Valorization of olive stones into a granular activated carbon for the removal of Methylene blue in batch and fixed bed modes

This work aims at valorizing olive stones as an agricultural waste into an efficient granular activated carbon for the removal of Methylene blue in batch and fixed bed modes from aqueous solutions. The adsorption capacity of the prepared activated carbon was evaluated using these two modes. The activated carbon preparation was carried out in two steps: an impregnation with 50% phosphoric acid at 170 °C for 2.5 hours followed by physical activation using steam at 750 °C. Nitrogen adsorption studies at 77 K on the prepared and commercial (Organosorb 10) activated carbons resulted in specific surface areas of 1031.5 and 1029.2 m².g⁻¹, respectively. The Langmuir model was found to describe correctly the isothermal adsorption of Methylene blue for both adsorbents and resulted in adsorption capacities for the olive stone activated carbon of 107 mg.g⁻¹ and 121 mg.g⁻¹ for the commercial one. This study shows that olive stones as a waste can be valorized into a value added adsorbent that can replace effectively costly commercial materials.