Evaluation of hydrotalcite-like compounds with distinct interlaminar anions as catalyst precursors in methylene blue photodegradation

Abstract

In this work, two hydrotalcite like-compounds with nitrate and acetate as interlaminar anions (uncalcined and calcined) were evaluated as catalysts in the photodegradation of methylene blue (MB) under visible light irradiation. Materials were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis, Scanning Electron Microscopy and Diffuse Reflectance Spectroscopy. The XRD analysis of the pristine compounds demonstrated that they exhibited the characteristic reflections of hydrotalcite-like compounds as the main crystalline phase. The analysis of the (003) reflection confirmed nitrate or acetate presence in the interlaminar region. However, after annealing spinel and MgO obtaining at 350°C was evidenced in both materials. Major absorbance intensity in the visible region was observed in the acetate-containing samples and the highest MB decomposition was achieved with the acetate precursor sample calcined at 450°C. The photocatalytic activity was attributed to a synergy between the crystalline phases, specific surface area and the band gap energy.