A novel partitioning process for treatment of high level liquid waste using macroporous silica-based adsorbents

To separate the long-life and significant fission product elements from high level liquid waste (HLLW), a novel partitioning process for the treatment of HLLW has been studied experimentally based on column separation technique using macroporous silica-based adsorbents. This process consists of (1) Cs and Rb are removed by the first separation column packed with (calix[4] + dodecanol)/SiO₂–P adsorbent; (2) Sr and Ba are eluted out by the second separation column packed with (DtBuCH18C6 + dodecanol)/SiO₂–P adsorbent; (3) Pd is partitioned by the third separation column packed with MOTDGA–TOA/SiO₂–P adsorbent; (4) Ru, Rh and Mo can be separated by the fourth separation column packed with TODGA/SiO₂–P adsorbent; (5) Am is separated from RE by the fifth column is packed with isobutyl-BTP/SiO₂–P adsorbent. The experimental results indicated that this partitioning process is essentially feasible.     

Stability of <Emphasis Type="Italic">iso</Emphasis>Hex-BTP/SiO<Subscript>2</Subscript>-P adsorbent against acidic hydrolysis and γ-irradiation

Separation of trivalent minor actinides (MA(III): Am(III), Cm(III)) from fission products (FP) in high-level liquid waste (HLLW) is an important task in advanced nuclear-fuel reprocessing systems. For this purpose, an advanced aqueous partitioning process based on extraction chromatography method was studied. Because R-BTP extractants (R-BTP: 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine, R = alkyl group) exhibit high selectivity for MA(III) over trivalent rare-earth elements (RE(III)), a novel adsorbent isoHex-BTP/SiO₂-P was prepared by impregnating isoHex-BTP extractant into the macroporous SiO₂-P support with a mean diameter of 60 μm. The stability of isoHex-BTP/SiO₂-P against nitric acid and γ-irradiation was investigated. It was found that isoHex-BTP/SiO₂-P adsorbent shows good adsorption affinity to Dy(III). The hydrolytic and radiolytic stability of isoHex-BTP/SiO₂-P adsorbent in 0.01 mol/L HNO₃ was fairly promising. However, the adsorption amount Q of Dy(III) decreased dramatically in 3 mol/L HNO₃ with the increase of the absorbed dose and became nearly zero at the absorbed dose over 46 kGy. These results suggest that with the synergetic effect of radiation and acidic hydrolysis, the adsorbent instantly loses its efficacy.     

Evaluation study on properties of isohexyl-BTP/SiO2-P resin for direct separation of trivalent minor actinides from HLLW

In order to develop a direct separation process for trivalent minor actinides from fission products in high level liquid waste (HLLW) by extraction chromatography, a novel macroporous silica-based 2,6-bis(5,6-diisohexyl)-1,2,4-triazin-3-yl)pyridine resin (isohexyl-BTP/SiO₂-P resin) was prepared. The content of isohexyl-BTP extractant in the resin was as high as 33.3 wt%. The resin exhibited much higher adsorption affinity for Am(III) in 2–3 M (mol/L) HNO₃ solution over U and FP which are contained in HLLW. The kinetic data were analyzed using pseudo-second-order equation. The results suggested that the Eu(III), Gd(III), and Dy(III) adsorption was well explained by the pseudo-second-order equation. Quantitative desorption for adsorbed elements was achieved by using H₂O or thiourea as eluting agents. However, the kinetics of adsorption and desorption were rather slow and this drawback needs to be resolved. Stability of the resin against HNO₃ was also examined. It was found that the resin was considerably stable against ≤4 M HNO₃ solution for the reasons of an extremely small leakage of the extractant into the solution from the resin and the adsorption performance keeping for rare earths in 3 M HNO₃ solution.     

