Kimmanthudawage Isuri Nayantha PERERA1, Jennifer M. PRINGLE1, Cristina POZO-GONZALO1
1Deakin University, Melbourne, Australia
The increased demand for portable electronic devices and electric vehicles has resulted in an exponential increase in lithium-ion battery (LIB) and waste at the end of their life cycle. Spent batteries contain toxic, flammable chemicals, and heavy metals that create serious impact on human health and ecosystems. LIB recycling processes have become vital to protect the environment and recover critical metals. Specially, the recycling of cobalt has attracted much attention because it is expensive, and categorized as a CMR (carcinogenic, mutagenic, or toxic to reproduction) substance. The current recycling state of the art of cobalt on an industrial scale is based on using concentrated inorganic acids such as HCl, and H2SO4 with H2O2 as a reducing agent, which leads to the corrosion of equipment, generation of acidic wastewater, and emission of toxic gases (NOx, SO2 and Cl2).
Greener solvents for recovery of cobalt, deep eutectic solvents (DESs) and ionic liquids (ILs), are drawing much attention due to their unique chemical and physical properties. Several DESs have been studied to leach cobalt from LiCoO2 and cobalt oxides (Co3O4) in the literature. However, recovery of leached Co2+ using the electrodeposition approach in DES has not been given much attention. Electrodeposition has been considered as a more sustainable, cost effective and efficient approach to recover leached Co2+ compared to solvent extraction and chemical precipitation.
This research work is focused on electrochemical recovery of cobalt using environmentally friendly ethylene glycol based solvent systems at lower temperature (50 °C). Cyclic voltammetry was used to study the effect of anion and chemical composition of the solvent system on the electrochemical behaviour of Co2+. UV- Vis spectrophotometer was used to identify the coordination geometry of Co2+ in each solvent system. In addition, a broad range of characterization techniques were performed to investigate the Co recovery efficiency, morphology, and purity of the Co electrodeposits with inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) respectively.