Every year, millions of tons of electronic waste accumulate, posing environmental and economic problems. An American research team is proposing an innovative solution by extracting gold from this waste and then transforming it into a catalyst, thus converting carbon dioxide into organic materials. This approach could offer an answer to the sustainable management of electronic waste.
A research team led by Cornell University (USA) has developed a method to extract gold from electronic waste. Subsequently, the recovered precious metal serves as a catalyst for the conversion of carbon dioxide (CO2), a greenhouse gas, into organic materials. This innovation could provide a sustainable use for the approximately 50 million tons of electronic waste that are thrown away each year, of which only 20% is recycled, according to Amin Zadehnazari, a postdoctoral researcher in the laboratory of Alireza Abbaspourrad, associate professor of food chemistry and ingredient technology at the Faculty of Agriculture and Life Sciences.
Covalent organic frameworks for gold capture
Amin Zadehnazari synthesized two types of vinyl-bonded covalent organic frameworks (VCOFs) to remove gold ions and nanoparticles from circuit boards in used electronic devices. One of its VCOFs demonstrated an ability to selectively capture 99.9% of gold, with very low retention of other metals, such as nickel and copper, present in the devices.
«We can then use the gold-loaded COFs to convert the CO2 into useful chemicals», indicated the researcher. “By transforming CO2 into value-added materials, we not only reduce waste management requirements, but also provide both environmental and practical benefits. It’s a win-win situation for the environment.»
The publication accepted in Nature Communications highlights the possibilities of repurposing e-waste as a potential gold mine. It is estimated that a ton of electronic waste contains at least ten times more gold than a ton of gold ore. With a projected 80 million tons of electronic waste by 2030, it is becoming increasingly imperative to find ways to recover this precious metal.
Environmentally friendly recovery methods
Traditional methods of recovering gold from e-waste involve the use of harmful chemicals, such as cyanide, which pose environmental risks. Zadehnazari’s method is notable for its absence of dangerous chemicals, using chemical adsorption – the adhesion of particles to a surface.
Covalent organic frameworks (COFs) are porous crystalline materials, known for their multiple potential applications, including chemical sensing and energy storage. Zadehnazari synthesized two VCOFs, using tetrathiafulvalene (TTF) and tetraphenylethylene (TPE) as building blocks. TTF-COF showed superior gold adsorption due to its richness in sulfur, for which gold has a natural affinity. In addition to its high adsorption capacity, TTF-COF withstood 16 washes and reuses, with little loss in adsorption efficiency.
Under ambient CO2 pressure at 50 degrees Celsius (122 degrees Fahrenheit), gold-loaded COF efficiently converts CO2 to organic matter through carboxylation.
Abbaspourrad points out that other methods of recovering gold and other precious metals from e-waste are generally not as selective as the one proposed by Zadehnazari, leading to impurities. “Knowing the amount of gold and other precious metals present in these types of electronic devices, being able to recover them in a way that selectively captures the desired metal – in this case, gold – is very important,» he mentioned.
Illustration caption: pile of electronic cards
Article : « Recycling e-waste into gold-loaded covalent organic framework catalysts for terminal alkyne carboxylation » – DOI : s41467-024-55156-3
Source: Cornell University
