Silica-based Extraction Resin Research Articles

Fabrication of a novel porous silica-based extraction resin and application in the adsorption of trivalent actinides

Separating long-lived minor actinides is an important subject in the field of radioactive waste disposal and radioactive analysis. The simple, convenient, effective separation of adjacent trivalent actinides with very similar chemical properties, Am(Ⅲ) and Cm(Ⅲ), represents a very difficult challenge. Here we report a novel porous silica-based extraction resin embedded with bis(chlorophenyl)dithiophosphinic acid (BCPDTPA) as extractants, BCPDTPA/SiO2- polymer. The multiporous silica particles with a high adsorption capacity were particularly prepared. The physicochemical properties of the BCPDTPA/SiO2-P resin materials (i.e., morphology, porous characteristics, and chemical structure) were comparatively investigated with pure SiO2 particles. The stability experiments in acidic and irradiation environment were also performed, respectively. The adsorption characteristics of BCPDTPA/SiO2-P resins for Am(Ⅲ) and Cm(Ⅲ) were mainly discussed. The results demonstrated that the BCPDTPA/SiO2-P resins fabricated in this work showed a high adsorption capacity, structural stability, and excellent adsorption characteristics for Am(Ⅲ) and Cm(Ⅲ). It may thus have great potential to develop the as-assembled silica-based materials as a novel, highly effective extraction resins for the separation of actinides(Ⅲ)/lanthanides(Ⅲ), especially for those elements with very similar chemical properties, such as Am(Ⅲ) and Cm(Ⅲ).

Separation of trivalent actinides from lanthanides by using R-BTP resins and stability of R-BTP resin

For the development of advanced aqueous reprocessing system, it is one of the most important subjects to separate minor trivalent actinides (MA = Am and Cm). MA are α-emitters with long half-life, therefore it is desired to separate MA from fission products. However, it is very difficult to separate MA from lanthanides (Ln) owing to their chemical similarity. For the separation of these two groups of elements, solvent extraction process has been widely studied based on the difference in complex formation with extractants. Extraction chromatography is one of the most promising separation techniques for recovering small amounts of target components from solution. For this purpose, we prepared novel silica-based extraction resins by impregnating some R-BTP molecules into a macroreticular styrene–divinylbenzene copolymer which is immobilized in porous silica particles with a mean diameter of 50 μm. The impregnated resin has high affinity for Am against Ln(III) not only in sodium nitrate solution but also in nitric acid solution. Stability of the extraction resin was also examined. The silica-based support was significantly stable against γ-irradiation and nitric acid. A part of R-BTP was dissolved into nitric acid solution from the extraction resin due to protonation. However, the branched R-BTP ( iso-Bu-BTP) resin was much more stable than a normal R-BTP in nitric acid solution (≤3 M).

A new partitioning process for high-level liquid waste by extraction chromatography using silica-substrate chelating agent impregnated adsorbents

To separate the long-lived minor actinides (MA(III) = Am(III), Cm(III)) and some specific fission products (FP) such as Pd(II), Mo(VI), Cs(I) and Sr(II) from high-level liquid waste (HLLW), we have been studying a new partitioning process by extraction chromatography using several novel silica-based extraction resins. In this work, we examined the separation behavior of the elements contained in a simulated MA-effluent by the CMPO/SiO 2 P packed column. In addition, as an attempt to further isolate Am(III) and Cm(III) from the heavy RE(III) such as Eu(III), Gd(III) and Dy(III) contained in the MA-effluent, we investigated the possibility of separation by using a silica-based cationic exchange resin. Furthermore, to isolate Sr(II) from the HLLW, adsorption and separation performances of Sr(II) and some other FP elements were studied by using a novel silica-based crown ether extraction resin, DtBuCH18C6/SiO 2 P. The experimental results demonstrated that the elements in the simulated MA-effluent can be successfully separated to (1) Pd, (2) MA-hRE and (3) Zr–Mo, by CMPO/SiO 2 P packed column using water and a dilute DTPA solution as eluents. Am(III) and Cm(III) are expected to be effectively separated from light RE(III) and Y(III) by the SiSCR cationic resin. However, more effective separation between Am(II), Cm(III) and heavy RE(III) such as Eu(III), Gd(III) and Dy(III) needs further approach. DtBuCH18C6/SiO 2 P showed a highly selective adsorption for Sr(III) so that the Sr(II) could be completely separated from other FPs except a portion of Ba(II).

