Studies show that the new chloride-based process recovers 84% of gold compared to 64% recovered by traditional methods.
Gold is one of the most popular metals in the world. It is malleable, conductive and non-corrosive and is used in jewelry, electronics and even space exploration. However, traditional gold production usually contains the well-known toxin cyanide, which is banned from industrial use in some countries.
The waiting for a scalable, non-toxic alternative may now be over, as a research team at Aalto University in Finland has successfully replaced cyanide with an important part of gold extraction from ore.The results are published in Chemical engineering..
Traditionally, when gold ore is mined from the ground, it is crushed into powder and passed through a series of tanks in a process called leaching. Then cyanide is used to separate the gold from the ore into the leachate.
In the new process, the leaching and recovery process is carried out using chloride, one of the two elements of salt.
“To date, no one has developed a good way to recover small amounts of gold from industrial chloride solutions,” said Ivan Korolev, a project researcher and PhD candidate. increase.
“In our process, the amount of gold recovered using chloride is as high as 84%. By comparison, when using the standard cyanide process on the same ore, only 64% in the control experiment. I didn’t get it, “he explains.
This new process, called Electroplated Redox Permutation (EDRR), is the best combination of two common methods for extracting leached gold. A metal into a solution that reacts with gold. Professor Mari Lundström of the Faculty of Chemical Engineering at Aalto University and Kirsi Iriniemi, a university lecturer, are behind the development.
“With EDRR, a short electrical pulse is applied to create a thin layer of metal (copper in this case) on the electrode, causing a reaction in which gold encourages the copper layer to be replaced layer by layer,” Kororev said. Mr. says. “This method consumes less energy and does not require any additional elements.”
The study was carried out as part of a broader EU sustainability project called SOCRATES, in collaboration with Finnish mining technology giant Metso Outotec. Most of the experiments were conducted at the company’s research center in western Finland.
“The collaboration with Metso Outotec allowed us to develop methods in a way that was much closer to the actual implementation,” says Korolev. “At first it was about 9% recovery, then it grew to 25% and soon reached 70%, sometimes close to 95%.”
“It’s one thing to do such an experiment on a small scale, but no one did it on the scale we did. Our method is still really new, but traditional. We have shown that there are many potential successes as an alternative to the industrial process of the company, “he says.
“To date, no one has developed a good way to recover small amounts of gold from industrial chloride solutions.”
— Ivan Korolev
“Past extraction methods have always left behind some precious metals. Nowadays, the demand for metals is constantly increasing, so even these small amounts are important,” he says. “I think we can still increase yields with EDRR technology. We may not be able to reach 100%, but we can reach 90% or more.”
“It’s great to see a mining company interested in this technology and willing to test it in the field with ore.”
Kororev is also very personally interested in this project. He was born and raised in the Siberian mining town of Kemerovo, looking at both the positive and negative aspects of the industry. When he first studied mining engineering in Russia and then in several European universities, Kororev became interested in metallurgy and waste collection.
“Past extraction methods have always left some precious metals behind. Nowadays, the demand for metals is constantly increasing, so even these small amounts are important,” he says. “I think we can still increase yields with EDRR technology. We may not be able to reach 100%, but we can reach 90% or more.”
Reference: “Electric Hydrometallurgical Chloride Process for Selective Gold Recovery from Fire-Resistant Tellurized Gold Ore: Mini-Pilot Study”, Ivan Korolev, Pelin Altinkaya, Mika Haapalainen, Eero Kolehmainen, Kirsi Yliniemi, Mari Lundström, September 2021 8th of the month Chemical engineering..
DOI: 10.1016 / j.cej.2021.132283
Non-toxic technology extracts more gold from ore
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