Kinetics of extraction of Eu 3+ ion by TODGA and CyMe 4 -BTBP studied using the RMC technique

Transcription

1 Kinetics of extraction of Eu 3+ ion by TDGA and CyMe 4 -BTBP studied using the RMC technique Trong-Hung VU and Jean-Pierre SIMI P.M. Curie university (Paris 6) / CRS, France. -

2 utline of the presentation Introduction Rotating membrane cell (RMC) technique Description + principle Closed capillary technique Extraction kinetics with TDGA/TBP (i-saex) Extraction kinetics with CyMe 4 -BTBP (r-saex) Conclusion

3 Introduction An-Ln separation process Increasing need of extraction kinetics data: process modelling (counter-current tests) lack of kinetics data better understanding of extraction mechanism bjective: => extraction kinetics (Rotating Membrane Cell - RMC)

4 Rotating Membrane Cell (RMC) Membrane

5 Rotating Membrane Cell (RMC) Phase A (membrane) (ion to be extracted) V A ~ 3-5 µl ω PVDF PTFE Membrane Diffusion layer δ 120 µm 8 mm Phase B x V B = 3-5 ml Good control of hydrodynamics and transport : - Within membrane : Pure diffusion (Fick s law) - In outer phase : Rotating disc hydrodynamics (Levich equation)

6 Rotating Membrane Cell (RMC) Proportion of extracted matter : -ln(1-p) P(t) 1- exp(- t /τ ) => -ln [1- P(t) ] = 1/τ * t = straight line DL Slope 1/τ t τ = τ aq + τ f + τ org τ aq = L 2 / 3D memb τ f = L / Forward interfacial rate constant τ org = σ L δ / KD org Values of these parameters determined experimentally Membrane Bulk k r x x

7 Measurement with Rotating Membrane Cell (RMC) Extraction >< Stripping Membrane aqueous Membrane organic Ion to be extracted Ion to be stripped Bulk phase organic Bulk phase aqueous

8 Rotating Membrane Cell (RMC) DL Extraction kinetics 1.00 DL Stripping kinetics -ln(1-p(t)) y = x R 2 = ln(1-p(t)) y = x R 2 = Experiment Experiment 0.20 Diffusional limit 0.20 Diffusional limit Time t (s) Time t (s) Extraction ( 152 Eu 3+ ) Stripping ( 152 Eu 3+ ) k ext = 5.8 ± (cm/s) k ext = 6.6 ± (cm/s) Rotation speed (RMC) = 600 rpm, T = 22 ± 1 C Aqueous: 0.01 M DTPA M malonic acid M a 3 + ph 2 rganic: 0.2 M TDGA M TBP in HTP (pre-equilibrated)

9 Rotating Membrane Cell (RMC) Proportion of extracted matter : -ln(1-p) P(t) 1- exp(- t /τ ) => -ln [1- P(t) ] = 1/τ * t = straight line DL Slope 1/τ t τ = τ aq + τ f + τ org τ aq = L 2 / 3D memb τ f = L / Forward interfacial rate constant τ org = σ L δ / KD org Values of these parameters determined experimentally Membrane Bulk k r x x

10 Diffusion coefficient (D) Closed capillary technique : 152 Eu(III) in 3.0 mol/l H 3 solution 1 P D = cm 2 /s Silica capillary L = 3.0 cm φ = 0.5 mm Scintillation plastic days t (h) D = k B T/ 6πηr Hydrodynamic radius: r = 5.6 Å [ J. Sol. Chem. 15 (1986) 1015 ]

11 utline of the presentation Introduction Rotating membrane cell (RMC) technique Description + principle Closed capillary technique Extraction kinetics with TDGA/TBP (i-saex) Extraction kinetics with CyMe 4 -BTBP (r-saex) Conclusion + perspective

12 Extraction kinetics of Eu 3+ with TDGA/TBP Effect of aqueous nitric acid Distribution ratio K(Eu) K(Eu) (cm/s) P TBP TDGA [H 3 ] aq rganic phase : 0.2 mol/l TDGA mol/l TBP in TPH Aqueous phase : variable H 3 Fast kinetics - Kinetics increases strongly with [H 3 ] aq Eu 3+ + ntdga yh 3 M( 3 ) 3 (TDGA) n (H 3 ) y Distribution ratio : K(Eu) ~ k equil [TDGA] n [ 3 ] 3 [H 3 ] y -TDGA : surfactant (ring method, tensiometer)

