What is the differences between the First portion/stage , Second portion/stage and third stage
What if the results show only single portion? what does it mean or convey about the finding?
Likewise What if the results shows only two portion/ stage mechanism?
(My analysis result showed two stage)
kindly comment/help
Weber and Morris had presented the intraparticle diffusion (IPD) model in 1962. Of the total 57 articles surveyed IPD model has been applied in three different forms:
(1) qt (the amount of adsorption at any time) is plotted against t1/2 (the square root of time) to get a straight line that is forced to pass through the origin;
(2) multi-linearity in qt vs. t1/2 plot is considered (that is, two or three steps are involved to follow the whole process). In this form, the external surface adsorption or instantaneous adsorption occurs in the first step; the second step is the gradual adsorption step, where intraparticle diffusion is controlled;
and the third step is the final equilibrium step, where the solute moves slowly from larger pores to micropores causing a slow adsorption rate. The time required for the second step usually depends on the variations of the system (including solute concentration, temperature, and adsorbent particle size), which is difficult to be predicted or controlled;
(3) qt is plotted against t1/2 to obtain a straight line but does not necessarily pass through the origin; that is, there is an intercept. Almost all the intercepts reported in the literature are positive, indicating that rapid adsorption occurs within a short period of time. To the present knowledge, this type of initial adsorption behaviour has never been reported.
Regards
Bachir Achour what if the adsorption shows two line stage of adsorption, firstly there is a rapid adsorption and the other stage where saturation/ equilibrium is achieved.
How do you explain the behavior??
Dear Akito I Sema,
This can be explained by the experimental plot of the adsorption isotherm. For example, the study of the adsorption of a gas on the surface of solid shows that there is the formation of an equilibrium between the pressure of this gas and the quantity of gas adsorbed per unit mass of solid. . We thus observe at least three types of adsorption isotherms: In the first case, the quantity expressed in mass of adsorbed gas increases very quickly as a function of the pressure. It reaches a plateau as if there were saturation of the surface of the solid. In other words, the solid is completely covered by a liquid monomolecular film of gas molecules. Of course, manipulation is limited to the saturation vapour pressure of the gas. Above the saturation vapour pressure, the gas liquefies. The second case corresponds to the previous case, with in addition, after saturation of the surface of the solid by a first layer, the appearance of formation of several layers of gaseous molecules on the surface. The third case corresponds to the formation of several monolayers on the surface of the solid.
Regards
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