PNNL

Abstract

Three initial proof-of-concept experiments were performed to test the removal of I and Te from solutions containing Mo for potential abatement during chemical processing to purify 99Mo. All three proof-of-concept experiments produced results indicating that further optimization could provide methods for I and/or Te abatement from multiple matrices. Decamp and Happel (2013) describe the use of CL resin from Eichrom Technologies loaded with Ag+ combined with Amberlite XAD-4 in the chromatographic separation of irradiated fission products in 1 M HNO3 to separate iodine species where iodide and iodate react with Ag+ and I2 adheres to the Amberlite resin. The method worked well under processing conditions in a medical isotope facility although many separation methods use higher concentrations of HNO3 which could adversely impact the Ag+ loading. The experiment performed here used a roughly 2 mL column of CL resin loaded with Ag+ and Amberlite XAD-4 to separate µg quantities of I, Te, and Mo in 3 M HNO3. The results indicate Te is not in the optimal oxidation state and did not adhere to the column, Mo does not adhere to the column, and the separation of iodine could not be determined due to issues with yielding stable iodine species using ICP-MS. The Ag elution was extremely low showing the column separation is not impacted using 3 M HNO3 under the conditions tested and an optimized method might be suitable for iodine abatement. The use of a redox reagent would be needed to use the method for Te abatement, however this a difficult prospect in HNO3. Like Ag+, some I and Te species react with Pb2+, therefore Pb2+could be implemented in a similar chromatography separation to CL resin loaded with Ag+. SR resin available from Eichrom Technologies sorbs Pb2+ strongly in 0.1-10 M HNO3 so this was chosen for the separation. The separation of a solution of I, Te, and Mo in 3 M HNO3 using SR resin loaded with Pb2+ resulted in the formation of PbI2 on the column as desired, little to no Te reacted with the Pb2+ indicating Te is not in the optimal oxidation state, and little to no Mo sorbed to the column as desired. The results indicate this method could be used in the removal of I from the solution with optimization of the chromatography parameters. The use of a redox reagent to adjust the Te oxidation state would be required to use this method for Te removal. Iodine and Te species also react with Sn2+ to produce a precipitate which can be filtered to separate I and Te from Mo; in the case of Te, Te metal is formed. Solutions of I, Te, and Mo in H2SO4 were contacted with 5% SnCl2 in H2SO4 followed by filtration. The results showed removal of a significant portion of Te and some removal of Mo. Maximizing the removal of Te while minimizing the Mo loss requires further optimization of the method. The experiments did show this could be a way to separate Te and Mo although there were issues with yielding I from an acidic solution which would need to be addressed. It should be noted that this method is not compatible with an oxidizing system like HNO3 since this will dissolve the Te metal formed. A neutral or reducing acid matrix like HCl or H2SO4 is required.