Clean and Zero Emission Processes for Chemical Extraction of Critical and Precious Metals with Deep Eutectic Solvents

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The conventional methods for chemical extraction of metals have generally been used by the mining industry for the recovery of metals from primary (e.g. ores) and secondary (i.e. end-of-life products) resources. The mineral acids and organic extractants are the common choice of chemicals for metals extraction. The recovery of metals using hydrometallurgy is of major importance with the growth in metal demand, largely due to electrification revolution in our societies. In recent years, a novel medium for metal extraction, known as deep eutectic solvents (DES), has been introduced. DES carry similar properties to ionic liquids but with additional advantages of low cost, far less environmental impact, and easy synthesis processes for their production in large scale in mining and metals extraction operations. Introduced only very recently, DES have found some very interesting applications in metals extraction processes from primary and secondary resources, however a limited literature is available on this topic. Hydrophilic DES can be used for leaching of metals and have great potential to replace mineral acids, and to reduce water consumption in metals extraction processes. Efficient and selective leaching of metals from minerals or wastes is feasible by using DES. However, the kinetics of leaching as well as the physicochemical properties of DES are still limiting their large-scale application. Electrochemical recovery from DES is also possible but deserves further investigation. On the other hand, hydrophobic DES can be used to recover metals from aqueous solutions e.g., for the solvent extraction of metals, hydrophobic DES constitute credible alternative ionic liquids. In this proposal, we aim to explore hydrophilic and hydrophobic DES for the extraction and recovery of metals from primary and secondary sources. In the first part of work, we will focus on the synthesis and characterization of DES and optimize them for the extraction and recovery of metals. The metals of our interest include nickel, cobalt, lithium, rare earths elements, gold and copper. In the later stage, the optimized DES systems will be explored for the extraction and recovery of the said metals from primary and secondary resources. The long-term goals of this research program are to develop robust metals extraction processes based on novel DES systems and build a comprehensive understanding of the chemistry of the process. Within a long-term plan we will define the environmental and economic benefits of the DES systems. During the next five years, we will design and try different DES systems for metals extraction, using the fail-fast design system. The DES metals extraction systems have the strong potential to make a revolution in the way we extract metals from the resource materials, substantially lowering the water consumption and use of toxic reagents. Two Ph.D. students and four Master's students will be trained through this research program.