preferably from about 120 to about 225 u00b0 c the heavy metal typically comprises a metal selected from the group consisting of arsenic beryllium lead cadmium chromium nickel zinc mercury barium and combinations of any two or more thereof the heavy metal most typically comprises mercury when the heavy metal is mercury the mercury is typically present in the gaseous feed stream in an amount in the range of from about 0 1 to about 10 000 u03bcg m 3 more typically in the range of from about 1 to about 800 u03bcg m 3 and most typically from about 3 to about 700 u03bcg m 3 the composition preferably converts at least a portion of the heavy metal in the gaseous feed stream to an elevated oxidation state in the case of mercury the composition preferably converts at least a portion of the mercury contained in the gaseous feed stream from a zero oxidation state to a 1 or a 2 oxidation state and also preferably removes mercury u201c at least a portion u201d as used in this paragraph can mean at least 20 weight preferably at least 30 weight and more preferably at least 50 weight mercury based on the total amount of mercury contained in the gaseous feed stream the gaseous product stream preferably contains less than about 20 weight more preferably less than about 10 weight and most preferably less than about 5 weight of the mercury contained in the gaseous feed stream the gaseous product stream is optionally contacted with a separate adsorbent in an adsorption zone the adsorbent can be any adsorbent capable of adsorbing a heavy metal more preferably the adsorbent comprises consists of or consists essentially of a material selected.