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1.
We report diffusion rates and equilibrium concentrations of water in a polyelectrolyte SPEES/PES film using ATR/FTIR spectroscopy. The data for water obtained by fitting spectral intensities to a dual mode diffusion model in the presence of different counter ions (at 0.2 mol dm−3) follow the order Li+>Cs+>Na+>Ca2+>K+. Diffusion is progressively slower for higher concentrations of NaCl (0.2-0.85 mol dm−3) and the NO3− counter anion leads to a faster diffusion rate than for Cl− at the same concentration. Both water uptake and diffusion rates are broadly consistent with expectations based on the differential degrees of swelling, caused by changes in the SO3−/SO3− interpolymer chain repulsive forces leading to a decrease in volume diffusion compared with the value for pure water. Direct spectral measurements of the degree of swelling confirm that the process does occur, although the order of the swelling amounts does not map directly onto that of the diffusion rates. This is probably because the interfacial dissociation processes are hydration dependent. 相似文献
2.
Po-Yu Chen 《Electrochimica acta》2005,50(12):2533-2540
The selective extraction of Cs+ and Sr2+ from aqueous solutions by using the ionophores calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6) and dicyclohexano-18-crown-6 (DCH18C6), respectively, was demonstrated in the hydrophobic, room-temperature ionic liquid (RTIL), tri-1-butylmethylammonium bis((trifluoromethyl)sulfonyl)imide (Tf2N−). The electrochemistry of Cs+ coordinated by BOBCalixC6 and Sr2+ coordinated by DCH18C6 was examined at a mercury film electrode (MFE) in this ionic liquid by using cyclic staircase voltammetry, sampled current voltammetry at a rotating electrode, and chronoamperometry. Both BOBCalixC6·2Cs+ and DCH18C6·Sr2+ exhibit well-defined reduction waves at approximately −2.4 and −2.9 V versus the ferrocene/ferrocenium (Fc/Fc+) couple, respectively, in which the coordinated ions are reduced to their respective amalgams, permitting the recycling of the ionophores. The diffusion coefficients of BOBCalixC6·2Cs+ and DCH18C6·Sr2+ are (2.7 ± 0.1) × 10−9 and (2.1 ± 0.1) × 10−9 cm2 s−1, respectively, at 30 °C. The coulometric efficiency for the reduction and stripping of Cs at mercury pool electrodes was about 90% and was independent of the deposition time, whereas the efficiency for Sr was slightly less than 90% at short times and decreased with the deposition time, probably due to the formation of a passive layer of Sr(Tf2N)2. 相似文献
3.
Di-urea cross-linked POE/siloxane hybrid ormolytes (di-ureasils) doped with a wide concentration range of lithium perchlorate trihydrate (LiClO4·3H2O) (200 ≥ n ≥ 0.5, where n expresses the salt content in terms of the number of ether oxygen atoms per Li+ ion) have been analysed by Fourier transform infrared and Raman (FT-IR and FT-Raman, respectively) spectroscopies and X-ray diffraction (XRD). The results obtained lead us to conclude that the xerogels with n ≥ 5 are totally amorphous. At n ≤ 1 free salt is observed. “Free” ClO4− ions appear to be the main charge carriers at the conductivity maximum located within the 25 ≤ n ≤ 8 composition range of this family of ormolytes. At n = 15 ClO4− ions coordinated in mono/tridentate (C3v symmetry) and bidentate (C2v symmetry) configurations were detected. In salt-rich samples with n < 15 there is a marked tendency for ionic association. The resulting decrease that occurs in the concentration of “free” ions is consistent with the observed significant decrease of the ionic conductivity. The analysis of the “amide I” and “amide II” regions provided solid proof that the Li+ ions bond to the urea carbonyl oxygen atoms over the entire range of salt concentration studied. 相似文献
4.
