Fe-MCM-48 catalyst with a three-dimensional cubic pore structure was directly synthesized via a hydrothermal method, and the mineralization efficiency of diclofenac (DCF) in the catalytic ozonation process (Fe-MCM-48/O 3 ) was assessed. X-ray diffraction (XRD), N 2 adsorption desorption, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) characterizations revealed that Fe existed in the framework of MCM-48, and Fe-MCM-48 possessed a large surface area and a highly ordered cubic mesoporous structure, which could accelerate reactants and products diffusion. Regarding mineralization efficiency, the addition of Fe-MCM-48 significantly improved total organic carbon (TOC) removal, and approximately 49.9% TOC were removed through the Fe-MCM-48/O 3 process at 60 min, which was 2.0 times higher than that in single ozonation. Due to this catalyst's superior structure, Fe-MCM-48 showed the better catalytic activity compared with Fe-MCM-41 and Fe loaded MCM-48 (Fe/MCM-48, Fe existed on the surface of MCM-48). DCF removal in the Fe-MCM-48/O 3 process was primarily based on ozone direct oxidation. The improvement of mineralization efficiency was attributed to the function of generated hydroxyl radicals (•OH), which indicated that the presence of Fe-MCM-48 accelerated ozone decomposition . Moreover, the negatively charged surface of Fe-MCM-48 and the proper pH value of the DCF solution played an essential role in OH generation.
Weirui Chen,Muxin Lin,Jiaxin Zhou,Xukai Li,Xipeng Wei,Gaozu Liao,Jing Wang,Laisheng Li
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 anti-inflammatory drug. 87.4 % TOC removal was obtained by F 2.5 Fe 0.8 M/O 3 process, but only 27.5 % and 52.7 % were found by sole ozonation and Fe 0.8 M/O 3 processes, respectively. Comparative characterizations, experiments and DFT calculations showed that fluorinated FFeM was regular sphere with three dimensional duct channel and large S BET . 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 O 3 activation. Greater amount of O 3 were absorbed on the surface of FFeM and the greater O 3 utilization rate, •OH and •O 2 – generation rates were obtained by FFeM/O 3 process. Common anions such as Cl − , SO 4 2− and NO 3 – and Humic acids (HA) had little effect on KET removal but inhibited TOC removal in FFeM/O 3 process. •OH, •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.
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