Studies on hydrolytic and radiolytic stability of N,N,N´,N´-tetra-(2-ethylhexyl) thiodiglycolamide T(2EH)TDGA

Abstract

Hydrolytic and radiolytic stability of T(2EH)TDGA solvent system has been investigated to establish its application in separation and recovery of palladium from High Level Liquid Waste (HLW) solutions. Hydrolysis of T(2EH)TDGA solvent system with nitric acid was not observed. Moreover, unlike other “S” donor extractants used for the said purpose, the oxidation of thioetheric sulphur to sulphoxide or sulphones was also not observed. However, radiolytic degradation was notably observed and found to increase with increase in absorbed dose. n-dodecane was found to sensitize the degradation of T(2EH)TDGA. At gamma radiation dose of 0.2 MGy, no significant loss of T(2EH)TDGA was observed. The degradation products were identified by GC-MS. The major products were found to be formed by cleavage of thioetheric and amidic bonds of T(2EH)TDGA molecule. The extraction studies of palladium with irradiated solvent indicate that with 0.025 M T(2EH)TDGA/n-dodecane, there was no significant change in D_Pd up to an absorbed dose of 0.2 MGy above which it decreases significantly. However, with 0.05 M T(2EH)TDGA/n-dodecane, there is gradual decrease in D_Pd with increase of absorbed dose. Further, the radiolysis does not affect the stripping behavior of palladium. Extraction studies of Pd(II) and other fission products from simulated high level liquid waste (SHLW) solutions to irradiated solvent system showed that, except palladium, any other element is hardly extracted thus retaining its remarkable selectivity.