Simultaneous removal of Pb(II), Cd(II) and bacteria from aqueous solution using amino-functionalized Fe3O4/NaP zeolite nanocomposite

Fe3O4/NaP nanocomposite was synthesized and modified using 3-aminopropyltrimethoxysilane (3-APTS)-functionalization. Fe3O4/NaP/NH2 was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, elemental analysis, energy-dispersive X-ray analysis, vibrating sample magnetometer, Brunauer-Emmett-Teller and thermogravimetric analysis techniques. Batch adsorption studies of Pb(II) and Cd(II) on Fe3O4/NaP/NH2 were investigated. The effect of experimental parameters (including pH, adsorbent dose, heavy metals' concentration, adsorption time and temperature) was studied. The results indicated that Fe3O4/NaP/NH2 have a high removal percent for Pb(II) and Cd(II) (more than 95%). The metal-loaded Fe3O4/NaP/NH2 nanocomposite could be recovered from the aqueous solution by magnetic separation and regenerated easily by acid treatment. The experimental data were fitted to Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (DKR) isotherm models. The Langmuir equation showed a better correlation with the experimental data than the other two models. The adsorption kinetics data were found to follow the pseudo-second-order kinetic model for Pb(II) and pseudo-first-order for Cd(II). The thermodynamic parameters (ΔG, ΔH and ΔS) were measured and the negative value of Gibbs energy indicated that the adsorption process was spontaneous in nature. The in vitro antibacterial activity of Fe3O4/NaP/NH2 composites before and after removal of metals show good inhibition on bacterial growth against Bacillus subtilis (as Gram-positive bacteria) and Pseudomonas aeruginosa (as Gram-negative bacteria), and the antibacterial activity of it comparison with standard drugs.