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Hydrogen is an alternative reductant to replace carbon for the production of metals. Reduction by hydrogen has advantages compared to carbothermic reduction, such as faster reaction rate and cleaner by-product (water vapor). This study investigated the application of hydrogen reduction for recycling and recovering cobalt and lithium from Li-ion battery cathode material (LiCoO2). The study consisted of thermodynamic simulations of the reactions and microstructure evolution analysis from experimental work to propose mechanisms of the reduction process. The thermodynamic assessment predicted that metallic Co could be generated from 400 °C and was stable up to 1200 °C, but strongly dependent on the molar amount of H2. The final experimental reduction products of lithium and cobalt were found to vary and consisted of Li2O, LiOH, Li2O2 and Co, CoO, Co3O4, respectively. The experimental work revealed that the overall reduction mechanism is uniquely characterized by the reduction temperature. The temperature range of 800 °C to 900 °C offered more benefit as Co could be generated as a larger mass indicating a more progressive reduction. The data and information obtained can help optimize the parameters in the recycling of Li-ion batteries.

The kinetics and mechanisms of carbothermic reduction of a complex Kalimantan weathered ilmenite (FeTiO3) using palm kernel biomass were investigated in the temperature range 1273–1473 K. The study included a combined thermodynamic assessment together with reduction experiments. Results were contrasted with data from similar experiments conducted using graphite as the reductant. Thermodynamic simulations showed that the major phases formed during reduction were pseudobrookite and metallic iron with reduction using biomass predicted to produce more metallic iron compared to the use of graphite in the same temperature range. Incomplete dissociation of ilmenite by biomass was noted at 1473 K and 30 min reaction time however increasing the reaction time to 180 min resulted in near complete ilmenite dissociation. The kinetic analysis indicated that the reduction process followed a diffusion-controlled mechanism. This was confirmed by a microstructural analysis that showed the reduced ilmenite grains had a three-layer structure. The microstructural analysis also revealed that pores and cracks present in the initial weathered ilmenite promoted metallic iron formation. The apparent activation energy for ilmenite reduction using biomass and graphite was determined to be 217.00 ± 0.06 kJ mol−1 and 239.44 ± 0.06 kJ mol−1, respectively. Based on the findings, a general micro-mechanism for the carbothermic reduction of weathered ilmenite was developed.

The lunar surface is extremely harsh and current mineral processing and metal extraction technologies are not adequately equipped to address this environment. In this paper we review the metals available for extraction and conditions at the lunar surface, and analyse the challenges associated with comminution, beneficiation, and metal extraction operations. The potential beneficial effects of the natural lunar conditions are also evaluated. This investigation concludes that process plant design on the lunar surface will favour lightweight, schematically simple flow sheets that enable automation, and that utilise the local environment wherever possible. The elimination of traditional comminution and beneficiation stages and their replacement with basic classification could be economically favourable. The most promising metal reduction pathways are identified as molten regolith electrolysis, and vacuum thermal dissociation, other processes with merit are hydrogen reduction, carbothermal reduction, and solid electrolysis. Finally, it is identified that a significant research effort in all areas of astrometallurgy will be required before industrial-sized extra-terrestrial mineral processing and metal extraction operations will be viable., 31 Pages, 5 Figures

Analogue sinter tablets were produced at temperatures between 1250°C and 1320°C, with a range of hold times and cooling rates. Platy silico-ferrite of calcium and aluminum (SFCA) morphology was identified in samples produced at 1250°C using reflected light microscopy; however, quantitative x-ray diffraction (XRD) identified the presence of the SFCA phase, with no SFCA-I detected. This proves that the platy SFCA morphology common in analysis by reflected light microscopy cannot be attributed to the SFCA-I mineral without further analysis. Micro-XRD and electron probe micro-analysis (EPMA) were carried out on an area of platy SFCA confirming this result. The sinter analogue tablets were reduced in a 30% CO, 70% N2 gas mixture at 900°C in a tube furnace thermo-gravimetric analyzer. The degree of reduction of the tablets in this study was found to be controlled by the porosity of the samples, rather than by the morphology or mineralogy of the bonding phase.

