Prospective evaluation of EDXRF for studying the cation exchange membrane separation of Co from Zr in oxalic acid media and comparison with radiotracer experiments

This work focuses on the selective separation of Co from Zr and Nb, for the decontamination of pressure tubes from pressurized heavy water reactor. Initial experiments were carried out using the respective radiotracers. These laboratory scale studies explore the feasibility of using oxalic acid, a benign complexing medium, for the Zr-Nb matrix, with targeted sorption of trace levels of ⁶⁰Co on cation exchange membranes. Sorption of Co(II) on the membrane followed pseudo second order kinetics and the equilibrium capacity was 1.89 meq g^-1. Oxalic acid concentration was a trade-off between the loading of matrix elements and the % sorption of Co(II). Energy dispersive X-ray fluorescence (EDXRF) spectrometry was used for monitoring the sorption of Co on the membrane from inactive sample solutions. Sorption improved the EDXRF detection limits for Co from 50 μg in solution to 1.3 μg on the membrane, where the total concentration of the matrix elements in solution was 50 g L^-1. EDXRF method was validated by spike recovery and radiotracer studies.