Solid-liquid process for extraction of radionuclides from waste solutions

Abstract

The invention related to a complexing system for extracting a radionuclide from a waste water solution including calix[n]arene groups on the surface of a porous conducting material.

Claims

1. A complexing system for extracting a radionuclide from a waste solution comprising calixarene groups covalently bonded to the surface of a porous conducting material, n being equal to 4, 6 or 8, provided that the porous conducting material is not a dispersable and/or particulate material.

2. The method of claim 1, wherein the porous conducting material is a conducting-fiber material.

3. The complexing system of claim 2, wherein the conducting-fiber material is a carbon-fiber material.

4. The complexing system of claim 3, wherein the carbon-fiber material is selected from carbon felts.

5. The complexing system of claim 1, wherein the calixarene groups are covalently bonded via C(O)NH, NHC(O), or CC.

6. The complexing system of claim 1, wherein the calixarene group is a calixarene-crown ether group.

7. The complexing system of claim 1, wherein the calixarene group is calixarene-crown-6 ether group.

8. The complexing system of claim 1, wherein the calixarene group is a 1,3-alternate calixarene-crown-6 conformer group.

9. A method for preparing the complexing system of claim 1 comprising: i) activating a porous conducting material by applying an electric potential sufficient to allow the grafting of a radical precursor group; ii) reacting the activated porous conducting material with a compound of formula (II), thereby obtaining a modified porous conducting material;
W-L-V(II) wherein V is a radical precursor group; W is selected from the group consisting of F, Cl, Br, I, OH, NHR.sub.10, C(O)H, C(O)Hal and C(O)OR.sub.9, L is spacing group and selected from (CH.sub.2).sub.r, C.sub.3-C.sub.10 cycloalkylene or C.sub.3-C.sub.10 arylene, R.sub.9, R.sub.10 are each independently selected from H or (C.sub.1-C.sub.6) alkyl, r is an integer selected from 1 to 20; iii) grafting the modified porous conducting material with a compound of formula (Ia): ##STR00012## wherein: R.sub.1 is selected from the group consisting of X(C.sub.2H.sub.4X).sub.m and X(C.sub.2H.sub.4X).sub.p/2YX(C.sub.2H.sub.4X).sub.p/2; X is independently O or NH; m=3, 4, 5 or 6; p=2 or 4; Y is C.sub.3-C.sub.10 cycloalkylene or C.sub.6-C.sub.10 arylene; R.sub.2-R.sub.5 are each independently H or C.sub.1-C.sub.6 alkyl; L.sub.1, L.sub.2 are spacing groups and are each independently selected from the group consisting of (CH.sub.2).sub.q, C.sub.3-C.sub.10 cycloalkylene and C.sub.3-C.sub.10 arylene; Z.sub.1, Z.sub.2 are grafting groups and are each independently selected from the group consisting of F, Cl, Br, I, OHNH.sub.2, C(O)H, C(O)Hal and C(O)OR.sub.8; R.sub.8 is independently H or (C.sub.1-C.sub.6) alkyl; q is an integer ranging from 1 to 12.

10. A method for preparing the complexing system of claim 1 comprising the steps of: i) activating a porous conducting material by applying on the material an electric potential sufficient to allow the grafting of a radical precursor group; ii) grafting the activated material with a compound of formula (Ib), ##STR00013## wherein R.sub.1 is selected from that group consisting of X(C.sub.2H.sub.4X).sub.m and X(C.sub.2H.sub.4X).sub.p/2YX(C.sub.2H.sub.4X).sub.p/2; X is independently O or NH; m=3, 4, 5 or 6; p=2 or 4; Y is C.sub.3-C.sub.10 cycloalkylene or C.sub.6-C.sub.10 arylene; R.sub.2-R.sub.5 are each independently H or C.sub.1-C.sub.6 alkyl; L.sub.1, L.sub.2 are spacing groups and are each independently selected from the group consisting of (CH.sub.2).sub.q, C.sub.3-C.sub.10 cycloalkylene and C.sub.3-C.sub.10 arylene; Z.sub.3, Z.sub.4 are each independently a group M-L-V, M is independently O or NR.sub.10; L is spacing group selected from the group consisting of (CH.sub.2).sub.r, C.sub.3-C.sub.10 cycloalkylene and C.sub.3-C.sub.10 arylene; V is a radical precursor group; R.sub.10 is H or (C.sub.1-C.sub.6) alkyl.

