Preparation of superhydrophobic/superoleophilic sugarcane bagasse-derived reduced graphene oxide anchored foam with application in oil/water separation

Preparation of superhydrophobic/superoleophilic sugarcane bagasse-derived reduced graphene oxide anchored foam with application in oil/water separation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Preparation of superhydrophobic/superoleophilic sugarcane bagasse-derived reduced graphene oxide anchored foam with application in oil/water separation Kamatchi Jothiramalingam Sankaran, Monami Mukherjee, Anita Mallick, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6034955/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 18 Jun, 2025 Read the published version in Waste and Biomass Valorization → Version 1 posted 5 You are reading this latest preprint version Abstract The conversion of bio-waste into carbon nanomaterials offers a sustainable and cost-effective approach to meet the growing demand for advanced functional materials and to treat the oil spill challenge in the massive water body. In this context, a sustainable, environment-friendly and efficient superhydrophobic/superoleophilic material is prepared by using sugarcane waste bagasse derived graphene oxide (GO) and functionalized to reduced graphene oxide (rGO) coated- polyurethane (PU) foam (rGO@PU) via a low-cost facile method for effective oil-water separation. The foam is dipped in the GO suspension followed by immersion in hydrazine hydrate to facilitate the reduction of GO to rGO. The scanning electron microscope (SEM) images illustrate the uniform deposition of rGO on the skeleton of PU foam. The rGO@PU foam shows a high repellency to water and affinity to various oil, with water contact angle (WCA) of 158.96° and oil contact angle of nearly 0°. Such non-wetting behaviour of the foam signifies the formation of Cassie-Baxter surface with low surface energy. Owing to its hierarchical pore structure, the adsorption capacities of rGO@PU foam for various oils are recorded in the range of 25-50 g/g. Furthermore, a demonstration is performed on the foam that successfully separated and recovered heavy oil like diesel and low oil like chloroform from the water. Hence, the GO/rGO@PU foam is evinced as an effective promising adsorbent material for oil spill cleanup. Adsorption educed graphene oxide polyurethane foam oil/water separation superhydrophobic super oleophilic sugarcane bagasse Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Statement of Novelty This research presents a novel, sustainable, and cost-effective approach for oil-water separation by utilizing sugarcane bagasse-derived graphene oxide (GO) to fabricate reduced graphene oxide-coated polyurethane foam (rGO@PU). Unlike conventional methods that rely on expensive and non-renewable materials, this study pioneers the valorization of agricultural bio-waste, specifically sugarcane bagasse, to synthesize advanced carbon nanomaterials. The facile dip-coating and reduction process ensures uniform deposition of rGO, imparting the foam with exceptional superhydrophobic (WCA of 158.96°) and superoleophilic (oil contact angle ~0°) properties. The rGO@PU foam demonstrates superior adsorption capacities (25-50 g/g) across various oils and effectively separates both heavy and light oils from water. The integration of bio-waste valorization, low-cost fabrication, and high-performance oil adsorption showcases a significant advancement in sustainable material design for environmental remediation, particularly in addressing large-scale oil spill challenges. Introduction The global interest in achieving sustainability and circular economy has boosted the demand for utilizing biomass wastes for synthesizing nanomaterials in order to align with the concept of resource efficiency and waste management. While the disposal of biomass wastes challenges the existing financial as well as environmental costs, their conversion into valuable functional and energy materials alleviates the cost and presents an opportunity to create a closed-loop system. Biomass or agricultural wastes, which are several and abundant in nature and a renewable source, are rich in carbon and provide a sustainable foundation for developing versatile advanced carbon-based materials. The intrinsic hierarchical structural diversity of biomass and organic composition provides a natural template for producing various carbon derivatives with tailored properties. Carbon, a fundamental element in the periodic table, is known as the foundation of all life forms and the cornerstone of modern science owing to its unparalleled versatility and structural diversity. Its unique electronic configuration enables it to form a stable and complex bond with other elements as well as itself, leading to diverse allotropic forms and derivatives from conventional graphite and diamond to advanced nanostructured graphene, carbon nanotubes (CNT) and fullerenes [1]. These carbon-based