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JAPANESE researchers have produced Prussian blue with a surface area more than ten times greater than previously possible, enhancing its capacity to adsorb radioactive caesium.

Prussian blue – an insoluble blue pigment of potassium ferrous ferricyanide – is used to treat people who have been internally contaminated with caesium or non-radioactive thallium, by trapping the contaminants in the intestine to limit their reabsorption in the body. It has been shown to reduce the biological half-life of caesium from about 110 days to 30.

A group led by Yusuke Yamauchi at Japan’s National Institute for Materials Science (NIMS) has successfully produced Prussian blue with a surface area greater than 330 m²/g. They also showed that this increased surface area resulted in the adsorption of more than eight times the amount of caesium captured by existing commercial Prussian blue.

Previous attempts to increase the adsorption capacity of Prussian blue by increasing its surface area failed due to the breakdown of its crystalline structure. The NIMS work succeeded in producing mesoporous Prussian blue – containing pores with diameters between 2–50 nm – by adding water-soluble macromolecules to a solution in which nanoparticles of Prussian blue had been dispersed, and stirring the resulting solution under an acidic condition.

There have been dozens of cases of caesium contamination reported in Japan since the Fukushima disaster last year, with traces being found in both soil and foods. In December, an estimated 45 t of contaminated water leaked from treatment works at the stricken plant. Though not lethal at low doses, exposure to caesium can cause infertility and cancer.

Angewandte Chemie DOI:10.1002/anie.201105190