快猫短视频

An aerogel made from old milk can extract highly pure gold nuggets from discarded computer motherboards.

Discarded electronics, known as e-waste, often contain large amounts of gold and other heavy metals. 快猫短视频s have come up with methods to recover the valuable metals, but these processes often rely on synthetic chemicals that can damage the environment.

at ETH Zurich in Switzerland and his colleagues have developed a way to recover gold from e-waste by using a milk-derived aerogel, a type of gel where the liquid component is replaced with gas.

鈥淚f you do an economic calculation, the margin is quite high because we start from a material [e-waste], which has no cost, and we start from a material [whey], which is very easy to process,鈥� says Mezzenga.

Mezzenga and his team took discarded whey, a by-product of strained milk, and extracted extremely long, nanoscopically thin protein fibres. They then added a chemical acid to link the fibres together, froze them and finally heated the resulting mass to form an aerogel.

Next, they placed the aerogel in a soup of computer motherboards, which they had stripped of all non-metal parts and then dissolved in a combination of hydrochloric and nitric acid. They found that the aerogel absorbed gold ions from the liquidised e-waste. After drying and burning the aerogel scaffolding, Mezzenga and his team recovered whole gold nuggets of more than 90 per cent purity, equivalent to 22 carats, with most of the remainder of the nugget consisting of copper.

Using one waste product to extract valuable material from another waste product is sustainable, says at the University of Edinburgh in the UK, but it still isn鈥檛 as effective as other existing chemical extraction techniques. And because the whey aerogel also absorbs other metals, like copper, it makes the gold less usable for some applications, he says.

Though people might be tempted to extract gold from old electronics themselves, this would be unwise, says Love: dissolving computer motherboards in powerful acids is dangerous and can give off highly toxic fumes.