The process of size enlargement or agglomeration finds a variety of applications in material processing and utilization. Pelletization is one such process which uses water as medium and revolving units (Disc/Drums) to form spherical pellets from fine particulates. Green or wet pelletization is the first step in pelletization process and is of critical importance since the effectiveness of the subsequent stages of drying and in duration depends on the quality and quantity of green pellets.This research presents the work carried out to develop model equations to predict the size distribution of pellets at any given level of intervals. Modeling of pelletization was oriented towards predicting the size distribution of pellets at any given level of variables .The prediction of pellet size distribution involves quantification of the self preserving curve and correlation between D50 and the variables. A new model has been developed to predict the size distribution of the pellets using advanced statistical software “STATISTICA”. The equation Y = − 0.3757X2 + 1.6256X-0.74 where “Y” is the cumulative wt.% passing and “X” is D/D50 was used to predict the pellet size distribution.Correlation between D50 and variables was given by “D 50” = 4.226 + (3.106*M) − (0.544*M2) + (2.044*I) − (0.644*I2) + (0.2444*T) − (0.028*T2) − (0.058*M*I) + (0.0917*I*T) using quadratic response surface methodology. The mean pellet diameter “D50” observed versus predicted was compared. A polynomial regression equation was used to quantify the characteristic curve of iron ore slimes agglomeration process. This can be utilized to predict the complete agglomerate size distribution irrespective of the operating conditions and the size of the pelletizer if a relationship such as agglomerate median product size D50, as a function of the operating conditions is made available. 相似文献
5.
I. Katsounaros 《Electrochimica acta》2007,52(23):6412-6420
The influences of the potential, the concentration and the nature of the supporting electrolyte on the rate of the reduction of nitrate on tin were studied by both voltammetry and constant potential electrolytic experiments.Both the rate of the reduction of nitrate and the yield of nitrogen increase as the negative potential increases from −1.8 to −2.8 V versus Ag/AgCl, while the yield of nitrite decreases. The yield of ammonia displays a maximum at −2.4 V and consequently decreases.The rate of the reduction at −1.8 V versus Ag/AgCl increases significantly as the concentration of NaCl increases. The cation of the supporting electrolyte increases the rate of the reduction along the series Li+ < Na+ < K+ < Cs+. Higher rates than that of the alkalimetals have been obtained in the presence of ammonium as well as of multivalent cations such as Ca2+ and La3+. The anion of the supporting electrolyte decreases the rate of the reduction in the order I− > Br− > Cl− > F− at −1.8 V.The experimental results were qualitatively explained by the Frumkin theory and additionally by the theory of the formation of ion pairs between the cation of the supporting electrolyte and the reacting nitrate. 相似文献
6.
Theoretical insights into PF6 and its alkali metal ion pairs: geometries and vibrational frequencies
The structures, vibrational frequencies, infrared and Raman intensities of hexafluorophosphate anion (PF6−) and M+PF6− (M+ = Li+, Na+, K+, Rb+ and Cs+) ion pairs have been studied by ab initio calculations. It is shown that the tridentate coordination of cation by PF6− is the most stable structure in gas phase. The vibrational spectroscopies of the most stable geometries were calculated and the changes in band position were used to probe the ion associations. 相似文献
7.
8.
New binuclear metallic complexes of thiomacrocyclic Schiff base, 3,9,13,19 -tetraphenyl-6,16-dithione-1,11-dithio-4,5,7,8,14,15,17,18-octaazacycloeicosa-3,8,13,18-tetraene binuclear metal(II) [M(II)2-TDDOCT] (M = Cu, Co, Ni), were synthesized and their anion response characteristics were investigated. The performances of the electrodes are considerably influenced by the nature of the central metals. The Cu(II) complex-based electrode exhibited a good selectivity to salicylate anion with an anti-Hofmeister selectivity pattern: Sal− > ClO4− > SCN− > I− > Benzoate > Br− > Acetate > F− > SO32− > NO2− > Cl− > NO3− > SO42− > H2PO4−. The electrode had an excellent linear response to Sal− from 9.0 × 10− 7 to 1.0 × 10− 1 M with a slope of − 59.3 mV per decade,a detection limit of 5.0 × 10− 7 M, and a fast response time within 15 s over the entire concentration series in phosphate buffer solutions of pH 5.0 at 25 °C. Spectroscopic techniques and the influence of lipophilic charged additives on the electrode behavior were used to investigate the response mechanism to Sal−. The electrode can be applied to the direct determination of salicylate in human urine and pharmaceutical samples and the results obtained are in accord with the results from a standard method. 相似文献
9.
