Tailoring the FeO/SiO2 ratio in electric arc furnace slags to minimize the leaching of vanadium and chromium

Based on recently published research on leaching control mechanisms in electric arc furnace (EAF) slags, it is assumed that a FeO/SiO2 ratio of around one leads to low leached V and Cr concentrations. This ratio influences the mineral phase composition of the slag toward higher amounts of spinel and a lower solubility of calcium silicate phases by suppressing the formation of magnesiowuestite and highly soluble calcium silicate phases. To evaluate this hypothesis, laboratory and scaled up tests in an EAF pilot plant were performed on slag samples characterized by elevated V and Cr leaching and a high FeO/SiO2 ratio. Prior to the melting experiments, the optimum FeO/SiO2 ratio was calculated via FactSageTM. In the melting experiments, the ratio was adjusted by adding quartz sand, which also decreased the basicity (CaO/SiO2) of the slag. As a reference, remelting experiments without quartz sand addition were conducted and additionally, the influence of the cooling rate of the slag was examined. The remelted (without quartz sand) and the remelted modified slags (with quartz sand) were analyzed chemically and mineralogically and the leaching behavior was investigated. The modification of the slags yielded a minimized release of V and Cr, supporting the hypothesis that the FeO/SiO2 ratio influences the mineralogy and the leaching behavior

Investigation of possible leaching control mechanisms for chromium and vanadium in electric arc furnace (EAF) slags using combined experimental and modeling approaches

In this study, possible leaching control mechanisms for Cr and V in electric arc furnace slags were investigated by using a multi-methodological approach. Aside from chemical and mineralogical bulk analyses, special emphasis was given to surface investigations of the slags prior to and after leaching. In addition, pH dependence leaching tests were performed and the obtained data were evaluated with hydrogeochemical models. Investigations revealed that Cr and V are mainly bound in spinel and wuestite as well as minor amounts of olivine. Spinel and wuestite do not dissolve during water leaching for 48 h, whereas, depending on the composition of olivine, this phase either dissolves and releases V and Cr congruently, or does not dissolve but may hydrate. Melilite may also hydrate, but neither V nor Cr were detected in this phase. It appears that leached V is subsequently adsorbed onto these newly hydrated phases. The combination of the applied methods further showed that the abundance of calcium silicates, spinel, and wuestite is influenced by the FeO/SiO2 and CaO/SiO2 ratio in the slag. Therefore, it is assumed that the leaching of V and Cr can be minimized by changing these ratios to favor the formation of Fe bearing calcium silicate and spinel instead of wuestite

Probing magnetic ordering in air stable iron-rich van der Waals minerals

In the rapidly expanding field of two-dimensional materials, magnetic monolayers show great promise for the future applications in nanoelectronics, data storage, and sensing. The research in intrinsically magnetic two-dimensional materials mainly focuses on synthetic iodide and telluride based compounds, which inherently suffer from the lack of ambient stability. So far, naturally occurring layered magnetic materials have been vastly overlooked. These minerals offer a unique opportunity to explore air-stable complex layered systems with high concentration of local moment bearing ions. We demonstrate magnetic ordering in iron-rich two-dimensional phyllosilicates, focusing on mineral species of minnesotaite, annite, and biotite. These are naturally occurring van der Waals magnetic materials which integrate local moment baring ions of iron via magnesium/aluminium substitution in their octahedral sites. Due to self-inherent capping by silicate/aluminate tetrahedral groups, ultra-thin layers are air-stable. Chemical characterization, quantitative elemental analysis, and iron oxidation states were determined via Raman spectroscopy, wavelength disperse X-ray spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Superconducting quantum interference device magnetometry measurements were performed to examine the magnetic ordering. These layered materials exhibit paramagnetic or superparamagnetic characteristics at room temperature. At low temperature ferrimagnetic or antiferromagnetic ordering occurs, with the critical ordering temperature of 38.7 K for minnesotaite, 36.1 K for annite, and 4.9 K for biotite. In-field magnetic force microscopy on iron bearing phyllosilicates confirmed the paramagnetic response at room temperature, present down to monolayers.Comment: 19 pages, 6 figure

Spurenelementanalysen (LA-ICP-MS) von Scheelit aus der Wolframlagerstätte Felbertal

