Development and application of a shrimp shell waste/FeCl₂-FeCl₃ composite as an efficient bioadsorbent for dye...

This study investigates the preparation and characterization of a bio-based adsorbent derived from shrimp shells, chemically modified with FeCl₂ and FeCl₃, for the efficient removal of methylene blue (MB) from aqueous solutions. This research aims to transform seafood waste into a high-value composite material for wastewater treatment. Structural and morphological evaluation (XRD, BET, SEM/EDX) confirmed the successful integration of iron oxides, resulting in increased surface roughness and the presence of iron-rich active sites. FTIR analysis identified amine and hydroxyl groups as the primary functional groups responsible for MB binding. Adsorption effects yielded optimal conditions: adsorbent mass of 0.050 g, initial MB concentration of 150 mg L^-1, temperature of 25 °C, and solution pH of 12, with a maximum monolayer adsorption capacity of 114.47 mg g^-1 according to the Langmuir isotherm model. The Elovich model, suggested adsorption on energetically heterogeneous surfaces, while equilibrium data follow the Dubinin-Radushkevich isotherm, indicating a predominantly physical adsorption, best described kinetic data. Thermodynamic analysis further revealed that the process is spontaneous and exothermic. Finally, process optimization using a Box-Behnken design (BBD) under response surface methodology showed high model predictability, establishing this composite as a cost-effective and eco-friendly solution for the remediation of dye-contaminated effluents.