What is an adsorption isotherm? Describe Freundlich adsorption isotherm.

Explanation

Adsorption isotherm represents the variation of the mass of the gas adsorbed per gram of the adsorbent with pressure at constant temperature. Freundlich Adsorption isotherm: Freundlich in 1909, gave an empirical relationship between the quantity, of a gas adsorbed by unit mass of solid adsorbent and pressure at a particular temperature. The relationship can be expressed by the following equation:

where x is the mass of the gas adsorbed by mass 'm' of the adsorbent at pressure P,k and n are constants which depend on the nature of the adsorbent and the gas at a particular temperature. The relationship is generally represented in the form of a curve where mass of the gas adsorbed per gram by the adsorbent is plotted aganist pressure. these curves indicate that at a fixed pressure, there is a decrease in physical adsorption with increase in temperature. These curves always seem to approach saturation at high pressure.
Taking log of equation (i), we get
`log.(x)/(m) = log k _(1)/(n) log P`