mineralogical analyses are pending.

This work has been supported by EIT Raw Materials project RIS-RESTORE, project number 19269.

How to cite: Fajković, H., Huljek, L., Vrkić, I., Ivanković, T., Fiket, Ž., Gotovac Atlagić, S., Sukur, S., and Tomašić, N.: Geochemical analysis of microbiologically treated red mud, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3996, https://doi.org/10.5194/egusphere-egu22-3996, 2022.

Raw materials are essential for the sustainable development of modern societies. Access to and cost-effectiveness of mineral raw materials are critical to the smooth functioning of the EU economy. The growing demand for raw materials raises increasing concerns about mineral resources. Feldspars along with quartz, the main components of granitoid rocks, are widely used in ceramic and glass industry. The need to meet the demands of the ceramic industry has stimulated research and development of new ceramic flows in granite complexes.

Italy is the world’s second-largest feldspar producer (22% of total) and the world biggest importer (22% of global world trades) (European Commission). Since the strong demand is rapidly depleting the proven reserves in EU Member States, the EU ceramics sector is increasingly dependent on feldspar imports from Turkey. Thus, it is necessary to find additional sources of feldspar or to further increase inter-continental transport. At present, Buddusò-Alà dei Sardi (Sardinia-Italy) is the most important granite production area in Italy. However, granite mining activities cause serious environmental problems. Feldspar production and trade generate large amounts of pollutant and greenhouse gas emissions, due either to the energy consumption of mining activities or the transport of the finished product from the exporting countries. The areas where quarries are active suffer from landscape degradation, due to incomplete compliance or non-compliance with quarry recovery plans, considering that opening new quarries is cheaper than moving large amounts of waste. Finally, granite mining accounts for huge amounts of soil consumption, as it requires large areas in which the quarry waste accumulates.

The LIFE REGS II project (LIFE19 ENV/IT/000373 LIFE REGS II) aims at demonstrating an innovative and economically-viable extraction technology to produce feldspars, of the same quality to those obtained from virgin raw material, using granite scraps. This will reduce demand for feldspar from environmentally-damaging granite mining operations as well as to minimize the soil consumption and to boost the awareness about the importance of recycling granite scraps.

To this respect, samples of the granite scraps accumulated in 18 landfills located in the Buddusò-Alà dei Sardi granite quarries have been analyzed for their mineral texture and composition. Modal variability of the main mineral constituents (quartz+plagioclase±potassium-feldspar+biotite/chlorite) allowed to distinguish three main groups characterized by different ratios of feldspars/mafic phases with the exception of samples from a specific landfill that display an increase in the plagioclase at the expense of potassium-feldspar+quartz along with an increase in epidote at the expense of biotite/chlorite.

Texturally potassium-feldspar occasionally occurs as microcline perthite while plagioclase is always affected by extensive alteration resulting in a variety of textural intergrowths of neoformed minerals. Such features are reflected in the inter/intra-crystalline compositional variations in terms of feldspar end-members and in the type of the alteration products. This provides the elements for a first estimate of the technological properties of felsdpars, allowing to recognize the material stored in the 18 landfills qualitatively better for commercial purpose, and to experimentally identify the most effective methods of physical treatments to enrich and extract feldspars useful for industrial uses.

How to cite: Conte, A. M., Guglietta, D., Perinelli, C., Marrocchino, E., and Soro, G.: Eco-sustainable solutions to transform quarry waste of granite rocks into resources for the ceramic and glass industry., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4187, https://doi.org/10.5194/egusphere-egu22-4187, 2022.

The diagnostic process on the cultural heritage by non-invasive multi techniques generates multiple volumes of different data sets. Such volumes can be applied to a whole range of problems from diagnostics of the building stone materials to their in-time monitoring for maintenance and conservation. The results of the diagnostic process in multimodal data sets can be rendered effective by comparing multiple volumes at the same time and over time since the safety of monumental structures requires periodic monitoring. As already shown in recent works that focused on the integration of heterogeneous data from complementary techniques, the use of a single technique is generally insufficient to obtain a reliable diagnostic process.