The effect of MgO on the stability, concentrations and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA and SFCA-I) iron ore sinter bonding phases during heating in synthetic mixtures was investigated using in situ x-ray diffraction. The novelty of this study is in the intricate detail in which the formation mechanisms of the SFCA-I and SFCA phases are characterized, and the observation of the effects of MgO addition on intermediate phases. For example, the significant mechanistic effect of increasing MgO content is the lack of additional SFCA formed after SFCA-I decomposition, with additional magnesioferrite spinel being formed instead. In MgO-free mixtures, the decomposition of SFCA-I typically results in a significant increase in SFCA concentration. Through the results of phase equilibria experiments, this study also provides evidence that the SFCA-I structure accommodates more Mg2+ than the SFCA structure, which is consistent with evidence that the SFCA-I structure contains a higher amount of Fe2+ than SFCA.

Dry processing options, involving the use of a circulating air classifier and thermal roasting (advanced microwave-assisted magnetizing roasting), followed by magnetic separation using an Induced R...

A carbothermic reduction of complex Kalimantan ilmenite (FeTiO3) with palm kernel shell biomass as a reducing agent using regular electric and simulated solar heating has been investigated. The results demonstrate that palm kernel shell biomass can be used as an alternative reductant for the carbothermic reduction. Incomplete ilmenite dissociation was observed at 1000°C and 1100°C for 60 min reaction time using an electric furnace. Complete ilmenite dissociation was attained at 1200°C using both electric and solar furnaces. The major phases formed upon reduction at 1000°C were TiO2 (rutile) and Fe(m). Pseudobrookite (Fe, Mg, Mn)(Ti2O5) was formed at 1100°C, and higher concentrations were observed at 1200°C for 60 min reaction time. Reduction at 1200°C using a solar furnace promoted pseudobrookite formation, and a unique streak morphology of Fe(m) was observed as opposed to a globular structure found in samples heated in an electric furnace. It is suggested that this may be due to localized overheating by solar radiation that promoted rapid local reduction.

Lime magnetite pellets (LMPs) containing CWF phase (CaFe3O5) provide potential feed materials for ironmaking. In this paper, the effects of typical impurity oxides inherent to magnetite ores such a...

The physical and mechanical properties of iron ore agglomerates are highly dependent on their chemical, mineralogical and microstructural properties. The effect of Al2O3, MgO and SiO2 on the phases...

Bangladesh’s heavy minerals deposits in river systems remain largely unexplored with past research restricted to beach placer deposits along the south-eastern coastline of the country. In this study, 64 samples were collected from stable sand bars from the northern Brahmaputra River. The average total heavy minerals (THM) from all sample sites was 10.73 wt%, with the THM concentrations generally highest at the outermost edges of the river and lowest within the mid-channel regions. There was no variation in THM content from north (upstream) to south (downstream). Valuable heavy minerals (VHMs) magnetite, ilmenite, garnet and zircon made up around 25–30 wt% of the THM content, with other heavy minerals including amphibole, pyroxene, kyanite, sillimanite, monazite, apatite and xenotime making up the remaining 70–75 wt%. A VHM distribution map showed that the upstream division of the studied area appeared to be the most prospective for valuable heavy minerals. A bench scale heavy mineral sands beneficiation flowsheet involving unit processes employing gravity, magnetic and electrostatic properties was designed and based on a detailed characterisation and phase analysis of the resulting fractions, it was determined that VHMs made up ~2 wt% of the material recovered. Of these, garnet and ilmenite made up the bulk of the VHMs at levels of 0.88 and 0.51 wt%, respectively, with recoveries of &gt, 83%. Characterisation of the concentrates showed that further refinement of the processing conditions is required to generate concentrates that are potentially suitable for commercial applications.

An alternative route of magnetite processing involving the formation of CWF (CaFe3O5/calcio-magnetite) phase in lime-magnetite pellets (LMPs) was proposed in the previous paper. This paper is focus...

The beneficiation of ferruginous rare earth bearing ores derived from lateritic deposits by conventional mineral dressing processes is usually difficult due to characteristics of these ores such as fine grain size, complex texture and similar physical characteristics between rare earth minerals and iron oxide gangue. The removal of iron oxides would offer significant advantages with respect to downstream rare earth mineral processing. The purpose of this study was to demonstrate at bench scale the feasibility of magnetically separating iron oxides from a ferruginous lateritic rare earth ore after the ore had been subjected to reduction roasting to convert feebly magnetic iron (III) oxides to magnetite. The effects of magnetic field strength and feed top size on the efficiency of low intensity magnetic separation (LIMS) was explored through rougher magnetic separation tests using a Davis tube tester and chemical and mineralogical analysis of the rougher magnetic concentrates and tails was performed. Magnetic separation was successful in removing iron (as magnetite) to the concentrate at a minimum field strength of 0.2 T; this was however non-selective, with significant amounts of rare earths reporting to the magnetic fraction. The rare earth enriched tails showed decreased grade and recovery and this was due to a number of factors including insufficient liberation, presence of iron oxide coatings on mineral surfaces and heteroflocculation. The findings of this study provided insight towards the potential optimisation and viability of the proposed process of magnetising roasting and low intensity magnetic separation as a means to beneficiate ferruginous lateritic rare earth ores.

