Biochar prepared from co-pyrolysis of municipal sewage sludge and tea waste for the adsorption of methylene blue from aqueous solutions: Kinetics, isotherm, thermodynamic and mechanism

Biochar was generated from municipal sludge and tea waste through co-pyrolysisin this study and was characterized by Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The effect factors including dosage, contact time, pH, temperature on the adsorption properties of methylene blue (MB) onto biochar were investigated. The adsorption kinetics, isotherm, thermodynamic and mechanism also were also studied. The results showed that pseudo-second order kinetics was the most suitable model for describing the adsorption of MB onto biochar. Equilibrium data were well fitted to the Langmuir isotherm model. A rise in operating temperature enhances MB adsorption on blather. Adsorption thermodynamic of MB on biochar showed that the adsorption was a spontaneous and endothermic process and revealed'favorable spontaneous under higher temperature conditions. Meanwhile, the positive values of Delta S suggest the increased randomness at the solid/solution interface during the sorption of MB onto biochar. The mechanism between MB and biochar involved electrostatic interaction, ion exchange, surface complexation, physical function and others. This work shows that the biochar hold promises acting as effective adsorbent to remove dyes in the wastewater. (c) 2016 Elsevier B.V. All rights reserved.