Synthesis of Nano-silica Oxide for Heavy Metal Decontamination from Aqueous Solutions

In the current study, nano-silica oxide (nano-SiO2) was fabricated via the sol-gel technique. Then, the prepared nano-SiO2 was characterized using X-ray diffractometer (XRD), transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) specific surface area analysis. Furthermore, the fabricated nano-SiO2 was applied for the adsorption of lead Pb (II) and chromium Cr (VI) from aqueous solutions. Additionally, the influence of different operating factors such as contact time (0-180 min), initial pH (1-11), nano-SiO2 dose (0.1-8 g L-1), initial metal ion concentration (5-100 mg L-1), and the temperature (30-85 degrees C) was investigated. The nano-SiO2 doses of 0.5 and 1 g L-1 were selected as the optimal adsorbent dose for the removal of Pb (II) and Cr (VI), respectively. These doses achieved a removal efficiency of 82.3% and 78.5% for Pb (II) and Cr (VI), after 60 and 90 min, at initial pH values of 5 and 2, respectively, using 10 mg L-1 initial metal concentration, and at room temperature. Lastly, kinetic and equilibrium studies were competently fitted using the pseudo-second-order and Freundlich models, respectively. Adsorption thermodynamic studies designate the spontaneous and thermodynamic nature of the adsorption process. These results reveal the efficiency of the fabricated nano-SiO2 as an adsorbent for heavy metal removal from aqueous solutions.