scholarly journals Adsorption Kinetics of Cationic Dyestuffs on to Natural Clay

1996 ◽  
Vol 13 (4) ◽  
pp. 295-303 ◽  
Author(s):  
Mohammad S. El-Geundi
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Size Range ◽  
External Mass Transfer ◽  
Natural Clay ◽  
Particle Size Range ◽  
Design Variables ◽  
Step Model ◽  
Kinetics Of

A three-step model has been proposed for the adsorption of cationic dyestuffs (Basic Blue 69 and Basic Red 22) from aqueous solutions on to natural clay. The rate of adsorption is controlled initially by the boundary layer film and an external mass-transfer coefficient Ks has been determined for this process under the influence of a number of design variables. Two approaches, designated methods 1 and 2, are available for determining the external mass-transfer coefficient. Using log-log correlations, the external mass-transfer coefficient was found to vary linearly with the agitation speed, the clay particle size range and the mass of clay employed.

Mass Transfer Coefficients during Steel Decarburization in a RH Degasser

2008 ◽  
Vol 273-276 ◽  
pp. 679-684
Author(s):  
Roberto Parreiras Tavares ◽  
André Afonso Nascimento ◽  
Henrique Loures Vale Pujatti
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Gas Flow ◽  
Vacuum Chamber ◽  
Volumetric Mass Transfer Coefficient ◽  
Gas Flow Rate ◽  
Rh Process ◽  
Kinetics Of

The RH process is a secondary refining process that can simultaneously attain significant levels of removal of interstitial elements, such as carbon, nitrogen and hydrogen, from liquid steel. In the RH process, the decarburization rate plays a very important role in determining the productivity of the equipment. The kinetics of this reaction is controlled by mass transfer in the liquid phase. In the present work, a physical model of a RH degasser has been built and used in the study of the kinetics of decarburization. The effects of the gas flow rate and of the configurations of the nozzles used in the injection of the gas have been analyzed. The decarburization reaction of liquid steel was simulated using a reaction involving CO2 and caustic solutions. The concentration of CO2 in the solution was evaluated using pH measurements. Based on the experimental results, it was possible to estimate the reaction rate constant. A volumetric mass transfer coefficient was then calculated based on these rate constants and on the circulation rate of the liquid. The logarithm of the mass transfer coefficient showed a linear relationship with the logarithm of the gas flow rate. The slope of the line was found to vary according to the relevance of the reaction at the free surface in the vacuum chamber. A linear relationship between the volumetric mass transfer coefficient and the nozzle Reynolds number was also observed. The slopes of the lines changed according to the relative importance of the two reaction sites, gas-liquid interface in the upleg snorkel and in the vacuum. At higher Reynolds number, the reaction in the vacuum chamber tends to be more significant.

scholarly journals Studies of the Dimensionless Mass-transfer Coefficient During the Adsorption of Basic and Acid Dyes on to Bagasse Pith

1994 ◽  
Vol 11 (2) ◽  
pp. 73-81 ◽  
Author(s):  
Mamdouh M. Nassar ◽  
Mohammed S. El-Geundi
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Particle Diameter ◽  
External Mass Transfer ◽  
Acid Dyes ◽  
Dimensionless Function ◽  
Bagasse Pith ◽  
System Variables

The influence of agitation, particle diameter and mass of adsorbent on the external mass-transfer coefficient is discussed. The computed values correlate with the dimensionless function Sh/Sc1/3. It has been found that Sh/Sc1/3 varies linearly with the variables studied and may be correlated with system variables via the equation Sh/Sc1/3 = A(variable)B.

scholarly journals Dynamic studies of nitrophenols sorption on perfil in a fixed-bed column

2008 ◽  
Vol 27 (2) ◽  
pp. 123 ◽  
Author(s):  
Zvezdelina Yaneva ◽  
Mirko Marinkovski ◽  
Liljana Markovska ◽  
Vera Meshko ◽  
Bogdana Koumanova
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Dispersion Coefficient ◽  
Fixed Bed ◽  
External Mass Transfer ◽  
Fixed Bed Column ◽  
Axial Dispersion Coefficient ◽  
Solid Diffusion

The adsorption of two substituted nitrophenols, namely 4-nitrophenol (4-NP) and 2,4-dinitrophenol (2,4-DNP), from aqueous solutions onto perfil was studied using a fixed bed column. The theoretical solid diffusion control (SDC) model describing single solute adsorption in a fixed bed based on the Linear Driving Force (LDF) kinetic model was successfully applied to the investigated systems. The model parameters of solid diffusion coefficient, DS, axial dispersion coefficient, DL, and external mass transfer coefficient, kf, for the investigated systems were estimated by the means of a best fit approach. Some deviations were found between the predicted and the experimental data which reflect the fact that the assumptions of the model were not quite fulfilled for these experiments. It is necessary to adjust the values of the solid diffusion coefficient, the axial dispersion coefficient and the external mass transfer coefficient in order to obtain a satisfactory agreement between the simulated and the experimental breakthrough curves. A Biot number was used as an indicator for the intarparticle diffusion. The Biot number was found to decrease with the increase of bed depth, indicating that the film resistance increased or the intraparticle diffusion resistance decreased.

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