scholarly journals Adsorption of fluoride by porous adsorbents: Estimating pore diffusion coefficients from batch kinetic data

2019 ◽  
Vol 25 (5) ◽  
pp. 645-651
Author(s):  
Gang Yuan ◽  
Bin Zhao ◽  
Khim Hoong Chu
Keyword(s):  
Algebraic Equation ◽  
Diffusion Coefficients ◽  
Kinetic Data ◽  
Rate Coefficient ◽  
Model Fitting ◽  
Pore Diffusion ◽  
Algebraic Expression ◽  
Batch Adsorption ◽  
Simple Method ◽  
Langmuir Kinetics

A simple method is presented for extracting pore diffusion coefficients from batch adsorption kinetic data. The method employs the classic Langmuir kinetics model which is characterized by a single rate coefficient. An analytical solution in the form of a simple algebraic equation is available for this rate model. Fitting the algebraic equation to batch kinetic data to determine the rate coefficient is straightforward and can be conveniently accomplished using standard spreadsheet programs. The resultant rate coefficient can be converted to the pertinent pore diffusion coefficient via a separate algebraic expression. The proposed modeling approach provides accurate fits of experimental kinetic data taken from the literature and yields acceptable errors in the best estimates for pore diffusion coefficients. Specific examples discussed are the adsorption of fluoride by bone char and laterite adsorbents.

Calculation of Surface Self-Diffusion Coefficients from AES Data on Decay of Thin Metal Films

2005 ◽  
Vol 237-240 ◽  
pp. 727-732 ◽  
Author(s):  
I. Beszeda ◽  
Dezső L. Beke ◽  
E.G. Gontier-Moya ◽  
Yuri S. Kaganovsky ◽  
D. Ianetz
Keyword(s):  
Thin Films ◽  
Diffusion Coefficients ◽  
Kinetic Data ◽  
Metal Films ◽  
In Situ Monitoring ◽  
Simple Method ◽  
Self Diffusion ◽  
Auger Signal ◽  
Equilibrium Calculations

We propose a simple method for calculation of surface self-diffusion coefficients using kinetic data on the decay of thin films – void growth and transformation of the island shape to the equilibrium. Calculations are made taking into account equilibrium wetting angle of the film on a substrate. The kinetic data on the decay of Pd thin films on sapphire and silica substrates were obtained using Auger electron spectroscopy. By in situ monitoring the intensity of the Auger signal from the film, three different stages of the decay could be distinguished. The surface self-diffusion coefficients were calculated for the temperature range 583 – 823 K. The values of the surface diffusion coefficients and the activation energies are discussed compared to those obtained by other methods.

scholarly journals Pore Diffusion Model for the Adsorption of Basic Dyestuffs onto Natural Clay in Batch Adsorbers

1992 ◽  
Vol 9 (2) ◽  
pp. 109-120 ◽  
Author(s):  
Mohammad S. El-Geundi
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Diffusion Model ◽  
Sherwood Number ◽  
Pore Diffusion ◽  
Batch Adsorption ◽  
External Mass Transfer ◽  
Natural Clay ◽  
Pore Diffusion Model ◽  
Best Fit

The adsorption of basic dyestuffs (Basic Blue 69 and Basic Red 22) onto natural clay has been studied using a series of batch adsorption runs. The pore diffusion model (PDM) has been developed based on external mass transfer and pore diffusion to predict the performance of a batch adsorber. A computer program has been developed to generate theoretical Sherwood number-time curves and these results were adjusted to experimental Sherwood number-time curves by means of a ‘best fit’ approach. The variables of initial dye concentration and natural clay mass have been successfully correlated using a single external mass-transfer coefficient, Ks, and a single effective pore diffusion coefficient, Deff. The Ks values are 3.3 × 10−5 and 2.6 × 10−5 m/s for Basic Blue 69 and Basic Red 22, respectively. The Deff values are 7.3 × 10−10 and 9.6 × 10−10 m2/s for Basic Blue 69 and Basic Red 22, respectively.

Diffusion of 60Co, 137Cs and 152Eu in Opalinus Clay

2008 ◽  
Vol 1124 ◽  
Author(s):  
Miguel García-Gutiérrez ◽  
José Luis Cormenzana ◽  
Tiziana Missana ◽  
Manuel Mingarro ◽  
Ursula Alonso
Keyword(s):  
Analytical Solution ◽  
Diffusion Coefficients ◽  
Model Fitting ◽  
Bedding Plane ◽  
Opalinus Clay ◽  
Apparent Diffusion Coefficients ◽  
Fitting Procedure ◽  
Large Dispersion ◽  
Apparent Diffusion ◽  
Paper Filter

