Optimization of Process Parameters in the Stripping (Back-Extraction) Stage of Uranium and Thorium: An Experimental Batch-Scale Study

Document Type : Research paper

Authors

1 Department of Chemical Engineering, Faculty of Engineering and Technology, University of Mazandaran, Babolsar, Iran

2 Department of Processing, Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, Tehran, Iran

Abstract

Objective: The aim of this study is to investigate the stripping (back-extraction) process of uranium and thorium from a loaded organic phase containing tributyl phosphate (TBP) and to evaluate the effect of process parameters on increasing the recovery percentage and improving separation efficiency at the laboratory scale.
Materials and methods: The stripping process was carried out experimentally, and the effects of aqueous solution pH, temperature, contact time, mixing intensity, and organic-to-aqueous (O/A) phase volume ratio were examined.
Results: The results showed that decreasing the hydrogen ion concentration significantly increased the stripping efficiency of uranium, while pH variation had no noticeable effect on thorium behavior. This behavioral difference is qualitatively attributed to the greater dependence of the uranium extraction and stripping equilibrium on process conditions, particularly pH and temperature, whereas thorium behavior is mainly governed by the chemical nature of its nitrate species and exhibits less sensitivity to changes in process parameters. Accordingly, thorium efficiency remained relatively constant within a certain range, while uranium efficiency changed markedly under the influence of process conditions. Increasing the temperature up to 55°C improved uranium stripping efficiency, with no significant change observed at higher temperatures. Investigation of contact time and mixing intensity showed that increasing these parameters had no considerable effect on final efficiency, and beyond a certain point, no noticeable change in mass transfer was observed. Furthermore, the phase ratio of 1:1, while maintaining appropriate efficiency, proved to be more economical in terms of aqueous phase consumption.
Conclusions: Under optimal conditions, including a temperature of 55°C, contact time of 30 minutes, mixing speed of 400 rpm, and phase ratio of 1:1, the stripping percentages of uranium and thorium were 89.3% and 72.4%, respectively, indicating the appropriate efficiency of the process under these 

Keywords

Main Subjects

References

[1] Revol, J.-P., Bourquin, M., Kadi, Y., Lillestol, E., de Mestral, J.-C., & Samec, K. (2016). Thorium energy for the world. Proceedings of the ThEC13 conference, CERN.
 
[2]  Sokolov, F., Fukuda, K., & Nawada, H. (2005). Thorium fuel cycle-Potential benefits and challenges. IAEA TECDOC, 1450.
 
[3] Habashi, F. (1993). A textbook of hydrometallurgy: Métallurgie extractive. Quebec, Enrc Canada.
 
 [4] Singh, H., & Gupta, C. (2000). Solvent extraction in production and processing of uranium and thorium. Mineral Processing and Extractive Metullargy Review, 21(1-5), 307-349. https://doi.org/10.1080/08827500008914172
 
[5] Sole, K. C., & Hiskey, J. B. (1995). Solvent extraction of copper by Cyanex 272, Cyanex 302 and Cyanex 301. Hydrometallurgy, 37(2), 129-147. https://doi.org/10.1016/0304-386X(94)00023-V
 
[6] Rydberg, J., Cox, M., Musikas, C., & Choppin, G. (2004). Solvent extraction and practice. In: MARCEL DEKKER Inc.
 
[7] Singh, S. K., Dhami, P., Tripathi, S., & Dakshinamoorthy, A. (2009). Studies on the recovery of uranium from phosphoric acid medium using synergistic mixture of (2-Ethyl hexyl) Phosphonic acid, mono (2-ethyl hexyl) ester (PC88A)andTri-n-butylphos (TBP). Hydrometallurgy, 95(1-2), 170-174. https://doi.org/10.1016/j.hydromet.2008.04.006
 
[8] Giridhar, P., Venkatesan, K., Subramaniam, S., Srinivasan, T., & Rao, P. V. (2008). Extraction of uranium (VI) by 1.1 M tri-n-butylphosphate/ionic liquid and the feasibility of recovery by direct electrodeposition from organic phase. Journal of Alloys and compounds, 448(1-2), 104-108. https://doi.org/10.1016/j.jallcom.2007.03.115
 
