The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Georges Guiochon - One of the best experts on this subject based on the ideXlab platform.
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investigations on the calculation of the third moments of elution peaks ii linear flow speed dependence of External Mass Transfer coefficient
Journal of Chromatography A, 2013Co-Authors: Hong Gao, Fabrice Gritti, Georges GuiochonAbstract:This work is a systematic investigation of the linear velocity dependence of the External Mass Transfer coefficient provided by fitting experimental results to the solution of the GR (General Rate) model that was previously derived. The second and third statistical moments of eluted peaks were measured at different flow rates, under different experimental conditions and analyzed. The results of this analysis confirm the validity of this dependence under our current experimental conditions. The other Mass Transfer parameters provided by the GR model were determined. The variations of these parameters with the experimental conditions were measured. The results are discussed and interpreted.
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investigations on the calculation of the third moments of elution peaks i composite signals generated by adding up a mathematical function and experimental noise
Journal of Chromatography A, 2012Co-Authors: Hong Gao, Paul G Stevenson, Fabrice Gritti, Georges GuiochonAbstract:Elution peaks were generated by summing up a mathematical function and a previously recorded experimental noise. The first three statistical moments of these peaks were calculated using several data processing methods. The results obtained were analyzed. From this analysis, a method is developed for the calculation with a satisfying accuracy of the third moments of these combined signals. The method is applicable to real chromatographic peaks and makes it possible to determine accurate estimates of their third moments. This approach could be helpful for the investigation of the Mass Transfer processes in chromatographic columns because the third moment provides direct access to the External Mass Transfer coefficient.
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External Mass Transfer in silica monolithic stationary phases
Chemical Engineering Science, 2010Co-Authors: Kanji Miyabe, Nobuho Ando, Takuya Nakamura, Georges GuiochonAbstract:Abstract A detailed analysis of a procedure of measurement of the External Mass Transfer coefficients ( k f ) in RPLC systems is provided. Application is described for a system consisting of a C 18 -silica monolithic column and a methanol/water eluent (70/30, v/v). The k f values of butylbenzene at 298 K were derived from peak profiles recorded in pulse response experiments by subtracting the contributions of the kinetic processes, i.e., axial molecular diffusion, eddy diffusion, pore and surface diffusion, from the band variance. This approach provided the Sherwood number ( Sh ) for a range of Reynolds number ( Re ) between 0.002 and 0.005 and a Schmidt number ( Sc ) equal to 2.7×10 3 . The experimental values of k f were compared with those estimated from literature correlations, giving a relative error of ca. 11% when Pfeffer equation was used for estimating k f . The exponents obtained for Re and Sc in Sh were 0.43 and 0.39, values comparable with those found in literature correlations, i.e., 0.33. The k f values estimated using the reference correlations are of the same order of magnitude as the experimental k f values. The acquisition of more experimental data is needed for deriving an improved correlation affording more accurate estimates of k f in stationary phases of cylindrical shape, like silica monoliths.
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kinetic study on External Mass Transfer in high performance liquid chromatography system
Journal of Chromatography A, 2010Co-Authors: Kanji Miyabe, Yuuki Kawaguchi, Georges GuiochonAbstract:Abstract External Mass Transfer coefficients ( k f ) were measured for a column packed with fully porous C 18 -silica spherical particles (50.6 μm in diameter), eluted with a methanol/water mixture (70/30, v/v). The pulse response and the peak-parking methods were used. Profiles of elution peaks of alkylbenzene homologues were recorded at flow rates between 0.2 and 2.0 mL min −1 . Peak-parking experiments were conducted under the same conditions, to measure intraparticle and pore diffusivity, and surface diffusion coefficients. Finally, the values of k f for these compounds at 298 K were derived from the first and second moments of the elution peaks by subtracting the contribution of intraparticle diffusion to band broadening. As a result, the Sherwood number ( Sh ) was measured under such conditions that the Reynolds ( Re ) and the Schmidt numbers ( Sc ) varied from 0.004 to 0.05 and from 1.8 × 10 3 to 2.7 × 10 3 , respectively. We found that Sh is proportional to Re α and Sc β and that the correlation between these three nondimensional parameters is almost the same as those given by conventional literature equations. The values of α and β were close to those in the literature correlations, between 0.26 and 0.41 and between 0.31 and 0.36, respectively. The use of the Wilson–Geankoplis equation to estimate k f values entails a relative error of ca. 15%. So, conventional literature correlations provide correct estimates of k f in HPLC systems, even for particle sizes of the order of a micrometer.
