Preparation and characterization of activated carbon from brown algae (Sargassum sp.) using phosphoric acid activation for heavy metal adsorption

This study presents the successful preparation and evaluation of activated carbon derived from brown seaweed (Sargassum sp.) waste using chemical activation with zinc chloride (ZnCl₂) and thermal treatment. The resulting biosorbent was characterized by its iodine number, surface morphology, and adsorption efficiency for hexavalent chromium (Cr⁶⁺) ions in aqueous solutions. The activated carbons exhibited high microporosity, with iodine numbers reaching 290 mg/g at 800 °C, closely comparable to commercial activated carbon. SEM analysis revealed a porous surface structure, supporting its high adsorption capacity. Batch adsorption experiments demonstrated that Cr⁶⁺ removal efficiency was strongly influenced by solution pH, initial ion concentration, and contact time. Optimal removal (>90%) was achieved at pH 2, low metal concentrations, and a contact time of 120 minutes. The bio-based activated carbon showed promising potential as a cost-effective and environmentally friendly material for heavy metal remediation. This approach contributes to sustainable waste valorization and supports circular economy practices.