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1.
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).  相似文献   

2.
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.  相似文献   

3.
The solid state structure of [Ru(Phtpy)2][PF6]2 · 4MeCN has been determined (Phtpy = 4′-phenyl-2,2′:6′,2″-terpyridine); [Ru(Phtpy)2]2+ cations pack into sheets by virtue of {M(tpy)2}2 embraces, and the MeCN solvent molecules are involved in NH–C interactions which prevent the efficient packing of adjacent sheets. Comparisons with related structures lead to some generalizations about packing motifs in salts containing [M(Phtpy)2]2+ or [M(pytpy)2]2+ cations (pytpy = 4′-pyridyl-2,2′:6′,2″-terpyridine).  相似文献   

4.
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.  相似文献   

5.
Cation exchange polymer particles have been synthesized for urinalysis to monitor levels of strontium-90 (90Sr) exposure in humans. Two techniques were utilized in the incorporation of a Sr2+ selective chelating agent, di-tert-butyl-cyclohexano-18-crown-6 (DtBuCH18C6). The ion imprinting technique involved entrapment of DtBuCH18C6 during the formation of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) polymer particles. In the surface immobilization technique, adsorption of DtBuCH18C6 onto the surface of AMPS polymer particles was assisted by a molecular modifier. Ethylene glycol dimethacrylate (EGDMA) and divinylbenzene (DVB) were evaluated as cross-linking agents to provide better support for DtBuCH18C6. These polymer particles were characterized by scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. Radiometric binding assays demonstrated that surface immobilization, in comparison to matrix imprinting, achieved greater Sr2+ uptake. Application of the surface immobilized particles in urinalysis was successful, attaining 86 ± 2% 90Sr uptake at pH 9.  相似文献   

6.
TiO2–SiO2 monolithic aerogels were homogeneously prepared using sol–gel method. Critical point of drying of TiO2–SiO2 gels with ethanol was studied for 30, 60, 90 and 120 min. Subsequently, the gels were dried with supercritical ethanol, resulting in amorphous aerogels that crystallized following heat treatment at 550 °C from 1 to 5 h. The TiO2–SiO2 aerogels were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface area measurements. The molar ratio of SiO2:TiO2 was 6 and the synthetic strategy revealed that TiO2–SiO2 aerogel, had a surface area 868 m2/g, particle size 40 nm, density 0.17 g/cm3 and 80% porosity. The finding indicated that from economic point of view, TiO2–SiO2 gel should be supercritical dried for 30 min and heat-treated for 5 h. The TiO2–SiO2 aerogel monoliths photocatalyst synthesized using sol–gel method provided insight into the characteristics that make a photocatalyst material well-suited for photodegradation of phenol and cyanide in an industrial waste stream containing Cl, S2− and NH4+. Interestingly, after multiple reuse cycles (i.e. ≥7), photodegradation systems with regenerated photocatalyst showed a slightly decreasing of photoactivity 2–4%. The overall kinetics of photodegradation of either phenol or cyanide using TiO2–SiO2 aerogel photocatalyst was found to be of first order.  相似文献   

7.
Two novel Zn(II) coordination polymers, [Zn5(pytpy)8(fum)4(H2O)4(OH)2]n · n(CH3OH) · 2n(H2O) (1) and [Zn3(pytpy)4 (btc)2]n · 2n(H2O) (2) (pytpy = 4′-(4-pyridyl)-3,2′:6′,3″-terpyridine, H2fum = fumaric acid, H3btc = 1,3,5-benzenetricarboxylic acid) have been hydrothermally synthesized and structurally characterized. Complex 1 is a 2D layer structure, which is constructed from linear pentanuclear Zn(II) subunits interconnected via bidentate-bridging pytpy ligands and tridentate-bridging fum2− anions. Complex 2 is a 3D network structure, μ2-pytpy ligands link the layers based on the heart-like hexanuclear subunits to form the 3D network. Both complexes show strong fluorescence emission upon excitation at 310 nm in solid state. Additionally, these two complexes possess great thermal stabilities, especially for 2, the framework is stable up to 350 °C.  相似文献   

