Contents lists available at ScienceDirect Progress in Nuclear Energy journal homepage: www.elsevier.com/locate/pnucene A new study on Uranium (VI) stripping from loaded Alamine 336 using some of alkaline solutions S.L. Mir-mohammadi, M.H. Mallah ∗ , R. Torkaman, J. Safdari Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, PO Box 14155–1339, Tehran, Iran ARTICLE INFO Keywords: Uranium (VI) Leach liquor Stripping Ammonium carbonate Ammonium chloride Sodium carbonate Response surface methodology ABSTRACT Stripping of U (VI) from loaded Alamine 336 by synthetic sulphuric acid solution and real leach liquor solution was investigated by employing various stripping agents comparing (NH 4 ) 2 CO 3 , NH 4 Cl and Na 2 CO 3 in the con- centration range of 0.25–2.00 mol/L and phase ratio of 0.5–5.0. To study the effect of the operating parameters and to find optimum conditions, response surface methodology was employed. U (VI) stripping efficiency under the optimum conditions (0.8, 0.6 and 0.72 mol/L at the stripping concentrations as well as 1.81, 1.16 and 1.16 values for organic/aqueous phases ratio) equaled 67.32, 42.18 and 54.13% of (NH ) CO 42 3 , NH Cl 4 and Na 2 CO 3 stripping efficiencies, respectively. 1. Introduction Uranium (VI) is a relatively rare metal element often found in the earth layer in combination with other elements. Since the nuclear power electricity generation mainly depends on U (VI), the importance of this metal is growing daily. Before its use as a fuel for power plants, U (VI) ore should undergo several processing steps. These include crushing, grinding, leaching, concentration and purification by the solvent extraction and ion exchange, to take the form of a pure U 3 O 8 oxide (Connelly, 2008). The production of U (VI) concentrate from the sulphuric liquor ty- pically adopts solvent extraction techniques. The solvent extraction process uses an extraction step in which the solutes are transferred from the aqueous phase to the organic phase; this is often followed by a scrubbing stage in which the unwanted solutes are removed from the organic phase, then a stripping stage in which the necessary solutes are removed from the organic phase and the organic phase can then be treated to make it ready for use again. The most common and effective extractant used for U (VI) extrac- tion is Alamine 336, diluted with purified kerosene. A modifier, usually a long-chain alcohol, is also added to the organic solution to prevent the formation of the third phase and emulsion. The stripping of U (VI)(VI) complex from this loaded organic phase can be achieved by various stripping agents such as hydrochloric acid (HCl) (Crouse and Brown, 1955; Kumar et al., 2010; Rydberg, 2004), sulphuric acid (H 2 SO 4 ) (Kumar et al., 2010; Morais et al., 2005), nitric acid (HNO 3 )(Kumar et al., 2010; Rydberg, 2004), ammonia (NH 3 )(Kumar et al., 2010), hydrogen peroxide (H 2 O 2 )(Kumar et al., 2010), ammonium carbonate ((NH 4 ) 2 CO 3 )(Kumar et al., 2010; Rydberg, 2004; Hurst and Crouse, 1961), ammonium chloride (NH 4 Cl), ammonium nitrate (NH 4 NO 3 ) (Kumar et al., 2010; Pandey et al., 1991; Crouse and Brown, 1956), (NH 4 ) 2 SO 4 and ammonium tartrate ((NH 4 ) 2 C 4 H 4 O 6 )(Kumar et al., 2010). One of these techniques that Morais and co-workers studied was U (VI) stripping from a loaded tertiary amine (Alamine 336) by using sulphuric acid solution. The loaded organic solution containing 8.0 g/L U 3 O 8 was supplied by U (VI) concentrate plant from Caetite city, Bahia State. It consists of Alamine 336 (0.15 mol/L) and tridecyl alcohol (3% v/v) and purified kerosene, used as a modifier and as well as a diluent respectively. The H 2 SO 4 concentration effect on U (VI) stripping was investigated in the range of 2.0–5.0 mol/L. In this range the U (VI) stripping efficiency increases from 24% to 75%. G. Ramadevi and co-workers studied on U (VI) stripping using mixed solution of 1 N NaCl in 0.2 N H 2 SO 4 whose organic phase was Alamine 336 (2% v/v) dilute in kerosene. The loading capacity under these conditions was 1.2 g/L of U 3 O 8 . About 98% of U (VI) could be stripped from the loaded organic using NaCl (1 N) in H 2 SO 4 (0.2 N). R. Kumar and co-workers investigated U (VI) stripping by some strippers in the range 0.5–5.0 mol/L from loaded organic solution (0.01 mol/L Alamine 336) containing 106.7 mg/L. The results are shown in Table 1. In case of mineral acids as stripping agents, the stripping of metal reached 85.5% with H 2 SO 4 (5.0 mol/L), whereas HCl and HNO 3 stripped 34% and 32% with the same acidity. In case of other reagents the percentage stripping reached 100% at NH 4 Cl (0.5 mol/L) at the 5th stage of stripping. These results prove that NH 4 Cl is the best and https://doi.org/10.1016/j.pnucene.2017.12.001 Received 19 November 2016; Received in revised form 6 October 2017; Accepted 7 December 2017 ∗ Corresponding author. E-mail address: mmallah@aeoi.org.ir (M.H. Mallah). Progress in Nuclear Energy 103 (2018) 229–235 0149-1970/ © 2017 Elsevier Ltd. All rights reserved. T