Gold and certain other precious metals are key ingredients in computer chips, including those used in consumer electronics such as smart phones. But it can be difficult to recover and recycle those metals from electronic waste. Japanese researchers have found that a pigment widely used by artists called Prussian blue can extract gold and platinum-group metals from e-waste much more efficiently than conventional bio-based absorbents, according to a recent paper published in the journal Scientific Reports.
“The amount of gold contained in one ton of mobile phones is 300-400 grams, which is much higher by 10-80 times than that in one ton of natural ore,” the authors wrote. “The other elements have a similar situation. Consequently, the recovery of those precious elements from e-wastes is much more effective and efficient when compared to their collections from natural ore.”
Prussian blue is the first modern synthetic pigment. Granted, there was once a pigment known as Egyptian blue used in ancient Egypt for millennia; the Romans called it caeruleum. But after the Roman empire collapsed, the pigment wasn’t used much, and eventually the secret to how it was made was lost. (Scientists have since figured out how to recreate the process.) So before Prussian blue was discovered, painters had to use indigo dye, smalt, or the pricey ultramarine made from lapis lazuli for deep blue hues.