Waste treatment by ion-exchange and precipitation methods after LOMI decontamination

Conventional polystyrene-based strong acid cation and strong base anion exchangers have been evaluated for the retention of 60Co from vanadium based low oxidation-state metal ion (LOMI) decontamination formulation. Cation exchange treatment results in decontamination factors (DFs) of 8--40 with respect to 60Co if the LOMI solution is treated immediately after decontamination but yields lower DFs of 3--4 if it is stored for >24 h under ambient conditions. In both cases, anionic treatment of the cation column effluent gives DFs in the range 45--400. These results point to the differential speciation of 60Co in fresh and stored LOMI solutions and hence the necessity of having both cation and anion exchange treatments for the near complete removal of 60Co. Coprecipitation with MnO2 obtained by mixing the used LOMI solution with the required amounts of alkaline KMnO4 employed for pretreating the oxide surfaces was also found to be an effective method for 60Co removal. From the point of view of total activity removal, the precipitation method was less efficient than ion-exchange method