Study on efficient removal of anionic, cationic and nonionic dyes from aqueous solutions by means of mesoporous carbon nanospheres with empty cavity

In this study, the efficiency of the adsorption of anionic dye Direct Red 23 (DR23), nonionic dye Direct Green 97 (DG97) and cationic dye Basic Yellow 28 (BY28) from aqueous solutions onto hollow mesoporous carbon nanospheres (HMCN) was investigated. The adsorbent was characterized by means of XRD, HRTEM, TGA, Raman spectroscopy, FTIR, BET and zeta potential measurements. The influence of dye initial concentration, temperature and pH on DR23, DG97 and BY28 adsorption onto HMCN was investigated. Equilibrium data were analyzed by model equations such as Langmuir and Freundlich isotherms and were best represented by Langmuir isotherm model showing maximum monolayer adsorption capacity 769.2 mg g(-1), 312.5 mg g(-1) and 909.1 mg g(-1) for the DR23, DG97 and 8Y28, respectively. The experimental kinetic data were analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The adsorption kinetics was best fitted to the pseudo-second-order kinetic model. Thermodynamic parameters, change in free energy Delta G degrees enthalpy Delta H degrees, and entropy Delta S degrees were also evaluated, indicating that the adsorption of DR23, DG97 and 8Y28 was spontaneous and endothermic in nature. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.