Particulate matter capturing over manganese dioxides with different crystal structures
Yang Liu , Rui Liu , Huan-Huan Yang , Hao Zhou , Xianliang Yi
DOI:10.1016/j.jes.2022.06.039
Received May 25, 2022,Revised , Accepted June 28, 2022, Available online July 09, 2022
Volume 35,2023,Pages 667-677
Particulate matter (PM) is the main contributor to air pollution, and filtration has been reported to be promising for PM capturing. Considering the complexity of polluted air (volatile organic compounds (VOCs) and ozone are likely concomitant with PM particles) and in view of the versatility of MnO2 for the degradation of VOCs and ozone, the feasibility of MnO2 materials as PM filtering media was investigated in this study, and the effect of crystal structure on PM filtration was clarified. Compared with the layered δ-MnO2, the MnO2 with tunnel structure (including 1 × 2-, 2 × 2- and 3 × 3-MnO2) exhibited greatly enhanced PM removal efficiencies, and particularly, the 3 × 3-MnO2 possessed not only significant activity for adsorbing PM particles but also high utilization efficiency of the active surface. Physicochemical properties of the adsorbents were studied by XRD, ATR, isothermal N2 adsorption, SEM and (HR)TEM. The correlation between pore characteristics and particle elimination activity demonstrates that the most developed mesoporous structure of the 3 × 3-MnO2 sample played an important role in strengthening the PM adsorption capability. Further comparison of the surface properties of the fresh and spent samples reveals that with respective to the occasion of δ-MnO2, the structure of 3 × 3-MnO2 was robust enough to resist collapse after PM capturing and the great accommodation of the inorganic and organic PM substances in the voluminous pores induced strong affinity between PM particles and 3 × 3-MnO2. Thereby, a higher particle filtration ability was retained.