11. A method for extracting radionuclides from a waste solution, said method comprising the step of: i) contacting a volume of a waste solution with the complexing system according to claim 1; optionally ii) contacting the complexing system containing a portion of radionuclide obtained at step i), with a volume of a stripping solution in acidic conditions, thereby removing the complexed radionuclide from said complexing system into the stripping solution, to make the complexing system available for reuse; and optionally iii) repeating steps i) and ii).

12. The method of claim 11, wherein the radionuclides are cesium and/or strontium.

13. The method of claim 11, wherein the waste solution is charged with competing alkali metal cations.

14. The method of claim 11, wherein the acidic conditions in step ii) are obtained by applying an electric potential difference on the porous conducting material of the complexing system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Figures

(1) FIG. 1: The electrochemical deposition of diazonium salt on gold plate surface.

(2) FIG. 2: Current-potential characteristic recorded during grafting of diazonium salts on gold substrate.

(3) FIG. 3: Current-potential characteristic recorded during grafting of diazonium salts on carbon felts.

(4) FIG. 4: Calixarene 1 grafted to the gold surface.

(5) FIG. 5: XPS scans of the Na+ and Cs+ regions for gold surface containing calixarene 3.

(6) FIG. 6: Cs.sup.133 NMR spectra.

(7) FIG. 7: Na.sup.23 NMR spectra.

(8) FIG. 8: Simplified scheme of SOLIEX demonstrator model.

(9) FIG. 9: Extraction of Cs by carbon felts containing calixarene 4 from water media.

DETAILED DESCRIPTION

Examples

(10) The following description and examples provide details of the manner in which the embodiments of the present invention can be made and used to effectively remove Cs from the contaminated solutions to be purified.

(11) Calix[n]arene Ligand Synthesis.

(12) A series of gold plates and carbon felts modified with calixarenes 1, 2 and 3 (Scheme 1) were prepared to accomplish the Cs complexation tests in water media.

(13) ##STR00008## ##STR00009##

Synthesis of 1,3-alternate calix[4]arene-crown-6 Conformer with Cl Terminal Group (1 and 2)

(14) The chloroderivatives of 1,3-dialkoxycalix[4]arene-crown-6 1 and 2 were synthesized from calix[4]arene according to the following sequence (Scheme 2). The chloroderivative of 1,3-dialkoxycalix[4]arene was prepared in a 72% yield by alkylation of the unsubstituted calix[4]arene with chlorobromobutane in the presence of 2.3 equivalent of K.sub.2CO.sub.3 as a base, in refluxing CH.sub.3CN according to the classical methods of O-alkylation (J. Guillon, J.-M. Lger, P. Sonnet, C. Jarry, and M. Robba, J. Org. Chem. 2000, 65, 8283-8289). Further treatment with appropriate glycol ditosylate and an excess of Cs.sub.2CO.sub.3 in refluxing CH.sub.3CN gave the calix[4]arenes-crown-6 1 and 2 in the 1,3-alternate conformation.

