Synthesis of CeO2-modified activated carbon spheres by grafting and coordinating reactions for elemental mercury removal

摘要

Series of resin-based activated carbon spheres with well-dispersed CeO2 particles inside and high surface area were successfully prepared by the grafting of MMA and coordinating reactions of cerium(III) nitrate salt and steam activation. N-2 adsorption isotherms, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction-meter and X-ray photoelectron spectroscopy were applied to study the textural and surface characteristics of the obtained activated carbon spheres, and the Hg-0 removal performances were evaluated in a fixed bed reactor. The experimental results indicated that pore structure, surface chemical properties and Hg-0 removal ability of activated carbon spheres were observably improved after the modification of grafting and coordinating reactions. The optimal cerium(III) nitrate loading value, reaction temperature and O-2 content were 7%, 150 degrees C and 5%, respectively. Moreover, SO2 showed an obvious inhibitory effect on the Hg-0 removal efficiency in the absence of O-2, while it facilitated the Hg-0 removal in the presence of O-2. Nitrogen monoxide promoted the Hg-0 removal with or without O-2, while water vapor inhibited the Hg-0 removal over ACS-M-7%Ce. In addition, both of stable removal performance and excellent recycling ability were shown for ACS-M-7%Ce in ten cycles. The Hg-0 removal mechanism analysis indicated that introduced CeO2 significantly promoted the Hg-0 removal ability of ACS-M-7%Ce by generating the active species (such as C=O or C-O) and the lattice oxygen through the Ce4+/Ce3+ redox couple, and catalytically oxidized Hg-0 into HgO.