Compared with processing high-TiO2 concentrates such as ilmenite ores, processing an anatase ore to achieve impurity levels acceptable for pigment production is more difficult because of the extensive number of accessory minerals present, the significant intergrowths between minerals and the fact that impurity elements may be distributed in several different minerals. In this paper, conditions applicable to processing anatase ores are reviewed with an aim of identifying conditions that may produce a suitable feedstock for processing to titania pigment by either the sulphate or chloride routes. Anatase ores containing 25–35 wt% TiO2 currently are processed using mineral dressing techniques of crushing and grinding, classification, magnetic separation and flotation to produce a concentrate with around 65 wt% TiO2. This concentrate is then typically upgraded to over 90 wt% TiO2 using combinations of heating and leaching treatments, often with the addition of a fluxing reagent to assist in impurity removal. The suitability of these products as a feedstock for the sulphate and chloride routes to pigment is discussed.

Detailed characterisation of a lateritic rare earth ore formed from the weathering of a primary carbonatite was carried out to determine the mode of occurrence and distribution of rare earths and gangue species in the ore. The ore was characterised by a number of techniques including chemical analysis, quantitative X-ray diffraction, screen analysis, QEMSCAN and SEM/EDX. The primary rare earth bearing mineral identified was monazite in its various forms; florencite the other rare earth mineral identified is of secondary importance. The main gangue species was goethite with lesser amounts of dolomite and apatite. As a result of the weathering process, the ore was enriched in rare earth oxides with the head grade being 7.65 wt%. Screen analysis of the crushed ore shows that it consists predominantly of fine and ultra-fine particles below 38 μm with the rare earths and iron distributing in the finer size fractions. Microstructural characterisation of the rare earth minerals in crushed ore showed that the rare earth minerals were of very fine grain size and occurred as polycrystalline aggregates and fine disseminations in gangue. Compositionally, monazite was cerium dominant and contained calcium and strontium as impurities whilst florencite was either cerium or lanthanum dominant and was enriched in strontium. The rare earth content in monazite was much higher relative to florencite, making it an important source of rare earths in the ore. Concentrate grades are likely to be impacted by the presence of structural impurities (Ca, Sr, Al) associated with monazite and florencite. In light of these findings, potential processing options such as magnetic separation and froth flotation for recovering rare earths from this ore are discussed which are also potentially applicable to the beneficiation of other ferruginous rare earth bearing ores of similar mineralogy.

Magnetite is relatively harder to reduce compared to hematite and present practise of magnetite processing involves its oxidation to hematite during pelletisation, followed by subsequent reduction in the blast furnace. In this paper, we establish the feasibility of forming a reducible CaFe3O5 (CWF) phase through the addition of lime to magnetite that can be directly charged to iron-making units. This new approach will potentially provide a better process route (in terms of CO2 emissions) for the production of iron. Thermodynamic assessment was carried out to understand the suitable range of temperature, composition and oxygen partial pressure for CWF stability. Experiments were carried out using laboratory grade chemicals and products were characterised using XRD, SEM and EDX. Reducibility of CWF phase was measured using scaled-down standardised tests and was found to be comparable to industrial sinters. Compressive strength of the CWF pellets was in the range of 14 to 35 MPa.

This paper critically reviews published research on silico-ferrite of calcium and aluminum (‘SFCA’) phases, the major bonding phases found in modern iron ore sinters. In particular, we focus on describing the different ‘SFCA’ phases formed in iron ore sinter and examining their phase chemistry, crystal structures, characteristic textures and microstructures, and formation conditions. Information for the two main bonding phases SFCA and SFCA-I are reviewed and, based on a critical analysis of the data, we suggest future research directions required to generate the information necessary to fully describe the properties of both phases.

