EFFECT OF THE INTERFERENCE OF ALKALI AND ALKALINE-EARTH METAL-IONS ONTHE EXTRACTION OF SR-90 FROM ACIDIC NUCLEAR WASTE SOLUTIONS BY 18-CROWN-6 DERIVATIVES

The extraction of Sr-90 from liquid sodium-bearing wastes (SEW) at the Idaho Chemical Processing Plant (ICPP) by 4',4'(5')-di-(t-butyldicycl ohexo)-18-crown-6 (DtBuCH18C6) and cis-dicyclohexano-18-crown-6 (DCH18 C6) in l-octanol has been investigated. It has been shown that the pre sence of group I and group II metal ions which are co-extracted by the organic solvent limits the extraction of Sr2+ from nitric acid soluti ons. For example, extraction experiments which were performed with 0.1 5 M DtBuCH18C6 in l-octanol yielded D-Sr values which ranged from simi lar to 20 in 3M nitric acid to similar to 5 in a solution of 3M NaNO3 and 3M nitric acid. Furthermore, it has been shown that when the conce ntration of the Na+ is greater than or equal to 1.5M, an increase in t he total concentration of NO3- ion has little effect on the value of D -Sr. The value of D-Sr has been studied as a function of the concentra tion of Li+, K+, Na+, Cs+, and Ca2+. Additionally, a comparative study of commercially available 18-crown-6 derivatives has been performed. It has been shown that although DtBuCH18C6 yields larger values of D-S r in nitric acid solutions than DCH18C6, the extractants yield very si milar results in SEW. This is explained by the observation that the pr esence of group I and group II metal ions interferes with the extracti on of Sr2+ by DtBuCH18C6 to a greater extent than that of DCH18C6.