Showing papers on "Standard molar entropy published in 2012"

Density, Surface Tension, and Refractive Index of Ionic Liquids Homologue of 1-Alkyl-3-methylimidazolium Tetrafluoroborate [Cnmim][BF4] (n = 2,3,4,5,6)

Abstract: The values of density, surface tension, and refractive index were measured for a classic series of air and water stable ionic liquids (ILs) based on tetrafluoroborate, [Cnmim][BF4](n = 2,3,4,5,6)(1-alkyl-3-methylimidazolium tetrafluoroborate) in the temperature range of (298.15 to 338.15 ± 0.02) K. In terms of Glasser’s theory, the standard molar entropy and lattice energy of the ILs were calculated. Using Kabo’s method, the molar enthalpy of vaporization of the IL, ΔlgHm0 (298 K), was estimated. According to the interstice model, the thermal expansion coefficient of ILs [Cnmim][BF4] (n = 2,3,4,5,6), α, were calculated, and in comparison with experimental value, their magnitude order is in good agreement. To test this new concept of ionic parachor, [BF4]− was chosen as a reference ion and its individual value of ionic parachor was determined in terms of extrathermodynamic assumption. Then, using ionic parachor of [BF4]−, the ionic parachors for all corresponding imidazolium cations, [Cnmim]+, were calcula...

Effect of Alkyl Chain Length in Anions on Thermodynamic and Surface Properties of 1-Butyl-3-methylimidazolium Carboxylate Ionic Liquids

Abstract: Carboxylate-anion-based imidazolium ionic liquids (ILs) are powerful solvents for cellulose and lignin. However, little is known about their fundamental physicochemical properties. In this work, 1-butyl-3-methylimidazolium carboxylate ILs 1-butyl-3-methylimidazolium formate ([C4mim][HCOO]), acetate ([C4mim][CH3COO]), propionate ([C4mim][CH3CH2COO]), and butyrate ([C4mim][CH3(CH2)2COO]), in which the alkyl chain length in the anions is being varied in contrast to the more usual studies where alkyl chain length in the cations is varied, have been synthesized and their densities and surface tensions have been determined experimentally at different temperatures. By using these data, the molar volume, isobaric expansivity, standard entropy, lattice energy, surface excess entropy, vaporization enthalpy, and Hildebrand solubility parameter have been estimated for these ILs. From the analysis of structure–property relationship, the effect of alkyl chain length in the anions on these physicochemical properties of ...

Electrochemical removal of boron from water: Adsorption and thermodynamic studies

Abstract: The present work provides an electrochemical removal of boron from water and its kinetics, thermodynamics, isotherm using mild steel and stainless steel as anode and cathode respectively. The various operating parameters on the removal efficiency of boron were investigated, such as initial boron ion concentration, initial pH, current density and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2 A dm−2 at pH of 7.0. First-, second-order rate equations, Elovich and Intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Fe(OH)3 were determined and correlated with isotherm equations such as Langmuir, Freundlich and D-R models. Thermodynamic parameters, such as standard Gibb's free energy (ΔG°), standard enthalpy (ΔH°) and standard entropy (ΔS°), were also evaluated by Van't Hoff equation. The adsorption process follows second-order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules. The adsorption of boron onto Fe(OH)3 was found to be spontaneous and endothermic. © 2011 Canadian Society for Chemical Engineering

Kinetic and Equilibrium Profiles of Adsorptive Recovery of Thorium(IV) from Aqueous Solutions Using Poly(methacrylic acid) Grafted Cellulose/Bentonite Superabsorbent Composite

Abstract: The removal and recovery of thorium(IV) [Th(IV)] ions from aqueous solutions were investigated using poly(methacrylic acid)-grafted-cellulose/bentonite (PMAA-g-Cell/Bent) superabsorbent composite through batch adsorption experiments. Surface characterizations of the adsorbent were investigated. The adsorbent showed significant Th(IV) removal (>99.7%) at pH 5.0. The influence of coexisting ions on the adsorption of Th(IV) was studied. Mass transfer aspects of Th(IV) adsorption onto PMAA-g-Cell/Bent were evaluated. The Sips adsorption isotherm described the adsorption data very well, with a maximum adsorption capacity of 188.1 mg/g. Thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°), standard free energy (ΔG°), activation energy (Ea), isosteric enthalpy (ΔHx), and entropy (ΔSx) were calculated. Tests with a seawater sample revealed the effectiveness of PMAA-g-Cell/Bent for adsorptive removal of Th(IV) from aqueous solutions. Desorption experiments showed that 0.1 M HNO3 can eff...

