Preparation of highly active zinc oxide for photocatalytic removal of phenol: direct calcination versus co-precipitation method

Abstract

Photocatalytic removal of phenol under UV light irradiation was studied on zinc oxide (ZnO) photocatalysts, which were prepared via direct calcination (DC), and co-precipitation (CP) methods. The XRD patterns revealed that all of the prepared ZnO samples showed wurtzite structure, in which the ZnO-CP showed higher intensity of the diffraction peaks than the ZnO-DC sample. Optical and fluorescence properties of the prepared ZnO samples were similar to each other as confirmed by DR UV-Vis and fluorescence spectroscopy, respectively. The Stern-Volmer plot was investigated to study the interactions between the emission sites and the phenol. It was obtained that the emission sites of the ZnO-CP gave better interactions towards phenol molecules as compared to the ZnO-DC. After 6 hours reaction under UV light irradiation, the ZnO-CP sample showed two times higher photocatalytic activity for removal of phenol (10%) than that of the ZnO-DC (5%). It was suggested that the high activity observed on the ZnO-CP sample would be due to high crystallinity and good interactions with phenol. These results clearly suggested that the co-precipitation method was a good approach to prepare the highly active ZnO for the photocatalytic removal of phenol.