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Removing the copper (and other metals like zinc, lead and molybdenum) typically found in sulphide ores involves a process of burning the minerals to remove the sulphur, which produces sulphur dioxide- a dangerous chemical that is converted to sulphuric acid.
Now a team of MIT researchers in the United States has shown that they can separate pure copper and other trace elements from sulphur-based minerals using molten electrolysis. Under the process, an electric current is passed through a molten substance, which produces a chemical reaction that separates the materials without producing toxic byproducts such as sulphur dioxide.
“It is a one-step process, directly just decompose the sulfide to copper and sulfur. Other previous methods are multiple steps”: post-doctoral researcher Sulata Sahu
By forming liquid copper metal and sulphur gas from an electrolyte composed of barium sulphide, lanthanum sulphide and copper sulfide, they were able to get yields greater than 99.9 percent pure copper – equivalent to the best current copper production methods, according to MIT News.
“It is a one-step process, directly just decompose the sulfide to copper and sulfur. Other previous methods are multiple steps,” post-doctoral researcher Sulata Sahu explained. “By adopting this process, we are aiming to reduce the cost.”
The work builds on a 2016 paper published in the Journal of The Electrochemical Society which offered proof of electrolytic extraction of copper.
“This paper was the first one to show that you can use a mixture where presumably electronic conductivity dominates conduction, but there is not actually 100 percent. There is a tiny fraction that is ionic, which is good enough to make copper,” said Antoine Allanore, assistant professor of metallurgy at MIT.
The experiments were conducted at 1,227 degrees Celsius, which is about 150 degrees above copper’s melting point and the temperature commonly used for industrial copper extraction.
6 Comments
Rob bowell
Nice idea but is this really practical? How much La sulfide is needed? Sounds like the starting materials are more expensive than any revenue!
Enoch Pax
The power alone needed to attain 1,227 degrees C will cost a lot of money plus the environmental costs associated with the power generation though It is good research,
Mike Failla
I would like to see what it costs to produce that wee bit of copper from the standpoint of materials, production and power. I have a feeling that it may be more expensive to produce, per ton than the present smelting processes.If it is cost effective then they may be on to something…still, industry needs sulphuric acid so……
Nordbird
First you would need molten concentrate, presumably produced in an electric furnace. Then, you would need electrolysis of the molten material. There was no mention of the recovery rate, total electricity consumption, and total production cost.
Basically, I would think twice before hiring someone claiming to be a MIT metallurgist.
Mark Harder
What happens to the sulfur in the electrolysis? At that temperature, elemental sulfur is molten, and not very dense. So it would float to the top of the vat. In the presence of air, it would burn and voila! sulfur dioxide (again). Perhaps something else happens to it, but I can’t imagine what. I hate to add to the chorus of negatives in the comments, but questions like these need to be answered. Maybe they are answered in the J. Electrochemical Soc. article.
Limeno
The MIT article gives some more detailed information relating the process:
“…but the new method produces elemental sulfur, which can be safely reused, for example, in fertilizers.”
“…negatively charged sulfur ions are reacting at the anode…”
“The amount of energy required to run the separation process in an
electrolysis cell is proportional to the faradaic efficiency and the
cell voltage. […] 0.45 volts for copper sulfide.”
“The new work doubles the efficiency [faradaic efficiency, aluminium’s faradaic efficiency is @ 95%] for electrolytic extraction of copper […] to 59 percent”