TWENTY FIRST CENTURY ALCHEMY
Jackpot! Gold from e-waste opens a rich vein for miners and the environment
New method published in Nature Sustainability
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Gold recovered from electronic waste in the Flinders University study.
view moreCredit: Flinders University
An interdisciplinary team of experts in green chemistry, engineering and physics at Flinders University in Australia has developed a safer and more sustainable approach to extract and recover gold from ore and electronic waste.
Explained in the leading journal Nature Sustainability, the gold-extraction technique promises to reduce levels of toxic waste from mining and shows that high purity gold can be recovered from recycling valuable components in printed circuit boards in discarded computers.
The project team, led by Matthew Flinders Professor Justin Chalker, applied this integrated method for high-yield gold extraction from many sources – even recovering trace gold found in scientific waste streams.
The progress toward safer and more sustainable gold recovery was demonstrated for electronic waste, mixed-metal waste, and ore concentrates.
“The study featured many innovations including a new and recyclable leaching reagent derived from a compound used to disinfect water,” says Professor of Chemistry Justin Chalker, who leads the Chalker Lab at Flinders University’s College of Science and Engineering.
“The team also developed an entirely new way to make the polymer sorbent, or the material that binds the gold after extraction into water, using light to initiate the key reaction.”
Extensive investigation into the mechanisms, scope and limitations of the methods are reported in the new study, and the team now plans to work with mining and e-waste recycling operations to trial the method on a larger scale.
“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,” says Professor Chalker.
The new process uses a low-cost and benign compound to extract the gold. This reagent (trichloroisocyanuric acid) is widely used in water sanitation and disinfection. When activated by salt water, the reagent can dissolve gold.
Next, the gold can be selectively bound to a novel sulfur-rich polymer developed by the Flinders team. The selectivity of the polymer allows gold recovery even in highly complex mixtures.
The gold can then be recovered by triggering the polymer to “un-make” itself and convert back to monomer. This allows the gold to be recovered and the polymer to be recycled and re-used.
Global demand for gold is driven by its high economic and monetary value but is also a vital element in electronics, medicine, aerospace technologies and other products and industries. However, mining the previous metal can involve the use of highly toxic substances such as cyanide and mercury for gold extraction – and other negative environmental impacts on water, air and land including CO2 emissions and deforestation.
The aim of the Flinders-led project was to provide alternative methods that are safer than mercury or cyanide in gold extraction and recovery.
The team also collaborated with experts in the US and Peru to validate the method on ore, in an effort to support small-scale mines that otherwise rely on toxic mercury to amalgamate gold.
Gold mining typically uses highly toxic cyanide to extract gold from ore, with risks to the wildlife and the broader environment if it is not contained properly. Artisanal and small-scale gold mines still use mercury to amalgamate gold. Unfortunately, the use of mercury in gold mining is one of the largest sources of mercury pollution on Earth.
Professor Chalker says interdisciplinary research collaborations with industry and environmental groups will help to address highly complex problems that support the economy and the environment.
“We are especially grateful to our engineering, mining, and philanthropic partners for supporting translation of laboratory discoveries to larger scale demonstrations of the gold recovery techniques.”
Lead authors of the major new study – Flinders University postdoctoral research associates Dr Max Mann, Dr Thomas Nicholls, Dr Harshal Patel and Dr Lynn Lisboa – extensively tested the new technique on piles of electronic waste, with the aim of finding more sustainable, circular economy solutions to make better use of ever-more-scarce resources in the world. Many components of electronic waste, such as CPU units and RAM cards, contain valuable metals such as gold and copper.
Dr Mann says: “This paper shows that interdisciplinary collaborations are needed to address the world's big problems managing the growing stockpiles of e-waste.”
ARC DECRA Fellow Dr Nicholls, adds: “The newly developed gold sorbent is made using a sustainable approach in which UV light is used to make the sulfur-rich polymer. Then, recycling the polymer after the gold has been recovered further increases the green credentials of this method.”
Dr Patel says: “We dived into a mound of e-waste and climbed out with a block of gold! I hope this research inspires impactful solutions to pressing global challenges.”
“With the ever-growing technological and societal demand for gold, it is increasingly important to develop safe and versatile methods to purify gold from varying sources," Dr Lisboa concludes.
The article, Sustainable gold extraction from ore and electronic waste (2025) by Maximilian Mann, Thomas P Nicholls, Harshal D Patel, Lynn S Lisboa, Jasmine MM Pople, Le Nhan Pham, Max JH Worthington, Matthew R Smith, Yanting Yin, Gunther G Andersson, Christopher T Gibson, Louisa J Esdaile, Claire E Lenehan, Michelle L Coote, Zhongfan Jia and Justin M Chalker has been published in Nature Sustainability. DOI: 10.1038/s41893-025-01586-w
https://doi.org/10.1038/s41893-025-01586-w
Photos: Nature Sustainability Press Release - Dropbox
Fast Facts:
Electronic waste (e-waste) is one of the fastest growing solid waste streams in the world. In 2022, an estimated 62 million tonnes of e-waste was produced globally. Only 22.3% was documented as formally collected and recycled.
E-waste is considered hazardous waste as it contains toxic materials and can produce toxic chemicals when recycled inappropriately. Many of these toxic materials are known or suspected to cause harm to human health, and several are included in the 10 chemicals of public health concern, including dioxins, lead and mercury. Inferior recycling of e-waste is a threat to public health and safety.
Miners use mercury, which binds to gold particles in ores, to create what are known as amalgams. These are then heated to evaporate the mercury, leaving behind gold but releasing toxic vapours. Studies indicate that up to 33% of artisanal miners suffer from moderate metallic mercury vapor intoxication.