Adsorption and desorption behavior of tetravalent zirconium onto a silica-based macroporous TODGA adsorbent in HNO3 solution

To understand the separation behavior of Zr(IV) in the partitioning process for high level liquid waste, a silica-based macroporous adsorbent (TODGA/SiO₂-P) was prepared by impregnating N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) into a macroporous silica/polymer composite particles support (SiO₂-P). Adsorption and desorption behavior of Zr(IV) from nitric acid solution onto silica-based TODGA/SiO₂-P adsorbent were investigated by batch experiment. It was found that TODGA/SiO₂-P showed strong adsorption affinity to Zr(IV) and this adsorption process reached equilibrium state around 6 h at 298 K. Meanwhile, HNO₃ concentration had no significant effect on the adsorption of Zr(IV) above 1 M. From calculated thermodynamic parameters, this adsorption process could occur spontaneously at the given temperature and was confirmed to be an exothermic reaction. This adsorption process could be expressed by Langmuir monomolecular layer adsorption mode and the maximum adsorption capacity were determined to be 0.283 and 0.512 mmol/g for Zr(IV) at 298 and 323 K, respectively. In addition, more than 90 % of Zr(IV) adsorbed onto adsorbent could be desorbed with 0.01 M diethylenetriamine pentaacetic acid solution within 24 h at 298 K.     

Adsorption behavior of Me2-CA-BTP/SiO2-P adsorbent toward MA(III) and Ln(III) in nitrate solution

A porous Me₂-CA-BTP/SiO₂-P adsorbent was prepared to separate MA(III) from Ln(III) in high level liquid waste (HLLW). The adsorption behavior of Me₂-CA-BTP/SiO₂-P toward ²⁴¹Am(III) and Ln(III) in 0.01 M HNO₃-NaNO₃ solution was studied. Me₂-CA-BTP/SiO₂-P showed high adsorption and selectivity toward ²⁴¹Am(III) over Ln(III) fission products with the separation factor (SF) reaching to 557, 2355, 1952, 1082, 214, 105, 86, 14 for Y, La, Ce, Nd, Sm, Eu, Gd and Dy respectively in 0.01 M HNO₃-0.99 M NaNO₃ solution. The adsorption kinetics of both Dy(III) and Eu(III) on Me₂-CA-BTP/SiO₂-P was studied and followed pseudo-second-order rate equation indicating chemical sorption as the rate-limiting step of the adsorption, and the adsorption isotherm of Dy(III) and Eu(III) matched better with the Langmuir isotherm than the Freundlich isotherm with the adsorption amount around 0.22 and 0.20 mmol/g respectively. Thermodynamic study revealed that the adsorption of both Dy(III) and Eu(III) on Me₂-CA-BTP/SiO₂-P was spontaneous and endothermic processes with a positive entropy at 298, 308, 313 K.     

Adsorption properties and behavior of the platinum group metals onto a silica-based (Crea + TOA)/SiO2–P adsorbent from simulated high level liquid waste of PUREX reprocessing

To separate platinum group metals (PGMs) from high level liquid waste (HLLW), a novel silica-based (Crea + TOA)/SiO₂–P adsorbent was synthesized by impregnating Crea (N′,N′-di-n-hexyl-thiodiglycolamide) and TOA (trioctylamine) two extractants into the macroporous SiO₂–P support with a mean diameter of 60 μm. Adsorption properties and behavior of PGMs from simulated HLLW onto the novel silica-based (Crea + TOA)/SiO₂–P adsorbent were investigated by batch method. It was found that (Crea + TOA)/SiO₂–P adsorbent exhibited good adsorption selectivity for PGMs over the other tested fission product element in a wide HNO₃ concentration. This adsorbent showed strong affinity to Pd(II) but almost no adsorption for rare earth elements. Adsorption process of PGMs could be expressed by Langmuir monomolecular layer adsorption mode and be governed by the chemisorption process. In addition, the adsorption isotherms and thermodynamic parameters of tested elements were calculated by Langmuir equation, Freundlich equation and van’t Hoff equation, respectively.     

