Synthesis and Characterization of a New Polymer-Based Supramolecular Recognition Material and its Adsorption for Cesium

A novel macroporous polymer-based 25,27-bis(iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/XAD-7, was synthesized. It was performed by vacuum impregnation and immobilization of BiPCalix[4]C6 into the pores of the macroporous XAD-7 particles. The composition and structure were characterized using SEM, BET, TG-DSC, FT-IR, and XRD, respectively. The adsorption of some typical metals contained in highly active liquid waste (HLW) such as Ru(III), Mo(VI), K(I), Rb(I), Cs(I), Sr(II), Ba(II), La(III), and Y(III) onto the BiPCalix[4]C6/XAD-7 materials was investigated. The effects of the HNO₃ concentration and contact time on the adsorption of the tested metals were evaluated. It was found that at the optimum concentration of 4.0 M HNO₃, BiPCalix[4]C6/XAD-7 exhibited excellent adsorption ability and high selectivity for Cs(I) over all the other tested metals, which showed weak or almost no adsorption except Rb(I). It demonstrated that application of the polymer-based supramolecular recognition material, BiPCalix[4]C6/XAD-7, in partitioning of Cs(I) from HLW is promising.     

Adsorption of cesium and some typical elements on a novel solid-state macroporous silica-calix[4]arene material

25,27-Bis(1-hexyloxy)-calix[4]arene-26,28-crown-6 (HexylCalix[4]C6) was synthesized. A new macroporous silica-based composite material, HexylCalix[4]C6@SiO₂, was prepared through impregnation and immobilization of HexylCalix[4]C6 into the SiO₂-P particles. The adsorption of 17 species of typical metals onto HexylCalix[4]C6@SiO₂ in the range of 0.3–5.0 M HNO₃ was investigated. The material exhibited strong adsorption ability and excellent selectivity for Cs(I) over all the tested metals except for Rb(I) and Pd(II). The optimum HNO₃ concentration and the adsorption mechanism of Cs(I) onto the material were discussed. The solubility of HexylCalix[4]C6@SiO₂ in aqueous phase was evaluated by total organic carbon (TOC). The technical feasibility of application of Hexyl Calix[4]C6@SiO₂ in Cs(I) separation was confirmed.     

Adsorption behavior and radiation effects of a silica-based (Calix(4)+Dodecanol)/SiO2-P adsorbent for selective separation of Cs(I) from high level liquid waste

A macroporous silica-based (Calix[4]+Dodecanol)/SiO₂-P absorbent for separation of Cs(I) from HNO₃ solution was prepared by impregnating the 1,3-[(2,4-Diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene and its molecule modifier 1-dodecanol into a macroporous silica/polymer composite support. To establish its application into partitioning of Cs(I) from High Level Liquid Waste (HLLW), the adsorption properties and radiation effects on the adsorbent were investigated. The adsorbent showed a relatively large distribution coefficient of Cs(I) and fast equilibrium time in simulated HLLW. Additionally, the adsorbent under the gamma-ray field was found to be able to selectively adsorb Cs(I) with similar behavior to the adsorption without irradiation up to at least 170 kGy.     

Preparation of macroporous silica-based crown ether materials for strontium separation

To develop a separation process of Sr(II), a macroporous silica-based 4,4′,(5′)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) polymeric material, (DtBuCH18C6+Oct)/SiO₂-P, was synthesized by impregnating and immobilizing DtBuCH18C6 and 1-octanol into the pores of the macroporous SiO₂-P particles support. DtBuCH18C6 was modified with 1-octanol through hydrogen bonding. The adsorption of simulant elements of some typical fission products Ru(III), Pd(II), Ba(II), Mo(VI), La(III), Y(III), Sr(II), Cs(I) and those of non-fission products Na(I) and K(I) onto (DtBuCH18C6+Oct)/SiO₂-P were studied at 298 K. The effects of the HNO₃ concentration in a range of 0.1–5.0 M and contact time on the adsorption were investigated. (DtBuCH18C6+Oct)/SiO₂-P showed excellent adsorption ability and high selectivity for Sr(II) over all of the tested metals except Ba(II). Partitioning of Sr(II) from a 2.0 M HNO₃ solution containing ~5.0 × 10^?3 M of the tested metals was conducted utilizing (DtBuCH18C6+Oct)/SiO₂-P packed column. Pd(II), Mo(VI), Y(III), La(III), Ru(III), K(I), Cs(I), and Na(I) showed no adsorption and flowed into effluent along with 2.0 M HNO₃. Sr(II) was retained on (DtBuCH18C6+Oct)/SiO₂-P and was eluted effectively by H₂O, while Ba(II) showed similar elution behavior. The bleeding of total organic carbon leaked from (DtBuCH18C6+Oct)/SiO₂-P was evaluated. It was demonstrated that the macroporous silica-based (DtBuCH18C6+Oct)/SiO₂-P materials are promising in separation of Sr(II) from high level radioactive waste.     

