Solid-state batteries (SSBs) are promising next-generation batteries due to their potential for achieving high energy densities and improved safety compared to conventional lithium-ion batteries ...(LIBs) with a flammable liquid electrolyte. Despite their huge market potential, very few studies have investigated SSB recycling processes to recover and reuse critical raw metals for a circular economy. For conventional LIBs, hydrometallurgical recycling has been proven to be able to produce high-quality products, with leaching being the first unit operation. Therefore, it is essential to establish a fundamental understanding of the leaching behavior of solid electrolytes as the key component of SSBs with different lixiviants. This work investigates the leaching of the most promising Al- and Ta-substituted Li7La3Zr2O12 (LLZO) solid electrolytes in mineral acids (H2SO4 and HCl), organic acids (formic, acetic, oxalic, and citric acid), and water. The leaching experiments were conducted using actual LLZO production waste in 1 M of acid at 1:20 S/L ratio at 25 °C for 24 h. The results showed that strong acids, such as H2SO4, almost completely dissolved LLZO. Encouraging selective leaching properties were observed with oxalic acid and water. This fundamental knowledge of LLZO leaching behavior will provide the basis for future optimization studies to develop innovative hydrometallurgical SSB recycling processes.
This research presents a novel precipitation method for scandium (Sc) concentrate refining from bauxite residue leachates and the effect of aqueous media on this triple-stage successive precipitation ...process. The precipitation pattern and the precipitation behavior of the constituent elements was investigated using different precipitation agents in three major mineral acid media, namely, H2SO4, HNO3, and HCl in a comparative manner. Experimental investigations showed behavioral similarities between HNO3 and HCl media, while H2SO4 media was different from them because of the nature of the formed complexes. NH4OH was found to be the best precipitation agent in every leaching media to remove Fe(III) with low Sc co-precipitation. To limit Sc loss from the system, Fe(III) removal was divided into two steps, leading to more than 90% of Fe(III) removal at the end of the process. Phosphate concentrates were produced in the final step of the precipitation process with dibasic phosphates which have a strong affinity towards Sc. Concentrates containing more than 50% of ScPO4 were produced in each case from the solutions after Fe(III) removal, as described. A flow diagram of the selective precipitation process is proposed for these three mineral acid media with their characteristic parameters.
The need of light weight alloys for future transportation industry puts Sc and Ti under a sudden demand. While these metals can bring unique and desired properties to alloys, lack of reliable sources ...brought forth a supply problem which can be solved by valorization of the secondary resources. Bauxite residue (red mud), with considerable Ti and Sc content, is a promising resource for secure supply of these metals. Due to drawbacks of the direct leaching route from bauxite residue, such as silica gel formation and low selectivity towards these valuable metals, a novel leaching process based on oxidative leaching conditions, aiming more efficient and selective leaching but also considering environmental aspects via lower acid consumption, was investigated in this study. Combination of hydrogen peroxide (H
O
) and sulfuric acid (H
SO
) was utilized as the leaching solution, where various acid concentrations, solid-to-liquid ratios, leaching temperatures and times were examined in a comparative manner. Leaching with 2.5 M H
O
: 2.5 M H
SO
mixture at 90 °C for 30 min was observed to be the best leaching conditions with suppressed silica gel formation and the highest reported leaching efficiency with high S/L ratio for Sc and Ti; 68% and 91%; respectively.