Impregnation synthesis of a novel macroporous silica-based TODGA polymeric composite and its application in the adsorption of rare earths in nitric acid solution containing diethylenetriaminepentaacetic acid

A macroporous silica-based N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric composite (TODGA/SiO₂-P) was synthesized. It was done through impregnation and immobilization of TODGA molecule into the pores of the SiO₂-P particles utilizing a vacuum sucking technique. The macroporous SiO₂-P particles were the silica-based organic/inorganic composite synthesized by immobilizing styrene-divinylbenzene copolymer inside SiO₂ through the complicated polymerization reaction. The adsorption of rare earth (RE(III)) elements onto TODGA/SiO₂-P was investigated in HNO₃ solution containing diethylenetriaminepentaacetic acid (DTPA), an acidic multi-dentate chelating agent. It was found that in the presence of 0.05 M DTPA, and H⁺ had significant effect on the TODGA/SiO₂-P adsorption due to the competition reactions of RE(III) with different species, H₄DTPA⁻ and H₂DTPA³⁻. With an increase in the concentration of from 0.115 M to 3.015 M, the adsorption of RE(III) onto TODGA/SiO₂-P increased noticeably. On the other hand, RE(III) showed strong adsorption at 0.1 M H⁺, weak adsorption at around pH 2, and no adsorption in excess of pH 2.3. In a 0.1 M H⁺-0.115 M -0.05 M DTPA solution, a change of the distribution coefficient of RE(III) onto TODGA/SiO₂-P with an increase in atomic number of RE(III) from La(III) to Lu(III) was investigated. The silica-based TODGA/SiO₂-P polymeric composite showed strong adsorption for heavy RE(III) over the light one. In a 0.01 M H⁺-1.0 M -0.05 M DTPA solution, the effect of the ratio of solid phase to liquid one on the relationship of the distribution coefficient of RE(III) with the change in atomic number of RE(III) was also studied. Based on the complicated disassociation equilibrium of DTPA, the influence of the concentrations of and H⁺ on the adsorption of TODGA/SiO₂-P for RE(III) was demonstrated. This makes the partitioning of RE(III) and MA(III) together from high level liquid waste (HLLW) by the polymeric composite TODGA/SiO₂-P promising.     

Bleeding evaluation of the stationary phase from a few novel macroporous silica-substrate polymeric materials used for radionuclide partitioning from HLLW in MAREC process

Summary To separate minor actinides from HLLW by extraction chromatography, a few novel silica-based di(2-ethylhexyl)phosphoric acid (HDEHP), 4,4¢,(5¢)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6), octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), and N,N,N¢,N¢-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric adsorption materials (HDEHP/SiO₂-P, DtBuCH18C6/SiO₂-P, CMPO/SiO₂-P, and TODGA/SiO₂-P) were synthesized by impregnating HDEHP, DtBuCH18C6, CMPO, and TODGA into the pores of porous SiO₂-P particles, which were the new kind of inorganic/organic composites consisted of macroporous SiO₂ and copolymer. The bleeding behavior of these composites was investigated by examining the effect of contact time and HNO₃ concentration. It was found that in the tested HNO₃ concentration range, a noticeable quantity of DtBuCH18C6, at least 600 ppm, leaked out from DtBuCH18C6/SiO₂-P because of the protonation of DtBuCH18C6 with hydrogen ion, while the others were lower and basically equivalent to the solubility of HDEHP, CMPO, or TODGA in corresponding acidities solutions. Based on the batch experiment, the bleeding of CMPO/SiO₂-P and TODGA/SiO₂-P, the main adsorbents used in MAREC process for HLLW partitioning, was evaluated by column operation in 0.01M HNO₃ and 3M HNO₃. The quantity of CMPO leaked was ~48 ppm in 0.01M HNO₃ and ~37 ppm in 3.0M HNO₃. The bleeding of TODGA decreased from 23.2 ppm to 7.27 ppm at the initial stage and then basically kept constant. An actual bleeding of TODGA was evaluated by the separation of Sr(II) from a 2.0M HNO₃ solution containing 5.0 ^. 10^-3M of 6 typically simulated elements.     

