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Goodbye to Cyanide: Green Technique for Metals Separation

We don’t often think about the precious metals inside our electronics and jewelry, and how those metals reached us. Driven by our passion for smart phones and now by growing demand for photovoltaics, precious metals is a booming business, with silver occupying 86% of the market in 2014 and production expected to reach 2 billion ounces by 2019 (in perspective, that is 62 million pounds, or 31,250 tons of silver). The U.S., China, India, Japan, and Russia were the top five consumers of silver in 2014. The downside? Separation of these metals has always required large amounts of cyanide, which if not properly contained, can wreak havoc on the environment.

Now, a century-old Russian firm has developed a less harmful way to separate metal without cyanide.  A new “acidless” vacuum distillation process technology separates out the more volatile metal based on difference in vapor pressures rather than through using environmentally harmful acids. The company behind this technology is Russian EZOCM Engineering, established in 1916. Their licensing partner in Italy, IKOI S.r.l., is actively promoting the acidless technology to the world market under the registered trademark ALS.

Traditionally, cyanide is used to dissolve the gold and the solution is adsorbed into activated carbon granules. More than 400 mineral processing facilities worldwide use this “best available technique (BAT)” for extracting of gold and other metals from low-grade ore. However, due to the highly poisonous nature of cyanide, the process is controversial and its usage is banned in a number of countries and territories. Unfortunately, this “best available technique” has been “available” for over 120 years.

Until now, the use of cyanide has been the only economically efficient process known for extraction of gold and silver. With proper management, cyanide can be used safely without harming the environment despite its toxicity. Cyanides do not cause cancer, and do not build up in the food chain. They do not persist in the environment, and are quickly broken down into less toxic chemicals, for example, by sunlight.

However, the problem in this case, as in many others, is human. There is always a possibility of a human error. Cyanide can leak into water causing environmental problems and pose serious threats to human health. In high concentrations, cyanide is toxic and can seep into the ground.

Earlier mining industry innovations have included new cyanide-destruction technologies and management strategies to reduce cyanide concentrations, toxicity, and potential impacts. Alternative extraction chemicals have been studied, but they can be equally or more damaging to the environment than cyanide.

New faster process saves operating costs

EZOCM declaration to the market at a conference of the International Precious Metals Institute in Texas in June 2015 was something new to the industry.

Saying goodbye to cyanide is not the only benefit of the acidless technology according to IKOI. Since the vacuum distillation machine can process dozens of kilograms gold or silver in an hour or less per cycle, the fast processing saves operating costs. The mineral processing, which usually comprises crushing, grinding, flotation, pressure oxidization, dissolution, and electrowinning, requires cyanide to separate gold and silver particles from ore in the middle of the process. The process is both time-consuming and complex — and even after the cyanide operation is complete, the gold extraction is still only halfway along.

The other benefit is that as there are no chemicals required  in the ALS separation process, there are no toxic fumes or vapors that could cause harmful effects in the workplace. There are also no environmental leakage issues.
























About Anne Irene Leino (8 Articles)
Anne-Irene Leino is a freelancer writer based in Helsinki, Finland. She is interested in sustainability, recycling and waste management, and energy efficiency. She covers clean technology in Europe, including R&D advances in Russia.

1 Comment on Goodbye to Cyanide: Green Technique for Metals Separation

  1. Wow, that’s really fascinating; I had no idea they previously would use cyanide for metal separation! It’s very cool that a non-cyanide technique has been developed. It’s always nice to see more environmentally friendly techniques being implemented.

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