Supercritical Fluid Extraction (SFE) is emerging as a powerful technique in the extraction of metal ions. In the present study, the extraction of nitrates of uranium and thorium was carried out using supercritical carbon dioxide (Sc-CO2) modified with various organophosphorous compounds such as dialkylalkyl phosphonates, trialkyl phosphates and trialkyl phosphine oxides in the presence of co-solvents such as methanol, dichlormethane and n-hexane. The influence of ligand and co-solvent on the extraction of the metal nitrates was studied in detail. These studies have established that co-solvent plays an important role in the extraction as well as fractionation of uranium and thorium nitrates. Polar co-solvent, methanol provided faster extraction without fractionation whereas the non-polar solvent, e.g. n-hexane provided some fractionation of metal nitrates though the extraction kinetics was slower.
References
[1]
Caude, M. and Thiebaut, D. (1999) Practical Supercritical Fluid Chromatography and Extraction. Harwood Academic Publishers, Chur.
[2]
Erkey, C. (2000) Supercritical Carbon Dioxide Extraction of Metals from Aqueous Solutions: A Review. Journal of Supercritical Fluids, 17, 259-287. http://dx.doi.org/10.1016/S0896-8446(99)00047-9
[3]
Laintz, K.E., Wai, C.M., Yonker, C.R. and Smith, R.D. (1992) Extraction of Metal Ions from Liquid and Solid Mate- rials by Supercritical Carbon Dioxide. Analytical Chemistry, 64, 2875-2878. http://dx.doi.org/10.1021/ac00046a039
[4]
Wai, C.M. (1995) Supercritical Fluid Extraction of Trace Metals from Solid and Liquid Materials for Analytical Ap- plications. Analytical Sciences, 11, 165-167. http://dx.doi.org/10.2116/analsci.11.165
[5]
Lin, Y., Brauer, R.D., Laintz, K.E. and Wai, C.M. (1993) Supercritical Fluid Extraction of Lanthanides and Actinides from Solid Materials with a Fluorinated β-Diketone. Analytical Chemistry, 65, 2549-2551.
http://dx.doi.org/10.1021/ac00066a027
[6]
Iso, S., Uno, S., Meguro, Y., Sasaki, T. and Yoshida, Z. (2000) Pressure Dependence of Extraction Behaviour of Plu- tonium (IV) and Uranium (VI) from Nitric Acid Solution to Supercritical Carbon Dioxide Containing Tributyl Phos- phate. Progress in Nuclear Energy, 37, 423-428. http://dx.doi.org/10.1016/S0149-1970(00)00082-2
[7]
Tomioka, O., Meguro, Y., Enokida, Y., Yamamoto, I. and Yoshida, Z. (2001) Dissolution Behaviour of Uranium Oxi- des with Supercritical CO2 Using HNO3-TBP Complex as a Reactant. Journal of Nuclear Science and Technology, 38, 1097-1102. http://dx.doi.org/10.1080/18811248.2001.9715141
[8]
Mincher, B.J., Fox, R.V., Holmes, R.G.G., Robbins, R.A. and Boardman, C. (2001) Supercritical Fluid Extraction of Plutonium and Americium from Soil Using Theonytrifluoroacetone and Tributylphosphate Complexation. Radiochi- mica Acta, 89, 613-617.
[9]
Lin, Y., Wai, C.M., Jean, F.M. and Brauer, R.D. (1994) Supercritical Fluid Extraction of Thorium and Uranium Ions from Solid and Liquid Materials with Fluorinated beta Diketones and Tributyl Phosphate. Environmental Science and Technology, 28, 1190-1193. http://dx.doi.org/10.1021/es00055a034
[10]
Rao, A., Kumar, P. and Ramakumar, K.L. (2010) Separation of Uranium from Different Uranium Oxide Matrices Em- ploying Supercritical Carbon Dioxide Extraction. Journal of Radioanalytical and Nuclear Chemistry, 285, 247-257.
http://dx.doi.org/10.1007/s10967-010-0568-7
[11]
Smart, N.G., Carleson, T., Kast, T., Clifford, A.A., Burford, M.D. and Wai, C.M. (1997) Solubility of Chelating Agents and Metal Containing Compounds in Supercritical Fluid Carbon Dioxide. Talanta, 44, 137-150.
http://dx.doi.org/10.1016/S0039-9140(96)02008-5
[12]
Kumar, R., Sivaraman, N., Senthil Vadivu, E., Srinivasan, T.G. and Vasudeva Rao, P.R. (2003) Complete Removal of Uranyl Nitrate from Tissue Matrix Using Supercritical Fluid Extraction. Radiochimica Acta, 91, 197-201.
http://dx.doi.org/10.1524/ract.91.4.197.19966
[13]
Kumar, R., Sivaraman, N., Sujatha, K., Srinivasan, T.G. and Vasudeva Rao, P.R. (2007) Removal of Plutonium and Americium from Waste Matrices by Supercritical Carbon Dioxide Extraction. Radiochimica Acta, 95, 577-584.
http://dx.doi.org/10.1524/ract.2007.95.10.577
[14]
Suresh Kumar, V., Kumar, R., Sivaraman, N., Ravisankar, G. and Vasudeva Rao, P.R. (2010) Design and Adaptation of a Novel Supercritical Extraction Facility for Operation in a Glove Box for Recovery of Radioactive Elements. Re- view of Scientific Instruments, 81, 094101-094106. http://dx.doi.org/10.1063/1.3484190
[15]
Kumar, R., Sivaraman, N., Sujatha, K., Srinivasan, T.G. and Vasudeva Rao, P.R. (2009) A Novel Technique for Mod- ifier Free Delivery of Ligands for Supercritical Fluid Extraction. Radiochimica Acta, 97, 443-451.
http://dx.doi.org/10.1524/ract.2009.1633
[16]
Sujatha, K., Pitchaiah, K.C., Sivaraman, N., Srinivasan, T.G. and Vasudeva Rao, P.R. (2012) Recovery of Uranium and Plutonium from Waste Matrices Using Supercritical Fluid Extraction. American Journal of Analytical Chemistry, 3, 916-922. http://dx.doi.org/10.4236/ajac.2012.312A121
[17]
Sujatha, K., Pitchaiah, K.C., Sivaraman, N., Nagarajan, K., Srinivasan, T.G. and Vasudeva Rao, P.R. (2014) Recovery of Plutonium from Polymeric Waste Matrices Using Supercritical Fluid Extraction. Desalination and Water Treatment, 52, 470-475. http://dx.doi.org/10.1080/19443994.2013.808729
[18]
Brahmmananda Rao, C.V.S., Srinivasan, T.G. and Vasudeva Rao, P.R. (2012) Studies on the Extraction by Substituted Butyl Phosphonates. Solvent Extraction and Ion Exchange, 30, 262-277.
http://dx.doi.org/10.1080/07366299.2011.639250
[19]
Datta, A., Sivaraman, N., Srinivasan, T.G. and Vasudeva Rao, P.R. (2011) Liquid Chromatographic Behaviour of Ac- tinides and Lanthanides on Monolith Supports. Radiochimica Acta, 99, 275-283.
http://dx.doi.org/10.1524/ract.2011.1816
[20]
Suresh, A., Srinivasan, T.G. and Vasudeva Rao, P.R. (1994) Extraction of U(VI), Pu(IV) and Th(IV) by Some Trialkyl Phosphates. Solvent Extraction and Ion Exchange, 12, 727-744. http://dx.doi.org/10.1080/07366299408918234
