Arsenic bubbles ease copper troubles

Arsenic occurs at varying levels in some copper ore bodies, and is a significant environmental hazard in the copper smelting process when emissions are released into the atmosphere.

In Australia, mining companies delivering copper concentrates containing high levels of arsenic to smelters are subject to substantial penalties, making some copper ore deposits economically unviable.

“Depending on what the concentrate grades of your ore are, our process might mean the difference between being able to sell your concentrate and not being able to sell it or getting a better price for it,” says CSIRO Minerals Experimental Scientist Leanne Smith.

“In the long term, it’s also better for the environment because you’re not sending that arsenic to the smelter.”

The standard flotation process involves copper ore being ground and made into a slurry, which is mixed with various chemicals. By pumping oxygen through the mix, the copper concentrate rises to the top and is then scraped off.

CSIRO’s development involves using electrochemical processes during flotation. By studying individual copper minerals’ flotation behaviour, including the copper-arsenic minerals, the CSIRO team has identified several electrochemical windows whereby it is possible to selectively float copper-arsenic minerals from other copper minerals. This produces a much purer form of copper concentrate, with low arsenic content, that can be supplied to smelters.

“If you’re running a flotation process, then this wouldn’t be that difficult to implement,” says Ms Smith.

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