The multi-technique high resolution 3D models described in this paper was aimed to investigate the conservation state of a precious carbonate colonnade in the ancient church of Saints Lorenzo and Pancrazio, dating to about the second half of the thirteenth century and located in the old town of Cagliari (Italy). The diagnostics of the carbonate colonnade was made by 3D non-invasive multi-techniques, i.e. Terrestrial Laser Scanner (TLS), close range photogrammetry (CRP) and ultrasonic tomography supported by petrographic investigations. To obtain a natural colour texturized 3D model of the columns with calibrated scale and coordinates both the TLS and CRP techniques were applied. The geometrical anomaly and reflectivity maps derived from the data of the TLS-CRP survey show presence of some anomalies worthy of attention. The 3D reconstruction with previous techniques was the essential base for the planning and execution of the 3D ultrasonic tomography that played an important role in detecting internal defects and voids and flaws within the materials by analysing the propagation of ultrasonic waves.

The results of the non-invasive diagnostic techniques on the building carbonate materials of the ancient colonnade were supported by thin section and mercury intrusion porosimetry (MIP) analyses in order to study their porosity and other textural characteristics such as the grains-matrix or grains-cement relationships, the bioclasts packing, the pore network and other petrophysical parameters (i.e. permeability and tortuosity). Knowledge of these characteristics is key to understanding the different susceptibility of the building carbonate materials to degradation and recognizing any forms of degradation while providing fundamental support to the interpretation of the geophysical data.

Acknowledgements

This work was supported by Regione Autonoma della Sardegna (RAS) (Sardinian Autonomous Region), Regional Law 7th August 2007, no. 7, Promotion of scientific research and technological innovation in Sardinia (Italy), Resp. Sc. S. Fais. 

How to cite: Casula, G., Fais, S., Cuccuru, F., Bianchi, M. G., and Ligas, P.: Diagnostic process of an ancient colonnade using non-invasive volume visualization multi techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5091, https://doi.org/10.5194/egusphere-egu22-5091, 2022.

One of the primary environmental problems connected to the growth of cities is the proportional increase of solid waste production and the corresponding leachate generation in the final disposal sites. A research line on the definition of technical systems that facilitate the proper treatment of these leachates to minimize groundwater, surface water, air and soil pollution is currently being developed.

One of the leachate-treatment alternatives is installing biofilm anaerobic biological reactors, in which microorganisms take charge of degrading organic matter while minimizing the leachate pollutant load. Optimal conditions are sought to develop this technology in order to achieve the highest bioreactor efficiency. Variables such as pH, temperature, retention time and the support media where the biofilm will be formed must be considered, in addition to its design and the material use to make it.

Therefore, the support media is one of the most important factors in anaerobic biofilm reactors design, given its function of creating the surface where the microorganisms adhere to form the biofilm. A proper design of this packing facilitates having a greater surface area per unit volume, thus increasing contact with the microorganisms, which is expected to increase the removal rate. Taking this into account, this study analyzes the types of materials currently used for packaging, along with their efficiency in biofilm reactors for first-stage leachate treatment. The evaluation is made using a specific polymeric material composed of polyethylene and expanded polystyrene waste as support media for bioreactors

How to cite: Gómez, Z., Solano, J., Orjuela, D., Rodrigo, M., and Rodrigo, J.: Analysis of support media in packaged bioreactors for landfill leachate treatment systems , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5522, https://doi.org/10.5194/egusphere-egu22-5522, 2022.

           Underground hard coal mining occurred in Germany over several centuries in the Ruhrgebiet in Northrhine-Westphalia and ceased in 2018. Nineteen mine waters draining historic and (sub)recent mines were studied in respect to their hydrochemistry and selected stable isotopes (H, O, C, S) in order to identify prevailing processes that determine their chemical composition.

All mine waters show near neutral pH values. Electrical conductivity displays a wide range with values between 370 and 1690 μS/cm (average value of 700 μS/cm). Major ions are in decreasing importance: dissolved inorganic carbon, calcium, sulfate, magnesium, sodium and chloride.

