The regulation of electron distribution on Fe Lewis acidic sites within silicon skeleton and its contribution to Ketoprofen ozonation

Lewis acid site was vital center for activating O-3 during catalytic ozonation process. Herein, we proposed a strategy to enhance the Lewis acid strength of Fe-MCM-48 (FeM) by fluorination. Fluorinated Fe-MCM-48 (FFeM) exhibited the better catalytic ozonation efficiency towards Ketoprofen (KET), a kind of nonsteroidal antiinflammatory drug. 87.4 % TOC removal was obtained by F2.5Fe0.8M/O-3 process, but only 27.5 % and 52.7 % were found by sole ozonation and Fe0.8M/O-3 processes, respectively. Comparative characterizations, experiments and DFT calculations showed that fluorinated FFeM was regular sphere with three dimensional duct channel and large SBET. Doping of F reduced particle size, implanted electron withdrawing Si-F group and formed the electron poor center around Fe atom, which enhanced Lewis acid strength of FFeM. Protonated hydroxyl groups on Lewis acid sites were the main active sites for O3 activation. Greater amount of O-3 were absorbed on the surface of FFeM and the greater O-3 utilization rate, center dot OH and center dot O-2 (-) generation rates were obtained by FFeM/O-3 process. Common anions such as Cl, SO42- and NO3- and Humic acids (HA) had little effect on KET removal but inhibited TOC removal in FFeM/O-3 process.center dot OH, center dot O-2(-) and Fe(IV) = O oxidation were accounted for KET degradation. 16 kinds of intermediates generated from KET degradation and 4 pathways were deduced.