Enhanced mineralization of pharmaceuticals by surface oxidation over mesoporous γ-Ti-Al2O3 suspension with ozone

Abstract

Titanium-doped mesoporous γ-Al2O3 (γ-Ti-Al2O3) was prepared by an evaporation-induced self-assembly method and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption, scanning electron microscope, and FTIR spectra of chemisorbed pyridine. γ-Ti-Al2O3 revealed excellent catalytic ozonation activity and stability for mineralization of six drugs in aqueous solution, including ibuprofen, sulfamethoxazole, phenytoin, diphenhydramine, diclofenac sodium and acyclovir. The characterization studies showed that titanium was incorporated into the framework of γ-Al2O3 by AlOTi linkage, locating at tetrahedrally coordinated sites, which increased the Lewis acid sites of γ-Al2O3, especially the medium acid sites. The surface atomic oxygen (Al3−*O) and peroxide species (Ti4+−*O2) were commonly generated rather than hydroxyl radical from catalytic decomposition of ozone in γ-Ti-Al2O3 suspension on the basis of the electron paramagnetic resonance (EPR) and in situ Raman measurements. Furthermore, it was verified that the high mineralization of the tested pharmaceuticals came from the surface oxidization of organic acid intermediates by the common role of the surface atomic oxygen and peroxide species.