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Kanji Miyabe - One of the best experts on this subject based on the ideXlab platform.
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estimation of Molecular Diffusivity in aqueous solution of acetonitrile by the wilke chang equation
2011Co-Authors: Kanji MiyabeAbstract:It was tried to estimate the Molecular Diffusivity (Dm) of solutes in the mixtures of acetonitrile (ACN) and water by the Wilke–Chang equation. Although the information about association coefficient (α) is necessary for the calculation, it has never been proposed for ACN. The value of α was estimated as 1.37 from Dm of benzene in ACN at 303 K experimentally measured by the peak parking method. The values of α, i.e. 2.6, 1.9, 1.5, and 1.0, which have respectively been proposed for four solvents, i.e. water, methanol, ethanol, and benzene, were correlated with two physico-chemical parameters of the solvents, i.e. solubility parameter and ET value. The α value for ACN was plotted around the two correlations, indicating its appropriateness. The values of Dm calculated by the Wilke–Chang equation using the α value for ACN were compared with those measured by the peak parking method and the Aris–Taylor method in aqueous solutions of ACN. The mean square deviation of the estimation of Dm was calculated as 8.8 and 14%. It was demonstrated that the Wilke–Chang equation can be used for estimating Dm with a reasonable accuracy in the mixtures consisting of ACN and water.
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estimation of Molecular Diffusivity in liquid phase systems by the wilke chang equation
2011Co-Authors: Kanji Miyabe, Ryo IsogaiAbstract:This study deals with the application of the Wilke-Chang equation to the estimation of Molecular Diffusivity (Dm) in liquid phase systems including polar solutes and/or solvents. First, Dm of benzene in six different organic solvents was experimentally measured by the peak parking method. The value of association coefficient (α) was calculated from the Dm values by assuming that Dm can be represented by the Wilke-Chang equation. Then, the α value was correlated with the solubility parameter (δ) and ET of the solvents. Two different curved correlations were observed between α and the two physico-chemical parameters. This means that α of given solutes and solvents can be obtained from the values of δ and/or ET. Finally, Dm was estimated by a modified Wilke-Chang equation, which is derived by considering the aggregation of not only solvent molecules but also solute molecules. Although α is necessary for the estimation, it was calculated from δ for various solutes and solvents. The Dm values estimated were compared with those reported in literature. The mean square deviation between the Dm values was calculated less than 19% for 71 Dm data. It was demonstrated that the modified Wilke-Chang equation can be used for estimating Dm in liquid phase systems containing polar solutes and solvents.
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peak parking moment analysis a strategy for the measurement of Molecular Diffusivity in liquid phase
2010Co-Authors: Kanji Miyabe, Junichi Nagai, Georges GuiochonAbstract:The peak-parking (PP) method permits the measurement of Molecular diffusivities (Dm) in solutions. Dm is first measured for benzene in pure methanol and acetonitrile (ACN), using an empty open tube. This yields an effective axial diffusion coefficient (Dax,m) equal to Dm because there is no tortuosity nor constriction in the flow channel. The same measurements made for the same combinations of solute and solvents, using a column packed with non-porous silica particles provides the obstructive factor (Ym), defined as the ratio Dax,m/Dm, which accounts for the influence of tortuosity and constriction of the interparticulate space in packed columns on axial Molecular dispersion. The value obtained for Ym, 0.74–0.75, is constant, irrespective of the solvent. Then, PP experiments were made with the same apparatus and column to measure Dm for benzene, toluene, and ethylbenzene in aqueous solutions of methanol and ACN. The values of Dm obtained by correcting the experimental Dax,m values with Ym were compared with values previously reported and those estimated by several literature correlations. They were in good agreement with each other. The average relative error is estimated at 4.5–10%, demonstrating that the PP method is practically effective for experimental measurements of Dm.
