Magnetic Mesoporous Silica Functionalized with Amine Groups for Efficient Removal of Heavy Metals and Bacterial Inhibition

Abstract

This study investigates the development of magnetic mesoporous silica functionalized with amine groups (MMS-NH₂) for its combined capability in heavy metal removal and bacterial inhibition, aiming to address critical water treatment challenges. MMS-NH₂ was successfully synthesized and meticulously characterized using various techniques: Field Emission Scanning Electron Microscopy (FESEM) for morphology, Brunauer-Emmett-Teller (BET) analysis for surface area and porosity, X-ray diffraction (XRD) for crystallinity, Fourier Transform Infrared (FTIR) spectroscopy for functional group identification, Thermogravimetric Analysis (TGA) for thermal stability, and Vibrating Sample Magnetometry (VSM) for magnetic properties. The removal efficiency of five common heavy metals (Pb(II), Cu(II), Ni(II), Hg(II), and Cd(II)) from water using MMS-NH₂ was investigated. influence of adsorbent dosage (0.05–2 g.L^− 1), solution pH (2–10), and initial metal ion concentration (50–200 mg.L^− 1) on the adsorption process was systematically investigated, revealing optimal conditions for each metal ion. Isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich) were employed to understand the adsorption mechanism, indicating a favorable and monolayer chemisorption process. Kinetic models (pseudo-first-order, pseudo-second-order, Elovich) were used to study the adsorption kinetics, suggesting a rapid and chemisorption-controlled mechanism. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were calculated, confirming the spontaneous and exothermic nature of the adsorption process. Furthermore, the antibacterial activity of MMS-NH₂ was investigated against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. The results demonstrated significant inhibition rates, ranging from 70 to 90%, for both bacterial strains. The amine group functionalization is attributed to enhancing both heavy metal adsorption capacity and bacterial inhibition.