Solvent extraction of technetium(VII) by cyclic amides

The extraction behavior of heptavalent technetium with cyclic amides inn-dodecane from nitric acid solution was studied. The amides investigated are N-(2-ethyl)hexylbutyrolactam(EHBLA). N-(2-ethyl)hexylvalerolactam(EHVLA), N-(2-ethyl)hexyl-caprolactam (EHCLA), N-octylcaprolactam(OCLA), a mixture of 3-octyl-N-(2-ethyl)hexylvalerolactam and 4-octyl-N-(2-ethyl)hexylvalerolactam (3,4,OEHVLA), 2-octyl-N-(2-ethyl)hexylcaprolactam(2OEHCLA), a mixture of 3-octyl-N-(2-ethyl)hexylcaprolactam and 5-octyl-N-(2-ethyl)hexylcaprolactam(3,5,OEHCLA) and that of 3-octyl-N-octylcaprolactam and 5-octyl-N-octylcaprolactam(3,5,OOCLA). From the results of the distribution ratio of Tc(VII) as a function of acid concentration, cyclic amides concentration and HTcO₄ concentration, the effects of both the ring size of cyclic amide and structure of the substituents attached to different positions of the cyclic ring on the extraction behavior of Tc(VII) were discussed. A clear steric hindrance was observed. For applications, 3,4,OEHVLA is proposed as the best extractant for Tc from acidic solution.