High surface area mesoporous nanocast LaMO 3 (M = Mn, Fe) perovskites for efficient catalytic ozonation and an insight into probable catalytic mechanism

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Applied Catalysis B: Environmental, ISSN: 0926-3373, Vol: 206, Page: 692-703

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Shahzad Afzal; Xie Quan; Jianlin Zhang
Elsevier BV
Chemical Engineering; Environmental Science
article description
Mesoporous nanocast perovskites (NC-LaMnO 3 and NC-LaFeO 3 ) were synthesized by nanocasting technique using SBA-15 as a template and for the first time they were used in catalytic ozonation of 2-chlorophenol. For the purpose of comparison, uncast counterpart perovskites (CA-LaMnO 3 and CA-LaFeO 3 ) as well as Mn 3 O 4 and Fe 2 O 3 were also prepared by conventional citric acid assisted route. Nanocast perovskites possessed high specific surface area and large pore dimensions than uncast perovskites. Catalytic activity in terms of TOC removal followed the order of NC-LaMnO 3 > NC-LaFeO 3 > CA-LaMnO 3 > CA-LaFeO 3 > Mn 3 O 4 > Fe 2 O 3 > O 3 with 80, 68, 50, 43, 39, 33% and 25% respectively. A detailed study is conducted to discuss the mechanism of catalytic ozonation of selected NC-LaMnO 3 perovskite by using organic and inorganic hydroxyl radical’s quenchers, FTIR, florescence spectroscopy, EPR, ATR-FTIR, XPS, LSV, H 2 O 2 detection, Raman spectroscopy, TPR-H 2, R ct value calculation, ozone utilization efficiency and ozone decomposition. It was found that hydroxyl radicals rather than surface peroxide, surface atomic oxygen, superoxide and singlet oxygen were the reactive oxygen species contributed to high catalytic activity. Moreover, high surface area as well as open porous structure of nanocast perovskites were believed to enhance the catalytic activity by surface reaction and easy access of reactants to the active sites.