Isotherm models
An adsorption isotherm equation is an expression of the
relation between the proportion of solute adsorbed and the
concentration of the solute in the fluid phase, since for
solid–liquid system, the studies of adsorption isotherms
are very important to realize information about adsorption
capacity of adsorbents. Therefore, the correlation of
equilibrium data using an equation is essential for practical
adsorption operation [38]. In order to investigate the
sorption isotherm, two equilibrium models were analyzed:
Langmuir and Freundlich isotherm equations. These both
isotherm models were first derived and used for gas
adsorption by microporous adsorbents, and then extended
to solute adsorption from aqueous solutions. The Langmuir
model is obtained under the ideal supposition of a totally
homogeneous adsorption surface, whereas the Freundlich
isotherm is suitable for a highly heterogeneous surface