Removal of ammonia from waste air streams with clinoptilolite tuff in its natural and treated forms

Abstract

Natural and impregnated clinoptilolite tuffs were studied to assess their potential to remove ammonia from air and, in a subsequent application, to use the spent adsorbent as a fertilizer. H2SO4, H3PO4 and HNO3, as agents containing important plant nutrients compatible with soil, were selected for impregnation to enhance sorption capacity of the natural clinoptilolite tuffs for ammonia removal. Sorbents were characterized using N2 adsorption isotherms at 77 K, X-ray analysis and high pressure mercury porosimetry. Ammonia breakthrough curves on fixed beds of sorbent were determined using appropriate NH3 and H2O input concentrations, flow rates and temperatures similar to the conditions in animal breeding farms. Impregnated clinoptilolite tuffs showed adsorption capacities comparable to SSP-4, an activated carbon that is commercially used for NH3 removal. Impregnations with H2SO4 and HNO3 are particularly important, since such modified adsorbents exhibit relatively high breakthrough capacities, thus rendering them potentially useful for practical applications in controlling ammonia emissions. The main contribution to the sorption capacity enhancement on impregnated clinoptilolite tuff samples seems to be due to the chemical reaction of ammonia with acids remaining in the macro- and mesopores.