Method for enriching uranium and thorium from water phase by using cloud point extraction technology

[0022] Example 1. UO is extracted from the water phase using cloud point extraction 2 2+ Or Th 4+

[0023] In the extraction experiment, the quantitative surfactant TX-114, the extraction agent TOPO, ionic liquid, uranyl ion (UO 2 2+ ) Or thorium ion (Th 4+ ) Solution and NaNO 3 Solution, distilled water three times to make up to 10mL. After shaking, keep the temperature at 70°C for 2h, centrifuge while hot, and analyze the U(VI) or Th(IV) concentration of the upper water phase (determination method: ICP-AES or inductively coupled plasma emission spectroscopy). The concentration of U(VI) or Th(IV) extracted into the surfactant phase is determined by the difference subtraction method, thereby obtaining the extraction rate E.

[0024] Without additional acid and the concentration of TX-114 in the aqueous solution is 0.01mol/L, the concentration of TOPO is 0.0005mol/L, NaNO 3 Under the condition of the concentration of 0.1mol/L, do not add or add different C n mimNTf 2 Ionic liquids for uranyl ions ([UO 2 2+ ] = 0.00005mol/L) or thorium ion ([Th 4+ ]=0.00005mol/L) uranyl ions or thorium ions in the aqueous solution were extracted, and the extraction rate was determined. See the result figure 1 (1: No ionic liquid, 2: C 2 mimNTf 2 , 3: C 4 mimNTf 2 , 4: C 6 mimNTf 2 , 5: C 8 mimNTf 2 , 6: C 10 mimNTf 2 , 7: C 12 mimNTf 2 ).

[0025] by figure 1 It can be seen that without the addition of acid, when the concentration of TX-114 in the aqueous solution is 0.01 mol/L, the TOPO cloud point of 0.0005 mol/L is used alone to extract the UO of 0.00005 mol/L. 2 2+ And Th 4+ , The extraction efficiency is ~36% and 30%. When 0.001mol/L C is added to the system 2 mimNTf 2 When the extraction efficiency is increased to ~75% and ~66%. Will C 2 mimNTf 2 Replace with C respectively 4 mimNTf 2 , C 6 mimNTf 2 , C 8 mimNTf 2 , C 10 mimNTf 2 Or C 12 mimNTf 2 , The extraction efficiency of U's extraction system and C 2 mimNTf 2 The system is basically the same; for the extraction system of Th, add C 4 mimNTf 2 , C 6 mimNTf 2 , C 8 mimNTf 2 The extraction efficiency of the system and the addition of C 2 mimNTf 2 The system is basically the same, but adding C 10 mimNTf 2 And C 12 mimNTf 2 The extraction efficiency of the system has been reduced.

[0026] Take C 4 mimNTf 2 -CPE system extracts U(VI) as an example to investigate the influence of various conditions. Without adding acid, maintain TOPO concentration at 0.0005mol/L, NaNO 3 The concentration is 0.1mol/L, C 4 mimNTf 2 The concentration is 0.001 mol/L, the concentration of TX-114 is changed to extract U(VI) (the concentration is 0.00005 mol/L), and the extraction rate is determined. Such as figure 2 As shown, as the concentration of TX-114 increases, the extraction efficiency of the system for uranyl ions increases, but the volume of the lower phase increases. Therefore, 0.01-0.02 mol/L is preferred.

[0027] image 3 In order to maintain the concentration of TX-114 at 0.01mol/L without adding acid, NaNO 3 The concentration is 0.1mol/L, C 4 mimNTf 2 The concentration is 0.001mol/L, the change of extraction rate when TOPO extracts U(VI) (concentration 0.00005mol/L) is changed. As the TOPO concentration increases, the extraction efficiency of the system for uranyl ions increases. When the TOPO concentration reaches 0.002mol/L, the extraction efficiency reaches 100%.

[0028] Without the addition of acid, the concentration of TX-114 in the aqueous solution was 0.01 mol/L and the concentration of TOPO was 0.0005 mol/L to extract U(VI) (concentration 0.00005 mol/L), and the extraction rate was determined. Take uranyl ion extraction rate (E) and C 4 mimNTf 2 Concentration plot, see the result Figure 4. by Figure 4 It can be seen that without adding acid, when the concentration of TX-114 in the aqueous solution is 0.01mol/L and the concentration of TOPO is 0.0005mol/L to extract 0.00005mol/L U(VI), C 4 mimNTf 2 When the concentration increases, the extraction efficiency of the system for uranyl ions increases, when C 4 mimNTf 2 When the concentration reaches 0.003mol/L, the extraction efficiency is close to 90%.

[0029] Using TX-114 concentration of 0.01mol/L, TOPO concentration of 0.0005mol/L, C 4 mimNTf 2 When the system with a concentration of 0.001mol/L extracts 0.00005mol/L U(VI), Th(IV), the extraction efficiency varies with the concentration of nitric acid in the aqueous phase, such as Figure 5 Shown. To extract UO 2 2+ For example, when no other acid is present, the pH of the solution is about 6. In the presence of TOPO alone, as the acidity increases, the extraction rate of U(VI) increases, when the acidity is greater than 1mol·dm -3 When, the extraction rate of uranyl ions is reduced. When C 4 mimNTf 2 After adding the extraction system (TOPT-IL-U curve in the figure), the change trend of the extraction rate with the change of acidity is the same as that of the system without ionic liquid, but the extraction rate is maintained above 60%. In general, the TOPO cloud point extraction system with ionic liquids can extract U(VI) and Th(IV) in a larger acidity range.

[0030] When using the method of the present invention, a certain ionic strength must be ensured in the extraction system to achieve phase separation. Using TX-114 concentration of 0.01mol/L, TOPO concentration of 0.0005mol/L, C 4 mimNTf 2 When the system with a concentration of 0.001mol/L extracts 0.00005mol/L U(VI), the extraction efficiency changes with the concentration of sodium nitrate in the aqueous phase, such as Image 6 Shown. As the salinity of the water phase increases, the extraction efficiency of uranyl ions increases. When NaNO 3 The concentration is 0.05mol/L (ionic strength is about 0.05mol/L), the extraction rate of U(VI) is 60%, when NaNO 3 When the concentration is greater than 0.5mol/L (ionic strength greater than 0.5mol/L), the extraction rate is basically unchanged.