Sulfate concentrations range from 27 to 363 mg/L, showing a positive correlation with electrical conductivity. Sulfate sulfur and oxygen isotopes display some variability between -4.9 and +20.4 ‰ (average value of +4.5 ‰) and between +0.7 and +12.7 ‰ (average value of +4.5 ‰), respectively. Most isotope values suggest that sulfate derived from pyrite oxidation and/or the oxidation of organo-sulfur compounds in the coal. In contrast, the very positive sulfur and oxygen isotopes could indicate dissolution of sulfate minerals.

Apart from sulfate, dissolved inorganic carbon (DIC) is a major ion with concentrations ranging from 60 to 600 mg/L (average value of 249 mg/L). The carbon isotopic composition of DIC is somewhat variable with values between -19.3 and -4.5 ‰. Samples center around an average value of -11,40 ‰, suggesting the dissolution of carbonate minerals through carbonic acid.

In summary hydrochemical and stable isotope data from these mine waters suggest water-rock interaction as the main compositional driver, specifically carbonate dissolution, pyrite oxidation and sulfate dissolution.

How to cite: Weisser, O. and Strauss, H.: The legacy of hard coal mining in Germany: hydrochemistry and stable isotopes of mine waters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5667, https://doi.org/10.5194/egusphere-egu22-5667, 2022.

Solid waste management produced in megacities is usually being transformed under a linear treatment scheme which considers the circular economy model guidelines (waste reduction, reuse and recycling). The comprehensive solid waste management plan (PGIRS 2020) proposed for the city of Bogotá (Colombia) implements this circular economy approach through different strategies, such as increasing the separation levels at the source, optimizing collection and recycling, including waste as raw materials in production processes and designing technological alternatives different from landfills for the use and treatment of solid waste. Under this new vision, the design of waste management systems must consider those environmental impacts generated throughout the life cycle of waste while integrating ways to address these impacts in comprehensive waste management plans. Furthermore, health and environmental impacts that will result from new forms of waste use or mismanagement must be considered, including the mitigation of climate change effects by diverting waste that would potentially go to a landfill. Therefore, the methodologies adopted to evaluate environmental impacts must be aligned with these new trends while being capable of providing the required and appropriate results for decision-making to achieve established goals.

This work shows the methodologies used to evaluate the environmental impacts generated by solid waste in Bogotá. These methodologies have generally been qualitative so far: checklists, double-entry matrices, indicators and problem trees. They have been selected based on the availability of information, ease of calculation and the physical and technical availability of infrastructures. While different phases of solid waste management may require different methodologies, progress must be made in using more precise methods to reduce uncertainty in the evaluation and become more effective decision-making tools. One of these tools is the Life Cycle Analysis methodology (LCA). LCA provides an opportunity to make progress in including the circular economy approach in the comprehensive solid waste management of the city of Bogotá.

How to cite: Becerra Quiroz, A. P., Solano Meza, J. K., Rodrigo Ilarri, J., and Rodrigo Clavero, M. E.: Analysis of methodologies to evaluate the environmental impacts of solid waste management in the city of Bogotá, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6229, https://doi.org/10.5194/egusphere-egu22-6229, 2022.

Metal ore mining and beneficiation led to the formation of mine waters and artificial effluents with high metal concentrations, which need cleaning to prevent vertical and lateral metal propagation in the environment. Metal precipitation in the form of hydroxides is the most common method of wastewater purification with high metal concentrations. Serpentines are common in the Earth’s crust and often are by-products of overburden and enclosing rocks. Unlimited reserves of serpentines have stimulated the search for new technology for processing these raw materials. Serpentine structure and properties allow the production of materials used in environmental management. Serpentines heat treatment increases the ability to neutralize acids and precipitate metals from water solutions. The ability of heat-activated serpentines to form a binder through water mixing allows producing granular material. It can be used as an alkaline reagent in a bulk filter to purify highly concentrated solutions with the possibility of separate precipitation of metals.

