Adsorption Kinetics and Isotherm Models: A Review

Abstract

Adsorption Kinetics describes the rate at which solute is adsorbed and the
resident time of the adsorbates on the solid-liquid interface. Adsorption
isotherms play important role in determining the interaction between adsorbate
and adsorbent and the optimum adsorption capacity of adsorbent. This article
considered selected adsorption kinetics and isotherms models. Pseudo first
order, Pseudo second order, Elovich, Bhattacharya and Venkobachar, and
Natarajan and Khalaf were adsorption kinetics reviewed on the assumption that
the process behaves as heterogeneous reaction at solid-liquid interface.
Adsorption kinetics equation presented takes the form of straight line, the slopes
and intercepts of the plots are used to determine adsorption capacity of
adsorbent, rate constant, rate of adsorption and intraparticle diffusion. Value of
correlation coefficient obtained is used in determining the adsorption kinetics
model that best describe the adsorption process. Langmuir, Freundlich, RadlichPeterson, Temkin and Dubinin-Radushkevic adsorption isotherms were
presented. Their slopes and intercepts provide insight on adsorption affinity,
mean free energy, whether the adsorption is physisorption or chemisorptions,
single or multilayer. Adsorption kinetics and isotherms reviewed provide
essential information required for understanding adsorption process.