A. Yokozeki 《The Journal of Supercritical Fluids》2010,55(2):846-851
A family of modified van der Waals equations of state (vdW EOS) is extremely useful for many industrial applications. For example, the generic Redlich-Kwong (RK) EOS or its modification by Soave (SRK EOS) and Peng-Robinson (PR EOS) are still of popular use in industry to the present day. These two most popular (“cubic”) EOSs are based on modifications [1/(V2 + bV), or 1/(V2 + 2bV − b2)] of the volume dependence on the attractive part of the original van der Waals EOS [1/V2] and also modifications of the temperature dependence of the attractive “a(T)” parameter of the original EOS (constant a). It is extremely rare in actual EOS applications to use the volume dependence of the original van der Waals EOS. In the present phase equilibrium calculations, we employ such a generic vdW EOS, P = RT/(V − b) − a(T)/V2, with our well-tested mixing rule for multi-component mixtures. Using the same form of the “a(T)” parameter and the mixing rule, it has been found that all generic RK, PR, and vdW EOSs can present the phase behaviors (temperature-pressure-composition diagrams) equally well. It is shown that experimental gas solubility data (CO2, CF3-CFH2, SO2, and NH3) in room-temperature ionic liquids are well correlated with the present EOS model, and also that the phase behaviors such as LLE (liquid-liquid separations) are satisfactorily predicted. 相似文献
10.
The 3D mesoporous, well crystalline RuO2 film prepared via the evaporation-induced self-assembled method (EISA) successfully demonstrates the extremely high power performances (e.g., excellent capacitive behavior at 10,000 mV s−1, ultrahigh-frequency capacitive responses (the absence of a knee point in the Nyquist plot), and 2.6 MW kg−1 with an acceptable energy density of 4.6 Wh kg−1). These excellent capacitive performances were identified by means of voltammetric and electrochemical impedance spectroscopic (EIS) analyses. The mesoporous (with mean pore spacing of 18.1 nm) and crystalline nature of this film was characterized by means of the field emission scanning electron microscopy (FE-SEM), Brunaur-Emmett-Teller (BET) method, small-angle X-ray scattering (SAXRS), high-resolution transmission electron microscopy (HR-TEM), electron diffraction (ED), and X-ray diffraction (XRD) analyses. This mesoporous, well crystalline RuO2 film constrains the redox transition to the superficial region meanwhile the tailored mesoporous structure increases the electrochemically active centers, promotes the penetration of electrolytes, provides the “proton reservoirs”, and enhances the rate of electron transport simultaneously for the ultrahigh power application. The specific capacitance of this mesoporous RuO2 can be enhanced from 84 to 185 F g−1 after the microwave-assisted hydrothermal treatment. 相似文献
11.
Organic/inorganic composite membranes with different inorganic heteropolyacid (HPA) additives maintain sufficient proton conductivities for atmospheric pressure elevated temperature (>100 °C) polymer electrolyte fuel cell (PEFC) operation. However, membrane and membrane electrode assembly (MEA) processing is severely curtailed because of the solubility of the HPA additives in aqueous media. Composite membranes with the HPA (phosphotungstic acid; PTA) additive rendered insoluble by ion exchanging protons with larger cations such as Cs+, NH4+, Rb+ and Tl+ were fabricated. The additive loss in aqueous media was lowered from nearly 100% (unmodified HPA) to about 5% (modified HPA). The membranes were robust, and demonstrated low H2 crossover currents of around 2 mA/cm2 for a 28 μm thick membrane. All membranes were evaluated at high temperatures and low relative humidities in an operating fuel cell. The conductivities of the composite membranes at 120 °C and 35% relative humidity were on the order of 1.6 × 10−2 S/cm. 相似文献
12.
