Adsorption characteristics of ammonium ion by zeolite 13X.

With synthetic wastewater, lab-scale batch experiments and column experiments were carried out to investigate the adsorption characteristics of ammonium ion by zeolite 13X which is a hydrothermally synthetic byproduct accompanied with preparation of potassium carbonate from insoluble potash ores. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms for ammonium ion uptake and the Langmuir model agrees very well with experimental data. Thermodynamic parameters including changes in the standard free energy (DeltaG(0)), enthalpy (DeltaH(0)) and entropy (DeltaS(0)) were also calculated. The results show that the exchange process of ammonium ion by zeolite 13X is spontaneous and exothermic. The pseudo second-order kinetic model was found to provide excellent kinetic data fitting (R(2)>0.999). The effects of relevant dynamic parameters, such as influent flow rate, adsorbent bed height and initial ammonium ion concentration on the adsorption of ammonium ion were examined, respectively. The Thomas model was applied to predict the breakthrough curves and to determine the characteristic parameters of column useful for process design and was found suitable for describing the adsorption process of the dynamic behavior of the zeolite 13X column. The total adsorbed quantities, equilibrium uptakes and total removal percents of ammonium ion related to the effluent volumes were determined by evaluating the breakthrough curves obtained at different conditions.