Assembly of Ultralight Dual Network Graphene Aerogel with Applications for Selective Oil Absorption

Abstract

High-performance graphene aerogels with welldeveloped internal structures are generally obtained by means of introducing additive materials such as carbon nanotubes, cellulose, and lignin into the aerogel network, which not only enhances the cost but also complicates the preparation process. Therefore, tailoring the internal structure of pristine graphene aerogel in a feasible way to achieve high performance is of great significance to the practical applications. Herein, a novel cysteamine/L-ascorbic acid graphene aerogel (CLGA) was fabricated by a simple one-step hydrothermal method followed by freeze-drying. Through the creative combination of the reducing agent L-ascorbic acid and cross-linking agent cysteamine, a dual-network structure was constructed by both layered physical stacking and vertical chemical cross-linking. The addition of cysteamine not only enhanced the reduction degree but also assisted the formation of more vertical connections between graphene nanosheets, resulting in more abundant pores with smaller sizes compared with graphene aerogels prepared by the traditional hydrothermal reduction method. CLGA possessed an ultra-low density of 4.2 mg/cm 3 and a high specific surface area of 397.9 m 2 /g. As expected, this dual-network structure effectively improved the absorption capacity toward a variety of oil and organic solvents, with an outstanding oil absorption capacity up to 310 g/g. Furthermore, CLGA possessed good mechanical properties and oil/water selectivity. The absorbed oil could be recovered by both continuous absorption-removal process and mechanical squeezing, making the as-prepared aerogel superior absorbent material for a variety of applications, such as selective oil absorption and water treatment.

Carbon Nanomaterials for Wastewater Treatment

“…Similarly to CNTs, graphene [5,70] and its derivatives have a high surface-to-weight ratio (~2600 m 2 g -1 ) and high chemical stability, which qualify them to be as potential adsorbent in the elimination of organic [71,72] and heavy metal ions from industrial effluents and domestic wastewater [71][72][73].…”

“…To improve the recovery and adsorbing capacity of graphene, graphene aerogels were prepared and applied successfully in selective separation of emulsified oil from wastewater. This macrostructural form of graphene ensured the recovery of adsorbents for reuse applications [5]. To utilize the benefits of macrostructured graphene, 3D porous graphene hydrogels (GHs) with super adsorption capacity for different types of pollutants (antibiotics, dyes, and heavy ions) were prepared and used effectively in wastewater treatment [75].…”

“…The physicochemical methods have drawbacks in terms of generating products mostly in impure forms due to being nonselective in their nature. On the other hand, the selective separation techniques such as ion exchange, membrane filtration, solvent extraction, and adsorption methods [4,5] have become more useful as they are able to yield products in purified forms. The technique of solvent extraction in wastewater purifications is well established and was initially applied by various industries for separation of uranium and copper.…”

Mechanically Tunable Spongy Graphene/Cellulose Nanocrystals Hybrid Aerogel by Atmospheric Drying and Its Adsorption Applications

“…In particular, the volume ratio of absorbed liquid is much higher than lightweight aerogel and other graphene-based foams as shown in Figure 5a), such as the nanofiber hybrid graphene aerogels [12], Graphene coating PUS [25,26], Surface modified PUS [27], and functional graphene sponge [5,28]. These volumetric oil absorption rates can be calculated according to the density of oil absorption material ρ m in the literature, due to the…”

“…The obtained anisotropic aerogel with a hierarchical porous structure could recover to its initial height after 20 times of axial compression and high oil absorption cycles. Dai et al prepared an ultralight dual-network GA through a straightforward hydrothermal reduction followed by lyophilization [5], and the hierarchical porous network structure improved the absorption capacity toward various solvents, with absorption capacity (ratio of weight before and after soaking) up to 310 g/g. Gao et al synthesized a spring-like 3D graphene aerogel with a long-range lamellar microstructure to undergo the large monolithic deformation by bidirectional freezing and freeze drying strategies [6].…”