DIPHONIX-CS : A NOVEL COMBINED CESIUM AND STRONTIUM SELECTIVE ION EXCHANGE RESIN*

Abstract

ABSTRACT The recently developed Diphonix® resin contains the geminally substituted diphosphonic acid ligand chemically bonded to a styrene-divinylbenzene copolymer. The resin exhibits an extraordinarily strong affinity for actinides, especially in the terra- and hexavalent oxidation states. Therefore the resin has potential for application in TRU removal from nuclear wastes. The Diphonix-CS resin is a Diphonix-type resin that contains also phenolic groups chemically attached to the polymeric matrix. The phenolic groups exhibit high affinity for Cs+ ions from highly alkaline media. Thanks to the combined action of the diphosphonic acid and the phenolic groups, the Diphonix-CS resin can simultaneously remove actinide species, Cs and Sr from alkaline media. In this paper the results obtained in the characterization of the new resin are reported, with regard to the uptake equilibrium and kinetics of Cs+ and Sr+2 removal from NaOH solutions and from synthetic alkaline wastes. The chemical and radiolytic stability of the resin has been investigated. The results have indicated that the Diphonix-CS resin is remarkably stable under the experimental conditions of this work (up to 35 days in I to 4 M NaOH, and up to 200 MRad gamma ray absorbed dose). The possibility of stripping the Cs+ and Sr+2 from the resin has been investigated in column experiments by using 1 M HNO3 as the stripping agent. Some problems encountered in the stripping of Sr+2 and possible ways to improve the stripping performance are discussed.