13 Extraction kinetics of Eu 3+ with TDGA/TBP Effect of DTPA concentration Distribution ratio K(Eu) K(Eu) (10 6 cm/s) H TDGA P TBP H H H H [DTPA] (mol/l) 0.0 H 5 DTPA Diethylenetriamine pentaacetic acid (pk A = I=0.1) - DTPA : complexing agent (Eu-DTPA complexation) - Slower kinetics than in H 3 aqueous solution H H Malonic acid (pk A = I=0.1) rganic phase : 0.2 mol/l TDGA mol/l TBP in TPH Aqueous phase : 1.0 mol/l malonic acid + variable DTPA mol/l a 3 + ph 2

14 Extraction kinetics of Eu 3+ with TDGA/TBP Effect of aqueous ph Distribution ratio K(Eu) K(Eu) (10 6 cm/s) H H H H H H 5 DTPA Diethylenetriamine pentaacetic acid (pk A = I=0.1) ph aq ph : H 5 DTPA 5H + + DTPA 5- (Eu complexation) Great sensitivity of the extraction performances vs ph aq rganic phase : 0.2 mol/l TDGA mol/l TBP in TPH Aqueous phase : 1.0 mol/l malonic acid mol/l DTPA mol/l a 3 + variable ph

15 Extraction kinetics of Eu 3+ with TDGA/TBP Effect of a kf Distribution ratio K(Eu) K(Eu) (10 6 cm/s) [a 3 ] (mol/l) salting-out effect on K - o clear effect on kinetics rganic phase : 0.2 mol/l TDGA mol/l TBP in TPH Aqueous phase : 1.0 mol/l malonic acid mol/l DTPA + variable a 3 + ph 2

16 utline of the presentation Introduction Rotating membrane cell (RMC) technique Description + principle Closed capillary technique Extraction kinetics with TDGA/TBP (i-saex) Extraction kinetics with CyMe 4 -BTBP (r-saex) Conclusion + perspective

17 Extraction kinetics of Eu 3+ with CyMe 4 -BTBP K(Eu) kf *10 6 (10-6 cm/s) CyMe 4 -BTBP ctanol Cyclohexanone 3-methyl cyclohexanone 4-methyl cyclohexanone - Very slow kinetics in 1-octanol - Fast kinetics in cyclohexanone but high mutual solubility cyclohexanone H 3 water rganic phase : 0.01 mol/l CyMe 4 -BTBP in different diluent Aqueous phase : 2.0 mol/l H 3

18 Extraction kinetics of Eu 3+ with CyMe 4 -BTBP rganic phase : CyMe 4 -BTBP in 1-octanol 2.0 mol/l H 3 Aqueous phase : H 3 Distribution ratio K(Eu) mol/l CyMe 4 -BTBP K(Eu) *10 6 (cm/s) kf *10 6 (cm/s) K(Eu) Slope H 3 aq (mol/l) Kinetics increases with H 3aq but very slow -Slopes ~ 2 => (BTBP/Eu) ext : 2/1 => 2 nd order dependance

19 Extraction kinetics of Eu 3+ with CyMe 4 -BTBP rganic phase : 0.01 mol/l CyMe 4 -BTBP + (TDGA or DMDHEMA) in 1-octanol Aqueous phase : 2.0 mol/l H K(Eu) kf * CyMe 4 -BTBP TDGA BTBP 0.01M alone BTBP 0.01M + TDGA 0.003M BTBP 0.01M + TDGA 0.005M TDGA 0.005M alone BTBP 0,01M + DMDHEMA 0,25M DMDHEMA TDGA or DMDHEMA phase-transfer catalyst : acceleration of kinetics TDGA > DMDHEMA

20 Conclusion RMC technique : measurement of extraction kinetics (interfacial reaction rate constants) diffusive contribution taken into account small volume (3-5 µl) of organic phase (if in membrane) TDGA extractant : aqueous nitric acid : accelerates extraction kinetics DTPA solutions : slower extraction kinetics CyMe 4 -BTBP slow kinetics phase-transfer catalyst : TDGA and DMDHEMA confirmation of the previous observations in ACSEPT project

21 Thank you for your attention