首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 234 毫秒
1.
The sorption of univalent, bivalent and trivalent ions has been studied on chromium ferrocyanide gel. The studies reveal a high sorption capacity for Cs+, Tl+, Ag+, Cu2+, Zn2+, Cd2+, Fe3+ and Th4+. The sorption of monovalent cations show purely ion-exchange mechanism while the uptake of bivalent and trivalent cations is non-equivalent in nature. Single elution of Rb+, Cs+ and Tl+ has been performed from the columns of this exchanger and the recovery is almost complete in all the cases. Cu2+ and Ag+ get completely adsorbed on the gel column and their elution is not possible probably due to the formation of some new solid phases. Depending on the Kd values of the metal ions, a large number of separations of radiochemical as well as analytical importance can be performed on the columns of this exchanger material.  相似文献   

2.
A new inorganic ion-exchanger, zirconium tugnstoarsenate, has been synthesized which has been characterized by chemical analysis, thermogravimetry, X-ray and infrared spectroscopy. The ion exchanger has been found to be stable in acids and neutral salt solutions. The Kd values for 30 metal ions have been determined at pH 3–4 which show that the exchanger has high affinity for UO 2 2+ , ZrO2+, Cs+ and Tl+ ions. The variation of Kd for a number of metal ions as a function of concentration of nitric acid and ammonium nitrate has been investigated to elucidate the probable exchange mechanism and to work out conditions for elution. Some binary separations, viz. Sr2+−Cs+, Sr2+−Rb+, Sr2+−Y3+, Fe3+−Al3+, Fe3+−Zn2+ and Zn2+−Hg2+ in trace amounts have been carried out on the column of the exchanger which demonstrate the utility of the exchanger in radionalytical and analytical chemistry.  相似文献   

3.
From extraction experiments and γ-activity measurements, the extraction constants corresponding to the general equilibrium M+(aq) + 1·Cs+(nb) \rightleftarrows \rightleftarrows 1·M+(nb) + Cs+(aq) taking part in the two-phase water–nitrobenzene system (1 = hexaarylbenzene-based receptor; M+ = H3O+, NH4 +, Ag+, K+, Rb+, Tl+; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML+ complex species in nitrobenzene saturated with water were calculated; they were found to increase in the series of Rb+ < K+ < Ag+, Tl+ < H3O+, NH4 +.  相似文献   

4.
Summary Chromium antimonate has been synthesised under varying conditions of precipitation and the cation-exchange properties of the various samples are reported. Systematic study has resulted in a product suitable for column operations. The effect of equilibration time, concentration of the electrolyte, size and charge of the ion and drying temperature on exchange capacity is reported. The chemical stability and regeneration power of the sample are also investigated. The plots of log Kd against pH for Rb+, Cs+, Tl+, Ca2+, Zn2+, and Tl3+ ions suggest a predominently ion-exchange mechanism in the case of Rb+ and Cs+ ions. Kd values of 27 metal ions have been determined and some chromatographic separations of analytical and radiochemical importance based on them have been achieved on chromium antimonate columns.Presented at the Annual Convention of Chemists (India), Roorkee, December 1975.  相似文献   

5.
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq) + Cs+(org) ⟺ M+(org) + Cs+(aq) taking place in the two-phase water–phenyltrifluoromethyl sulfone (abbrev. FS 13) system (M+ = Li+, H3O+, Na+, NH4+ \hbox{NH}_{4}{}^{+} , Ag+, Tl+, K+, Rb+; aq = aqueous phase, org = FS 13 phase) were evaluated. Furthermore, the individual extraction constants of the M+ cations in the mentioned two-phase system were calculated; they were found to increase in the series of Li+ < H3O+ < Na+< NH4 + \hbox{NH}_{4}{}^{ + } < Ag+ < Tl+ < K+ < Rb+ < Cs+.  相似文献   

