Synthesis of mesoporous silica/iron oxide nanocomposites and application of optimum sample as adsorbent in removal of heavy metals

In this study, mesoporous silica/iron oxide nanocomposite (MCM-Fe₂O₃) was synthesized via hydrothermal technique. The chemical synthesis of MCM-Fe₂O₃ nanocomposite was achieved at 18 h. The effect of concentration of tetraethylorthosilicate (TEOS) on nanocomposites properties was studied during synthesis process. For this purpose, 0.5, 1.5, 2.5, 3.5, and 4.5 ml tetraethylorthosilicate (TEOS) were selected, respectively. The textural properties and microstructure of the nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), N₂ adsorption–desorption, and vibrating sample magnetometer (VSM) analysis. Results show that the nanocomposite with tetraethylorthosilicate (TEOS)/cetyltrimethylammonium bromide (CTAB) ratio of 5 exhibits large surface areas (461.19 m²·g⁻¹). Furthermore, this nanocomposite shows superparamagnetic behavior under external magnetic field compared to other samples. Moreover, results of removal of metal ions indicate that adsorption of Ni(II), Cd(II), Cr(III), Zn(II), and Pb(II) ions on the surface of adsorbent (nanocomposite) increases with the increase in solution pH, contact time, and adsorbent dosage. Furthermore, the maximum removal rates of heavy metals ions reach 53.0 %, 79.0 %, 61.0 %, 89.0 %, and 99.5 % at pH of 5, time of 50 min, and the weight of adsorbent of 0.16 with 2.5 ml TEOS, respectively.