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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]

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]

The study examined the rate of diethyl ether dehydration reaction on mordenite (NaM) and Mn(II)-mordenite (Mn(II)M) as catalysts. The reaction was observed in a gas phase in the temperature interval from 426 K to 653 K. The products of the reaction in addition to ethene and water is also a small quantity of butene that occurs on NaM. At the temperature of 653 K on NaM the reaction ran as the first order reaction without an initial period, while at lower temperatures both on NaM and on Mn(II)M the reaction had an initial period. Therefore, the experiments were conducted on Mn(II)M as a catalyst, in which water was added to the reaction mixture. The experiment with the addition of water on Mn(II)M was conducted at 455 K, and the ratio of diethyl ether and water at the beginning of the reaction was 1:2. The reaction ran as the first order reaction without an initial period and the product of the reaction in addition to water was only ethene. The introduction of Mn2+ ion in the mordenite structure significantly sped up the reaction, and because of that the reaction could be observed at the temperatures lower by 150-200 K. The presence of Mn2+ ion in the mordenite structure resulted in the increase of the total number, but also the acidity of the active centers on the zeolite surface, which caused an increased catalytic activity of Mn(II)M. [ABSTRACT FROM AUTHOR]