Harutaka Hoshi

Chromatographic Separation of Strontium (II) from a Nitric Acid Solution Containing some Typically Simulated Elements by a Novel Silica‐Based TODGA Impregnated Polymeric Composite in the MAREC Process

Abstract A new kind of macroporous silica‐based N,N,N′,N′‐tetraoctyl‐3‐oxapentane‐1,5‐diamide (TODGA) chelating polymeric adsorption material (TODGA/SiO2‐P) was developed and synthesized by impregnating TODGA molecules into the pores of ∼50 µm SiO2‐P particles to separate strontium effectively from high‐level liquid waste (HLLW). The adsorption of some typically simulated elements Na(I), K(I), Cs(I), Rb(I), Sr(II), Ba(II), and Ru(III) towards TODGA/SiO2‐P adsorbent was investigated by examining the influence of contact time and HNO3 concentration. It was found that with an increase in the HNO3 concentration, the adsorption of Sr(II) onto TODGA/SiO2‐P adsorbent increased quickly from 0.5 M to 2.0 HNO3 and then decreased. TODGA/SiO2‐P exhibited excellent adsorption ability and selectivity for Sr(II) over all of the tested elements, which showed almost no adsorption. Based on the batch experiments, the separation of Sr(II) from a 2.0 M HNO3 solution containing ∼5×10−3 M of the simulated elements was performed by TODGA/SiO2‐P packed column at 25°C and 50°C, respectively. Cs(I), K(I), Ru(III), Ba(III), Rb(I), and Na(I) were found to facilely elute out column and flow into effluent along with feed solution and 2.0 M HNO3 because of no adsorption. Sr(II) adsorbed towards TODGA/SiO2‐P was desorbed sufficiently by distilled water and separated completely from the simulated elements. Its recovery percentage was 100.2% at 25°C and 99.7% at 50°C. Furthermore, the leakage behavior of TODGA from its silica‐based adsorbent was investigated. It was found that the quantity of TODGA leaked was basically equivalent to its solubility in the corresponding HNO3 solution.

Partitioning of Cesium from a Simulated High Level Liquid Waste by Extraction Chromatography Utilizing a Macroporous Silica‐Based Supramolecular Calix[4]arene‐Crown Impregnated Polymeric Composite

Abstract 1,3‐[(2,4‐Diethyl‐heptylethoxy)oxy]‐2,4‐crown‐6‐calix[4]arene (Calix[4]arene‐R14) is a supramolecular compound exhibiting Cs ion recognition in high level liquid waste (HLLW). To separate effectively Cs(I) from HLLW, a novel silica‐based Calix[4]arene‐R14 polymeric material (Calix[4]arene‐R14/SiO2‐P) was prepared. It was done through impregnating a mixture of Calix[4]arene‐R14 and tri‐n‐butyl phosphate (TBP), a molecular modifier, into the pores of macroporous SiO2‐P particles utilizing a vacuum sucking technique. The sorption of some typical fission product (FP) elements Na(I), K(I), Cs(I), Rb(I), Sr(II), and La(III) towards Calix[4]arene‐R14/SiO2‐P was investigated by examining the influence of contact time and the HNO3 concentration. It was found that with an increase in the HNO3 concentration from 1.0 M to 4.0, the sorption of Cs(I) towards Calix[4]arene‐R14/SiO2‐P increased quickly and then decreased with further increase of HNO3 concentration to 5.0 M. At the optimum HNO3 concentration of 4.0 M HNO3, the Calix[4]arene‐R14/SiO2‐P adsorbent exhibited excellent sorption ability and selectivity for Cs(I) over all of the tested elements, which showed very weak or almost no sorption except Rb(I). The chromatographic separation of Cs(I) from a simulated HLLW containing ∼5 mM of the FP elements and 4.0 M HNO3 was performed by Calix[4]arene‐R14/SiO2‐P packed column at 298 K. Na(I), K(I), Sr(II), and La(III) were found to elute facilely and flowed into the effluent along with 4.0 M HNO3. Cs(I) and Rb(I), adsorbed strongly onto Calix[4]arene‐R14/SiO2‐P, were desorbed sufficiently by water. The leakage behavior of Calix[4]arene‐R14 and TBP from Calix[4]arene‐R14/SiO2‐P was also investigated.

UPTAKE PROPERTIES OF PALLADIUM FOR BIOPOLYMER MICROCAPSULES ENCLOSING CYANEX 302 EXTRACTANT

An extractant having a strong affinity for palladium, bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302), was enclosed into microcapsules by mixing with a biopolymer, calcium alginate gel polymer. The uptake of Pd2+ and other metal ions in the microcapsules was investigated; a relatively large distribution coefficient of Pd2+, K d,Pd, of above 103 cm3/g was obtained around 0.1 M HNO3, and there was a large difference in K d value between Pd2+ and other metal ions. The uptake of Pd2+ on microcapsules followed a Langmuir-type uptake isotherm. The microcapsules were packed into a column and then a separation of Pd2+ was performed.