functional materials possess remarkable properties including chemical and high thermal resistance, robust mechanical properties, lightweight, flexible, high thermal and electrical conductivity, making them indispensable in several scientific and industrial applications [2-3]. The key advantages of valorizing biomass waste in the development of carbon nanomaterials include their high carbon content, high abundancy, versatile molecular structure, diverse feedstock, more active sites, well-developed porous structures with enhanced surface area as well as maintain carbon neutrality [4-5]. However, the major challenges posed by such green feedstock are moderate or low processing yield, versatility in chemical composition and energy consumption [5]. Out of various carbon allotropes derived from biomass wastes, graphene stands as an extraordinary two-dimensional material (2D) that embraces hybridization with a single layer of carbon atoms assembled in a hexagonal lattice. The isolation of graphene marked a revolutionary advancement, unravelling its unique properties like high surface area, high percolation threshold, high mechanical strength (up to 1000 GPa), high thermal (4840-5300 ) and electrical (2 ×10 5 ) [6-7]. The derivative of graphene classified as graphene oxide (GO) and reduced graphene oxide (rGO) expands its utility through variable interface chemistry, enabling their applications in electronics, drug delivery, sensors, adsorbents and photocatalytic activity [8]. GO has attracted significant attention from the scientific community and is preferred over reduced rGO in several applications owing to its high oxygen-containing functional groups, high dispersion stability and lower defect density [9]. In contrast to graphene and rGO, GO is highly dispersive in water due to its oxygen-containing polar groups and increased surface charge that facilitate the interaction with water- or solvent-based suspensions [10]. In the conventional process, GO can be synthesized by the oxidation process of graphite that forms graphite oxide followed by the exfoliation of graphite oxide to GO. However, carbon-rich biomass feedstock needs to undergo graphitization before oxidation and this step involves either physical or chemical processing. Although, biomass-derived carbon nanomaterials are a safer choice to cover the discussion regarding carbon dioxide ( ) emission and non-renewability, the challenges included in the synthesis process are mostly low-level products without fine molecular structure. Several methods are established to synthesize graphene from biomass including mechanical exfoliation [11], chemical exfoliation [12], chemical vapor deposition (CVD)[13] , microwave process [14] and plasma-enhanced CVD (PECVD) [15]. However, every synthesis route exhibits some limitations and challenges depending upon the application of graphene. For example, the mechanical exfoliation route generates a low yield of graphene and the exfoliated layers may have varying thickness and properties. Chemical exfoliation involves several acids and oxidizing agents that can introduce additional irrelevant functional groups and quite not always eco-friendly. The CVD route, which is excessively utilized to produce graphene, poses challenges that involve high-cost equipment with high-purity precursor gas along with large-area deposition [16- 17]. Furthermore, compared to conventional thermal treatment, the microwave technique supports biomass for uniform heat transfer and rapid heating; however, it has a low energy efficiency due to the mismatching between poor dielectric properties of biomass and microwave power [16- 18]. PECVD is reported as an eco-friendly route to exfoliate graphene into its derivatives; it is limited by its equipment complexity [16]. Out of the above-mentioned techniques, pyrolysis is reported as a convenient method to derive high graphitic carbon materials under high temperatures (300-1200°C) and inert atmosphere. Additionally, this bottom-up approach is viable for a large variety of biomass precursors and minimization of greenhouse to facilitate sustainability. Various agricultural waste feedstock has been investigated for their potential in carbon nanoparticles, such as jute, grass, sugarcane, corn stalk, rice husk and straw, wheat straw, bamboo, fruit wastes, coconut shell, groundnut shell, etc. Among them, sugarcane bagasse (SB) is hugely disposed of by juice makers and industries. India is the second largest sugarcane producer around the globe, produces 350 Mt of bagasse annually, and is projected to reach a value of 100-125 Mt by 2030 [19]. The carbon nanoparticle derived from SB exhibits a unique porous structure, large surface area, high adsorption capacity and larger pore volume making it a potential candidate for several advanced applications [20]. One such critical exploration is oil-water separation, where the superhydrophobic and superoleophilic properties of efficient and sustainable