In the art world, Prussian blue was originally used as a pigment and dye, and painters such as Picasso, Van Gogh and Katsushika Hokusai used it for its deep blue color. And in the chemical world, scientists have found another interesting property and special use for this pigment. A related paper was recently published in Scientific Reports.

One of the big problems with nuclear waste and electronic waste is that gold, platinum group metals and other metals, which are key metals in computer chips, are wasted in the disposal process. Jun Onoe and Shinta Watanabe of Nagoya University in Japan, in collaboration with Takeshita Kenji of Tokyo Institute of Technology, have found that the solution to this pressing environmental and technological problem may lie in Prussian blue.

Prussian blue has a climbing shelf-like lattice in its nanospace. Previous experiments have found that it can absorb platinum group metals, however, it is not clear how this works.

The researchers used inductively coupled plasma atomic emission spectroscopy, UV-visible near-infrared spectrophotometry and more to learn more about this process.

"Prussian blue nanoparticle adsorption experiments revealed that it absorbs platinum group metals through iron ion substitution while maintaining the climbing frame structure." Onoe explained that this mechanism allowed Prussian Blue nanoparticles to absorb more gold and platinum group metals than conventional bio-based adsorbents.

The study demonstrates a solution to the nuclear waste disposal problem - the recovery of platinum group metals. During reprocessing of highly radioactive waste streams, platinum group metals often settle on the sidewall surface of the melter, affecting stability and increasing disposal space and costs.

This study found that 0.13 grams of ruthenium, 0.16 grams of rhodium, 0.30 grams of palladium and 0.107 grams of molybdenum could be recovered using 1 gram of Prussian blue nanoparticles. And more recently, Prussian Blue was used to remove radioactive cesium-134 and 137 elements from contaminated soil caused by the Fukushima nuclear power plant accident.

The gold content in 1 ton of cell phone is 300-400 grams, which is 10-80 times higher than the gold content in natural ores. The Prussian blue nanoparticles are heat-, nitrate- and gamma-radiation-resistant, so the team's technology can be used not only in the nuclear waste disposal process, but also in the electronic waste recycling process.

Onoe said, "Our results suggest that Prussian blue or its analogues are strong candidates for improved recycling of precious metals from nuclear and electronic waste, especially when compared to conventional bio-based adsorbents/activated carbon."

The loss of valuable metals in waste disposal is a serious problem in the current context of increasingly limited natural resources. By improving the efficiency of metal recovery, Prussian Blue or similar materials are expected to make production more environmentally friendly and economical.

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