Bio-based activated carbon from coffee husk for efficient removal of Fe³⁺ and Cu²⁺ ions from water

Contamination of water with iron and copper ions poses significant environmental and health challenges, necessitating the development of effective, sustainable treatment methods. In this study, bio-based activated carbon was synthesized from coffee husk waste through a controlled two-step thermal activation process to remove Fe³⁺ and Cu²⁺ ions from aqueous solutions. Structural characterization indicated an amorphous, mesoporous carbon material with abundant oxygen-containing functional groups and a point of zero charge of 9.25, which facilitated metal ion adsorption. Batch adsorption experiments demonstrated high removal efficiencies, and the Langmuir isotherm model predicted monolayer adsorption with maximum capacities of 23.34 mg g⁻¹ for Fe³⁺ and 26.03 mg g⁻¹ for Cu²⁺. High correlation coefficients suggest uniform adsorption sites and the strong affinity of metal ions for the activated carbon, with chemisorption identified as the dominant mechanism. These findings indicate that activated carbon derived from coffee husk is a cost-effective, sustainable, and efficient adsorbent for the removal of iron and copper, supporting agricultural waste valorization and environmentally friendly water treatment.