A study on adsorption and desorption behaviors of¹⁴C from a mixed bed resin

Spent resin waste containing a high concentration of¹⁴C radionuclide cannot be disposed of directly. A fundamental study on selective¹⁴C stripping, especially from the IRN-150 mixed bed resin, was carried out. In single ion-exchange equilibrium isotherm experiments, the ion adsorption capacity of the fresh resin for non-radioactive HCO₃- ion, as the chemical form of¹⁴C, was evaluated as 11mg-C/g-resin. Adsorption affinity of anions to the resin was derived in order of NO₃- > HCO₃- ≥ H₂PO₄-. Thus the competitive adsorption affinity of NO₃ ^- ion in binary systems appeared far higher than that of HCO₃- or H₂PO₄-, and the selective desorption of HCO₃ ^- from the resin was very effective. On one hand, the affinity of Co²⁺ and Cs⁺ for the resin remained relatively higher than that of other cations in the same stripping solution. Desorption of Cs+ was minimized when the summation of the metal ions in the spent resin and the other cations in solution was near saturation and the pH value was maintained above 4.5. Among the various solutions tested, from the view-point of the simple second waste process, NH₄H₂PO₄ solution was preferable for the stripping of ¹⁴C from the spent resin.