Solid adsorbents, following their use for mercury removal from flue gas, that do not interfere with the ability of air-entraining additives (such as surfactants) to form stable bubbles when added to fly ash containing the adsorbents. The interference is overcome by heating the materials used in the manufacture of the adsorbent so that magnesium hydroxide and/or one or more alkali compounds containing one or more silicate, aluminate, and/or phosphate moiety, added or already present in the materials, binds multivalent cations present in the materials that could otherwise interfere with the surfactant activity.