Selective removal of cesium and strontium by crystalline silicotitanates

Crystalline silicotitanate ion exchanger (58.5 mmol Ti, and 620 mmol Na) with 6 mmol of SiO₂ after 10 days of hydrothermal synthesis was optimized for selective removal of ⁹⁰Sr. Studies on X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy revealed that the silicotitanate is highly crystalline with bright cubic and rod like morphology with varying amounts of Ti, Si, Na, and O. The decontamination factor and distribution coefficient values for uptake of ¹³⁷Cs and ⁹⁰Sr from actual radioactive waste solutions by the ion exchanger after 24 h of equilibration was found to be 40 and 176 and 4025 ml g^?1 and 7525 ml g^?1, respectively. The exchange capacity for ⁹⁰Sr and ¹³⁷Cs was estimated to be 14.6 and 4.4 meq g^?1, respectively.     

Uptake of cesium and strontium by crystalline silicotitanates from radioactive wastes

Crystalline silicotitanate inorganic ion exchanger, with a sitinakite structure is candidate material for remediation of aqueous nuclear waste streams. The syntheses of crystalline silicotitanate (CST) and Nb-substituted crystalline silcotitanate (Nb-CST) were carried out under hydrothermal conditions and the products were characterized using techniques viz., XRD, SEM/EDS, DTA/TGA, surface area respectively. Batch experiments were carried out to study the kinetics of uptake of ¹³⁷Cs and ⁹⁰Sr, to estimate the decontamination factor (DF) values and distribution coefficients (K _d) for the above synthesized CST and Nb-CST samples from actual radioactive waste solutions. The DF values for uptake of Cs and Sr by Nb-CST after 24 h of equilibration was 355 and 136 whereas for CST it was found to be 40 and 176 respectively. The K _d values for uptake of Cs and Sr for Nb-CST after 24 h of equilibration was found to be 35,490 and 13,500 mL/g respectively whereas the K _d values for uptake of Cs and Sr for CST was found to be 4,025 and 17,525 mL/g respectively. The ion exchange capacity of Nb-CST towards ⁹⁰Sr and ¹³⁷Cs was estimated to be 11.8 and 3.2 meq/g respectively whereas the ion exchange capacity of CST towards ⁹⁰Sr and ¹³⁷Cs was estimated to be 14.6 and 4.4 meq/g respectively.     

Separation of Sr in combination of ion exchange and Sr resin with alcohol-nitric acid solution and rapid determination of <Superscript>90</Superscript>Sr in wine and soil samples

This paper describes the procedures of isolating strontium from wine and soil samples which enable creating of procedure for rapid determination of ⁹⁰Sr. The method of determination of ⁹⁰Sr includes binding of Sr on the cationic exchanger IR-120 from the sample and simultaneous elution from the cation column and binding on the Sr column, separation of Sr on Sr resin with HNO₃ even in presence of alcohols and subsequent Cherenkov counting. Sr can be efficiently bind on Sr resin and separated from the other elements with lower acid concentrations in the presence of a low portion of alcohol, or even from a wine sample without the loss of Sr resin capacity. The binding strength of Sr on Sr resin decreases with the rising of HNO₃ concentration (1–5 M) in the presence of 13% of ethanol or methanol, and with the rising of the alcohol portion in constant concentration of HNO₃. Application of cation exchanger for Sr binding in phase of sample preparation decreases Sr column loading and improve Sr recovery. The method allows the determination of ⁹⁰Sr activities in wine and soil sample lower than 10 mBq in reasonable time.     

Feasibility study of an analytical method for detecting <Superscript>90</Superscript>Sr in soil using DGA resin and Sr resin

This study investigated an analytical method for detecting ⁹⁰Sr in soil samples for the routine monitoring of environmental radioactivity. Mineral acid leaching and fusion methods were first used to digest the soil sample, and the analytical results were compared. DGA resin was employed to separate ⁹⁰Y, being a daughter of ⁹⁰Sr. Then, ⁹⁰Y was analyzed by liquid scintillation counter (LSC). These analytical results were compared with those obtained using Sr resin, which is a well-known, simple and reliable separation method. With the DGA resin approach a minimum detectable activity of ~0.28 Bq kg^?1 was detected in a 50 g sample, with 180 min of counting time, 70% recovery and ~97% counting efficiency using a LSC.     

