Incorporation of graphene into silica-based aerogels and application for water remediation

Abstract

Graphene/silica nanocomposites in the form of highly porous aerogels are obtained for the first time by integrating a novel approach for the production of low defectivity graphene with a two-step route for the synthesis of silica-based monolith. Differently from the other synthetic methods, the use of co-gelation of dispersed phase and matrix followed by high temperature supercritical drying leads to well dispersed bilayered graphene inside a high surface area silica matrix with an open texture porosity. Physico-chemical characterization provides evidence that the developed graphene/SiO2 bulk aerogel nanocomposites combine the distinct features of both the dispersed graphene sheets and of the porous silica aerogel matrix. It was found that incorporation of graphene in the aerogel, even at low loading, increases significantly the hydrophobic behaviour of the materials. This, combined with the high surface/volume ratio of the aerogel, makes the resulting nanocomposite a suitable candidate as a novel oil sorbent for water remediation. In particular, the developed graphene/silica aerogels selectively and quickly uptake oil, up to more than 7 times the aerogel sorbent mass, from oilwater mixtures, and keeps floating on water after absorbing the oil phase. The suitability of the developed composites as a class of novel sorbents for environmental remediation in the occurrence of flammable liquid spills, where burning represents a major threat, is supported by specific features of silica aerogels such as a relative fire-resistance, in addition to the high porosity and hydrophobic nature.

The effect of graphene-nanoplatelets on gelation and structural integrity of a polyvinyltrimethoxysilane-based aerogel

“…16 The limitation of a low void fraction in this new class of aerogels (polymer-based particulate structure) can be improved using spinodal decomposition phase separation during polycondensation by increasing the amount of catalyst to accelerate hydrolytic polycondensation leading to a polymer-based co-continuous nanostructure. 7,9 Several studies showed the reinforcement of the conventional salt-based silica aerogels with biopolymers namely, polysaccharides (such as cellulose, pectin, 15 and chitosan 16 ), or protein (such as silk broin 17 ), as well as carbon materials (such as graphene, 18,19 graphene nanoplatelets (GnPs), and graphene oxide (GO) [20][21][22][23] ). Besides, some studies showed that the addition of GnPs or GO can introduce multifunctionalities to the new class of aerogels made of pre-polymerized silica-based precursors ($30 wt% GnPs).…”

A new type of microphotoreactor with integrated optofluidic waveguide based on solid-air nanoporous aerogels

“…A peak at approximately 800 cm −1 is then due to symmetric stretching vibrations of Si–O–Si. The comparison of the spectra of untreated (figure 5 a ) and HMDS-treated (figure 5 b ) samples clearly indicates that the aerogels have been modified, since the intensities of the broad Si–OH band around 3400 cm −1 and the other Si–OH peak around 960 cm −1 are reduced upon treatment [43,44]. In addition, the presence of a sharp peak around 2900 cm −1 corresponding to CH 3 symmetric and asymmetric vibrations and a peak at 837 cm −1 corresponding to Si–C stretching vibrations indicates that HMDS indeed reacted with silanol groups on the backbone of the treated samples.…”

Growing CeO2 Nanoparticles Within the Nano-Porous Architecture of the SiO2 Aerogel

“…Due to these microstructural features, silica aerogels are well-known for a number of extraordinary properties such as high optical transmission, high open porosity, low dielectric constant, low refractive index, and extremely low thermal conductivity (Malfait et al, 2015;Wan et al, 2018). These properties enable the exploitation of silica aerogels in many technological areas, such as air and water purification (Cao et al, 2006;Loche et al, 2016), thermal insulation in buildings and space vehicles (Fesmire, 2006;Lamy-Mendes et al, 2018), sensing and catalysis (Amonette and Matyáš, 2017).…”