Stripping of hafnium and zirconium from chelating ion-exchange resin

Separation of hafnium from zirconium on Diphonix® resin is very successful. However, the chemical affinity of these elements to the Diphonix® resin is very strong. Therefore, the aim of the present study was to develop a method that would permit the desorption of these metals and the regeneration of the resin. For this purpose, solutions of various ligands such as citrate, oxalate, EDTA, tiron, and carbonate were examined. The lowest weight distribution coefficients of hafnium and zirconium on Diphonix® resin were obtained using a 0.25 M ammonium oxalate solution. Its use gave satisfying results with a very good level of the metals recovery in dynamic studies. Due to difficulties in the processing of the obtained zirconium(IV) (hafnium(IV)) oxalate into zirconium(IV) (hafnium(IV)) sulfate, some modification of the stripping method was proposed. The elution of the studied elements by ammonium oxalate solution was preceded by elution with 2 M sulfuric acid. It permitted the removal of 70% of the adsorbed zirconium(IV) as a sulfate solution, ready for returning into the Zr and Hf ion-exchange separation process.