The effect of ionic strength on the ammonium adsorption and desorption by Semnan clinoptilolite zeolite

The high affinity of zeolite for NH4+ and the possibility of releasing it over time have enabled them to be used as NH4+ and/or NH3 adsorbents during composting, in poultry facilities and controlled-release NH4+ fertilizers. Understanding the adsorption and desorption processes in natural zeolite is necessary for effective utilization of natural zeolites as NH3 and NH4+ adsorbents and consequently as controlled-release NH4+ fertilizers. The objectives of this study were to determine the adsorption isotherm and desorption kinetics of NH4+ by Semnan clinoptilolite zeolite in different ionic strength (0.03, 0.1 and 0.3 M NaCl) and identify empirical models that best describe the adsorption and desorption processes. The results showed that Initial NH4+ concentration and ionic strength significantly affected the amount of NH4+ adsorbed. A decrease in ionic strength resulted in greater amounts of NH4+ being adsorbed and therefore greater sorption efficiency at any given solution concentration. The experimental data could be well fitted by Freundlich, Langmuir, Temkin, Redlich-Peterson and Langmuir-Frendlich models.