Chromatographic partitioning of cesium by a macroporous silica‐calix[4]arene‐crown supramolecular recognition composite

A macroporous silica‐based 1,3‐[(2,4‐diethyl‐heptylethoxy)oxy]‐2,4‐crown‐6‐calix[4]arene (Calix[4]arene‐R14) supramolecular recognition polymeric composite, (Calix[4]+Oct)/SiO₂‐P, was synthesized. It was performed by impregnating and immobilizing Calix[4]arene‐R14 and n‐octanol into the pores of the macroporous SiO₂‐P particles support. n‐Octanol was used to modify Calix[4]arene‐R14 through hydrogen bonding. The effect of eight typical fission products contained in highly active liquid waste (HLW) on the adsorption of Cs(I), one of the heat generators, was investigated at 298 K by examining the effect of contact time and the HNO₃ concentration in a range of 0.3–7.0 M. (Calix[4]+Oct)/SiO₂‐P showed excellent adsorption ability and high selectivity for Cs(I) at 4.0 M HNO₃ over the tested elements. The partitioning of Cs(I) from a simulated HLW was operated by (Calix[4]+Oct)/SiO₂‐P packed column. Cs(I) was able to be effectively eluted by water and separated from the tested metals. It is demonstrated that (Calix[4]+Oct)/SiO₂‐P is promising to apply in chromatographic separation of Cs(I) from HLW. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Adsorption Behavior of Sr(II) and some Typical Co‐existent Metals Contained in High Level Liquid Waste onto a Modified Macroporous Silica‐Based Polymeric DtBuCH18C6 Composite

To significantly reduce the bleeding of 4,4′,(5′)‐di(tert‐butylcyclohexano)‐18‐crown‐ 6 (DtBuCH18C6), an improved novel macroporous silica‐based polymeric composite (DtBuCH18C6+TBP)/SiO₂‐P was synthesized. It was performed by impregnating and immobilizing DtBuCH18C6 into the pores of the SiO₂‐P particles via the molecular modification of DtBuCH18C6 with a tri‐n‐butyl phosphate (TBP) through hydrogen bonding. The adsorption of a few typical simulated fission and non‐fission products Pd(II), La(III), Na(I), K(I), Sr(II), Ba(II), Ru(III), Cs(I), Mo(VI), and Y(III) onto (DtBuCH18C6+TBP)/SiO₂‐P was investigated at 323 K. It was done by examining the effect of contact time and the HNO₃ concentration in a range of 0.1–5.0 M. Sr(II), one of the main heat emitting nuclides, showed optimum adsorption onto (DtBuCH18C6+TBP)/SiO₂‐P in 2.0 HNO₃, while others showed very weak or almost no adsorption except a portion of Ba(II). The leaching of TBP and DtBuCH18C6 from (DtBuCH18C6+TBP)/SiO₂‐P was evaluated. The average content of DtBuCH18C6, 298.7 ppm, leached from (DtBuCH18C6+TBP)/SiO₂‐P in 2.0 M HNO₃ at 323 K was obviously lower than that of 797.3 ppm leached from DtBuCH18C6/SiO₂‐P at 298 K. The significant reduction of DtBuCH18C6 leaching from its macroporous silica‐based polymeric adsorbent was achieved. It is useful for the recycle operation of the silica‐based DtBuCH18C6 impregnated polymeric composite in chromatographic partitioning of Sr(II) from high level liquid waste (HLLW).     

