Removal of radiocobalt from EDTA-complexes using oxidation and selective ion exchange

Methods for the removal of radiocobalt from an ethylenediaminetetraacetic acid (EDTA) complex of Co(II) (aqueous solution containing 10 μM Co(II) and 10 μM or 50 μM EDTA traced with ⁵⁷Co) are presented. The studies examined a combination of different oxidation methods and the sorption of ⁵⁷Co on a selective inorganic ion exchange material, CoTreat. The oxidation methods used were ultraviolet (UV) irradiation with and without hydrogen peroxide (H₂O₂), as well as ozonation alone or in combination with UV irradiation. Also, the possible contribution of Degussa P25 TiO₂ photocatalyst to degradation of EDTA was studied. The best results for the equimolar solution of Co(II) and EDTA were achieved by combining ozonation, UV irradiation, Degussa P25 TiO₂ and CoTreat, with approximately 94% sorption of ⁵⁷Co. High values for the ⁵⁷Co sorption were also achieved by ozonation (∼88%) and UV irradiation (∼90%) in the presence of CoTreat and Degussa P25 TiO₂. A surplus of EDTA over Co(II) was also tested using 10 μM Co(II) and 50 μM EDTA. Only a slight decrease, to ∼88% sorption of ⁵⁷Co, was detected compared to the value (∼90%) obtained with 10 μM EDTA.