[9] Awwad, N. S. (2004). Equilibrium and kinetic studies on the extraction and stripping of uranium (VI) from nitric acid medium into tri-phenylphosphine oxide using a single drop column technique. Chemical Engineering and Processing: Process Intensification, 43(12), 1503-1509. https://doi.org/10.1016/j.cep.2004.02.005
 
[10]  Singh, H., Mishra, S., & Vijayalakshmi, R. (2004). Uranium recovery from phosphoric acid by solvent extraction using a synergistic mixture of di-nonyl phenyl phosphoric acid and tri-n-butyl phosphate. Hydrometallurgy, 73(1-2), 63-70. https://doi.org/10.1016/j.hydromet.2003.08.006
 
[11] Shadrin, A., Kamachev, V., Murzin, A., & Shafikov, D. (2007). Extraction of nitric acid and uranyl nitrate by TBP in HFC-134a. The Journal of supercritical fluids, 42(3), 347-350. https://doi.org/10.1016/j.supflu.2007.05.005
 
[12] Stas, J., Khuder, A., & Karjou, J. (2008). Direct determination of uranium and co-extracted elements in the organic phases (D2EHPA/TOPO, TBP, TDA) in kerosene by TXRF technique. Applied Radiation and Isotopes, 66(4), 450-456. https://doi.org/10.1016/j.apradiso.2007.10.012
 
[13] Benedict, M., Pigford, T. H., & Levi, H. W. (1981). edition 2. Nuclear chemical engineering.
 
[14] Alibrahim, M., & Shlewit, H. (2007). Solvent extraction of uranium (VI) by tributyl phosphate/dodecane from nitric acid medium. Periodica Polytechnica Chemical Engineering, 51(2), 57-60. https://doi.org/10.3311/pp.ch.2007-2.09
 
[15] Tanabe, T., & Kondo, Y. (1976). Solvent extraction of thorium nitrate and nitric acid by tributyl phosphate. Transactions of the Japan Institute of Metals, 17(7), 426-434. https://doi.org/10.2320/matertrans1960.17.426
 
[16] Schulz, W. W., Bender, K. P., Burger, L. L., & Navratil, J. D. (1989). Science and technology of tributyl phosphate.
 
[17] Khanramaki, F., Keshtkar, A., & Sohbatzadeh, H. (2025). Separation of thorium from a multi-component aqueous solution by liquid-liquid extraction method: investigation and comparison of different solvents. Journal of Nuclear Science, Engineering and Technology (JONSAT), 46(1), 77-84. https://doi.org/10.24200/nst.2024.1646
 
[18] Ali, A. (2017). Coextraction and successive selective stripping of cerium (IV) and thorium from monazite leach solutions with tributyl phosphate (TBP). Radiochemistry, 59(6), 579-586. https://doi.org/10.1134/S10663622170600054
 
[19] Rahmati, A., Ghaemi, A., & Samadfam, M. (2011). Uranium recovery from solid waste of a uranium conversion facility’s fluorination reactor by using solvent extraction method. J Sep Transp Phenom (J School Eng), 1, 97-107.
 
[20] Torkaman, R., Moosavian, M., Safdari, J., & Torab-Mostaedi, M. (2013). Synergistic extraction of gadolinium from nitrate media by mixtures of bis (2, 4, 4-trimethylpentyl) dithiophosphinic acid and di-(2-ethylhexyl) phosphoric acid. Annals of Nuclear Energy, 62, 284-290. https://doi.org/10.1016/j.anucene.2013.06.028
 
[21] Zahakifar, F., Khanramaki, F., Nejad, D. G., Ghazanfari, V., & Yadollahi, A. (2025). The solvent extraction and stripping process using Alamine 336 with a case study of uranium. Scientific Reports, 15(1), 11749. https://doi.org/10.1038/s41598-025-96421-9
 
[22] Khanramaki, F., Shirani, A., Safdari, J., & Torkaman, R. (2018). Investigation of liquid extraction and thermodynamic studies on uranium from sulfate solution by Alamine 336 as an extractant. International Journal of Environmental Science And Technology, 15(7), 1467-1476.
Journal of Separation Science and Engineering
Volume 18, Issue 1
June 2026
Pages 1-13

Files

Share

How to cite

Statistics