6.
The kinetics and mechanism of iron(II) reduction of cis- α-chloro/bromo(cetylamine)(triethylenetetramine) cobalt(III) surfactant complex ions were studied spectrophotometrically in an aqueous acid medium by following the disappearance of CoIII using an excess of the reductant under pseudo-first-order conditions: [FeII = 0.25 mol dm−3, [H+ = 0.1 mol dm−3, [μ = 1.0 mol dm−3 ionic strength in a nitrogen atmosphere at 303, 308 and 313 K. The reaction was found to be second order and showed acid independence in the range [H+ = 0.05−0.25 mol dm−3. The second order rate constant increased with CoIII concentration and the presence of aggregation of the complex itself altered the reaction rate. The effects of [FeII], [H+] and [ μ] on the rate were determined. Activation and thermodynamic parameters were computed. It is suggested that the reaction of Fe2+(aq) with CoIII complex proceeds by an inner-sphere mechanism.  相似文献   

7.
Quinolin-8-ol-bonded polyurethane foam (Ox-PUF) was synthesized by coupling the polyurethane foam matrix with oxine through an azo (-N=N-) group. The chromatographic retention behavior of Ag+, Pb2+, and Al3+ onto the Ox-PUF was studied. The extraction of Ag+, Pb2+, and Al3+ was accomplished within 15–20 min at pH ranges of 1–4, 4–6, and 6–12, respectively. The kinetics and thermodynamics of the sorption of tested metal ions onto Ox-PUF have been studied. The average values of ΔH, ΔS, ΔG; k 1, k −1, k′, and t 1/2 at 298 K were −28.7 kJ/mol, 210.1 J/(mol K), −6.74 kJ/mol, 0.095, 0.01, 0.113, and 7.184 min, respectively. The sorption capacities of the Ox-PUF were 0.16, 0.07, and 0.59 mmol/g for Ag+, Pb2+, and Al3+, correspondingly. The proposed method has been successfully applied to the preconcentration and removal of tested metal ions from wastewater. Recoveries between 80 and 99% were obtained (RSD ∼ 7). The text was submitted by the authors in English.  相似文献   

8.
Samples of zirconium antimonate have been prepared under varying conditions of precipitation. Their properties, composition, and ion-exchange behaviour are reported. The 1g Kd vs. pH curves are given for Rb+, Cs+, Zn2+, Ca2+ and Tl3+ ions. The distribution coefficients of 26 metal ions have been measured and several separations of analytical and radiochemical importance achieved.  相似文献   

9.
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the equilibrium M +(aq) + 1 · Na+ (nb) ⇄ 1 · M + (nb) + Na+ (aq) taking place in the two-phase water-nitrobenzene system (M + = Li+, H3O+, NH4 +, Ag+, K+, Rb+, Tl+, Cs+; 1 = tetraphenyl p-tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the 1 · M + complexes in water saturated nitrobenzene were calculated; they were found to increase in the order Cs+ < Rb+ < Tl+ < K+ < NH4 + < Ag+ < H3O+ < Li+. Correspondence: Emanuel Makrlík, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czech Republic.  相似文献   

10.
The complex formation between Na+, K+, Cs+, Rb+ and Tl+ metal cations with macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6) was studied in acetonitrile-water (AN-H2O) binary systems at different temperatures using conductometric method. DCH18C6 forms 1:1 complexes with these metal cations. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program Genplot. The results show that the selectivity order of DCH18C6 for the metal cations in acetonitrile-water mixtures (AN = 25.3 and 50.4 mol %) is: Tl+ > K+ > Rb+ > Cs+ > Na+. A non-linear behaviour was observed between the log K f of the complexes versus the composition of the mixed solvent which it related to changes of acidity, basicity, polarity and also polarizability of AN-H2O mixtures with the composition of this binary solution. The values of standard enthalpy changes (ΔH s0) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in the standard entropy (ΔS s0) were calculated from the relationship: ΔG s,298.150 = ΔH s0 − 298.15ΔS s0. The obtained results show that in most cases, the complexes are enthalpy stabilized but entropy destabilized. Original Russian Text ? M.H. Soorgi, G.H. Rounaghi, M.S. Kazemi, 2008, published in Zhurnal Obshchei Khimii, 2008, vol. 78, No. 10, pp. 1627–1632.  相似文献   

