Topics: Adsorption, Freundlich equation, Gas Pages: 2 (326 words) Published: November 7, 2010
Introduction to freundlich adsorption isotherm
Let us discuss about the introduction to Freundlich adsorption isotherm. The adsorption the surface energy is decrease. The solid on which adsoprtion occurs is called adsorbent and the substance that is adorbed is called as adorbate. The total phenomenon is called as the freundlich adsorption isotherm. In the illustration cited above, charcoal is adsorbent and the particles or molecules of the dye are adsorbate and the total phenomenon is adsorption. Explanation of Freundlich Adsorption Isotherm

The following is the relation between the adsorption or gaseous adsorbent at definite temperature and the pressure of the gas is the first equation. n>1

Where x/m is the adsorption per gram of adsorbent which is obtained be dividing the amount of adsorbate (x) by the weight of the adsorbent (m). The pressure of the gas is p, k and n are constants. This relation is called as the freundlich adsorption isotherm. As see the following diagram. The value of x/m is increasing with increase in p but as n>1 it does not increase suddenly. This curve is also called the freundlich isotherm curve.

Taking the logarithms of a first equation.

Hence, if a graph of log x/m is plotted against log p, it will be a straight line in the following diagram.
From this the value of slope equal to 1/n and the value of intercept equal to log k can be obtained. Over and above, it the graph of log x/m against log p comes out to be a straight line, it can be assured that the freundlich adsorption isotherm is satisfied for this system. Next we see the limitations of freundlich adsorption isotherm. Limitation of freundlich adsorption isotherm

It is applicable within certain limits of pressure. At higher pressure, it shows deviation. •The values of constants k and n change with...
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