Currently, most metals used in Europe’s industries are imported, which means supplies can be affected by instability in the countries where they are mined. They can also be subject to political decisions to restrict exports or to introduce tariffs such as those imposed on steel and aluminium by the US.

The CHROMIC project is aiming to change this dependence by looking to recover metals from waste and by-products that are already in the EU.

'We want to develop technologies that can help Europe to be more self-reliant for important metal resources in the future,' said Dr Liesbeth Horckmans, from the Flemish Institute for Technological Research (VITO) in Mol, Belgium, who is the project coordinator.

CHROMIC is focussing on a group of metals that are commonly used in everyday life – chromium, vanadium, molybdenum and niobium. All four metals are added to steel to make it more durable or increase its strength, but chromium is also a valuable chemical and pigment. Vanadium alloys are also ideal for making bicycle frames and gears, while niobium is used in prosthetics and pacemakers due to its hypoallergenic properties. Molybdenum is found in military armour, aircraft parts and fertilisers.

Around 45% of chromium, however, is brought into Europe from abroad while 100% of the other three metals are imported from South Africa, Brazil, the US, China, Russia, Kazakhstan and Turkey. But each of these metals are found in significant amounts in industrial by-products that are often discarded in the EU.

'We are focussing on steel slags (stony waste matter), stainless steel slags and ferrochrome slags,' said Dr Horckmans. At present, the team is looking at new slags being produced, although they have considered opening up old industrial landfill sites as well.

Extraction

Extracting metals from industrial residue isn’t easy though. The metals are present as fine particles that need to be separated out from the rest of the waste. Dr Horckmans and her team are developing a number of methods to remove them, including using magnetic fields to pull out metallic particles and water to dissolve the metal so it can then be recovered from the solution.

'We are developing a new process based on a combination of novel and existing technologies where we can recover metallic particles (from some of the slags) that can be reintroduced directly into the steel process,' said Dr Horckmans.

From the sources they are investigating, the team think their technologies could recover around 91,000 tonnes of these metals a year, equivalent to 5-10% of the EU's annual use. But the techniques could be applied to other types of industrial slag waste, such as incinerator ashes, to boost their quantities.

In addition, Dr Horckmans and her colleagues are looking at how to repurpose the material left behind after they have extracted the metal. Metals typically make up less than 5% of the waste, so the whole process would not be sustainable if the rest is not reused as well, said Dr Horckmans.

Metal-containing slags are already used in the construction industry as aggregates in concrete or asphalt, for example, so the remaining waste could be put to similar uses. But the material left behind after the metal is removed will be made up of finer grains, whereas the original slags are lumpy.

The team has developed a way of making bricks from this material by shaping them into rectangular blocks and using carbon dioxide to create a reaction that cements the particles together. 'It’s one of the applications we want to test,' said Dr Horckmans.

The project typifies a movement known as the circular economy, which aims to reuse discarded and waste materials for new purposes.



See the full version of the Discarded waste could be a treasure trove of rare metals article. It was originally published on Horizon: the EU Research & Innovation magazine | European Commission.

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