Facile regulation of Lewis sites and 3D mesoporous channel within Ce-SBA-15 for catalytic ozonation of clofibric acid

Abstract

The traditional 2D channel of SBA-15 was not favor for the mass transfer and Lewis sites exposures, which restrained its application in catalytic ozonation. Herein, we proposed a facile hydrothermal method for simultaneously regulating pore structure (from 2D to 3D channel) and introducing Ce-based Lewis sites within Ce-SBA-15 with urea (named as Ce-SBA-U) as pH-regulator. pH ascension induced by urea during hydrothermal and phase transition process could weaken the electrostatic interaction between inorganic silicate and surfactant molecules as well as slowed down the hydrolysis and condensation rates of silane, which facilitated the doping of cerium, enlargement of mesoporous sizes and formation of 3D mesoporous channel. Mesoporous sizes of Ce-SBA-U was manipulated by urea dosage and could be enlarged to more than 20 nm, which favored for the mass transfer of ozone and its further activation on Ce(III)-based Lewis sites. The redox cycle of Ce(III)/Ce(IV) could donate electron for surface bonded O3 for the generation of hydroxyl radicals (•OH), superoxide radical (O2•−) and singlet oxygen (1O2). Benefiting from the above features, Ce-SBA-U/O3 process achieved 98.1% clofibric acid (CA) removal and 35.4% TOC removal, which were far beyond those of sole ozonation and Ce-SBA-15/O3 processes. The involved mechanism together with the degradation pathways were exploited by comparative characterizations and experiments. This work could broaden the application of SBA-15 in catalytic ozonation.