The influence of the type of serpentine mineral (antigorite, chrysotile, and lizardite) on the hydration of thermally activated materials and the formation of magnesium silicate binder was studied. The serpentine samples were studied using X-ray diffraction analysis, differential scanning calorimetry, and surface texture analysis. The hydration of heat-activated serpentines through their interaction with water vapor and the strength characteristics of the resulting binder agents were investigated. The results show an essential role of serpentine structure in destroying mineral crystal lattices during heat treatment. The lower the activation energy of dehydroxylation, the higher the transformation of serpentines into the active metastable phase. It was found that thermo-antigorite does not sorb water, in contrast to thermally activated chrysotile and lizardite. The acid-neutralizing ability of latter minerals significantly differed with the higher values for thermo-chrysotile. The weight loss of hydrated samples at the temperature of 350-600℃ decreased in the same sequence – from chrysotile to antigorite. Therefore, this characteristic could be considered an indirect indicator of the total content and precursor of binder formed during the thermo-serpentine hydration.

In contrast, the strength of the samples based on heat-activated serpentines decreased in the row chrysotile–antigorite–lizardite. The structural features of chrysotile determined the greatest strength of serpentine binder samples compared with antigorite and lizardite. Lizardite acid-neutralizing ability (activity) was noticeably higher than antigorite, but its strength was lower due to the layered mineral structure and the presence of impurities reducing the strength of the resulting material.

Thus, the structural features of serpentines played a crucial role in the mineral hydration and, as a result, in selecting a material for producing a granular magnesium silicate reagent. Chrysotile is a promising mineral for obtaining granular materials, whereas lizardite is advisable to use in fractionated powders. Antigorite differs from the other two serpentines because it has a less acid-neutralizing ability and can be used for magnesia and silicate products.

The work was supported by the Russian Science Foundation project #21-77-10111.

How to cite: Ivanova, T., Slukovskaya, M., and Kremenetskaya, I.: Relationship between structure and hydration process in heat-activated serpentine-group minerals (antigorite, chrysotile, and lizardite), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6913, https://doi.org/10.5194/egusphere-egu22-6913, 2022.

Blast Furnace Slag (BFS) is a waste product generated during smelting of iron ore in a blast furnace. It is composed of, among other oxides, CaO and MgO due to which BFS is capable of generating alkalinity above pH 8 thus has a high neutralizing potential. This characteristic feature makes BFS a potential remediation agent for acid mine drainage (AMD) generated from abandoned mines. Passive treatment systems (PTS) of AMD generally make use of alkaline materials such as limestone to neutralize the acidity and to precipitate metals. Moreover, the use of BFS as an alkaline material in remediating AMD can be considered as a way of achieving industrial symbiosis and hence sustainability. However, researches conducted to investigate suitability of BFS in remediating highly acid (pH≤3) and metal rich AMDs are absent in the literature despite the promising properties of BFS. In addition, Rare Earth Elements (REE), which are considered as technology-critical elements, are present in higher concentrations in such AMDs than those found in natural water bodies. Therefore, in addition to the AMD remediation, it would be worth to investigate the effectiveness of BFS to also retain REE in PTS. This study aimed at investigating the efficiency of BFS in remediating highly acidic and metal rich AMD generated at the Iberian Pyrite Belt (IPB) and especially in retaining REE. Three AMD samples having different chemical properties were collected from the Tharsis mining area situated in the IPB. Various amounts of BFS were added to aliquots of AMD samples in  such a way to collect solids and solution per each pH unit until neutralization (from pH 3-7). Suspensions were then kept in an orbital shaker for a week to ensure proper contact between the added BFS and AMD solution. Afterwards, the suspensions were centrifuged at 4000 rcf for 5 min to separate the supernatants from the precipitated solids and BFS. The supernatants were then analyzed by ICP-MS and the removal efficiencies for Al, Fe, trace metals and REE were calculated. BFS showed high removal efficiency for Al (97.8±2.1%), Fe (98.8±1.2%), Zn (93.2±2.7%), Cu (99.7±0.3%), Mn (92.2±0.1%), As (99.8±0.2%), Cr (98.2±1.5%), Cd (99.6±0.7%) and REE (98±0.8%) at pH 7. This result shows that BFS is also suitable to be used as an alkaline agent in treating highly acidic and metal rich AMDs and in retaining REE. Precipitated solids during alkalinization of AMD with BFS will also be characterized by XRD, SEM/EDX and LA-ICP-MS to identify the nature of the precipitated solids and the association of REE with the mineral phases contained in the precipitated solids. The fate of toxic metals and REE during alkalinization will be modeled based on the results from solid and solution characterization It is thereby intended to reach a better understanding of the AMD remediation and REE retention mechanisms using BFS as alkaline material in passive AMD remediation.

