Your favorite Picasso dye may one day recycle minerals from your cell phone

A new method is helping to recover gold from e-waste at a higher rate than can be extracted from fresh ore.
Zoom / A new method is helping to recover gold from e-waste at a higher rate than can be extracted from fresh ore.

Rikko Matsushita / Shinta Watanabe

Gold and some other precious metals are major components of computer chips, including those used in consumer electronics such as smartphones. But it can be difficult to recover and recycle those metals from e-waste. Japanese researchers have found that the widely used dye by artists called Prussian blue Gold and platinum group metals can be extracted from e-waste much more efficiently than conventional biological pipettes, according to last paper Published in Scientific Reports.

“The amount of gold contained in one ton of mobile phones is 300-400 grams, which is much higher by about 10-80 times than that in one ton of natural ore,” the authors wrote. “Other elements have a similar situation. Thus, the recovery of those precious elements from e-waste is more effective and efficient compared to their combinations from natural ore.”

Prussian blue is the first modern synthetic pigment. Granted, there was a dye known as Egyptian blue Used in ancient Egypt for thousands of years. The Romans called it caeruleum. But after the collapse of the Roman Empire, the dye was not used much, and eventually the secret of 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 pigment indigo, smalt, or expensive ultramarine made from lapis lazuli to obtain the deep blue shades.

It is believed that Prussian blue was first synthesized by accident by Berlin paint maker Johann Jacob Diesbach around 1706. Diesbach was attempting to make a red dye, which involves mixing potash, iron sulfate, and powdered cochineal. But the potash he used appears to have been contaminated with blood – one would assume it was from a finger cut or similar minor injury. The reaction that followed resulted in iron ferrocyanide having a characteristic blue color, and eventually came to be called Prussian blue (or Berlin blue).

The oldest known painting to use Prussian blue today is that of Peter van den Werf Christ’s tomb (1709), but the recipe was published in 1734, and Prussian blue quickly spread among artists. Famous Hokusai artwork, The Great Wave off Kanagawais one of the most famous works that used dye, along with Vincent van Gogh starry night And many paintings by Pablo Picasso.blue period. “

La Soupe (The Soup) From Pablo Picasso, from the artist’s blue period, Prussian blue on a large scale.” src=”https://cdn.arstechnica.net/wp-content/uploads/2022/06/prussianblue2-640×502.jpg” width=”640 ” height=”502″ srcset=”https://cdn.arstechnica.net/wp-content/uploads/2022/06/prussianblue2.jpg 2x”/>
Zoom / Pablo Picasso La Soupfrom the artist’s blue period, Prussian blue is widely used.

The dye has other uses. It is often used to treat heavy metal poisoning from radioactive thallium or cesium because its mesh-like structure — similar to a jungle gym — can trap metal ions from those metals and prevent them from being absorbed by the body. Prussian blue helped remove cesium from the soil around the Fukushima power plant after the 2011 tsunami. Prussian blue nanoparticles are used in some cosmetics, and pathologists use them as a stain to detect iron in bone marrow biopsy samples, for example.

So it’s a very useful material, which is why the Japanese authors of this latest research paper decided to explore other potential practical applications. They analyzed how Prussian blue absorbs polyvalent metals — such as platinum, ruthenium, rhodium, molybdenum, osmium and palladium, among others — using X-ray and ultraviolet spectroscopy. They were surprised by how well the dye retained the structure of the jungle gym while replacing iron ions in the structure, which is the secret to its impressive absorption efficiency compared to bio-absorbents. This is great news for e-waste recycling.

Prussian blue could also solve one of the nuclear waste disposal challenges, according to the authors. Current practice involves converting radioactive effluents to a glass-like state in a reprocessing plant, prior to disposal. But platinum group metals can accumulate on the walls of smelters, which ultimately leads to an uneven distribution of heat. So fuses must be rinsed after each use, which in turn increases costs. Prussian blue can remove these deposits without the need to clean the molten after each use.

DOI: Scientific Reports, 2022. 10.1038 / s41598-022-08838-1 (About DOIs).