11.
Summary Distribution studies of some metal ions have been made on Sn(IV) and Cr(III) arsenophosphates and on some samples of Sn(II) amine hexacyanoferrates(II), using radiotracers. The Kd values of Cs+ and Rb+ have been followed at varying HNO3 concentrations also. As a result 3 useful binary separations have been achieved on Sn(IV) and Cr(III) arsenophosphates, such as Sr2+–Cs+, Hg2+–Ag+ and Hg2+–Zn2+.  相似文献   

12.
Pulse radiolysis of an aqueous solution of mono-valent thallium ion and mixed solutions of Tl+/Ag+ in the presence of various amino polycarboxylic acids such as trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (DCTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) and triethylenetetraminehexaacetic acid (TTHA) has been carried out. Abnormal valence states of Tl ions were generated. It is concluded that DCTA, DTPA, HEDTA and TTHA decrease the redox potential of Tl ions in aqueous solutions. It was observed that the electron transfer from complexed Tl2+ to Ag+ varied in the range 7.5 × 108 to 1.0 × 109, depending on the type of complexing ligand. Electron transfer from Tl2+ to Ag+ lead to the formation of silver atoms, which agglomerate further to form silver colloid.  相似文献   

13.
The complexation reactions between dibenzo-24-crown-8 (DB24C8) and K+, Rb+, Cs+ and Tl+ ions were studied conductometrically in different acetonitrile–nitromethane mixtures at various temperatures. The formation constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance–mole ratio data at different temperatures. At 25 °C and in all solvent mixtures used, the stability of the resulting complexes varied in the order Tl+ > K+ > Rb+ > Cs+. The enthalpy and entropy changes of the complexation reactions were evaluated from the temperature dependence of formation constants. It was found that the stability of the resulting complexes increased with increasing nitromethane in the solvent mixture. The TΔS° vs. ΔH° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence of enthalpy–entropy compensation in the complexation reactions.  相似文献   

14.
Zirconium arsenophosphate (ZAP) a new inorganic ion exchanger has been synthesized under varying conditions of precipitation. The material possesses good chemical and thermal stabilities and regeneration power. It shows no breakdown on irradiation with a gamma dose of ~109 rad. ZAP shows high affinity for univalent ions like Rb+, Ag+ and Tl+. The Kd-values have been determined for a number of metal ions from acid media. The stoichiometry of metal ion uptake was checked using almost carrier-free radiotracers. Sixteen binary/ternary separations of metal ions are reported on a ZAP column.  相似文献   

15.
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+ (aq) + 1·Na+ (nb) ⇔ 1·M+ (nb) + Na+ (aq) taking place in the two-phase water–nitrobenzene system (M+ = Li+, H3O+, NH4 + {\rm NH}_{4}^{ + } , Ag+, K+, Rb+, Tl+, Cs+; 1 = barium ionophore I; aq = aqueous phase, nb = nitrobenzene phase) were determined. Furthermore, the stability constants of the 1·M+ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the series of Cs+ < Rb+ < NH4 + {\rm NH}_{4}^{ + } , K+ < H3O+ < Na+ < Ag+, Tl+ < Li+.  相似文献   

16.
Solubility product (Lu(OH)3(s)⇆Lu3++3OH) and first hydrolysis (Lu3++H2O⇆Lu(OH)2++H+) constants were determined for an initial lutetium concentration range from 3.72·10−5 mol·dm−3 to 2.09·10−3 mol·dm−3. Measurements were made in 2 mol·dm−3 NaClO4 ionic strength, under CO2-free conditions and temperature was controlled at 303 K. Solubility diagrams (pLuaq vs. pC H) were determined by means of a radiochemical method using 177Lu. The pC H for the beginning of precipitation and solubility product constant were determined from these diagrams and both the first hydrolysis and solubility product constants were calculated by fitting the diagrams to the solubility equation. The pC H values of precipitation increases inversely to [Lu3+]initial and the values for the first hydrolysis and solubility product constants were log10 β* Lu,H = −7.92±0.07 and log10 K*sp,Lu(OH)3 = −23.37±0.14. Individual solubility values for pC H range between the beginning of precipitation and 8.5 were S Lu3+ = 3.5·10−7 mol·dm−3, S Lu(OH)2+ = 6.2·10−7 mol·dm−3, and then total solubility was 9.7·10−7 mol·dm−3.  相似文献   

