Application of Zirconia/Alumina Composite Oxide Ceramics as Photocatalysts for Removal of 2,4,6-Trichlorophenol from Water

Abstract

The mesoporous zirconia/alumina composites were synthesized via a sol–gel method, followed by heat treatment at 500 °C for 5 h. The effect of the ZrO2/Al2O3 ratio on the structural and textural properties of the obtained composites was explored. Sorption analysis has confirmed that all samples have a mesoporous structure whose parameters (SBET, Vp and Dmax) strongly depend on the ZrO2/Al2O3 ratio. The XRD pattern of composites has shown that the addition of zirconia disrupts the crystallinity of alumina. The composites with higher zirconia content (50% ZrO2 and 67% ZrO2) are characterized by peaks related only to the zirconia phase. UV/Vis diffuse reflection spectra of all samples revealed that composites have more intensive absorption compared to pure oxides for wavelengths larger than 250 nm and similar band gaps. Photoluminescence measurements showed presence of defects in all samples, which are responsible for photocatalytic activity. All samples showed significant adsorption/photocatalytic efficacy for the removal/degradation of 2,4,6 -trichlorophenol (TCP). Results obtained using HPLC and TOC techniques showed that between 70 and 80% of the initial TCP concentration was removed/degraded after 4 h of illumination. These results were corelated with flat, conduction and valence band potentials of synthesized pure and binary oxides, calculated using Mott–Schottky plots.