《Electrochimica acta》2003,48(27):4039-4048
Generation of poly(neutral red) films has been studied by means of the simultaneous measurements of current-potential and mass-potential curves during cyclic voltammetry (CV) experiments. It has been proved that the presence of molecular oxygen in the solution increases the amount of polymer deposited on the electrode. Otherwise, using the mass/charge ratio it is possible to obtain quantitative information about the electrodeposition by different procedures. It is observed that this ratio decreases when the amount of polymer electrogenerated increases, except when the polymer is not reduced and oxidised after its electrogeneration. The study of poly(neutral red) by CV and quartz crystal microbalance in solutions without monomer allows to discern between the role of different charged species which are present in the solution: salt cations (Cs+, Na+ and K+), salt anions (NO3−, Cl−, I− and Br−) and hydrated protons that can compensate electrical charge within the film during electrochemical processes. 相似文献
13.
FTIR spectroscopic investigations coupled with ionic conductivity and viscosity measurements on lithium imide (LiN(CF3SO2)2)-propylene carbonate (PC)-poly(methyl methacrylate) (PMMA) based liquid and gel electrolytes over a wide range of salt (0.025-3 M) and polymer (5-25 wt.%) concentration range furnish a novel insight into the ion-ion and ion-solvent-polymer interactions. Vibrational spectral data for LiN(CF3SO2)2-PC electrolytes reveal that the solvation of lithium ions manifests from Li+OC and Li+O (ring oxygens) interactions as the νs(CO), the ring breathing and the δ(CH) modes of the pentagonal solvent ring are strongly perturbed for all salt concentrations. The split of the ν(SO2) mode (that appears at 1355 cm−1 for the “free imide ion”) into two components at 1337 and 1359 cm−1 confirms the existence of contact ion-pairs possessing two different stable optimized geometries wherein the Li+ ion coordinates in a bidentate fashion in liquid and gel electrolytes of 3 M LiN(CF3SO2)2-PC strength. Perturbations observed for the νa(SNS) and νs(SNS) modes of the imide ion and the symmetric ring deformation mode of PC confirms the presence of ion-pairs in both 2 and 3 M electrolytes. Incorporation of even upto 25 wt.% of PMMA in a solution of LiN(CF3SO2)2-PC of 3 M strength results in an insignificant conductivity decline (as σ25>10−3 S cm−1) which is simultaneously accompanied by a massive increase in its macroscopic viscosity (as η25>108 cSt). Gels containing 25 wt.% of PMMA exhibit a complex pattern of Li+-PMMA interactions through the carbonyl oxygen of its ester group which is evidenced from the perturbations observed for the νs(CO) mode of PMMA. Ionic conductivity decline that occurs at salt concentrations ≥1.25 M LiN(CF3SO2)2-PC in both liquid and gel electrolytes, is therefore attributable to (i) ion-pairing phenomenon and (ii) an enhancement in the solution viscosity due to a high salt proportion. 相似文献
14.
Qing Lin Sheng 《Electrochimica acta》2007,52(13):4506-4512
The electrochemical properties of an electroactive rare earth metal hexacyanoferrate, neodymium hexacyanoferrate (NdHCF) were studied by mechanically attaching NdHCF samples to the surface of carbon ceramic electrodes (CCEs) derived from sol-gel technique. The resulting modified electrodes exhibit well-defined redox responses with the formal potential of 0.241 V (versus SCE) at a scan rate of 20 mV s−1 in 0.5 M KCl solution. The voltammetric characteristics of the NdHCF-modified CCEs in the presence of different alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) were investigated by voltammetry. The NdHCF-modified CCEs presented a good electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2), and was used for amperometric detection of H2O2. In addition, the NdHCF-CCEs exhibited a distinct advantage of simple preparation, surface renewal, good stability and reproducibility. 相似文献
15.