AbstractThis study addresses the diffusion of representative sorbing elements, cobalt, cesium and europium in the Opalinus Clay (OPA). The methodology used here to determine diffusion coefficients is the ‘instantaneous planar source’ method. In this setup, a paper filter impregnated with tracer is introduced between two clay samples, avoiding contact between the tracer and the experimental vessels. The apparent diffusion coefficients (Da) perpendicular to the bedding plane, obtained with this experimental method and fitting the experimental results with an analytical solution, were Da(Co) = (2.4-3.5)·10-14 m2/s, Da(Cs) = (5.9-8.0)·10-14 m2/s, and Da(Eu) = (1.0-2.1)·10-15 m2/s. With cobalt and cesium, classical in-diffusion experiments were also performed for comparison, and similar Da values were obtained but with a large dispersion. To analyze the possible effects of the paper filter impregnated with the tracer on the determinations of Da with the analytical solution, one experiment was also analyzed using a detailed stochastic model of the setup. The good agreement between the two modeling approaches confirms the validity of this experimental setup and the analytical model fitting procedure.

scholarly journals Biosorption of lead contaminated wastewater using cattails (Typha angustifolia) leaves: Kinetic studies

2011 ◽  
Vol 76 (7) ◽  
pp. 1037-1047 ◽  
Author(s):  
Sharain Ling ◽  
Collin Joseph ◽  
How Eng
Keyword(s):  
Linear Regression Analysis ◽  
Model Fitting ◽  
Kinetic Studies ◽  
Second Order ◽  
Batch Adsorption ◽  
Typha Angustifolia ◽  
Order Model ◽  
Effective Removal ◽  
Pseudo Second Order ◽  
The Common

In this work, dried leaves of Typha angustifolia (TA), also known as the common cattail, were used as an adsorbent in kinetic studies of Pb(II) adsorption from synthetic aqueous solutions. Batch adsorption studies with dried TA leaves were conducted and they were able to adsorb Pb(II) from 100 mL of a 25 mg L-1 Pb(II) solution effectively with the optimized dosage of 0.6 g. Adsorption equilibrium was achieved within 8 hours with an effective removal percentage of 86.04 %. Adsorption kinetics was further evaluated using four kinetic models, i.e., the pseudofirst order, pseudo-second order, intraparticle diffusion and Elovich model. Fitting of the data was performed based on linear regression analysis. The sorption kinetic data fitted best to the pseudo-second order model with an R2 of 0.9979, followed closely by the Elovich model with an R2 of 0.9952. The obtained results showed the adsorption of Pb(II) by TA leaves, which is an abundant biological material, is feasible, cheap and environmentally friendly.

scholarly journals Improved Security Evaluation of SPN Block Ciphers and its Applications in the Single-key Attack on SKINNY

2020 ◽  
pp. 171-191
Author(s):  
Wenying Zhang ◽  
Meichun Cao ◽  
Jian Guo ◽  
Enes Pasalic
Keyword(s):  
Block Cipher ◽  
Internal State ◽  
Block Ciphers ◽  
Security Evaluation ◽  
Algebraic Expression ◽  
Single Pair ◽  
Integral Property ◽  
Simple Method ◽  
Truncated Differential ◽  
Impossible Differentials

In this paper, a new method for evaluating the integral property, truncated and impossible differentials for substitution-permutation network (SPN) block ciphers is proposed. The main assumption is an explicit description/expression of the internal state words in terms of the plaintext (ciphertext) words. By counting the number of times these words occur in the internal state expression, we can evaluate the resistance of a given block cipher to integral and impossible/truncated differential attacks more accurately than previous methods. More precisely, we explore the cryptographic consequences of uneven frequency of occurrences of plaintext (ciphertext) words appearing in the algebraic expression of the internal state words. This approach gives a new family of distinguishers employing different concepts such as the integral property, impossible/truncated differentials and the so-called zero-sum property. We then provide algorithms to determine the maximum number of rounds of such new types of distinguishers for SPN block ciphers. The potential and efficiency of this relatively simple method is confirmed through applications. For instance, in the case of SKINNY block cipher, several 10-round integral distinguishers, all of the 11-round impossible differentials, and a 7-round truncated differential could be determined. For the last case, using a single pair of plaintexts differing in three words so that (a = b = c) ≠ (a’ = b’ = c’), we are able to distinguish 7-round SKINNY from random permutations. More importantly, exploiting our distinguishers, we give the first practical attack on 11-round SKINNY-128-128 in the single-key setting (a theoretical attack reaches 16 rounds). Finally, using the same ideas, we provide a concise explanation on the existing distinguishers for round-reduced AES.

scholarly journals Comparison of wood pyrolysis kinetic data derived from thermogravimetric experiments by model-fitting and model-free methods

2020 ◽  
Vol 212 ◽  
pp. 112818 ◽  
Author(s):  
Antonio Soria-Verdugo ◽  
Marco Tomasi Morgano ◽  
Hartmut Mätzing ◽  
Elke Goos ◽  
Hans Leibold ◽  
...  
Keyword(s):  
Kinetic Data ◽  
Model Fitting ◽  
Wood Pyrolysis ◽  
Model Free ◽  
Pyrolysis Kinetic
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