Extraction of microamounts of europium and americium by a phenyltrifluoromethyl sulfone (FS 13) solution of hydrogen dicarbollylcobaltate
(H+B−) in the presence of octyl-phenyl-N,N-diisobutylcarbamoylmethyl phosphine oxide (“classical” CMPO, L) has been investigated. The equilibrium data have been explained
assuming that the complexes
(M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species in
FS 13 saturated with water have been determined. It was found that the stability constants of the corresponding complexes
Authors:M. Takeuchi, S. Tanaka, M. Yamawaki, and S. Tachimori
The coextraction equilibrium of technetium(VII) and uranium(VI) from nictric acid solution was studied in a system involvingn-octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) in decalin. Stoichiometry of technetium, uranium and CMPO in the Tc-U-CMPO complex was obtained from the distribution data by slope analysis. The results indicated that the enhanced extraction of technetium was caused by the formation of UO2NO3TcO4·nCMPO (wheren=2 and/or 3). It was found that this coextraction of technetium with uranium was well explained by using ion exchange reaction between UO2(NO3)2·2CMPO complex and TcO
The extraction of Eu3+ and Am3+ by a mixture of CMPO and dicarbollide in nitrobenzene has been studied. The synergetic effect of dicarbollide is pronounced at low acidities but still lower than for previously studied DBDECMP. Separation properties towards Am/Eu pair are small.
CMPO/TBP sorbed on Amberlite XAD7 resin was used for the separation of actinides and lanthanides from nitric acid solutions
by extraction chromatography. The distribution ratios of actinides and lanthanide fission products (Ce, Eu) as a function
of acid concentration and some complexing agents were determined. In strong HNO3 medium (>1 mol/l) the tri-, tetra- and hexavalent actinides as well as the lanthanides have shown great affinity for the
CMPO/TBP/XAD7 sorbent. The same behavior was found in HCl medium except for trivalent actinides and lanthanides which show
lower distribution values in the same acid range. The effect of some complexing agents as DTPA and ammonium oxalate were also
investigated. In DTPA only hexavalent actinides showed higher distribution value. On the basis of these differences, an alternative
procedure for actinide-lanthanide separation and actinides from each other is proposed.
Authors:A. Sengupta, V. Adya, P. Mohapatra, S. Godbole, and V. Manchanda
This paper describes the development of a separation method for americium from the effluents emanating from anion exchange
column, used for the recovery of plutonium from analytical waste solutions. The waste contained uranium, sodium, calcium and
iron as the major impurities as estimated by ICP-AES method. ~99% pure americium was obtained by three separation steps using
solvent extraction and extraction chromatography techniques. In the first step, uranium was quantitatively separated by giving
five contacts of equal volumes of 30% TBP in n-dodecane. Fe and Na were separated in the next step using 0.1 M TODGA + 0.5 M DHOA as the extractant. In the last step, Am
was separated from the co-extracted Ca (about 76%) using CMPO loaded extraction chromatographic column. The overall recovery
was >80% with decontamination factor (D.F.) from the impurities being >3000 while the purity of the product was 99%.
Authors:J. Mathur, M. Murali, M. Balarama Krishna, R. Iyer, R. Chitnis, P. Wattal, A. Bauri, and A. Banerji
The partitioning and recovery of237Np from three types of simulated high level waste solutions originating from PUREX processing of spent nuclear fuels such as sulfate bearing high level waste (SB-HLW), HLW from a pressurised heavy water reactor (PHWR-HLW) and from a fast breeder reactor (FBR-HLW) have been carried out using a mixture of 0.2M CMPO and 1.2M TBP in dodecane. Quantitative extraction of neptunium was possible by either oxidizing it to the hexavalent state keeping K2Cr2O7 at 0.01M concentration or by reducing it to tetravalent state keeping Fe2+ at 0.02M concentration. Stripping of neptunium was carried out using different reagents, such as dilute nitric acid, oxalic acid and sodium carbonate. Almost quantitative recovery of neptunium has been achieved during these studies.