(15) ##STR00010##

Synthesis of chloroderivative of 1,3-dialkoxycalix[4]arene

(16) To a suspension of calix[4]arene (4.71 mmol, 1.0 g) in CH.sub.3CN (100 mL) were added bromochlorobutane (23.56 mmol, 2.71 ml) and K.sub.2CO.sub.3 (4.71 mmol, 0.651 g) and the reaction mixture was stirred under reflux for 12 h. The solvent was then removed under reduced pressure and the residue quenched with 100 mL of 10% HCl and 200 mL of CH.sub.2Cl.sub.2. The organic phase was separated and washed twice with distilled water (2100 mL) and 100 ml of brine. CH.sub.2Cl.sub.2 was dried over Mg.sub.2SO.sub.4 and distilled off to afford a solid which was crystallized from CH.sub.2Cl.sub.2-MeOH to give pure chloroderivative of 1,3-dialkoxycalix[4]arene: yield 89%; H NMR (CDCl.sub.3) 7.94 (s, 2H, OH), 7.06 and 6.89 (d, J=7.34 Hz, 4H each, ArH meta), 6.76-6.63 (m, 4H, ArH para), 4.26 (d, J=13.0 Hz, 4H, ArCH.sub.2Ar), 4.05-4.01 (m, 4H, CH.sub.2O), 3.78-3.74 (m, 4H, CH.sub.2Cl), 3.39 (d, J=13.0 Hz, 4H, ArCH.sub.2Ar), 2.26-2.18 (m, 8H, CH.sub.2). HRMS (CI, NH.sub.3): M Calcd. 624.6 (MNH.sub.4.sup.+), found 624.3.

Synthesis of 1,3-alternate calix[4]arene-crown-6 Conformer with Cl Terminal Group 1 and 2

(17) Chloroderivative of 1,3-dialkoxycalix[4]arene (0.425 g; 1.00 mmol), K.sub.2CO.sub.3 (1.380 g; 10.00 mmol), ditosylate (0.691 g; 1.00 mmol), and acetonitrile (100 mL) were refluxed for 12 h. The solvent was then removed under reduced pressure and the residue quenched with 100 mL of 10% HCl and 200 mL of CH.sub.2Cl.sub.2. The organic phase was separated and washed twice with distilled water (2100 mL) and 100 ml of brine. CH.sub.2Cl.sub.2 was dried over Mg.sub.2SO.sub.4 and distilled off to afford a solid which was crystallized from CH.sub.2Cl.sub.2-Me.sub.3CN to give pure 1,3-alternate calix[4]arene-crown-6 conformer with Cl terminal group 1: yield 83%; H NMR (CDCl3) 7.08 and 7.02 (d, J=7.50 Hz, 4H each, ArH meta), 6.87-6.80 (m, 4H, ArH para), 3.79-3.29 (m, 36H, 8H, ArCH.sub.2Ar, 4H, CH.sub.2O, 4H, CH.sub.2Cl, 20H, OCH.sub.2CH.sub.2O), 1.61-1.57 (m, 4H, CH.sub.2), 1.45-1.37 (m, 4H, CH.sub.2). HRMS (CI, NH.sub.3): M Calcd. 824.8 (MNH.sub.4.sup.+), found 824.6.

(18) The 1,3-alternate calix[4] arene-crown-6 conformer 2 was synthesized in the same manner using appropriate glycol ditosylate prepared according to described procedure (Z. Asfari, V. Lamare, J.-F. Dozol, and J. Vicens, Tetrahedron Letters 1999, 40, 691-694). Yield 61%; H NMR (CDCl.sub.3) 7.06-7.02 (m, 8H, calix ArH meta), 6.99 (br S, 4H, calix ArHpara), 6.83 (t, 7.50 Hz, 2H benzoArH), 6.68 (t, 6.68 Hz, 2H benzoArH), 4.13-4.11 (m, 4H, CH2O), 3.78 (s, 8H, ArCH.sub.2Ar), 3.69-3.67 (m, 4H, CH2Cl), 3.58-3.44 (16H, OCH.sub.2CH.sub.2O), 1.64-1.60 (m, 4H, CH.sub.2), 1.50-1.44 (m, 4H, CH.sub.2). HRMS (CI, NH.sub.3): M Calcd. 872.8 (MNH.sub.4.sup.+), found 872.5.

Synthesis of 1,3-alternate calix[4]arene-crown-6 Conformer with Terminal Aromatic Amino Group (3)

(19) Calixarene 3 was prepared from chloroderivative 2 applying the classic conditions (M. Incerti et al, Chem Med Chem, 2010, 5, 1143-1149) to react the primary aliphatic amine and halogen and was used for construction of complexing system without purification.

