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Obtaining coltan, the “black gold” of electronics, from the waste of an abandoned mine site

A team of CSIC researchers has developed a physical-chemical process to obtain niobium and tantalum, two of the most commonly used minerals in electronics, from the residues of a tin mine in Ourense. The procedure could be applied to other deposits for the extraction of these metals and also to clean areas where residues of other mining operations remain.

Tantalum oxide obtained in CENIM laboratories. Image: CENIM-CSIC.The process has been applied to the waste of Penouta mines, in Viana do Bolo (Ourense), a town of 3000 people at the northwest of Spain.

This mine was abandoned in the eighties after the end of the company Rumasa. Nowadays, it is the only European mine site where it can be obtained coltan, the 'black gold' of electronics.

Coltan, composed of columbite, tantalite and cassiterite, is the raw material from where niobium and tantalium oxides are obtained. These compounds are a main component for the production of smartphones, game consoles, batteries and other electronic devices.

These rare commodities are usually found in conflict geographical areas. According to the US Geological Service, Brazil was the first producer of niobium in 2019, with 65.000 tonnes, followed by Canada, with less than 8.000 tonnes. In Europe it is hardly found: just countries like Russia and Germany generate between the 2 and the 3 % of world ferroniobium production, the most commercialized form of this mineral.

On the other side, the Democratic Republic of the Congo is the first producer in the world of tantalum, with 740 tonnes, followed by Ruanda, where 370 tonnes in 2019 were produced. Again, the European countries (Germany and Austria) produce very small quantities of this compound.

“Several tonnes of coltan can be extracted from the mine wastes”, says the CSIC scientist Félix Antonio López Gómez, from the Centro Nacional de Investigaciones Metalúrgicas de Madrid (CENIM-CSIC). The team led by López Gómez has been working on this project for five years.

The project started as a commission by the company Strategic Minerals Spain, which manages nowadays the mine, after several geological studies suggested that these minerals could be obtained from the waste.

“Spain could become the first European producer. The obtained coltan could be sold to China”, say the scientists, although he also points out that this production “might be a turning point for the European manufacturing”.

The developed process could also help to clean the mine site from the pollution by the residues left after. Some projections suggest that the mine exploitation could last for 30 years more.