Methylene blue adsorption by Quercus cerris acorn shell based activated carbon: equilibrium, kinetic, and thermodynamic studies

The present study demonstrates that Quercus cerris acorn shell-derived activated carbon can serve as an effective and promising adsorptive material for the cationic Methylene Blue removing from aqueous solution via adsorption technique. The study explored how adsorbent concentration, temperature, initial adsorbate concentration, contact time, and pH influence MB adsorption onto QCAC. QCAC dosages of 30, 45, 60, 75, 90, and 105 mg/50 mL provided nearly 99.70% MB removal efficiencies for 50, 100, 150, 200, 250, and 300 mg/L MB solution concentrations. It was found that the adsorption of MB on QCAC is notably impacted by solution pH, and that higher temperatures enhance the adsorption process, particularly at lower adsorbent concentrations. Adsorption properties were characterized by utilizing various adsorption isotherms, e.g. Temkin, Langmuir, Freundlich, and Jovanović and by utilizing various kinetic models such as pseudo-first-order, and pseudo-second-order, and intra-particle diffusion models via their non-linear forms. When using non-linear version of isotherm models isotherm model, Freundlich and Temkin isotherm aligned well with the experimental data. The study evinced that the adsorption kinetics of QCAC by MB adapted well to kinetic model for pseudo-second order and the application of the particle-diffusion model contributed insights into MB adsorption kinetic mechanism on QCAC. Additionally, thermodynamic variables for the MB adsorption on QCAC were assessed, disclosing that MB adsorption process on QCAC was endothermic, reversible, and feasible.