Impregnation synthesis of a novel macroporous silica-based crown ether polymeric material modified by 1-dodecanol and its adsorption for strontium and some coexistent metals

4,4′,(5′)-Di-(tert-butylcyclohexano)-18-crown-6(DtBuCH18C6) is a chelating agent having high selectivity mostly for Sr(II). To significantly reduce its leakage by molecular modification, a macroporous silica-based DtBuCH18C6 polymeric composite (DtDo/SiO₂–P) was synthesized. It was performed by impregnating and immobilizing DtBuCH18C6 and 1-dodecanol molecules into the pores of the SiO₂–P particles utilizing an advanced vacuum sucking technique. The adsorption of a few fission and non-fission products Sr(II), Ba(II), Cs(I), Ru(III), Mo(VI), Na(I), K(I), Pd(II), La(III), and Y(III) onto DtDo/SiO₂–P was investigated. It was done by examining the effects of contact time and the HNO₃ concentration in a range of 0.1–5.0 M at 298 K. At the optimum concentration of 2.0 M HNO₃, DtDo/SiO₂–P exhibited strong adsorption ability and high selectivity for Sr(II) great over all of the tested elements, which showed very weak or almost no adsorption except Ba(II). Meanwhile, It was found that the quantity of total organic carbon (TOC) leaked from DtDo/SiO₂–P in 2.0 M HNO₃, 187.5 ppm, was lower than 658.4 ppm that leaked from DtBuCH18C6/SiO₂–P, which was not modified. This was ascribed to the effective association of DtBuCH18C6 and 1-dodecanol through intermolecular interaction. The reduction of DtBuCH18C6 leakage by molecular modification with 1-dodecanol was achieved. It was of great benefit to application of DtDo/SiO₂–P in chromatographic partitioning of Sr(II), one of the main heat generators, from high level liquid waste (HLLW) in reprocessing of nuclear spent fuel in the MAREC (Minor Actinides Recovery from HLLW by Extraction Chromatography) process developed recently.     

Removal of cesium by countercurrent solvent extraction with a calix[4]crown derivative

A macrocyclic 1,3-di(1-dodecyloxy)-2,4-crown-6-calix[4]arene (DodCalix[4]C6) was synthesized and characterized. The extraction of Cs(I) and more than 10 typical metals with DodCalix[4]C6/octanol in HNO₃ medium was investigated. DodCalix[4]C6 exhibited strong extraction ability and high selectivity for Cs(I) over others except for Rb(I). The optimum acidity in Cs(I) extraction was 3.0 M HNO₃. The Cs(I) separation from a simulated highly active liquid waste by five-stage countercurrent extraction was performed. The extraction efficiency of Cs(I) for five-stage extraction was greater than 99%. The effective partitioning of Cs(I) by DodCalix[4]C6/octanol through multistage countercurrent extraction was achieved.     

Adsorption of Some Typical Fission Products onto a Novel Macroporous Silica-based Dialkyl Derivative of Pyridine Impregnated Material

A macroporous silica-based multidentate soft-ligand 2,6-bis(5,6-di(iso-hexyl)-1,2,4-triazine-3-yl)pyridine (BDIHTP) material, BDIHTP/SiO₂-P, was synthesized by impregnating and immobilizating BDIHTP into the pores of the SiO₂-P particles. The adsorption behavior of some typical fission products Mo(VI), Zr(IV), Ru(III), Pd(II), Rh(III), and a part of rare earths La(III), Ce(III), Nd(III), Eu(III), Gd(III), Dy(III), Er(III), Yb(III), and Y(III) contained in highly active liquid waste (HLW) onto BDIHTP/SiO₂-P was investigated. The effects of contact time and the concentration of HNO₃ in the range of 0.3 M to 5.0 M were examined. The BDIHTP/SiO₂-P materials showed excellent adsorption ability and high selectivity for Pd(II) greater than all of the tested metals. It was contributed to the effective complexation of Pd(II), a soft-Lewis acid and an electron-pair acceptor, with BDIHTP, a soft-Lewis base and an electron-pair donor. The chromatographic partitioning of the tested metals from 1.0 M HNO₃ by BDIHTP/SiO₂-P packed column was performed. Pd(II) was effectively eluted with 0.2 M thiourea-0.1 M HNO₃ and then separated from the others. The results are beneficial to partitioning of the long-lived minor actinides and Pd(II) together from HLW by the BDIHTP/SiO₂-P materials.     

