Olive Mill Residue as an Innovative Adsorbent for Fe(III) Extraction: Understanding Adsorption Models and Kinetics

This research sought to assess the capability of olive mill residue powder as an economical and highly efficient adsorbent for extracting Fe(III) from aqueous solutions. The adsorption process was systematically investigated under varying conditions of contact time, pH, adsorbent dose, and initial Fe(III) concentration, with the experimental data fitted to seven isotherm models and four kinetic models. The Langmuir isotherm demonstrated the highest correlation (R2 = 0.994), with a maximum adsorption capacity (Qm) of 9.19 mg/g and a strong affinity (b = 0.179 L/mg), suggesting single-layer adsorption over a uniform surface. Kinetic studies revealed that adsorption follows pseudo-second-order kinetics (R2 = 1.000), suggesting chemisorption as the dominant mechanism, with rapid equilibrium achieved within 20 minutes. Under optimal conditions, the adsorbent showed exceptional performance across a broad range of Fe(III) concentrations, achieving up to 99% removal efficiency. This study introduces the innovative use of olive mill residue—an abundant agricultural by-product—as a sustainable and cost-effective adsorbent for removing Fe(III) from water. By converting olive mill residue—an abundant agricultural by-product—into an effective adsorbent, we present an environmentally friendly solution to reduce Fe(III) contamination in water. This approach not only tackles water pollution but also supports the circular economy by repurposing waste materials that might otherwise be discarded. Our results demonstrate that this adsorbent has practical potential, offering a cost-effective and accessible alternative to conventional treatment methods, which are often expensive. This work highlights the importance of exploring low-cost, renewable materials for environmental remediation and sets the stage for future research into similar waste-derived adsorbents.