High CO2‐Capture Ability of a Porous Organic Polymer Bifunctionalized with Carboxy and Triazole Groups

A new porous organic polymer, SNU‐C1 , incorporating two different CO₂‐attracting groups, namely, carboxy and triazole groups, has been synthesized. By activating SNU‐C1 with two different methods, vacuum drying and supercritical‐CO₂ treatment, the guest‐free phases, SNU‐C1‐va and SNU‐C1‐sca , respectively, were obtained. Brunauer–Emmett–Teller (BET) surface areas of SNU‐C1‐va and SNU‐C1‐sca are 595 and 830 m²g^?1, respectively, as estimated by the N₂‐adsorption isotherms at 77 K. At 298 K and 1 atm, SNU‐C1‐va and SNU‐C1‐sca show high CO₂ uptakes, 2.31 mmol g^?1 and 3.14 mmol g^?1, respectively, the high level being due to the presence of abundant polar groups (carboxy and triazole) exposed on the pore surfaces. Five separation parameters for flue gas and landfill gas in vacuum‐swing adsorption were calculated from single‐component gas‐sorption isotherms by using the ideal adsorbed solution theory (IAST). The data reveal excellent CO₂‐separation abilities of SNU‐C1‐va and SNU‐C1‐sca , namely high CO₂‐uptake capacity, high selectivity, and high regenerability. The gas‐cycling experiments for the materials and the water‐treated samples, experiments that involved treating the samples with a CO₂‐N₂ gas mixture (15:85, v/v) followed by a pure N₂ purge, further verified the high regenerability and water stability. The results suggest that these materials have great potential applications in CO₂ separation.     

Use of amorphous zirconium phosphate for the treatment of radioactive waste

Ion-exchange experiments were carried out for the removal of¹³⁷Cs, and⁹⁰Sr/⁹⁰Y radioisotopes by different cationic forms of amorphous zirconium phosphate. The effect of temperature and concentration on the percent uptake and distribution coefficients (K _d ) values (milli-equivalents of ion per gram of exchanger/milli-equivalents of ion per ml of solution) were determined. Experiments were made in simulated pond water at pH 11.4.     

Optimization of Nb-substitution and Cs+/Sr+2 ion exchange in crystalline silicotitanates (CST)

Crystalline silicotitanate inorganic ion exchanger, with a sitinakite structure is a candidate material for remediation of aqueous nuclear waste streams. Niobium substituted crystalline silicotitanates (Nb-CST) with varying concentrations of Nb (2, 4, 8, 12 and 24 mmol) and with constant concentrations of Ti-12 mmol, Si-16 mmol, Na-165 mmol were prepared hydrothermally and the products were characterized using techniques viz., XRD, SEM/EDS, DTA/TGA, surface area respectively. Batch experiments were carried out to study the kinetics of uptake of Cs¹³⁷ and Sr⁹⁰, to estimate the decontamination factor (DF) values and distribution coefficients (K _d) for the above synthesized Nb-CST samples from actual radioactive waste solutions. The DF values for uptake of Cs and Sr by Nb-CST for the optimized Nb-concentration of 4 mmol after 24 h of equilibration was 355 and 136 respectively. The K _d values for uptake of Cs and Sr for Nb-CST (Nb-4 mmol) after 24 h of equilibration was found to be 35,490 and 13,500 ml/g respectively. The ion exchange capacity of Nb-CST (Nb-4 mmol) towards Sr ⁹⁰ and Cs¹³⁷ was estimated to be 11.8 and 3.2 meq/g respectively.     

The preparation of covalent triazine‐based framework via Friedel‐Crafts reaction of 2,4,6‐trichloro‐1,3,5‐triazine with N,N′‐diphenyl‐N,N′‐di(m‐tolyl)benzidine for capturing and sensing to iodine

The covalent triazine‐based framework (TDPDB) has been prepared by Friedel‐Crafts polymerization reaction of N,N′‐diphenyl‐N,N′‐di(m‐tolyl)benzidine (DPDB) with 2,4,6‐trichloro‐1,3,5‐triazine (TCT) catalyzed by methanesulfonic acid. The yield of the reaction (94.85%) is very high. TDPDB was provided with Brunauer‐Emmett‐Teller specific surface area of 592.18 m² g^?1 and pore volume of 0.5241 cm³ g^?1. TDPDB demonstrated an excellent capacity for capturing iodine (3.93 g g^?1) and an outstanding ability to fluorescent sensing to iodine with Ksv of 5.83 × 10⁴ L mol^?1. It also showed high fluorescent sensing sensitivity to picric acid.     

