Pencil graphite supported nano zero-valent iron for removal of levofloxacin from aqueous solution: Effects of pH, kinetic and biological activity

A highly efficient, and potentially recyclable antibacterial composite was prepared in an efficient simple process. Antimicrobial levofloxacin (LEV) was used to functionalize the surface of nano zero-valent iron (Fe⁰) supported by pencil graphite (PG). The surface morphology, elemental composition, particle size, and removal efficiency of the PG-Fe⁰ composite were confirmed by UV, FTIR, EDX, SEM, TEM, and XRD techniques. The potential influence of pH, adsorbate concentration, contact time, and temperature on the removal efficiency of LEV by the magnetic composite (PG-Fe⁰) from an aqueous solution was investigated. The well-known established models were used to examine the adsorption isotherms, and the results showed that the kinetic adsorption data fit well with the pseudo-second-order model, with the highest removal efficiency achieved from pH 5–7 (85%). The maximum adsorption capacity q_max on the surface of Fe⁰-PG for LEV was obtained using the Langmuir isotherm at pH 6.5 (66.3 mg/g) and pH 8 (11.4 mg/g). All adsorption thermodynamic parameters at pH 6.5 suggested a chemisorption endothermic natural process ΔH^o(44.4 kJ/mol), and the negative value of free Gibbs energy indicated a spontaneous process at an ambient temperature. Furthermore, the removal efficiency of the PG-Fe⁰ composite was better than that of the Fenton-like catalyst performance for both Fe⁰ and PG-Fe⁰. Reusability and antibacterial activity of adsorbed LEV on the surface of PG-Fe⁰ were investigated against various types of gram-positive bacteria; (E. faecalis, S. epidermidis, and S. aureus) and gram-negative; (E. coli, K. pneumonia, and P. Mirabilia) via agar well diffusion method. Finally, the magnetic feature of the PG-Fe⁰-LEV composite has numerous potential for recovery and reuse.