Ana R. F. CARREIRA1, André F. M. NOGUEIRA1, Anna P. S. CREMA1, Nicolas SCHAEFFER1, Helena PASSOS1, João A. P. COUTINHO1
1University of Aveiro, Aveiro, Portugal
It is estimated that over 50 million metric tonnes of electrical and electronic equipment waste (e-waste) are discarded annually. Recovering metals from e-waste is a sustainable alternative to ore mining. Lithium-ion batteries (LIB) are interesting candidates due to their high content of Co(II), Cu(II), Mn(II) and Li(I). Hydrophobic eutectic solvents (HES) are composed of a hydrogen bond donor and acceptor and can be tailored alternatives for metal extraction. Herein, an ionic liquid system composed of trioctylphosphine oxide (TOPO) and decanoic acid after saturation with HCl as to obtain the TOPOH+ Cl- adduct is used for metal recovery from LIB. Parameters such as HCl loading concentration, solid:liquid ratio, temperature and time were studied to understand their influence on the leaching selectivity and efficiency. The HES loaded with HCl was found to be more effective than aqueous HCl leachate due to the greater n(HCl):n(H2O) ratio in the HES which is twice that of 37 wt.% HCl. HES leaching enabled the selective extraction of Co(II) over Ni(II) when a stoichiometric excess of LIB to TOPOH+ Cl- was added, with over 91 % of Co(II) being extracted vs 52 % of Ni(II). Following the solid-liquid extraction, Co was selectively recovered from co-extracted Ni by using aqueous solutions as a counter solvent. The system could be regenerated by contacting with fresh HCl whilst NMR analysis confirmed the lack of solvent degradation.