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1.
Jianjun Liu Yanliang Wang Deqian Li 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(10):949-955
BACKGROUND: Thermodynamic studies on Ce(IV) extraction with primary amine N1923 demonstrate that primary amine N1923 is an excellent extractant for separation of Ce(IV) from Re(III). In order to clarify the mechanism of extraction and to optimize the parameters in practical extraction systems used in the rare earth industry, the extraction kinetics was investigated using a constant interfacial area cell with laminar flow in the present work. RESULTS: The data indicate that the rate constant (kao) becomes constant when stirring speed exceeds 250 rpm. The apparent forward extraction rate is calculated to be 10?1.70. The activation energy (Ea) was calculated to be 20.5 kJ/mol from the slope of log kao against 1000/T. The minimum bulk concentration of the extractant necessary to saturate the interface (Cmin) is lower than 10?5 mol L?1. CONCLUSION: Studies of interfacial tension and the effects of stirring rate and specific interfacial area on the extraction rate show that the extraction rate is kinetically controlled, and a mass transfer model has been proposed. The rate equation has been obtained as: ? d[Ce(IV)]/dt = 10?1.70[Ce(IV)] [(RNH3)2SO4]1.376. The rate‐controlling step has been evaluated from analysis of the experimental results. Copyright © 2007 Society of Chemical Industry 相似文献
2.
Studies on extraction equilibrium constants at different temperatures and thermodynamic parameters of solvent extraction of Pb2+ ion with carboxylic acid derivatives of different ring size calixarenes and structure related monomeric compound have been carried out. The extraction equilibrium constants corresponding to calix[n]arene (n?=?4, 5, 6) derivatives decrease in the order [5]arene > [6]arene > [4]arene. In all cases, the complexation process is primarily enthalpy driven. The favorable enthalpic contribution for extraction of Pb2+ is in the order hexamer ≈ monomer > tetramer > pentamer. However, the unfavorable entropic loss follows the order: monomer > hexamer > tetramer > pentamer. Overall stability of the host-guest complex is the function of entropy-enthalpy compensation and the free energy of complexation is minimum for the pentamer, followed by tetramer ≈ hexamer and monomer. Although the carboxylic acid derivative of calix[4]arene is more preorganized than the calix[5]arene derivative, extraction of Pb2+ ion with the tetramer passes through greater entropic loss than that with the pentamer and the degree of preorganization of calix[4]arene derivative is far from perfect for the complexation and extraction of Pb2+ ion. As compared to tetrameric and hexameric counterparts, the structural features of the carboxylic acid derivative of calix[5]arene prior to complexation contribute much to interact with the Pb2+ ion and form a thermodynamically stable complex. Supplementary materials are available for this article. Go to the publisher's online edition of Solvent Extraction and Ion Exchange to view the supplemental file. 相似文献
3.
Abstract The kinetics of the forward and backward extraction of the title process have been investigated using a Lewis cell operated at 3 Hz and flux or (F) – method of data treatment. The dependences of (F) in the forward extraction on [Fe3+], [H2A2](o), pH, and [HSO4 ?] are 1, 0.5, 1, and ?1, respectively. The value of the forward extraction rate constant (k f ) has been estimated to be 10?7.37 kmol3/2 m?7/2 s?1. The analysis of the experimentally found flux equation gives the following simple equation: F f =100.13 [FeHSO4 2+] [A?], on considering the monomeric model of BTMPPA and the stability constants of Fe(III)‐HSO4 ? complexes. This indicates the following elementary reaction occurring in the aqueous film of the interface as rate determining: [FeHSO4]2++A?→[FeHSO4.A]+. The very high activation energy of 91 kJ mol?1 supports this chemical reaction step as rate-determining. The negative value of the entropy change of activation (?94 J mol?1 K?1) indicates that the slow chemical reaction step occurs via the SN2 mechanism. The backward extraction rate can be expressed by the equation: F b =10?5.13 [[FeHSO4A2]](o) [H+] [H2A2](o) ?0.5. An analysis of this equation leads to the following chemical reaction step as rate-determining: [FeHSO4A2](int)→[FeHSO4A]+A(i) ?. However, the activation energy of 24 kJ mol?1 suggests that the backward extraction process is intermediate controlled with greater contribution of the diffusion of one or the other species as a slow process. The equilibrium constant obtained from the rate study matches well with that obtained from the equilibrium study. 相似文献
4.
5.