Eduardo Alejandro Ramírez Paola Andrea Jara Ulloa Luis Nuñez Vergara 《Electrochimica acta》2010,55(3):771-9713
We study the thermodynamics and kinetics of the adsorption of a redox couple having quinone nature on glassy carbon electrodes. This couple is produced by the anodic oxidation of mycotoxin ochratoxin A in 10% acetonitrile + 90% 1 M HClO4 aqueous solution. The quasi-reversible redox couple was studied by both cyclic (CV) and square wave (SWV) voltammetric techniques. The Frumkin adsorption isotherm best described the specific interaction of the redox couple with carbon electrodes. By fitting the experimental data, we obtained values of −28.4 kJ mol−1 and 0.70 ± 0.02 for the Gibbs free energy of adsorption and the interaction parameter, respectively. SWV fully characterized the thermodynamics and kinetics of the adsorbed redox couple, using a combination of the “quasi-reversible maximum” and the “splitting of SW peaks” methods. Average values of 0.609 ± 0.003 V and 0.45 ± 0.06 were obtained for the formal potential and the anodic transfer coefficient, respectively. Moreover, a formal rate constant of 10.7 s−1 was obtained. SWV was also employed to generate calibration curves. The lowest concentration of mycotoxin was 1.24 × 10−8 M (5 ppb), measured indirectly with a signal to noise ratio of 3:1. 相似文献
16.
Komol Kanta Sharker Md. Nazrul Islam Shuvo Das 《Journal of surfactants and detergents》2019,22(2):249-258
In this work, we have investigated the influence of some alkali metal ions on the Krafft temperature (TK) and critical micelle concentration (CMC) of a classical ionic surfactant, sodium dodecyl sulfate (SDS), over a wide range of temperature. The alkali metal cations such as Li+, Na+, Cs+, and K+ are found to affect the solubility and hence the TK of the surfactant. It was observed that kosmotropic Li+ lowers the TK of the surfactant. Due to the common ion effect, the solubility of SDS decreases in the presence of Na+, resulting in an increase in the TK. On the other hand, chaotropic K+ and Cs+, capable of forming contact ion pairs with the chaotropic dodecyl sulfate ion, lower the solubility and hence elevate the TK. In terms of decreasing the TK, the ions follow the trend: Li+ > Na+ > Cs+ > K+ except for 0.0025 M CsCl. The added cations screen the charge of the micelle surface and facilitate closer packing of the surfactant with a consequent decrease in the CMC. In terms of the effectiveness in lowering the CMC, the ions follow the order: Cs+ > K+ > Na+ > Li+. In the presence of added electrolytes, the γCMC values are found to be lower than the corresponding values in pure water. The thermodynamic parameters (Gibbs free energy, enthalpy, and entropy changes) of micellization were calculated to gain insights into the mechanism of the process. 相似文献
17.
C. Deslouis J. de SanoitS. Saada C. MerA. Pailleret H. Cachet P. Bergonzo 《Diamond and Related Materials》2011,20(1):1-10
Electrochemical activity, morphology and surface electrical conductivity of Boron-Doped Polycrystalline Diamond films prepared by MPCVD have been investigated. Heterogeneous apparent rate constants of three different redox systems, [Fe(CN)6]3−/4−, [IrCl6]2−/3− and [Ru(NH3)6]3+/2+ have been measured by both Cyclic Voltammetry and Electrochemical Impedance Spectroscopy on < 100 > textured films with a predominance of (111) faces: first measurements have been done with [Fe(CN)6]3−/4− only on as grown samples, and secondly after a mild electrochemical pretreatment the three redox systems have been investigated. “As-grown” samples showed a moderate average activity which was related to the presence of a minority of electronically conducting areas among insulating zones. Electrochemical treatment in neutral conditions substantially increased the activity and heterogeneous apparent rate constants kapp for the three couples were measured in the range of 10− 2 cm s− 1 with a good stability in time. Current-sensing AFM images performed ex situ showed that the electrochemically pre-treated material presented a high superficial conductivity whereas the grown sample showed major area of low conductivity. 相似文献
18.
