Adsorpcija amonijum jona i amonijaka iz vodene sredine na bentonitu i mordenitu.

This paper studies adsorption of ammonium ions and ammonia from aqueous solution onto bentonite and on a synthetic zeolite mordenite. Bentonite and mordenite are characterized by chemical composition and specific surface determination, and X-ray diffraction analysis. The removal of ammonium ions and ammonia was performed in a batch system. The influence of various parameters, such as adsorbent weight, contact time and temperature, on adsorption process was examined. Optimal contact time for reaching adsorption equilibrium is 3 hours for bentonite and 24 hours for mordenite, while the optimal weights are 0,2 g and 0,5 g respectively. The pH values of the solution and temperature are the parameters which affect the equilibrium of the non-ionized form of ammonia (NH3 ∙ nH2O) and/or the ionized form (NH4 +). In the acidic medium, the predominant form of ammonia is NH4 +, while in the alkali medium (pH over 9,5) the dominant form is NH3. As aqueous solutions of ammonia in the concentration range 0,02-0,08 mol/L are used in this study, pH of these solutions is over 9,5 and dominant form in this case is NH3. Due to this, it can be assumed that adsorption process is the primary mechanism of ammonia removal, while the ion exchange process is negligible. Temperatures effect on adsorption process was studied at three temperatures: 293, 303 and 313 K. The adsorption capacity of both adsorbents increases with increasing temperature, which indicates that adsorption process is endothermic and chemisorption occurs in addition to physical adsorption. Experiments show that adsorption curves of both adsorbents, at all observed temperatures, pass through multiple "plateaus" and, according to Giles classification, these isotherms are S4-type. This type of isotherms described multilayered and cooperative adsorption. The obtained results were fitted to Freundlich's and Langmuir's linear theoretical model. Based on the values of the correlation coefficient (R2), the results showed that the adsorption of ammonium ions and ammonia from aqueous solution obeys the Freundlich adsorption model. Bentonite proved to be a better adsorbent than mordenite. [ABSTRACT FROM AUTHOR]