Comparison of two and three parameters adsorption isotherm for Cr(VI) onto Kraft lignin

Equilibrium studies were carried out for the sorption of Cr(VI) onto Kraft lignin as an adsorbent. The experimental data were fitted to the Freundlich, Langmuir, Temkin, Dubinin–Radushkevich, Redlich–Peterson, Sips and Toth isotherms by non-linear method. We presented the comparison of two- and three-parameter isotherm. Only non-linear regression method was used in selecting the optimum isotherm for the experimental data. The coefficient of correlation was used to select the best theoretical isotherm. The best two-parameter isotherm is equally Langmuir and Dubinin–Radushkevich isotherm. From three-parameter isotherms Redlich–Peterson isotherm proved to be the best. Generally, Redlich–Peterson isotherm was found to be the best representative for Cr(VI) adsorption on the sorbent.

► The adsorption of Cr(VI) onto Kraft lignin as an adsorbent.
► Non-linear regression method with two- and three-parameters was used.
► Coefficient of determination was used to test the best-fitting isotherm.
► Redlich–Peterson model is the best representative for Cr(VI)-sorption on the sorbent.