Extracting Gold Sustainably from Ore and E‑Waste
Gold’s role in technology, aerospace and finance is indisputable, but extracting it comes at a high environmental price. Traditional mining relies heavily on cyanide and mercury, chemicals infamous for pollution and health risks.
A breakthrough study in Nature Sustainability offers a solution: a novel method that uses trichloroisocyanuric acid and a reusable sulfur polymer to extract gold cleanly from both ore and electronic waste.
TCCA Leaching Replaces Cyanide and Mercury
At the heart of the innovation lies trichloroisocyanuric acid (TCCA), a disinfectant chemical commonly used in water treatment. Activated with a halide catalyst—typically sodium chloride or bromide—it oxidises gold effectively, dissolving it from ore and circuit boards without resorting to cyanide or mercury.
The significance is major. By eliminating toxic reagents used in over 80% of current gold leaching, this approach addresses environmental, regulatory and health concerns in both industrial and artisanal mining sectors.
Polysulfide Polymer Sorbents
Once the gold is in solution, the next trick is capturing it. The Flinders research team developed a polysulfide polymer sorbent that binds gold ions selectively—even in complex mixtures with other metals. These sorbents are redox active: they actually reduce the gold salt to the metal, pulling it out of solution through chemical affinity.
Even better? The polymer can be depolymerised or pyrolyzed to release gold with over 99% purity, and then recycled for reuse. It’s a closed-loop system that combines recovery with sustainability.
Demonstrated Efficacy Across Sources
Tests confirmed the method works on:
- Traditional gold ore
- Printed circuit boards and mixed e‑waste
- Lab and industrial metal‑containing waste
The high extraction yield and purity have been demonstrated across all three, forming the basis for scaling up with recycling plants and mining partners.
In the words of Professor Justin Chalker of Flinders University in Austalia: “The aim is to provide effective gold recovery methods that support the many uses of gold, while lessening the impact on the environment and human health.”
For Mining and E‑Waste Recycling this eliminates cyanide and mercury use, and drastically cuts toxic waste production, offering a cost-effective, scalable solution.
For Artisanal and Small-Scale Miners mercury amalgamation remains prevalent in small-scale mining, responsible for up to 40% of global mercury emissions. A mercury‑free process helps protect communities and ecosystems from exposure and contamination without sacrificing yield.
For the Circular Economy with global electronic waste reaching 62 million tonnes in 2022—and projected to hit over 80 million tonnes by 2030—every old phone or circuit board represents both a hazard and a resource. This method transforms an environmental burden into a profit-generating opportunity, aligning perfectly with urban-mining and circular economy goals.
How the Process Works
- Leaching – Apply TCCA in salt-activated solution to oxidatively dissolve gold.
- Binding – Introduce polysulfide polymer sorbent that selectively adsorbs gold ions and reduces them to metal.
- Recovery – Release gold at >99% purity by heating (pyrolysis) or depolymerising the polymer; recycle the polymer monomer for repeated use.
Broader Context and Industry Implications
- Growing regulatory pressure on cyanide and mercury use
- Heightened investor interest in ESG-compliant practices
- Demand for sustainable technology inputs requires gold, which is crucial in microelectronics, aerospace, medical devices and materials sciences
Governments and corporations adopting this technology could set a new industry standard, reducing carbon footprints and hazardous waste while extracting economic value from e‑waste.
Sustainability at Scale
The research team is now engaged with mining and e‑waste recycling operations to pilot the technique at commercial scale. Thanks to the polymer’s recyclability and low reagent cost, this method is well‑poised to achieve industrial feasibility without hefty capital expenditure.
If scaled effectively, it could shift the gold supply chain to a circular, non‑toxic model, safeguarding both natural ecosystems and human communities.
A Greener Gold Era Beckons
This new method marks a turning point in sustainable construction and resource industries. With high purity gold recovery from primary and secondary sources, all without mercury or cyanide, the approach reports a significant leap forward.
It fits right into corporate ESG strategies, supports policy moves to ban hazardous substances, and may even attract investment from green-tech funds and circular economy champions.
Given mounting global pressure to clean up mining practices and reclaim value from e‑waste, this innovation could become a cornerstone for next‑generation gold recovery.