Oligoether‐Strapped Calix[4]pyrrole: An Ion‐Pair Receptor Displaying Cation‐Dependent Chloride Anion Transport

A ditopic ion‐pair receptor ( 1 ), which has tunable cation‐ and anion‐binding sites, has been synthesized and characterized. Spectroscopic analyses provide support for the conclusion that receptor 1 binds fluoride and chloride anions strongly and forms stable 1:1 complexes ([ 1? F]^? and [ 1? Cl]^?) with appropriately chosen salts of these anions in acetonitrile. When the anion complexes of 1 were treated with alkali metal ions (Li⁺, Na⁺, K⁺, Cs⁺, as their perchlorate salts), ion‐dependent interactions were observed that were found to depend on both the choice of added cation and the initially complexed anion. In the case of [ 1? F]^?, no appreciable interaction with the K⁺ ion was seen. On the other hand, when this complex was treated with Li⁺ or Na⁺ ions, decomplexation of the bound fluoride anion was observed. In contrast to what was seen with Li⁺, Na⁺, K⁺, treating [ 1?F ]^? with Cs⁺ ions gave rise to a stable, host‐separated ion‐pair complex, [F ?1? Cs], which contains the Cs⁺ ion bound in the cup‐like portion of the calix[4]pyrrole. Different complexation behavior was seen in the case of the chloride complex, [ 1? Cl]^?. Here, no appreciable interaction was observed with Na⁺ or K⁺. In contrast, treating with Li⁺ produces a tight ion‐pair complex, [ 1? Li ? Cl], in which the cation is bound to the crown moiety. In analogy to what was seen for [ 1? F]^?, treatment of [ 1? Cl]^? with Cs⁺ ions gives rise to a host‐separated ion‐pair complex, [Cl ?1? Cs], in which the cation is bound to the cup of the calix[4]pyrrole. As inferred from liposomal model membrane transport studies, system 1 can act as an effective carrier for several chloride anion salts of Group 1 cations, operating through both symport (chloride+cation co‐transport) and antiport (nitrate‐for‐chloride exchange) mechanisms. This transport behavior stands in contrast to what is seen for simple octamethylcalix[4]pyrrole, which acts as an effective carrier for cesium chloride but does not operates through a nitrate‐for‐chloride anion exchange mechanism.     

Enhancing the Water Stability of Al‐MIL‐101‐NH2 via Postsynthetic Modification

The resistance of metal–organic frameworks towards water is a very critical issue concerning their practical use. Recently, it was shown for microporous MOFs that the water stability could be increased by introducing hydrophobic pendant groups. Here, we demonstrate a remarkable stabilisation of the mesoporous MOF Al‐MIL‐101‐NH₂ by postsynthetic modification with phenyl isocyanate. In this process 86 % of the amino groups were converted into phenylurea units. As a consequence, the long‐term stability of Al‐MIL‐101‐URPh in liquid water could be extended beyond a week. In water saturated atmospheres Al‐MIL‐101‐URPh decomposed at least 12‐times slower than the unfunctionalised analogue. To study the underlying processes both materials were characterised by Ar, N₂ and H₂O sorption measurements, powder X‐ray diffraction, thermogravimetric and chemical analysis as well as solid‐state NMR and IR spectroscopy. Postsynthetic modification decreased the BET equivalent surface area from 3363 to 1555 m² g^?1 for Al‐MIL‐101‐URPh and reduced the mean diameters of the mesopores by 0.6 nm without degrading the structure significantly and reducing thermal stability. In spite of similar water uptake capacities, the relative humidity‐dependent uptake of Al‐MIL‐101‐URPh is slowed and occurs at higher relative humidity values. In combination with ¹H‐²⁷Al D ‐HMQC NMR spectroscopy experiments this favours a shielding mechanism of the Al clusters by the pendant phenyl groups and rules out pore blocking.     

Determination of90Sr and137Cs in mushrooms following the Chernobyl fallout

After the Chernobyl accident high concentrations of radionuclides were found in Sweden in mushrooms and the contents of⁹⁰Sr and¹³⁷Cs were measured. The level of⁹⁰Sr was generally low and, in proportion to¹³⁷Cs, 2–3 orders of magnitude lower than in the fallut. The contents of¹³⁷Cs varied among species and extreme local variations occurred. The ratio¹³⁴Cs/¹³⁷Cs diverged from other biological samples leading to the conclusion that old fallout was involved in the uptake.     

