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1.
In the present investigation Br-82 radioactive isotope was used as a tracer to study the kinetics of exchange reaction taking
place between the ion exchange resin and the external bromide ion solution. In an attempt to study the reversible bromide
ion-isotopic exchange reaction kinetics, it was expected that whether the initial step was the exchange of radioactive bromide
ions from the solution on to the ion exchange resin (forward reaction), or from the ion exchange resin in to the solution
(reverse reaction), the two ion-isotopic exchange reactions should occur simultaneously, which was further confirmed from
the values of specific reaction rate 0.122 and 0.123 min −1 respectively obtained under identical experimental conditions. The radioactive tracer technique employed in the present investigation
will be useful for characterization of various industrial grade ion exchange resins. 相似文献
2.
In the present investigation, the 82Br radioactive isotope was used as a tracer to study the kinetics and mechanism of the exchange reaction between an ion exchange
resin and an external solution of bromide ions. In an attempt to study the reversible bromide isotope exchange reaction kinetics,
it was expected that whether the initial step was the exchange of radioactive bromide ions from the solution to the ion exchange
resin (forward reaction) or from the ion exchange resin to the solution (reverse reaction), the two ion-isotope exchange reactions
should occur simultaneously, which was further confirmed by the experimental values of specific reaction rates, 0.142 and
0.141 min −1, respectively. The results will be useful to standardize the process parameters so as to achieve optimum use of ion exchange
resins in various industrial applications.
The text was submitted by the authors in English. 相似文献
3.
The adsorption characteristics of phosphorylated Aspergillus niger (AN-P) for uranium(VI) were studied in this work. The AN-P was successfully prepared by the reaction of Aspergillus niger with phosphorus pentoxide in ice-bath under the catalysis of methanesulphonic acid. AN-P was characterized by FT-IR and SEM–EDS. The effects of pH, contact time, initial U(VI) ions concentration, adsorbent dosage and temperature on the adsorption of U(VI) by AN-P were investigated. The isotherm and kinetic data were accurately described by the Langmuir and pseudo-second-order models, respectively. The calculated thermodynamic parameters indicated that the adsorption of U(VI) by AN-P was an spontaneous and endothermic process. This indicated that the AN-P composite is a promising adsorbent for efficient removal of U(VI) from radioactive wastewater. 相似文献
4.
We measured quantitative spectra of firefly ( Photinus pyralis) bioluminescence in the presence of Zn 2+ and other bivalent metal ions to investigate the effects of these metal ions on luciferin‐luciferase reaction. We studied the dependence of the quantum yield and spectrum on quantity and kind of bivalent metal ions. Adding various amounts of Mg 2+, Mn 2+ and Ca 2+ produced virtually no change in the quantum yields or the spectra of bioluminescence. In contrast, increasing amounts of ions such as Zn 2+ and Cd 2+ decreased quantum yields and changed the bioluminescence color from yellow‐green to red. Quantitative analysis showed that the sensitivities of the quantum yield and color to various metal ions were in the order of Hg 2+>Zn 2+, Cd 2+>Ni 2+, Co 2+, Fe 2+≫Mg 2+, Mn 2+, Ca 2+. We propose that the changes in quantum yield and spectrum caused by the metal ions are due to their effect on luciferase that surrounds oxyluciferin during its radioactive decay. We also found that having more metal ions accelerated bioluminescence reactions. The sensitivity of the reaction rate had no correlation with those of the quantum yield and spectrum. 相似文献
5.
In the present investigation, 82Br radioactive isotope was used as a tracer to study the kinetics and mechanism of exchange reaction between an ion exchange
resin and an external bromide ion solution. In an attempt to study the reversible bromide ion isotopic exchange reaction kinetics,
it was expected that whether the initial step was the exchange of radioactive bromide ions from the solution into the ion
exchange resin (forward reaction) or from the ion exchange resin into the solution (reverse reaction), two ion isotopic exchange
reactions should occur simultaneously, which was further confirmed by the experimental specific reaction rates of 0.130 and
0.131 min −1, respectively. The results can be used to standardize process parameters so as to optimize the utilization of ion exchange
resins in various industrial applications.
The text was submitted by the authors in English. 相似文献
6.
