Preparation of highly active and SO2-resistant Cr-based non-carbon adsorbents via plasma for elemental mercury removal

Coal-fired mercury pollution poses an escalating threat to the ecosystem and human health. In this study, we designed and prepared transition metal oxides (MO x ) supported non-carbon-based adsorbents for Hg 0 removal using non-thermal plasma, based on the mechanism of Hg 0 removal. Specifically, MO x supported SiO 2 adsorbents were examined to explore the correlation between their redox ability and Hg 0 removal. The plasma treatment process could enhance the catalytic oxidation activity of the MO x (oxygen activation center) and effectively enhance Hg 0 removal efficiency. The Hg 0 removal efficiencies of Co 3 O 4 /SiO 2 -P and CrO x /SiO 2 -P prepared by plasma could maintain above 95.0 % and 85.0 % in the whole test, whereas the Co 3 O 4 /SiO 2 and CrO x /SiO 2 adsorbents prepared by traditional incipient wetness impregnation method exhibited lower Hg 0 removal efficiencies of nearly 20–30 %. Furthermore, with the addition of SO 2 , the Hg 0 removal performance of Co 3 O 4 /SiO 2 -P decreased significantly, while the performance of CrO x /SiO 2 -P remained relatively unchanged. Characterization results containing X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the oxygen activation centers on CrO x /SiO 2 -P exhibited excellent resistance to SO 2 and were less susceptible to SO 2 occupation than those on Co 3 O 4 /SiO 2 -P. The plasma-prepared CrO x /SiO 2 -P adsorbents demonstrate promising potential for industrial applications in Hg 0 removal.