MnO₂-decorated rGO: a functional material for Congo Red dye removal

Metal oxide nanostructures functionalized with carbonaceous nanomaterials, notably graphene oxide and reduced graphene oxide have drawn the rising interest of researchers for environmental remediation. Consequently, this study was designed to fabricate MnO₂-GO and MnO₂-rGO nanocomposites as photocatalysts and evaluate their photo-assisted removal capability of Congo Red (CR) dye. The MnO₂-GO and MnO₂-rGO nanocomposites was fabricated by a one-pot simple approach and characterized for its crystallinity, morphology, composition, functional groups, thermal stability, and optical properties via the selected techniques. Furthermore, the photo-assisted removal capability of the as-prepared nanomaterials was assessed to eliminate CR dye from wastewater. MnO₂-rGO revealed a higher photo-assisted removal performance (92%) compared to MnO₂-GO (87%) and pure MnO₂ (82%) using 0.1 g of catalyst for a 100 mg/L CR dye solution over 80 minutes under UV light, at 40°C, and pH 5. The kinetics results reveal that the photo-assisted process of Congo Red dye followed the pseudo-second-order kinetic model, and the thermodynamic data (ΔS, ΔG, and ΔH) confirmed the increased randomness, feasibility, spontaneity, and endothermic nature of the CR dye. This work highlights the effectiveness of MnO₂-GO and MnO₂-rGO nanocomposites for both adsorptive and photocatalytic environmental remediation.