Gold is a valuable raw material for many branches of industry, but its sources are limited. Engineers and chemists have now developed a new technology to win high -purity gold from ores and from electronic waste. The method uses non -toxic chemicals, which are largely recycled. This gold extraction technology is therefore more sustainable and safer than conventional methods and could replace them in the future. That would reduce the amount of toxic waste from mining and help to recycle gold from discarded computers.
Our world is full of electrical appliances and there are more and more. This also increases the global mountain of electronic waste. In 2022, an estimated 62 million tons of this special waste were produced, but only 22.3 percent of which were recycled. This is a problem for the environment and human health. Because with improper recycling and on dumps, toxic chemicals can be released from the electronic waste, including dioxins, lead and mercury. The recycling of E-Watste would also be worthwhile in order to be able to recycle the gold it contains. So far, however, there has been no sustainable techniques for this “urban mining”.
The same applies to gold extraction from ores. Bergers often use mercury that binds to the gold particles in ores and forms amalgame from them. These are then heated to evaporate the mercury and get rid of it. What remains is the pure gold-and mercury damps that are poisonous for the miners and the environment. This is a problem, especially in small, unregulated mining companies. Instead, larger mining companies use highly toxic zyanide leaves to win gold from ore. In the case of correct use, this harms the miners less than mercury, but is associated with risks to animals and the environment. In addition, gold mining often goes hand in hand with deforestation and high CO2 emissions. The demand for gold is high worldwide- because of its high currency value and because the precious metal is an important raw material for electronics, aerospace technology, medicine and other branches of industry.
Gentle gold extraction
A research team around Maximilian Mann from Flinders University in Australia has now developed a new method for secure and more sustainable gold extraction from ores and electronic waste, which does not require any cyanide and mercury. Trichlorisocyanuric acid (TCCA) is used – an inexpensive and non -toxic chemical that is also often used in water treatment. Man and his colleagues use this acid in combination with salt water to solve gold from ores or electronic waste. This took a few hours and resulted in a liquid that, in addition to gold, also contained other metals such as copper and zinc from the scrap components.
For this solution, the researchers gave a newly developed sulfuric polymer that selectively binds only the dissolved gold. The resulting polysulfide gold connection can be easily separated from the remaining substances by a filter. This enables gol to extraction from highly complex mixtures, as the researchers explain. In order to get the pure gold, they finally brought the polymer to dismantle themselves and convert them back into monomers. The structure of the polymer is stimulated by UV light, the dismantling by heat. Through subsequent distillation, the pure gold can be obtained and the polymer can be reused at least in parts. The trichlorisocyanuric acid as a leaching reagent and the water used can also be largely recycled, as the team explains.
Mann and his colleagues tested their new technology in the laboratory of grinding electronic waste, including CPU units and RAM cards, i.e. processors and working stores from old computers. “We dipped into a mountain of electronic waste and climbed out with a gold block,” reports co-author Harshal Patel from Flinders University. Such electric components contain between 200 and 900 milligrams of gold per kilogram of scrap – more than in ores. The team solved 3.9 grams of gold from 30 grams of concentrated e-scrap powder. In addition, the team demonstrated that the method can effectively be used for gold extraction from small arch chunks and metal waste from chemical laboratories: they received 59 milligrams of gold from 200 grams of ore concentrate and 6.5 grams of gold from 7.5 liters of chemical waste.
Method is to be further optimized
The team now wants to work with mining and electronic red recycling companies as well as environmental groups in order to test the technology on a larger scale and under economic conditions. “The aim is to offer effective methods of golf extraction that support the diverse uses of gold and at the same time reduce the effects on the environment and human health,” says senior author Justin Chalker from Flinders University. In the future, the technology could be a sustainable solution for the circular economy, so that the tight gold resources can be better used.
Source: Maximilian Mann (Flinders University) et al.; Nature Sustainability, DOI: 10.1038/S41893-025-01586-W
