Journal o f R adioanalyticai and Nuclear Chem isl'ry, A rticles, VoL 91/1 (1985) 91-97 COMPARATIVE STUDIES ON THE IONEXCHANGE BEHAVIOUR OF UO2 (II), Ce(III) AND Am(III) WITH CHELEX-100 FROM THIOCYANATE MEDIA F. H. EL-SWEIFY, R. SHABANA, N. ABDEL-RAHMAN, H.F. ALY Nuclear Chemistry Department, Nuclear Research Centre, .Atomic Energy Establishment, Cairo (Egypt} (Received July 12, 1984) The distribution of UO~ § Ces+ and Ams+ between Chelex-lO0 and 0.2 and 5.0M ammonium thiocyanate solutions of different hydrogen ion concentrations has been investigated. The results obtained are compared with parallel experimental results using the anion exchanger Dowex-l• and the cation exchar, ger Dowex-50• It is found that Chelex-100 can act as anion exchaoger at pH <2 and as cation and chelate exchanger at higher pH. A main featvxe of the distribution results of UO~ § Am3§ and Ce ~§ with Chelex-100 is the very high distribution coefficient for the three cations at pH higher than 3.5 from aqueous solutions containing 0.2 or 5.0M ammonium thiocyanate. Introduction Chelex-100, which is a chelating resin containing iminodiacetate groups, found wide application in the enrichment and separation of traces of heavy metals from concentrated solutions, l -3 The main feature of this resin is its behaviour as anion, cation or chelating exchanger in different pH media.4 In the present work, the exchange behaviour of U(VI), Ce(III) and Am(IID from thiocyanate media of two different concentrations and at different pH with Chelex-100 have been investigated. To assess the exchange behaviour obtained with Chelex-100, parallel exchange studies using the cation exchanger Dowex-50X4 and the anion exchanger Dowex-l• have also been carried out for comparison. Materials Experimental All chemicals used were of analytical grade quality. Chelex-100 Na form (50-100 mesh) was a product of Bio-Rad Laboratory. Dowex-l• (100-200 mesh) and Dowex-50X4 (100-200 mesh) were products of Serva. All these resins were of analytical grade quality. Elsevier Sequoia S. A., Lausanne Alawldmiai Ktad6, Budapest