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External Mass Transfer in high performance liquid chromatography systems
Journal of Chromatography A, 2008Co-Authors: Kanji Miyabe, Motoki Ando, Nobuho Ando, Georges GuiochonAbstract:External Mass Transfer in a HPLC system operated in the reversed-phase mode was studied by pulse response experiments, using a column packed with non-porous C(18)-silica gel spherical particles, 18 microm in diameter. The first and second moments of the elution peaks, measured under different flow velocities and temperatures, were analyzed by the moment method to determine the External Mass Transfer coefficient (k(f)). The dependence of the Sherwood number on the Reynolds and the Schmidt numbers is almost the same as that observed in previous investigations of conventional literature correlations. The exponent of the last two nondimensional parameters was derived as being in the range from 0.28 to 0.41. When the Kataoka equation is used, the mean square deviation was calculated to be 0.21 for the values of k(f) estimated in this study. It is concluded that conventional correlations can be used to estimate k(f) values, even when the particle diameter is of the order of a micrometer.
Y Mansouri - One of the best experts on this subject based on the ideXlab platform.
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biosorption of cd2 from aqueous solution by a naoh treated bacterial dead streptomyces rimosus bioMass
Hydrometallurgy, 2004Co-Authors: A. Selatnia, M.z. Bakhti, A Madani, L Kertous, Y MansouriAbstract:The cadmium biosorption capacity of a Streptomyces rimosus bioMass treated with NaOH (0.1 M) was studied in the batch mode. After pretreatment of bioMass at the ambient temperature, optimum conditions of biosorption were found to be: a bioMass particle size between 50 and 160 μm, an average saturation contact time of 1 h, a bioMass concentration and a stirring speed in the range of 2.5–3 g L−1 and 200–250 rpm, respectively. The External Mass Transfer was found to be the controlling step in the overall sorption process. The equilibrium data could be fitted by Langmuir isotherm equation. Under these optimal conditions, a biosorption capacity of 63.3 mg Cd2+/g bioMass was obtained.
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Biosorption of Ni2+ from aqueous solution by a NaOH-treated bacterial dead Streptomyces rimosus bioMass
Minerals Engineering, 2004Co-Authors: A. Selatnia, M.z. Bakhti, A Madani, L Kertous, Y Mansouri, Radia YousAbstract:Abstract The nickel biosorption capacity of a Streptomyces rimosus bioMass treated with NaOH (0.1 M) was studied in the batch mode. After pre-treatment of bioMass at the ambient temperature, optimum conditions of biosorption were found to be: a bioMass particle size between 50 and 160 μm, an average saturation contact time of 2 h, a bioMass concentration of 3 g L −1 and a stirring speed of 250 rpm. The External Mass Transfer was found to be the controlling step in the overall sorption process. The equilibrium data could be fitted by Langmuir isotherm equation. Under these optimal conditions a biosorption capacity of 32.6 mg Ni 2+ /g bioMass was obtained.
Guilherme Luiz Dotto - One of the best experts on this subject based on the ideXlab platform.
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a Mass Transfer study considering intraparticle diffusion and axial dispersion for fixed bed adsorption of crystal violet on pecan pericarp carya illinoensis
Chemical Engineering Journal, 2020Co-Authors: Dison S P Franco, Jean L S Fagundes, Jordana Georgin, Nina P G Salau, Guilherme Luiz DottoAbstract:Abstract This research was focused on the representation of the fixed bed adsorption of crystal violet dye (CV) on treated pecan pericarp (Carya illinoensis) using a Mass Transfer approach based on the intraparticle diffusion and axial dispersion. The operation was firstly evaluated in batch mode to determine the External Mass Transfer coefficients, the equilibrium relation, and the thermodynamic aspects. It was then studied the continuous operation. In this case, the breakthrough curves were modeled by a phenomenological approach, based on the combination of the fluid phase Mass balance with intraparticle diffusion (FBID). The results were compared with the Thomas model, which not considers the axial dispersion. The External Mass Transfer was 4.39 × 10-3 cm s−1. The equilibrium relation was better represented by the Langmuir model. The adsorption process was endothermic, with a maximum adsorption capacity of 639.7 mg g−1. Concerning fixed-bed adsorption evaluation, Thomas and FBID models were able to describe the breakthrough tendencies. Nevertheless, the FBID was used to estimate the axial dispersion coefficient, which ranged from 0.79 × 10-6 to 7.81 × 10-6 cm2 s−1.
