Effect of Zr Impregnation on Clay-Based Materials for H2O2-Assisted Photocatalytic Wet Oxidation of Winery Wastewater

Abstract

UV-activated Zr-doped composites were successfully produced through the impregnation of Zr on the crystal lattice of different clay materials by a one-step route. Fixing the amount of Zr available for dopage (4%), the influence of different supports, submitted to different chemical treatments, on the photocatalytic activity of the resulting Zr-doped pillared clay materials (PILC) was assessed. Both chemical characterization and structural characterization suggest that the immobilization of Zr on montmorillonite and PILC structures occurred through isomorphic substitution between Si and Zr in the tetrahedral sheet of the clay material. This structural change was demonstrated by significant modifications on Si-OH stretching vibrations (1016 cm−1, 1100 cm−1 and 1150 cm−1), and resulted in improved textural properties, with an increase in surface area from 8 m2/g (natural montmorillonite) to 107 m2/g after the pillaring process, and to 118 m2/g after the pillaring and Zr-doping processes ((Zr)Al-Cu-PILC). These materials were tested in the UV-photodegradation of agro-industrial wastewater (AIW), characterized by high concentrations of recalcitrant contaminants. After Zr-dopage on AlCu-PILC heterogeneous catalyst, the total organic carbon (TOC) removals of 8.9% and 10.4% were obtained through adsorption and 77% and 86% by photocatalytic oxidation, at pH 4 and 7, respectively. These results suggest a synergetic effect deriving from the combination of Zr and Cu on the photocatalytic degradation process.