Based on economic importance and potential supply risk tungsten is considered as a critical raw material by the EU as about 80 % of the global tungsten supply comes from China. Within the EU the Felbertal scheelite deposit in Austria is one of the few producing tungsten mines. Vein-stockwork scheelite mineralization in this area was formed at ~340 Ma during the Variscan Orogeny, with subsequent metamorphic overprint and remobilization. Thus, several generations of scheelite can be distinguished. REE analyses (LA-ICP-MS) of these scheelite generations demonstrate that primary magmatic-hydrothermal (Scheelite type 1 and 2) and metamorphic scheelite (Scheelite type 3) have different chemical signatures. Extensive greenfield exploration during the 1980s led to the discovery of many other scheelite occurrences in the Eastern Alps. Since then, tungsten mineralization is known from different parts of the Austroalpine Unit and the Penninic/Subpenninic Nappe System. Mineralization style includes strata-bound mineralization, for example in metabasites (Felbertal), metacarbonates partly with magnesite (Tux-Lanersbach, Mallnock) and calc-silicate rocks (Messelingscharte, Lienzer Schlossberg), orogenic Au-W veins (Schellgaden) and scheelite-bearing metamorphic veins (Mühlbach/Neukirchen). The “W Alps” project (W stands for the chemical symbol of tungsten) aims to develop assessment criteria for the evaluation of regional tungsten potentials in Austria. In order to understand the context in the current geological-tectonic concept for the Eastern Alps the project includes field-based studies of tungsten-bearing geological units.Wolfram stellt für die Industrie einen gefragten Rohstoff mit großer wirtschaftlicher und strategischer Bedeutung dar. Allerdings bedingt die starke Abhängigkeit des europäischen Rohstoffmarkts vom größten primären Wolframproduzenten China (>80 %) ein erhöhtes Versorgungsrisiko, weshalb Wolfram in der aktuellen Liste der kritischen Rohstoffe für die EU 2020 aufscheint. Eine der wenigen aktiven Wolframminen in der EU ist die Scheelitlagerstätte Felbertal in Österreich. Die dort abgebaute gang- und stockwerkartige Vererzung wurde vor ca. 340 Ma während der variszischen Orogenese gebildet. Die anschließende metamorphe Überprägung sowie teilweise Remobilisierung der Vererzung führte zur Bildung mehrerer Scheelitgenerationen. Analysen (LA-ICP-MS) der Verteilung von SEE in diesen Generationen zeigen, dass sich primär magmatisch-hydrothermal gebildeter Scheelit (Scheelittyp 1 und 2) vom metamorphen Scheelit (Scheelittyp 3) aufgrund der chemischen Signatur unterscheiden lässt. Intensive Explorationstätigkeiten während der 1980er Jahre führten zur Entdeckung zahlreicher Scheelitvorkommen in den Ostalpen. Wolframvererzungen sind aus unterschiedlichen geologischen Einheiten des Oberostalpins, Penninikums und Subpenninikums bekannt. Die Mineralisationsstile umfassen schichtgebundene Vererzungen in Metabasiten (Felbertal), Metakarbonaten z. T. mit Magnesit (Tux-Lanersbach, Mallnock) und Kalksilikatgesteinen (Messelingscharte, Lienzer Schlossberg), orogene Au-W-Gänge (Schellgaden), metamorphogene Gang- und Kluftvererzungen (Mühlbach/Neukirchen). Das Projekt „W Alps“ (W steht für das chemische Symbol von Wolfram) beschäftigt sich mit der Entwicklung von Bewertungskriterien für die Evaluierung regionaler Wolframpotenziale in Österreich. Dabei dienen Geländeuntersuchungen von Wolframvorkommen in unterschiedlichen geologischen Einheiten dazu, den Kontext im aktuellen geologisch-tektonischen Konzept der Ostalpen besser zu verstehen.Trace element analyses of scheelite samples from the "Eastern Ore Zone" (open pit, level 2014) and "Western Ore Zone" (underground mine, level 1152) of the Felbertal deposit were done by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in 2003 and 2006 at the Department of Earth Sciences, University of Gothenburg, Sweden. A CETAC LSX-200 laser ablation system with a Nd-YAG laser (wavelength 213 nm) was used. The laser fluence was 4 mJ cm-2 at 4 Hz for a spot size of 100 μm. Analyses were collected in spot mode with spot sizes of 100 μm and 50 μm, respectively. Argon was used as carrier gas. Masses were analyzed with a quadrupole Agilent 7500a ICP mass spectrometer. NIST610 was used as primary reference material. All measurements on reference materials and unknowns were normalized to Ca, which was used as internal standard. Concentrations of Ca in scheelite were determined by routine WDX-electron probe microanalysis prior to LA-ICP-MS analyses from the same spots later analyzed by LA-ICP-MS. In the concentration data, the prefix “<” indicates the level of detection for each element, which may vary in the subsequent individual analyses. For more information see ZDGG publication (www.schweizerbart.de/journals/zdgg): Altenberger, F., Raith, J. G., Weilbold, J., Auer, C., Knoll, T., Paulick, H., Schedl, A., Aupers, K., Schmidt, S., and Neinavaie, H., 2021, Casting new light on tungsten deposits in the Eastern Alps: Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, v. 172, p. 63-72. https://doi.org/10.1127/zdgg/2021/0262Die Analysen von Spurenelementen in Scheelitproben aus dem "Ostfeld" (Tagbau, Etage 2014) und "Westfeld" (Untertagebau, Sohle 1152) der Lagerstätte Felbertal wurden 2003 und 2006 mittels Laserablation-induktiv gekoppelter Plasma-Massenspektrometrie (LA-ICP-MS) am Department of Earth Sciences der University of Gothenburg (Sweden) durchgeführt. Dazu wurde ein CETAC LSX-200 Laserablationssystem mit einem Nd-YAG Laser (Wellenlänge 213 nm) verwendet. Die Laserfluenz betrug 4 mJ cm-2 bei 4 Hz für eine Spotgröße von 100 μm. Die einzelnen Spotanalysen wurden mit einem Durchmesser von 100 bzw. 50 µm festgelegt. Als Trägergas wurde Argon verwendet. Die Massen wurden mit einem Quadrupol-Massenspektrometer Agilent 7500a ICP analysiert. Als primäres Referenzmaterial diente ein NIST610. Alle Messungen an Referenz- und Probenmaterial wurden auf Ca (interner Standard) normalisiert. Die Konzentrationen von Ca in Scheelit wurden durch routinemäßige WDS-Mikrosondenanalysen vor den LA-ICP-MS-Analysen an denselben Stellen bestimmt. In den Konzentrationsdaten gibt das Präfix „<“ die Nachweisgrenze für jedes Element an, die in den aufeinanderfolgenden Einzelanalysen variieren kann. Mehr Informationen in der ZDGG Publikation (www.schweizerbart.de/journals/zdgg): Altenberger, F., Raith, J. G., Weilbold, J., Auer, C., Knoll, T., Paulick, H., Schedl, A., Aupers, K., Schmidt, S., and Neinavaie, H., 2021, Casting new light on tungsten deposits in the Eastern Alps: Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, v. 172, p. 63-72. https://doi.org/10.1127/zdgg/2021/0262These published data are part of the project "MRI W Alps" that aims to develop assessment criteria (e.g., trace elements) for the evaluation of regional tungsten potentials in Austria. The series comprises a consistent set of geochemical, mineralogical and geological data from different types of tungsten mineralization in the Eastern Alps and provides the basis for defining prospective regions for tungsten.Diese publizierten Daten sind Teil des Projekts "MRI W Alps", das darauf abzielt, Bewertungskriterien (z. B. Spurenelemente) für die Evaluierung regionaler Wolframpotenziale in Österreich zu entwickeln. Die Serie umfasst einen konsistenten Datensatz aus geochemischen, mineralogischen und geologischen Informationen von verschiedenen Wolframmineralisationen in den Ostalpen und bildet die Basis, um Regionen mit erhöhter Prospektivität für Wolfram zu definieren