《分离科学与技术》2012,47(17):2395-2402
Abstract The selective liquid-liquid extraction of Fe3+ cation from the aqueous phase to the organic phase was carried out by using p-tert-butylcalix[4]arene [L1], ca-lix[4]arene [L2], p-nitro-calix[4]arene [L3], calix[4]arene p-sulfonic acid [L4], p-(diethylamino)methylcalixt4]arene [L5], tetramethyl-p-tert-butylcalix[4]arene tet-raketone [L6], 25,27-dimethyl-26,28-dihydroxy-p-tert-butylcalix[4]arene diketone [L7], calix[4]arene-bearing dioxime group on the lower rim [L8], and a monooxime [L9]. The effect of varying pH upon the extraction ability of calixarenes substituted with electron-donating and electron-withdrawing groups at their p-position was examined. Observed results were compared with those found for unsubstituted calix[4]arene. 相似文献
6.
Qing-Xiang Li Qiao Li Rong Chen Xiang-Liang Yang Jing-Yan Zhou Hui-Bi Xu 《Inorganic chemistry communications》2010,13(11):1293-1295
A novel tetranuclear copper(II) complex Na2[Cu4Na2(TACNTA)4(H2O)6]·(H2O)26, where TACNTA is 1,4,7-triazacyclononane-1,4,7-triacetate, was synthesized and characterized by X-ray crystallography. The result shows that each copper(II) ion is six-coordinated to three nitrogen atoms and three oxygen atoms of ligand TACNTA and adopts distorted octahedral coordination geometry. The superoxide (·O2?) dismutation activity of the complex was also investigated by the riboflavin–methionine–nitro blue tetrazolium assay. 相似文献
7.
Naglaa E El‐Hefny Sahar I El‐Dessouky 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(3):394-400
The liquid–liquid extraction of Gd(III) from aqueous nitrate medium was studied using di‐2‐ethylhexylphosphoric acid (HDEHP) in kerosene. On the basis of the slope analysis data, the composition of the extracted species was found to be [Gd A3(HA)] with the extraction equilibrium constant (Kex) = (1.48 ± 0.042) × 10?12 mol dm?3. The results of the effect of temperature on the value of the equilibrium extraction constant indicated the endothermic character of the extraction system. The kinetics of the forward extraction of Gd3+ from nitrate medium by HDEHP in kerosene was investigated using the single drop column technique. The rate of flux (mass transfer per unit area) was found to be proportional to [Gd(III)], [H2A2](o), [NO3?], and [H+]?1 in the liquid drop organic phase. The forward extraction rate constant, kf, was 2.24 × 10?3 m s?1 using the equation: Copyright © 2005 Society of Chemical Industry 相似文献
8.
Maria Atanassova Nikolay Vassilev Emil Tashev Victoria Lachkova Sabi Varbanov 《分离科学与技术》2016,51(1):49-56
The solvent extraction of trivalent lanthanoids (Ln3+) by 5,11,17,23-tetra(para-tert-octyl)-25,26,27,28-tetrakis(dimethylphosphinoylmethoxy)calix[4]arene (S), bearing four phosphine oxide donor groups at the lower rim as synergistic agent in combination with a 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP) in CHCl3 from chloride medium at µ = 0.1 was quantitatively described in the form of LnP3·S complexes. The role of the synergistic agent on the extraction process was discussed. The values of the separation factors have been evaluated. On the basis of the IR and NMR spectra the stoichiometry and the structure of the solid mixed complex of Eu(III) with HP and S were proposed. 相似文献
9.
Maryam Ghoreishi Amiri Ali Morsali Fahime Bigdeli 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(1):195-200
A new 1D supramolecular involving two different ligands, {[Zn(GB)2]·(μ-bpe)3}
n
(ClO4)2n
·nH2O (GB = 2-guanidinobenzimidazole and bpe = 1,2-bis(4-pyridyl)ethylene, has been synthesised, characterized by elemental analysis,
IR-, 1H NMR-, 13C NMR spectroscopy. The thermal stability of compound {[Zn(GB)2]·(μ-bpe)3}
n
(ClO4)2n
·nH2O was studied by thermal gravimetric and differential thermal analyses. The single crystal X-ray analysis shows that the complex
is a one-dimensional polymer involving macrocycle rings as a result of non-covalent bridging bpe ligands via N–H···N and N···N
interactions, N–H···bpe···bpe···H–N, with the basic repeating {[Zn(GB)2](μ-bpe)3}(ClO4)2·H2O units and by connecting [Zn(GB)2]2+ nodes. ZnO nanoparticles were obtained by calcination of compound {[Zn(GB)2]·(μ-bpe)3}
n
(ClO4)2n
·nH2O at 500 °C in air. The nanoparticles were characterized by X-ray diffraction and scanning electron microscopy. 相似文献
10.