Surface‐initiated ring‐opening polymerization of p‐dioxanone on Wang resin bead

Biodegradable poly(p‐dioxanone) (PPDO) was formed on Wang resin surface by surface‐initiated ring‐opening polymerization (SI‐ROP). The SI‐ROP of p‐dioxanone (PDO) was achieved by heating a mixture of Tin(II) bis(2‐ethylhexanoate) [Sn(Oct)₂], hydroxyl functionalized Wang resin, and PDO in anhydrous toluene at 80 °C. The resultant polymer‐grafted Wang resin (Wang‐g‐PPDO) was characterized by fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), optical microscopy (OM), and field‐emission scanning electron microscopy (FE‐SEM). The FTIR spectra of Wang‐g‐PPDO show peak characteristic of PPDO at 2943 cm^?1 (? C? H stretch), at 1741 cm^?1 (? C?O stretch), and 1136 cm^?1 (C? O? C stretch) indicating the formation of ester linkage between PPDO and hydroxyl terminated Wang resin. The DSC thermogram show melting peak corresponding to PPDO polymer on Wang resin surface. Thermogravimetric investigation shows increase in PPDO content on the Wang resin surface in terms of percentage of weight loss with increase in reaction time. The OM and SEM photographs clearly show the formation of PPDO polymer on the Wang resin surface without altering the spherical nature of Wang resin bead. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1178–1184, 2008     

Determination of137Cs and90Sr in milk by the static method with an ion exchanger

This paper presents the method of⁹⁰Sr and¹³⁷Cs determination from 10 litres of milk. The preconcentration is made by the static method with a strong acid cation exchanger (OSTION KS).¹³⁷Cs from the eluent (8M HCl) is selectively eliminated with ammonium molybdophosphate and then the^137mBa gamma activity measured, using NaI(T1) detector.⁹⁰Sr as⁹⁰Y is determined after achievement of the radioactive equilibrium and measured by flow proportional counter. The method appears to be accurate, reproducible and permits to determine³² mBq¹³⁷Cs and 13 mBq⁹⁰Sr in the samples.     

Synthesis and bio‐evaluation of Tc‐99 m‐labeled fatty acid derivatives for myocardial metabolism imaging

¹¹C, ¹⁸F and ¹²³I fatty acids are used for myocardial imaging, and ^99mTc‐labeled fatty acids are more desirable substitutes than other radiolabeled fatty acids. In the work reported, [^99mTc]‐CpTT‐10‐oxo‐FPA ( 1c ), [^99mTc]‐CpTT‐12‐oxo‐FPA ( 2c ), [^99mTc]‐CpTT‐14‐oxo‐FPA ( 3c ) and [^99mTc]‐CpTT‐16‐oxo‐FPA ( 4c ) were prepared with 60.76–70.92% of radiochemical yield and purity of more than 95%. These radiotracers ( 1c , 2c , 3c , 4c ) were chemically stable when incubated in Sprague Dawley rat serum for 3 h at 37 °C. Tissue distribution studies in female mice indicated that 2c had high initial heart uptake (8.84%ID g^?1 at 1 min post‐injection) and 4c had long retention in the heart (1.45%ID g^?1 at 30 min post‐injection). Metabolite analysis showed 4c could be metabolized to 5c via β‐oxidation with loss of two ? CH₂? in the myocardium, the radiometabolite being excreted via urine. However, low heart uptake suggested that 4c cannot be used as a diagnostic imaging agent. Copyright © 2016 John Wiley & Sons, Ltd.     

Sequential estimation of106Ru,137Cs,and90Sr in urine

A sequential method has been developed for the estimation of¹⁰⁶Ru,¹³⁷Cs, and⁹⁰Sr in urine using beta counting. After completely destroying the organic matter in urine,¹⁰⁶Ru is oxidized to volatile ruthenium tetroxide and allowed to reactin-situ with polyethylene powder;¹³⁷Cs is concentrated on ammonium phosphomolybdate and estimated as tetraphenylborate;⁹⁰Sr is coprecipitated as strontium sulphate and converted to carbonate. The recoveries have been found to be better than 83% for all of the radionuclides. The minimum detection limits are 0.16, 0.85, and 0.14 Bq/dm³ for¹⁰⁶Ru,¹³⁷Cs, and⁹⁰Sr, respectively. Yttrium-90 fraction of⁹⁰Sr is also estimated using sodium nitroprusside as reagent, after allowing it to grow for 14 days.This work forms part of the doctoral work of SRIM.V.R. PRASAD to be submitted to the University of Madras, under the supervision of DR. O.M. SREEDHARAN.     