Quarz und Cristobalit aus Allchar als Monitore fuer kosmogenes

Allchar, Sb-As-Tl- Au Lagerstätte, befindet sich in Süd-West Teil von Mazedonien an der Grenze mit Griechenland. Wir haben eine ausführliche Untersuchungen, mit verschiedenen komparativen und komplementären Methoden (wie OM, Rö- Beugung, SEM, SEM-EDX, EPMA, ICP – MS, AMS) an den Quarz und Cristobalit aus Allchar durchgeführt. Zwei verschieden Art der Proben wurde untersucht: einmal als erz- bzw. petrographische Schliefe und nach Mineralogische Separation und mineralogisch – chemische Extraktion, als sogen. feinpulverliche stöchiometrische Minerale

High-resolution sulfur isotope and trace element measurements of sphalerites from the Pb-Zn deposits of the Drau Range (Eastern Alps, Austria/Slovenia)

High-resolution (partly in-situ) sulfur isotope measurements on sulfides in 17 samples from 5 different Pb-Zn deposits of the Drau range have been carried out. High-resolution sulfur isotope investigations provide knowledge on small-scale variations in the sulfur isotopic composition of coexisting sulfides and can help to interpret the mineralization processes. The sulfur isotopic composition provides evidence for different sulfur reservoirs and fluids involved in the mineralization process. Small-scale isotope heterogeneities can be related to textural aspects and this enables to recognize different sulfur reservoirs, one providing bacteriogene reduced sulfur (BSR) and another one responsible for thermochemical reduced sulfur (TSR). Both reservoirs were involved into ore formation and were able to contribute reduced sulfur during the whole mineralization process. In addition to isotopic measurements, major, minor and trace element analyses by electron microprobe (EMP) have been carried out on sphalerites in order to investigate if any relation between sulfur isotopic and chemical composition exists