Adsorption studies of methylene blue onto ZnCl2-activated carbon produced from buriti shells (Mauritia flexuosa L.)

• Activated carbon was prepared from a new material, buriti shells.
• A microporous activated carbon (75.10% of micropores) was obtained.
• The adsorption dynamics was evaluated by several isotherm and kinetic models.
• Monolayer adsorption capacity for methylene blue is 274.62 mg g−1.

The present study reports the preparation of an activated carbon produced from buriti shells (ACb) using ZnCl2 as activating agent and its ability to remove methylene blue dye (MB) from aqueous solutions. The obtained ACb was characterized by N2 adsorption–desorption isotherms, SEM and FT-IR. The results show that ACb presents microporous features with BET surface area (SBET) of 843 m2 g−1 and functional groups common in carbonaceous materials. Adsorption studies were carried out and experimental data were fitted to three isotherm models (Langmuir, Freundlich, and Redlich–Peterson) and four kinetic models (pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion). The isotherm model which best fitted to experimental data was Redlich–Peterson. However, the g parameter of this model indicated that the adsorption of MB onto ACb occurs according to the mechanism proposed by Langmuir, which showed maximum monolayer adsorption capacity of 274.62 mg g−1. Kinetic studies demonstrated that the Elovich model is suitable to describe the experimental data. Moreover, it was found that the intraparticle diffusion is the limiting step of adsorption process.