Preparation of a macroporous silica–pyridine multidentate material and its adsorption behavior for some typical elements

A new macroporous silica‐based‐polymer (SiO₂‐P) soft ligand composite material, 2,6‐bis(5,6‐di(iso‐butyl)‐1,2,4‐triazine‐3‐yl)pyridine (BDIBTP/SiO₂‐P), was synthesized by impregnation and immobilization of BDIBTP and 1‐octanol molecules into the pores of the SiO₂‐P particles. The impact of some typical alkali metal and alkaline earths Cs(I), Na(I), K(I), Rb(I), Sr(II), and Ba(II) containing in highly active liquid waste (HLW) on the adsorption of Pd(II) onto BDIBTP/SiO₂‐P was studied. It was performed by examining the effects of contact time and the HNO₃ concentration in the range of 0.3–7.0 M. BDIBTP/SiO₂‐P showed strong adsorption ability and high selectivity for Pd(II) over all the tested metals. The chromatographic partitioning of Pd(II) from a simulated HLW solution was conducted by BDIBTP/SiO₂‐P packed column. Pd(II) was effectively eluted with 0.2 M thiourea–0.1 M HNO₃. The others showed no adverse impact on separation of Pd(II). The results are beneficial to partitioning of minor actinides and Pd(II) together from HLW by BDIBTP/SiO₂‐P in the MPS process developed. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Adsorption Behaviors of Platinum Group Metals in Simulated High Level Liquid Waste Using Macroporous (MOTDGA-TOA)/SiO2-P Silica-based Absorbent

As fundamental research for separation of platinum group metals (PGMs) from high level liquid waste (HLLW) by macroporous silica-based adsorbent, (MOTDGA-TOA)/SiO₂-P adsorbent was prepared by impregnation of N,N′-dimethyl-N,N′-di-n-octyl-thiodiglycolamide (MOTDGA) and Tri-n-octylamine (TOA) into silica/polymer composite support (SiO₂-P). The adsorption behavior of Ru(III), Rh(III), and Pd(II) in simulated HLLW onto the adsorbent were investigated by the batch method to obtain their corresponding equilibrium and kinetic data. The adsorbent showed strong adsorption for Pd(II) and the adsorption reached equilibrium within 2 hr. High distribution coefficient (K _d) values for Pd(II) were obtained in 0.1–1 M HNO₃ concentration. In addition, the use of both MOTDGA and TOA improved adsorption of Ru(III) and Rh(III) better than individual use of them. Especially, the K _d value for Ru(III) towards (MOTDGA-TOA)/SiO₂-P adsorbent was three times larger than that in the adsorption using only with MOTDGA or TOA as extractant. The adsorptions of Ru(III), Rh(III), and Pd(II) followed the Langmuir adsorption model, and were found to be controlled by the chemisorption mechanism.     

Preparation of a Macroporous Silica-Based Multidentate Soft-Ligand Material and its Application in the Adsorption of Palladium and the Others

To separate Pd(II), a macroporous silica-based soft-ligand 2,6-bis(5,6-di(iso-butyl)-1,2,4-triazine-3-yl)pyridine (BDIBTP) material, BDIBTP/SiO₂-P, was synthesized by vacuum treatment. It was a multidentate chelating composite prepared by impregnation and immobilization of BDIBTP and 1-octanol molecules into the pores of the macroporous SiO₂-P particles with a mean diameter of 50 µm. 1-Octanol was used to modify BDIBTP through intermolecular interaction force. The adsorption of some typical fission products Zr(IV), Pd(II), La(III), Y(III), Ru(III), Rh(III), and Mo(VI) contained in highly active liquid waste (HLW) onto the BDIBTP/ SiO₂-P materials was investigated. It was carried out by examining the effects of contact time and the concentration of HNO₃ in the range of 0.3 M?7.0 M. BDIBTP/SiO₂-P showed excellent adsorption ability and high selectivity for Pd(II) over all of the tested metals. It was ascribed to the effective complexation of Pd(II) with BDIBTP/SiO₂-P. Consideration of the complexation of BDIBTP for minor actinides MAs(III), the possibility and feasibility of effective partitioning of Pd(II) and MAs(III) simultaneously from a simulated HLW were discussed. A new concept process entitled MPS for the MA(III) and Pd(II) Separation has been proposed.     

