Adsorption of methylene blue on modified electrolytic manganese residue: Kinetics, isotherm, thermodynamics and mechanism analysis

Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore. In this work, modified electrolytic manganese residue (MEMR) as a high efficiency adsorbent for the removal of methylene blue (MB) was synthesized via hydrothermal method. The characterizations of MEMR were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N-2 adsorption/desorption isotherms, and scanning electron microscope. The results showed that with the BET specific surface area of 500.8 m(2)/g the MEMR reached the maximum adsorption capacity (548.15 m(2)/g) within 50 min when the pH of initial solution was 6.05 and the initial concentration of MB was 1600 mg/L. The adsorption kinetics and equilibrium isotherms were accurately described by the pseudo-second-order model and Langmuir isotherm, respectively. The FTIR spectra indicated that electrostatic attraction and stacking interaction were the main adsorption mechanisms. Thermodynamic analyses showed that the adsorption of MB on MEMR was a spontaneous and exothermic physisorption process. This study revealed that MEMR can be used as a low cost and eco-friendly potential adsorbent for removing MB from wastewater. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.