Keywords: Blast furnace slag, Acid mine drainage remediation, Passive treatment systems, Rare Earth Elements

How to cite: Kotte Hewa, D. J., Durce, D., Salah, S., and Smolders, E.: Using blast furnace slag as an alkaline agent in remediating acid mine drainage from the Iberian Pyrite Belt and removal efficiencies for Rare Earth Elements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7488, https://doi.org/10.5194/egusphere-egu22-7488, 2022.

The mining and minerals sector faces a dilemma: the transition away from hydrocarbons and race to net-zero requires enormous quantities of mineral resources for low-carbon technologies. However, mining and processing can be hugely energy-intensive and sometimes environmentally harmful, thus there is a need for novel solutions in extraction and processing. Gold ore processing in particular often features cyanide, which is highly toxic and has a large carbon footprint [1], and the often low Au concentrations can result in relatively large volumes of waste rock.

In addition, gold deposits are often also enriched in other metals, and the Björkdal mine produces gold concentrates and tailings that also contain Te, Bi and W. Initial data indicates a high degree of liberation for bismuth-tellurides which is promising for extraction. Currently, there is little incentive and few options by which to process and extract these additional metals for Mandalay Resources, the mine operator [2]. Developing a way in which these metals could be recovered rather than sent to tailings would be ideal for meeting some of the demand for these metals, without opening any new mines.

Deep Eutectic Solvents (DES), developed at the University of Leicester, are a promising advancement for both gold and by-product extraction [3][4]. DES are eutectic mixtures of an organic salt and a hydrogen-bond donor, which are powerful solvents and liquid at room temperature. The components are cheap, readily available and environmentally-benign compounds, such as choline chloride (Vitamin B4) and urea, and can be recycled and reused. Previous work on DES has demonstrated rapid leaching of Au, Ag, Sb, Te and other metals [1], including success with dissolution of tellurides and bismuth tellurides [5].

This project aims to understand the flows of Te, Bi and W through the Björkdal processing plant, and mineralogically characterise tailings and concentrates. This will be used to test the feasibility and impacts of inserting DES leaching stages, and/or altering the processing procedure or reprocessing tailings, in order to maximise by-product recovery in an environmentally-friendly and low energy process.

References:

[1] Norgate T and Haque N (2012) J Clean Prod 29-30:53-63

[2] Jenkin G et al. (2019) 15th SGA Biennial Meeting 4:1512-1515

[3] Abbott A et al. (2004) J Am Chem Soc 126 (29):9142-9147

[4] Smith E et al. (2014) Chem Rev 224 (21):11060-11082

[5] Jenkin G et al. (2016) Min Eng 87:18-24

How to cite: Tritton, L., Jenkin, G., and Smith, D.: Recovery of Te, Bi and W from mine tailings and concentrates, using environmentally-benign Deep Eutectic Solvents at Björkdal Gold Mine, Sweden , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8697, https://doi.org/10.5194/egusphere-egu22-8697, 2022.

Mines have been (and still are) fundamental for the economic and social development of Countries: indeed, mining exploitation is aimed to meet the demand for natural resources to improve the life quality of population. Raw Materials (RM), including the Critical ones (CRM), are essential for the sustainable functioning of modern societies; they are used in several clean and low carbon technologies (batteries for electric vehicles, turbines for wind energy, solar panels, etc.), as well as employed in the electronic industry (capacitors, electronic devices, etc.). Furthermore, as for clean and low carbon technologies, the demand for CRM is dependent on which wind, solar, and battery technologies will become dominant in the marketplace. Indeed, the acceleration in deployment of the key low carbon technologies has real implications for the commodities market; thus, not only REE but also aluminum, copper, silver, iron, lead, and others all stand to potentially benefit from a strong shift to low carbon technologies. All literature examining material and metals implications for supplying clean technologies strongly agrees that building these technologies will result in considerably more material-intensive demand than would traditional fossil fuel mechanisms.

