Applicability comparison of different models for ammonium ion adsorption by multi-walled carbon nanotube

The aim of the present research was to remove ammonium ions (NH4+) from aqueous solution using multi-walled carbon nanotubes (MWCNTs). The adsorption behavior of ammonium ions (NH4+) from aqueous solution by multi-walled carbon nanotubes (MWCNTs) was investigated as a function of some parameters such as contact time, initial ammonium ion concentration, and temperature. Adsorption equilibrium data for the removal of ammonium ions were examined by fitting the experimental data to various models. Six isotherm models were used to describe the isotherm experiment data. Langmuir, Freundlich, and Halsey isotherm models provided much better isotherm data fitting than the other isotherm models (Temkin, D–R, and Harkins–Jura). The Langmuir equation was found to best represent the equilibrium data for ammonium ion-MWCNT system. The average relative errors (ARE) value demonstrated that the Langmuir provided the best model for these data.