Mining and Process Solutions (MPS), an Australian company based in Perth, has unveiled a new leaching process for sustainable mineral extraction. Glycine leaching (Glyleach™️) claims the alkaline process it uses is low cost, readily available, and makes low-grade orphaned ore deposits commercially appealing.
Image Credit: Sergey Tarasov/Shutterstock.com
How the Glycine Leaching Process Works
The process uses manufactured amino acid glycine, obtained by combining chloroacetic acid and ammonia, with sodium hydroxide to provide sodium glycinate as the reagent.
The chemical reaction created by the reagent, causes metals to be released or leached from metal-rich minerals for much faster results than with conventional smelting processes.
For example, malachite will release the copper it contains when placed in a glycine solution through the process of chelation, whereby the copper bonds or grabs onto the glycine.
It can also be used to leach most other non-ferrous metals, including nickel, cobalt, and zinc, and precious metals gold and silver, as well as some platinum group metals. All of these leach at different rates and chemical conditions.
Sustainable Eco-Friendly Mineral Extraction
Glycine is a fully biodegradable and non-toxic amino acid. It was first discovered in 1820 by French chemist, Henri Braconnot, after he boiled gelatin with sulphuric acid.
The word originates from ancient Greece, meaning ‘sweet tasting’.
The bonus of glycine leaching is that most of the glycine can be recovered, and it is not consumed during the chemical process. This makes it a cost-effective, re-usable, sustainable mineral extraction process.
Small amounts of glycine are produced naturally by the body to create proteins essential for building muscle and body functioning processes.
It is sold commercially as a food supplement or sweetener and is found in gelatin, protein-rich foods, connective tissue, and bone and skin.
Glycine is also used in the non-sustainable herbicide manufacture of glyphosate, a highly toxic herbicide now banned, or being phased out in most countries around the world, including many US states.
Why Transitioning from Wasteful and Environmentally Damaging Cyanide Leaching to Glycine Leaching is Necessary
Sodium cyanide is commonly used by the mining industry to leach gold from ore.
This is carried out via heap leaching and tank leaching.
In heap leaching, cyanide is sprayed over crushed ore, dissolving the gold onto collection pads. This process is repeated until all the gold has been recovered.
In-tank leaching, gold ore is mixed with cyanide in large tanks in a more controlled way than in heap leaching. However, the left-over waste is usually stored in tailings ponds, behind large, engineered dam and dyke facilities.
These tailings can fail, often without any warning. When they fail, they cause catastrophic environmental pollution and devastation, such as that which occurred in 2014, at Mount Polley, a Canadian gold and copper mine, situated in British Columbia.
Twenty-four million cubic meters of mine waste contaminated nearby lakes and rivers, poisoning aquatic life and eco-systems. The disaster is considered to be the biggest mining disaster in Canadian history.
Recent studies reveal lake waters still have elevated copper and fine sediment today and could be making their way into the food chain.
In addition to cyanide leaching being environmentally hazardous, MPS suggests cyanide leaching is not an attractive economic investment as it uses such vast amounts of non-renewable cyanide, whereas glycine is both non-toxic and recoverable.
Some gold mining projects also prohibit cyanide use.
In 2010, the European Parliament banned cyanide technologies altogether within the European Union for having a catastrophic and irreversible effect on human health, environment and biodiversity.
Glycine also facilitates the opportunity to leach from stranded copper oxide deposits, where its use can be more selective and is not dependent on high acid use.
Curtin University Glycine Technology Improves Leaching Rates for Gold Ore
Curtin University, which first developed glycine technology and then partnered with MPS to commercialize it, claims it can significantly increase leaching rates for gold ore using potassium permanganate.
Professor Eksteen at the University explains that potassium permanganate, when used in the glycine process, significantly reduces the need for high temperatures, high glycine concentrations, and oxygen, delivering the most successful results to improve the glycine leaching process even further.
Researchers leached 85.1% of gold from an ore deposit, using potassium permanganate, at ambient temperature, similar to that achieved with cyanide.
It also eliminates the risks associated with transporting and handling cyanide, as well as environmental accidents.
This suggests glycine technology has the potential to revolutionize the gold mining industry.
Glycat™️ Technology Improves Gold Leaching Rates with Lower Cyanide Concentrations
In addition to standard glycine leaching, which uses alternative catalysts, MPS has developed a secondary technology called Glycat™️, which uses glycine and small amounts of cyanide.
The purpose of still using cyanide is that Glycat™️ technology has been developed to not only reduce the need for cyanide by up to 87.5%, but to also improve gold recovery from ores that contain nuisance copper.
This means problematic ores, with elevated soluble copper can still be leached much faster and more economically than cyanide alone, with 100% copper recovery.
Alternative catalysts to cyanide are still available when required, making sustainable mineral extraction either wholly or at least partially viable using the glycine leaching process that best suits the situation.
This makes glycine leaching very versatile, which should make it appealing to the mining industry in the very near future.
References and Further Reading
Cyanide use in gold mining (2019) in Earthworks online https://earthworks.org/issues/cyanide/
Glycine mitigates fertilizer requirements of agricultural crops: case study with cucumber as a high fertilizer demanding crop (10.15.2020) Handoskt.M.R, Jari.S.K, Shooshtari.F.Z, Souri. M.K in SpringerOpen (Journal) https://chembioagro.springeropen.com/articles/10.1186/s40538-020-00185-5
Soil applied glycine betaine with Arbuscular mycorrhizal funghi reduces chromium uptake and ameliorates chromium toxicity by suppressing the oxidative stress in three genetically different Sorghum (sorghum bicolor.L) cultivars (07.14.2021) Kumar.P in BMC Plant Biology online https://bmcplantbiol.biomedcentral.com/articles/10.1186/s12870-021-03113-3
Top 9 Benefits and Uses of Glycine (12.12.2018) Van de Walle.G in healthline online https://www.healthline.com/nutrition/glycine
Which Countries and U.S states are banning Roundup? (02.10.2021) in Carlson Law Firm online https://www.carlsonattorneys.com/news-and-update/banning-roundup
Mount Polley Independent Expert Investigation and Review Report: The Panel report ‘What did we find?’ video on YouTube 01.30.2015 https://www.mountpolleyreviewpanel.ca
Contamination from Mount Polley spill continues to affect waterways, study finds, in CBC News https://www.cbc.ca/news/canada/british-columbia/mount-polley-2020-study-1.5685631
Ban on use of cyanide mining technologies (03.15.2011) (pp.1-4) in Official Journal of the European Union https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:C:2011:081E:0074:0077:EN:PDF
Curtin University ups glycine gold leaching rates with permanganate agent (01.08.2021) Gleeson.D in International Mining, online, https://im-mining.com/2021/01/08/curtin-university-ups-glycine-gold-leaching-rates-permanganate-agent/
Gold Leaching with nuisance copper Glycat™️ in Mining and Process Solutions (pdf) online https://www.mpsinnovation.com.au/wp-content/uploads/GlyLeach-1-pager-PDF.pdf
The Glyleach process in Mining and Process Solutions (2021) https://www.mpsinnovation.com.au/technology/
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