Surface Modification of Activated Carbon through Bacterial Adsorption and its Effect on Cadmium Removal from Aqueous Solution

Introduction/Objectives: The increasing contamination of water sources by pathogenic microorganisms and heavy metals necessitates the development of multifunctional adsorbents capable of addressing both simultaneously. In this study, fish scale-derived activated carbon (FSAC) was used to remove Staphylococcus aureus and Klebsiella pneumoniae through a column adsorption technique. Subsequently, FSAC pre-adsorbed with S. aureus (FSAC-M) was utilized in a batch adsorption experiment for the removal of cadmium (Cd). Methods: Bacterial removal was monitored via colony-forming units (CFU mL⁻¹) at 10-minute intervals, while Cd adsorption was evaluated using isotherm, kinetic, and thermodynamic analyses. Results: Both bacterial strains were effectively removed, with FSAC-M exhibiting a higher adsorption capacity (qm = 6.51 mg g⁻¹) than FSAC (qm = 5.43 mg g⁻¹) for Cd adsorption owing to the presence of microbial surface functionalities. The adsorption followed the Langmuir isotherm (R² = 0.996 for FSAC-M; 0.988 for FSAC), indicating monolayer adsorption. Although the kinetic data fit the pseudo-second-order model (R² = 0.997 for FSAC-M; 0.995 for FSAC), thermodynamic results indicated an endothermic, spontaneous, and predominantly physisorptive process (ΔH = 16.33–16.99 kJ mol⁻¹), with positive ΔS values reflecting increased randomness at the solid– solution interface. Discussion: Microbial pre-adsorption introduced additional binding sites and surface interactions, enhancing FSAC’s affinity for both biological and chemical contaminants. Conclusion: FSAC effectively adsorbed S. aureus and K. pneumoniae in a column setup, while FSAC-M demonstrated notable Cd removal in batch mode. The adsorption conformed to isotherm and kinetic models, with thermodynamic results indicating a spontaneous and temperaturedependent process, highlighting the applicability of FSAC for multifunctional water treatment.