Deep Eutectic Solvents and the Future of the Critical Metals Circular Economy

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Waste Electrical and Electronic Equipment (WEEE) is the world's fastest growing waste stream, generating approximately 54 million tonnes per annum (Mtpa). The value of the metals contained in this waste stream is valued at £43Bn, including numerous precious and critical metals needed to move to a low carbon economy, most of which is lost to landfill. WEEE that is recycled is processed using inefficient and environmentally impactful smelting and refining processes that require significant energy, water use and discharge of large quantities of CO2 into the atmosphere, a processes that is at odds with commitments to a low carbon economy. The UK, which is one of the largest WEEE producers (23.9kg/person; 1.6mtpa) (UN GEM 2020), exports huge volumes of WEEE for recycling due to limited domestic and advanced recycling capacity. There is therefore a need within the UK for a domestic recycling option that can not only recycle and extract the trapped metal value within WEEE but do so in a more efficient and environmentally sustainable way. This research will build on current UK research into the application of a novel chemistry, known as Deep Eutectic Solvents (DES), in the extraction of metals form WEEE. The research aims to create a low impact alternative to current WEEE recycling methods, reducing the environmental impact of metals production and establishing the UK as a world leader in the field of environmentally sustainable metals recycling and production with the associated economic benefits of GDP increase and job creation. DES are based on very simple chemistry where molecules such as pro-vitamin B4, (in chicken feed), are combined with organic molecules such as citric acid, (in fruit), or urea, which is a (fertiliser) to form liquids that excel at dissolving metals. They are a class of biodegradable, environmentally benign, low cost, recyclable, water free, free of strong acid and base liquids that were developed in the UK as an alternative to highly dangerous, toxic and environmentally hazardous processes that are currently employed. They can dissolve metals out of mined ores and also WEEE, so can be applied to multiple metal processing industries. They do not produce large amounts of waste, greenhouse gases or other particulate emissions, require less energy and are highly efficient at dissolving a wide range of different metals. This makes them excellent solvents for recycling and recovery of metals that can then be used in the low carbon economy, such as nickel, copper, gold etc. which have uses in the move to electrification over fossil fuel use. DES can also extract other metals, including Rare Earth Elements (REE) which are crucial in the production of efficient permanent magnet motors for hybrid-electric vehicles and wind turbine generators.Rare Earth Element (REE) recovery is another critical industry to the UK economy however, China currently produces around 80% of the world's REE. Furthermore, only 1% of REE are currently recycled. The current processes are in many ways similar to the ones that are used in current WEEE recycling processes and so are also in need of cleaner alternatives. This presents an exciting and critical opportunity for the UK to develop new lower energy and environmentally safer technology to become global leaders in this industry as well. This would remove the reliance on countries like China for supply of these metals.The need for increasing WEEE recycling and establishing a sophisticated UK industry has been called for in the latest Environmental Audit Committee (EAC) report and securing the supply of REE outside of China, necessary for renewable projects such as the Dogger Bank wind farm, is a priority both at national and European level. These are both issues this research can help solve by recovering and recycling critical metals for a low carbon and circular economy in the UK. DES are exactly the technology to drive this metals recycling revolution in the UK forward.