Graphene enhanced Mn-Ce binary metal oxides for catalytic oxidation and adsorption of elemental mercury from coal-fired flue gas

Graphene was used for the enhancement of gaseous elemental mercury (Hg-0) catalytic oxidation and adsorption over Mn-based oxides. A series of graphene modified Mn-based and Ce-Mn-based oxides were prepared via a hydrothermal method. Experimental results indicated that Mn-Ce@rGO composite has a Hg-0 removal efficiency of 91% at 250 degrees C which was higher than that or pure MnOx and MnOx@rGO under the same reaction conditions. Hg-0 removal efficiency decreased in the absence of O-2. The higher SO2 concentration and space velocity resulted in lower Hg-0 removal efficiencies. The mechanism study indicated that high valances of Mn4+ and Mn3+ benefit the Hg-0 oxidation and the surface oxygen participated in the Hg-0 oxidation process. CeO2 supplies sufficient oxygen for mercury surface adsorption. During these processes, graphene-enhanced the catalytic oxidation and adsorption processes through supporting more reaction space, facilitating electron transfer and binding sites. Moreover, the spent materials can be regenerated using a simple thermal-desorption method. Mn-Ce@rGO composite was proved to be a prospective adsorbent for Hg-0 removal from coal-fired flue gas.