Gold leaching with edible ingredients
Sustainable EnviroLeach gold recovery excites Yukon miner Metal Tech News Weekly Edition – March 4, 2020
Last updated 6/27/2020 at 5:26am
EnviroLeach Technologies Inc.
Looking to put its best foot forward when it comes to environmental, social, and corporate governance (ESG), Golden Predator Mining Corp. is testing a non-cyanide and environmentally friendly way to extract the otherwise hard to recover gold from its mine project in the Yukon.
For more than 130 years, cyanide has provided an inexpensive and effective means of extracting gold from ore. A chemical compound of carbon and nitrogen, cyanide dissolves gold into a solution, from which the precious metal can be recovered. The downside to cyanide, however, is it is toxic and could be dangerous if not handled properly. While mines around the world have shown that cyanide leaching of gold can be safe if used appropriately, and the compound is biodegradable, in recent years there have been breakthroughs in research into less toxic alternatives.
One such solution has been developed by EnviroLeach Technologies Inc., a company that is using five ingredients that are FDA approved for human consumption to dissolve and a diamond-based electrochemical process to ultimately recover gold and other metals from ores, concentrates and recycled electronics.
While EnviroLeach's patent-pending formula is proprietary, the company said the leach kinetics of the gold dissolving chemical compound it has developed is superior to cyanide. The best part is, however, the EnviroLeach process offers an almost zero environmental footprint, with no off gassing, no water effluent and does not require special storage for waste material.
"We are setting a new paradigm for sustainable and economic metals processing," said EnviroLeach Technologies President and CEO Duane Nelson. "EnviroLeach is clearly establishing itself as a market leader with a best-in-class technology solution."
A solution that is proving to be highly successful in recovering gold from concentrates collected from a bulk sample plant at Golden Predator's 3 Aces project in Canada's Yukon Territory.
Golden Predator has been testing this process to recover the gold from the No. 2 concentrate produced from bulk sampling of high-grade gold mineralization at 3 Aces.
A gravity processing plant captures roughly 85 percent recovery of the contained gold without the use of chemicals. This gold reports to two concentrates. The No. 1 concentrate is poured into doré bars and shipped to a refinery for further processing. The No. 2 concentrate, which contains heavy mineral sands with some gold, has been set aside for further processing.
A sample of this gold-bearing concentrate recovered during bulk sampling in 2018 was shipped to the EnviroLeach facility in Surrey, British Columbia last fall.
Using the EnviroLeach solution, 96.5 percent of the gold was recovered from a 55.9-kilogram initial sample of the material in just six hours.
Electrowinning, a process of recovering metals from a solution using electrical current, was used to pull the gold out of solution and a 91.3-gram (2.9 ounces) bar was poured.
Using Golden Predator's Secondary Recovery Unit (SRU), a trademarked name for the processing equipment that is being tested using the EnviroLeach process, an initial five metric ton bulk sample is being tested in phases at the site of the company's gravity recovery plant on the 3 Aces property.
Eleven test batches totaling roughly two metric tons of this sample material resulted in 93.2% recovery of contained gold yielding 132.2 oz of gold doré. Golden Predator said recoveries improved as the tests advanced with the final five test batches yielding 96.8% recovery of gold.
"The test processing plant operation and the SRU are examples of Golden Predator's commitment to innovation aligned to environmental and social responsibility (ESG)," said Golden Predator Mining CEO Janet Lee-Sheriff.
The EnviroLeach process delivers numerous benefits over current leaching techniques and has the potential to unlock the value of many deposits located in environmentally sensitive areas that cannot be developed using current extraction methods.
"The results clearly show that our cyanide-free alternative represents a commercial opportunity for many projects and jurisdictions. When we received the successful results, we altered our course of work at the plant to focus greater time and energy on this new technology," said Lee-Sheriff. "We are now assessing some potential commercial applications for this innovative development and we expect to provide more information on these opportunities in the near future."