Concentration-dependent diffusivity of benzoic acid in water and its influence on the liquid-solid mass transfer (original) (raw)

Some Measurements of Diffusion in Liquids

The Journal of Physical Chemistry, 1955

Diffusion coefficients for iodine and toluene in a series of saturated hydrocarbons and for benzoic, acet,ic and formic acids in a number of organic solvents are reported. Data were obtained by the diaphragm cell method.

Diffusivity: A Review on Research and Studies with Insight into Affecting Parameters

http://ijshr.com/IJSHR\_Vol.1\_Issue.4\_Oct2016/IJSHR0002.pdf, 2016

Diffusivity is number of moles transferred per unit area per unit time per unit concentration gradient. The molar flux in molecular diffusion is divided into two parts. One is due to bulk motion and other is due relative speed of particle or molecule. Diffusion plays major role in applications such as drying, catalysis and many other chemical engineering applications. Diffusion through solid is classified as diffusion through porous solid, diffusion through polymers and surface diffusion. Depending on size of molecule, porous diffusion is classified as Fickian, Knudsen diffusion and transient diffusion. Various investigators have carried out studies on diffusivity and its affecting parameters. Current review summarizes research and studies on diffusivity and its affecting parameters.

Remarks on the analysis method for determining diffusion coefficient in ternary mixtures

Comptes Rendus Mécanique, 2013

The objective of this work is the determination of diagonal and cross-diagonal molecular diffusion coefficients in a ternary mixture, using the 'Sliding Symmetric Tubes' (SST) technique. The analyzed mixture consists of two aromatics and one normal alkane (tetrahydronaphthalene-dodecane-isobutylbenzene) with an equal mass fraction for all components (1:1:1) at 25 • C. The analytical solution corresponding to the SST technique has been successfully derived. The different fitting procedures were utilized by two scientific teams to subtract diffusion coefficients from the experimentally measured time-dependent concentration field. None of the attempts provided reliable results for the data from a single experiment. The "simplex"-based methods display reasonable results assuming that crossdiagonal coefficients are close to zero, i.e. quasi-binary and diluted mixtures. The results obtained by "trust region method" are satisfactory if the initial guess is good. To achieve better results, it is necessary to increase the number of experimental data.

1st International Conference on Diffusion in Solids and Liquids “DSL-2005”

Abstract It has been shown very recently that the diffusion non-linearity, due to the strong composition dependence of the diffusion coefficients, can lead to surprising effects on nanoscale: i) non parabolic shift of interfaces (both in ideal and phase separating systems), ii) sharpening of an initially diffuse interface in ideal systems. Some of these can not be interpreted even qualitatively from Fick s classical equations.

The Relationship between the Molecular Weight, Time and Rate of Diffusion of Substances

The relationship between the molecular weight and rate of diffusion was determined using the glass tube test and the agar-water gel test. In the glass tube test, two cotton plugs with equal sizes were soaked at the same rate to two different substances: the hydrochloric acid (HCl) and ammonium hydroxide (NH4OH), and were inserted to both ends of a glass tube. The substance (NH4OH) having a lighter molecular weight diffused faster forming a white smoke. For the agar-water gel set up, three solutions, namely, KMnO4, K2Cr2O7 and methylene blue, were dropped into three different wells in a petri dish of agar-water gel. Methylene blue displayed the smallest diameter and diffused at the slowest rate because it has the largest molecular weight. Hence, the higher the molecular weight, the slower the rate of diffusion.

The Effect of Molecular Weight on the Rate of Diffusion of Substances1

The study was conducted to determine the effect of molecular weight on the rate of diffusion of substances. In able to do this, two tests were conducted -tube test and agar-water gel test. Two cotton balls of the same size were used in the setup of the tube test. One cotton ball was moistened with hydrochloric acid (HCl) while the other was moistened with ammonium hydroxide (NH4OH). The moistened cotton balls were then plugged to both ends of the glass tube. HCl (MW=36.4611 g/mole) diffused at a lower rate as compared to NH4OH (MW=35.0459 g/mole) resulting a formation of a white ring of smoke around the glass near the HCl. In the agar-water gel setup, a petri dish containing three wells of equal diameters was used. A drop of potassium permanganate (KMnO4), potassium dichromate (K2Cr2O7) and methylene blue was placed into each of the three wells. After 25 minutes, methylene blue with the largest molecular weight (MW=374 g/mole) resulted to have a smaller diameter (7mm) with the lowest average rate of diffusion (0.080 mm/min.) as compared to KMnO4 (MW=158 g/mole; 14mm; 0.36mm/min.) and K2Cr2O7 (MW=294 g/mole; 12mm; 0.28mm/min.). Thus, the higher the molecular weight of a substance, the slower its rate of diffusion.

A diffusion study on the ternary system, sodium cholate–sodium deoxycholate–water

Journal of Molecular Liquids, 2010

The mutual diffusion coefficients, D ij , of the ternary system sodium cholate (NaC, component 1) + sodium deoxycholate (NadC, component 2) + water have been determined at five average compositions (c 1 , c 2 ) keeping c 1 constant and varying c 2 . The possibility to obtain expressions for the four diffusion coefficients in term of the micellization parameters and of the diffusivity of the species in solution is discussed. Data have been qualitatively interpreted. Results for the main term diffusion coefficients have been used in the much more difficult analysis of the cross term diffusion coefficients.