CYANIDE CONTAINMENT
IN GOLD MINES:
ENSURING ENVIRONMENTAL SAFETY
IMPROVING THE RISK-REWARD RATIO
OF GOLD CYANIDATION
When you think of chemical hazards, you probably think of cyanide. It’s a notorious poison that’s become synonymous with toxicity, but its utility extends far beyond its role in Hollywood and geopolitics. Cyanide and cyanide-containing compounds are used extensively in industrial applications, such as in the manufacturing of textiles and plastics, or in traditional technologies used to develop photographs. One of cyanide’s most common uses is in metallurgy, where cyanide salts are used for electroplating, metal cleaning, and extracting gold from ore. In fact, gold cyanidation, or cyanide leaching – the technical terms for extracting gold from ore using cyanide – has been the most common and well-established process of gold extraction since as early as the 1970s. However, the widespread use of such an acutely dangerous substance has remained quite controversial, and requires robust safety measures to minimize the risk of contamination. To improve the risk-reward ratio of gold cyanidation, polyurea coatings can be used for comprehensive cyanide containment, preventing cyanide solutions from leaking into the ground or surrounding areas to protect both human health and the environment.
WHY IS CYANIDE USED IN GOLD MINNG?
When we say “cyanide,” we refer to one of many different compounds that contain a cyanide functional group, consisting of a carbon (C) atom attached to a nitrogen (N) atom with a triple bond (C≡N). Cyanide can react with many metals, which sees it used to separate precious metals like gold from ore. The cyanide compound most often used for gold leaching is sodium cyanide (NaCN), applied to one of two common types of leaching: heap leaching, and tank leaching. Heap leaching uses cyanide solutions in open environments, where cyanide is sprayed over heaps of crushed ore that’s spread across large collection pads. The cyanide solution then passes over the heap, dissolving gold into solution that’s later collected by the collection pads, and this process is repeated until the ore is fully depleted. In contrast, tank leaching is performed in more controlled environments, typically in large tanks or vats. The process is fundamentally similar to heap leaching and benefits from a lower chance of spills or leaks, but produces a waste product known as tailings, a major type of hazardous waste that’s typically contained behind large dams known as tailings impoundments. When these dams fail, contamination can be every bit as extensive and severe as in heap leaching. So while the risks are clear and acute, cyanide leaching remains a key part of the mining industry, and extensive measures are taken to see its safe and continued use.
THE DANGERS OF CYANIDE IN GOLD MINING
As you might expect, there are many risks associated with using cyanide in gold mining, both to the environment as well as public health. Cyanide contamination has killed wildlife populations, destroyed agricultural land, and contaminated water supplies, all from some form of containment failure. A colorless gas, liquid, or crystal, cyanide prevents the body from receiving oxygen, preferentially binding to key molecules in aerobic cell metabolism, making it fast-acting and potentially lethal. Moreover, cyanide spills aren’t simple short-term events; cyanide spills can persist in the environment, and even when broken down in surface water, the resulting compounds can be similarly dangerous. Whether it be from retaining ponds, transport vehicles, dams, or industrial storage tanks, cyanide spills risk catastrophic health and safety risks to both humans and the environment.
POLYUREA FOR
CYANIDE CONTAINMENT:
If you’ve ever looked into industrial coatings, you’ve probably heard of polyurea. Since its development in the 1980s, polyurea has become one of the highest performing, all purpose protective coatings available on the market. It offers a unique combination of strength and flexibility, being durable enough to withstand forceful impacts and harsh abrasion, and malleable enough to adjust with shifting structures and changing environments. For cyanide containment, polyurea’s key advantage lies in its robust chemical resistance and lasting impermeability. In primary containment, polyurea is used to protect the inner surfaces of holding tanks, retainment ponds, and storage basins where pure and impregnated cyanide solutions are contained. This helps reinforce the structural integrity of containment materials and resist the corrosive effects of cyanide compounds. Likewise, polyurea is also used in secondary containment, being applied to floors, walls, and other surfaces to create a reliable secondary containment layer. Applied at both levels of containment, polyurea is the ultimate solution for ensuring environmental safety in gold cyanidation.
- Primary Containment Liners: Polyurea coatings act as a formidable barrier, seamlessly covering the inner surfaces of holding tanks, ponds, and basins where cyanide solutions are stored. The exceptional chemical resistance of polyurea prevents the corrosive effects of cyanide, maintaining the integrity of the containment system. Its quick curing time also allows for faster installation, reducing downtime during mine operations.
- Secondary Containment Systems: In addition to primary liners, secondary containment systems are essential to catch any potential leaks or spills. Polyurea coatings can be applied to floors, walls, and other surfaces to create a robust secondary containment layer. This ensures that even if the primary liners fail due to unforeseen circumstances, the surrounding environment remains protected.
FREQUENTLY ASKED QUESTIONS
Cyanide leaching, or gold cyanidation, is a safe and efficient process with proper management and control. Polyurea coatings can be used in both heap leaching and tank leaching to contain the spread of cyanide solutions and confine ore extraction within controlled environments. Polyurea is strong, flexible, and chemically resistant, making it the perfect containment solution for the mining industry.
In sufficiently large quantities or high concentrations, cyanide can be acutely dangerous to humans and other organisms. However, with careful and proactive risk mitigation, cyanide leaching can be both safe and cost-effective. It’s remained the most common type of gold extraction since the 1970s, and technologies like polyurea help see safer and more efficient mining operations.
Polyurea is not directly involved in the process of leaching gold ore, but instead serves to protect leaching solutions from spreading beyond the confines of the leaching operation. Without additional protection from robust technologies like polyurea, dangerous leaching compounds like sodium cyanide risk the health and safety of communities, ecosystems, and environments.
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CONSIDER PARTNERING WITH ARMORTHANE
Polyurea’s introduction to cyanide containment has drastically improved the safety and security of gold mining operations. If you want to leverage the strength and flexibility of high-quality polyurea formulations engineered for advanced containment, consider partnering with ArmorThane! Our goal is simple: to become your one-stop shop for everything polyurea and polyurethane, and this mission has guided our business for the last 35 years. As full-service operators, we formulate, manufacture, distribute, and apply our suite of polyurea and polyurethane products and services to a growing global network of customers and ArmorThane-certified professional applicators. Whether you need a quick fix or a common formulation for small projects, or seek expert guidance and full-suite capabilities to tackle even the biggest and most challenging coatings project, we’ve got you covered. Contact us today, and discover how we can help make your mining operations safe, easier, and more cost-effective.
ABOUT THE AUTHOR
TYLER GLECKLER
I am a chemist with a specialization in nanotechnology and applied materials chemistry. My work has focused on the characterization of optoelectronic materials, namely including semiconductor nanocrystals.