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Rare-earth elements (REEs) were efficiently recovered by a supported ionic liquid phase (SILP) after iron(III) precipitation from simulated bauxite residue (BR) leachates in sulfuric acid media, ...since leaching of BR with sulfuric acid is more feasible than leaching with other mineral acids. The SILP betainium sulfonyl(trifluoromethanesulfonylimide) poly(styrene-co-divinylbenzene) Hbet-STFSI-PS-DVB exhibits a high selectivity for the rare-earth elements (REEs) over other elements in acidic BR leachates. However, scandium(III) uptake by the Hbet-STFSI-PS-DVB from sulfuric acid leachates is difficult due to strong electrostatic interactions of small scandium(III) ions with sulfate anions. Sulfuric acid leachates generally contain high concentrations of base metal ions like iron(III) and this reduces the efficiency of the Hbet-STFSI-PS-DVB for uptake of REEs. Therefore, a precipitation step for iron(III) removal with aqueous ammonia solution was introduced, as a simple and economically viable pretreatment step of BR leachate, prior to the REEs recovery by the SILP. Iron(III) precipitation from sulfuric acid BR leachates increased the efficiency of purification by column chromatography. Additionally, scandium(III) phosphate precipitation, after iron(III) removal, was performed in order to compare and assess the optimum route for scandium(III) purification between the two common processes: selective precipitation and elution chromatography. After scandium(III) phosphate precipitation, the recovery and subsequent purification of the remaining REEs on the Hbet-STFSI-PS-DVB column were also examined, and resulted in a higher purity of these REEs.
•Rare earths were efficiently recovered by a supported ionic liquid phase.•Precipitation of iron enhanced the purity of rare earths.•High-purity scandium was obtained by column chromatography.•The method is applicable to HNO3, HCl and H2SO4 bauxite residue leachates.•Scandium could be precipitated as ScPO4.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A combination of pyrometallurgical and hydrometallurgical processes showed promising results for the sustainable valorisation of red mud with selective iron recovery. However; high Si content in red ...mud and its slags produced by pyrometallurgical treatment for the Fe removal makes these secondary resources untreatable with conventional acid leaching routes due to the formation of silica gel. In this study, red mud and slags synthesized by electric arc furnace smelting, which contain both moderate and extensive SiO2, were exposed to dry digestion aiming selective Sc recovery with suppressed Ti and Si dissolution. Various additions of concentrated sulfuric acid were investigated to find out the optimum acid consumption for this process. A promising Sc leaching efficiency was found for acidic slag (~80%), where Ti dissolution was suppressed to <10% and without Si gel formation. The mineralogical content of red mud and the two slags were analysed by QEMSCAN and XRD in order to elucidate the leaching mechanism. Using the findings of this study, an empirical dry digestion leaching model was proposed for each starting material in a comparative manner.
•Dry digestion process was applied to red mud and EAF-treated slags.•The role of crystallinity and the chemistry was investigated.•Formation of silica gel was completely suppressed with dry digestion.•Supressed Ti with enhanced Sc efficiency was obtained in Si-enriched red mud slag.•Comparative mechanisms of dry digestion processes was proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Solid-state batteries (SSBs) are promising next-generation batteries due to their potential for achieving high energy densities and improved safety compared to conventional lithium-ion batteries ...(LIBs) with a flammable liquid electrolyte. Despite their huge market potential, very few studies have investigated SSB recycling processes to recover and reuse critical raw metals for a circular economy. For conventional LIBs, hydrometallurgical recycling has been proven to be able to produce high-quality products, with leaching being the first unit operation. Therefore, it is essential to establish a fundamental understanding of the leaching behavior of solid electrolytes as the key component of SSBs with different lixiviants. This work investigates the leaching of the most promising Al- and Ta-substituted Lisub.7Lasub.3Zrsub.2Osub.12 (LLZO) solid electrolytes in mineral acids (Hsub.2SOsub.4 and HCl), organic acids (formic, acetic, oxalic, and citric acid), and water. The leaching experiments were conducted using actual LLZO production waste in 1 M of acid at 1:20 S/L ratio at 25 °C for 24 h. The results showed that strong acids, such as Hsub.2SOsub.4, almost completely dissolved LLZO. Encouraging selective leaching properties were observed with oxalic acid and water. This fundamental knowledge of LLZO leaching behavior will provide the basis for future optimization studies to develop innovative hydrometallurgical SSB recycling processes.