Synthesis of 1,3-alternate calix[4]arene-crown-6 Conformer with Terminal Aromatic Amino Group (4)

(20) Calixarene 4 was prepared from 1 equivalent of chloroderivative 1 and 2.2 equivalents of paranitrophenol in DMF in the presence of 4 equivalents of K.sub.2CO.sub.3 as a base. Then the reaction was quenched with 100 mL of 10% HCl and 200 mL of CH.sub.2Cl.sub.2. The organic phase was separated and washed twice with distilled water (2100 mL) and 100 ml of brine. CH.sub.2Cl.sub.2 was dried over Mg.sub.2SO.sub.4 and distilled off to afford a solid which was reduced to the amine with H.sub.2/Pd catalyst and was used for construction of complexing system without purification.

(21) Construction of the Complexing System.

(22) Electrochemical Modification of the Conducting-Fiber Material with Organic Compounds

(23) The electrochemical deposition of organic compound to conducting-fiber material was accomplished on gold plates to have an opportunity to confirm the results of deposition by ATR analysis.

(24) The electrochemical deposition (D. Alamarguy, A. Benedetto, M. Balog, S. Noel, P. Viel, F. Le Derf, F. Houze, M. Sall and S. Palacin, Surf. Interface Anal. 2008, 40, 802-805) of hydrochloride salt of 4-aminoethylbenzene diazonium tetrafluoroborate (FIG. 1) was carried out with an EGG-PAR 273 potentiostat in three-electrode electrochemical cell under a highly controlled (argon purified) atmosphere inside a glove box. The working electrodes were the gold substrates.

(25) The reference electrode was based on the Ag|Ag.sup.+ 10.sup.2 M couple. Electrochemical analysis was done using an EG&G potentiostat, model 273 A. A solution of 5 mM of diazonium salts in anhydrous acetonitrile was used; tetraethyl ammonium perchlorate 0.05 M was used as supporting electrolyte. Two cycles of potential sweep at 20 mV.s.sup.1 were carried out between the equilibrium potential (typically of the order of 0.3 V) and 1.0 V (FIG. 2). The results of deposition were confirmed by ATR analysis.

(26) Carbon felts are preferred conductive material to form the complexing system. Carbon felts of 200 mg were modified in the same manner to create a demonstration sample for further extraction tests.

(27) The electrochemical deposition of tetrafluoroborate of 4-aminoethyl benzene diazonium tetrafluoroborate was carried out with an EGG-PAR 273 potentiostat in three-electrode electrochemical cell under a highly controlled (argon purified) atmosphere inside a glove box. Three graphite bars for mechanical pencils Bic Criterium HB of 2 mm in diameter were used as power feed. The carbon felts were introduced to electrochemical cell and pierced with graphite bars for about 100% of their thickness. The reference electrode was done by a platinum wire. 126 mg of diazonium salts was placed to the electrochemical cell; tetraethyl ammonium perchlorate 0.05 M was used as supporting electrolyte. Six cycles of potential sweep at 20 mV s.sup.1 were carried out between the equilibrium potential and 1.0 V. The voltammograms of grafting process of diazonium salts on the carbon felt surface are represented in FIG. 3.

(28) Electrochemical Deposition of the Calixarene 3 on the Surface of the Conducting Material

(29) The electrochemical deposition of calixarene-amine 3 (Scheme 1) on gold plates was carried out with an EGG-PAR 273 potentiostat in three-electrode electrochemical cell under a highly controlled (argon purified) atmosphere inside a glove box. The working electrodes were the gold substrates. The reference electrode was based on the Ag|Ag+ 10-2 M couple. Electrochemical analysis was done using a EG&G potentiostat, model 273 A. A solution of about 1 mM of diazonium salts in anhydrous acetonitrile was prepared directly in the electrochemical cell in presence of 1 equivalent of NOBF.sub.4 by one equivalent of amine group; tetraethyl ammonium perchlorate 0.05 M was used as supporting electrolyte. Two cycles of potential sweep at 20 mV s.sup.1 were carried out between the equilibrium potential (typically of the order of 0.3 V) and 1 V. The presence of calixarene 3 on gold plates was confirmed by ATR analysis.

