Microporous assembly of MnO2 nanosheets for malachite green degradation

Abstract Porous assembly of MnO 2 nanosheets has been prepared via a simple redox co-precipitation method using Mn(OAc) 2 and KMnO 4 . The material has been characterized by XRD, XPS, FESEM, TEM, FTIR, and N 2 -adsorption–desorption analyses. The as-prepared MnO 2 nanomaterial is microporous (average pore diameter: 0.8 nm; surface area: 162 m 2 /g) and poorly crystalline. The TEM and SEM images reveal the formation of spherical assembly of fine nanosheets. The oxidation state of manganese is determined by XPS analysis. The porous nature and the oxidizing property of the nano MnO 2 has been exploited for MG degradation in aqueous media under ambient condition. The effects of various parameters (such as pH, MnO 2 dose, initial MG concentration, air/O 2 , and organic acids) on MG degradation are evaluated. The mineralization of MG is monitored through TOC analyses. About 99% decolorization and ∼44% mineralization of MG (conc.: 50 mg/L) is achieved in 120 min with MnO 2 (dose: 0.5 g/L). The decolorization follows first order kinetics. During the oxidative degradation, slight leaching of Mn 2+ is observed. The reusability of the material has been shown for three consecutive cycles with good performance.