The availability of CRM/RM is increasingly under pressure, and the criticality of the processing infrastructure and the recovering of these elements from various resources, leads the EU to be dependent on their imports, often from non-EU countries, which have been always affected by: fluctuating policies of the market, potential conflicts in the areas interested by their exploitation, higher environmental impacts connected to their exploitation, processing and waste management. China is the biggest producer of the 30 CRM for the EU; other countries have dominant supplies of specific CRM, such as USA (Beryllium), Brazil (Niobium), Chile (Lithium), South Africa (Iridium, Platinum, Rhodium, Ruthenium), Kazakhstan (Phosphorous), Guinea (Bauxite), DRC (Cobalt).

There is still a high potential for RM/CRM available in Europe, but their exploration and extraction have faced a strong competition due to highly regulated environmental protection and different land uses. Several studies show that in many regions massive amounts of strategically important materials, such as metals, have been accumulated in landfills and extractive waste facilities. EU legislation aims to reduce the amount of wastes disposed in waste facilities and landfills and to foster the recovery and recycling of waste. The objective set by the measures of Circular Economy packages is not to allow any more landfills by 2050. Contemporary, EU policies intend to boost the domestic exploitation, which need to be faced in a sustainable way (also applying new financial instruments for companies, such as the “Sustainable Finance”). Thus, wastes (including extractive waste) have to be intended as resources and landfills (including extractive waste facilities) have to be considered as “raw material reserve” to be exploited. To face the challenges connected to sustainable RM/CRM supply, an interdisciplinary approach and a wider knowledge about waste characteristics, volumes, localization, suggested processing activities, main impacts on environment and human health are needed.

How to cite: Dino, G. A. and Cavallo, A.: Sustainable Raw Material supply: towards a more “domestic” approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8747, https://doi.org/10.5194/egusphere-egu22-8747, 2022.

In the last decades, the demand for raw materials, such as Heavy Metals (HM) and Rare Earth Elements (REE) is constantly grown due to the increasing demand from the new technologies. In particular, the REEs are mainly concentrated in apatite and zircon, largely present in pre-Paleozoic and Paleozoic cratonic rocks. Although many countries, such as Brazil, China and Iran have important deposits of HM and REE, they may only partially satisfy the increasing technology market demand. At present, extraction possibility is decreasing, and it is important to find new exploitable zones. For these reasons, mineral industries prefer to invest in exploration licenses before the mining activity.

Mozambique has a large and diverse mineral resource potential and is one of the most important exporting nations of raw materials.  Between 2009-2017 ENEA (National Agency for New Technology, Energy and Sustainable Economic Development) in collaboration with the University of Ferrara carried out explorative research to verify the presence of raw strategic materials in the Republic of Mozambique.

This research aims to investigate the sediments from the placer deposits of the Zambezi River in order to elaborate on the basis of analytical data an environmental friend extractive plan for mining activities that take into account also the environment and its preservation. The placer deposits are due to the mechanical agent, like marine, aeolian or lacustrine where minerals with high density and hardness, such as HM, are in high concentration, together with more than one economic mineral. The alluvial plain of the Zambesi River is characterized by the presence of sands, which contain heavy minerals in a percentage comprised of between 10-30%. A wide number of geochemical and mineralogical analyses (Diffractometry, XRF and ICP-MS) has been performed on samples, taken along 200 km of the river course. These data show a good presence of precious elements (Au, Ag, Pt, Pd, Os and Rh), a strong presence of minerals containing Fe and Ti, Zr, Hf and subordinately Ta, Ni and others. Moreover, Rare Earth Elements are present, in particular, is evident a good presence of Sc and Y from an economical point of view.

How to cite: Vaccaro, C., Zarlenga, F., and Marrocchino, E.: Research on the heavy sands of the floodplain of the River Zambezi (Republic of Mozambique). Mining potential and economic evaluation., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10374, https://doi.org/10.5194/egusphere-egu22-10374, 2022.