Adsorption equilibrium, thermodynamics, kinetics, mechanism and process design of zinc(II) ions onto cashew nut shell

Abstract: Cashew nut shell (CNS) is an agricultural waste was investigated as a new adsorbent for the removal of zinc(II) from aqueous environment. Effects of solution pH, CNS dose, contact time, initial zinc(II) concentration and temperature on removal efficiency were tested and optimum conditions were evaluated. The equilibrium data were fitted well with Langmuir isotherm model and pseudo-second-order kinetic model. Langmuir monolayer adsorption capacity of CNS was examined as 24.98 mg/g. Changes in standard Gibbs free energy (▵G°), standard enthalpy (▵H°) and standard entropy (▵S°) showed that the sorption of zinc(II) ions onto CNS are spontaneous and exothermic at 303–333 K. Sorption process was found to be controlled by both surface and pore diffusion. A batch adsorber was designed for different CNS dose to effluent volume ratios using Langmuir equation. Effective diffusivity values were found to be 1.927 × 10−11 (10 mg/L), 2.135 × 10−11 (20 mg/L), 2.267 × 10−11 (30 mg/L), 2.305 × 10−11 (40 mg/L) and 2.362 × 10−11 (50 mg/L) m2/s. © 2011 Canadian Society for Chemical Engineering

Electrochemical Removal of Boron fromWater: Adsorption and Thermodynamic Studies

Abstract: The present work provides an electrochemical removal of boron from water and its kinetics, thermodynamics, isotherm using mild steel and stainless steel as anode and cathode respectively. The various operating parameters on the removal efficiency of boron were investigated, such as initial boron ion concentration, initial pH, current density and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2 A dm−2 at pH of 7.0. First-, second-order rate equations, Elovich and Intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Fe(OH)3 were determined and correlated with isotherm equations such as Langmuir, Freundlich and D-R models. Thermodynamic parameters, such as standard Gibb’s free energy (G◦), standard enthalpy (H◦) and standard entropy (S◦), were also evaluated by Van’t Hoff equation. The adsorption process follows second-order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules. The adsorption of boron onto Fe(OH)3 was found to be spontaneous and endothermic

Study on Thermodynamic Properties of Ionic Liquid N-Butyl-3-methylpyridinium Bis(trifluoromethylsulfonyl)imide

Abstract: An air- and water-stable hydrophobic ionic liquid N-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide ([c43mpy][NTf2]) was synthesized and characterized. Density, surface tension, dynamic viscosity, and electrical conductivity of the IL were measured and calculated from (278.15 to 353.15) K. The glass transition temperature and decomposition temperature were determined by the differential scanning calorimetry and thermogravimatric analysis. The physicochemical properties like molecular volume, standard molar entropy, lattice energy, parachor, molar enthalpy of vaporization, interstice volume, thermal expansion coefficient, interstice fraction, etc. of the IL were estimated by the reported empirical and semiempirical equations. The dynamic viscosity and electrical conductivity data of the IL were described by Vogel–Fulcher–Tamman and Arrhenius equations, respectively. Then, the relationship between the molar conductivity and dynamic viscosity of this IL was expressed through the Walden rule.

n-Hexadecane hydrocracking Single-Event MicroKinetics on Pt/H-beta

Abstract: The Single-Event MicroKinetic (SEMK) model constructed for gas-phase hydroconversion of light n -alkanes on large-pore USY zeolites was applied, for the first time, to the hydrocracking of n -hexadecane on a Pt/H-Beta catalyst. Despite the 12-ringed pore channels, shape selectivity was observed in the formation of ethyl side chains. Additionally, heavy feed molecules such as n -hexadecane lead to physisorption saturation of the catalyst pores by strong Van der Waals interactions of the long alkyl chains with the zeolite framework. Intermolecular interactions and packing efficiencies in the pores induce deviations from typical Henry-regime physisorption characteristics as the physisorption selectivity, which is expected to increase with increasing carbon number, appeared to be independent of the latter. Micropore saturation effects were described by the ‘size entropy’ which quantifies the difference in standard entropy loss between physisorption in the Henry regime and hindered physisorption on a saturated surface. The size entropy is proportional to the catalyst loading with physisorbed species and the adsorbate carbon number. The addition of a size entropy term in the SEMK model, amounting to 102 J mol −1 K −1 for a hexadecane molecule at full saturation, allowed accurately reproducing the contribution of secondary isomerization and cracking reactions, as quantified by means of a contribution analysis.

