Engineered Ag–Fe bimetallic nanoparticles for efficient levofloxacin removal: Surface adsorption mechanism and antibacterial performance

A simple in-situ chemical reduction method was employed to synthesize silver-iron bimetallic nanoparticles (Ag_x-Fe_y BNPs) with inherent dual adsorptive and antimicrobial functionality. The nanoparticles (NPs) were thoroughly characterized using TEM, SEM, EDS, XRD, XPS, BET, ICP-OES and FTIR to determine their surface morphology, particle size, and elemental composition. Batch experiments systematically examined the adsorption kinetics and isotherm behavior of levofloxacin (LVN) onto Ag₁-Fe₇ BNPs, considering the influence of adsorbent dosage, adsorbate concentration, pH, temperature, soluble organic content, and electrolyte concentration. Adsorption kinetics were best described by the pseudo-second-order model (R² ' 0.996; χ² ≤ 2.14), and the Langmuir isotherm accurately depicted the process with a maximum capacity (Q_max) of 28.3 mg. g⁻¹. Thermodynamic analysis (∆S^∅= −82.4 J.mol⁻¹, ΔH°= −18.7 kJ. mol⁻¹, and ΔG° = −1.87 kJ. mol⁻¹) confirmed that the adsorption process was exothermic and spontaneous at room temperature, while the activation energy (E_a = 21.86 kJ. mol⁻¹) indicated a physisorption mechanism. Ag₁-Fe₇ BNPs showed efficient reusability over multiple adsorption-desorption cycles, while both Ag₁-Fe₇ BNPs and Ag₁-Fe₇@LVN nanocomposites exhibited strong antimicrobial activity against Gram-positive and Gram-negative bacteria, with LVN as a reference. The results clearly demonstrate that Ag₁-Fe₇@LVN exhibits outstanding dual functionality as both an efficient LVN adsorbent and a potent antimicrobial agent. This study presents a novel and facile synthesis route for multifunctional BNPs, offering a promising, sustainable, and integrated platform for advanced water treatment applications.