Study of adsorption of methylene blue onto activated carbon from lignite

An adsorbent has been prepared from lignite by chemical activation using ZnCl2. Pore properties of the activated carbon such as the surface area determined by the Brunauer–Emmett–Teller (BET) method, pore volume, pore size distribution, and pore diameter were characterized by t-plot based on N2 adsorption isotherm. The determined surface area of the adsorbent which was primarily contributed by micropores was 600 m2/g. Activated carbon from lignite was used to adsorb methylene blue (MB) from an aqueous solution. The effects of the initial dye concentration, agitation time and initial pH have been studied. It was found that the adsorption isotherms followed both Langmuir and Freundlich models. However, the Langmuir model gave a better fit to all adsorption isotherms than the Freundlich one. The kinetics of adsorption of MB has been tested using pseudo-first-order, pseudo-second-order models, as well as the intra-particle diffusion equation. The results obtained show that the adsorption of MB from an aqueous solution onto microporous activated carbon takes place according to the pseudo-second-order model. © 2015, Allerton Press, Inc.