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interpretations on the mechanism of in iii adsorption onto chitosan and chitin a Mass Transfer model approach
Journal of Molecular Liquids, 2020Co-Authors: Dison S P Franco, Julien Vieillard, Nina Paula Goncalves Salau, Guilherme Luiz DottoAbstract:Abstract The Mass transport mechanism of the In(III) adsorption on chitin and chitosan was elucidated in this research. The chitosan and chitin presented specific surface area values of 3.60 and 4.30 m2 g−1, with average pore radius of 14.30 and 33.10 Ǻ, respectively. It was identified in chitosan and chitin, typical groups, such as N H and C O. It was found that both materials present a rigid surface without the presence of visible pores and cavities, with a geometry that resembles plates. Further analysis indicates the presence of the In(III) on the surface of both materials. The isotherm experiments indicated that the temperature caused an increase in the adsorption capacity for both materials. The Langmuir model was chosen for describing the equilibrium in both cases. The External Mass Transfer Model (EMTM) and Pore Volume and Surface Diffusion Model (PVSDM) were used for describing the indium concentration decay curves for the chitosan and chitin. Nevertheless, the modified Biot number (between 8.82 × 10−4 and 2.71) indicated that, in this case, the External Mass Transfer was the dominant mechanism. In addition, chitin and chitosan were efficient adsorbents for In(III), since that only 0.35 mg L−1 of In(III) remained in solution after adsorption. Chitosan provided faster adsorption kinetics, and this fact was attributed to its higher External surface area. The findings revealed that the overall Mass transport mechanism is as follows: the indium species in the bulk solution are Transferred to the adsorbent surface and then, adsorbed by surface precipitation and/or coordination bonds.
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evaluation of the Mass Transfer process on thin layer drying of papaya seeds from the perspective of diffusive models
Heat and Mass Transfer, 2018Co-Authors: Guilherme Luiz Dotto, Lucas Meili, Eduardo Hiromitsu Tanabe, Daniel Padoin Chielle, Marcos Flavio Pinto MoreiraAbstract:The Mass Transfer process that occurs in the thin layer drying of papaya seeds was studied under different conditions. The External Mass Transfer resistance and the dependence of effective diffusivity (D EFF ) in relation to the moisture ratio (\( \overline{MR} \)) and temperature (T) were investigated from the perspective of diffusive models. It was verified that the effective diffusivity was affected by the moisture content and temperature. A new correlation was proposed for drying of papaya seeds in order to describe these influences. Regarding the use of diffusive models, the results showed that, at conditions of low drying rates (T ≤ 70 °C), the External Mass Transfer resistance, as well as the dependence of the effective diffusivity with respect to the temperature and moisture content should be considered. At high drying rates (T > 90 °C), the dependence of the effective diffusivity with respect to the temperature and moisture content can be neglected, but the External Mass Transfer resistance was still considerable in the range of air velocities used in this work.
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diffusional Mass Transfer model for the adsorption of food dyes on chitosan films
Chemical Engineering Research & Design, 2014Co-Authors: Guilherme Luiz Dotto, C Buriol, Luiz Antonio De Almeida PintoAbstract:Abstract The adsorption kinetics of erythrosine B and indigo carmine on chitosan films was studied by a diffusional Mass Transfer model. The experimental curves were obtained in batch system under different conditions of stirring rate (80–200 rpm) and initial dye concentration (20–100 mg L −1 ). For the model development, External Mass Transfer and intraparticle diffusion steps were considered and the specific simplifications were based on the system characteristics. The proposed diffusional Mass Transfer model agreed very well with the experimental curves, indicating that the surface diffusion was the rate limiting step. The External Mass Transfer coefficient ( k f ) was dependent of the operating conditions and ranged from 1.32 × 10 −4 to 2.17 × 10 −4 m s −1 . The values of surface diffusion coefficient ( D s ) increased with the initial dye concentration and were in the range from 0.41 × 10 −14 to 22.90 × 10 −14 m 2 s −1 . The Biot number ranged from 17.0 to 478.5, confirming that the intraparticle diffusion due to surface diffusion was the rate limiting step in the adsorption of erythrosine B and indigo carmine on chitosan films.