Synthesis of a Novel Silica‐Based Macroporous Polymer Containing TODGA Chelating Agent and Its Application in the Chromatographic Separation of Mo(VI) and Zr(IV) from Diethylenetriaminepentaacetic Acid

Abstract A novel silica‐based N,N,N′,N′‐tetraoctyl‐3‐oxapentane‐1,5‐diamide (TODGA) chelating polymeric material (TODGA/SiO2‐P) was synthesized by impregnating TODGA into ∼50 µm of spherical SiO2‐P particles for separating Mo(VI) and Zr(IV) from a HNO3 solution containing 0.05 M diethylenetriaminepentacetic acid (DTPA) in minor actinides recovery by extraction chromatography (MAREC) process. The adsorption of TODGA/SiO2‐P for Mo(VI) and Zr(IV) was investigated by examining the influence of HNO3 and DTPA concentrations. It was found that HNO3 concentration from 0.3 M to 9 M either with or without 0.05 M DTPA had a strong effect on the adsorption of Mo(VI) and Zr(IV) towards TODGA/SiO2‐P. In the absence of 0.05 M DTPA, both the adsorption of Mo(VI) and Zr(IV) decreased with an increase in the concentration of HNO3 from 0.3 M to 3 M and then gradually increased. In the presence of 0.05 M DTPA, Zr(IV) showed scarcely any adsorption towards TODGA/SiO2‐P below 2 M HNO3 and was gradually adsorbed from 2 M to 3 M HNO3 while Mo(VI) showed almost no adsorption. In excess of 3 M HNO3, the adsorption curve of Mo(VI) or Zr(IV) fully overlapped with that of the absence of 0.05 M DTPA. This resulted from the dissociation of Mo(VI) or Zr(IV) from its complex with DTPA because of full protonation of DTPA in high HNO3 concentration and the strong complexation taking place simultaneously with TODGA/SiO2‐P. In terms of the batch experiments, the separation of Mo(VI) and Zr(IV) from a 3 M HNO3 solution containing 0.05 M DTPA was performed by employing the TODGA/SiO2‐P packed column at 50°C. Molybdenum(VI) was found to leak out of the column along with 3 M HNO3. Zirconium(IV) adsorbed by TODGA/SiO2‐P was effectively eluted by 0.5 M H2C2O4. The recovery was 101.6% for Mo(VI) and 94.8% for Zr(IV). This work was financially supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) under the framework of the “Development of Innovation Nuclear Technologies.”

Elemental Groups Separation for High-Level Waste Partitioning Using a Novel Silica-Based CMPO Extraction-Resin

Abstract To facilitate the management of high-level liquid waste (HLLW) and minimize its long-term radiological risk in geologic disposal. We have proposed an advanced partitioning process by extraction chromatography using a minimal organic solvent and compact equipment to separate long-lived minor actinides (MA) and specific fission products (FP) such as Zr and Mo from nitrate acidic HLLW solution. The process consists of two separation columns packed with CMPO (octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide) extraction-resin for elemental groups separation and R-BTP (2,6-bis-(5,6-dialkyl-l,2,4-triazine-3-yl)-pyridine) extraction-resin for the isolation of MA from lanthanides (Ln), respectively. Several novel silica-based extraction resins have been prepared by impregnating CMPO or R-BTP into a macroreticular styrene -divinylbenzene copolymer which is immobilized in porous silica particles with a diameter of 50 μm (SiO2-P). In this work, adsorption and elution behavior of typical FP elements from nitric acid solution onto the CMOP extraction-resin was investigated. Separation experiments for simulated HLLW solutions containing a trace amount of 243Am (III) and macro amounts of typical FP elements were carried out by column chromatography. It was found that the elements in the simulated HLLW were successfully separated to the following there groups: Cs-Sr-Rh-Ru, Pd-Ln-Am and Zr-Mo

Separation of americium from europium by biopolymer microcapsules enclosing Cyanex 301 extractant

Microcapsules enclosing an extractant with strong affinity for Am were prepared by employing a biopolymer gel as an immobilization matrix. A relatively large separation factor between Am and Eu was exhibited by the microcapsule containing of bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301, HA) and alginic acid (HALG). The chromatographic separation of these metal ions was accomplished by gradient elution through the column packed with HA-HALG.

