Preparation and characterization of chemically activated carbons derived from Mediterranean Posidonia oceanica (L.) fibres

In the present work, the preparation of several chemically activated carbons (CACs) from marine Posidonia oceanica fibrous biomass was performed using various activating agents. The chemical activation was carried out using phosphoric acid (H₃PO₄), potassium hydroxide (KOH), zinc chloride (ZnCl₂) and hydrogen peroxide (H₂O₂). The effects of those impregnating agents were investigated for all produced CACs via several chemical and structural analyses. The results showed that H₃PO₄ seems to induce the deepest impact on the P. oceanica fibres by providing the lowest conversion yield (16.9%). Besides, the pore analysis showed that two types of porosity were developed: (i) CACs characterized by an inner structure combining significant fraction of both mesopores and micropores (i.e. CAC-H₃PO₄, CAC-KOH and CAC-ZnCl₂) and (ii) CAC-H₂O₂ with a large mesoporous structure and a small fraction of microporosity. Dealing with the RAMAN and XPS analysis, it was showed that the main carbon fraction is structurally organized (i.e. graphite), especially for the CAC-ZnCl₂ sample. As for the isotherm and kinetic investigation, the experimental and modelling results revealed that CAC-H₃PO₄ was the best performing activated carbon by removing the highest methylene blue dye amount (137 mg/g) in the shortest time (1.3 h to reach the half reaction point).