Degradation of a cobalt-EDTA complex by photocatalysis and [H.sub.2][O.sub.2]/UV-C. Application to nuclear wastes containing [sup.60]Co

The [sup.60]Co present in some low-level effluents forms complexes with organic ligands such as ethylenediaminetetraacetic acid (EDTA). These complexes make it difficult to remove the [sup.60]Co using conventional filtration methods. The aim of this study was to test the use of titanium-based photocatalysis (Ti[O.sub.2]/UV) and photochemical methods involving the use of oxidation agents ([H.sub.2][O.sub.2]/ UV-C) (both of which are advanced oxidation processes) to degrade EDTA and recover [sup.60]Co once it has been released from the complex. In preliminary experiments on the [sup.59]Co-EDTA complex, we tested the efficiency of the Ti[O.sub.2]/UV and [H.sub.2][O.sub.2]/UV-C processes as means of degrading EDTA molecules and releasing cobalt in its cationic forms [Co.sup.2+] and [Co.sup.3+]. These cations can be trapped by either precipitating and/or adsorbing them on Ti[O.sub.2] depending on the pH. When this treatment was applied experimentally to radioactive wastes, it turned out to be highly effective since it improved the decontamination factor (DF: initial volumic activity/final volumic activity) twofold. Keywords Photocatalysis * [H.sub.2][O.sub.2]/UV process * [sup.60]Co-EDTA degradation * Radioactive effluent * Decontamination factor