abstract
Ionic-liquid-based acidic aqueous biphasic systems (IL-based AcABS) represent a promising alternative to the solvent extraction process for the recovery of critical metals, in which the substitution of the inorganic salt by an acid allows for a 'one-pot' approach to the leaching and separation of metals. However, a more fundamental understanding of AcABS formation remains wanting. In this work, the formation mechanisms of AcABS are elucidated through a comparison with traditional aqueous biphasic systems (ABS). A large screening of AcABS formation with a wide range of IL identifies the charge shielding of the cation as the primary structural driver for the applicability of an IL in AcABS. Through a systematic study of tributyltetradecylphosphonium chloride ([P-44414] Cl) with various chloride salts and acids, we observed the first significant deviation to the cationic Hofmeister series reported for IL-based ABS. Furthermore, the weaker than expected salting-out ability of H3O+ compared to Na+ is attributed to the greater interaction of H3O+ with the [P-44414](+) micelle surface. Finally, the remarkable thermomorphic properties of [P-44414] Cl based systems are investigated with a significant increase in the biphasic region induced by the increase in the temperature from 298 K to 323 K. These finding allows for the extension of ABS to new acidic systems and highlights their versatility and tunability.
keywords
MOLECULAR-DYNAMICS SIMULATIONS; HOFMEISTER SERIES; MUTUAL SOLUBILITY; WATER-STRUCTURE; PALISADE LAYER; LITHIUM IONS; EXTRACTION; DENSITY; EXCHANGE; MICELLE
subject category
Chemistry; Physics
authors
Schaeffer, N; Passos, H; Gras, M; Mogilireddy, V; Leal, JP; Perez-Sanchez, G; Gomes, JRB; Billard, I; Papaiconomou, N; Coutinho, JAP
our authors
Germán Pérez-Sánchez
Junior Researcher
Helena Isabel Sousa Passos
Junior Researcher
José R. B. Gomes
Principal Researcher
Nicolas Schaeffer
Assistant ResearcherGroups
G4 - Renewable Materials and Circular Economy
G6 - Virtual Materials and Artificial Intelligence
acknowledgements
This work was part of the BATRE-ARES project (ERA-MIN/0001/2015) funded by ADEME and FCT. M. Gras would like to acknowledge labex CEMAM and EIT InnoEnergy H2020 for financial support. This work was partly developed in the scope of the project CICECO - Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013). Financial support from Fundacao para a Ciencia e a Tecnologia and Portugal 2020 to the Portuguese Mass Spectrometry Network (LISBOA-01-0145-FEDER-402-022125) is acknowledged.