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