Adsorption Behavior of Platinum Group Metals onto a Silica-based (Crea+Dodec)/SiO2-P Extraction Resin from Simulated High Level Liquid Waste

Basic properties of a silica-based macroporous N’,N’-di-n-hexyl-thiodiglycolamide (Crea) extraction resin, (Crea+Dodec)/SiO₂-P were examined. This extraction resin was synthesized by impregnating Crea and its modifier, n-Dodecyl alcohol (Dodec) into the macroporous SiO₂-P support with a mean diameter of 50 μm. Adsorption behavior of platinum group metals (PGMs) and some fission product elements from simulated high level liquid waste onto the resin was investigated by batch experiment. It was found that (Crea+Dodec)/SiO₂-P extraction resin exhibited good adsorption selectivity for PGMs over other tested elements in 0.1-5.0 M HNO₃ solution. This resin showed strong affinity to Pd(II) especially in a short contact time but almost no adsorption for rare earth elements. Adsorption behavior of PGMs in experiment could be expressed by the Langmuir monomolecular layer adsorption mode. Meanwhile, adsorption results were fitted well with the pseudo-second order model and the rate-controlling step of this adsorption process was governed by the chemisorption process. In addition, the adsorption isotherms and thermodynamic parameters of tested elements were calculated by the Langmuir, Freundlich, and van’t Hoff equations, respectively.     

Synthesis of a macroporous silica‐based derivative of pyridine material and its application in separation of palladium

A novel macroporous silica‐based 2,6‐bis(5,6‐dibutyl‐1,2,4‐triazine‐3‐yl)pyridine (BDBTP) material, BDBTP/SiO₂‐P, was prepared through impregnation and immobilization of BDBTP and octanol into the pores of the SiO₂‐P particles. The adsorption of 10 typical fission and nonfission elements contained in highly active liquid waste (HLW) onto BDBTP/SiO₂‐P was investigated by examining the effect of contact time and the HNO₃ concentration in the range of 0.1–5.0 M. Pd(II), a weak Lewis acid and an electron‐pair acceptor, was strongly complexed with nitrogen, a weak Lewis base and an electron‐pair donor. BDBTP/SiO₂‐P showed excellent adsorption ability and high selectivity for Pd(II) over all the tested metals. The separation of Pd(II) from a simulated HLW was performed by BDBTP/SiO₂‐P packed column. Pd(II) was effectively eluted with 0.2 M thiourea and separated from the others. It demonstrated that in HNO₃, application of the macroporous silica‐based BDBTP/SiO₂‐P material in partitioning and recovery of Pd(II) from HLW is promising. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Use of Calix[4]-bis-2,3-naphthocrown-6 for Separation of Cesium from Pressurized Heavy Water Reactor Simulated High Level Waste Solutions (PHWR-SHLW)

Abstract

Distribution studies on Cs(I) were carried out from pressurized heavy water reactor (PHWR) simulated high level waste (SHLW) solution using calix[4]-bis-2,3-naphtho-crown-6 as the ligand. A mixture of 1:1 nitrobenzene and toluene was evaluated as a suitable diluent. The distribution ratio of Cs(I) increased with the aqueous feed acidity upto 3 M HNO₃ and decreased thereafter due to extraction of hydronium ions. The maximum D_Cs value at ～3 M HNO₃ suggested the possible application of the system for the recovery of radio-cesium from high level waste solution. The addition of 0.4% (v/v) Alamine 336 (a tertiary amine) facilitated the quantitative stripping of Cs(I) with distilled water. Quantitative extraction of Cs(I) from SHLW containing 0.32 g/L of Cs was observed in five contacts at O/A = 1/2 with 2.5 × 10^?3 M calix[4]-bis-2,3-naphtho-crown-6. Similarly, quantitative stripping of Cs(I) from the loaded organic phase was achieved in two contacts with distilled water at a volume ratio (O/A) of 2. Selectivity studies carried out using several radiotracers such as ¹⁴³Ce, ¹⁴⁰La, ¹⁴⁰Ba, ¹³⁷Cs, ¹⁰³Ru, ⁹⁹Mo, ^99mTc, ⁹⁷Zr, ⁹¹Sr, etc. indicated excellent selectivity for Cs. The reagent exhibited excellent chemical stability up to a period of six months.     

