Fabrication of Mesoporous Silica Nanoparticle-Decorated Graphene Oxide Sheets for the Effective Removal of Lead (Pb 2+ ) from Water.

Mesoporous silica nanoparticle-decorated graphene oxide nanosheets (MSiO 2 -GO) were synthesized and characterized for the active removal of lead (Pb 2+ ) from the water. MSiO 2 NPs were prepared via an ultrasonication method using tetraethyl orthosilicate (TEOS), and GO sheets were obtained via a modified Hummers' method. X-ray diffraction, UV-vis spectroscopy, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy specified the composition of MSiO 2 NPs and GO sheets. The surface charge and texture of the MSiO 2 -GO nanosheets were obtained using the ζ-potential technique and by field emission scanning electron microscopy. The relative cytotoxicity test of MSiO 2 NPs and MSiO 2 -GO nanosheets was performed on Murine Raw 264.7 cells before implying the treatment of water. Adsorption of Pb 2+ ions on MSiO 2 -GO nanosheets was examined at various parameters such as different aqueous pH values (2.0-10.0), MSiO 2 -GO nanosheet doses (3, 5, 10, 15, 20 mg L -1 ), time intervals (2-30 min), and temperatures (25-45 °C). About 90% of Pb 2+ ions were removed from water within 30 min (MSiO 2 -GO dose: 15 mg L -1 ; initial Pb 2+ ions: 50 mg L -1 ; temperature: 25 °C; shaking speed: 200 rpm). The maximal uptake of Pb 2+ was obtained at solution pH 6.0. Pseudo-first- and pseudo-second-order kinetic rate equations describe the sorption dynamic data. Pb 2+ sorption isotherms were modeled using the Freundlich and Langmuir isotherm models. The possible mechanism of binding of Pb 2+ ions onto MSiO 2 -GO nanosheets has been discussed. The exhausted MSiO 2 -GO nanosheets were successfully regenerated using 0.005 M HNO 3 as the desorbing agent.