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peak parking method for measurement of Molecular Diffusivity in liquid phase systems
2009Co-Authors: Kanji Miyabe, Nobuho Ando, Georges GuiochonAbstract:Abstract The combination of series of measurements of band broadening made with the peak parking (PP) method, using successively an open capillary tube and a HPLC column, gives a convenient procedure for the measurement of the Molecular Diffusivity (Dm) of compounds in solutions, of their axial dispersion coefficient (Dax,m) in chromatographic columns, and of the tortuosity or obstructive factor of the column bed. The Molecular Diffusivity measured for benzene in methanol was in excellent agreement with literature data. The ratio of the axial dispersion coefficient to this Diffusivity gives the obstructive factor (γm) of the packed bed, which was 0.74 for the column used. The values of Dm in other solutions were obtained from the Dax,m values measured by the PP method, by correcting the Dax,m values with the γm value. The Dm values determined by this method were in good agreement with those previously reported or estimated using literature correlations. These results showed that the PP method is effective for the experimental measurement of Dm.
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a kinetic parameter concerning mass transfer in silica monolithic and particulate stationary phases measured by the peak parking and slow elution methods
2006Co-Authors: Kanji Miyabe, Hiroshi Kobayashi, Daisuke Tokuda, Nobuo TanakaAbstract:Mass transfer in monolithic C18-silica stationary phases and C18-silica gel particles was studied. A traditional kinetic parameter, gamma(s)D(s), which is a diffusion coefficient of solute molecules in the stationary phase, was measured by two unusual approaches, i.e., peak-parking and slow-elution methods. The correlation between the ratio of gamma(s)D(s) to Molecular Diffusivity (Dm) and the retention factor (k) was represented by one common curve, irrespective of the RPLC conditions. A similar curved profile was also observed between another kinetic parameter (D(Ls)), which is related to the axial diffusive Molecular migration in the stationary phase, and the retention equilibrium constant (Ka). The values of D(Ls) and Ka were calculated from those of gamma(s)D(s) and k, respectively. The ratio of D(Ls)/Dm increases with decreasing Ka and seems to approach around unity when Ka is infinitely small. The dependence of D(Ls) on Ka was also studied from extra-thermodynamic points of view. The linear correlation between In D(Ls) and In Ka suggests the existence of a kind of linear free energy relationship between the mass transfer in the stationary phase and the retention equilibrium. Because these characteristics of D(Ls) are similar to those of the surface diffusion coefficient (D(sur)), D(Ls) seems to correspond to D(sur).
Rebecca M Dickhut - One of the best experts on this subject based on the ideXlab platform.
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Molecular Diffusivity of polycyclic aromatic hydrocarbons in aqueous solution
1994Co-Authors: Kurt E Gustafson, Rebecca M DickhutAbstract:Knowledge of Molecular diffusion is fundamental for describing processes that control the environmental fate and distribution of contaminants such as polycyclic aromatic hydrocarbons (PAHs). Measured Molecular diffusion coefficients of several polycyclic aromatic hydrocarbons (PAHs) in aqueous solution indicate that available techniques largely overestimate the diffusivities of compounds with three or more aromatic rings. The Molecular diffusivities of benzene, toluene, naphthalene, phenanthrene, anthracene, benz[a]anthracene, and pyrene were measured in water at temperatures ranging from 4 to 40 C using a modified open tube elution method. An experiment was conducted to assess the effects and interactions of solute concentration, temperature, and salinity on PAH aqueous Molecular Diffusivity. Aqueous diffusion coefficients increased with temperature and decreased with molar volume of the diffusing species. No significant effects of solute concentration (12.5--50% saturation) and salinity (0--35 ppt) were observed. The experimental data have been used to formulate a new predictive equation for estimation of aqueous Molecular Diffusivity of aromatic chemicals as a function of temperature.
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Molecular Diffusivity of polycyclic aromatic hydrocarbons in air
1994Co-Authors: Kurt E Gustafson, Rebecca M DickhutAbstract:Molecular diffusivities in air are essential for the accurate determination of chemical fluxes across the air-water interface. Gas-phase diffusion coefficients are also important parameters for describing the dispersion of contaminants in unsaturated soils. The Molecular diffusivities of benzene, toluene, naphthalene, acenaphthylene, phenanthrene, anthracene, benz[a]anthracene, pyrene, and benzo[e]pyrene were measured in air at temperatures ranging from [minus]5 to +40 C using a modified arrested flow method. Molecular diffusivities in air for all compounds studied decreased with Molecular size, and increased logarithmically with temperature. The experimental data have been used to formulate a predictive equation for the estimation of Molecular diffusivities of aromatic chemicals in air as a function of temperature and molar volume.
