Relevance of isotherm models in biosorption of pollutants by agricultural byproducts

•The significance and the characteristic features of the biosorbents from agricultural byproducts were discussed.•The adsorption isotherm models of two, three, four and five parameters were presented.•The significance of adsorption isotherm models in the assessment of biosorbents for different pollutants was summarized.•Most of the adsorption studies carried out were best fitted with the two and three parameter isotherm models.

Industries generating wastewater with elevated concentrations of pollutants (e.g. metals, dyes, phenolic compounds, anions, etc.) need specialized atreatment systems. Adsorption is one of the most extensively applied techniques for the removal of pollutants from the industrial effluents. The prominent and emerging trend of subjecting biosorbent in the adsorption technology is mainly because of their natural existence, abundance, renewable, biodegradable and economic features. The adsorption isotherm equations used to describe the experimental data and the thermodynamic assumptions of the models often provide some insight into the sorption mechanism, the surface properties and affinity of the biosorbent. This paper presents a state of the art on the review of adsorption isotherm models in an exhaustive manner on the basis of two, three, four and five parameters respectively. Focuses on the various sources of agricultural byproducts as biosorbents and describes on the potential applications of different adsorption isotherm models for the evaluation of the wastewater pollutants biosorption. It is evident from the literature survey that various adsorption isotherm models have been considered under study by the researchers but mostly two and three parameter isotherm model were best fitted the equilibrium data. This paper reviews the adsorption isotherm models on the basis of parameters that can be applied for exploring a novel biosorbents.