Utilization of a biosorbent derived from plant residues for the treatment of water contaminated with rhodamine B: preparation and characterization

Abstract

This study reports the preparation and characterization of a novel biosorbent obtained from oak pericarp for the removal of rhodamine B (RhB) dye from aqueous solutions. Comprehensive analyses (FTIR, SEM-EDX, TGA, BET, XRD, and pH_pzc) confirmed the presence of diverse functional groups and a heterogeneous surface morphology contributing to adsorption. Batch experiments were performed under varying operational conditions (pH, contact time, adsorbent dosage, ionic strength, temperature, and initial concentration), with optimal adsorption achieved at pH 2, using 0.05 g L⁻¹ of biosorbent and an equilibrium time of 300 min. Adsorption equilibrium data were best fitted by the Langmuir–Freundlich isotherm, suggesting heterogeneous and multilayer adsorption, with a maximum capacity of 160.809 mg g⁻¹ at 20 °C. Kinetic modeling indicated that the pseudo-second-order model best described the process, pointing to chemisorption as the dominant mechanism. Thermodynamic results confirmed the spontaneous and endothermic nature of RhB adsorption. Furthermore, regeneration tests revealed that the biosorbent retained high efficiency over multiple cycles, demonstrating its potential as a sustainable, low-cost, and environmentally friendly material for wastewater treatment.