Sustainable Biosorption and Isotherm Modeling of Heavy Metals Using Phragmites australis

This study investigates the biosorption of heavy metal ions (Pb, Fe, Cu, Cd, Zn, and Mn) from wastewater using the powdered biomass of Phragmites australis (Common Reed) under varying conditions, including temperature, pH, retention time, plant powder size, and biosorbent weight. The results showed that plant powder size significantly influenced the biosorption effi-ciency, with the 0.5 mm powder diameter yielding the highest removal rates for the heavy metal ions. The optimal temperature for biosorption was found to be between 30-50°C, achieving up to 99.94% removal for Pb. The ideal pH for the biosorption of all metals was 7, and the best reten-tion time for ion removal was 30 minutes, with a mean biosorption rate of 99.82% for Fe. A bio-sorbent weight of 10 g/L was also identified as the most effective for metal ion removal. Fur-thermore, two forms of P. australis, dry pieces and powdered biomass, were tested, with pow-dered biomass exhibiting superior biosorption performance. FTIR analysis revealed the in-volvement of carboxyl and hydroxyl functional groups in the biosorption process, while SEM imaging confirmed the surface interaction between metal ions and the plant material. The ad-sorption of heavy metals onto P. australis was effectively described by both Langmuir and Freundlich isotherm models, indicating a mix of monolayer coverage and heterogeneous inter-actions. The Langmuir model showed the highest adsorption capacities for Mn²⁺ (6.29 mg/g) and Cd²⁺ (5.10 mg/g), with Fe²⁺ (0.0138 L/mg) and Cu²⁺ (0.0130 L/mg) exhibiting strong affinities. Sim-ilarly, the Freundlich model indicated favorable adsorption (n > 1) for all ions. Cu²⁺ and Fe²⁺ had the highest adsorption intensities (n = 2.06), with the strongest capacities observed for Fe²⁺ (Kf = 0.231) and Cu²⁺ (Kf = 0.222). These findings confirm the high potential of P. australis as a sustaina-ble and eco-friendly biosorbent.