Separation of Am(III) and Cm(III) from trivalent lanthanides by 2,6-bistriazinylpyridine extraction chromatography for radioactive waste management

To separate long-lived minor actinides (MA=Am, Cm) from high level liquid waste (HLLW), we have prepared a novel silica-based extraction resin by impregnating 2,6-bis-(5,6-dibutyl-1,2,4-triazine-3-yl)pyridine ( nBu-BTP) into the porous SiO 2-P support with a diameter of 50 μm. The adsorption performance of Am(III), Cm(III) and typical fission products (FP) including lanthanides (Ln) from nitrate acidic solution was investigated. Furthermore, separation behavior of MA from Ln was examined by extraction chromatography using a column packed with the extraction resin. It was found that the extraction resin exhibits significantly high adsorbability and selectivity for Am(III) and Cm(III) over other FP elements. A complete separation between Am(IV) and Ln(III) was achieved in the column experiment.

Group separation of trivalent minor actinides and lanthanides by TODGA extraction chromatography for radioactive waste management

For the development of an advanced reprocessing process, it is one of the most important tasks to separate long-lived minor actinides (MA). The authors have been developing an advanced reprocessing process, ERIX process, including a selective separation of MA(III) [Proceedings of the JAERI-Conference 2002–2004 (2002) 225]. In this work, group separation of trivalent MA and lanthanides (Ln) from simulated high level liquid waste (HLLW) using a novel silica-based extraction resin containing the newly developed chelating extractant was investigated. N, N, N′, N′-Tetraoctyl-3-oxapentane-1,5-diamide (TODGA) was developed recently and has high affinity for MA(III) and Ln(III) in concentrated nitric acid medium [Solv. Extr. Ion Exch. 20 (2002) 687]. The novel silica-based extraction resin was prepared by impregnating TODGA into a macroreticular styrene–divinylbenzene copolymer which is immobilized in porous silica particles with a mean diameter of 50 μm. This impregnated resin has the good properties such as fast kinetics and less swelling for use in extraction chromatography. The results of separation experiments for the simulated HLLW solutions using TODGA extraction resin demonstrated that both MA(III) and Ln(III) can be effectively isolated from almost all of the other FP elements.

Preparation of Novel Silica-Based R-BTP Extraction-Resins and Their Application to Trivalent Actinides and Lanthanides Separation

To separate long-lived minor actinides and specific fission products such as Zr and Mo from nitrate acidic high-level liquid waste, we have been studying an advanced partitioning process by extraction chromatography using a minimal organic solvent and compact equipment. In this work, we have synthesized several new type of nitrogen donor ligands, 2,6-bis-(5,6-dialkyl-1,2,4 -triazine-3-yl)-pyridine with different alkyl groups and prepared the novel silica-based extraction-resins by impregnating these ligands into the SiO2-P support with a diameter of 50 μm. The adsorption performance of 243Am(III) and typical fission product Ln(III) from nitrate solution on these extraction-resins was investigated. It was found that the adsorption behavior depends strongly on the alkyl group in R-BTP. «Bu-BTP/SiO2-P and wHex-BTP/SiO2-P showed significantly higher adsorbability and selectivity for Am(lH) over Ln(m). The separation factor is about 104 for Am/Ce and near 102 for Am/Eu-Gd, respectively. It is expected that Am(III) can be effectively separated from Ln(HT) by extraction chromatography using these novel R-BTP/SiO2-P extraction-resins.

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

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

Studies on the Separation of Minor Actinides from High-Level Wastes by Extraction Chromatography Using Novel Silica-Based Extraction Resins

To develop an advanced partitioning process by extraction chromatography using a minimal organic solvent and compact equipment to separate minor actinides such as Am and Cm from nitrate acidic high-level waste (HLW) solution, several novel silica-based extraction resins have been prepared by impregnating organic extractants into the styrene-divinylbenzene copolymer, which is immobilized in porous silica particles (SiO2-P). The extractants include octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO), di(2-ethylhexyl)-phosphoric acid (HDEHP), and bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301). Compared to conventional polymer-matrix resins, these new types of extraction resin are characterized by rapid kinetics and significantly low pressure loss in a packed column.The results of separation experiments revealed that trivalent actinides and lanthanides can be separated from other fission products, such as Cs, Sr, and Ru in simulated HLW solution containing concentrated nitric acid by extraction chromatography using a CMPO/SiO2-P resin-packed column. Satisfactory separation between Am(III) and a macro amount of lanthanides from simulated HLW solution with pH 4 was achieved by using a newly purified Cyanex 301/SiO2-P resin. However, the Am(III) separation was very sensitive to the purity of Cyanex 301, and the improvement of its stability is an important task for practical utilization.