To investigate the enganced extraction yield of Tc from a simulated solution, a small amount of tri-n-octylamine was added to 30 vol% tributyl phosphate/n-dodecane (30% TBP/x% TOA). Effects of nitric acid and TOA concentrations on the selective co-extraction of Tc, Np and U from the solution were also studies. At less than 0.8 M HNO3, the extraction of Tc(D(Tc-TBP)) with 30% TBP occurred by a competition between H(+) ion concentration in the aqueous phase and free TBP concentration. Above 1 M HNO3, however, D(Tc-TBP) depended on only the free TBP concentration. At nitrate concentration of less than 2 M in the aqueous phase, however, the extraction of Tc(D(Tc-TBP/TOA)) with 30% TBP/x% TOA occurred through a simple anion exchange mechanism between TcO4(-) in the aqueous phase and NO3(-) ion in the organic phase. K2Cr2O7 was an effective oxidant of Np at 1 M HNO3. At 1 M HNO3, 0.001 M K2Cr2O7 and 30% TBP/0.5% TOA, the extraction yields of Tc, Np and U were 81.9%, 86%, 89.2%, resectively. However, the yields of Am, Eu, Nd, Mo and Fe were below 5%. It was found that 30% TBP/x% TOA was the most effective extraction condition that enhanced Tc extraction; the other elements were extracted by using TBP only. Coexisting elements such as Eu, Nd, Mo and Fe did not affect the extraction yields of Tc. When 30% TBP/x% TOA was used. then Zr had to be pre-removed to prevent the formation of three-phase.

본 연구는 30 vol.% TBP(tributyl phosphate)/dodecane에 TOA(tri-n-octyl amine)를 소량 첨가하는 방법(30% TBP/x% TOA)에 의해 Tc의 추출율을 증진시키면서 Tc, Np, U만을 선택적으로 공추출시키는 조건을 찾기 위하여 수행하였다. 30% TBP에 의한 Tc추출의 경우(D(Tc-TBP)) 질산농도 0.8 M 이하에서는 H(+) 농도와 TBP의 자유농도 간의 경쟁반응으로, 1M 이상에서는 TBP의 자유농도에만 의존하여 추출된다. 반면에 30% TBP/x% TOA의 경우(D(Tc-TBP/TOA)) 수용상 내 NO3(-) 농도 2M 이하에서는 TOA 내 함유되어 있는 NO3(-)과 수용상 내 TcO4(-)간의 음이온 교환반응에 의해 추출된다. 한편 질산농도 1M에서는 Np 산화제는 K2Cr2O7가 효과적이며, 1M HNO3 및 0.001 M K2Cr2O7에서 30% TBP/0.5% TOA에 의한 Tc, Np, U의 추출율은 각각 81%, 89.2%였으며, 기타 Am, Nd, Mo, Fe등은 5% 이하였다. 이로부터 30% TBP/ x% TOA가 Tc의 추출증진을 위한 가장 효과적인 방법이라는 것과 Tc을 제외한 기타 원소의 추출은 거의 TBP에 의해 주도됨을 알 수 있다. 그리고 공존원소가 Tc의 추출에 미치는 영향은 없고, 30% TBP/x% TOA사용 시 제 3상의 생성 방지를 위해 Zr의 선 제거가 필요하다.