Synthesis and Characterization of Thiol-Functionalized Magnetic (Core) Mesoporous Silica-Titanium (Shell-Shell) Nanocomposites for Efficient Copper Ions Removal from Aqueous Solutions

In this study, magnetite (Fe₃O₄) nanoparticles were synthesized simultaneously with mesoporous silica (MCM-41), followed by the attachment of mesoporous titanium dioxide (mTiO₂) to obtain Fe₃O₄@MCM-41@mTiO₂. 3-mercaptopropyl trimethoxysilane (MPTMS) was used as a precursor for the functionalization of thiol over magnetic mesoporous titania-silica is referred to as Fe₃O₄@MCM-41@mTiO₂@SH. Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), zeta potentials analysis, and Brunauer–Emmett–Teller (BET) analysis were used to characterize the adsorbents. Parameters that influence adsorption, such as pH, adsorbent dosage, contact time, adsorbate concentration, and thermodynamics, were examined for the removal of copper ions from aqueous solutions. pH 6.5 was determined to be the optimal condition for the experiments. The Sips isotherm and pseudo-second-order model exhibited the highest degree of fit for both adsorbents Fe₃O₄@MCM-41@mTiO₂ and Fe₃O₄@MCM-41@mTiO₂@SH, respectively. The maximum adsorption capacity of Fe₃O₄@MCM-41@mTiO₂@SH was 30.08 mg/g which was reported higher than another adsorbent, and further investigation was carried out for Fe₃O₄@MCM-41@mTiO₂@SH like, thermodynamic analysis and recyclability. The thermodynamics demonstrated that the adsorption was spontaneous and endothermic, and the positive ΔS° also increased the disorder or randomness of the system. Fe₃O₄@MCM-41@mTiO₂@SH also has the potential to be recycled up to five times for copper ions, with approximately 70% removal efficiency from aqueous solutions.