materials play a crucial role. The water pollution arising from oil spillage, development of oil production and oil wastewater generated from various industrial processes poses a grave threat to marine species, human health and national development. Recent highlights surface on the oil spill incident in Chennai, India, originating from the Chennai Petroleum Corporation Ltd (CPCL) that has reported to cross at least 20 sq. km into the sea, posing a major threat to aquatic life. A variety of traditional methods have been delivered for oil-water separation such as skimming, gravity separation, air flotation, flocculation, centrifugation and filtration [21- 22]. However, these methods are limited by their low processing efficiency, high operational cost and ineffectiveness for oil-water emulsion separation. Among these, adsorption offers several advantages, including highly efficient selective separation, separation of oil from oil-water emulsion, and eco-friendly, making it a preferred method of the separation process. The growing demand for materials of separate oils and organic contaminants has attracted porous oil-absorbing materials such as graphene, hydrophobic nano silica, polydopamine, CNT, etc. However, the practical applicability of these materials is hampered by their cost, environmental incompatibility, low stability and poor usability [23] . As an alternative, foam-based three-dimensional (3D) effective adsorbents have been widely used for oil/water separation due to their comprehensive benefits such as low density, 3D porous network and special wettability. Various 3D porous materials such as functional sponges, carbon aerogels, nickel foam and resin foams have been studied; however, sponges particularly garnered significant attention for their high efficacy towards oil adsorption capacity [24- 25]Among various foaming materials, polyurethane (PU) foam captured substantial attention due to its larger surface area, good mechanical strength, lightweight, high permeability and low cost [24- 26]. However, commercially available PU foam exhibits hydrophilic property that makes it less effective for selective adsorption of oil. Therefore, the structural modification of these PU foams is a prerequisite step to transform the surface into hydrophobic and oleophilic. Herein, the sugarcane bagasse-derived rGO anchored PU (rGO@PU) foam is prepared by a facile method and reported for the selective adsorption of oil from the oil-water mixture. The bottom-up pyrolysis route is employed to derive GO from sugarcane bagasse to eliminate volatile and hydrophilic compounds. The commercial PU foams are dispersed with GO and then dipped in an organic substrate to induce rGO. Sugarcane bagasse-derived GO serves as a scaffold to support the PU foam. In addition, introducing organic substrate that produces amine groups during the reduction process of GO to rGO helps to construct superhydrophilic and superoleophilic surfaces for stable and efficient repelling of water and adsorption of several oils. The rGO@PU foam shows superhydrophobic behavior in different salt concentrations, temperatures and pH, indicating the exceptionally strong and stable attribute of rGO@PU foam. The tunable structural, defect characteristic and the surface properties of rGO@PU foam significantly influence its wettability and adsorption properties. The superoleophilic rGO@PU foam exhibit excellent oil affinity and the presence of rGO related functional group on the foam enhances adsorption capacity, making it highly favourable for effective oil-water separation application. In consequence, this work offers a green and sustainable development of graphene based materials from biomass waste for the effective exploitation of oil/water separation. Experimental Methods Materials Sugarcane bagasse was taken from a sugar milling industry in Bhubaneswar, Odisha, India. Pure chemicals such as tetrahydrofuran (THF), hydrazine hydrate 80%, acetone, ethanol, sodium chloride (NaCl), isopropanol, toluene, butanol and hexane chloroform were procured from Central Drug House (CDH) fine chemicals Pvt. Ltd., New Delhi and polyurethane (PU) foam was purchased from Neustro Poly Products Pvt Ltd. All chemicals were used without further refinement. Oils such as pump oil, hydraulic oil, kerosene, mobile, paraffin, vegetable oil, engine oil, coconut oil, mustard oil, terpene, petrol, diesel and crude oil were purchased from Bhubaneswar, India. Double distilled water was used for all synthesis and treatment processes. Synthesis of GO from sugarcane bagasse The sugarcane bagasse was chopped into small pieces and thoroughly washed with deionized (DI) water. It was then dried in a hot air oven at 100°C for 4 h. The dried bagasse was pulverized and sieved to obtain particles of approximately 25 microns. The pulverizing phase decreased mean particle size and increased specific surface area. The sieved sample was carbonized and subsequently annealed in a tube