Adsorption of Toxic Gases on Iron-Incorporated Na-A Zeolites Synthesized from Melting Slag

Abstract

Iron incorporated zeolites were prepared from Na-A type zeolite synthesized from melting slag and FeCl3 solution and applied as adsorbents for NH3 and H2S gases. Iron incorporated zeolite was pelletized, calcined and used for gas adsorption experiment. XRD analyses of the zeolite revealed that Fe 3þ concentration of solution more than 90 mM could destruct the zeolite network structure. It was observed that the gas adsorption capacities of these zeolite pellets depend significantly on iron concentration of solution and calcination temperature. The type of binders affected a little on gas adsorption capacities. From adsorption results, adsorption capacity for NH3 was proportional to Fe 3þ concentration and it was increased with calcination temperature up to 500 � C, but it was decreased over 600 � C. Pellets prepared from 56 mM Fe 3þ solution calcined at 500 � C showed highest ammonia adsorption capacity (3.7%). This iron incorporated Na-A type zeolites showed much higher adsorption capacities for NH3 (2:4� 3:7%) than commercially available activated carbons (0:16� 0:44%) and zeolites (0:23� 0:60%). In the case of adsorption capacities for H2S, adsorption capacity was proportional to Fe3þ concentration and inversely proportional to calcination temperature. Pellets prepared from 78 mM Fe 3þ solution calcined at 200 � C showed highest hydrogen sulfide adsorption capacity (1.5%). Adsorption capacity (0:2� 1:5%) was found to be lower than that of the commercial activated carbons (1:2� 2:4%) and higher than that of commercial zeolites 4A (0.15%) and 13X (0.91%). Higher ammonia adsorption in iron incorporated Na-A zeolites could be possibly due to development of number of acid sites on the zeolites surface due to incorporation of Fe 3þ ion. [doi:10.2320/matertrans.M2009175]