NOVELTY - Adsorbent composition comprises: powdered activated carbon having a mean particle size (d50) of less than or equal to 20-25 mu ; and at least one separate alkaline component including sodium bicarbonate, sodium carbonate, ammonium carbonate, ammonium bicarbonate, potassium carbonate, potassium bicarbonate, trisodium hydrogendicarbonate dihydrate, magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, calcium bicarbonate or calcium carbonate, dispersed on the activated carbon.    USE - The adsorbent composition is useful for removing mercury from a flue gas stream (claimed) generated during the combustion of fossil fuels e.g. coal, or the combustion of solid wastes.    ADVANTAGE - The adsorbent composition: removes mercury from a flue gas stream with a high efficiency in low-halogen species concentration environments, and in high sulfur species environments; lowers the impact of the sorbent on the properties of the fly ash in terms of its foaming index; has much finer particle size compared to standard commercial powdered activated carbon, and thus has high mercury capturing ability, and can be easily re-dispersed when injected into a flue gas without having the need to provide extra energy for re-dispersion; and can be prepared in a simple and cost effective manner.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) an adsorbent composition comprising: the powdered activated carbon; and a separate flow agent dispersed on the activated carbon; (2) an adsorbent composition comprising powdered activated carbon containing a separate chemical component dispersed on the activated carbon, that undergoes an endothermic decomposition at flue gas temperatures below 1100 degrees F; (3) an adsorbent composition comprising: dry powdered activated carbon having a mean particle size (d50) of less than or equal to 20-25 mu ; and a separate chemical component dispersed on the activated carbon, where the component comprises a hydrophobic portion that is coupled to the activated carbon and a hydrophilic portion that increases stability in a water-based medium; and (4) removing mercury from flue gas resulting from combustion, in which the flue gas is passed through a particle separator, comprising: injecting powdered activated carbon into the flue gas at at least one location before the flue gas reaches the particle separator; and injecting a sacrificial agent into the flue gas at at least one location before the flue gas reaches the particle separator, where the sacrificial agent is organic compound having sulfonate, carboxylate or amino functional groups including sodium methyl naphthalene sulfonate, phenyl glycol ethers, poly-naphthalene sulfonate, sodium/calcium ligno sulfonate, Aerosol OS (RTM: Sodium diisopropyl naphthalene sulfonate), salts of alkyl naphthalene sulfonates or ethylene glycol phenyl ether.