Facile Fabrication of 3D Graphene–Silica Hydrogel Composite for Enhanced Removal of Mercury Ions

Abstract

Adsorption is a highly promising and widely used approach to remove Hg(II) ions from contaminated water. The key to this technology is exploring the effective adsorbent. The three-dimensional (3D) graphene as reduced graphene oxide hydrogel (rGH)-encapsulated silica gel (SG-PEI/rGH) was prepared by a moderate chemical reduction strategy using ascorbic acid. This composite structure was characterized by FTIR, XRD, and SEM analysis and used as adsorbents for Hg(II) ions. Its adsorption capacity toward Hg(II) ions was 266 mg/g and increased about 32% compared with the silica gel because of reduced graphene oxide hydrogel (rGH). Mechanism study showed that the high adsorption ability was due to the formation of an N–Hg complex with multi-amino groups on the surface of polyethyleneimine-modified silica gel (SG-PEI) and the rapid diffusion of adsorbed ions attributed to the rGH network structure. This composite SG-PEI/rGH would be a promising material for the removal of Hg(II) ions.

Layer-by-Layer Method to Prepare Three-Dimensional Reduced Graphene Materials with Controlled Architectures Using SiO2 as a Sacrificial Template

“…On the other hand, XRD patterns are shown in Figure 2, where the SiO 2 particles covered with GO (SPG) exhibited a peak at 23°attributed to the amorphous silica particles. 29 GO presents a typical peak at 9.7°associated with the sheets stacking inherent to this material due to its periodicity (see Figure S3a), and according to Bragg's law, the position of this peak indicates an interlayer spacing of 0.911 nm. 39 However, such a peak was no longer observed after covering the SiO 2 particles associated with the low concentration of GO needed to form SPG material, as only two coverings of GO were used to obtain the final rGS material.…”

“…On the other hand, XRD patterns are shown in Figure , where the SiO 2 particles covered with GO (SPG) exhibited a peak at 23° attributed to the amorphous silica particles . GO presents a typical peak at 9.7° associated with the sheets stacking inherent to this material due to its periodicity (see Figure S3a), and according to Bragg’s law, the position of this peak indicates an interlayer spacing of 0.911 nm .…”

“…Some carbon inverse opals have been prepared previously through the direct combination of SiO 2 particles and a graphene precursor, such as graphene oxide (GO). SiO 2 particles, SBA-15 mesoporous silica amorphous material, and silica gel have been employed to develop 3D graphene architectures. − However, the as-obtained materials presented irregular structures since SiO 2 particles with irregular shapes were used.…”

Adsorption Processing for the Removal of Toxic Hg(II) from Liquid Effluents: Advances in the 2019 Year

“…This composite structure was used to investigate its performance against the removal of Hg(II) from aqueous solutions. Its adsorption capacity was 266 mg/g, which represented an increase of 32% if compared with the silica gel [65]. This increment was attributable to the formation of a N-Hg complex with multi-amino groups on the surface of polyethyleneimine-modified silica gel (SG-PEI), coupled with the rapid diffusion of Hg(II) due to the rGH network structure.…”

The Effects of Hydrophobicity and Textural Properties on Hexamethyldisiloxane Adsorption in Reduced Graphene Oxide Aerogels

“…Previously, we developed a modified silica gel siloxane adsorbent with good recyclability and found that its adsorption performance was affected by its textural properties, such as the specific surface area ( S BET ), total pore volume ( V tot ), micropore volume ( V micro ) and contact angle [ 16 , 17 , 18 ]. Reduced graphene oxide aerogels (rGOAs) have good textural properties and strong hydrophobicity [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ], although their application to biogas siloxane removal has not been reported. In addition, rGOAs were prepared using commercially available industrial grade graphene oxide (IGGO) without any reducing agents.…”