Recycling tin and PGMs with EnviroLeach
Tests show promise for recovering critical metals from waste Metal Tech News – June 30, 2021
Last updated 7/6/2021 at 4:28pm
From research into a non-invasive mining technique to extract gold from the ground without mining to recycling electronic waste and old car parts, EnviroLeach Technologies Inc. has developed safe and environmentally friendly formulas to recover precious and critical metals.
Originally developed as an alternative to cyanide at gold mines, EnviroLeach developed a formula made up of five ingredients that are approved by the U.S. Food and Drug Administration for human consumption that dissolves gold and a diamond-based electrochemical process to recover the precious metals from solution.
Now, EnviroLeach has expanded its technologies to recycling gold and critical metals from e-waste and platinum group elements from catalytic converters.
"Our research continues to find new applications for our unique and proprietary chemistry and patented processes," said EnviroLeach Technologies CEO Duane Nelson.
These new applications include the recovery of tin from discarded printed circuit boards and platinum and palladium from the catalytic convertors that scrub harmful pollutants from the exhaust of internal combustion engines.
Tin from "digital ore"
EnviroLeach has been developing various formulas and technologies to recover the precious and critical metals contained in printed circuit boards from outdated computers, last generation smartphones, and the numerous other electronics becoming obsolete with the forward march of technology.
While each type of circuit board has its own special blend of metals, these electron superhighways at the heart of nearly every electronic device contain some mix of gold, copper, tin, palladium, and silver.
These circuit boards represent "digital ore" that can range from grades as low as US$700 to US$3,500 per metric ton for boards with low metal content to as high as $10,000 to $64,000/t for those with the highest amounts of precious and critical metals.
At an average of around US$4,000/t, the 3.14 million metric tons of outmoded circuit boards in old electronics forecast to be stuffed into desk drawers, sent to recycling centers, or simply thrown into landfills each year is estimated to top US$12.5 billion.
The EnviroLeach process has shown the ability to recovery high purity gold, and tin from circuit boards.
Results from a round of extensive testing reported by the company on June 24 demonstrate that the recovery and reusability of the formula after repetitive cycles of tin recovery.
Considered the glue of the technology revolution, tin is used extensively in the solders that make innumerable connections in electronics and electrical products.
With tin prices at record highs above US$32,000/t, the roughly 15 to 50 kilograms (33 to 110 pounds) of tin in every metric ton of circuit boards is worth around US$500 to US$1,600/t.
Locked-cycle reusability tests using low-grade circuit boards demonstrated continuous recoveries averaging 84.2% tin over 16 cycles, confirming the reusability of the EnviroLeach solution.
What stands out is the last four cycles recovered 87.7% of the tin, the highest average recovery of the testing.
And testing completed last year produced up to 92.6% tin recoveries from high-grade scrap circuit board concentrate material with the EnviroLeach solution.
A tin oxide product produced from this testing was sent to a refiner for detailed analysis and confirmation of the product's suitability for refining and sale.
"This marks a pivotal breakthrough for the entire electronics sector," said Nelson. "The cost-effective recovery of tin from scrap PCBAs (printed circuit board assemblies) has been a long-sought-after industry goal. This breakthrough technology could now lead to a significant secondary source for this critical and strategic metal."
The next stage of research is the development of a pilot-scale plant to perform bulk tests on a variety of PCBA-based concentrates to determine final process engineering and assess economics.
Catalytic PGM recovery
In addition to the promising results for recovering tin from scrap circuit boards, recent results from 14 months of testing indicate the viability of using the EnviroLeach process for recovering platinum and palladium from spent catalytic converters.
Using modified variations of the EnviroLeach formula and processes, this round of extensive testing demonstrated high recoverability for both platinum and palladium.
Samples taken from spent catalytic converter material were first ground then assayed to determine head grades for platinum and palladium.
The samples were then dissolved in several variations of EnviroLeach's proprietary formula and then tested using various concentrations of the formula, temperatures, and other test conditions.
Highlighted recoveries from the testing include:
• 98.1% platinum and 98.7% palladium from a sample averaging 5.92 million grams per metric ton platinum and 4.04 million g/t palladium.
• 93.5% platinum and 91.8% palladium from a sample averaging 5.41 million g/t platinum and 2.85 million g/t palladium.
• 96.8% platinum and 93% palladium from a sample averaging 4.56 million g/t platinum and 1.78 million g/t palladium.
• 95.7% platinum and 94.7% palladium from a sample averaging 7.95 million g/t platinum and 2.56 million g/t palladium.
"I am very excited about the results on our latest phase of research targeting the recovery of platinum and palladium from catalytic converters," said Nelson.
Given these results, EnviroLeach plans to optimize platinum and palladium recoveries and economics.
Upon completion of these and other related tests, the company intends to carry out a comprehensive phase of pilot plant testing.