Facile Fabrication of Nano-sized SiO2 by an Improved Sol-Gel Route: As an Adsorbent for Enhanced Removal of Cd(II) and Pb(II) Ions

We herein report a direct and facil sol-gel method for the preparation of porous silicon dioxide nanoparticles using dissolved silica gel and nitric acid. We prepared SiO2 nanoparticles at three different pH values: 6, 7, and 8. The washed and dried products were calcined at 800 degrees C for 2 h. The average crystallite size of the prepared SiO2 nanoparticles was ca. 37.7 nm. The products were characterized by using FT-IR, TEM, FE-SEM, and XRD analyses. The as-prepared SiO2 nanoparticles showed high adsorption capacities; ca. 32.2 mg g(-1) and 42.2 mg g(-1), for the removal of Pb(II) and Cd(II) ions, respectively, from aqueous media. The adsorption data followed well the pseudo-second-order and Langmuir isotherm models. The determined thermodynamic parameters: Delta G degrees (from - 5.026 to - 5.180 kJ/mol for Cd(II) ion adsorption and from - 5.528 to - 5.732 kJ/mol for Pb(II) ion adsorption) and Delta H degrees (- 7.00 and - 7.607 kJ/mol, respectively), indicate the spontaneous, exothermic, and physisorption nature of the adsorption process. Besides, the excellent reusability and adsorption capacity for SiO2 nanoparticles revealed their good efficiency for the removal of Pb(II) and Cd(II) ions from aqueous media.

Automated summary

In this study, a direct and easy method for the preparation of porous silicon dioxide nanoparticles was reported, and their adsorption performance for the removal of heavy metal ions from aqueous media was investigated. The results showed that the prepared SiO2 nanoparticles exhibited high adsorption capacities and good reusability, making them efficient for the removal of Pb(II) and Cd(II) ions from water.