2,4-Dichlorophenoxyacetic acid (2,4-D) photodegradation using an Mn+/ZrO2 photocatalyst: XPS, UV–vis, XRD characterization

Abstract Zirconium oxide materials doped with transition metals (Mn, Fe, Co, Ni and Cu) were synthesized using sol–gel methods. The powders, which were obtained, were characterized by XPS, XRD, UV–vis spectroscopy and nitrogen adsorption. The photodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D), a herbicide used in agricultural applications, was used as a test reaction to study the activity of the compounds synthesized. Photodegradation studies were performed using a lamp radiating light with a UV wavelength of 254 nm. Characterization studies showed a predominance of the tetragonal phase of zirconium oxide for all of the samples studied. The values obtained for the forbidden energy level Eg fall in a range between 3.6 and 5.5 eV. BET surface areas were found to be in a range between 55 and 80 m2/g. The concentration of the metals is small and in the case of Ni it could not be detected. Samples calcined at 400 °C used in the photocatalytic study showed the highest activity. Mn/ZrO2 was the most active photocatalyst used. A 70% conversion of 2,4-D was obtained in the first hour. This can be compared to a conversion of only 30% in the absence of Mn/ZrO2.