Adsorption performance and mechanism of methylene blue on chemically activated carbon spheres derived from hydrothermally-prepared poly(vinyl alcohol) microspheres

Chemically activated carbon microspheres (CACms) are synthesized by sulfonation and carbonization of PVA (polyvinyl alcohol) microspheres, which is prepared by hydrothermal method with the assistance of FeCl3. The as-prepared samples are characterized by SEM, XRD and FTIR measurement Functional carbon microspheres with sulfonic group are found to be excellent adsorbents for cation dye removal with a higher adsorption capacity. Methylene blue (MB) as a typical kind of cation dye is chosen to investigate the adsorption performance of CACms. The parameters, such as pH, temperature, contact time, concentration of adsorbate, are employed to study the influence for adsorption capacity. The obtained results suggest that CACmc can effectively adsorb methylene blue with adsorption capacity increasing from 474.6 to 602.4 mg g(-1) as the initial concentration increases from 20 to 300 mg/L in a wide pH range. The kinetics, isotherms and adsorption mechanism of functional CACms adsorption are discussed in detail. The adsorption data onto CACms can be fitted to pseudo-second-order model better than the pseudo-first-order model. The Langmuir adsorption model agrees well with the experimental data and the maximum adsorption capacity can reach 925.9 mg g(-1) at 45 degrees C. Temperature change is found to have a significant effect on the adsorption process. The thermodynamic parameters such as the free energy, enthalpy and entropy of adsorption are evaluated and it was found that the adsorption was endothermic and spontaneous. In addition, the as-prepared CACms exhibit selective adsorption ability for MB. (C) 2016 Elsevier B.V. All rights reserved.