Eco‐friendly waste coconut fiber activated carbon beaded by gelatin for high‐efficiency hexavalent chromium removal: Performance and mechanisms

Hexavalent chromium (Cr(VI)) can greatly endanger the environment and human health, necessitating efficient removal strategies. This study developed a novel adsorbent by modifying coconut fiber‐derived activated carbon (CFAC) with gelatin (CFAC‐GE) to enhance Cr(VI) adsorption. The best adsorption capacity of 15.25 mg/g was achieved under optimal conditions of pH 2, 2.0 g/L dose, 35°C, 50 mg/L Cr(VI) initial concentration. A maximum adsorption capacity was calculated to be 281.52 mg/g, which surpassed most biomass‐based adsorbents. The Cr(VI) adsorption process followed the Langmuir isotherm (monolayer adsorption) and the pseudo‐second‐order kinetic model (chemisorption). Thermodynamic analysis confirmed spontaneity (Δ G ° = −132.43 kJ/mol), endothermicity (Δ H ° = −25.31 kJ/mol), and increased entropy (Δ S ° = +360 J/mol·K), indicating favorable Cr(VI) binding. FTIR analysis showed gelatin introduced amine and hydroxyl groups, enabling Cr(VI) complexation and hydrogen bonding. Gelatin also improved adsorbent recoverability, retaining >60% efficiency after four cycles. Combining physisorption and chemisorption, CFAC‐GE offers a cost‐effective and sustainable solution for industrial wastewater treatment, repurposing agricultural waste in line with circular economy principles.