Turning garbage into gold sounds like alchemy, not science. But researchers at ETH Zurich have demonstrated an efficient, sustainable method to extract gold nuggets from common electronic waste.
The process uses not one, but two waste products. Gold is coaxed from e-waste with a protein amyloid nanofibril (AF) aerogel derived from whey, a by-product of cheese making. The aerogel acts like a gold sponge, and the researchers were able to extract a nearly pure, 22-karat, gold nugget weighing almost half a gram from 20 discarded computer motherboards.
“We knew protein sponges have a very high absorption capacity for gold, but our surprise was to find so much gold [relative to other metals],” said Raffaele Mezzenga, a professor at ETH Zurich. “When we saw the purity of the gold was so high, that was a good surprise, of course.”
From Garbage to Gold
Extracting gold from e-waste is desirable for the obvious reason: Gold is valuable. Prices vary but as of press time, 22-karat gold is valued at roughly US $60 per gram. However, extracting that gold requires a process that can separate it from the many other metals and substances found in e-waste.
The researchers were able to extract about half a gram of nearly pure gold from old motherboards using their process.Alan Kovacevic/ETH Zurich
Mezzenga and his fellow researchers were inspired by prior research using protein amyloid nanofibrils to purify water contaminated by heavy metals like lead, palladium, and mercury. Gold, another heavy metal, can also be absorbed by the protein.
“In the past we have already used this very same protein to purify water polluted by heavy metal, arsenic, radioactive compounds, and so on,” said Mezzenga. “So we were preparing this [AF] aerogel and sought to see whether we can now extract gold from e-waste.”
“We are positive we will be able to extract platinum, palladium, silver, and exotic rare earth metals.” —Raffaele Mezzenga, ETH Zurich
The results were even more successful than the researchers hoped. Gold was absorbed, as expected, but other metals present were absorbed in very small quantities, which allowed the researchers to extract a gold nugget with a high level of purity. They estimate the value of the gold produced at nearly 50 times as great as the cost of extracting it.
Before you buy a bucket of whey powder from your local gym and throw it on an old motherboard, wait a minute. The process begins with cleaning the motherboard and removing unwanted components like capacitors and plastic cladding. Then, the motherboard is smashed to bits and dissolved in a highly acidic aqua regia bath, which is filtered to remove debris. The AF aerogel is placed in this motherboard soup, which is then dried, combusted, mixed with borax, melted, and finally cooled to form a lump of useful gold.
This diagram shows how gold ions adhere to a sponge of protein fibrils, in order to separate the gold from other elements.ETH Zurich/Advanced Materials
That might sound complex,…
Read full article: Researchers Turn Electronic Garbage Into Gold
The post “Researchers Turn Electronic Garbage Into Gold” by Matthew S. Smith was published on 03/14/2024 by spectrum.ieee.org