Granitoids are among the most common rock types used in construction. Along with their typical dominant mineralogical composition and rock microfabric, these rocks contain numerous minor/accessory phases and microfabric features that can be attributed to post-solidification development associated with e.g. hydrothermal alteration (HA). HA can be manifested both by microcracking, and by discrete changes in mineralogical composition – e.g., alteration of more basic cores of plagioclases, recrystallization of quartz aggregates, and/or by formation of clay mineral fillings of microcracks. Additional changes can occur due to various decay processes, and interactions with other construction materials (such as mortars) and/or conservation agents. Current study aims to show how these changes can influence physical and mechanical properties specifically when considering granitic natural stone used in important load-bearing infrastructural structures such as bridges. This issue can be of great importance for structures where individual stone elements were re-used from older ones or for those structures which require current repair.

How to cite: Prikryl, R., Racek, M., Natherova, V., Rimnacova, D., Prikrylova, J., and Kucharova, A.: Post-solidification features in granite natural stone and implication for its possible use and re-use in construction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11775, https://doi.org/10.5194/egusphere-egu22-11775, 2022.

As is now widely known, any industrial activity produces wastes. These materials, more and more often, represent a logistic and environmental problem since they require regulations and treatments for disposal/storage that inevitably affect the general costs of the final product.

Wastes from stone materials processing, in short, retain all the mineralogical and compositional characteristics of the original materials even if, in some way, may be contaminated by the processing itself, or by wearing and tearing of industrial tools.

This research presents preliminary results from testing prototypes of construction adhesives made up recycling 1) a quartzite (India) stone waste mixed with 2) sand (also from India) as fine aggregates in mix design of the adhesives.

First, both wastes were characterized by physical, chemical and mineralogical points of view.

Particle size distribution along with X-ray Diffractometry, X-ray fluorescence and Scanning Electron Microscopy were carried out to acquire precise physical, mineralogical, and chemical information on wastes.

Experimental research started by mix designing different recipes considering a reference adhesive and a waste containing ones. Fresh doughs, as reported in European standard EN12004-2:2017, were cured for 28 days and used to stick on a concrete support three types of tiles with different grip: i) a polished metal plate, ii) a ceramic tile and a iii) natural stone slab. For each type a statistical valid number of sticked samples was tested.

After curing time, adhesive capabilities were tested by the Pull Off - Adhesion Test, as reported in European standard EN12004-2:2017, with very promising results, comparable to those obtained by normally marketed adhesives.

Further mix design additions useful for improving adhesive capabilities are currently under development.

Experimental procedures and results carried out in this research by using wastes from India can be safely extended to materials of different origins, proposing itself as an alternative method to storage for the reuse of these kind of wastes.

How to cite: Graziano, S. F., Marone, P., Trinchillo, A., and Cappelletti, P.: Stone materials processing waste used as secondary raw material for construction adhesives: preliminary results., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12274, https://doi.org/10.5194/egusphere-egu22-12274, 2022.

A particular use of quarry waste is presented in this study. The aggregate quarries produce high amounts of quarry waste, especially dust, that has been considered for many years as ’no need materials. One possible use of this dust is as aggregate in renders. Four Hungarian basaltic quarries provides a high amount of dust: Uzsa, Recsk, Egerbakta and Vidornyaszőlős. 15% of the mass waste of dust from these quarries were added to the renders. Both standard size (quarry fresh) and nano-grinded dust were tested. Test specimens were made from the dust added render, and physical properties were tested 28 days after casting. Bending strength tests, uniaxial compressive strength tests were made to assess the mechanical properties of the renders. Carbonate formation, porosity and pore-size distribution were also analyzed to obtain valuable information on the binding and textural characteristics. Reference samples without basalt dust were also cast, and the test results were compared in order to assess the performance of basalt dust containing renders. The basalt dust and nano dust containing samples have lower bending strength than the reference ones, while the uniaxial compéressivbe strength increased when basalt dust was added. Nano dust containing samples show an increased porosity but a decrease in mean pore diameters. Our results show that adding basalt dust to renders could be a useful solution in the reduction of quarry waste and the obtained render has fairly good mechanical properties.

How to cite: Török, Á. and Kósa, Z.: Use of basaltic quarry waste in renders, examples from Hungary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12973, https://doi.org/10.5194/egusphere-egu22-12973, 2022.