Recovery of Rare Earth Elements from spent Nickel-Metal Hydride Batteries from Hybrid Electric Vehicles
Abstract: Rare earth elements (REE) are a group of elements that are of critical importance in numerous technological applications, including “green technologies” such as wind turbines and hybrid car batteries. When the criticality of applications is considered, problems in supply has brought the option of effective secondary resource utilization into consideration. In this thesis, several methods have been developed and assessed to recover REE from spent hybrid electric vehicles batteries.Leaching of the NiMH active anode and cathode materials with sulfuric acid and hydrochloric acid has been carried out. Acid recovery using nanofiltration has been investigated. Further, precipitation of a mixed REE concentrate has been studied. The REE were separated as sodium double sulfate salts after sulfuric acid leaching by addition of a sodium salt. In addition, antisolvent precipitation of REE sulfates were studied by addition of alcohols. The REE sulfate salts can easily be dissolved for further processing and recovery of the individual elements by other techniques. As an alternative a process based on sulfation, selective roasting and water leaching was investigated. This allowed recovering an aqueous REE sulfate solution also suitable for further processing to recover the individual REE by e.g. solvent extraction or chromatographic separation. A complimentary LCA study was conducted in collaboration with IVL. Here certain selected recycling methods were scaled up on paper and the environmental burdens of the different processes were compared. The results obtained have proven the effectiveness of different recycling methods. It is foreseen that Europe will be guiding the efforts on recycling whether it is supply problems or value creation and battery recycling will have key importance.The work proves the importance of sustainable and resource efficient technologies for closing the loop for critical raw materials. The sustainable development of these processes has substantial importance to have continuous and uninterrupted access to the critical raw materials as well as displaying a responsible method of recycling and consumption which are aligned with UN Global Goals for a sustainable society.
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