🌱 How much gold can be recovered from e-waste?
E-waste “often contain[s] large amounts of gold and other heavy metals”. According to the Business Insider, [t]he materials in electronics that are thrown away over the course of a year are worth an estimated $60 billion”. Alone from one ton of disposed printed circuit boards, it is possible to recover “gold worth around $12,000, copper worth around $2,000 and silver worth $1,400”. Yet, the valuable materials found in e-waste are not particularly easy to collect.
🌱 Can old milk be used for recycling gold from e-waste?
It is possible to make a type of gel called “aerogel” from old milk. Researchers at the ETH Zurich recently “developed a way to recover gold from e-waste by using a milk-derived aerogel”. The aerogel can be used to “extract highly pure gold nuggets from discarded computer motherboards”. In laboratory conditions, the aerogel could absorb 93% of the gold from a mixed solution.
🌱 How does the process work?
The researchers at the ETH Zurich “started with whey protein, a byproduct of the cheesemaking industry”. They made a cheap aerogel out of this. The researchers then “placed whey protein into an acidic solution and heated it, which unraveled the proteins from tiny balls into strands”. Next, “they freeze-dried the solution, forming a lightweight puck with high porosity”. The resulting aerogel has a low-density and a high surface area. When the aerogel was added to “dissolved computer motherboards in aqua regia, a mix of nitric acid and hydrochloric acid”, the “[g]old ions from the mixture settled on the surface of the aerogel and were reduced, forming metallic gold”.
🌱 Is the new process more efficient?
Notably, “[e]ach gram of aerogel snatched 190 mg of gold” from the “dissolved computer motherboards in aqua regia”. In comparison with aerogel, “[e]ach gram of activated carbon only adsorbed about 60 mg of gold from [the] e-waste mixture”. This means that the aerogel method is more efficient than the more typically used adsorption method of using activated carbon. As large amounts of energy are needed to produce activated carbon, “recovering the same amount of gold using activated carbon had a higher environmental impact in a life cycle analysis”. The researchers now plan to investigate other proteins that can be created from food waste, such as keratin and tofu. They hope this “could potentially help with other needs, such as the recycling of rare earth metals”, and provide an opportunity to create new value from food waste.
Read more about gold recycling from e-waste here:
- https://greekreporter.com/2024/02/09/how-extract-gold-from-e-waste-old-milk/
- https://onlinelibrary.wiley.com/doi/10.1002/adma.202310642
- https://hackaday.com/2024/02/20/gold-recovery-from-e-waste-with-food-waste-amyloid-aerogels/
- https://www.elektronikpraxis.de/das-gold-liegt-im-muell-a-1a6084f0c30538fc719d6e8f2af4f234/