E-waste management techniques have received global attention due to the abrupt accumulation of electrical and electronic wastes (WEEE) generated with rapid technology upgradation, as well as the short life span of electronic devices. The recycling of e-waste and the reuse of its constituents reduce the environmental contamination to an extent and are helpful in maintaining a circular economy1. In the modern technological world, the usage of lithium-ion batteries is inevitable due to their high energy density, which leads to over-demand and production. The overproduction expedites the formation of lithium-ion battery wastes, which are the prior source of LiCoO2. Hydrometallurgical recovery of metals from used LiCoO2 cathode materials consumes highly corrosive substances, such as inorganic acids, for the leaching process, thereby negatively impacting the environment. Deep Eutectic Solvents (DES) are a type of biocompatible solvents that emerged as a potential lixiviant for leaching applications. DES are the low-melting mixtures prepared by mixing carboxylic acid as a hydrogen bond donor (HBD) and choline chloride as a hydrogen bond acceptor (HBA)3. Here we have designed a choline chloride-carboxylic acid-based DES as an effective alternative to the conventionally used inorganic acids for the leaching of LiCoO2. Differential Scanning Calorimetry (DSC) curves provide information on the eutectic composition and melting point of the prepared systems, and the reducing ability of HBD was studied using cyclic voltammetry. The high chloride content from the choline-based DES stabilizes the reduced Co2+ by forming a blue color cobalt-chloro complex, which was proved by the UV-Visible spectroscopy4. As an extension of this, the molecular-level understanding of prepared DES and its leaching ability for different metal oxides are the future perspective.
References
(1) Schaeffer, N,; Passos, H,; Billard, I,; Papaiconomou, N,; Coutinho, J.A.P. Crit. Rev. Environ. Sci. Technol. 2018,48(13-15),859-922.
(2) Chen, L,; Chao Y,; Li, X. Green Chem. 2021,23(5),2177-2184.
(3) Tran, M.K,; Rodrigues, M.T.F,; Kato, K,; Babu, G,; Ajayan, P.M. Nat Energy. 2019,4(4),339-345.
(4) Peeters, N,; Binnemans, K,; Riano, S. Green Chem. 2020,22(13),4210-4221.