Vitamin C-Assisted Fabrication of Aerogels from Industrial Graphene Oxide for Gaseous Hexamethyldisiloxane Adsorption

Abstract

Volatile methyl siloxanes (VMSs) as a trace impurity in biogas decreases its energy utilization, and thus need to be removed. In this paper, a one-step hydrothermal reduction was performed to produce three-dimensional reduced graphene oxide aerogels (rGOAs) using industrial-grade graphene oxide (IGGO) as raw material and vitamin C (VC) as a reductant to facilitate the fabrication of rGOAs. The synthesis of rGOAs was a simple, green, and energy-efficient process. The developed rGOAs were characterized using the Brunauer–Emmett–Teller method, Raman spectrometry, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction measurements and contact angle. The results obtained showed that rGOA-1 with a VC/IGGO ratio of 1/1 (m/m) exhibited a hierarchical porous structure and super-hydrophobicity, yielding a high specific surface area (137.9 m2 g−1) and superior water contact angle (143.8°). The breakthrough adsorption capacity of rGOA-1 for hexamethyldisiloxane (L2, a VMS model) was 11 times higher than that of IGGO. Low inlet concentration and bed temperature were considered beneficial for the L2 adsorption. Interestingly, rGOA-1 was less sensitive to water, and it was readily regenerated for reuse by annealing at 80 °C. The rGOAs have been demonstrated to have great potential for the removal of siloxanes from biogas.

Efficient Removal of Siloxane from Biogas by Using β-Cyclodextrin-Modified Reduced Graphene Oxide Aerogels

“…The broad peaks at 3441 cm − 1 are attributable to the O–H stretching vibration in the carboxyl groups, C–OH groups, and adsorbed-state water. In the IGGO spectrum, 2927 cm −1 (low-intensity stretching and bending vibrations from C–H), 1727 cm −1 (C=O stretching vibration in the carboxyl groups), 1600 cm −1 (C=C vibration of the graphene skeleton), and 1050 cm −1 (C–O–C stretching vibration in the epoxy groups) were observed, which indicates that IGGO has a large number of oxygen-containing groups on its surface [ 36 ]. After hydrothermal reduction, the C–O–C band at 1050 cm −1 and the C=O peak at 1727 cm −1 in the rGOA were no longer evident, which indicates that some of the oxygen-containing groups in IGGO underwent reduction.…”

“…The Yoon–Nelson model was selected to predict the theoretical breakthrough adsorption capacity ( Q B,th , mg g −1 ) and the theoretical breakthrough time ( t B,th , min) and to better understand adsorption phenomena of L2 in the β -CD-rGOAs. The model is represented by Equation (2) [ 36 ]: where K YN is the Yoon–Nelson constant of the model, t is the adsorption time (min), and τ is the time when the ratio C out,t / C in = 0.5.…”

Hexamethyldisiloxane Removal from Biogas Using a Fe3O4–Urea-Modified Three-Dimensional Graphene Aerogel

“…The removal performances of IGGO and the Fe 3 O 4 –urea–rGOAs for an L2 gas stream were measured using a fixed-bed dynamic adsorption setup. The full experimental setup and related details of the methods are described in the published literature [ 24 , 25 ]. For each test, 0.10 g of Fe 3 O 4 –urea–rGOA was used and the experimental parameters were T = 25 °C, an L2 inlet concentration of 14.62 mg L −1 , and V g = 50 mL min −1 .…”

“…A reduced graphene oxide aerogel (rGOA) with a three-dimensional porous network structure is formed by the cross-linked stacking of graphene sheets. Zheng et al [ 24 , 25 ] prepared a series of micro/narrow mesoporous reduced graphene oxide aerogels under hydrothermal conditions by using VC and amine as reducing agents. These aerogels exhibited a good adsorption performance for L2, as well as an excellent cycling stability [ 24 , 25 ]; however, the increase in the specific surface area of the rGOA and the regulation of the pore size were restricted.…”

“…Zheng et al [ 24 , 25 ] prepared a series of micro/narrow mesoporous reduced graphene oxide aerogels under hydrothermal conditions by using VC and amine as reducing agents. These aerogels exhibited a good adsorption performance for L2, as well as an excellent cycling stability [ 24 , 25 ]; however, the increase in the specific surface area of the rGOA and the regulation of the pore size were restricted. Therefore, finding new ways of improving the texture properties of rGOAs has continued to attract attention.…”