Selective ion-exchange sorbents for caesium extraction from alkaline radioactive solutions. Review

Abstract

This review covers studies dedicated to the search for and development of sorbents for the extraction of the caesium-137 radioactive isotope from highly mineralised, highly alkaline solutions that are waste products of nuclear plants. This isotope with a half-life of 30.2 years is one of the most significant contributors to the radioactivity of the waste. It was shown that phenolic sorbents play the key role in caesium extraction from such solutions, they are able to exchange ions on phenolic groups in alkaline solutions, exhibiting high selectivity to caesium against large amounts of sodium and potassium ions. The sorbents make it possible to filter large solution flows, as well as to elute concentrated caesium quantitatively and rapidly with a small volume of acid. We compared the selectivity of sorbents obtained by the condensation of phenol and diatomic phenols with formaldehyde as well as modern materials obtained by the condensation of calixarenes and resorcinarenes with aldehyde. It was shown that the latter do not have any advantage in selectivity and are of lower chemical stability. Therefore, resorcinol-based materials are considered the key element in solving the problem of extracting the caesium-137 isotope from alkaline solutions. We analysed the current state of the problem. This article explains the nature of the high selectivity of phenolic sorbents for caesium ions and why the special arrangement of functional groups of calixarene and resorcinarene resins does not result in increased selectivity as compared with conventional phenol- and resorcinol-based materials

Keywords

• сaesium-137 isotope
• highly mineralised alkaline solutions
• ion exchange
• sorbtion
• selectivity
• resorcinolformaldehyde resin
• calixarene
• resorcinarene