8.
The co-extraction of strontium and cesium from nitric acid medium by di-tert-butylcyclohexano-18-crown-6 (DtBuCH18C6) and 1,3-di(2-propoxy)calix[4]arene-crown-6 (iPr-C[4]C-6) in n-octanol was studied. The effects of contact time, nitric acid concentration, extractant concentration and temperature on the co-extraction behavior were systematically investigated. Effective extraction of the two metals was achieved under a variety of conditions. The co-extraction from a simulated high-level liquid waste (HLLW) was also conducted, and strontium and cesium could be selectively extracted in the presence of a large number of other metals. Results in this work illustrate the feasibility of partitioning radioactive strontium and cesium simultaneously from HLLW by a mixture of DtBuCH18C6 and iPr-C[4]C-6 in n-octanol.  相似文献   

9.
Abstract

A novel 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. It was prepared by impregnation and the immobilization of the BiPCalix[4]C6 molecule into the pores of the macroporous SiO2-P particles. The adsorption of Cs(I) and some typical elements Na(I), K(I), Rb(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) onto the BiPCalix[4]C6/SiO2-P material was investigated. The effects of the HNO3 concentration, contact time, and temperature on the adsorption of the tested metals were studied. It was found that at the optimum concentration of 3.0 M HNO3, BiPCalix[4]C6/SiO2-P exhibited excellent adsorption ability and high selectivity for Cs(I) over all the tested elements, which showed weak or almost no adsorption except Rb(I). A pseudo-second-order model was found to be able to describe the adsorption kinetics of Cs(I). The chemical complexation of Cs(I) with BiPCalix[4]C6/SiO2-P was considered to be the rate-controlling step. Meanwhile, the thermodynamic parameters of the Cs(I) adsorption, ΔH?, ΔG?, and ΔS? were determined. The adsorption of Cs(I) onto BiPCalix[4]C6/SiO2-P was exothermic. It was demonstrated that in 3.0 M HNO3, the novel macroporous BiPCalix[4]C6/SiO2-P material shows promise for the partitioning of Cs(I) from highly active liquid waste.  相似文献   

10.
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  相似文献   

11.
SiO2–TiO2/montmorillonite composites were prepared under acidic, neutral and basic conditions and the solid acidity of the resulting composites were determined. All the SiO2/TiO2 ratio of the colloidal particles was set at 10 but the resulting SiO2/TiO2 ratios were significantly richer in TiO2. The XRD patterns of the acidic composite showed expanding and broadening of the (001) reflection by intercalation of colloidal SiO2–TiO2 particles, but the neutral and basic composites showed only broadening of the reflections and no intercalation. The specific surface areas of the acidic, neutral and basic composites (375, 237 and 247 m2/g, respectively) were much larger than of montmorillonite (6 m2/g). The average pore sizes were about 4, 15 and 50 nm, and the amounts of solid acidic sites measured by the NH3-TPD were 178, 95 and 86 µmol/g for the acidic, neutral and basic composites, respectively. The solid acid amount of the acidic composite was twice that of a commercial catalyst, K-10, (85 µmol/g) and much higher than the guest phase SiO2–TiO2 gel (16 µmol/g) or the host phase montmorillonite (6 µmol/g). The TPD peak temperatures reflect the acid strength, and were similar in all the samples, ranging from 175° to 200 °C.  相似文献   

12.
The synthesis and characterization of three new bis(2,2′:6′,2′-terpyridine) (tpy) ligands containing different hydrazone spacers between the metal-binding domains are described. Treatment of 1,4-benzenedicarbaldehyde bis(2,2′:6′,2′′-terpyridin-4′-ylhydrazone) (1) with [(tpy)RuCl3] in the presence of N-ethylmorpholine results in the formation of [(tpy)Ru(μ-1)Ru(tpy)]4+. Single crystal X-ray diffraction data for [(tpy)Ru(μ-1)Ru(tpy)][PF6]4·8MeCN confirm the ability of the hydrazone-based ligand to bridge two ruthenium(II) centres, providing proof-of-principle for the application of this class of flexible ligand in the design of coordination polymers.  相似文献   