Isothermal Titration Calorimetry in Supramolecular Chemistry

Abstract: Among the many options to measure molecular interactions in solution, isothermal titration microcalorimetry (ITC) stands out as an almost universal, label-free, operationally fast, fully computer-operated, and thus quite robust method to acquire all thermodynamic parameters necessary to characterize the energetics of intermolecular association. Provided that there is an enthalpic response accompanying the mutual molecular interaction, the free energy, molar enthalpy, and, by using the Gibbs–Helmholtz equation, also the molar entropy can be determined in a single run. The present review describes the fundamental concept, the methodological aspects concerning the range accessible to direct determinations, and its potential expansion. Special focus is on data evaluation and the intrinsic limits to translate the macroscopic instrumental output into the illumination of the microscopic events happening on the molecular scene. The scope of ITC as a means to characterize thermodynamic equilibria is illustrated with the help from recent applications spanning from low-molecular host–guest chemistry to multimeric assembly of surfactants observable as phase changes. Keywords: ITC; molecular interaction; host–guest chemistry; thermodynamics; calorimetry; association; supramolecular chemistry; enthalpy; entropy

Adsorption of 2, 4-dichlorophenoxyacetic acid onto date seeds activated carbon: equilibrium, kinetic and thermodynamic studies

Abstract: Adsorption isotherm and kinetics of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide on activated carbon prepared from Barhi date seeds were determined from batch tests. The effects of contact time, initial herbicide concentration and solution temperature were investigated. The adsorption equilibrium data were processed in accordance with the three most widely used adsorption isotherms: Langmuir, Freundlich and Temkin isotherm models. The equilibrium data were best represented by Langmuir isotherm model, showing maximum monolayer adsorption capacity of 175.4 mg/g. The kinetic data were also examined with the pseudo-first-order and pseudo-second-order models, and was found to follow closely the pseudo-second-order kinetic model. Thermodynamic parameters such as standard enthalpy (ΔH o ), standard entropy (ΔS o ) and standard free energy (ΔG o ) were evaluated. The adsorption interaction was found to be endothermic in nature.

Almandine: Lattice and non-lattice heat capacity behavior and standard thermodynamic properties

Abstract: The heat capacity of three synthetic polycrystalline almandine garnets (ideal formula Fe3Al2Si3O12) and one natural almandine-rich single crystal was measured. The samples were characterized by optical microscopy, electron microprobe analysis, X-ray powder diffraction, and Mossbauer spectroscopy. Measurements were performed in the temperature range 3 to 300 K using relaxation calorimetry and between 282 and 764 K using DSC methods. All garnets show a prominent λ-type heat-capacity anomaly at low temperatures resulting from a paramagnetic-antiferromagnetic phase transition. For two Fe3+-free or nearly Fe3+-free synthetic almandines, the phase transition is sharp and occurs at 9.2 K. Almandine samples that have ~3% Fe3+ show a λ-type peak that is less sharp and that occurs at 8.0 ± 0.2 K. The low- T C P data were adjusted slightly using the DSC results to improve the experimental accuracy. Integration of the low- T C P data yields calorimetric standard entropy, S∘ , values between 336.7 ± 0.8 and 337.8 ± 0.8 J/(mol·K). The smaller value is recommended as the best S∘ for end-member stoichiometric almandine, because it derives from the “best” Fe3+-free synthetic sample. The lattice (vibrational) heat capacity of almandine was calculated using the single-parameter phonon dispersion model of Komada and Westrum (1997), which allows the non-lattice heat capacity ( C ex) behavior to be modeled. An analysis shows the presence of an electronic heat-capacity contribution ( C el, Schottky anomaly) superimposed on a larger magnetic heat-capacity effect ( C mag) around 17 K. The calculated lattice entropy at 298.15 K is S vib = 303.3 J/(mol·K) and it contributes about 90% to the total standard entropy at 298 K. The non-lattice entropy is S ex = 33.4 J/(mol·K) and consists of S mag = 32.1 J/(mol·K) and S el = 1.3 J/(mol·K) contributions. The C P behavior for almandine above 298 K is given by the polynomial [in J/(mol·K)]: C P = 649.06 ( ± 4 ) - 3837.57 ( ± 122 ) · T - 0.5 - 1.44682 ( ± 0.06 ) · 10 7 · T - 2 + 1.94834 ( ± 0.09 ) · 10 9 · T - 3 which is calculated using the measured DSC data together with one published heat-content datum determined by transposed-drop calorimetry along with a new determination in this work that gives H 1181K − H 302K = 415.0 ± 3.2 kJ/mol. Using our S∘ value and the C P polynomial for almandine, we derived the enthalpy of formation, Δ H °f, from an analysis of experimental phase equilibrium results on the reactions almandine + 3rutile = 3ilmenite + sillimanite + 2quartz and 2ilmenite = 2Fe + 2rutile + O2. A Δ H °f = −5269.63 kJ/mol was obtained.