Van der Sluis et al.'s model was used to determine the rate of the partial dissolution of a Tunisian phosphate rock with dilute phosphoric acid (1.5 mass% P2O5). When the temperature rises from 25 to 90°C, for a given particle size, the mass-transfer coefficients, kL°, vary from 3 × 10?3 to 8 × 10?3 m ·s?1. The corresponding diffusion coefficients, D, lies between 6 × 10?7 and 27 × 10?7 m2·s?1. Activation energy is equal to 14 kJ·mol?1 and values of kL°, at 25°C, are in the range of 0.28 × 10?3 and 4 × 10?3 m·s?1 when the agitation speed goes from 220 to 1030 rpm, showing that the leaching process is controlled by diffusion rather than by chemical reaction. 相似文献
11.
12.
Charge transfer complexes possessing a … DADA … structure with both the donor, D, and acceptor, A, being S = 1/2 radicals may exhibit cooperative magnetic phenomena. The complex [Fe(C5Me5)2]+·[TCNQ]−· exhibits metamagnetic behavior. The similarly structured [TCNE]−· and [C4(CN)6]−· complexes are ferromagnets, whereas the [DDQ]−· salt is a paramagnet. The high temperature magnetic susceptibility obeys the Curie-Weiss expression with θ = + 30, + 30, and + 3 for the [TCNE]−·, [C4(CN)6]−·, and [TCNQ]−· salts, respectively. The ferromagnetic [TCNE]−· salt exhibits zero field Zeeman split 57Fe Mossbauer spectra with an internal field of 425.6 kOe at 4.23 K. After reviewing the current papers discussing ferromagnetism in molecular (organic) compounds, a qualitative model consistent with the necessary bulk spin alignment required for a ferromagnet is presented. 相似文献
13.
A compound, [Mn5(H4C8A)(OH)2(C3H6NO2)(DMF)5(CH3O)1.5(HCO2) (C2H3O2)0.5]·2DMF·CH3OH (1) (H8C8A = p-tert-butylcalix[8]arene, DMF = N,N′-dimethylformamide), was synthesized by the solvothermal method in the mixed CH3OH/DMF (1:1) solvent. Compound 1 is featured with a tetragonal pyramid-like MnII5 cluster encircled within a calix[8]arene molecule with a ‘pleated loop’ conformation. Magnetic study indicates that the MnII centers exhibit antiferromagnetic interactions. 相似文献
14.
MING CHEN HUI-LAN WANG JING GU GUO-WANG DIAO 《Journal of Applied Electrochemistry》2007,37(3):331-337
The water-soluble p-sulfonated sodium salt of calix[8]arene (III) was synthesized. The product was characterized by FT-IR, NMR and UV–Vis spectra.Then
the electrochemical behaviors of p-sulfonated sodium salt of calix[8]arene in NaAc+HAc (pH = 4) buffer solution was studied. In aqueous solution, p-sulfonated calix[8]arene can be oxidized when the potential is more than 0.7 V vs SCE. It was confirmed that the reaction
was a two-electron irreversible electrochemical reaction. The transfer coefficient, α, was measured as 0.7. At 25°, the diffusion
coefficient of p-sulfonated calix[8]arene was determined as 8.6 × 10−7 cm2 s−1. The diffusion activation energy of p-sulfonated calix[8]arene was 18.9 kJ mol−1 at pH = 4. 相似文献
15.
By using a semi-rigid tripodal ligand 1,1′,1′′-(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)tripyridinium-4-olate) (L), six isomorphous lanthanum metal-organic frameworks (MOFs), namely, [Pr(L)2(Cl)2]·(Cl)(DMF)0.5·(H2O)·(1), [Nd(L)2(Cl)2]·(Cl)(2), [Tb(L)2(Cl)2]·(Cl)·(DMF)·(H2O)(3), [Eu(L)2(Cl)2]·(Cl)(DMF)·(H2O)(4), [La(L)2(Cl)2]·(Cl)(5), [Sm(L)2(Cl)2]·(Cl) (DMF)·(H2O) (6), were obtained and characterized by single crystal X-ray diffraction, IR and elemental analysis. Six compounds are isostructural with Ln3 + (Ln = Pr, Nd, Tb, Eu, La, Sm) and in which the Ln3 + is considered as a 6-connecting node and the L ligand is a 3-connecting node to afford a (3,6)-connected 2D layer with kgd topology, which further stacks into 3D supramolecular networks through C-H…O weak interactions. Luminescent properties of these lanthanide MOFs have also been assessed at ambient temperature, in which the Pr3 +-1 and the La3 +-5 are slightly blue-shifted with respect to the ligand. Series of sharp peaks characteristic of the Eu3 +-4, the Tb3 +-3 and Sm3 + − 6 metal-centered luminescence appear. The Nd3 +-2 has no emission. 相似文献
16.
