Amoxicillin adsorption from aqueous solution by magnetite iron nanoparticles: molecular modelling and simulation

Molecular modelling and simulation were used to examine the efficacy of iron nanoparticles (Fe₃O₄–NPs) in removing amoxicillin (AMX) from aqueous media and determine the optimal conditions. Fe₃O₄–NPs were initially ascertained using scanning electron microscopy, and Fourier transform infrared spectroscopy. The molecular optimisation modelling via DFT confirmed AMX molecule has chemical potential (–3.59), and electrophilicity index (2.14). The results established that a small chemical hardness = 3.0 eV and molecular energy gap of 6.01 eV, which makes it reactive. The molecule of the antibiotics could interact and be absorbed by the lactase enzyme. The parameters: pH (3–7), time (15–80 min), Fe₃O₄–NPs dosage (0.1–1.0 g/L), and antibiotic concentration (10–100 mg/L) were studied. The impact of optimum variables pH3, and dosage (0.5 g/L) for adsorption of AMX molecules onto coated Fe₃O₄–NPs translated to 98% efficiency at 60 mg/l of AMX and 60 min. The adsorption data fitted the Langmuir (R ²: 0.9245) with minimal error metrics RMSE ≤ 1.2 when compared to the Freundlich isotherm R ² (0.88) and intraparticle diffusion model R ² (0.58). The maximum adsorption capacity of AMX to Fe₃O₄–NPs corresponds to 6.47 mg/g with a corresponding adsorption constant of 2.8. Furthermore, AMX adsorption onto Fe₃O₄–NPs followed pseudo-second-order at R ² (0.9999), with an adsorption constant (k = 3.6 × 10⁻²g/mg.min).