Between 10 million and 20 million miners in more than 70 countries work in artisanal and small-scale gold mining, including up to 5 million women and children. These operations, which are often unregulated and unsafe, generate 37% of global mercury pollution (838 tonnes a year) – more than any other sector.
Most informal sites lack the funding and training needed to transition towards mercury-free mining. Despite accounting for 20% of the global gold supply and generating approximately US$30 billion annually, artisanal miners typically sell gold at around 70% of its global market value. Additionally, with many gold mines located in rural and remote areas, miners seeking loans are often restricted to predatory interest rates from illegal sources, pushing demand for mercury.
Journal
Nature Sustainability
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Sustainable gold extraction from ore and electronic waste
Article Publication Date
26-Jun-2025
COI Statement
J.M.C. and M.M. are inventors on a patent application on gold leaching and recovery (US20220205061). J.M.C and M.J.H.W. are inventors on a granted patent on polymer sorbents used in this study (US patent 11,167,263). Both patents are owned by Flinder
Addressing challenges for safer and more sustainable gold extraction. A: Gold mining relies on the use of toxic substances such as cyanide in formal mining and mercury in artisanal and small-scale gold mining. Recycling gold from electronic waste (‘urban mining’) is complicated by the complex composition of printed circuit boards and other components of obsolete electronic devices. Credit: a. (left), US Consulate General b, An integrated approach to mercury- and cyanide-free gold recovery from both primary and secondary gold sources reported in this study.
Gold mining relies on the use of toxic substances such as cyanide in formal mining and mercury in artisanal and small-scale gold mining.
Many components of electronic waste, such as computer processing units and RAM cards, contain valuable metals such as gold and copper.
A Pitt study has identified a protein that can separate critical metals from electronic waste
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Meng Wang has used ferritin to successfully recover critical metals from e-waste from a liquid solution.
view moreCredit: Paul Kovach/University of Pittsburgh
When phones or computers are recycled, small amounts of important materials get discarded. Those minute amounts of cobalt, nickel and lithium add up quickly, and separating and recovering these “critical materials” for reuse is a dirty, energy intensive job.
New Pitt research has found there are proteins that may be able to do the same job without the use of harsh chemicals and rigorous energy demands. Meng Wang, an assistant professor of environmental and civil engineering in the Swanson School of Engineering, has used ferritin to successfully recover some of these same critical metals from a liquid solution.
In 2019, the United States generated nearly 7 million tons of electronics, but only 15% of their critical materials are recovered. “That’s lower than the world average of 17%,” Wang said, citing research published in 2020 and 2021.
And those unrecovered metals are worth about $7 billion. “If they can be recycled, the critical metals can be used to complement the supply chain,” Wang said.
Wang’s lab focuses on using proteins for environmental remediation and, generally, to aid in sustainability efforts. He turned to ferritin, a protein with porous walls on its surface which leads to a hollow inside. Proteins like this are called nanocages because of their ability to trap smaller materials inside.
Less than 10 years ago, researchers started to use a different protein, lanmodulin (LanM), to trap rare earth materials. “We were inspired by this study,” Wang said.
He and his team were already working with ferritin when he saw a call for a biomining tool — a microorganism that can be used to extract metals from rocks or other materials. They turned to the protein to see if it might work similarly to LanM.
The team had reason to be hopeful: The inside of ferritin nanocages carry dense negative charges. Earlier studies had shown that ferritin nanocages could sequester metals, so Wang decided to find out if the protein was in any way selective about which metals it sequestered and which it left undisturbed.
Most of the critical metals in a lithium-ion battery are in its cathode, usually a solid, and its electrolyte, which is liquid. To recover them, the cathode metals are leached into a liquid solution. The result is a liquid mixture of cobalt, nickel and lithium ions, instead of a relatively simple solution containing one metal, which would be easier to recover.
“That’s why selectivity is key,” Wang said. “You want the protein to selectively separate or recover the metals.”
The team ran several experiments to test ferritin’s selectivity. They added it to a solution with cobalt ions and found that ferritin was not only selective for the metal, but had such strong affinity that the concentration of cobalt inside the nanocages was thousands of times higher than that left in the solution. This affinity created hot spots of metal ions which precipitated out of the liquid and sank to the bottom, where they were easily recovered.
Ferritin also had a strong affinity for nickel ions, although not quite as strong as it had for cobalt, but had barely any affinity for lithium — which was good news.
“Ultimately, we want to recover metals like cobalt and nickel through precipitation,” Wang said. “Then we leave the lithium in the solution. If you get a relatively pure lithium solution, that's much easier for downstream processing.
This process also has the benefit of taking place in benign, neutral conditions. Current practices, such as solvent extraction, require using harsh chemicals that require careful disposal.
The next step for Wang is to investigate why ferritin has an affinity for some metals, but not others.
Part of the reason for the discrepancy, Wang said, is to do with charge. The interior of the nanocages have strong negative charges, while the three metals are positive, but the cobalt and nickel ions have a stronger positive charge (+2) than lithium (+1).
That can’t be the whole story, though. “Even though cobalt and nickel are both +2, we still observed a significant adsorption difference between the two,” Wang said. “That part we don’t yet understand.”
The team hopes a better understanding of ferritin’s selectivity will allow them to refine the nanocages, engineering one that selects cobalt only and one that selects nickel.
“So, you’d have three tanks,” Wang said of his long-term goal. “The first tank uses one ferritin to recover nickel, the second tank uses a second ferritin to recover cobalt, and then we have a lithium solution for downstream processing.”
Journal
Environmental Science & Technology Letters
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Ferritin Protein Nanocages for Selective Separation and Recovery of Critical Metals
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