Industrial waste and industrial waste management is a challenge that has plagued the steel and aluminum manufacturing industries for decades. For every ton of alumina produced another ton of bi-product, called bauxite residue, is produced. Every day nearly 2,000 tons of this heavy red mud like substance is created. At first glance bauxite residue seems like a waste, and some even consider it a form of pollution. So why did Greece recently begin importing large quantities of this substance from China? It is because bauxite residue contains several rare Earth elements, also known as REE’s, such as iron, titanium, silicon, and scandium. These elements are extremely valuable in even very small quantities. These REE’s drastically change the properties of certain materials, making them virtually irreplaceable in a number of manufacturing processes. REE’s are used to make turbines, cars, computers, smart phones, etc. Recently, Greek scientists have developed new technology that makes it possible to extract the REE’s from the red mud in an economical and environmentally friendly way.
How it’s Done
The technology developed to extract REE’s from bauxite residue is relatively new and advanced. The process begins by pouring the red mud into a reactor that contains a solution of ionic liquid. Ionic liquids are essentially “molten salt” that are liquid even at room temperature. Ionic liquids can be chemically changed and applied in a variety of extraction applications, making them extremely useful. They have been referred to as “the solvents of the future”. This liquid is the key to extracting the REE’s. It selectively extracts the REE’s without dissolving the entirety of the solid matter contained in the bauxite residue. Once the REE’s dissolve in the ionic liquid, the solution is then filtered to remove any additional solid residue. The remaining solid residue is then recycled. In order to get the REE’s back to their initial state acid is then added. What is left is the pure extracts of the REE’s. The process of extracting these REE’s takes only a couple hours. For each ton of alumina produced 1.5 kg of REE’s can be extracted. This adds up to 700,000 tons of REE’s being produced in Europe alone each year. This new application of ionic liquids can be fine-tuned to suit a number of processes, leading the way to a more sustainable use of fossil fuels and other exhaustible resources.
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