Review and Perspectives of Mercury Removal by Spinel Compounds

Abstract

Several preparation methods for current spinel compounds are briefly introduced. The effects of temperature and flue gas components on the removal of Hg 0 over spinel compounds are reviewed. The reaction processes and mechanisms of Hg 0 adsorption, oxidation, and desorption on the surface of spinel compounds are analyzed deeply. The current methods for improving Hg 0 catalytic oxidation performance by spinel-based photocatalytic materials are also introduced. There are two main types of spinel compounds for Hg 0 removal: conventional spinel and loaded spinel compounds. Loaded spinel compounds are favorable for the adsorption and oxidation of Hg 0 due to more active sites and a larger surface area than ordinary spinel compounds. Both O 2 and HCl contribute to Hg 0 removal with Hg 0 oxidation efficiency being sensitive to both O 2 and HCl concentrations. The presence of SO 2 has a detrimental effect on the removal of Hg 0 due to the competition for the active adsorption sites on the surface of catalysts and adsorbents. The impact of temperature is bidirectional, and an optimum temperature exists. Based on the analysis of three stages (adsorption, oxidation, and desorption) included in the Hg 0 catalytic oxidation process, it was discovered that for most catalysts the Hg 0 oxidation process is the rate-limiting step for the reaction.

Enhancement of Elemental Mercury Oxidation by Core–Shell CuCo2O4@SiO2 Oxygen Carrier with Strong Oxygen Release and Weak Adsorption Capacity in Chemical-Looping Combustion

“…CuO has the strongest oxygen release capacity, but CuO is prone to sintering at high temperatures, agglomeration after reduction, and thus has poor recycling performance . In recent years, spinel (AB 2 X 4 ) oxides have been continuously applied in several research fields, such as energy storage and environmental treatment, due to their magnetic property, high catalytic activity, and good chemical stability. − A series of spinel oxides have also been widely used as oxygen carriers in CLC processes due to the synergistic effect of their complex metal oxides. − Among the spinel-type oxides, cobalt-based spinel oxides have good activity, low cost, high stability, and environmental benefits. − CuCo 2 O 4 , constructed by replacing Co 2+ in the tetrahedral position in Co 3 O 4 with Cu 2+ , is a typical spinel structure. , At 900 °C, the mercury removal efficiency of CuCo 2 O 4 is 16% higher than that of Co 3 O 4 , and it reaches the maximum mercury removal efficiency faster (as shown in Figure S1). CuCo 2 O 4 has better oxygen release properties than Co 3 O 4 and can further improve the oxidation of mercury in the fuel reactor.…”