Standard entropy, surface excess entropy, surface enthalpy, molar enthalpy of vaporization, and critical temperature of bis(trifluoromethanesulfonyl)imide-based ionic liquids

Abstract: The density and surface tension of several bis(trifluoromethanesulfonyl)imide-based ionic liquids (ILs) 1-methyl-3-pentylimidazolium bis(trifluoromethanesulfonyl)imide ([MPI][TFSI]), 1,2-dimethyl-3-pentylimidazolium bis(trifluoromethanesulfonyl)imide ([DMPI][TFSI]), 1-ethyl-3-pentylimidazolium bis(trifluoromethanesulfonyl)imide ([EPeI][TFSI]), and 1-ethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide ([EPrI][TFSI]) were measured at temperatures from 293.15 to 353.15 K and atmospheric pressure. The values of thermal expansion coefficient and surface excess entropy were estimated by extrapolation. In terms of Glasser's semiempirical relation of ILs, the standard molar entropy and the lattice energy of ILs were estimated. Using Kabo's and Sugden's methods, the molar enthalpy values of vaporization of the IL, Δ 1 g H m ° ( 298 K ) , and Parachor were estimated. The thermal expansion coefficients of the bis(trifluoromethanesulfonyl)imide-based hydrophobic ILs were estimated by the interstice model and they are in good agreement with experimental values. This indicated that the interstice model is reasonable and may be applied to estimate the coefficient of thermal expansion of ionic liquids.

Equilibrium modeling and thermodynamic parameters for adsorption of cationic dyes onto Yemen natural clay

Abstract: The equilibrium modeling for adsorption of cationic dye Methylene Blue (MB) onto Yemen natural clay at different temperatures, particle size and solution pH was studied. The adsorption capacity was found to be increase with increasing temperature and pH and decreased with increasing particle size. The maximum adsorption capacity was 500.0 (mg g−1) at T = 25°C, dp = 250−355 μm and pH = 12. The data are successfully tested by Langmuir, Freundlich, Temkin and Redlich–Peterson models. It was found that the Redlich–Peterson isotherm best fit the experimental data over the whole concentration range. Thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were calculated. The thermodynamic parameters of methylene blue/clay system indicated spontaneous and endothermic nature of the adsorption process. The results demonstrate that Yemen natural clay is very effective in the removal of MB from aqueous solution and can be used as alternative of ...

Density, Electrical Conductivity, and Dynamic Viscosity of N-Alkyl-4-methylpyridinium Bis(trifluoromethylsulfonyl)imide

Abstract: Two air and water stable hydrophobic ionic liquids N-alkyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([Cn4mpy][NTf2], n = 2, 4) were synthesized and characterized. The density, electrical conductivity, and dynamic viscosity were measured and estimated in the range of T = (278.15 to 363.15) K. The melting temperature, glass transition temperature, and decomposition temperature of the two ILs were determined according to the differential scanning calorimetry (DSC) and thermogravimetric analyzer (TG). The molecular volume, standard molar entropy, and lattice energy were estimated in terms of empirical equations on the basis of the density values. The electrical conductivity and dynamic viscosity values dependence on temperature were fitted by the Vogel–Fulcher–Tamman equation. The molar conductivity was calculated by the density and electrical conductivity.