Adsorption and Chromatographic Separation of Mo(VI) and Zr(IV) Ions from a High-Concentration Oxalic Acid Solution by a Macroporous Silica-Based N,N,N′,N′-Tetraoctyl-3-Oxapentane-1,5-Diamide Polymeric Adsorbent

To separate Mo(VI) and Zr(IV) ions from a 0.5 M oxalic acid solution and from each other, a novel macroporous silica-based N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) chelating polymeric adsorbent (TODGA/SiO2-P) was synthesized by introducing the TODGA molecule into ca. 50-μm diameter SiO2-P particles by impregnation. The adsorption of Mo(VI) and Zr(IV) ions onto TODGA/SiO2-P was investigated by examining the influence of nitric acid and oxalic acid concentrations. It was found that the adsorption was strongly affected by increasing the HNO3 concentration from 0.5 M to 9.0 M either with or without the addition of 0.5 M H2C2O4. In the absence of 0.5 M H2C2O4, the distribution coefficients (Kd) of both Mo(VI) and Zr(IV) ions decreased with an increase in the HNO3 concentration from 0.5 M to 3.0 M, increased slowly when the concentration of HNO3 was increased further from 3.0 M to 6.0 M, and then increased gradually above 6.0 M concentration. Furthermore, the adsorption of Zn(IV) ions onto TODGA/SiO2-P was considerably greater than that of Mo(VI) ions. In the presence of 0.5 M H2C2O4, Zr(IV) ions showed no adsorption at HNO3 concentrations below 4.0 M, being partly adsorbed in the presence of 4.0–6.0 M HNO3 and fully adsorbed when the HNO3 concentration was greater than 6.0 M. In contrast, Mo(VI) ions showed a much lower adsorption at HNO3 concentrations below 2.0 M and no adsorption above this acid level. In the presence of HNO3 at a concentration above 6.0 M and containing 0.5 M H2C2O4, the adsorption of Zr(IV) ions overlapped that from a similar HNO3 solution which did not include 0.5 M H2C2O4. This was attributed to complete protonation of the C2O2−2 anion. On the basis of batch experiments, Mo(VI) and Zr(IV) ions were separated from a 6.5 M HNO3 solution containing 0.5 M H2C2O4 by means of a column packed with TODGA/SiO2-P at 50°C. The separate components, Mo(VI) and Zr(IV), could be effectively separated from each other by eluting with some selected eluants. The recovery percentage was 100.5% for Mo(VI) ions and 96.8% for Zr(IV) ions.

Separation of Americium from Europium Using Liquid Membrane Impregnated with Organodithiophosphinic Acid

The selective transport of Am across a supported liquid membrane (SLM) has been investigated by using bis (2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) as a mobile carrier. This extractant containing soft donor atoms exhibits strong affinity for actinoids, giving a large separation factor between trivalent Am and Eu. Separation of Am from Eu was achieved by an SLM containing highly purified Cyanex 301. Americium was preferentially transported across the SLM and concentrated in the product solution, while most of Eu remained in the feed solution.

SEPARATION OF LANTHANOIDS AND ACTINOIDS BY CENTRIFUGAL PARTITION CHROMATOGRAPHY

The separation of actinoids such as Am from lighter lanthanoids has been investigated based on the liquid-liquid extraction principle. An extractant, 5, 8-diethyl-7-hydroxy-dodecan-6-one oxime (LIX 63), is suitable for separation of actinoids heavier than Am from lanthanoids lighter than Eu. On the basis of extraction behavior, multistage separation has been performed by centrifugal partition chromatography (CPC) provided with a series of micro cells. A kerosene solution of LIX 63 was retained in a column as a stationary phase without any solid support. The element substituted for heavier actinoids was chromatographically separated from lighter lanthanoids by CPC.

Leakage of Octyl(Phenyl)-N,N-Di-Isobutylcarbamoylmethylphosphine Oxide from a Macroporous Silica-Based Chelating Polymeric Adsorption Material and its Recovery by Some Selected Porous Adsorbents

The leakage behaviour of a neutral chelating agent, i.e. octyl(phenyl)-N,N-di-isobutylcarbamoylmethylphosphine oxide (CMPO), from its macroporous silica-based (CMPO/SiO2-P) extraction resin (a novel polymeric adsorption material developed in the MAREC process) and the recovery of CMPO by some selected polymer- and silica-based porous adsorbents were investigated by column operation in 0.01 M HNO3 at 25°C or 50°C. The concentration of CMPO in the effluent leaking from CMPO/SiO2-P was determined as ca. 48 ppm at 25°C and ca. 37 ppm at 50°C. The corresponding elution volumes and the amounts of CMPO leaking were 8700.9 BV/g and 239.3 mg/g at 25°C and 11 842.9 BV/g and 359.4 mg/g at 50°C, respectively. The adsorption experiment showed that a polymer-based porous material, SEPABEADS® SP-825, was capable of recovering CMPO effectively from 0.01 M HNO3. Its adsorption ability towards CMPO was considerably greater than those of macroporous silica-based SiO2-P particles, polymer-based Amberlite™ XAD-7 and activated carbon. The bed volume and the amount of CMPO adsorbed by SEPABEADS® SP-825 at the breakthrough point at 25°C were 13 549.2 BV/g and 498.7 mg/g, respectively, thereby demonstrating that SEPABEADS® SP-825 was promising for the recovery of CMPO from Am(III)- and Cm(III)-containing solutions in the MAREC process.