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Cobalt and nickel are vital metals for the transition to a decarbonized society, currently in critical supply conditions to meet future demands. The recovery of those metals from secondary sources can mitigate this issue, as well as treating hazardous waste and increasing its economic value. In this work, ionic polymers inspired by deep eutectic solvents (DES) were studied for cobalt and nickel recovery from representative recycling solutions. These polymers were prepared by simple and fast photopolymerization process combining [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) with a series of hydroxylated compounds (e.g. alcohol and phenolic compounds). Different driving forces for metal absorption; ionic interactions, hydrogen bonding coordination, acidity of the media and polymer swelling have been investigated. The poly(METAC:1-butanol) polymer showed the highest absorption capacity (46 ± 5 mg g−1 and 46 ± 4 mg g−1 for cobalt and nickel, respectively), competing with conventional materials. Moreover, the metal stripping and recovery step was investigated. Favourably, deionized water presented the highest desorption efficiency, in comparison with HCl, rendering this process 'greener' and highly cost-effective. Finally, the ionic polymers were successfully reused as absorbents for five absorption/desorption cycles, maintaining structural integrity. This approach can pose an alternative way of using systems inspired by DES, with application at a larger scale upon further optimizations. [ABSTRACT FROM AUTHOR]

Cobalt has a vital role in the manufacturing of reliable and sustainable clean energy technologies. However, the forecasted supply deficit for cobalt is likely to reach values of 150 kT by 2030. Therefore, it is paramount to consider end-of-life devices as secondary resources for cobalt. Electrorecovery of cobalt from leached solutions has attracted attention due to the sustainability of the recovery process over solvent extraction followed by chemical precipitation. Recently, we reported Co electrorecovery from two different cobalt sources (CoCl2·6H2O and CoSO4·7H2O) using ethylene glycol : choline chloride (EG : ChCl) in a 4.5 : 1 molar ratio, leading to higher purity and easier electrodeposition when sulfate was present as an additive. Here, Co2+ speciation is reported for the two EG : ChCl systems depending on the cobalt source using several spectroscopic techniques (e.g. NMR, EPR, FTIR) in combination with molecular dynamics simulations. Monodentate coordination of SO42− to Co2+, forming the tetrahedral [CoCl3(SO4)]3− was observed as the dominant structure in the system containing CoSO4·7H2O, whereas the system comprising CoCl2·6H2O shows a homoleptic tetrahedral [CoCl4]2− as the dominant structure. This resulted in knowledge being gained regarding Co2+ speciation and the correlation with electrochemistry will contribute to the science required for designing safe electrolytes for efficient electrorecovery. [ABSTRACT FROM AUTHOR]

Membrane‐based gas separation technologies are one solution towards mitigating global emissions of CO2. New membrane materials with improved separation performance are still highly sought after. Composite membranes based on organic ionic plastic crystals (OIPCs) have shown preferential interaction for CO2 over N2, leading in some cases to competitive CO2/N2 selectivities. However, these ionic materials have been scarcely studied in the field of gas separation. Here, OIPCs based on the bis(trifluoromethylsulfonyl)imide ([TFSI]−) anion were investigated for use as gas separation membranes for the first time. The effect of the polymer type was also investigated, through the comparison of poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride)‐hexafluoropropylene (PVDF‐HFP) OIPC membranes. A strong temperature dependence of the gas separation performance was found, particularly in the N‐methyl‐N‐ethylpyrrolidinium‐based composites where the material undergoes a solid‐solid phase transition within the testing temperature range. The polymer type was noted to induce a strong effect on the structure of the composites, as well as affecting the gas and ionic transport. Thus, this research provides insights on the influence of the [TFSI]− anion on the structure and separation properties of OIPC‐based composites, and new information towards the development of novel OIPC‐based membranes with enhanced gas separation performance. [ABSTRACT FROM AUTHOR]

The recovery of critical metals from spent lithium‐ion batteries (LIBs) is rapidly growing. Current methods are energy‐intensive and hazardous, while alternative solvent‐based strategies require more studies on their 'green' character, metal dissolution mechanism and industrial applicability. Herein, we bridged this gap by studying the effect of dilute HCl solutions in hydroxylated solvents to dissolve Co, Ni and Mn oxides. Ethylene glycol emerged consistently as the most effective solvent, dissolving up to four times more Co and Ni oxides than using aqueous acidic media, attributed to improved chloro‐complex formation and solvent effects. These effects had a significant contribution compared to acid type and concentration. The highest Co dissolution (0.27 M) was achieved in 0.5 M HCl in 25 % (v/v) glycerol in water, using less acid and a significant amount of water compared to other solvent systems, as well as mild temperatures (40 °C). This solvent was applied to dissolve battery cathode material, achieving 100 % dissolution of Co and Mn and 94 % dissolution of Ni, following what was concluded to be a mixed mechanism. These results offer a simple alternative to current leaching processes, reducing acid consumption, enhancing atomic efficiency, and paving the way for optimized industrial hydrometallurgical processes leaning to 'greener' strategies. [ABSTRACT FROM AUTHOR]