Plasma-modified viscose rayon activated carbon felt (VR-ACF) for Cu(II) and Cd(II) decontamination-mechanism and continuous-flow column operation

This study investigates the enhanced removal of Cu(II) and Cd(II) heavy metal ions from water using viscose rayon based activated carbon felt (VR-ACF). Employing a synergistic approach involving oxidant (KMnO₄) and plasma treatment, the surface modification process was meticulously examined. Key findings demonstrate the superior efficacy of KMnO₄ over H₂O₂ and Na₂S₂O₈ in coating. The synergy between plasma modification and 0.1 M KMnO₄ enhances VR-ACF's adsorption capacity, ensuring effective metal ion removal. Fine-tuning plasma parameters aids a comprehensive understanding of the modification process, guiding successful metal ion removal. Adsorption complexities are evidenced by prolonged kinetics of 720 min at pH 5 with high Q_max of 175.43 mg/g for Cu(II) and 223.22 mg/g for Cd(II), and extended column experiments, affirming the efficacy of modified VR-ACF. Thermodynamic analyses underscore the spontaneity and variability of Cu(II) and Cd(II) adsorption. X-ray photoemission spectroscopy (XPS), Scanning electron microscopy (SEM), X-ray Diffraction (XRD) investigations endorse complexation, ion-exchange, co-precipitation, and solvation interactions. Recyclability tests reveal maintenance of 60% removal efficiency for five cycles, with reduced efficiency in the presence of phosphates and divalent cations. The 50% breakthrough time for adsorption of Cu(II) and Cd(II) was found to be 58 days and 62 days, respectively. This underscores the efficacy of modified VR-ACF in sustainable water purification, particularly in extended column setups, offering a hopeful path for advanced materials in eliminating heavy metal ions.