Ionic liquids (ILs) and deep eutectic solvents (DESs) have proven to be suitable solvents and reactants for low-temperature reactions. To date, several attempts were made to apply this promising ...class of materials to metal oxide chemistry, which, conventionally, is performed at high temperatures. This review gives an overview about the scientific approaches of the synthesis as well as the dissolution of metal oxides in ILs and DESs. A wide range of metal oxides along with numerous ILs and DESs are covered by this research. With ILs and DESs being involved, many metal oxide phases as well as different particle morphologies were obtained by means of relatively simple reactions paths. By the development of acidic task-specific ILs and DESs, even difficultly soluble metal oxides were dissolved and, hence, made accessible for downstream chemistry. Especially the role of ILs in these reactions is in the focus of discussion.
Due to their typically low reactivity, the activation of metal oxides, as found in ores, earths and minerals, is in general performed by high temperature reactions, which consume much energy. Owing ...to the prevalence of fossil fuels, this is accompagnied by the generation of large amounts of CO
2
. Alternatively, ionic liquids (ILs) can be used as solvents for metal oxide dissolution and downstream chemistry at much lower temperatures. The dissolution ability of the dry ionic liquid betainium bis(trifluoromethylsulfonyl)imide, HbetNTf
2
, was investigated for 30 metal oxides at 175 °C and compared to chloride containing IL Hbet
2
NTf
2
Cl. A general dissolution-promoting effect of chloride anions was found, regarding reaction time as well as the variety of dissolved metal oxides. Up to now, the dissolution in Hbet
2
NTf
2
Cl is limited to basic or amphoteric metal oxides and assumed to be influenced by multiple factors, such as reaction conditions and the lattice energy of the metal oxide as well as its crystal structure. Comprehensive investigations were performed for the dissolution of CuO, which led to the discovery of the water-free complex compound Cu
2
(bet)
4
(NTf
2
)
2
NTf
2
2
. Proceeding from this compound, a complete exchange of the O-coordination sphere by other ligands was demonstrated, opening up promising possibilities for downstream chemistry.
Investigation on the dissolution of 30 metal oxides in the water-free ionic liquid HbetNTf
2
and the catalytic effect of chloride for the application in green ore processing.
The applicability of a deep eutectic solvent (DES) consisting of betainium hydrochloride, urea and glycerol is examined with respect to ionometallurgical metal extraction and compared with the ionic ...liquid (IL) betainium bis(trifluoromethylsulfonyl)imide (HbetNTf2). The DES dissolves numerous metal oxides, where not only betaine and chloride act as stabilizing ligands, but also nascent ammonia seems to be essential. From such solutions, cobalt, copper, zinc, tin, lead, and even vanadium can be electrodeposited, demonstrating the feasibility of ionometallurgy. However, repeated recycling of the DES is not conceivable. NMR spectroscopy and mass spectrometry identify numerous decomposition reactions taking place at 60 °C already. The by‐products that are formed not only make recycling more difficult, but also pose a toxicity problem. The opportunities and obstacles of DESs and ILs for their application in ionometallurgy are critically discussed. It is shown that a thorough understanding of the underlying chemical processes is critical.
The applicability of a deep eutectic solvent (DES), formed by betainium hydrochloride, urea and glycerol, for ionometallurgical metal production is investigated and critically discussed. Although several metals can be electrodeposited after rapid dissolution of the respective metal oxide, various decomposition reactions prevent the solvent from being usable and environmentally friendly.
The application of ionic liquids for the dissolution of metal oxides is a promising field for the development of more energy‐ and resource‐efficient metallurgical processes. Using such solutions for ...the production of valuable chemicals or electrochemical metal deposition requires a detailed understanding of the chemical system and the factors influencing it. In the present work, several compounds are reported that crystallize after the dissolution of copper(II) oxide in the ionic liquid HbetNTf2. Dependent on the initial amount of chloride, the reaction temperature and the purity of the reagent, copper crystallizes in complexes with varying coordination geometries and ligands. Subsequently, the influence of these different complex species on electrochemical properties is shown. For the first time, copper is deposited from the ionic liquid HbetNTf2, giving promising opportunities for more resource‐efficient copper plating. The copper coatings were analyzed by SEM and EDX measurements. Furthermore, a mechanism for the decomposition of HbetNTf2 in the presence of chloride is suggested and supported by experimental evidence.
The influence of reaction parameters of the dissolution of copper(II) oxide in the ionic HbetNTf2 and on the speciation of coordination compounds is investigated. The applicability to electrochemical copper deposition, especially the copper plating of steel, is shown.
