Synthesis of Manganese Dioxide/Reduced Graphene Oxide Nanocomposite for Oxidative Degradation of Methylene Blue

Abstract

Dyes are serious environmental contaminants having negative effects on human health. Due to the tenacity and resilience of dyes to natural degradation, the careless dumping of wastewater containing azo dyes has turned into a significant environmental problem. Researchers have focused their efforts and made substantial attempts to address this problem since dyes cannot be removed from the environment by standard wastewater treatment procedures. Manganese dioxide (MnO2) – reduced graphene oxide (rGO) nanocomposite was synthesized by using KMnO4 and rGO. MnO2-rGO nanocomposite was used as a model for the efficient removal of methylene blue (MB) from an aqueous medium. The nanocomposite obtained was characterized by Fourier transforms infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. The effect of pH, dosage of the nanocomposite, MB initial concentration, and reusability of nanocomposite were studied. MnO2–rGO nanocomposite showed high performance for oxidative decolorization and removal of MB. Typically, 25 mL of MB (10 ppm) can be decolorized in 15 min with 25 mg of the MnO2–rGO nanocomposite with 98% decolorization efficiency. The optimum pH is 7 for MnO2-rGO nanocomposite. Moreover, the dye decolorization rate was decreased with increasing MB concentration. The Pseudo-second-order model (R2 = 0.9958) was the applicable kinetic model. The nanocomposite material exhibited recyclability and durability with the degradation value of 76% for MB after three consecutive cycles. Results revealed that the MnO2-rGO nanocomposite is capable of successfully degrading MB in aqueous solutions.