SGS tests show enviro-formula oft beats traditional leaching Metal Tech News - December 8, 2021
In spite of its toxic and corrosive reputation, cyanide has been the go-to chemical for gold recovery since 1890 due to its unmatched ability to dissolve the precious metal into a solution. Or, more precisely, previously unmatched ability to recover gold.
A new, more environmentally sound formula has been developed in Canada that rivals and sometimes even exceeds cyanide gold recovery, according to tests carried out by world-leading analytical firm SGS.
Developed by EnviroMetal Technologies Inc. (formerly EnviroLeach Technologies Inc.), this formula is a proprietary blend of five ingredients that are FDA approved for human consumption that can dissolve gold contained in ores, concentrates, and recycled electronics. The aurum is then recovered with a diamond-based electrochemical process developed by the British Columbia-based company.
The benign gold dissolving advantages by EnviroMetal offer an alternative for gold mining companies seeking to boost their environmental, social, and governance credentials.
The results from SGS testing indicate that there is little to no gold recovery trade-off for the ESG advantages offered by the cyanide-free EnviroMetal formula.
According to tests carried out at an SGS lab in BC, the EnviroMetal formula outperformed cyanide on high-grade ore samples from a Canadian mine.
A one-gram-per-liter concentration of the EnviroMetal formula recovered 99.6% of the gold from a 675-grams-per-metric-ton gold sample in just six hours, compared to 93.9% recovery in 24 hours with the same concentration of cyanide.
Using the same concentrations, the EnviroMetal formula recovered 92.5% of the gold from flotation concentrates averaging 55.1 g/t gold, compared to 93.5% over 30 hours with cyanide.
In addition to superior recoveries from the high-grade ore and comparable recoveries from the concentrate sample, the EnviroMetal process began leaching the gold out of these samples much quicker than cyanide.
As part of an analysis of the sustainability and economics of EnviroMetal's formula and process, SGS carried out a series of ten locked cycle tests to evaluate the reusability of the lixiviant.
Reusing the same lixiviant in each round of testing, the EnviroMetal formula recovered 88% to 99% of the gold from ten separate ore samples. While there was variance with each sample, there was no evident trend of reduced recoveries, and the formula was still recovering 96% of the gold by the tenth round.
"These are probably our most important test results to date. They confirm equivalent or better recoveries than cyanide, faster leach kinetics than cyanide, and prove the sustainable, and reusable nature of our formula," said EnviroMetal CEO Duane Nelson. "This continued reusability is the foundation of our powerful and eco-friendly lixiviant. The EnviroMetal formula provides a very effective and sustainable alternative to cyanide and smelting for the recovery of gold with an almost zero environmental footprint."
Following the testing by SGS, testing carried out on material from P2 Gold Inc.'s Gabbs gold-copper project in Nevada returned roughly 90% gold recoveries from much lower grade samples averaging 0.72 and 1.45 g/t gold.
"We decided to investigate the use of EnviroMetal's eco-friendly gold extraction solutions for our Gabbs project because of its record of extracting gold for other projects," said P2 Gold President and CEO Joe Ovsenek. "With gold recoveries of approximately 90% for the Gabbs samples, the initial test work was definitely a success. Given these encouraging initial results, we intend to evaluate EnviroMetal's process as an alternative for gold recovery as we advance engineering for the Gabbs project."