Ammonium Adsorption on Natural Zeolite (clinoptilolite): Adsorption Isotherms and Kinetics Modeling

A batch sorption process for removal of ammonium ions from aqueous solution using natural zeolite was studied. Tree different particle sizes of zeolite (1-2 mm, 2-4 mm and 4-10 mm) were used in the experiments. Sorption of ammonium ions on natural zeolite were carried out at 298 K with the initial concentrations of ammonium in the range of 1000 – 7000 mg NH4 -N/dm. Equilibrium data were fitted by Freundlich and Langmuir isotherm and sorption kinetic data by pseudo-first and second order. The parameters were estimated by linear and non-linear method. Results show that non-linear method may be superior way to compute the parameters. The Langmuir isotherm model fitted better the experimental data with a maximum monolayer adsorption capacity of 58.36 mg NH4 -N/g (1-2 mm), 49.02 mg NH4 -N/g (2-4 mm) and 46.46 mg NH4 -N/g (4-10 mm), respectively. Also, the pseudo-second-order kinetic model was the best applicable model to describe the sorption kinetics. The obtained results suggest that the natural zeolite is a good adsorbent for removal of ammonium ions from aqueous solution and that ion exchange increased with decreasing of particle sizes of natural zeolite.