Challenges to develop single-column MA(III) separation from HLLW using R-BTP type adsorbents

In order to directly separate trivalent minor actinides(MA:Am,Cm) from fission products(FP) containing rare earths(RE) in high level radioactive liquid waste(HLLW),the authors have challenged to develop a simplified MA separation process by extraction chromatography using a single column.Attention has been paid to a new type of nitrogen-donor ligands,R-BTP(2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl) pyridine,R:alkyl group) as an extractant because it shows high extraction selectivity for Am(Ⅲ) over RE(Ⅲ).It is known that the R-BTP ligands show different properties such as adsorbability and stability by having different alkyl groups.Therefore,some novel adsorbents were prepared by impregnating different types of R-BTP ligands(isohexyl-,isoheptyl-and cyheptyl-BTP) and a similar ligand to the R-BTP,ATP(2,6-bis(1-aryl-1H-tetrazol-5-yl)pyridines),into the porous silica/polymer support(SiO2-P particles).This work deals with comparison in adsorption and desorption properties of Am and some FP in HNO 3 solution onto such R-BTP type adsorbents,as well as chemical and radiolytic stability of the adsorbents.Then the possibility of a single-column separation of MA from main FP was pursued by evaluating the results of column experiments using the most promising adsorbent(isohexyl-BTP/SiO2-P) under temperature control.In addition,elution behaviors of U and Pd were also estimated.     

SPEC Process II. Adsorption of strontium and some typical co-existent elements contained in high level liquid waste onto a macroporous silica-based crown ether impregnated functional composite

To separate Sr(II), one of the heat emitting nuclides, from high level liquid waste (HLLW), a macroporous silica-based DtBuCH18C6 polymeric composite, DtOct/SiO₂-P, was synthesized by means of molecular modification of 4,4′,(5′)-di(tert-butylcyclohexano)-18-crown-6 (DtBuC H18C6) with a long-chain 1-octanol. It was performed by impregnating and immobilizing DtBuCH18C6 and 1-octanol molecules into the pores of the SiO₂-P particles, the macroporous silica-based support. The adsorption of Sr(II) and some co-existent typical elements Na(I), K(I), Cs(I), Ru(III), Mo(VI), Pd(II), Ba(II), La(III), and Y(III) contained in highly active liquid waste (HLW) towards DtOct/SiO₂-P was investigated at 323 K. The effects of contact time and the concentration of HNO₃ in a range of 0.1–5.0M on the adsorption of the tested metals were examined. The macroporous silica-based DtOct/SiO₂-P polymeric composite showed strong adsorption ability and high selectivity for Sr(II) over all of the tested metals except Ba(II). The optimum acidity of Sr(II) adsorption onto DtOct/SiO₂-P was determined to be 2.0M HNO₃. The bleeding behavior of DtOct/SiO₂-P in aqueous phase was evaluated using total organic carbon (TOC) analysis. The content of TOC increased with increasing the HNO₃ concentration and contact time. It resulted from the decrease in the stability of the associated species, C₈H₁₇-OH• DtBuCH18C6 formed through hydrogen binding, because of high temperature.     

Adsorption characteristics and radiation stability of a silica-based DtBuCH18C6 adsorbent for Sr(II) separation in HNO3 medium

A silica-based adsorbent, (DtBuCH18C6 + dodecanol)/SiO₂-P, which is used for selective separation of Sr(II) from high level liquid wastes, against temperature and gama-irradiation was investigated. The adsorption characteristics of Sr(II), Ba(II), La(III), Nd(III), Gd(III) and Dy(III) under varying nitric acid concentration at different temperatures were measured by batch method. The adsorbent showed higher distribution coefficients (K _d) for Sr(II) compared to other tested metal ions, and the K _d values of Sr(II) decreased with increasing temperature. Thermodynamic parameters of the adsorption process were calculated. The related parameters in adsorption isotherm models were obtained using a non-linear fitting. Uptake capacity from 0.38 to 0.43 mmol g^?1 was obtained for Sr(II) in the temperature range of 298–323 K by the Langmuir equation fitting. The leakage of total organic carbon was below 120 ppm at 298 K and 180 ppm at 323 K, respectively. The degradation of the adsorbent irradiated in 2 M HNO₃ was investigated. It is found that the adsorbed dose of γ-ray more than 50 KGy has a strong influence on K _d of Sr(II). The K _d values of Sr(II) decrease about 3 times ranged from 50 to 500 KGy.     

