The adsorption of Ha and NOX on gasifier and combustion by-products was investigated. Carbon-rich fractions were produced by a density separation technique from a gasifier char (GC) and a pulverized coal combustion blended fly/bottom ash (CC) recovered from a pond. Both fractions were subjected to steam activation at 875 degrees C. As-received and activated chars and two commercial carbons developed specifically for Ha and NOX adsorption were tested and compared for Hg and NOx adsorption capacities. The Hg adsorption capacity of GC was found as good as a specialty commercial carbon designed for Hg capture from flue gases. Steam activation or heating to 900 degrees C destroyed GC's adsorption capability. GC adsorbed one-third of the NOX uptake of a commercial carbon used for NOX adsorption. Hg-laden GC captured even more NOX than the as-received GC. Possible explanations for the performance of GC will be discussed. The CC material was a poor performer for both Hg and NOx capture. (c) 2005 Elsevier Ltd. All rights reserved.