Researchers at Flinders University revealed a method to extract gold from both ore and electronic waste using a mix of saltwater, ultraviolet (UV) light, and a recyclable polymer. This technique offers a cleaner and safer alternative to traditional gold extraction methods, which often rely on toxic chemicals like cyanide and mercury, according to SciTechDaily.
In 2022, global electronic waste (e-waste) reached 62 million tonnes, enough to fill more than 1.5 million garbage trucks. Only 22.3 percent of this e-waste was recycled. Discarded electronic devices not only contribute to environmental pollution but also result in the loss of valuable materials such as gold, silver, and rare earth elements.
An interdisciplinary team of scientists and engineers, led by Maximilian Mann from Flinders University, developed a new technique to recover gold from e-waste and ore. By leveraging expertise in green chemistry, engineering, and physics, the team crafted a method that reduces the health and environmental impacts associated with traditional gold mining.
"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," said Lynn Lisboa, a postdoctoral research associate at Flinders University and one of the lead authors of the study, as reported by SciTechDaily.
The procedure unfolds in three key stages. In the first step, trichloroisocyanuric acid (TCCA), a common disinfectant used in water treatment and pool cleaning, is activated with a halide catalyst in saltwater to dissolve gold from the ore or electronic waste. This process effectively converts solid gold into a soluble form without the use of toxic chemicals.
In the second step, a sulfur-rich polysulfide polymer is introduced to the solution. This polymer selectively binds to the dissolved gold, separating it from other metals and materials present in the mixture. The polymer can extract gold even from solutions containing a mix of metals, showing its selectivity and efficiency.
The final step involves recovering the gold-bound polymer by either pyrolyzing (heating) or depolymerizing it. This allows for the retrieval of high-purity gold while enabling the polymer to revert to its monomer form, ready to be reused. This circular recovery process promotes responsible e-waste recycling and minimizes environmental impact.
Traditional gold extraction methods often involve the use of cyanide and mercury, which are highly toxic and pose risks to ecosystems and human health. Artisanal and small-scale mining operations contribute to 37 percent of global mercury pollution, approximately 838 tonnes annually. By eliminating the need for these hazardous chemicals, the new method developed by the Flinders University team offers a safer and more sustainable alternative.
The team tested their approach on electronic waste, mixed-metal scraps, and ore concentrates, demonstrating its versatility and potential for widespread application. The method transforms electronic waste and ore into valuable resources while protecting the environment, offering applications in mining and small-scale e-waste recycling.
Mann emphasized the importance of interdisciplinary collaborations in addressing global challenges. "This paper shows that interdisciplinary collaborations are needed to address the world's big problems managing the growing stockpiles of e-waste," he said.
The researchers plan to collaborate with industry partners, governments, and non-governmental organizations to test their method in small-scale mining operations. They aim to support small-scale miners who often rely on mercury due to financial constraints and lack of access to safer alternatives.
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