(30) Electrochemical Deposition of the Calixarene 4 on the Surface of the Conducting Material.

(31) The diazonium salt of calixarene 4 was obtained by diazotation in classic conditions and then the molecules were bonded to conducting surfaces by the electrochemical reduction of diazonium groups.

(32) Chemical Deposition of Calix[n]arene Ligands 1 and 2 on the Surface of the Conducting Material

(33) Calixarenes 1 and 2 were grafted on premodified gold surfaces (FIG. 4) via classical reaction between its Cl and surface terminal amino groups in the presence of K.sub.2CO.sub.3 and DMF (the same protocol was applied for synthesis of 3). The presence of calixarenes 1 and 2 on the surfaces of gold plates was confirmed by ATR analysis.

(34) Calixarenes 1 and 2 were then grafted onto carbon felts surfaces via reaction between its Cl and surface NH.sub.2 terminal groups in the presence of K.sub.2CO.sub.3 and catalytic amount of KI in DMF under argon at 80 C. during 24 h. Then carbon felts were washed in demineralized water during 12 h, acetonitrile (12 h), dichloromethane (30 min) and dried under vacuum for 1 hour.

(35) Extraction of Cs.

(36) Extraction of Cs by Gold Plates Containing Calixarenes 1, 2 and 3 from Water Media in Presence of High Excess of Na Ions

(37) The calixarene modified gold plates were kept in 3 ml of selectivity test solution during 12 h at RT in 3 ml glass bottles. The complexed gold plates were then washed with demineralized water, acetonitrile and dichloromethane and dried under vacuum. The XPS analysis indicated the presence of Cs.sup.+ ions in all examined surfaces. The XPS results are collected in Table 1.

(38) The selectivity coefficient may be expressed as:
SR1/R2

(39) where R2 is the final average equivalent ratio of Na+/Cs+ ions on the 1 mm.sup.2 of surface of gold plate (determined from 3 different regions of the same plate), R1 is the initial equivalent ratio of Na.sup.+/Cs.sup.+ ions in the selectivity test solution calculated from Na.sup.+ and Cs.sup.+ concentrations. Selectivity test solution contained 4 mol/l of NaNO.sub.3 and 510.sup.3 mol/l of CsNO.sub.3 in demineralized water. Consequently, R1 (the initial equivalent ratio of Na.sup.+/Cs.sup.+ ions)=800.

(40) TABLE-US-00001 TABLE 1 $S=\frac{{\left[\mathrm{Na}\right]}_i}{{\left[\mathrm{Na}\right]}_f}\frac{{\left[\mathrm{Cs}\right]}_f}{{\left[\mathrm{Cs}\right]}_i}$ iinitial concentration ffinal concentration Calculated average ratios of Na+/Cs+ ions (R2) for 1 mm of the sample surface and selectivity (S) in all samples. Experiment code Calixarene R1 R2 S Gold plates: 2 800 very little quantity of Na+ was found => S >> 1000 1 800 1.68 476.2 3 800 Na.sup.+ wasn't found (FIG. 6) => S =

(41) Extraction of Cs by Carbon Felts Containing Calixarenes 1, 2 and 3 from Water Media in Presence of High Excess of Na Ions

(42) Calixarenes 1 and 2 were grafted onto carbon felts surfaces via reaction between its Cl and surface NH.sub.2 terminal groups in the presence of K.sub.2CO.sub.3 and catalytic amount of KI in DMF under argon at 80 C. during 24 h. Then carbon felts were washed in demineralized water during 12 h, acetonitrile (12 h), dichloromethane (30 min) and dried under vacuum for 1 hour.

(43) The calixarene modified carbon felts 1 and 2 were kept in 3 ml of selectivity test solution described above during 24 h at RT in 3 ml glass bottles. The complexed carbon felts were then washed with demineralized water (12 h), acetonitrile (12 h), dichloromethane (1 h) and dried under vacuum (12 h). The XPS analysis indicated the presence of Cs.sup.+ ions inside and outside in all examined surfaces. The average results are collected in Table 2.

