Magnetic silica nanoparticles for the removal of $\mathrm{Pb}^{+2}$ from water

Zero valent iron impregnated silica nanoparticles ($\mathrm{Fe}^0/n$-$\mathrm{SiO}_2$) were synthesized using sol-gel process followed by supercritical drying, wet impregnation and hydrogen reduction. The synthesized nanoparticles were characterized by nitrogen Brunauer-Emmett-Teller ($\mathrm{N}_2$-BET), Scanning Electron Microscopy, Transmission Electron Microscopy, Scanning Electron Microscopy with Energy-Dispersive X-ray spectroscopy, Vibrating Sample Magnetometer and X-ray diffraction techniques. Prepared samples were found to be magnetic with ultra-low density ($0.048$ g/mL) and high surface area ($422$ m$^2$/g). Prepared samples were evaluated for adsorptive removal of $\mathrm{Pb}^{+2}$ ($5$, $10$, $25$ and $50$ ppm) from contaminated water. Results indicated that the adsorption of $\mathrm{Pb}^{+2}$ was faster at lower concentrations ($5$ and $10$ ppm) as $>80$ % of $\mathrm{Pb}^{+2}$ was removed within $480$ minutes. At higher concentrations, the adsorption was slower, and the removal efficiency of $51.24$ and $21.78$ % were observed for $25$ and $50$ ppm $\mathrm{Pb}^{+2}$ respectively, whereas for bare $\mathrm{SiO}_2$ nanoparticles, it was $39.64$ and $14.04$ %.