New cleaner smelting process accidentally discovered

25 Aug 2016

Some of our best discoveries are made by accident and, in the most recent case, a team of MIT researchers stumbled upon a method of smelting metals that could drastically reduce the carbon emissions produced.

Before such a smelting process was even considered, the MIT team had been working on developing a new type of battery, however, during testing, they realised that they actually stumbled across an entirely new way of producing the metal antimony.

While antimony remains a metal of limited use in the wider world, the researchers believe the same process could be applied to smelting and the production of other more economically important metals, like copper and nickel.

Can ‘virtually eliminate’ CO2 emissions

By applying this new smelting process, the researchers believe it could not only reduce the cost of smelting significantly compared with current methods, but “virtually eliminate” the associated CO2 emissions that come with it.

Speaking with MIT News, the research team described how they were originally attempting to develop a different electrochemistry for a battery using molten metals or salts with different densities.

However, following one attempt, things got rather weird, resulting in the creation of antimony from the molten semiconductor, antimony sulphide, rather than a charge for their battery.

In fact, the antimony was being separated from the sulphide with a purity percentage of 99.9pc and collecting at the bottom of the ‘battery’, while the sulphur gas accumulated at the top.

To achieve electrolysis – seen in this discovery – a very good ionic conductor was layered on top of the molten semiconductor layer, making it a much cleaner smelting process than any current available methods.

“Antimony sulphide is a very good conductor of electrons,” explained researcher Donald Sadoway. “But if you want to do electrolysis, you only want an ionic conductor.”

Scaling up to more common metals

From an environmental perspective, this would make smelting significantly cleaner on the environment as, using current methods, the sulphur in this instance would bond with oxygen in the air creating sulphur dioxide, typically seen as acid rain.

Another major benefit to the wider world, however, will be the method’s scalability and use on other metals.

“The thing that made this such an exciting finding,” Sadoway said, “is that we could imagine doing the same for copper and nickel, metals that are used in large quantities.”

The challenge now for the researchers is to find a similarly-easy method of smelting these metals, as antimony has a much lower melting point of just 631ºC, compared to copper’s 1,085ºC.

The team’s research has been published in Nature Communications.

Smelting image via Shutterstock

Colm Gorey was a senior journalist with Silicon Republic