Modification of a novel macroporous silica-based crown ether impregnated polymeric composite with 1-dodecanol and its adsorption for some fission and non-fission products contained in high level liquid waste

A novel macroporous silica-based chelating polymeric composite, DtDo/SiO₂-P, was synthesized by molecular modification of 4,4′,(5′)-di-(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) with a long carbon chain organic compound 1-dodecanol. It was performed through impregnation and immobilization of DtBuCH18C6 and 1-dodecanol molecules into the pores of the SiO₂-P particles. The adsorption of a few fission and non-fission product elements 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 at 323 K. The effects of contact time and the HNO₃ concentration in a range of 0.1-4.0 M were investigated. It was found that at the optimum concentration of 2.0 M HNO₃, DtDo/SiO₂-P exhibited strong adsorption ability and excellent selectivity for Sr(II) over all of the tested elements, which showed very weak or almost no adsorption except Ba(II). The bleeding of total organic carbon (TOC) from DtDo/SiO₂-P was evaluated. The quantity of TOC in aqueous phase increased with an increase in HNO₃ concentration in terms of a linear equation [TOC] = 35.82[HNO₃] + 115.5 with a correlation coefficient of 0.9751. The TOC content leaked from DtDo/SiO₂-P modified by 1-dodecanol, 119.0-269.3 ppm, in the range of 1.0-4.0 M HNO₃ was significantly lower than that of 424.8-634.6 ppm in the case without modification. It resulted from the intermolecular interaction force of DtBuCH18C6 and 1-dodecanol through hydrogen bonding. The reduction of DtBuCH18C6 leakage by molecular modification was achieved. It is of great benefit to application of DtDo/SiO₂-P in partitioning of Sr(II), one of the main heat generators, from high level liquid waste (HLLW) in reprocessing process of nuclear spent fuel in MAREC (Minor Actinides Recovery from HLLW by Extraction Chromatography) process developed.     

Preparation of a novel macroporous silica-based 2,6-bis(5,6-diisobutyl-1,2,4-triazine-3-yl)pyridine impregnated polymeric composite and its application in the adsorption for trivalent rare earths

A novel macroporous silica-based 2,6-bis(5,6-diisobutyl-1,2,4-triazine-3-yl)pyridine (iso-Bu-BTP), a neutral chelating agent having several softatom nitrogen, polymeric composite (iso-Bu-BTP/SiO₂-P) was synthesized. It was done through impregnation and immobilization of iso-Bu-BTP molecule into the pores of SiO₂-P particles with 40–60 μm of bead diameter and 0.6 μm of mean pore size. The effective impregnation resulted from the intermolecular interaction of iso-Bu-BTP and co-polymer inside the SiO₂-P particles by a vacuum sucking technique. To understand the possibility of applying iso-Bu-BTP in the MAREC process developed, the adsorption behavior of a few representative rare earths (REs) such as Ce(III), Nd(III), Gd(III), Dy(III), Er(III), Yb(III), and Y(III) towards iso-Bu-BTP/SiO₂-P was investigated at 298 K. The influence of the HNO₃ concentration in a wide range of pH 5.52–3.0M and a few chelating agents such as formic acid, citric acid, and diethylenetriaminepentaacetic acid (DTPA) on the adsorption of RE(III) was examined. It was found that in the presence of chelating agent, the adsorption ability of the tested RE(III) towards iso-Bu-BTP/SiO₂-P decreased due to two competition reactions of RE(III) with iso-Bu-BTP/SiO₂-P and chelating agents. In a 0.01M HNO₃ solution containing 1M formic acid or 1M citric acid, light RE(III) showed lower adsorption towards iso-Bu-BTP/SiO₂-P than that of the heavy one. This makes the separation of light RE(III) from the heavy one possible. Based on the similarity of minor actinides and heavy RE(III) in chemical properties and the results of column separation experiments, chromatographic partitioning of light RE(III) from a simulated high level liquid waste solution composed of the heavy RE(III) and minor actinides in MAREC process is promising.     

