Glycogen-assisted biosynthesis of MnO2 for adsorptive elimination of methylene blue from water

•MnO2 NPs were successfully biosynthesized via glycogen oxidation by KMnO4.•MnO2 NPs were able to 95 % remove of methylene blue dye in 30 min.•The equilibrium data were consistent with the Langmuir isotherm model.•The adsorption rate followed the pseudo-second-order kinetic model.•The adsorption process was endothermic, spontaneous and physisorption. A novel biosynthesis of manganese dioxide (MnO2) NPs was achieved by oxidizing glycogen with KMnO4 in an alkaline medium. X-ray powder diffraction, Fourier-transform infrared spectroscopy, N2 sorption, and transmission electron microscope (TEM) techniques were utilized to assess the physicochemical characteristics of the prepared MnO2. The impacts of different adsorption parameters, including contact time, pH, concentration, temperature, and adsorbent dose, on methylene blue (MB) elimination utilizing the prepared MnO2 NPs, were investigated. It was found that the Langmuir model well describes how the dye molecules arrange themselves on the MnO2 surface compared to other models. This proposes a single layer of dye forms, with each molecule attaching to a specific site on the MnO2. Additionally, the results were well-matched with a pseudo-2nd-order model, demonstrating that chemical reactions had a significant role in the adsorption experiment. Under specific conditions (RT, natural pH of the dye solution, and 30-minute contact time), the MnO2 could hold up to 40.85 mg of dye per gram of MnO2 (mg/g). Further analysis reflected that the adsorption procedure was spontaneous, which means it happened favorably without needing extra energy input. This suggests that biosynthesized MnO2 has great potential as an eco-friendly material for cleaning up MB dye contamination in water.