(44) TABLE-US-00002 TABLE 2 Calculated average ratios of Na+/Cs+ ions (R2) for 1 mm of the sample surface and selectivity (S) in all samples. Experiment code Carbonfelts: Calixarene R1 R2 S Carbonfelt 1 (outside) 1 800 10.78 74.21 Carbonfelt 1 (inside) 1 800 10.43 76.7 Carbonfelt 2 (outside) 2 800 13.57 58.95 Carbonfelt 2 (inside) 2 800 7.38 108.40

(45) The results presented in Tables 1 and 2 for R.sub.2 (the final average equivalent ratio of Na+/Cs+ ions on the 1 mm.sup.2 of surface) demonstrate that the calixarenes grafted on surface are capable to perform the selective complexing of Cesium. R.sub.2 and S are performance criteria of the complexing system: the decrease in R2 in correlation to R1 and the increase of S (selectivity) will indicate better system performance. The analysis of these values shows that the selectivity of calixarene 2 modified with benzene moiety in its crown part (calixarenes 2 and 3) is in most cases better than selectivity of non-modified calixarene 1: these results are in accordance with data previously obtained by Dozol et al. (FR 2760236 A1) for liquid-liquid extraction of Cs ions by related calixarenes.

(46) On the other hand, sodium is common laboratory impurity most frequently detected in XPS analysis occurring due to environmental or human impacts. For carbon felts it may also be the result of insufficient washing from non-complexed Na+ ions or may remain with residual traces of water or organic solvents employed in post complexation work-up. Further Cs extraction examples are made in deuterated organic media and show absolute selectivity of calixarene of this type for Cs.sup.+ ions confirmed by Cs.sup.133 and Na.sup.23 NMR analysis.

(47) Extraction of Cs by Calixarene 1 from Organic Media in Presence of High Excess of Na Ions: Absolute Selectivity Towards Cs+ Cations

(48) The NMR study of competitive complexation of cesium and sodium picrate salts to calixarene 1 was carried out in acetonitrile-d3. Cesium and sodium picrates complexes in 10.sup.4-10.sup.1 concentrations were tested. Cs.sup.133 and Na.sup.23 NMR spectra were obtained for samples prepared in 0.6 ml of acetonitrile-d3. Calixarene 1 exhibited absolute selectivity towards Cs+ ions (FIGS. 6 and 7).

(49) TABLE-US-00003 TABLE 3 Ratios of Calixarene 1/Cs.sup.++/Na.sup.+ Cs.sup.+ ions in 0.6 mL of acetonitrile-d3. Calixarene 1 Cs+ Na+ Sample (molar ratio) (molar ratio) (molar ratio) code 1 1 1 1-1-1 1 1 10 1-1-10 1 1 100 1-1-100 1 1 1000 1-1-1000 20 1 20 20-1-20 0 1 0 free Cs+ 0 0 1 free Na+ 1 0 1000 calixarene 1 with excess of Na+

(50) Recycling of the Complexing Structure.

(51) Expulsion of complexed ions may be accomplished by chemical or electrically assisted means.

(52) Example of chemical expulsion: the Cs+ complexed carbon felts 1 and 2 were immersed for 12 h in 3 ml of 0.001 to 1M HCl solution. Then they were washed in demineralized water (30 min), acetonitrile (30 min), dichloromethane (30 min) and dried under vacuum for 1 hour. The XPS analysis indicated the complete absence of Cs+ ions inside and outside in all examined surfaces.

(53) Expulsion by Electrically Assisted Means:

(54) electro-assisted pH-switchable mechanism is shown in the following scheme.

(55) ##STR00011##

(56) Such a phenomenon within the carbon felts complexed with Cs ions is equivalent to an acidic washing. Such electro-oxidizing strategy was already used to assist the regeneration of copper complexed by basic pyridine groups of the P4VP films by P. Viel et al (Viel, P.; Dubois, L.; Lyskawa, J.; Sall, M.; Palacin, S. Applied Surface Science 2007, 253, 3263-3269.)

