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Abstract: Cerium-doped MCM-41 (Ce-MCM-41) was prepared by a hydrothermal method and its catalytic activity for ozonation of p-chlorobenzoic acid (p-CBA) in aqueous solution was studied. For comparison, cerium-loaded MCM-41 (Ce/MCM-41) was prepared by a dipping method. Ce-MCM-41 was characterized by the low and wide angle X-ray powder diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM) and ultraviolet–visible diffuse reflection spectrum (UV–vis DRS). The results showed that the material retained the highly ordered mesopore structure of MCM-41 and had a surface area of 852m2 g−1. Cerium was incorporated into the framework of MCM-41, locating at tetrahedrally coordinated sites. The cerium doping content, initial pH of aqueous solution and reaction temperature played important roles in catalytic ozonation of p-CBA. Under the chosen conditions (1.39mgl−1 ozone dosage, 10mgl−1 p-CBA solution and 1gl−1 catalyst dosage), the high mineralization rate (86%) was achieved by Ce-MCM-41/O3 process at 60min reaction time, only 52% by O3 alone. The combination of Ce-MCM-41 and O3 exhibited a significant synergetic effect. Ce-MCM-41 showed the better activity and stability than cerium-loaded MCM-41(Ce/MCM-41) during catalytic ozonation of p-CBA, its cerium leaching was greatly reduced (only 0.085mgl−1) and below detection limit after being reused, compared with that of Ce/MCM-41 (0.44mgl−1) with the presence of the same theoretical cerium content. TOC removal rate slightly decreased from 86% to 81% and kept stable after Ce-MCM-41 being re-utilized two times, which illustrated that Ce-MCM-41 was a kind of promising catalyst for ozonation of p-CBA. The addition of Ce-MCM-41 significantly improved ozone decomposition into HOus solution and reduced ozone concentration in equilibrium. [Copyright &y& Elsevier]

Comparative experiments were conducted to investigate the catalytic ability of MnO x /SBA-15 for the ozonation of clofibric acid (CA) and its reaction mechanism. Compared with ozonation alone, the degradation of CA was barely enhanced, while the removal of TOC was significantly improved by catalytic ozonation (O 3 /MnO x /SBA-15). Adsorption of CA and its intermediates by MnO x /SBA-15 was proved unimportant in O 3 /MnO x /SBA-15 due to the insignificant adsorption of CA and little TOC variation after ceasing ozone in stopped-flow experiment. The more remarkably inhibition effect of sodium bisulfite (NaHSO 3 ) on the removal of TOC in catalytic ozonation than in ozonation alone elucidated that MnO x /SBA-15 facilitated the generation of hydroxyl radicals ( OH), which was further verified by electron spin-resonance spectroscopy (ESR). Highly dispersed MnO x on SBA-15 were believed to be the main active component in MnO x /SBA-15. Some intermediates were indentified and different degradation routes of CA were proposed in both ozonation alone and catalytic ozonation. The amounts of small molecular carboxylic acids (i.e., formic acid (FA), acetic acid (AA) and oxalic acid (OA)) generated in catalytic ozonation were lower than in ozonation alone, resulting from the generation of more OH. [ABSTRACT FROM AUTHOR]