Selective Binding and Precipitation of Cesium Ions from Aqueous Solutions: A Size-Driven Supramolecular Reaction

The nuclear disasters of Chernobyl and Fukushima presented an urgent need for finding solutions to treatment of radioactive wastes. Among the by-products of nuclear fission is radioactive ¹³⁷ Cs, which evokes an environmental hazard due to its long half-life (>30 years) and high solubility in water. In this work, a water-soluble organic ligand, readily obtained from alloxan and 1,3,5-benzenetriol, has been found to selectively bind and precipitate Cs⁺ ions from aqueous solutions. The special rigid structure of the ligand, which consists of a "tripodal" carbonyl base above and below an aromatic plane, contributes to the size-driven selectivity towards the large Cs⁺ ions and the formation of a giant, insoluble supramolecular complex. In addition to the low costs of the ligand, high yields and effectiveness in precipitating Cs⁺ ions, the Cs-complex revealed a high endurance to continuous doses of γ-radiation, increasing its potential to act as a precipitating agent for ¹³⁷ Cs.