Multipollutant removal of Hg⁰/SO₂/NO from simulated coal-combustion flue gases using metal oxide/mesoporous SiO₂ composites

This study investigated the multipollutant control effectiveness for Hg⁰/SO₂/NO using V, Mn, and Cu oxides/mesoporous SiO₂ particulate composites. The presence of metal oxides decreased the specific surface area and pore volume and altered the surface morphology and sizes of the raw SiO₂ particles. V^4 +/V^5 +, Mn^4 +, and Cu⁺/Cu^2 + were the major valence states in the VO_x, MnO_x, and CuO_x/SiO₂ composites, respectively. Amorphous and highly dispersed metal oxides presenting in the SiO₂ composites was confirmed by the X-ray diffraction characteristic peaks. Multipollutant control of Hg⁰ and NO using the metal oxide/SiO₂ composites was achieved at both 150 and 350 °C under the simulated coal-combustion flue gas condition. CuO_x/SiO₂ with > 40% Hg⁰ removal at 350 °C further implies that strong chemical bonds could form between Hg species and the surface groups of CuO_x/SiO₂. The metal oxide/SiO₂ composites had up to 62% NO removal enhancement with injection of NH₃ at 350 °C, indicating the effectiveness of catalytic reduction of NO. The CuO_x/SiO₂ composite showed the greatest Hg⁰ and NO removal performance, which may stem from the presence of active CuO_x in high content and its large surface area and mesoporosity.