5.4.4 DEFINITION OF THE SOLUTE FLux The flux of solute diffusing at any location
ID: 1766845 • Letter: 5
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5.4.4 DEFINITION OF THE SOLUTE FLux The flux of solute diffusing at any location y is defined as the moles of solute per unit time per unit area normal to the direction of diffusion, i.e., j,-J,/S. The flux at the surface of the plate in Figure 5.1 is therefore given by ac ay 0 For the situation shown in Figure 5.1, we can find C/y, o by differentiating Equation 59 with respect to y and evaluating this result at y = 0, we find for this case that DCo (5.12) Equation 5.12 shows that the solute flux at the surface of the plate is inversely proportional to the square root of the contact time of the plate with the fluid.Explanation / Answer
According to the first image on Solute Flux Definition, Mass transport of molecules in a solution or molecular transport across a barrier is normally measured by fluxes. The flux of a solute is simply defined as the mass or number of molecules moving through a given crosssectional area during a given period of time.
where J is the flux of a mass of compound m, moving through a cross-sectional area A during time t as illustrated. The unit for a flux value could thus be mol cm-2 min-1, or alternatively mg cm-2 h-1. Movement of molecules in solution or molecular transport across barriers can be caused by migration or diffusion. Migration is movement of molecules caused by an external force that is acting on each of the solute molecules. Such external forces can be gravity, electrical fields (in case of charged solutes) or hydrodynamic flow. Diffusion is the random thermal movement of molecules in a solution, and thus diffusion may only cause a net transport of molecules in the presence of a concentration gradient.
As per 2nd image, the equations relates to Solution for concentration profile for diffusion from a flat plate into quiecent fluid.
It represents the concentration of the solute and typical units are moles per cubic centimeter or moles per liter.The surface are normal to y-direction of solute diffusion. The solute diffusitivity generally depends on the size of solute and physical properties of fluid or material in which the solute is diffusing.
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