furnace under an inert atmosphere of argon gas at 800°C for 5h to obtain GO. The annealing temperature and thermal stability for the carbonized sample were determined from the thermal degradation profile of TGA and crystallization temperature observed in DSC, as shown in Fig. S1. Finally, the GO sample was allowed to cool in an argon atmosphere to reach room temperature. Fabrication of rGO@PU foam Before treatment, the original PU foam was cut into small cubes, each measuring 1 × 1 × 1 cm³. The foam cubes were then ultrasonically cleaned for 45 minutes in THF, followed by additional cleaning in ethanol and DI water to remove any external stains and impurities. After the cleaning process, the foams were dried in a hot-air oven at 80°C for 3 h. To prevent moisture adsorption, the cleaned foams were immediately transferred to an airtight container upon removal from the oven. To prepare the GO suspension, 0.03 g of GO derived from sugarcane bagasse was dispersed in 10 mL of DI water using ultrasonic treatment for 1 h to avoid any kind of accumulation. The cleaned PU foam was then gradually immersed in the GO suspension and allowed to soak for 1 h under ambient conditions. After soaking, the foams were dried at 80°C in a hot-air oven for 4 h to eliminate any additional water, resulting in GO-coated PU foam. The coated foam was subsequently immersed in 25 mL of 80% hydrazine hydrate and placed in an oven to facilitate the reduction of GO to rGO. After the reduction process, the foam was rinsed with DI water to eliminate residual hydrazine hydrate and dried again in the hot-air oven at 90 °C for 6 hours, yielding the final rGO@PU foam. Characterization The Raman characteristics were investigated using a Renishaw in Via micro-Raman spectrometer (λ =532 nm) to know the crystalline quality of the materials. The structural morphology of the materials was observed using a Zeiss Evo 15 Field emission scanning electron microscope (FESEM) equipped with an energy-dispersive X-ray (EDX) detector. To prepare the sample for the FESEM, first, a slice of foam was taken and the foam was placed on a copper tape fixed on the sample holder of the SEM. The sample was then subjected to gold sputtering in order to avoid charging. The conditions of SEM measurements are a sputter ion pump (i) 2.61 × 10−8 Pa; (ii) 4.2 × 10−7 Pa; vacuum: 1.8 × 10−4 Pa; beam power (emission current): 42.60 μA; accelerator volt: 15 kV; mode−secondary electron detector; and working distance: 8 mm. The microstructural features of the materials were observed using JEOL transmission electron microscopy (TEM) equipped with energy-dispersive X-ray. The selected area electron diffraction (SAED) pattern was taken under 20 cm camera length and 1000 μm aperture in TEM. The TEM samples of the rGO composite were prepared by the extraction of rGO from PU foam in an ethanol solution using the ultrasonication process and by drop-casting on a TEM Cupper (Cu) grid. Contact angle and oil-water separation measurements The samples were analyzed for their contact angle using a digital microscope camera. A 5 μL water droplet was placed as a probe liquid on the sample surface, and the droplet's image was captured. ImageJ software with the drop-analysis plugin was used to determine the contact angle [27-28]. The standard error of the contact angle measurement was calculated from five readings taken at different locations on the samples. Kerosene and chloroform were used to demonstrate oil/water separation on the surface and underwater. The weight of the rGO@PU foam was measured. The foam was then immersed in oil and various organic solvents for 1 minute, and its weight was measured again to determine the adsorption capacity. The adsorption capacities of different oils were calculated using a specific equation [29] where m 1 and m 2 are the weight of the foam before and after adsorption of oils/organic solvents, respectively. Results And Discussion Structural analysis Fig. 1(a) shows the FESEM micrographs of the rGO@PU foam. The 3D structure with the interconnected pores. These pore structures in the foams facilitate the adsorption and internal transport of the rGO to act as a hydrophobic/oleophobic substrate. Furthermore, the high-magnified FESEM micrograph shown at the inset of Fig. 1(a) illustrates the deposition of rGO on the skeleton of PU foam, which signifies a rough, wrinkled and homogenous coating of rGO existed on PU foam. The surface of PU foam is closely packed by those rGO, creating a multiscale roughness structure, which depicts the transition of hydrophilic PU foam to hydrophobic one. Fig. S3 shows the quantification of O and C by using EDX. Moreover, Fig.1(b) shows the HRTEM micrograph of the rGO with wrinkled structures, and the inset shows the SAED pattern of the ring-structured rGO pattern. Raman spectroscopy is an indispensable technique used to investigate the degree of disorderness, crystallinity and number of layers present in carbon-based