The uptake of metal ions, cerium, Ce(III); cobalt, Co(II); thorium, Th(IV); and uranium U(VI) by Bacillus pumilus-LRW1, Bacillus cereus-LRW2 and Micrococcus lylae-LRW3 from aqueous solution was examined as a function of metal ion concentration, pH, temperature, and the presence of some foreign ions. The bacterial species exhibited high affinity to accumulate metal ions from their solutions at pH 4–5.0±0.5. The amount of each ion (in mg) accumulated by one gram dry weight of each bacteria was calculated. The uptake by the Bacillus cereus-LRW2 from aqueous solutions and simulated radioactive wastes were also investigated. Electron microscopic investigations showed that the ions were accumulated around the cell wall. 相似文献
7.
A radioactive multitracer solution was prepared from the reaction of selenium with 25 MeV/nucleon 40Ar ions. Using off-line -ray spectrometry, the solution containing 47 radioactive isotopes of 24 elements was obtained. The nucleide with the longest half-life was 22Na, and the shortest-lived one was 81Rb 8. 相似文献
8.
The ion exchange resins Duolite A-161 and Duolite A-162 in bromide form were equilibrated separately with the labeled radioactive
bromide ion solution of different concentrations varied from 0.005 to 0.100 M in the temperature range 25.0–45.0°C. The K
d values of bromide ions for Duolite A-162 were found to be higher than that for Duolite A-161 under similar experimental conditions.
The difference in K
d values of bromide ions for these two resins is produced by a swelling pressure depending on the water holding capacities. 相似文献
9.
This work is a study of lipase production by a Brazilian strain of Penicillium citrinum using an inexpensive and simple medium without organic nitrogen sources and of some important industrial properties, including
thermostability in relation to ionic strength. The maximal lipase activity (1585 U/L) was obtained when Penicillium citrinum was cultured on 0.75% ammonium sulfate complemented with minerals salts instead of yeast extract. Although this activity
was about 55% lower than that produced in medium with yeast extract (2850 U/L), the specific activity (7.8 U/mg proteins)
was higher than that obtained with the yeast extract (4.9 U/mg proteins). The morphology of fungus changed totally, with yeast
extract there are smooth, solid, and spherical pellets whereas on ammonium sulfate there are small “hairy” pellets uniformly
suspended in the medium. The effect of ferrous (Fe ++) ions was carried out using medium MA with and without Fe ++ ions. Lipase production by Penicillium citrinum in medium MA requires Fe ++ ions, the absence of which caused a decreased of about 50% in the specific activity (3.5 U/mg proteins). The utilization
of commercial, locally available oils as carbon sources, such as soybean oil (236 U/L) and corn oil (74 U/L) resulted in lower
activity compared to olive oil, showing that lipase production by Penicillium citrinum is specifically induced by olive oil. Potassium concentration in the medium can effects the production of lipase (1 mM (1585
U/L), 10 mM (1290 U/L), and 30 mM (1238 U/L), 50 mM (195 U/L), and 100 mM (2 U/L). The crude culture filtered was susceptable
to thermal deactivation. It was stable at pH 6.0, but was not stable at the optimum pH (8.0-8.5) at 50 mM. At the low ionic
concentration (1-25 mM) this lipase was stable at low pH (3.5-4.0). The activation energy was 22.4 ±2.2 Kcal. mol 1. 相似文献
10.
This study concerns the removal of the 137Cs + and 60Co 2+ β+γ-radioactive ions in Azolla caroliniana Willd. water fern. The living fern and two different types of biosorbent prepared from Azolla caroliniana were tested to remove the above-mentioned radioactive ions from dilute solutions, in the absence and in the presence of the
ionic competition. Effective 137Cs + and 60Co 2+ ions removal from low radioactive wastewaters was demonstrated. The time dependent K
d
( t) values were calculated from the absorption data. These results indicate that removal process achieved equilibrium in about
120 min and that it involves two steps: rapid and slow absorption; the active process (metabolic bioaccumulation on the living
fern) was responsible for above one half of the total removal process. A thin layer radiochromatography study leads to the
conclusion that the biochemical components in which 137Cs + and 60Co 2+ place themselves are of a polysaccharide and lipoid fractions. 相似文献
11.
