Systems are disclosed for making and using micro-porous particulates at least partially composed of metal sulfides, particularly alkaline earth metal and transition metal sulfides, as sorbents for removal of mercury from flue gas. Calcium sulfide micro-porous powders derived from the high temperature reduction of calcium sulfate and calcium sulfite are disclosed to be reactive substrates for a group of sorbents for adsorption of mercury from coal combustion flue gases produced by the utilities industry, as well as from natural gas and gaseous and liquid hydrocarbons. The sorbents are useful for cost-effectively adsorbing elemental mercury and oxidized mercury species such as mercuric chloride from flue gases, including those containing acid gases (e.g., SO.sub.2, NO and NO.sub.2, and HCl), over a wide range of temperatures.