Hong-Bo Han Shao-Wei Feng Wen-Fang Feng Jin Nie Hong Li Hajime Matsumoto Zhi-Bin Zhou 《Electrochimica acta》2010,55(23):7134-10666
New functionalized ionic liquids (ILs), comprised of multi-methoxyethyl substituted quaternary ammonium cations (i.e. [N(CH2CH2OCH3)4−n(R)n]+; n = 1, R = CH3OCH2CH2; n = 1, R = CH3, CH2CH3; n = 2, R = CH3CH2), and two representative perfluorinated sulfonimide anions (i.e. bis(fluorosulfonyl)imide (FSI−) and bis(trifluoromethanesulfonyl)imide (TFSI−)), were prepared. Their fundamental properties, including phase transition, thermal stability, viscosity, density, specific conductivity and electrochemical window, were extensively characterized. These multi-ether functionalized ionic liquids exhibit good capability of dissolving lithium salts. Their binary electrolytes containing high concentration of the corresponding lithium salt ([Li+] >1.6 mol kg−1) show Li+ ion transference number (tLi+) as high as 0.6-0.7. Their electrochemical stability allows Li deposition/stripping realized at room temperature. The desired properties of these multi-ether functionalized ionic liquids make them potential electrolytes for Li (or Li-ion) batteries. 相似文献
19.
Preparation, characterization and Methylene Blue adsorption of phosphoric acid activated carbons from globe artichoke leaves 总被引:2,自引:0,他引:2
M. BenadjemiaL. Millière L. ReinertN. Benderdouche L. Duclaux 《Fuel Processing Technology》2011,92(6):1203-1212
Activated carbons were prepared by the pyrolysis of artichoke leaves impregnated with phosphoric acid at 500 °C for different impregnation ratios: 100, 200, 300 wt.%. Materials were characterized for their surface chemistry by elemental analysis, “Boehm titrations”, point of zero charge measurements, infrared spectroscopy, as well as for their porous and morphological structure by Scanning Electron Microscopy and nitrogen adsorption at 77 K. The impregnation ratio was found to govern the porous structure of the prepared activated carbons. Low impregnation ratios (~ 100 wt.%) led to essentially microporous and acidic activated carbons whereas high impregnation ratios (> 100 wt.%) gave essentially microporous-mesoporous carbons with specific surface areas as high as 2038 m2·g− 1, pore volume as large as 2.47 cm3·g− 1, and a slightly acidic surface. The prepared activated carbons were studied for their adsorption isotherms of Methylene Blue at pH = 3 and pH = 9. The supermicroporous structure of the material produced at 200 wt.% H3PO4 ratio was found to be appropriate for an efficient adsorption of this dye controlled by dispersive and electrostatic interactions depending on the amount of oxygen at the surface. 相似文献
20.
A new diamine monomer containing noncoplanar methyl substitution, 2,2′-dimethyl-4,4′-bis(2-trifluoromethyl-4-aminophenoxy)biphenyl (DBTFAPB) was successfully synthesized and used in the preparation of a series of polyamides and polyimides by direct polycondensation with various aromatic dicarboxylic acids and tertacarboxylic dianhydrides. A new noncoplanar dicarboxylic acid monomer containing noncoplanar methyl substitution, 2,2′-dimethyl-4,4′-bis(2-trifluoromethyl-4-trimellitimidophenoxy)biphenyl (DBTFTPB) was also successfully synthesized by refluxing the diamine, DBTFAPB, with trimellitic anhydride in glacial acetic acid. A series of new poly(amide-imide)s were prepared directly from DBTFTPB with various diamines in N-methyl-2-pyrrolidinone (NMP). All the polymers exhibited excellent solubility in solvents, such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, tetrahydrofuran (THF), cyclohexanone and γ-butyrolactone at room temperature or upon heating at 70 °C. Inherent viscosities of the polymers were found to range between 0.60 and 1.34 dL g−1. Gel permeation chromatography (GPC) of the polymers showed number-average and weight-average molecular weight up to 7.3×104 and 17.9×104, respectively. These polymers showed that the glass transition temperatures were between 230 and 265 °C, and the 10% mass loss temperatures were higher than 460 °C in nitrogen atmosphere. All the polymers could be cast into flexible and tough films from DMAc solutions. They had a tensile strength in the range of 82-124 MPa and a tensile modulus in the range of 1.9-2.9 GPa. These polymers exhibited low dielectric constants ranging from 2.87 to 4.03, low moisture absorption in the range of 0.29-3.20%, and high transparency with an ultraviolet-visible absorption cut-off wavelength in the 347-414 nm range. 相似文献