Effects of γ-ray Irradiation on Thiodiglycolamide-type Extractant-impregnated Adsorbents for Separation of Platinum Group Metals from High-level Liquid Waste

To estimate the applicability of thiodiglycolamide-type extractant-impregnated adsorbents to separation of the platinum group metals (PGMs) from high-level liquid waste, radiation effects on the adsorption behavior of PGMs onto a macroporous silica-based (Crea-TOA)/SiO2-P absorbent and on the stability of the adsorbent were investigated by using γ-rays emitted from 60Co, and the results were compared with those obtained using (MOTDGA-TOA)/SiO2-P. A difference in adsorption behaviors of PGMs onto the two adsorbents was not observed with or without irradiation up to 100 kGy of the absorbed dose. Decomposition of the impregnated extractants and degradation of the adsorption capability increased with increasing absorbed dose, but the distribution coefficient of Pd remained >102 up to approximately 250 kGy. The retention ratio of loaded PGMs gradually decreased with increasing absorbed dose. From these results, the adsorbents were considered to be useful for the adsorption of PGMs irrespective of whether the adsorption system was irradiated, except for when the adsorbent was irradiated by a very large dose.