Authors:V. Gopalakrishnan, P. Dhami, A. Ramanujam, M. Krishna, M. Murali, J. Mathur, R. Iyer, A. Bauri, and A. Banerji
Bench-Scale studies on the partitioning and recovery of minoractinides from the actual and synthetic sulphate-bearing high level waste (SBHLW) solutions have been carried out by giving two contacts with 30% TBP to deplete uranium content followed by four contacts with 0.2M CMPO+1.2M TBP in dodecane. The acidity of the SBHLW solutions was about 0.3M. In the case of actual SBHLW, the final raffinate contained about 0.4% -activity originally present in the HLW, whereas with synthetic SBHLW the -activity was reduced to the background level.144Ce is extracted almost quantitative in the CMPO phase,106Ru about 12% and137Cs is practically not extracted at all. The extraction chromatographic column studies with synthetic SBHLW (aftertwo TBP contacts) has shown that large volume of waste solutions could be passed through the column without break-through of actinide metal ions. Using 0.04M HNO3>99% Am(III) and rare earths could be eluted/stripped. Similarly >99% Pu(IV) and U(VI) could be eluted.stripped using 0.01M oxalic acid and 0.25M sodium carbonate, respectively. In the presence of 0.16M SO
(in the SBHLW) the complex ions AmSO
, UO2SO4, PuSO
and Pu(SO4)2 were formed in the aqueous phase but the species extracted into the organic phase (CMPO+TBP) were only the nitrato complexes Am(NO3)3·3CMPO, UO2(NO3)2·2CMPO and Pu(NO3)4·2CMPO. A scheme for the recovery of minor actinides from SBHLW solution with two contacts of 30% TBP followed by either solvent extraction or extraction chromatographic techniques has been proposed.
The octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), loaded as stationary phase on silica, has been used for the sorption of Eu and actinides from acidic aqueous solution. Different commerical solid support were investigated and, finally SiO2 was chosen. Experiments were performed to obtain basic data on actinide removal. Distribution coefficients, kinetics, sorption isotherms (three adsorption model correlations were tested) and the acidic concentration effect were studied.
Authors:A. Sengupta, S. Thulasidas, V. Adya, P. Mohapatra, S. Godbole, and V. Manchanda
During the simultaneous extraction of plutonium and uranium using anion exchange chromatographic technique from analytical
waste in hydrochloric acid medium, 241Am which is invariably present in the plutonium bearing fuel samples remains in the effluent. A two step separation scheme
was developed for the recovery and purification of Am from the assorted waste to facilitate the disposal of large volume of
aqueous waste and the purified Am solution was utilized for spectroscopic investigation. The separation scheme involved solvent
extraction using 0.1 M TODGA + 0.5 M DHOA for separation of americium from Fe, Pb, Ni and Na followed by extraction chromatographic
technique using CMPO on inert support as stationary phase for separation of Ca from Am. A systematic study on the extraction
behavior of Am from hydrochloric acid medium revealed that out of four extraction systems well known for actinide partitioning
namely 0.1 M TODGA + 0.5 M DHOA, 1 M DMDBTDMA, 0.2 M CMPO + 1.2 M TBP and 30% TRPO, only 0.1 M TODGA + 0.5 M DHOA extracts
americium from 7.5 M HCl feed acidity. A comparative study involving CMPO solvent extraction and column chromatographic technique
revealed that elution of Am from column is satisfactory as compared to inefficient stripping of Am from organic phase in solvent
extraction technique using 0.1 M HNO3. The purity of the final solution was checked for 17 elements of interest and was found to be 98% pure, while the overall
recovery of this two step separation scheme was found to be 95%.
Stripping of the nuclides U, Np, Pu, Am, Eu, Zr, Ru and Fe from the loaded TRUEX solvent (0.2M CMPO+1.2M TBP in dodecane) has been carried out with a potassium ferrocyanide solution. In four contacts, 98% or more of U, Pu, Am and Eu could be stripped whereas Zr and Ru recoveries were 94% and 92%, respectively. Further, the co-precipitation of Am, Pu, U and Eu on ferric ferrocyanide precipitate from the CMPO phase has shown high recovery of Am, Pu and Eu but lower for U.