Georges Guiochon - One of the best experts on this subject based on the ideXlab platform.
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peak parking moment analysis a strategy for the measurement of Molecular Diffusivity in liquid phase
2010Co-Authors: Kanji Miyabe, Junichi Nagai, Georges GuiochonAbstract:The peak-parking (PP) method permits the measurement of Molecular diffusivities (Dm) in solutions. Dm is first measured for benzene in pure methanol and acetonitrile (ACN), using an empty open tube. This yields an effective axial diffusion coefficient (Dax,m) equal to Dm because there is no tortuosity nor constriction in the flow channel. The same measurements made for the same combinations of solute and solvents, using a column packed with non-porous silica particles provides the obstructive factor (Ym), defined as the ratio Dax,m/Dm, which accounts for the influence of tortuosity and constriction of the interparticulate space in packed columns on axial Molecular dispersion. The value obtained for Ym, 0.74–0.75, is constant, irrespective of the solvent. Then, PP experiments were made with the same apparatus and column to measure Dm for benzene, toluene, and ethylbenzene in aqueous solutions of methanol and ACN. The values of Dm obtained by correcting the experimental Dax,m values with Ym were compared with values previously reported and those estimated by several literature correlations. They were in good agreement with each other. The average relative error is estimated at 4.5–10%, demonstrating that the PP method is practically effective for experimental measurements of Dm.
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peak parking method for measurement of Molecular Diffusivity in liquid phase systems
2009Co-Authors: Kanji Miyabe, Nobuho Ando, Georges GuiochonAbstract:Abstract The combination of series of measurements of band broadening made with the peak parking (PP) method, using successively an open capillary tube and a HPLC column, gives a convenient procedure for the measurement of the Molecular Diffusivity (Dm) of compounds in solutions, of their axial dispersion coefficient (Dax,m) in chromatographic columns, and of the tortuosity or obstructive factor of the column bed. The Molecular Diffusivity measured for benzene in methanol was in excellent agreement with literature data. The ratio of the axial dispersion coefficient to this Diffusivity gives the obstructive factor (γm) of the packed bed, which was 0.74 for the column used. The values of Dm in other solutions were obtained from the Dax,m values measured by the PP method, by correcting the Dax,m values with the γm value. The Dm values determined by this method were in good agreement with those previously reported or estimated using literature correlations. These results showed that the PP method is effective for the experimental measurement of Dm.
V Linek - One of the best experts on this subject based on the ideXlab platform.
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mechanism of gas absorption enhancement in presence of fine solid particles in mechanically agitated gas liquid dispersion effect of Molecular Diffusivity
2008Co-Authors: V Linek, M Kordac, M SoniAbstract:Abstract The effect of fine particle addition in physical gas desorption and absorption with fast reaction (sulphite oxidation in the presence of a cobalt catalyst) has been studied in a stirred cell with a flat gas–liquid interface and mechanically agitated gas–liquid bubble dispersion in a wide range of stirring speeds. Activated carbon and TiO 2 were used at low loadings ( 0.5 – 1 kg m - 3 ) . The desorption was used to avoid supersaturation effect which was observed during oxygen and hydrogen absorption into liquid saturated with nitrogen. Using two gases with sufficiently different Diffusivity (O 2 , H 2 ), the effect of Molecular Diffusivity on the mass transfer coefficient was estimated in the form k L ∼ D n , with the exponent n indicating the surface mobility accompanying the effect of the particles. The value n = 2 / 3 indicates a fully rigid and the value 1 / 2 a fully mobile mass transfer interface. Chemisorption experiments confirmed that the particles do not affect mass transfer area of the agitated dispersion. After addition of particles, k L for physical desorption from bubbles in dispersion was increased by 10–30% in water and by 20–60% in sulphate solution with decreasing agitation rate. In the stirred cell, the increases were much higher reaching 200% and 230% for water and sulphate solution, respectively. The exponent n exhibited a significant decrease in the presence of particles ranging from 10% (for dispersion in water) to 33% (for stirred cell in sulphate solution). The decrease in n encountered in dispersion indicated the transition from a partially mobile to a fully mobile surface. The reduction of k L was interpreted through the physicochemical effect of surfactants removal from the gas–liquid interface by activated carbon particles. The results have confirmed that the mechanism of mass transfer enhancement in the presence of fine particles, based on the removal of surface contaminants from the liquid by adsorption onto the hydrophobic surface of the particles, as suggested by Kaya and Schumpe [2005. Surfactant adsorption rather than “shuttle effect”? Chemical Engineering Science 60, 6504–6510] for stirred cell, is valid also for the enhancement of absorption rate from bubbles in mechanically agitated dispersion.
