Efficient batch and fixed-bed sequestration of a basic dye using a novel variant of ordered mesoporous carbon as adsorbent

Herein, an ordered mesoporous carbon (OMC) material was prepared using a metal and halogen free method, and its adsorptive potential for the cationic dye, ‘Methylene Blue’ (MB), was investigated. Batch studies were carried out to determine the influence of pH, dye concentration, adsorbent quantity, and contact time on adsorption behaviour. Adsorption models based on Langmuir, Freundlich, Temkin and Dubinin-Radunkevich isotherms were validated and the thermodynamic variables governing the nature and feasibility of reaction were evaluated. Values of the adsorption uptake at equilibrium (qe) decreased as the temperature was increased, suggesting thereby that the adsorption process involved was exothermic. Kinetic studies indicated that adsorption obeyed pseudo-second order behaviour and operated via a ‘film-diffusion’ mechanism. When attempts were made to carry out bulk removal of MB using a fixed bed adsorption column, 99.5% saturation could be achieved. Desorption of MB from the used column was performed and dye recovery was almost 100% in the first cycle and on 5th cycle 99% of dye was obtained. This pattern clearly indicates that for the cationic dye MB, OMC acts as a highly efficient and robust adsorbent.