One-Step Synthesis of Hierarchical Micro-Mesoporous SiO₂/Reduced Graphene Oxide Nanocomposites for Adsorption of Aqueous Cr(VI)

Abstract

A novel micro-mesostructured SiO 2 /reduced graphene oxide (RGO) nanocomposite was successfully synthesized by means of simple one-step hydrothermal method under acidic conditions using tetraethoxysilane (TEOS) and graphene oxide (GO) as the raw material. The nanocomposites were characterized by TEM, XRD, FT-IR, TG-DSC, and N 2 adsorption-desorption. The results showed that GO was partially reduced to RGO without adding any reducing agent and SiO 2 nanoparticles (ca. 10 nm) were uniformly anchored on the surface of RGO. The optimized composite contained 75 wt.% SiO 2 and possessed hierarchical micro-mesoporous structure with surface area of 676 m 2 /g. The adsorption performance of synthesized SiO 2 /RGO samples was investigated by removal efficiency of Cr(VI) ions in wastewater. The Cr(VI) adsorption reached equilibrium in 30 min and 98.8% Cr(VI) adsorption efficiency was achieved at pH = 2 at 35 ∘ C. Stability tests showed that SiO 2 nanoparticles effectively prevented RGO from the restacking. The mechanisms of composite formation and for Cr(VI) adsorption were suggested.

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“…The DSC curves showed two exothermic peaks of GO and Fe 3 O 4 @GO at 189.1, 203.1 • C, respectively, which were in accord with the second phase of weight loss by TG (Mohan et al, 2019). Due to the evaporation of combined water, which was an endothermic process as depicted by the endothermic peak of DSC curve (Yi et al, 2017).…”

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“…The obtained NH 2 ‐SiO 2 was filtered, washed with toluene, ethanol and acetone, and dried under vacuum at 60°C for 12 hours. Secondly, GO was boned on the surfaces of NH 2 ‐SiO 2 ; 0.23 g GO was dispersed in 500 mL N,N ‐dimethylformamide for 4 hours according to the method, and 0.22 g of DCC and 5.00 g of the prepared NH 2 ‐SiO 2 were added for 24 hours under stirring . The product (GO@SiO 2 ) was filtered and washed with methanol and ultrapure water three times to remove the unreacted reagents.…”

“…Secondly, GO was boned on the surfaces of NH 2 -SiO 2 ; 0.23 g GO was dispersed in 500 mL N,Ndimethylformamide for 4 hours according to the method, and 0.22 g of DCC and 5.00 g of the prepared NH 2 -SiO 2 were added for 24 hours under stirring. 12 The product (GO@SiO 2 ) was filtered and washed with methanol and ultrapure water three times to remove the unreacted reagents. Thirdly, rGO@SiO 2 was obtained according to the literature 36 ; 4.50 g of GO@SiO 2 was dispersed in 250 mL of ultrapure water with 3 mL of aqueous ammonia and 16 mL of hydrazine hydrate to reflux for 12 hours.…”

“…11 Yi et al prepared a reduced (rGO) and silica nanoparticles composite as a solid phase extraction material which was used to extract the metal ions chromium with the adsorption rate of 98.8% in 30 minutes. 12 Zhang et al found that after GO was bonded to silica gel and further reduced, the obtained material had a better separation effect for the neutral and polar compounds on high performance liquid chromatography (HPLC). When separating benzene-containing analytes, the π-π stacking between graphene and benzene rings was the main factor.…”

“…The removal of oxygen‐containing functional groups mainly uses hydrazine hydrate with more obvious characteristics . Yi et al prepared a reduced (rGO) and silica nanoparticles composite as a solid phase extraction material which was used to extract the metal ions chromium with the adsorption rate of 98.8% in 30 minutes . Zhang et al found that after GO was bonded to silica gel and further reduced, the obtained material had a better separation effect for the neutral and polar compounds on high performance liquid chromatography (HPLC).…”