Safaa Eldin H. Etaiw Tarek A. Fayed Mohamed B. El-zaria Safaa N. Abdou 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(1):36-42
Self assembly of K3[Cu(CN)4] with Me3SnCl and quinoxaline (qox) affords the new organotin ternary adduct ∞3[Cu2(CN)3·Me3Sn·qox], 1, as orange platelet crystals. The supramolecular architecture of 1 consists of [Cu2(CN)3]− building blocks connected by the (Me3Sn)+ cations forming infinite corrugated 1D-chains. The chains are bridged by the qox molecules forming 2D-layers containing fused
distorted polygons. The layers are interwoven forming 3D-network structure, which are stabilized by close packing effects
such as H-bonds as well as Cu···Cu and π–π interactions. IR and mass spectra as well as TGA are investigated. 相似文献
17.
《分离科学与技术》2012,47(14):2151-2157
Several commercial calix-crown-6 ligands such as: calix[4]arene-bis-crown-6 (CC), calix[4]arene-bis-benzo-crown-6 (CBC), calix[4]arene-bis-naphtho-crown-6 (CNC), and bis-(octyloxy)calix[4]arene-mono-crown-6 (CMC) have been evaluated for their Cs uptake ability from nitric acid feed solutions in a novel solvent system. The calix-crown-6 ligands were made soluble in phenyl trifluoromethyl sulphone (PTMS) and 1 × 10?3 M solutions were used for metal ion extraction from nitric acid feed solutions. The extraction efficiency of the calix-crown-6 ligands was found out to be: CBC > CNC > CMC ? CC, which was attributed to trends of their partition coefficients. CNC was considered to be the most suitable extractant in view of its better organophilicity. The effects of concentrations of nitric acid and Cs carrier in feed were also investigated. Studies carried out using variation of ligand concentration yielded an extracted species of the type [CsL+][NO3?]org. Stripping of Cs(I) from the loaded organic phase was found to be possible when the organic phase contained minute quantities of Alamine 336. Co-current extraction and stripping studies were also carried out using CNC as the extractant. 相似文献
18.
Copolyethers and polyurethanes containing lower and upper rim calix[4]arene units in the fixed cone conformation were prepared in good yield by polycondensation reactions of distal calix[4]arene diols with bisphenol-A/dibromomethane and 2,4-tolylendiisocyanate (TDI), respectively. In a similar way were prepared calix[4]arene-crown-5 and -crown-6 polyurethanes in the fixed 1,3-alternate conformation by condensation of TDI with lower rim calixcrown-5 and calixcrown-6 diols. However, the poor solubility in common organic solvents of the copolyether derivatives (Mw=11,100-11,600 g/mol) hampered further studies on their ionophoric properties. Aiming to obtain model compounds for the investigation of both extraction abilities and ionophoric properties of the polyurethane materials, several bis-urethanes were also synthesized by reaction of the calix[4]arene diols with p-tolylisocyanate (TI). The extraction ability measurements of monomeric and polymeric calix[4]arene urethanes (Mw=12,300-83,500 g/mol) towards alkali metal cations (Li+, Na+, K+, Rb+, Cs+) and Ag+showed a remarkable efficiency and selectivity of calixcrown-6 polyurethane toward Rb+, Cs+and Ag+. 相似文献
19.
《Inorganic chemistry communications》2000,3(2):49-51
Reaction of Mo2Cl4(dppm)2 with excess [n-Bu4N][CN] produces [Bu4N]2[Mo2II,II(CN)6(dppm)2]·2(CH3CN)·2(C6H6) (1) the first example of an edge-sharing bioctahedral compound of Mo(II), that upon exposure to air oxidizes to the mixed valence analog [Bu4N][Mo2II,III(CN)6(dppm)2]·2(H2O)·2(CH3CN) (2). 相似文献
20.
Zhou Zhi-Hua Ruan Jian-Ming Zhou Zhong-Cheng Zou Jian-Peng 《Polymer-Plastics Technology and Engineering》2013,52(9):863-871
The influence of non-isothermal melt crystallization on thermal behavior and isothermal melt crystallization kinetics of poly-L-lactide (PLLA) were investigated by differential scanning calorimetry (DSC), polarizing micrograph (POM) and x-ray diffraction (XRD). Crystallization performed at lower cooling rates (2°C·min?1) is accompanied by a variation of the kinetics around 118°C. The glass transition temperature of PLLA decreases with increase of cooling rate, and the crystallinity at the end of crystallization increases with decreasing cooling rate. The size of PLLA spherulites increases with a decrease in the cooling rate, and PLLA becomes almost amorphous cooled at rapid rate (>10°C·min?1). PLLA exhibits an Avrami crystallization exponent n = 3.01±0.13 in isothermal crystallization in the range from 90°C to 140°C. According to Hoffman-Lauritzen theory, two crystallization regime are identified with a transition temperature occurring at 118°C, and the value of Kg(II)/Kg(III) is 2.17 [Kg(II) = 6.025 × 105K2, Kg(III) = 1.307 × 106 K2]. 相似文献