Sustainable synthesis and environmental application of chitosan-Ocimum basilicum leaves-ZnO composite membrane for permanganate ion removal in wastewater treatment

This study introduces a novel and environmentally friendly method for developing a cross-linked chitosan-Ocimum basilicum leaves-ZnO (ChOBLZnO) composite membrane, specifically designed for the adsorption of permanganate ions (MnO₄-) from wastewater. Various characterization techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area analysis, were employed to confirm the membrane's synthesis quality, structural integrity, and surface properties crucial for adsorption. The BET analysis revealed a surface area of 228.64 m²/g, indicating a highly porous structure. The membrane exhibited a high adsorption capacity of 142.8 mg/g and an outstanding removal efficiency of 98.5%. The adsorption kinetics were best described by the pseudo-second-order model, with a correlation coefficient (R²) of 0.998, while the Freundlich isotherm model provided the most accurate fit for the adsorption behavior, with an R² of 0.995. Thermodynamic studies indicated that the adsorption process is spontaneous and endothermic, with negative Gibbs free energy and positive enthalpy and entropy values. Reusability tests showed that the ChOBLZnO composite membrane maintained a high removal efficiency across five cycles, with minimal performance loss. These results demonstrate the ChOBLZnO composite membrane's potential as an efficient and sustainable solution for wastewater treatment, offering both high efficiency and durability.