To gain new insight into the antimicrobial potential of Ailanthus altissima Swingle, ethanol leaf extracts were evaluated for the antifungal effects against the model yeast Saccharomyces cerevisae. The extracts inhibited the yeast growth in a dose-dependent manner, and this effect could be augmented by heat shock, exposure to visible light or exposure to high concentrations of Ca 2+. Using transgenic yeast cells expressing the Ca 2+-dependent photoprotein, aequorin, it was found that the leaf extracts induced cytosolic Ca 2+ elevation. Experiments on yeast mutants with defects in Ca 2+ transport demonstrated that the cytotoxicity of the A. altissima leaf extracts (AaLEs) was mediated by transient pulses of Ca 2+ ions which were released into the cytosol predominantly from the vacuole. The investigation of the antifungal synergies involving AaLEs may contribute to the development of optimal and safe combination therapies for the treatment of drug-resistant fungal infections. 相似文献
12.
Microfluidic approaches have demonstrated a relevant impact on radiochemical reactions involving Positron Emission Tomography (PET) nuclides, due to shorter reaction times and smaller precursor quantities. However, little attention has been given to the integration of the initial pre-concentration and drying of radioactive [(18)F]fluoride ions, required for the labeling of radiotracer compounds. In this work we report the design, fabrication and implementation of a glass microfluidic device filled with recyclable anion exchange particles for the repeated recovery of [(18)F] and [(19)F]fluoride ions. The device was first tested with non radioactive [(19)F]fluoride ions and it was shown to repeatedly trap and elute >95% fluoride over 40 successive experimental runs with no decrease in efficiency. The same device was then tested for the trapping and release of [(18)F]fluoride ions over 20 experiments with no measurable decrease in performance. Finally, the [(18)F]fluoride ions were eluted as a K(18)F/K2.2.2 complex, dried by repeated dissolution in acetonitrile and evaporation of residual water, and reacted with ethyl ditosylate (EtDT) leading to the desired product ([(18)F]fluoroethyltosylate) with 96 ± 3% yield (RCY). The overall time needed for conditioning, trapping, elution and regeneration was less than 6 min. This approach will be of great benefit towards an integrated platform able to perform faster and safer radiochemical synthesis on the micro-scale. 相似文献
13.
Fixation of 137Cs, 144Ce, 60Co, 90Sr, 240Th and 233U from aqueous and phosphate media on bentonite clay was studied. The fixation of the radioactive ions on bentonite surfaces
was dependent on the pH behavior of the metal ions. A method was proposed to use bentonite as an absorbent of ions from simulated
radioactive waste as a treatment step. 相似文献
14.
The radioactive tracer method was used to investigate the adsorption of iodide and europium ions from aqueous solution on dried isoelectric precipitates of silver sulfide, silver iodide and silver bromide. The relationship between the amount of iodide ions adsorbed on Ag 2S and the iodide ion and HNO 3 concentrations in the solution was determined. It was shown that the iodide ions adsorbed on Ag 2S could be desorbed with sulfide ions. Using Ag 2S, AgI and AgBr precipitates, a relationship between the europium ion adsorption and Eu(NO 3) 3, H 2S, NaI, NaBr and NaCl concentration in solution was established. The adsorption of europium ions was also assessed in respect to the presence of lanthanum and barium ions. For adsorption measurement iodide and europium ions were labeled with their radioactive isotopes and the amounts adsorbed were determined from the measured radioactivities of the precipitates after reaching the equilibrium between the solid phase and the solution. 相似文献
15.
This paper deals with the bioaccumulation of some radioactive ions from contaminated waste solutions, on hydrophytic vegetal organisms. In order to follow the distribution of radioactive ions 137Cs +, 60Co 2+ and 51Cr 3+ in various cell components extracted from Spirulina platensis, Porphiridium cruentum, Scenedesmus quadricauda, Lemna minor, Elodea canadensis, Pistia stratiotes and Riccia fluitans, the plants were cultivated in radioactive solutions. The resulting complexes were extracted with acetone or acetic acid and separated chromatographically. The results show an intense activity of the polysaccharide and lipoid fractions in the bioaccumulation process. The bioaccumulation varies in the series: Spirulina> Scenedesmus> Porphiridium> Riccia> Pistia> Lemna
3
Elodea for 137Cs + and 60Co 2+; Spirulina> Porphiridium> Scenedesmus> Riccia> Pistia> Lemna> Elodea for 51Cr 3+. 相似文献
16.
