Adsorption of Ammonium Ions onto a Natural Zeolite: Transcarpathian Clinoptilolite

Abstract

A study was carried out of ammonium ion sorption from synthetic aqueous solutions by Transcarpathian clinoptilolite, a natural zeolite, under static conditions. The main physical properties of the clinoptilolite and the basic parameters of its porous structure were determined. Values of the specific surface area and of the pore volume occupied by sorbed substances were calculated using the relative moisture content established and the maximum sorption capacity exhibited towards ammonium ions as well as a nitrogen adsorption/desorption method. Ammonium ion sorption by the zeolite appeared to be complete within 24 h for all fraction sizes, initial NH 4 + ion concentration and adsorbate volumes. The amounts of NH 4 + ions sorbed increased with increasing initial NH 4 + concentration and decreasing adsorbate volumes, with the maximum sorption capacity exhibited by the clinoptilolite being 0.64 mequiv/g. The sorption effectiveness decreased somewhat with increasing fraction size. The Langmuir and Freundlich models were applied to the data obtained from the batch studies with the first model exhibiting the more satisfactory correlation coefficient value (0.996 and 0.959, respectively).