Background High-sensitivity cardiac troponin (hs-cTn)-based diagnostic algorithms are recommended for the management of patients with suspected myocardial infarction (MI) without ST elevation. ...Although mirroring different phases of myocardial injury, falling and rising troponin patterns (FPs and RPs, respectively) are equally considered by most algorithms. We aimed to compare the performance of diagnostic protocols for RPs and FPs, separately. Methods and Results We pooled 2 prospective cohorts of patients with suspected MI and stratified patients to stable, FP, and RP during serial sampling separately for hs-cTnI and hs-cTnT and applied the European Society of Cardiology 0/1- and 0/3-hour algorithms comparing the positive predictive values to rule in MI. Overall, 3523 patients were included in the hs-cTnI study population. The positive predictive value for patients with an FP was significantly reduced compared with patients with an RP (0/1-hour: FP, 53.3% 95% CI, 45.0-61.4 versus RP, 76.9 95% CI, 71.6-81.7; 0/3-hour: FP, 56.9% 95% CI, 42.2-70.7 versus RP, 78.1% 95% CI, 74.0-81.8). The proportion of patients in the observe zone was larger in the FP using 0/1-hour (31.3% versus 55.8%) and 0/3-hour (14.6% versus 38.6%) algorithms. Alternative cutoffs did not improve algorithm performances. Compared with stable hs-cTn, the risk for death or MI was highest in those with an FP (adjusted hazard ratio HR, hs-cTnI 2.3 95% CI, 1.7-3.2; RP adjusted HR, hs-cTnI 1.8 95% CI, 1.4-2.4). Findings were similar for hs-cTnT tested in 3647 patients overall. Conclusions The positive predictive value to rule in MI by the European Society of Cardiology 0/1- and 0/3-hour algorithms is significantly lower in patients with FP than RP. These are at highest risk for incident death or MI.
URL: https://www.clinicaltrials.gov; Unique identifiers: NCT02355457, NCT03227159.
Owing to the environmental problems of numerous metal production processes, there is a growing need for more energy‐efficient approaches. Cobalt is considered a strategic element that is extracted ...not only from ores but also from spent Li‐ion batteries. One promising new approach is ionometallurgy, which is the extraction of metal oxides by ionic liquids (ILs). This study concerns new investigations into ionometallurgical processing of CoO, Co3O4, and LiCoO2 in the IL betainium bis(trifluoromethylsulfonyl)imide, HbetNTf2. Three crystal structures of cobalt−betaine complex compounds and combined spectroscopic and diffraction studies provide insights into the dissolution process. In addition, an optimized dissolution procedure for metal oxides is presented, avoiding the previously reported decomposition of the IL. Subsequent cobalt electrodeposition is only possible from cationic complex species, highlighting the importance of a thorough understanding of the complex equilibria. The presented method is also compared to other recently reported approaches.
The cobalt oxides CoO, Co3O4 and LiCoO2 are dissolved in the ionic liquid HbetNTf2, whereupon cobalt can directly be electrodeposited. A special focus is on understanding the complex equilibria present in solution and ways to manipulate them specifically. This is relevant for cobalt production from naturally occurring ores and lithium‐ion battery recycling.
Metals and functional metal-containing compounds are indispensable mass products. Metals are produced from low-reactive resources that are activated by very high temperatures (pyrometallurgy) or ...aggressive chemicals (hydrometallurgy). These traditional and highly optimized processes are often environmentally problematic because they require a lot of energy and generate large quantities of waste. Nowadays, numerous metal oxides and sulfides can be dissolved in ionic liquids (ILs) or deep eutectic solvents (DESs) at moderate temperatures below 200 C, at least on a laboratory scale. Some of these solutions are thermally and electrochemically stable enough to enable galvanic metal deposition. Moreover, valuable metal-containing compounds can by synthesized from them. This review discusses whether such ionometallurgical metal extraction could be a viable and sustainable alternative to conventional processes, focusing on the examples of copper, cobalt and aluminum. Among the various factors that are crucial for the sustainability and economic feasibility of ionometallurgical processes, we mainly focus on the chemical aspects, but also take a look at the availability, environmental impact and reusability of the new solvents. Although the challenges associated with ionometallurgy are great, especially when it comes to upscaling, ionometallurgy could contribute to a more sustainable production of metals and metal compounds and also provide rewarding results in other areas,
e.g.
battery applications.
Ionometallurgy can contribute to a sustainable production of metals and their compounds. In this context, chemical aspects, availability, environmental impact, and reusability of ionic liquids and deep eutectic solvents are critically discussed.
The Cover Feature symbolizes the recovery of cobalt metal from battery materials. Cobalt oxides are dissolved in an ionic liquid to form cobalt complexes, and the metal is electrodeposited directly ...from this solution. More information can be found in the Research Article by J. Richter et al.
In 2015, the United Nations General Assembly agreed upon 17 Sustainable Development Goals (SDGs) that are to be achieved by the year 2030. These goals were adopted to ensure an economical, socially ...just and ecologically sustainable development on a global scale and to protect natural resources and the environment
.
PDF