Phase equilibria of CaO-Al2O3-SiO2-Na2O slags were studied by thermal equilibration and quenching. The primary phases of the quenched slags were identified, and their equilibrium compositions determined by electron probe microanalysis. Liquidus temperatures of the slags were bracketed within an uncertainty of ± 10–20°C. Anorthite (CaO·Al2O3·2SiO2), gehlenite (2CaO·Al2O3·SiO2), pseudowollastonite (CaO·SiO2), and larnite (2CaO·SiO2) were observed as primary phases. Progressive doping by Na2O substantially changed the slag liquidus temperature, shifting the primary phase from anorthite to pseudowollastonite and larnite, and gehlenite to larnite. The liquidus temperature decreased significantly with increasing Na2O in slags with CaO/SiO2 (C/S) ratios of 0.3 and 0.6, while the liquidus temperature increased for slags with a C/S ratio of 1.0. The solid solubility of Na2O in the phases was quantified. Finally, the relevance of the phase equilibria study of the CaO-Al2O3-SiO2-Na2O system was discussed with regard to the optimum design of smelting with a focus on value recovery from e-waste.

The recovery of valuable and critical metals from electronic wastes (e-waste) via the pyrometallurgical route has some challenges including high processing temperatures. Designing appropriate slag systems based on the major elemental components in e-waste could bring operational advantages by lowering the liquidus temperature. In this study, the quaternary slag system CaO–Al2O3–SiO2–Na2O was investigated to determine the liquidus temperature and phase equilibria of slags relevant to e-waste smelting. The slags were thermally equilibrated at different temperatures inside a vertical tube furnace followed by rapid quenching. The quenched slags were examined by SEM to observe the phase formed and the equilibrium compositions were determined using energy dispersive (ED) spectrometry. The liquidus temperature of the slags in the anorthite (CaO·Al2O3·2SiO2) phase field was significantly decreased with increasing levels of Na2O. The slag composition moved towards the pseudo wollastonite (CaO·SiO2) region upon the addition of Na2O.

Knowledge of the behavior of technologically enhanced naturally occurring radioactive materials derived through the decay of U and its daughter products, and their subsequent fractionation, mobilization and retention, is essential to develop effective mitigation strategies and long-term radiological risk prediction. In the present study, multiple state-of-the-art, spatially resolved micro-analytical characterization techniques were combined to systematically track the liberation and migration of radionuclides (RN) from U-bearing phases in an Olympic Dam Cu flotation concentrate following sulfuric-acid-leach processing. The results highlighted the progressive dissolution of U-bearing minerals (mainly uraninite) leading to the release, disequilibrium and ultimately upgrade of daughter RN from the parent U. This occurred in conjunction with primary Cu-Fe-sulfide minerals undergoing coupled-dissolution reprecipitation to the porous secondary Cu-mineral, covellite. The budget of RN remaining in the leached concentrate was split between RN still hosted in the original U-bearing minerals, and RN that were mobilized and subsequently sorbed/precipitated onto porous covellite and auxiliary gangue mineral phases (e.g. barite). Further grinding of the flotation concentrate prior to sulfuric-acid-leach led to dissolution of U-bearing minerals previously encapsulated within Cu-Fe-sulfide minerals, resulting in increased release and disequilibrium of daughter RN, and causing further RN upgrade. The various processes that affect RN (mobility, sorption, precipitation) and sulfide minerals (coupled-dissolution reprecipitation and associated porosity generation) occur continuously within the hydrometallurgical circuit, and their interplay controls the rapid and highly localized enrichment of RN. The innovative combination of tools developed here reveal the heterogeneous distribution and fractionation of the RN in the ores following hydrometallurgical treatment at nm to cm-scales in exquisite detail. This approach provides an effective blueprint for understanding of the mobility and retention of U and its daughter products in complex anthropogenic and natural processes in the mining and energy industries.

Alluvial mineral sands rank among the most complex subjects for mineral characterization due to the diverse range of minerals present in the sediments, which may collectively contain a daunting number of elements (>20) in major or minor concentrations (>1 wt%). To comprehensively characterize the phase abundance and chemistry of these complex mineral specimens, a method was developed using hyperspectral x-ray and cathodoluminescence mapping in an electron probe microanalyser (EPMA), coupled with automated cluster analysis and quantitative analysis of clustered x-ray spectra. This method proved successful in identifying and quantifying over 40 phases from mineral sand specimens, including unexpected phases with low modal abundance (4] for which 24 elements were analyzed, including 12 overlapped REEs. The mineral identification procedure was also capable of characterizing mineral groups that exhibit significant compositional variability due to the substitution of multiple elements, such as garnets (Mg, Ca, Fe, Mn, Cr), pyroxenes (Mg, Ca, Fe), and amphiboles (Na, Mg, Ca, Fe, Al).

