Batch adsorption isotherm models applied in single and multicomponent adsorption systems – a review

Abstract

The advancement in urbanization and industrialization in recent times due to increase in population has led to generation of huge quantities of pollutants which are discharged into the biota without proper treatment leading to environmental pollution. This situation is causing a lot of concern to environmental conservationists. It has been proven that adsorption is superior to most of the conventional treatment techniques due to the fact that it is easy to design, insensitive to toxic pollutants, cheap and very efficient in removing pollutants at low solution concentrations. An adsorption isotherm relates the concentration of adsorbed adsorbate in the adsorbent to that in the bulk solution at constant pH and temperature. Hence isotherm modeling can predict the amount of adsorbate a given quantity of adsorbent can remove from solution under given conditions. This article reviewed various isotherm models used to describe adsorption systems whether singular or multiple-component. The applications, advantages and disadvantages are discussed. Error functions which bring out the closeness of predicted results to experimental data are discussed. The difficulty in predicting physisorption with isotherm models is mentioned suggesting that researches should be carried out applying IUPAC type VI Isotherms to resolve the problem.