The kinetics of reactions of p-chlorobenzenediazonium ions in aqueous buffer solutions (pH 9.0–10.6) under N 2 (< 5 ppb of O 2) have been measured between 20 and 50°C. The formation of trans-diazotate is first-order with respect to the concentration of hydroxyl ions and to the equilibrium concentration of diazonium ions, if the diazonium ion? cis-diazotate equilibrium is considered as a fast prior equilibrium. This indicates that the p-chlorobenzenediazonium ion, in contrast to all previous investigations with the p-nitrobenzenediazonium ion and benzenediazonium ions carrying similar substituents with a ? M effect, rearranges from the cis- to the trans-configuration as diazohydroxide and not as diazotate. The formation of trans-diazotate is catalyzed by carbonate and inhibited by hydrogen carbonate ions; mechanisms of these catalyses are discussed, and the solvent isotope effect KH2O/ KD2O measured by an 1H-NMR. technique reported. The kinetics of the dediazoniations can be analyzed as a mixture of two reactions, a relatively fast first reaction, reaction A, which is responsible for about 5% of the total reaction, and a second reaction F. Both are first-order with respect to diazonium ion; reaction A is also first-order in hydroxyl ions. There are some indications that reaction A corresponds to the hydrolysis of the diazonium ion to give eventually amine and nitrite ions. Reaction F shows a complex dependence on hydroxyl ions; it is related to the homolytic dediazoniation. 相似文献
17.
Fluorescence correlation spectroscopy (FCS) has been extensively used to measure equilibrium binding constants ( K) or association and dissociation rates in many reversible chemical reactions across chemistry and biology. For the majority of investigated reactions, the binding constant was on the order of ∼100 M −1, with dissociation constants faster or equal to 10 3 s −1, which ensured that enough association/dissociation events occur during the typical diffusion-determined transition time of molecules through the FCS detection volume. However, complexation reactions involving metal ions and chelating ligands exhibit equilibrium constants exceeding 10 4 M −1. In the present paper, we explore the applicability of FCS for measuring reaction rates of such complexation reactions, and apply it to binding of iron, europium and uranyl ions to a fluorescent chelating ligand, calcein. For this purpose, we exploit the fact that the ligand fluorescence becomes strongly quenched after binding a metal ion, which results in strong intensity fluctuations that lead to a partial correlation decay in FCS. We also present measurements for the strongly radioactive ions of 241Am 3+, where the extreme sensitivity of FCS allows us to work with sample concentrations and volumes that exhibit close to negligible radioactivity levels. A general discussion of the applicability of FCS to the investigation of metal-ligand binding reactions concludes our paper. 相似文献
18.
以中草药有效成分 β-榄香烯为起始原料, 经烯丙位的氯代反应及亲核取代反应在 β-榄香烯母体上成功地引入含吡啶基的三齿螯合剂, 并与稳定的三羰基铼配位, 得到了一种新的铼(I)三齿配合物, 在此基础上利用铼的放射性同位素Re-188进行了放射性标记. 反应中间体及最终化合物分别用IR, 1H NMR, HRMS, HPLC或元素分析进行表征, 并对该化合物进行了初步的体外抗癌活性研究. β-榄香烯三羰基铼配合物的合成、放射化学合成及体外抗癌活性评价, 为探讨 β-榄香烯体内靶点和作用机制提供了可能, 并为最终开发基于 β-榄香烯的放射性药物奠定了基础. 相似文献
19.
Copper and zinc are essential trace elements participating in many physiological functions, notably immunity and protection
against oxidative stress. Yeasts and the yeast Saccharomyces cerevisiae, in particular, possess in their genome tandem repeats of the CUP1 gene coding for a protein (a metallothionein) capable of capturing and binding toxic elements such as copper ions. The number
of copies of this gene in a cell determines its physiological level of resistance to these ions. This paper describes the
selection, characterization, and production of a new copper-resistant yeast strain that can bind large quantities of copper
and zinc. This approach should lead to increasing the bioavailability of these trace elements and hence to reducing their
emission into the environment. 相似文献
20.
The kinetic study of the oxidation of L-α-amino- n-butyric acid by permanganate ions has been carried out in buffered acid medium at pH = 1–3, using a spectrophotometric technique. An auto-catalytic effect has been observed in all cases due to Mn 2+ ions formed as a product of the reaction. A first-order reaction with respect to the amino acid and the permanganate ions in both processes, catalyzed and uncatalyzed was obtained. The influence of several factors (pH, temperature, ionic strength, and reactants concentration) on the rate constants has also been investigated. In this article we propose a reaction mechanism in accordance with the experimental results obtained. © 1996 John Wiley & Sons, Inc. 相似文献
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