SPEC: A New Process for Strontium and Cesium Partitioning Utilizing Two Macroporous Silica-Based Supramolecular Recognition Agents Impregnated Polymeric Composites

Abstract

To effectively separate two heat generators Cs(I) and Sr(II) from a highly active liquid waste (HLW), two macroporous silica-based polymeric composites (Calix[4]arene-R14 + M)/SiO₂-P and (DtBuCH18C6 + M)/SiO₂-P were synthesized. It was done by impregnating and immobilizing the supramolecular recognition agent, 1,3-[(2,4-diethylheptyl ethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) or 4,4′,(5′)-di-(tert-butylcyclo hexano)-18-crown-6 (DtBuCH18C6), into the pores of the macroporous SiO₂-P particles with a mean diameter of 50 µm. It was found that in the first column packed with (Calix[4]arene-R14 + M)/SiO₂-P, all of the tested elements were effectively eluted and separated into two groups: (1 Horwitz , E.P. ; Mark , L.D. ; Fisher , D.E. ( 1991 ) SREX: A new process for the extraction and recovery of strontium from acidic nuclear waste stream . Solvent Extr. Ion Exch. , 9 ( 1 ): 1 – 25 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) Na(I), K(I), Sr(II), Ba(II), Rh(III), Ru(III), Pd(II), Zr(IV), RE(III) (La-Lu and Y), and Mo(VI) (Sr-containing group), and (2 Wood , D.J. ; Law , J.D. ( 1997 ) Evaluation of the SREX solvent extraction process for the removal of ⁹⁰Sr and hazardous metal ions from acidic nuclear waste solutions containing high concentrations of interfering alkali metal ions . Sep. Sci. Technol. , 32 ( 1–4 ): 241 – 253 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) Cs(I)-Rb(I) (Cs-group) by eluting with 4.0 M HNO₃ and water, respectively, at 298 K. The heat emitting element Cs(I) flowed into the second group along with Rb(I), while Sr(II) showed no sorption and flowed into the Sr-containing group. In the second column packed with (DtBuCH18C6 + M)/SiO₂-P, the Sr-containing group was separated into (1 Horwitz , E.P. ; Mark , L.D. ; Fisher , D.E. ( 1991 ) SREX: A new process for the extraction and recovery of strontium from acidic nuclear waste stream . Solvent Extr. Ion Exch. , 9 ( 1 ): 1 – 25 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) Na(I), K(I), Rh(III), Ru(III), RE(III) (La-Lu and Y), Pd(II), Zr(IV), and Mo(VI) (non-sorption group), and (2 Wood , D.J. ; Law , J.D. ( 1997 ) Evaluation of the SREX solvent extraction process for the removal of ⁹⁰Sr and hazardous metal ions from acidic nuclear waste solutions containing high concentrations of interfering alkali metal ions . Sep. Sci. Technol. , 32 ( 1–4 ): 241 – 253 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) Sr(II)-Ba(II) (Sr-group), by eluting with 2.0 M HNO₃ and water, respectively. The heat emitting element Sr(II) adsorbed by (DtBuCH18C6 + M)/SiO₂-P flowed into the second group along with Ba(II). Based on the results, a new process entitled SPEC (Strontium/Cesium Partitioning from HLW by Extraction Chromatography) for heat generator partitioning from a simulated highly active liquid waste utilizing two macroporous silica-based supramolecular recognition composites has been developed.     