materials. Here, the spectra are collected for the carbonized sugarcane bagasse, sugarcane-derived GO and rGO-coated foam and the peaks are fitted with 3 Gaussian bands Fig.2 (a). All three samples show signature D and G bands at 1360 cm -1 and 1590 cm -1 attributed to the in-plane vibration of carbon atoms in the graphitic lattice and signify the characteristic peak of the carbon-contained materials [30] The appearance of the G band probe the formation of sp 2 -hybridized carbon network that caused due to in-plane vibration of C-C stretching [31], where D-band indicates the density of structural defects and disorders. Out of the three samples shown, the GO spectrum exhibits a higher D-band intensity relative to the G-band, indicating a comparatively higher degree of distortions in the localized 2-D structures. Moreover, the wide spectrum and the outspread area under D-bands peaks convey the formation of graphitic amorphous phase due to sp 3 carbon content upon oxidation effect introduced due to thermal forces. The presence of the sp3 bond introduces distortion and defects in regular sp2 lattice, leading to a higher defect density. After a thorough observation of the nature of peaks, further information was extracted from the fitting parameters to evaluate the degree of disorderness, defect density and crystallite size. The degree of disorderness and crystallite size in the carbon atoms can be evaluated by estimating the intensity ratio of D and G band peaks. Moreover, the defect density and the distance between the defects are also calculated and all together presented in Fig. 2(b). The empirical estimation suggested that GO (0.96) and rGO (0.88) exhibit comparatively higher value than carbonized sugarcane bagasse and amounts to less than 1.00 ( <1.00). This observation is attributed to a greater degree of lattice distortion of sp 3 hybridization due to oxidized graphene. Briefly explains, the greater the ratio of two intensities, the more will be disordered of the morphology of the sample. Besides, the lateral crystallite size 13.27 ( ) is observed to be higher in both GO and rGO cases with lower defect density, suggesting a nanocrystalline structure of graphitic phase with fewer defects. These above-described results confirm the alternation of the structural integrity of the carbonized sugarcane bagasse upon the thermal event and thermal event-assisted reduction, making it suitable for the tailored oil-water separation application. Wetting Characteristics Figure 3 shows a series of optical micrograph images of rGO@PU obtained from contact angle measurement. Fig. 3(a1) - (a3) represents the state of three different periods of water droplet adherence on the rGO-coated foam substrate. It can be seen that the water droplet adheres to the foam substrate relatively constantly over time. The maximum time is recorded for 30 min with a maximum WCA of 158.96°. Such value remains the same in all three-time frames and indicates the superhydrophobic behaviour of preparing the rGO-coated foam. It also signifies the force of adhesion between the water droplet and the surface of the sponge is relatively excellent. Fig. 3(b) reveals the wettability performance of the rGO@PU foam with a 5 μL drop of mango juice, tea, soya sauce, milk, tomato sauce, and glycerine. In each of the cases, the contact angle of the rGO@PU foam is recorded to be 158.96°, indicating the domineering effect of superhydrophobic nature, which is extremely resistant to wetting by lipids. Fig. 4(a). It affirms the potential application of the rGO@PU foam for requiring lipid repellence. The uniform coating of the rGO throughout the network of the foam enhances the surface roughness of materials, which is evident from FESEM micrographs. This roughness plays a key role for trapping air pockets that reduces solid-liquid contact area, leading to superhydro phobicity. This characteristic follows the Cassie-Baxter non-wetting phenomenon, [32] where air pockets trapped within the rough surface contribute to the high-lipid contact angle, preventing lipids from penetrating the material. The functionalization during the reduction process of the foam introduces hydrophobic functional groups in the microstructure, hence achieving lower surface energy. The presence of these functional groups facilitates the interaction with various liquids, making the surface not only the water but also several organic solvents efficiently. Additionally, chemical firmness (varying pH, temperature, and salt concentration) experiments were carried out on the superhydrophobic rGO@PU foam to evaluate its practical usability. Fig.4(b) shows the measured WCA values at pH values from 1-13. It is observed that the WCA values remain high across the range of pH levels, implying stable, superhydrophobicity regardless of exposure to strongly acidic and basic environments of the rGO@PU foam. The superhydrophobic properties of the prepared foam are further analysed under