Synthesis of cerium-doped MCM-41 for ozonation of p-chlorobenzoic acid in aqueous solution

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 852 m(2) 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 (1.39 mg l(-1) ozone dosage, 10 mg l(-1) p-CBA solution and 1 g l(-1) catalyst dosage), the high mineralization rate (86%) was achieved by Ce-MCM-41/O-3 process at 60 min reaction time, only 52% by O-3 alone. The combination of Ce-MCM-41 and O-3 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 0.085 mg l(-1)) and below detection limit after being reused, compared with that of Ce/MCM-41 (0.44 mg l(-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 HO center dot in aqueous solution and reduced ozone concentration in equilibrium. (C) 2012 Elsevier B.V. All rights reserved.