Methyl orange degradation over nano-LaMnO3 as a green catalyst under the mild conditions

Abstract

This study was conducted to investigate the use of cubic LaMnO3 nano-perovskite as a green catalyst for the degradation of an aqueous solution of methyl orange under different conditions. Nanoscale cubic lanthanum manganite with the particle size of ~20 nm was successfully synthesized via citrate sol-gel method. The sample was characterized using the FT-IR and UV-Vis spectroscopy, XRD, SEM, and TEM analysis. The particle size of catalyst was calculated by Scherer equation using data of XRD analysis. The calculations along with an analysis of SEM and TEM confirm the formation of nanosized perovskite phase. The behavior of this nanocatalyst for degradation of an aqueous solution of methyl orange was investigated at wavelengths of 300-700 nm. The effects of the type and different amounts of acid, the absorbent content, pH, and temperature were studied for obtaining the optimal conditions of degradation. The prepared sample shows a suitable activity for the methyl orange degradation under dark (~90%) condition. The solar catalytic degradation is faster and goes up to about 100% after 60 min, indicating a different reaction pathway with less activation energy. Pre-visible-light degradation is the basis of catalytic activity of lanthanum manganite. A parallel photocatalytic reaction, however, is an almost simpler way to destroy the azo dyes over LaMnO3 nanoperovskite, which makes the LaMnO3 as a proper photocatalyst for degradation.