In situ synthesis of MnO2-loaded biocomposite based on microcrystalline cellulose for Pb2+ removal from wastewater

Abstract

We fabricated a new MnO2-loaded biocomposite based on microcrystalline cellulose (MCC–MnO2) by an in situ synthesis method and investigated its adsorption behavior and mechanism for Pb2+ removal from aqueous medium. As-prepared MCC–MnO2 was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analyses. The effects of pH value, initial Pb2+ concentration, contact time, and solution temperature on the uptake of Pb2+ onto MCC–MnO2 were investigated using a batch system. Adsorption equilibrium could be achieved in 3 h for various studied initial concentrations, and a pseudo-second-order model could fit the adsorption behavior well. The equilibrium data could be well described by the Langmuir isotherm model, and the maximum monolayer adsorption capacity of MCC–MnO2 (with 7.98% MnO2 loading) for Pb2+ was estimated to be 247.5 mg/g at 313 K. Thermodynamic studies indicated a spontaneous and endothermic adsorption process. X-ray photoelectron spectroscopy (XPS) was used to analyze the adsorption mechanism, revealing that the chemical speciation of Pb2+ on MCC–MnO2 was similar to the compound PbO. Moreover, no variations in the valence of Mn were observed after adsorbing Pb2+. The regeneration study showed that the adsorption capacity retained about 89.6% of its initial value at the fifth sequential regeneration cycle, indicating that this material is an efficient and renewable hybrid adsorbent for Pb2+ removal.