Application of chemically modified palm ( <i>Elaeis guineensis</i> ) bunch fibers in the biosorption of methylene blue: kinetic and thermodynamic parameters

Abstract Methylene blue (MB) dye effluents pose significant environmental challenges that necessitate efficient removal methods. This study used biosorbents derived from in natura palm bunches (INPB), modified with H 3 PO 4 (ATPB) and NaOH (BTPB), to enhance adsorption efficiency. The biosorbents were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and X‐ray fluorescence (XRF), revealing that BTPB exhibited the highest porosity and concentration of basic groups, whereas ATPB predominantly displayed acidic functional groups. Adsorption was optimized under pH 8, 200 mg biosorbent, 240 min for BTPB, 360 min for ATPB and INPB, initial MB concentration of 200 mg L −1 , and temperatures of 25–45 °C. Superior performance was demonstrated by BTPB, achieving up to 98.02% removal at 100 mg L −1 MB concentration and maintaining 91.79% removal at 300 mg L −1 . Adsorption data fitted the Langmuir isotherm best ( R 2 ≥ 0.96), with maximum adsorption capacities ( Q max ) increasing with temperature: BTPB reached 67.56 mg g −1 at 45 °C, in comparison with 41.49 mg g −1 for INPB and 44.64 mg g −1 for ATPB. Thermodynamic analysis confirmed spontaneous adsorption (Δ G &lt; 0) and exothermic behavior (Δ H &lt; 0), especially for BTPB. Reusability tests demonstrated more than 76% removal efficiency after three cycles. These findings highlight the potential of modified palm bunch fibers as efficient and sustainable biosorbents for wastewater treatment.