RGO-stabilized MnO/N-doped carbon nanofibers for efficient removal of Pb(II) ion and catalytic degradation of methylene blue

Abstract

rGO-MnO/NC nanocomposites with porous structure were prepared by one-pot solvothermal method combining with heat treatment. rGO nanosheets can serve as a substrate to prevent the irreversible fusion and aggregation during the high-temperature pyrolysis of Mn-precursor; meanwhile, the organic ligands in the precursor can provide N and C source, resulting in rGO-stabilized MnO/N-doped carbon nanofibers (rGO-MnO/NC). This study investigated the adsorption behaviors of Pb(II) ions onto rGO-MnO/NC under different rGO loading in composites, pH value and temperature of solution. The rGO-MnO/NC nanocomposites exhibited an enhanced performance for removal of Pb(II) ions as compared with pure MnO/NC. The adsorption isotherm of Pb(II) ions onto pure MnO/NC and rGO-MnO/NC were well fitted by Langmuir model, and the adsorption kinetics of Pb(II) ions onto rGO-MnO/NC was well described by pseudo-second-order model. The theoretical maximum adsorption capacity of Pb(II) onto rGO-MnO/NC-2 with 5 wt% rGO loading was 222.2 mg g−1 at 25 °C without adjusting solutions pH value. Furthermore, the rGO-MnO/NC-2 showed higher catalytic activity in Fenton-like oxidation of methylene blue than bare MnO/NC. The rGO-MnO/NC-2 catalyst achieved high removal of methylene blue (100% removal within 30 min) at the selected operating conditions (0.4 g catalyst L−1, [H2O2]:[MB] of 31.2 (mol/mol), 25 °C). The results suggest that the rGO-MnO/NC with suitable rGO loading could provide a promising option for effective decontamination and detoxification of heavy metal and organic dye wastewater.