Isothermal Titration Calorimetry in Supramolecular Chemistry

Abstract: Among the many options to measure molecular interactions in solution, isothermal titration microcalorimetry (ITC) stands out as an almost universal, label-free, operationally fast, fully computer-operated, and thus quite robust method to acquire all thermodynamic parameters necessary to characterize the energetics of intermolecular association. Provided that there is an enthalpic response accompanying the mutual molecular interaction, the free energy, molar enthalpy, and, by using the Gibbs–Helmholtz equation, also the molar entropy can be determined in a single run. The present review describes the fundamental concept, the methodological aspects concerning the range accessible to direct determinations, and its potential expansion. Special focus is on data evaluation and the intrinsic limits to translate the macroscopic instrumental output into the illumination of the microscopic events happening on the molecular scene. The scope of ITC as a means to characterize thermodynamic equilibria is illustrated with the help from recent applications spanning from low-molecular host–guest chemistry to multimeric assembly of surfactants observable as phase changes. Keywords: ITC; molecular interaction; host–guest chemistry; thermodynamics; calorimetry; association; supramolecular chemistry; enthalpy; entropy

Energetic study applied to the knowledge of the structural and electronic properties of monofluorobenzonitriles.

Abstract: The present work reports an energetic and structural study of 2-fluoro-, 3-fluoro-, and 4-fluorobenzonitrile. The standard molar enthalpies of formation, in the condensed phase, of the three isomers were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K. The standard molar enthalpies of vaporization or sublimation (for 4-fluorobenzonitrile), at T = 298.15 K, were measured using high-temperature Calvet microcalorimetry. The combination of these two parameters yields the standard molar enthalpies of formation in the gaseous phase. The vapor-pressure study of the referred compounds was performed by a static method, and the enthalpies of phase transition derived from the application of the Clarke and Glew equation. Theoretically estimated gas-phase enthalpies of formation, basicities, proton and electron affinities, and adiabatic ionization enthalpies were calculated from the G3MP2B3 level of theory. In order to evaluate the electronic properties, the geometries were reoptimiz...

Interfacial composition, thermodynamic properties, and structural parameters of water-in-oil microemulsions stabilized by 1-pentanol and mixed surfactants.

Abstract: The present study is focused on the evaluation of the interfacial composition, thermodynamic properties, and structural parameters of water-in-oil mixed surfactant microemulsions [(cetylpyridinium chloride, CPC+polyoxyethylene (20) cetyl ether, Brij-58 or polyoxyethylene (20) stearyl ether, Brij-78)/1-pentanol/n-heptane, or n-decane] under various physicochemical environments by the Schulman method of cosurfactant titration of the oil/water interface. The estimation of the number of moles of 1-pentanol at the interface (n(a)(i)) and bulk oil (n(a)(o)) and its distribution between these two domains at the threshold level of stability have been emphasized. The thermodynamics of transfer of 1-pentanol from the continuous oil phase to the interface have been evaluated. n(a)(i),n(a)(i), standard Gibbs free energy (ΔG(t)(0)), standard enthalpy (ΔH(t)(0)), and standard entropy (ΔG(t)(0)) of transfer process have been found to be dependent on the molar ratio of water to surfactant (ω), type of nonionic surfactant and its content (X(Brij-58 or Brij-78)), oil and temperature. A correlation between (ΔH(t)(0)) and (ΔS(t)(0)) is examined at different experimental temperatures. Bulk surfactant composition dependent temperature insensitive microemulsions have been reported. Associated structural parameters, such as droplet dimensions and aggregation number of surfactant and cosurfactant at the droplet interface have been evaluated using a mathematical model after suitable modifications for mixed surfactant systems. In light of these parameters, the prospect of using these microemulsion systems for the synthesis of nanoparticles and the modulation of enzyme activity has been discussed. Correlations of the results in terms of the evaluated physicochemical parameters have been attempted.

Standard Gibbs Energies of Formation of the Ferro- and Paramagnetic Phases of AlNd3

Abstract: The standard Gibbs energies of formation, ΔfGm,T°, below and above the critical temperatures of polymorphs, magnetic, and superconductive phase transitions are necessary to clarify the driving forces for such phase transitions. However, they have remained unsolved due to experimental difficulties. In the present study, the ΔfGm,T° values of the ferro- and paramagnetic phases of AlNd3 were directly determined. The standard entropy of formation, ΔfSm,T°, was determined from the heat capacity, Cp,m°, from 2 to 300 K. The standard enthalpies of formation, ΔfHm,T°, were determined by combining Cp,m° with the standard enthalpy of formation at 298 K, ΔfHm,298°, obtained by acid-solution calorimetry. The magnetization, M, was measured by a magnetic balance. The ΔfGm,T° values obtained by combining the ΔfSm,T° and ΔfHm,T° values indicate that the phase transition occurs at 73.47 K, i.e., the Curie point, consistent with the spontaneous magnetization from para- to ferromagnetic phases clarified by measuring M. The ...

