Tracer studies in the solution chemistry of heavy elements

Abstract

Sorption of yttrium, lanthanum and cerium (III) ions on Zeo-Karb 225 (SRC 15) and De-acidite from perchlorate media has been studied at 25 C and a tracer concentration of the ions concerned. It has been found that the sorption of these ions on the resins in question follows nearly an identical pattern, and that the changes of the hydrogen-ion concentration in the pH range of 2.5-4 have only a very slight effect on the values of the distribution co-efficients. Taking yttrium-glycollate as a representative for the systems involving glycollate or other ligands and the triva-lent rare-earth ions and those from the actinium series using yttrium-91 as a tracer and a perchlorate medium of μ = 0.50M, the effect of the cross-linking of a resin on the β(_n) values of the system in question has been studied and found to be negligible for the 2%, 4-5%, and 8% DVB resins provided the necessary corrections due to swelling of the resins are duly taken into account. An investigation of the same system with Zem-Karb 225 (SRC 15) at different v/m ratios in the range of 15/0.20 and 15/0.60 has revealed that subject to the appropriate corrections due to swelling of the resin having been made, such changes of the v/m ratio have no significant effect on the values of the system concerned. It has been further observed that a treatment of a complexing solution with resins of different cross-linking practically entails no significant loss of the ligand species (glycollate) from the complexing solution. Having made the above investigations of the resin/solution behaviour in perchlorate media at 25 C, the method (cation-exchange) was adopted for a tracer study of the systems involving yttrium, lanthanum, cerium (III),europium (III), actinium and americium (III) ions and chloride, fluoride, sulphate, oxalate, -hydroxyisobutyrate and glycollate ligands. The stability constants have been computed by a graphic method based on a theory proposed by Fronaeus (^78,102). The results obtained are generalize in good agreement with those reported by other workers as a result of their investigation of the systems in question by ion-exchange, solvent-extraction, pH or potentiometric methods under comparable conditions, and have further shown the dependence of the chemistry of the concerned ions on the sizes of their respective crystal ionic-radii. The ratios of the β(_I) values for the lanthanum/ actinium and europium (III)/americium (III) systems involving sulphate, oxalate and α-hydroxyisobutyrate ligands have been worked out and found to be in general near unity; this is an evidence in support of similar interactions between the metal ions of both the lanthanum and actinium series and the noted ligands in aqueous systems.