(57) Electrochemistry was carried out with a Princeton Applied Research Inc. potentiostat model 263A from EG&G in three-electrode electrochemical cell. The working electrode was Cs complexed carbon felt (1 then 2, see Table 2). The reference electrode was the platinum wire of 0.5 mm in diameter; the counter electrode was the graphite plate. The carbon felts were subjected to anodic treatment in H.sub.2O DI solution of MgSO4, 0.9 g/l during 300 s. A galvanostatic regime with an anode current density of 0.033 mA/cm.sup.2 was used for the anodization. The XPS analysis indicated the complete absence of Cs+ ions inside and outside in all examined carbon felts surfaces: the complexing system is reversible.

(58) The recycled carbon felts were reintroduced to selectivity test solution during 12 h at RT in 3 ml glass bottles. Then they were washed in demineralized water during 30 min, acetonitrile (30 min), dichloromethane (30 min) and dried under vacuum for 1 hour. The XPS analysis indicated the presence of Cs+ ions in all examined surfaces: the complexing system is reusable.

(59) A Demonstrator Model for Construction of the Complexing System, Decontamination of Liquid Wastes and Regeneration of the Complexing System.

(60) A demonstrator model with a total working volume of about 1 liter was constructed to scale-up the SOLIEX process (see FIG. 8) allowing the whole process: construction of the complexing system, decontamination of liquid wastes and regeneration of the complexing felts to be accomplished in situ in the <<active surface module>>. SOLIEX process can be run through the following steps: i) Preparation of the complexing surface in the active surface module: electrochemical grafting of carbon felts with molecular traps (calixarenes) in the active surface module and further rinsing of the surface from grafting solution; ii) Passing the waste solution through the complexing system in the active surface module (carbon felt grafted with calixarenes); iii) On-demand recycling of the complexed radionuclide to make the complexing system available for reuse: contacting the cation-loaded complexing system with a volume of a stripping solution in acidic conditions or electrochemical cation expulsion into the aqueous stripping solution; iv) Repeating steps i) and ii).

(61) Extraction of Cs by Carbon Felts Containing Calixarene 4 from Water Media.

(62) Three series of grafting/decontamination experiments were carried out for CsNO.sub.3 10.sup.4-10.sup.5 M non-radioactive solutions of 1 L using grafted MERSEN carbon felts; the detected average complexed Cs.sup.+ mass was about 9 mg by carbon felt of about 14 g.

(63) The set of carbon felts (diameter of 14 cm) was prepared in the electrochemical cell using 8.8 g of TEAP (supporting electrolite) and 212 mg of calixarene 4 solution in 1 L of acetonitrile by circulating flow of the left module. The carbon felts were then washed by flow of acetonitrile and water to remove the non-grafted calixarene molecules. Three batches of 1 L of initial 10.sup.4 M cesium aqueous solution were prepared using commercially available cesium nitrate to accomplish the decontamination tests.

(64) The batches were then circulated through the carbon felts located in the electrochemical cell.

(65) Atomic absorption spectroscopy (AAS) was successfully implemented for analysis of Cs solutions before and after extraction process to estimate the complexing capacity of carbon felts. The set of the decontamination experiments was accomplished; the initial and resulting concentrations of cesium nitrate solutions are presented in table below and on FIG. 9:

(66) TABLE-US-00004 Initial Solution, mM 3 min 5 min 10 min 15 min 20 min 35 min 50 min 80 min 0.1157 0.103 0.0941 0.0898 0.0811 0.0820 0.0728 0.0687 0.0680 0.1092 0.0935 0.0940 0.0878 0.0841 0.0824 0.0742 0.0727 0.0659 0.1098 0.0971 0.0941 0.0843 0.0803 0.0820 0.0760 0.0705 0.0637 Average concen- 0.098 0.094 0.0873 0.082 0.0822 0.072 0.0706 0.0659 trations: 0.116

REFERENCES

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