ENGINEERING TECHNOLOGY

Recycled metal, another use of Prussian blue


The new method of recovering gold from e-waste is more efficient than extracting from ore. Image source: Shinta Watanabe et al

In the art world, Prussian blue was originally used as a pigment and dye, and painters such as Picasso, Van Gogh and Katsushika Hokusai also used it for their deep blue color. In the chemical community, scientists have found that this pigment has another interesting property and special use. The relevant paper was recently published in Scientific Reports.

A big problem with nuclear and electronic waste is that gold, platinum group metals, etc., which are key metals in computer chips, are wasted during the 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 technical problem may lie in Prussian blue.

The nanospace of Prussian blue has a climbing frame-like lattice. Previous experiments have found that it can absorb platinum group metals, however, it is unclear how this works.

The researchers used inductively coupled plasma atomic emission spectra, ultraviolet-visible near-infrared spectrophotometers, and more to learn more about this process.

“Prussian blue nanoparticle adsorption of platinum group metals test found that while maintaining the structure of the climbing frame, it absorbed platinum group metals by iron ion substitution.” Onoe explains that this mechanism allows Prussian blue nanoparticles to absorb more gold and platinum group metals than traditional bio-based adsorbents.

This study demonstrates a solution to the problem of nuclear waste disposal – recycling platinum group metals. During the post-treatment of highly radioactive waste liquids, platinum group metals often precipitate on the sidewall surface of the melter, affecting stability and increasing disposal space and cost.

The study found that 0.13 g of ruthenium, 0.16 g of rhodium, 0.30 g of palladium and 0.107 g of molybdenum could be recovered using 1 g of Prussian blue nanoparticles. More recently, Prussian blue has been used to remove radioactive cesium-134 and 137 elements from contaminated soil caused by the Fukushima nuclear power plant accident.

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

“Our findings suggest that Prussian blue or its analogues are a strong candidate for improved recycling of precious metals in nuclear waste and e-waste, especially compared to traditional bio-based adsorbents/activated carbon,” Onoe said. ”

In the current situation of increasingly limited natural resources, the loss of valuable metals in waste disposal is a serious problem. By improving the efficiency of metal recycling, Prussian blue or similar materials are expected to make production more environmentally friendly and economical. (Source: China Science Daily Wang Fang)

Related paper information:https:// doi.org/10.1038/s41598-022-08838-1



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