An Azine‐Linked Covalent Organic Framework: Synthesis,Characterization and Efficient Gas Storage

A azine‐linked covalent organic framework, COF‐JLU2, was designed and synthesized by condensation of hydrazine hydrate and 1,3,5‐triformylphloroglucinol under solvothermal conditions for the first time. The new covalent organic framework material combines permanent micropores, high crystallinity, good thermal and chemical stability, and abundant heteroatom activated sites in the skeleton. COF‐JLU2 possesses a moderate BET surface area of over 410 m² g^?1 with a pore volume of 0.56 cm³ g^?1. Specifically, COF‐JLU2 displays remarkable carbon dioxide uptake (up to 217 mg g^?1) and methane uptake (38 mg g^?1) at 273 K and 1 bar, as well as high CO₂/N₂ (77) selectivity. Furthermore, we further highlight that it exhibits a higher hydrogen storage capacity (16 mg g^?1) than those of reported COFs at 77 K and 1 bar.     

Characterization and application of SuperLig<Superscript>®</Superscript> 620 solid phase extraction resin for automated process monitoring of <Superscript>90</Superscript>Sr

Characterization of SuperLig^® 620 solid phase extraction resin was performed in order to develop an automated on-line process monitor for ⁹⁰Sr. The main focus was on strontium separation from barium, with the goal of developing an automated separation process for ⁹⁰Sr in high-level wastes. High-level waste contains significant ¹³⁷Cs activity, of which ^137mBa is of great concern as an interference to the quantification of strontium. In addition barium, yttrium and plutonium were studied as potential interferences to strontium uptake and detection. A number of complexants were studied in a series of batch K_d experiments, as SuperLig^® 620 was not previously known to elute strontium in typical mineral acids. The optimal separation was found using a 2 M nitric acid load solution with a strontium elution step of ~0.49 M ammonium citrate and a barium elution step of ~1.8 M ammonium citrate. ⁹⁰Sr quantification of Hanford high-level tank waste was performed on a sequential injection analysis microfluidics system coupled to a flow-cell detector. The results of the on-line procedure are compared to standard radiochemical techniques in this paper.     

Radioanalytical determination of137Cs and89Sr in milk

Separation of Cs, Sr and Ca from their mixture was studied using solvent extraction and ion exchange techniques. More than 90% separation efficiency was achieved for Ca–Sr separation using ion exchange resin (Doulite C-20) while solvent extraction amounted to 88%. A proposed technique for determination of¹³⁷Cs and⁸⁹Sr in milk (after removal of organic matter) showed more than 80% accuracy for⁸⁹Sr determination and more than 90% for¹³⁷Cs determination.     

Poly(methyl methacrylate‐co‐pentaerythritol tetraacrylate‐co‐butyl methacrylate)‐g‐polystyrene: Synthesis and high oil‐absorption property

Well‐defined high oil‐absorption resin was successfully prepared via living radical polymerization on surface of polystyrene resin‐supported N‐chlorosulfonamide group utilizing methyl methacrylate and butyl methacrylate as monomers, ferric trichloride/iminodiacetic acid (FeCl₃/IDA) as catalyst system, pentaerythritol tetraacrylate as crosslinker, and L ‐ascorbic acid as reducing agent. The polymerization proceeded in a “living” polymerization manner as indicated by linearity kinetic plot of the polymerization. Effects of crosslinker, catalyst, macroinitiator, reducing agent on polymerization and absorption property were discussed in detail. The chemical structure of sorbent was determined by FTIR spectrometry. The oil‐absorption resin shows a toluene absorption capacity of 21 g g^?1. The adsorption of oil behaves as pseudo‐first‐order kinetic model rather than pseudo‐second‐order kinetic model. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Facilitated Ion‐Transfer of Sodium Cation by (Anthraquinone‐1‐yloxy) methane‐15‐crown‐5 Across the Water/1,2‐Dichloroethane Microinterface

The transfer of sodium cation facilitated by (anthraquinone‐1‐yloxy) methane‐15‐crown‐5 (L) has been investigated at the water/1,2‐dichloroethane microinterface supported at the tip of a micropipette. The diffusion coefficient of (anthraquinone‐1‐yloxy) methane‐15‐crown‐5 obtained was (3.42±0.20)×10^?6 cm² s^?1. The steady‐state voltammograms were observed for forward and backward scans due to sodium ion transfer facilitated by L with 1 : 1 stoichiometry. The mechanism corresponded to an interfacial complexation (TIC) and interfacial dissociation (TID) process. The association constant was calculated to be log β_o=11.08±0.03 in the DCE phase. The association constant of other alkali metals (Li⁺, K⁺, Rb⁺) were also obtained.