Impregnating filter media such as granular activated carbon or activated alumina with a reactive chemical or a catalyst can convert the adsorbed contaminants to less odorous compounds. For example, an air filter medium consisting of activated alumina and potassium permanganate can remove odorous hydrogen sulfide, mercaptans, and other sulfur contaminants. Another approach, patented by Turk and Brassey, can remove hydrogen sulfide from oxygen containing gas. The process involves adding ammonia to the air stream containing hydrogen sulfide prior to its passage through activated carbon. The ammonia catalyzes the oxidation of hydrogen sulfide to elemental sulfur. Impregnating activated carbon with sodium or potassium hydroxide can also neutralize hy drogen sulfide and form elemental sulfur. Both the ammonia/granular activated carbon system and the caustic/granular activated carbon system perform better than unimpregnated carbon.
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