Manipulating catalytic activity and durability of Pt-modified Cu–Fe–La/γ-Al2O3 ternary catalyst for catalytic wet air oxidation: effect of calcination temperature

Abstract

A series of novel Pt-modified Cu–Fe–La/γ-Al₂O₃ catalysts were prepared by an incipient-wetness impregnation method, and their performances were evaluated in catalytic wet air oxidation (CWAO) of printing and dyeing wastewater (PDW). The as-prepared catalysts were characterized by X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy, and temperature programmed reduction by hydrogen (H₂-TPR). The effects of catalyst composition and calcination temperature on the catalytic performance were investigated. The chemical oxygen demand (COD) removal efficiency and decolorization rate are satisfactory over Cu_1.5Fe_1.5La₃/γ-Al₂O₃ catalyst, with poor stability under CWAO conditions. In contrast, catalytic performance and stability of all Pt-modified catalysts are significantly improved. With increasing calcination temperatures from 350 °C to 750 °C, the activity of the catalysts significantly decreases from 97.3% to 84.6%, and the size of the particles varies from 4.71–6.95 nm. The XRD, HRTEM, and XPS results indicate that the Pt₁Cu₁Fe₁La₃/γ-Al₂O₃ catalyst mostly comprises Pt, CuO, Fe₃O₄, and La₂O₃, and the incorporation of Pt increases the binding energies (BEs) of the metal elements in the catalyst, owing to synergistic interactions between the Pt and the Cu, Fe, and La elements. After five cycles, the COD removal efficiency and decolorization rate for PDW over the Pt₁Cu₁Fe₁La₃/γ-Al₂O₃ catalyst calcined at 650 °C remain comparable with the fresh catalyst, indicating that Pt-modified Cu–Fe–La/γ-Al₂O₃ ternary oxide is a promising catalyst with high activity and stability for CWAO treatment.