Extraction Properties of P(O)-Modified N-Aryl-Carbamoylmethylphosphine Oxides in Nitric Acid Media

Novel polyfunctional neutral organophosphorus compounds, P(O)-modified N-aryl- carbamoylmethylphosphine oxides, Ph₂P(O)CH₂C(O)NH-(o-C₆H₄)(CH₂)_n-P(O)Ph₂ and Ph₂P(O)CH₂C(O)NH-(m-C₆H₄)(CH₂)_n-P(O)Ph₂ (n = 1,2), were synthesized and studied as extractants for U(VI), Th(IV) and Ln(III) from HNO₃ solutions. The influence of aqueous and organic phases on the extraction efficiency was elucidated and stoichiometry of the complexes extracted was determined. Introduction of an additional phosphoryl group into the phenyl substitutent at the nitrogen atom of diphenyl(N-phenylcarbamoylmethyl)phosphine oxide resulted in an increase of the efficiency of U(VI), Th(IV), Ln(III), and Re(VII) extraction.     

Selected Alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine Oxides as Extractants for Am(III) from Nitric Acid Media

Abstract

A new series of neutral bifunctional extractants, alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine oxides, has been prepared and studied as extractants for Am(III) from nitric acid media. Two types of alkyl(phenyl)-N,N-dialkyl CMPO compounds were prepared, one containing N,N-diethyl groups and the other containing N,N-diisobutyl groups. The N,N-diethyl series contained hexyl(phenyl) and 6-methylheptyl(phenyl) derivatives, abbreviated HφDECMPO, and 6-MHφDECMPO, respectively. The N,N-diisobutyl series contained the n-octyl(phenyl), 6-methylheptyl(phenyl), and the 2-ethylhexyl(phenyl) derivatives, abbreviated OφD[IB]CMPO, 6-MHφD[IB]CMPO, and 2-EHφD[IB]CMPO, respectively. Third power extractant dependencies for the extraction of Am(III) from 0.5 and 3 M HNO₃ were obtained at low (<0.25 M) concentrations of extractant, but higher power dependencies were obtained above 0.25 M extractant from 3 M HNO₃. The HφDECMPO, 6-MHφDECMPO, 6-MHφD[IB]CMPO, and OφD[IB]CMPO [all 0.5 M in diethylbenzene (DEB)] are significantly better extractants than DHDECMPO for Am(III) from 1 to 6 M HNO₃. These same extractants have lower D _Am values than DHDECMPO at low acidities. HφDECMPO and OφD[IB]CMPO also have better selectivity for Am(III) over Fe(III) than DHDECMPO. HφDECMPO in DEB has a strong tendency toward the formation of a second liquid organic phase on extracting macroconcentrations of Nd(III) and U(VI) from 3 M HNO₃; however, this behavior is substantially diminished with the OφD[IB]CMPO and 6-MHφD[IB]CMPO compounds.     

Conformationally Mobile Wide Rim Carbamoylmethylphosphine Oxide (CMPO)-Calixarenes

Six new calix[4]arene derivatives 2a – f have been synthesised, bearing CMPO-like functions (-NH–C(O)–CH₂–P(O)Ph₂) at their wide rim. They differ by their alkoxy groups at the narrow rim, comprising all possible combinations of methoxy and syn-propoxy groups including the conformationally mobile tetramethyl ether 2e and the tetrapropyl ether 2f fixed in the cone conformation. Their extraction behaviour for thorium(IV) and several lanthanides(III) from 1M HNO₃ to dichloromethane has been studied and compared also to non cyclic calixarene analogues 6a – e . Surprisingly the best extraction results were found for the 1,2-dimethoxy-3,4-dipropoxy derivative 2c among the calixarenes and for the tetramer 6d among the linear compounds. Extraction of americium(III) in comparison to curium(III) and various lanthanides(LaIII), Ce(III), Nd(III), Sm(III), Eu(III)) from 0.1– 3M HNO₃ to NPHE (o-nitrophenyl hexyl ether) was most effective again for 2c . Among these cations, the highest distribution coefficients were found for Am(III) and the lowest for Ce(III) with a maximum generally in the range of 1–2M HNO₃.