In this study, extraction of uranium(VI) from an aqueous nitric acid solution was investigated using tri-n-butyl phosphate (TBP) as an extractant in an ionic liquid, 1-alkyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ([Cnmim][Tf2N]). The distribution ratio of U(VI) in 1.1 M TBP/[Cnmim][Tf2N] was significantly high when the concentration of nitric acid was low. The value of the distribution ratio decreased as the concentration of the nitric acid increased at lower acidities, and then increased with a nitric acid concentration of up to 8 M. This can be attributed to the different extraction mechanisms of U(VI) based on nitric acid concentrations. Thus, a cation exchange at low acidity levels and an ion-pair extraction at high acidity levels were suggested as the extraction mechanism of U(VI) in the TBP/[Cnmim][Tf2N] system.

30 % TBP/NDD-2 M HNO3 (0.005 M K2Cr2O7 함유) 계에 의해 산화 추출된 Np의 유기상을 대상으로 n-butyraldehyde (NBA)에 의한 Np의 환원 역추출을 고찰하였다. Np의 역추출은 NBA의 농도 증가에 따라, 역추출 수용상 내 질산농도 감소에 따라, 그리고 반응 온도 감소에 따라 증가하였으며, 이때 겉보기 환원 역추출 속도식은 -d [Np]Org./dt =1,524 exp(-2,906/T) [NBA]0.91[H+]-0.92 [Np]Org. 이었다. 1.04M NBA 및 2M HNO3에서 Np 및 U의 역추출률은 각각 70.1 % 및 7.1 % 이며 이때 분리계수((DU/DNp)는 30.4 정도로, TBP-HNO3 계에 의해 공추출된 Np과 U은 NBA에 의해 효과적으로 상호 분리할 수 있음을 알 수 있었다.

The solid phase extractant SAN-D2EHPA/TBP containing two extractants of Di-(2-ethylhexyl)phosphoric acid (D2EHPA) and Tri-butyl-phosphate (TBP) was prepared by immobilizing two exractants D2EHPA and TBP in styrene acrylonitrile copolymer (SAN). The prepared SAN-D2EHPA/TBP was characterized by using fourier transform infrared spectrometer (FTIR) and scanning electron microscopy (SEM). The solid phase extractant SAN-D2EHPA/TBP was tested for the removal of Cu(II) from aqueous solution. Experiments were carried out as a function of the pH and Cu(II) concentration in the aqueous phase. The equilibrium time was 180 min and equilibrium experiment data obeyed the pseudo-second-order kinetic model. The Langmuir isotherm model represented the experiment data as well. The maximum removal capacity of Cu(II) calculated from Langmuir isotherm model was 3.1 mg/g.

The feasibility of PS-D2EHPA/TBP beads prepared by immobilizing two extractants D2EHPA and TBP in polysulfone to remove Sr(II) from aqueous solution was investigated in batch system. Batch experiments were carried out to study equilibrium isotherms, kinetics, and thermodynamics. Equilibrium data were fitted using Langmuir, Freundlich, Redlich– Peterson, and Dubinin-Radushkevich equation models at temperatures of 298 K, 313 K, and 328 K. The removal capacity of Sr(II) by PS-D2EHPA/TBP beads obtained from Langmuir model was 2.41 mg/g at 298 K. The experimental data were well represented by pseudo-second-order model. The removal process of Sr(II) by PS-D2EHPA/TBP beads prepared in this study was found to be feasible, endothermic, and spontaneous.

Removal characteristics of Cu(II) ions by solid-phase extractant immobilized D2EHPA and TBP in PVC were investigated. Cu(II) ion concentrations in the solution and removal capacity of Cu(II) ion according to operation time were compared. The lower the initial concentration of Cu(II) ion in aqueous solution was, the removal capacity of Cu(II) ion by solid-phase extractant was increased relatively. The bigger the initial concentration of Cu(II) ion was, the removal capacity of Cu(II) ion was increased relatively. The pseudo-second-order kinetics according to operation time was showed more satisfying results than the pseudo-first-order kinetics for the removal velocity of Cu(II) ion. The removal capacity of Cu(II) ion was 0.025 mg/g in aqueous solution of pH 2, but the removal capacity of Cu(II) ion was increased to 0.33 mg/g mg/g in aqueous solution of pH 4 according to increasing pH.

The solid-phase extractant PS-D2EHPA/TBP was prepared by immobilizing two extractants D2EHPA and TBP in polysulfone (PS). The prepared PS-D2EHPA/TBP was characterized by using fourier transform infrared spectrometer (FTIR) and scanning electron microscopy (SEM). The removal of Cu(II) from aqueous solution was investigated in batch system. The experiment data were obeyed the pseudo-second-order kinetic model. Equilibrium data were well fitted by Langmuir model and the removal capacity of Cu(II) by solid extractant PS-D2EHPA/TBP obtained from Langmuir model was 3.11 mg/g at 288 K. The removal capacity of Cu(II) was increased according to increasing pH from 2 to 6, but the removal capacity was decreased below pH 3 remarkably.