varying temperatures from 283 K to 373 K, as illustrated in Fig. 4(c). The WCA is observed to remain consistently high, above 150°, across a wide temperature range, indicating the material's thermal stability to maintain water repellence regardless of temperature fluctuations. This stability across varying temperatures and pH levels underscores the robustness and suitability of the rGO@PU foam for applications in environments where thermal conditions and chemical exposures may vary significantly. In the next investigation, WCA on the surface of the foam is measured at different salt concentrations, ranging from 1 M to 7 M Fig. 4(d). The consistent high contact angles across all concentrations suggest that the superhydrophobic properties of the material are stable and unaffected by the presence of salts, even at low to high concentrations. Together, these results confirm the material robust and uniform water-repellent properties, making it suitable for applications requiring resistance to both a wide range of liquids and saline environments. Oleophilicity is a substantial parameter to study the oil/water separation that provides evidence of the performance of the adsorption of oils. In this case, the oil contact angle (OCA) is estimated by taking 5 μL oil as a probe liquid and dropped on the surface of the as-prepared rGO@PU foam. The optical micrographs from the contact angle are shown in Fig. 3(c). The oil droplet has made contact with the surface for 5 ms, as shown in the figure, however, it is quickly distorted and later spread over completely in 10 ms, as shown in Fig. 3 (c1-c3). The rGO coating and low energy of oils render the effective adsorption of oil into the microstructure of the foam and reveal the superoleophilic behaviour. It is valuable to know the impact of rGO in encouraging superhydrophobic and superoleophilic behaviour on PU foam. The superhydrophobicity of rGO@PU foam is ascribed to low surface energy formed by the coated rGO. When the GO nanosheet is enclosed on the foam skeleton, the high surface area of GO and strong accretion effect between the overlapping layers make the GO sheet stably wrap around the foam [33- 34]In addition, there is a strong van der Waals interaction between the GO and the skeleton of the PU foam, which causes an even and steady coating [35] The thermal behaviour of GO in the presence of hydrazine hydrate leads to the breakdown of oxygen-containing functional groups, facilitating the reduction of GO [36] Additionally, reduction lead to local sheet deformation and have a deoxygenating effect, which would enhance the great binding between the rough rGO sheets. The non-wetting behaviour of rGO@PU foam is due to the creation of the Cassie-Baxter surface with low surface energy, which forms an air gap between the surface and water. For comparison, we took pristine PU foams. The WCA, with corresponding SEM morphologies of these samples, is shown in Fig. S2. The WCA, with Hence, rGO@PU foam displayed high water repellence. However, oils, due to their low surface energy, promoted the flow of rGO@PU foam, resulting in oleophilicity. Hence, when the rGO@PU foam is placed in the oil-water emulsion, the air in the holes of the foam is occupied by the oil due to the capillary effect, van der Waals force, and hydrophobic interaction, whereas the air pores of rGO@PU foam repel water. Therefore, the air-filled superhydrophobic foam is changed during the oil adsorption process into oil-filled foam, promoting quick oil adsorption. Fig. 5 (a) explains the adsorption capacities of various oils and solvents, highlighting significant differences across the rGO@PU foam. The adsorption capacity of rGO@PU foam to various oils and organic solvents is found to be in the range of 20–60 g/g. It is observed that oils and solvents with low viscosity, such as chloroform, butanol, acetone, petrol, and ethanol, show much higher adsorption capacity and get saturated in just 2.5 s. The highest adsorption capability is achieved by toluene (50.0 g/g) followed by isopropanol (45.7 g/g), ethanol (42.2 g/g), acetone (40), butanol (40.7 g/g) and terpene (40.6 g/g) than its weight. The differences in adsorption behaviour are likely due to the varying physical and chemical properties of the substances, such as molecular size, viscosity, and polarity, which influence their interaction with the adsorbent material. This is due to the low viscosity of oils that promoted easy penetration into the low surface energy framework of rGO@PU foam. Whereas high viscous oils and solvents such as mustard oil, pump oil, hydraulic oil, and crude oils could be adsorbed and saturated within 8 to 10 s. This suggests that the adsorption mechanism is highly dependent on the nature of the adsorbate, and the faster adsorption rates observed for lighter hydrocarbons indicate more efficient interaction with the adsorbent rGO@PU foam. Oil/water separation Rapid adsorption is the significant course for efficient