A method for treating powdered activated carbon (PAC) and/or coal combustion residues (CCRs) by heating at least one of a spent PAC and/or a CCR to separate at least one heavy metal from the at least one of the spent PAC and/or the CCR to create a clean stream and a heavy metal stream, combining the heavy metal stream with a water soluble alkaline-earth metal sulfide to create a combined stream, and removing at least a portion of the at least one heavy metal from the combined stream. The heating may further include heating the at least one of the spent PAC and/or the CCR in an inert atmosphere. Further, the combining may include combining the heavy metal stream with the water soluble alkaline-earth metal sulfide and a catalyst and/or a surfactant or hyperdispersant.