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mechanism of enhanced gas absorption in presence of fine solid particles effect of Molecular Diffusivity on mass transfer coefficient in stirred cell
2006Co-Authors: M Kordac, V LinekAbstract:Abstract Desorption of oxygen and hydrogen from various liquids (water, 0.8 molar sodium sulphate solution) containing suspended particles of activated carbon at various solid loading was investigated. The desorption was used to avoid supersaturation effect which was observed during oxygen and hydrogen absorption into liquid saturated with nitrogen. Experiments were carried out in a stirred cell with flat gas–liquid interface at 30 ∘ C and atmospheric pressure. An increase of k L upon addition of the particles was observed. Enhancement factor increases with increasing contact time of the particles with liquid reaching maximum steady-state value of approx. 3 after sufficiently long time (a few hours) regardless of solid loading ( 0.1 – 1 kg / m 3 ) , agitator frequency ( 50 – 300 min - 1 ) and solute gas ( O 2 , H 2 ) . The results fit the correlation k L = C e 1 / 4 D n ( e is specific power dissipated by agitator in liquid and D is Molecular Diffusivity of gas absorbed) with the exponent n = 2 3 for liquids without and n = 1 2 for the liquids with the particles. It indicates that the interface is rigid in absence of particles and hinders the motion of liquid along the interface forming boundary layer while in the presence of particles the interface is completely mobile and surface renewal proceeds according to the penetration model. These results confirm a finding of Kaya and Schumpe (2005) that the enhancement of mass transfer in the cell at the presence of hydrophobic solids is due to clean-up of the interface from surfactants by their adsorption on hydrophobic solids rather than by a “shuttle mechanism” exerted by particles with a high adsorption capacity for the transfer component.
Kurt E Gustafson - One of the best experts on this subject based on the ideXlab platform.
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Molecular Diffusivity of polycyclic aromatic hydrocarbons in aqueous solution
1994Co-Authors: Kurt E Gustafson, Rebecca M DickhutAbstract:Knowledge of Molecular diffusion is fundamental for describing processes that control the environmental fate and distribution of contaminants such as polycyclic aromatic hydrocarbons (PAHs). Measured Molecular diffusion coefficients of several polycyclic aromatic hydrocarbons (PAHs) in aqueous solution indicate that available techniques largely overestimate the diffusivities of compounds with three or more aromatic rings. The Molecular diffusivities of benzene, toluene, naphthalene, phenanthrene, anthracene, benz[a]anthracene, and pyrene were measured in water at temperatures ranging from 4 to 40 C using a modified open tube elution method. An experiment was conducted to assess the effects and interactions of solute concentration, temperature, and salinity on PAH aqueous Molecular Diffusivity. Aqueous diffusion coefficients increased with temperature and decreased with molar volume of the diffusing species. No significant effects of solute concentration (12.5--50% saturation) and salinity (0--35 ppt) were observed. The experimental data have been used to formulate a new predictive equation for estimation of aqueous Molecular Diffusivity of aromatic chemicals as a function of temperature.
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Molecular Diffusivity of polycyclic aromatic hydrocarbons in air
1994Co-Authors: Kurt E Gustafson, Rebecca M DickhutAbstract:Molecular diffusivities in air are essential for the accurate determination of chemical fluxes across the air-water interface. Gas-phase diffusion coefficients are also important parameters for describing the dispersion of contaminants in unsaturated soils. The Molecular diffusivities of benzene, toluene, naphthalene, acenaphthylene, phenanthrene, anthracene, benz[a]anthracene, pyrene, and benzo[e]pyrene were measured in air at temperatures ranging from [minus]5 to +40 C using a modified arrested flow method. Molecular diffusivities in air for all compounds studied decreased with Molecular size, and increased logarithmically with temperature. The experimental data have been used to formulate a predictive equation for the estimation of Molecular diffusivities of aromatic chemicals in air as a function of temperature and molar volume.