Synthesis and application of a macroporous silica-based polymeric octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide composite for the chromatographic separation of high level liquid waste

Summary The Minor Actinides Recovery from HLW by Extraction Chromatography (MAREC) process was used mainly for the separation of minor actinides (MAs) and some specific fission products (FPs) from highly active liquid waste (HLW) by the composite CMPO/SiO₂-P of the macroporous silica based polymeric octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide (CMPO) and others. In this study a cascade of chromatographic separation was performed on a 3.0M HNO₃ solution containing 5.0 ^. 10^-3M of 13 elements, at 323 K. The cascade consisted of three columns the first and second ones were packed with CMPO/SiO₂-P and the third with SiO₂-P particles. The first column was employed to prepare various eluents containing saturated CMPO. The second column was used for separation into groups. The CMPO of CMPO/SiO₂-P was recovered from the effluent by the third column and a CMPO-free effluent containing minor actinides was obtained. The elements contained in the simulated HLW of 3.0M HNO₃ were separated into (1) a non-adsorption group (Sr, Cs, and Ru etc.), (2) a MA-hRE (heavy rare earth)-Mo-Zr group, and (3) a lRE (light rare earth) group by eluting with 3.0M HNO₃, 0.05M DTPA (diethylenetriaminepentaacetic acid) (pH 2.0) and HNO₃ (pH 3.5), respectively. The resultant MA-hRE-Mo-Zr mixture containing minor actinides was then separated into the groups (1) Pd-Ru, (2) MA-hRE, and (3) Mo-Zr by utilizing 3.0M HNO₃, distilled water, and 0.05M DTPA (pH 2.0) as eluents. More than 92% of CMPO in the MA-hRE containing effluent was adsorbed by SiO₂-P particles. The effectivity and technical feasibility of MAREC process were demonstrated.     

Study on selective separation of cesium from high level liquid waste using a macroporous silica-based supramolecular recognition absorbent

A macroporous silica-based supramolecular recognition absorbent (Calix[4]?+?Dodecanol)/SiO₂?CP, was prepared by successive impregnation and fixing the 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-Calix[4]arene (Calix[4]arene-R14) and its molecule modifier 1-Dodecanol onto SiO₂ silica-based polymer support. The characterization of (Calix[4]?+?Dodecanol)/SiO₂?CP was examined by thermal gravimetry and differential thermal analysis and electron probe microanalysis. Relatively large separation factors of Cs and other metal ions (?? _Cs/M ⁿ⁺ ) above 60 were obtained in the presence of 3?M HNO₃. The adsorption data of Cs(I) fitted well with Langmuir isotherm and the maximum adsorption capacity was estimated to be 0.19?mmol?g^?1. The Cs(I) in 3?M HNO₃ were also effectively adsorption on (Calix[4]?+?Dodecanol)/SiO₂?CP in the column operation, and the loaded Cs(I) was successfully eluted with an eluent of H₂O. The column packed with (Calix[4]?+?Dodecanol)/SiO₂?CP had excellent reusability after three cycles.     

Synthesis and characterization of a novel organic–inorganic hybrid supramolecular recognition material and its selective adsorption for cesium

To separate Cs(I) from highly active liquid waste, a macroporous silica-based 25, 27-bis(iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/SiO₂–P, was synthesized and characterized by SEM, FT-IR, and TG-DSC. The adsorption properties of BiPCalix[4]C6/SiO₂–P and a macroporous polymer-based supramolecular recognition composite, BiPCalix[4]C6/XAD-7, were compared. It was found that BiPCalix[4]C6/SiO₂–P exhibited better adsorption ability and faster adsorption dynamics than BiPCalix[4]C6/XAD-7. The adsorption isotherm of Cs(I) onto BiPCalix[4]C6/SiO₂–P was studied at 298 K and it was well described by Langmuir isotherm model. The complex composition between BiPCalix[4]C6/SiO₂–P and Cs(I) was determined as 1:1 type by investigating the effect of the concentrations of BiPCalix[4]C6, Cs(I), and H⁺ on the adsorption. Meanwhile, the selectivity of BiPCalix[4]C6/SiO₂–P towards Na(I), K(I), Rb(I), Cs(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) was investigated.     