13.
A new category of organosilica adsorbents functionalized with macrocyclic ligand cis-dicyclohexano-18-crown-6(cis-DCH18C6) were synthesized for selective strontium separation. The cis-DCH18C6 molecule, well-known as an excellent complexing agent of strontium, was elaborately modified for immobilization in the organosilica matrix by co-condensation. 13C and 29Si solid-state NMR, XPS, FT-IR, ESEM, and elemental analysis were employed to characterize the structure and surface morphology of the organosilicas. Due to the improved surface properties and supramolecular recognition to the ion, the functionalized organosilicas showed favorable adsorption capacity and selectivity to the strontium in HNO3 media. The sample of Crown-75 showed a high distribution coefficient (185.3 cm3/g) of strontium in 1 mol/L HNO3 solution. For practical purpose, the separation of strontium in the simulated high level liquid waste (HLLW) from the spent fuel of a light water reactor (LWR) was investigated. The Kds of strontium as well as dozens of other metals present in the HLLW were obtained. Moreover, the radiolytic and hydrolytic stability of the organosilicas was evaluated. It revealed that the organosilicas had excellent resistance against gamma-ray irradiation and nitric acid treatment. These novel DCH18C6-functionalized organosilicas possess a promising future for the separation of the strontium in radioactive liquid waste.  相似文献   

14.
A new dinuclear complex [Cu2(OAc)2(OH)(dpa)2] PF6 · H2O (1) is prepared and structurally and magneto-structurally characterized. The monocationic core contains one acetate in familiar bidentate η112-bridge and another in the rare monoatomic bridge along with one hydroxo intermediary. 1 packs through N–H…O and O–H…O hydrogen bonds and π…π interaction resulting a 3D supramolecular continuum and displays high-energy intraligand 1(π − π*) fluorescence and intraligand 3(π − π*) phosphorescence in glassy solution.  相似文献   

15.
An experimental strategy was developed to obtain mesoporous SiO2–ZrO2 and SiO2–TiO2 mixed oxides by a sol–gel method, treating the gels hydrothermally. The solids were characterized by nitrogen physisorption, pyridine thermodesorption, 29Si nuclear magnetic resonance, SEM and X-ray diffraction. The effects of ZrO2 content, the generated pressure in the synthesis vessel and further modification of this type of procedure on the solids properties were studied. It was found that SiO2–ZrO2 and SiO2–TiO2 mixed oxides dried at atmospheric pressure developed type I isotherms. On the other hand, for the SiO2–ZrO2 and SiO2–TiO2 mixed oxides that were treated under pressure in the autoclave (at high SiO2 content) the porosity was improved and mesoporous materials exhibiting type IV adsorption isotherms. Specific surface area and pore size distribution were a function of ZrO2 and TiO2 content. The materials exhibited narrow pore size distributions with pore diameters in the region of mesopores at about 4 nm and high surface areas, the highest being 481 m2/g for the 10 wt% ZrO2 Si–Zr material. Differences in acidity as determined by pyridine thermodesorption were observed to depend on the synthesis parameters and ZrO2 and TiO2 concentration.  相似文献   

16.
《分离科学与技术》2012,47(17):2616-2625
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.  相似文献   

