Comparison of linear and non-linear method for determination of optimum equilibrium isotherm for adsorption of copper(II) onto treated Martil sand

Abstract

A comparison of linear and non-linear regression method for predicting the optimum isotherm was made using the experimental adsorption equilibrium data of Cu(II) onto treated Martil sand (TMS). For this, six error analysis methods were used: the coefficient of determination r2, the sum of the squares of the errors, the sum of the absolute errors, the average relative error, the hybrid fractional error function and the Marquardt's percent standard deviation. The error values indicated that non-linear method is a better way to obtain the isotherm parameters describing the Cu(II) adsorption onto TMS. The comparison between different models such as Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, Redlich-Peterson, Koble-Corrigan and Fritz-Schlünder showed that Fritz-Schlünder model was more suitable to describe the equilibrium data. Based on this result and in order to optimize the equilibrium model results for more accurate parameters values, the Fritz-Schlünder equation was modified and called modified Fritz-Schlünder model. As a comparison of such developed modified model to existing mentioned ones, the results showed that the adsorption equilibrium of Cu(II) onto TMS was better described by the modified Fritz-Schlünder model than by others.