AsianScientist (May 28, 2014) – Korean researchers have developed a material that can remove radioactive cesium more effectively than conventional sorbents. This research has been published in the journal Angewandte Chemie.
Cesium 137 (Cs-137) is among the most dangerous radioactive nuclides. With a half-life of 30 years, Cs-137 contaminated areas remain polluted for a long time. The high solubility of cesium salts in water facilitates its dispersal in the environment and its uptake by plants. If humans ingest this contaminated food, the body cannot differentiate the cesium from potassium, resulting in cesium accumulation in muscle tissue. Larger amounts can cause severe radiation sickness; smaller amounts can cause diseases like cancer.
The removal of Cs-137 from contaminated ground- and seawater, as well as liquid nuclear waste from reprocessing and nuclear energy plants is therefore a critical public health issue. However, very high relative concentrations of competing cations like sodium, calcium, magnesium, and potassium ions make it difficult to build an effective and selective cesium trap.
Although a wide variety of inorganic materials have been developed for cesium trapping, there has been no substantial progress in the last 20 years. To date, titanosilicates, which were used after the Fukushima reactor disaster, have worked best.
Kyung Byung Yoon and a team from Sogang University in Seoul, South Korea have now developed a new material named as “Sogang University-45” (or SGU-45 for short) that very effectively binds and immobilizes cesium from groundwater, seawater, and liquid nuclear waste. Under the test conditions used, SGU-45 was shown to be superior to all previous materials with regard to selectivity, capacity, and rate of absorption. Strikingly, a variant loaded with potassium ions known as K-SGU-4 more strongly selects for cesium as the cesium concentration decreases.
SGU-45 is a microporous vanadosilicate with vanadium ions in the 4+ and 5+ oxidation states. Cesium ions are absorbed from the environment by exchange with the potassium ions in K-SGU-45.
The unique structure of SGU-45 includes non-exchangeable cesium ions which are 16-coordinate, meaning that they have 16 neighboring atoms bonded to cesium. This observation is of academic interest because this is the highest coordination number (the number of nearest neighbors in a crystal lattice or complex) observed in chemistry to date.
The article can be found at: Datta et al. (2014) A Novel Vanadosilicate with Hexadeca-Coordinated Cs+ Ions as a Highly Effective Cs+ Remover.
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Source: Angewandte Chemie International.
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