17.
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq)+NaL+(nb)⇔ML+(nb)+Na+(aq) taking place in the two-phase water-nitrobenzene system (M+ = H+, NH4+, Ag+, Tl+; L = tetramethyl p-tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the ML+ complexes in water saturated nitrobenzene were calculated; they were found to increase in the order Tl+<NH4+<Ag+ <H+ <Na+.  相似文献   

18.
Nonempirical methods are used to calculate the geometric parameters, the frequencies of normal vibrations, and thermochemical characteristics of ions existing in saturated vapors over sodium bromide and iodide: Na2X+, NaX2, Na3X2+, and Na2X3 (X = Br, I). According to the calculations, Na2X+ and NaX2 triatomic ions have a linear equilibrium configuration of D h symmetry. Pentaatomic ions can exist in the form of three isomers: linear with D h symmetry, planar cyclic with C 2v symmetry, and bipyramidal with D 3h symmetry. At a temperature of ∼1000 K, Na3X2+ and NaX3 pentaatomic ions are shown to be present in vapor mainly in the form of linear isomers. The energies and enthalpies of ion molecular reactions with the participation of the above ions are calculated, and the formation enthalpies of the ions are determined, Δ f H o(0 K): 293±2 kJ/mol (Na2Br+), 354±2 kJ/mol (Na2I+), −536±2 kJ/mol (NaBr2, −458±2 kJ/mol (NaI2, 24±5 kJ/mol (Na3Br2+, 143±5 kJ/mol (Na3I2+, −810±5 kJ/mol (Na2Br3, and −675±5 kJ/mol (Na2I3.  相似文献   

19.
The reductions of [Co(CN)5NO2]3−, [Co(NH3)5NO2]2+ and [Co(NH3)5ONO]2+, by TiIII in aqueous acidic solution have been studied spectrophotometrically. Kinetic studies were carried out using conventional techniques at an ionic strength of 1.0 mol dm−3 (LiCl/HCl) at 25.0 ± 0.1 °C and acid concentrations between 0.015 and 0.100 mol dm−3. The second-order rate constant is inverse—acid dependent and is described by the limiting rate law:- k2 ≈ k0 + k[H+]−1,where k=k′Ka and Ka is the hydrolytic equilibrium constant for [Ti(H2O)6]3+. Values of k0 obtained for [Co(CN)5NO2]3−, [Co(NH3)5NO2]2+ and [Co(NH3)5ONO]2+ are (1.31 ± 0.05) × 10−2 dm3 mol−1 s−1, (4.53 ± 0.08) × 10−2 dm3 mol−1 s−1 and (1.7 ± 0.08) × 10−2 dm3 mol−1 s−1 respectively, while the corresponding k′ values from reductions by TiOH2+ are 10.27 ± 0.45 dm3 mol−1 s−1, 14.99 ± 0.70 dm3 mol−1 s−1 and 17.93 ± 0.78 dm3 mol−1 s−1 respectively. Values of K a obtained for the three complexes lie in the range (1–2) × 10−3 mol dm−3 which suggest an outer-sphere mechanism.  相似文献   

20.
The complexation reaction of phenylaza-15-crwon-5, 4- nitrobenzo- 15-crown-5, and benzo-15-crown-5 with Ag+, Tl+ and Pb2+ ions in methanol solution have been studied by a competitive potentiometric method. The Ag+/Ag electrode used both as an indicator and reference electrode in a concentration cell. The emf of cell monitored as the crown ethers concentration varies through the titration. The stoichiometry and stability constants of resulting complexes have been evaluated by MINIQUAD. The stoichiometry for all resulting complexes was 1:1. The stability of these metal ions with derivatives of 15-crown-5 are in order phenylaza-15-crown-5 > Benzo-15-crown-5 > 4-nitrobenzo-15-crown-5, and for the each used crown ethers are as Pb2+ > Ag+ > Tl+. The effect of the substituted group on the stability of resulting complexes was considered. The obtained results are novel and interesting.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号