17.
The purpose of this study was the synthesis of lithium disilicate glass-ceramics in the system SiO2–Al2O3–K2O–Li2O. A total of 8 compositions from three series were prepared. The starting glass compositions 1 and 2 were selected in the leucite–lithium disilicate system with leucite/lithium disilicate weight ratio of 50/50 and 25/75, respectively. Then, production of lithium disilicate glass-ceramics was attempted via solid-state reaction between Li2SiO3 (which was the main crystalline phase in compositions 1 and 2) and SiO2. In the second series of compositions, silica was added to fine glass powders of the compositions 1 and 2 (in weight ratio of 20/100 and 30/100) resulting in the modified compositions 1–20, 1–30, 2–20, and 2–30. In the third series of compositions, excess of silica, in the amount of 30 wt.% and 20 wt.% with respect to the parent compositions 1 and 2, was introduced directly into the glass batch. Specimens, sintered at 800 °C, 850 °C and 900 °C, were tested for density (Archimedes’ method), Vickers hardness (HV), flexural strength (3-point bending tests), and chemical durability. Field emission scanning electron microscopy and X-ray diffraction were employed for crystalline phase analysis of the glass-ceramics. Lithium disilicate precipitated as dominant crystalline phase in the crystallized modified compositions containing colloidal silica as well as in the glass-ceramics 3 and 4 after sintering at 850 °C and 900 °C. Self-glazed effect was observed in the glass-ceramics with compositions 3 and 4, whose 3-point bending strength and microhardness values were 165.3 (25.6) MPa and 201.4 (14.0) MPa, 5.27 (0.48) GPa and 5.34 (0.40) GPa, respectively.  相似文献   

18.
Two series of Sr- or Ce-doped La1−xMxCrO3 (x = 0.0, 0.1, 0.2 and 0.3) catalysts were prepared by thermal decomposition of amorphous citrate precursors followed by annealing at 800 °C in air atmosphere. The effect of Ce and Sr on the morphological/structural properties of LaCrO3 was investigated by means of thermogravimetric/differential thermal analysis (TG/DTA) of the precursors decomposition under air, X-ray diffraction (XRD), electron paramagnetic resonance (EPR), transmission electron microscopy–X-ray energy dispersive spectroscopy (TEM–XEDS), SBET determination, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The characterization results are employed to explain catalytic activity results for C3H6 combustion. It is shown that the lanthanum chromite perovskite structure is obtained upon thermal treatment of the sol–gel derived precursors at T > ca. 800 °C. The presence of the dopant generally induces the formation of segregated oxide phases in the samples calcined at 800 °C although some introduction of the Sr in the perovskite structure is inferred from EPR measurements. The oxidation activity becomes maximised upon formation of such doped perovskite structure.  相似文献   

19.
Te-free and Te-containing Mo–V–Nb mixed oxide catalysts were diluted with several metal oxides (SiO2, γ-Al2O3, α-Al2O3, Nb2O5, or ZrO2), characterized, and tested in the oxidation of ethane and propane. Bulk and diluted Mo–V–Nb–Te catalysts exhibited high selectivity to ethylene (up to 96%) at ethane conversions <10%, whereas the corresponding Te-free catalysts exhibited lower selectivity to ethylene. The selectivity to ethylene decreased with the ethane conversion, with this effect depending strongly on the diluter and the catalyst composition. For propane oxidation, the presence of diluter exerted a negative effect on catalytic performance (decreasing the formation of acrylic acid), and α-Al2O3 can be considered only a relatively efficient diluter. The higher or lower interaction between diluter and active-phase precursors, promoting or hindering an unfavorable formation of the active and selective crystalline phase [i.e., Te2M20O57 (M = Mo, V, and Nb)], determines the catalytic performance of these materials.  相似文献   

20.
A polyoxometalate-based compound, (bix)[Cu(bix)][Cu2(bix)2(P2W18O62)]·2H2O (1) (bix = 1,4-bis(imidazol-1-ylmethyl)benzene), was hydrothermally synthesized, and characterized by elemental analyses, IR spectroscopy, thermogravimetric analysis, and single X-ray diffraction. Compound 1 exhibits the 1D + 1D polypseudo-rotaxane structure consists of two parts: the P2W18–Cu2–(bix)2 chain which contains 26-membered Cu2(bix)2 macrocycles and the 1D Cu-bix line. Remarkably, it represents the first polypseudo-rotaxane structure based on the Wells–Dawson polyoxometalate.  相似文献   

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