Gordon Mckay - One of the best experts on this subject based on the ideXlab platform.
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the External Mass Transfer of basic and acidic dyes on wood
Journal of Chemical Technology & Biotechnology, 2007Co-Authors: Gordon Mckay, Ian F McconveyAbstract:The parameters affecting the initial adsorption rates of Astrazone Blue dye (Basic Blue 69) on to wood have been studied. A simple model has been proposed to determine the External Mass Transfer coefficients and these have been compared with values obtained using a more complex procedure. The External Mass Transfer coefficient, β, has been shown to vary linearly with agitation and initial dye concentration using log-log coordinates; furthermore β is independent of particle size. The effect of temperature has been studied and the activation energy for the process is 44 ± 2 kJ mol−1. Similar correlations were obtained for the adsorption of Telon Blue dye (Acid Blue 25) on wood. Using log-log correlations, the External Mass Transfer coefficient was found to vary with (rev min−1)0.14, C0−0.27; and a small dependence on particle size was also observed. The activation energy for the External Mass Transfer process was 25 ± 2 kJ mol−1.
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the adsorption of dyestuffs from aqueous solutions using activated carbon iv External Mass Transfer processes
Journal of Chemical Technology and Biotechnology. Chemical Technology, 2007Co-Authors: Gordon MckayAbstract:The parameters affecting the Mass Transfer coefficients for External transport of dyes from water on to activated carbon particles have been studied. The External Mass Transfer coefficients have been determined and correlated as the dimensionless Mass Transfer term, Sh/Sc0.33. The dimensionless function has been found to vary linearly with agitation, initial dye concentration, particle size, adsorbent Mass on log-log coordinates, while reciprocal variation was obtained with absolute temperature. Activation energies were determined for the surface process, for the adsorption of Deorlene Yellow, Victoria Blue, Telon Blue and Disperse Blue 7 and found to be 26.5, 24.5. 25.4 and 74.6 kJ mol-l respectively.
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application of surface diffusion model to the adsorption of dyes on bagasse pith
Adsorption-journal of The International Adsorption Society, 1998Co-Authors: Gordon MckayAbstract:A homogeneous solid phase diffusion model (HSDM) has been developed using a computer to predict the performance of a batch adsorber. The computer program utilises a semi-analytical solution for a two resistance model based on External Mass Transfer and homogeneous solid phase diffusion. The model has been successfully applied to four adsorption systems, namely, the adsorption of AB25, AR114, BB69 and BR22 onto pith. The method produces excellent correlations between experimental and theoretical concentration decay curves in batch adsorbers. The model developed presents a solution using a single solid diffusion coefficient and a single External Mass Transfer coefficient which are sufficient to characterise the system within a range of initial dye concentration, 25–300 mg · dm3 and solid/liquid ratios (w/v) 0.25–2.
Julio Alberto Luna - One of the best experts on this subject based on the ideXlab platform.
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mathematical modeling of drug delivery from one layer and two layer torus shaped devices with External Mass Transfer resistance
European Journal of Pharmaceutical Sciences, 2011Co-Authors: Ignacio Marcelo Helbling, Maria Ines Cabrera, Julio Alberto LunaAbstract:A mathematical modeling of controlled release of drug from one-layer and two-layer torus-shaped devices with External Mass Transfer resistance is presented. Analytical solutions based on the pseudo-steady state approximation are derived. The validity of the equations is established in two stages. In the first stage, the validity of the models derived for more complex systems is determined by comparison with profiles predicted by the simplest model, in asymptotic cases. In the second stage, the reliability and usefulness of the models are ascertained by comparison of the simulation results with vaginal rings experimental release data reported in the literature. In order to measures quantitatively the fit of the theoretical models to the experimental data, the pair-wise procedure is used. A good agreement between the prediction of the models and the experimental data is observed. The models are applicable only to torus-shaped systems in where the initial load of drug is higher than its solubility in the polymer.