In the present study, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray absorption near edge structure (XANES) spectroscopy, and Raman spectroscopy were used to investigate the effect of chloride ions on chalcopyrite bioleaching and chemical leaching at 25 °C. The leaching results show that the addition of chloride ions suppressed the dissolution of chalcopyrite in both chemical and bacterial leaching. In chemical leaching, the solution redox potential in the experiment without Cl− stayed in a range more suitable for chalcopyrite dissolution compared with experiments with Cl−. In bioleaching, the bacteria activity was suppressed by Cl− leading to low dissolution rates of Cu. Surface morphology and chemical speciation studies confirmed the formation of potassium jarosite on the surface of the chalcopyrite leach residues. In addition, S K-edge XANES indicated the formation of trace amount of elemental sulfur and covellite on the mineral surfaces.

A synthetic coffinite was hydrothermally prepared and characterized before conducting a series of acid sulfate leach tests under conditions of relevance to uranium extraction. The results were then compared with similar studies on synthetic versions of the related U4+ minerals uraninite (UO2) and brannerite (UTi2O6) to identify and differentiate the rate and U extraction among these important uranium minerals. Tests examining the influence of residence time on uranium dissolution from synthetic coffinite, uraninite and brannerite showed that under similar experimental conditions, complete dissolution of uranium from coffinite was obtained between 36 and 48 h. The activation energy for this reaction was calculated to be 38.4 kJ/mol. This represented a significantly slower rate of dissolution than that indicated for uraninite which dissolved in 3 h (Ea=15.2 kJ/mol). The synthetic brannerite was leached at a much slower rate than the coffinite and reached a maximum dissolution of ∼18% U in 144 h (Ea=42–84 kJ/mol). The clear differentiation in rates and U extraction among the three minerals is consistent with previous literatures which suggest that in terms of leachability, uraninite>coffinite>brannerite. It is expected that the presence of impurities in natural coffinites would further inhibit leachability.

Surface and borehole sampling along a ∼80 km section of the lower Tista river, northwestern Bangladesh, indicated that the river sands offer significant potential as a heavy mineral (HM) resource. ...

A novel approach for the removal of chrome-bearing spinel impurities (chromite) from weathered ilmenite concentrates has been proposed. This involves a two-stage process where in Stage 1 the spinel impurities are subjected to selective surface sulphidation followed by physicochemical separation in Stage 2. In this Part 1 paper, the applicability of the selective sulphidation of spinel impurities at 1100 °C was investigated for different ilmenite concentrates sourced from the Murray Basin region in south-eastern Australia and from Bangka Island Indonesia. The results demonstrated that the selective sulphidation of the impurities can be applied to the Murray Basin ilmenites. This was indicated by the formation of sulphide-rich rims on the spinel impurities. The chrome spinels from the Indonesian ilmenite, however, were not sulphidised. This was most likely due to the refractory nature of the spinels as they contain higher concentrations of Mg and Al. The current study also simulated an industrial Becher kiln process in a laboratory roller-bed-furnace. The results show that the selective sulphidation conditions can be achieved using char and sulphur sources. It was also observed from these experiments that Mn impurities are also sulphidised. The current study also identified and presented the range of high temperature and gaseous conditions (pO2 and pS2) that promote the selective sulphidation of Mg, Mn, Sn and Y impurities.

The factors influencing goethite to magnetite conversion during magnetizing roasting of an iron-rich rare earth ore using coal as the reductant were explored in the present paper. The effect of temperature, time and reductant addition on magnetite conversion; and the optimal conditions which resulted in complete conversion of goethite to magnetite were determined through the use of satmagan and quantitative X-ray diffraction. For this particular ore, optimal roasting conditions were determined to be a roasting temperature of 600–650 °C with the addition of 10–20 wt% coal in the mixture and a roasting time of 90 min. The mineralogical changes occurring during magnetizing roasting were also investigated using X-ray diffraction. Magnetite formation was found to proceed by the reduction of hematite formed from the dehydroxylation of goethite. X-ray diffraction showed that further reaction of magnetite to form wustite and fayalite had taken place under highly reducing conditions and temperatures exceeding 650 °C. The primary rare earth mineral in this ore, monazite was stable at all roasting conditions whilst florencite underwent thermal decomposition resulting in an increase in the monazite content of the roasted ore.