Anticipated future demand and limited primary sources of Sc highlight the importance of secondary Sc resources such as bauxite residue (red mud). In this study, a process route starting from red mud ...aiming to recover Sc as a concentrate by a combination of pyrometallurgical and hydrometallurgical processes was developed. Bauxite residue was treated in an electric arc furnace (EAF) for Fe removal as well as slag conditioning with varying flux additions and various cooling conditions. 95% of iron recovery to the metal was achieved. Resulting slags were subjected to identical H
O
supported H
SO
leaching conditions at 75 °C. The effect of slag mineralogy and crystallinity on the leaching efficiencies were investigated using XRD and QEMSCAN analysis. As a result of the highly amorphous nature of acidic slags, maximum of 72% Sc leaching was obtained. For leached slags, water quenched basic slag was found to be the most promising condition resulting in an extreme Sc leaching yield of 97% and this slag was selected for the further Sc precipitation. High impurity removal rates and selective Sc separation were achieved with a triple-stage successive precipitation to synthesize a Sc concentrate. Starting from EAF treatment followed by leaching and precipitation, 85% of the initial Sc in the red mud was successfully recovered as Sc phosphate.
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The high volume of mine tailings generated during mining activities poses significant worldwide storage risks. However, these tailings often contain valuable metals that can be recovered. Therefore, ...reprocessing mine tailings has emerged as a crucial strategy to assess secondary metals resources and mitigate storage risks. Furthermore, the mining industry’s extensive use of freshwater necessitates exploring alternative water sources. In this study, the leaching of base metals from mine tailings in chloride-based media was investigated. Approximately 52% Cu, 73% Zn, and 100% Pb were leached from the sample in the presence of HCl and NaCl. The substitution of freshwater with seawater yielded comparable results, demonstrating the potential of seawater as an alternative freshwater source that does not compromise leaching effectiveness. Additionally, 77% of Pb precipitated as PbSO4 from the pregnant leach solution. Through solvent extraction, approximately 100% Cu was recovered using LIX 984 as an extractant, and 71% Zn with D2EHPA. The use of Fe0 significantly reduced the co-extraction of Fe in the Zn recovery step. Overall, this study provides a potential route for reprocessing mine tailings, ensuring maximum leaching and efficient recovery of metals from sulfide mine tailings.
The application of scandium (Sc) is hindered by insufficient supply. The majority of the world Sc supply is sourced from industrial byproducts, where Sc needs to be separated from other components. ...Phosphate precipitation is an effective separation and purification method to harvest dissolved Sc ions from acidic leachate solutions; however the obtained Sc phosphate currently has no direct application. To this end, a solid-state conversion route of Sc phosphate to oxide was investigated by using five different sodium compounds, as sodium forms very stable phosphate compounds. The thermal conversion (up to 1000 °C) of Sc phosphate with high melting point sodium compounds (sodium sulfate, carbonate, and chloride) yielded a stable mixed sodium–scandium phosphate phase with a formula of Na3Sc2(PO4)3. The thermal conversion with lower melting point sodium compounds (sodium hydroxide and nitrate) resulted in the separation of Sc from phosphate moieties, forming respectively Sc oxides (NaScO2 or Sc2O3) and sodium phosphate. In situ high temperature X-ray diffraction, differential scanning calorimetry (DSC), and thermogravimetry (TGA) were employed to investigate the solid-state conversion process by sodium nitrate. Slower heating rate (120 °C/h) and the evolution of oxygen gas (as a result of sodium nitrate decomposition) favored the formation of Sc2O3 phase over NaScO2 phase, and the conversion reaction was completed at 670 °C. The conversion process was further explored as a purification step toward Sc-containing mixed phosphate precipitates, where the impurities (aluminum and iron phosphates) were converted into sodium aluminate and ferrite and could then be separated from Sc2O3 by their differences in acid/base solubility.
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