Rare-earth elements in mining industry's waste piles

Credit: Susan Heikkinen and Jani Närhi

If the necessary metals can be extracted from previously quarried ore, we can avoid the environmental hazards of new mines and cut back on mining waste.

In his doctoral research, Wenzhong Zhang from the Department of Chemistry at the University of Helsinki developed a new material, with which scandium, one of the rare-earth metals, can efficiently be extracted from the waste of the aluminium industry.

The amount of bauxite needed to manufacture one aluminium tin produces some 60 grams of reddish, clay-like substance, red mud that used to be dumped in the sea. Now it is amassing in producer countries, like Greece, as ever growing heaps, and there is over three billion tonnes of this waste in the world today.

– The problem is that the minerals we want are hidden in the waste heaps in very small quantities, and we do not have efficient methods for extracting them, says Wenzhong Zhang.

In his research supported by the EU H2020 REDMUD project, Wenzhong Zhang focused on scandium, a currently very interesting element due to its high cost and the mining of it that may soon start in Finland (the Rautalammi deposit). The use of scandium in combination with aluminium will make it possible to manufacture more durable aeroplanes and bicycles, for example, with a lighter structure.

A pinch of white powder is left at the bottom of the test tube. Is this the key that will solve the problem of waste?

Wenzhong Zhang is developing new, functional materials, with which we can capture the metal we want as a clean element, while the rest of the waste remains.

The work of a chemist is like building something from building blocks. Once the blocks fall into place, a usable material is born with features that can be further developed by engineers. One day, the method will be deployable on an industrial scale.

– At the moment, the aluminium industry does not put its focus on the metal extraction methods. It is more interested in looking for solutions that will make an end to the mountains of waste, says Wenzhong Zhang.

At the University of Helsinki, the Academy of Finland-funded USEMA project USEMA-project (Ultra-Selective Hybrid Materials for Separation of Group 3 and f-block Element) started by Risto Koivula is developing new materials on the basis of the research group’s expertise in methods of inorganic chemistry and ion exchange.

– There are many areas of application, such as transforming waste flows to raw material and development of new processes to destroy radioactive waste, or manufacturing radio-medicine, says Koivula.

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Wenzhong Zhang, M.Sc. will defend the doctoral dissertation entitled “Metal(IV) Phosphate Based Functional Materials for Selectively Harvesting Rare-Earth Elements from Bauxite Residue” in the Faculty of Science, University of Helsinki, on 23 November 2018

Professor Freddy Kleitz, University of Vienna, will serve as the opponent, and Professor Gareth Law as the custos.

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Original Source

https://www.helsinki.fi/en/news/science-news/rare-earth-elements-in-mining-industrys-waste-piles

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