Surface Chemistry: Part 4 - Types Of Adsorption Isotherm

Описание: This lecture is fourth part of our series on surface chemistry, First part of the Surface Chemistry explained basics of Adsorption can be watched on    • Surface Chemistry: Adsorption#1   Second part explains the Freundlich Adsorption Isotherm (   • Surface Chemistry: Part 2 - Freundlich Ads...  ). Third part described Langmuir adsorption isotherm (   • Surface Chemistry: Part 3 - Langmuir Adsor...  ) and its comparision with Freundllich isotherm.

This lecture describes various adsorption isotherms as given by Brunauer in 1945. It describes the 5 types of curves, its characteristics and example.

Type – I curve describes Langmuir Adsorption Isotherm and is gives mono-molecular layer formation in adsorption. It is more suitable for Chemical adsorption. There is a rapid increase in extent of adsorption is observed at low pressure. The rate of increase of adsorption decreases with increase in pressure and beyond saturation pressure there is no significant increase in extent of adsorption with increase in pressure i.e adsorption goes for saturation.

Type – II curve better describes BET equation where in there is a completion of first layer of adsorption before second and subsequent layers adsorption begins. The adsorption does not go for saturation in this curve.

Type – III curve describes situation when interaction between adsorbate-adsobent is less than adsorbate-adsorbate interaction. In this case, second and subsequent layer formation begins before completion of first layer. This curve also does not go for saturation.

Type IV and V are extentions of Type II and III respectively. In these curves, adsorption reaches saturation point in subsequent layer also.

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