###### 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 m\({}^{2}\) g\({}^{-1}\)) and superior water contact angle (143.8\({}^{\circ}\)). 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 \({}^{\circ}\)C. The rGOAs have been demonstrated to have great potential for the removal of siloxanes from biogas. reduced graphene oxide aerogel; Vitamin C; hexamethyldisiloxane; siloxane; adsorption 2021  
11 August 2021  
Accepted: 10 September 2021  
Submitted: 13 September 2021  
Volatile methyl siloxanes (VMSs) are products of the hydrolytic depolymerization of silicone. In VMS molecules, silicon atoms are alternately linked to oxygen atoms and methyl groups, exhibiting cyclic and chain structures labeled D and L, respectively (Figure S1) [1, 2, 3]. Due to the widespread use of silicone, the VMS content in biogas originating from the digestion of organic waste substances in sewage plants, municipal landfills, and farm fermentation tanks has recently grown quickly [4, 5, 6]. Their presence in biogas is proven to impose significant constraints on its energy application, for example, blocking the fan and wearing out the fenestrae of the engine, etc., which are fatal to the biogas power equipment, substantially increasing the production cost [3]. Therefore, the VMS removal from biogas has recently come into research focus. There are several available methods to remove VMSs, such as adsorption, absorption, biofiltration, and membrane filtering [7, 8, 9]. Among these techniques, adsorption has been the most widely used method because of higher efficiency, less risk, and lower cost than other approaches. Silica gel, activated carbons (ACs), and zeolites were applied in adsorbing VMSs, exhibiting good activity toward the VMS capture [10, 11, 12, 13, 14, 15]. However, in the presence of moisture, the siloxane polymerization reaction occurs attributed to the hydroxyl groups on the surface of ACs, zeolites, and silica gel, making thermal regeneration more difficult [16; 17; 18; 19]. Thus, novel materials for the VMS adsorption need to be developed. Graphene-based materials, for instance, graphene oxide (GO) and reduced graphene-oxide aerogels (rGOAs), have attracted significant attention for adsorbent applications [20; 21; 22; 23]. Graphene oxide is comprised of many functional groups on its edges and basal planes, including epoxide, hydroxyl, carboxyl, and carbonyl groups [24; 25; 26]. The hydrothermal reduction can be used to eliminate the GO functional groups, yielding rGOAs [27]. Compared with GO, rGOAs show better performance of adsorption toward non-polar pollutants as a consequence of their high surface area, high hydrophobicity, and low oxygen content, suggesting great application potential of rGOAs for the VMS removal [28; 29; 30; 31].