Crystal structure, thermodynamic properties, and paragenesis of bukovskyite, Fe-2(AsO4)(SO4)(OH)center dot 9H(2)O

Abstract: Bukovskyite is a relatively rare secondary ferric arsenate-sulfate. At the type locality near the municipality of Kutna Hora (Czech Republic), it is the main secondary mineral in the medieval dumps, where it occurs in enormous amounts and forms nodules of prodigious dimensions. We investigated the mineral bukovskyite and the type locality in detail to understand the abundance of the mineral at this locality. The crystal structure of bukovskyite was solved for bukovskyite crystals from Grossvoigtsberg (Germany) and found to be of the space group P (I) over bar with a final R factor of 5.08% from 2403 reflections. The lattice parameters at room temperature are a = 7.549(1) angstrom, b = 10.305(1) angstrom, c = 10.914(2) angstrom, alpha = 115.136(3)degrees, beta = 99.798(3)degrees, and gamma = 92.864(3)degrees. The structure consists of octahedral-tetrahedral Fe-arsenate chains. Sulfate tetrahedra are bonded to the chains and free H2O molecules via a complicated network of hydrogen bonds. Calorimetric measurements (acid-solution calorimetry at T = 298.15 K and relaxation calorimetry yielded heat capacities from T = 0.4 K to 300 K) gave an enthalpy of formation of -4742.4 +/- 3.8 kJ.mol(-1) and standard entropy of 615.2 +/- 6.9 J.mol(-l).K-1. A combination of these values gives a Gibbs free energy of formation of -3968.9 +/- 4.3 kJ.mol(-1) and aqueous solubility product (log K) of -30.627. Bukovskyite is metastable with respect to scorodite; if scorodite is not considered in the thermodynamic calculations, a stability field of bukovskyite appears at low pH and high sulfate and arsenate activity. Field observations showed that bukovskyite occurs in dumps where the space between the rock fragments is filled by clays. Bukovskyite crystallizes from Fe-As-S-rich gels that replace Si-Al gels. The exact mechanisms that control the entire process are not clear but will be the subject of further studies.

Surfactant assisted preparation and characterization of carboxymethyl cellulose Sn(IV) phosphate composite nano-rod like cation exchanger

Abstract: Carboxymethyl cellulose Sn(IV) phosphate composite nano-rod like cation exchanger with diameter in the range of 20–40 nm, length in the range of 100–150 μm and particle size in the range of 21–38 nm have been successfully prepared by surfactant assisted sol–gel method. Scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, fourier transform infra red spectroscopy and thermogravimetric analysis-differential thermal analysis studies were carried out to study the structure and morphology of this composite nano-rod like cation exchanger. Freundlich adsorption isotherm is well fitted for the adsorption of pyridine on the surface of this composite nano-rod like cation exchanger. The thermodynamic parameters such as Freundlich constant, thermodynamic equilibrium constant (K0), standard free energy changes (ΔG0), standard enthalpy changes (ΔH0) and standard entropy changes (ΔS0) have been evaluated. These parameters indicated that the adsorption of pyridine on the surface of composite nano-rod like cation exchanger was feasible, spontaneous and exothermic in nature which suggests for the potential application of pyridine removal from water.

Density and Surface Tension of Ionic Liquids [H2N–C2mim][PF6] and [H2N–C3mim][PF6]

Abstract: Two amino functionalized ionic liquids 1-(2-aminoethyl)-3-methylimidazolium hexafluorophosphate, [H2N–C2mim][PF6], and 1-(3-aminopropyl)-3-methylimidazolium hexafluorophosphate, [H2N–C3mim][PF6], were synthesized and characterized. The density and surface tension of these ionic liquids were measured from (293.15 to 343.15) K. Their values decreased with increasing temperature. The physical properties such as coefficient of thermal expansion, molecular volume, standard molar entropy, lattice energy, and molar enthalpy of vaporization were estimated using experimental data. The critical temperature of the ionic liquids was estimated using Eotvos equations. The values were then used to estimate the boiling temperature of the ionic liquids according to methods of Rebelo. The interstice model was used to predict the thermal expansion coefficient of the ionic liquids, α, and the result was in very good agreement with the experimental value. In addition, the parachor method was used to predict the physical prope...