Validation of a Monte Carlo HPGe detector model against irradiated foil gamma-ray spectroscopy measurements

In order to separate and pre-concentrate uranium from aqueous phase, a novel silica-based adsorbent was prepared by impregnating nalidixic acid (HNA) into a macroreticular silica/polymer composite support (SiO₂-P) with a mean diameter of 60 μm. Adsorption behavior of uranium from aqueous solution onto the adsorbent was studied. Experimental results indicated that HNA/SiO₂-P showed strong adsorption for uranium in a wide range of pH from 3.5 to 10.0, and the maximum adsorption capacity was 35.4 mg g⁻¹. In addition, HNA/SiO₂-P exhibited good selectivity for U(VI) and showed weak or bare adsorption affinity to foreign ions. Kinetic and isotherm of uranium adsorption were in accordance with the pseudo-second-order kinetic model and Langmuir isotherm adsorption model, respectively. Moreover, U(VI) sorption was found to be an endothermic reaction and spontaneous under experimental state. The synthesized adsorbent showed an admirable stability at lower pH values in aqueous solution.

     

Separation and purification of 90Sr from PUREX HLLW using N,N,N′,N′-tetra(2-ethylhexyl) diglycolamide

This paper describes a method for the separation and purification of ⁹⁰Sr from PUREX–HLLW employing solvent extraction and precipitation techniques. 30 % TBP in n-dodecane was used for the removal of residual uranium, plutonium and neptunium from HLLW. Trivalent actinides and lanthanides were subsequently removed using N,N,N’,N’-tetra(2-ethylhexyl) diglycolamide (TEHDGA, 0.20 M in 30 % isodecyl alcohol and n-dodecane). ⁹⁰Sr was selectively extracted from actinides and lanthanides depleted HLLW using 0.3 M TEHDGA in 5 % isodecyl alcohol and dodecane. Loaded strontium was stripped using 0.01 M HNO₃ and further purified by radiochemical precipitation technique after adding Fe and natural strontium as carriers. Based on the experimental results, a flow-sheet was formulated and mCi levels of ⁹⁰Sr recovered.     

Studies on the separation treatment of high-level liquid waste by bisamide podand(I): Extraction and separation of An(III) from Ln(III)

A process for actinide(III) and lanthanum(III) extraction separation from high-level liquid waste (HLLW) was proposed, with N,N,N',N'-tetraoctyl diglycolamide (TODGA) as the extractant, tri-n?butyl phosphate (TBP) as the phase modifier and 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl]pyridine (PyTri-Diol or PTD) as hydrophilic stripping agent. This ‘hot test’ was successfully carried out, achieving 99.92% removal of americium-241 (²⁴¹Am) with a separation factor SF_(Eu/Am) of 3.8 × 10³ in the actinide(III) product solution. The results show that bisamide podand extractants can effectively realize the extraction and separation of actinide(III) and lanthanum(III) from Chinese commercial HLLW and thus have a bright practical application potential for the treatment of commercial HLLW.     

Adsorption of UO2 2+ on poly(N,N-diethylacrylamide-co-acrylic acid): effects of pH, ionic strength, initial uranyl concentration, and temperature

We prepared poly(N,N-diethylacrylamide-co-acrylic acid) (P(DEA-co-AA)) microgels which could efficiently remove UO₂ ²⁺ from aqueous solutions. In this study, the effect of adsorption parameters such as pH value, adsorbent dose, shaking time, and temperature has investigated. It is found that the pseudo-second-order model is more suitable for our experiment. The adsorption kinetic data indicated that the chemical adsorption was the swiftness processes, the adsorption equilibrium could be achieved within 30 min. And there are very good correlation coefficients of linearized equations for Langmuir isotherm model, which indicated that the sorption isotherm of the hydrogel for UO₂ ²⁺ can be fitted to the Langmuir isotherm model. The adsorption process was spontaneous (?G ⁰ < 0) and exothermic (?H ⁰ < 0). The adsorbed UO₂ ²⁺ can be desorbed effectively by 0.1 M HNO₃ and the adsorption capacity is not significantly reduced after five cycles. Present study suggests that this P(DEA-co-AA) can be used as a potential adsorbent for sorption UO₂ ²⁺ and also provide a simple, fast separation method for removal of UO₂ ²⁺ ions from aqueous solution.