Extraction of U(VI) and Th(IV) into a highly hindered (GO) 2 PO(OH) extractant from an aqueous nitrate phase

Abstract

The extraction of U(VI) and Th(IV) from an aqueous nitrate phase into a highly sterically hindered extractant, bis (2, 6-dimethyl-4-heptyl) phosphoric acid, (C 9H 19O) 2 PO (OH), HD(DIBM) P, in n-heptane and benzene “carrier” diluents was studied. The extraction stoichiometries and the corresponding expression for the distribution ratio, K, in terms of the formality, F of HD(DIBM)P in the organic phase, hydrogen concentration [H +] and nitrate ion concentration [NO 3 −] in the aqueous phase, and K s for a 1.00F (HNO 3+NaNO 3) aqueous phase are U(VI): OU 2+ 2A+ 2( HY 2 0 ⇌ UO 2 (H 2Y 4) O+2H + AK= K sF 2 [H +] 2 Th(IV): Th 4+ A2No − 3 A+2(HY) 2 0⇌Th(No 3) 2(H 2Y 4) o+2H + AK= K s[NO − 3] 2F 2 [H +] 2 where (HY) 2 represents the dimer of HD(DIBM) P. The formulation of the extracted species does not imply any particular structure. The second power nitrate ion dependency established in the tracer studies of the extraction of Th(IV) from 1.00F (HNO 3+NaNO 3) into HD(DIBM)P was confirmed by gross analysis of the organic phase in a macro thorium extraction experiment. The K sNO3 − K sCl − is ∼10 5 for the extraction of Th(IV). Comparison of the formation of thorium complexes containing inorganic anions as part of the extracted entity in various extraction systems is discussed.