oil-adsorbing materials to avert the spread of oil spills and reduce ecological devastation. In this work, the adsorption kinetic curves of the rGO@PU foam for various oils and organic solvents are shown in Fig. 5(a). The 3D bar shown in Fig. 5 (b) shows the adsorption capacity of three different hydrocarbons—petrol, diesel, and mobil—over a range of adsorption cycles, from cycle 1 to cycle 20. Petrol exhibits the highest adsorption capacity, reaching nearly 40.5 g/g in each cycle, with minimal variation, indicating strong and consistent adsorption performance. Diesel follows with an adsorption capacity of around 35.2 g/g, which also remains stable throughout the cycles. Mobil shows the lowest adsorption capacity, stabilizing at approximately 22.6 g/g, but still makes no compromises across the cycles. The uniformity of adsorption capacity for all three hydrocarbons across multiple cycles suggests that the adsorbent material used is durable and effective for repeated use without significant degradation in performance. This stability is particularly important in applications where repeated adsorption-desorption processes are necessary. The differences in adsorption capacity between the hydrocarbons likely result from their varying molecular characteristics, with Petrol, a lighter hydrocarbon, having the highest adsorption capacity, while the heavier Mobil shows a lower capacity. This insight highlights the rGO@PU foam’s effectiveness for multiple uses and the varying adsorption behaviour based on hydrocarbon properties. The foam demonstrates high oil adsorption efficiency; however, as time progresses, the equilibrium is achieved as the adsorption sites within the pores of the foam are occupied, resulting in saturation beyond which no uptake occurs, as shown in Fig. S4. It is recognised that depending on the densities of oils and solvents, they occupy the top or bottom surface of the water, which influences oil spill cleanup. Here, diesel and chloroform with two different densities are selected as light and heavy oil, respectively to demonstrate the oil spill clean-up from the oil-water mixture. Fig. 6 (a–c) shows the utilization of rGO@PU foam for the removal of diesel at the surface of the water, whereas Fig. 6 (d-f) displays the chloroform removal from the bottom of the water. When the oil adsorption process is complete, the oil-loaded foam can float on the water surface but not sink into the water either in the diesel-water mixture or in the chloroform-water mixture, suggesting its outstanding adsorption selectivity and buoyancy. These results clearly show that the rGO@PU foam possesses an excellent adsorption selectivity of clean-up and exclusion of organic solvents of different densities. Conclusion This study demonstrates a feasible method to develop an oil-adsorbent material, i.e., rGO@PU foam, based on rGO coating on the skeleton of a commercially available PU foam through a dipping-dying process. GO is prepared from sugarcane bagasse and decorated on the skeletal structure of PU foam followed by the reduction process using hydrazine hydrate to finally fabricate rGO@PU foam. The rGO coating is introduced to induce the desired hydrophobicity and oleophilicity with reducing surface energy. The prepared rGO@PU foam shows very high effectivity towards superhydrophobic and superoleophilic properties for various sources of liquids and oils. Furthermore, the foam defines its superiority in various pH levels, temperatures and salt concentrations. In addition, rGO@PU foam demonstrates a very high selectivity in oil-water separation, potentially capable of swiftly absorbing both surface oils and submerged oils. It shows good removal capabilities for the oil droplets of diesel-in-water and chloroform-in-water mixture. Therefore, the superhydrophobic/superoleophobic rGO@PU could be a promising sorbent candidate for addressing large-scale applications in oil spills and chemical leak clean-up operations. Declarations The authors declare that they have no financial interests. Acknowledgements The authors would like to thank the Science and Engineering Research Board (SERB), India, the CSIR-Institute of Minerals and Materials Technology, India, via Research Projects SRG/ 2020/000329, GAP-404 and OLP-128 for the financial support. The authors acknowledge the Central Characterization Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, India, for their support in the characterization of materials. Author Contributions The manuscript was written through the contributions of all authors. All authors have given approval for the final version of the manuscript. Monami Mukherjee: Methodology, Conceptualization, Preparation of the test samples, Experiment, Investigation, Data processing and handling, Data curation, Writing and preparation of original draft Anita Mallick : Experiment, Conceptualization, Data processing and handling, Formal analysis, original draft review. K. Bharati Pradhan: Writing and preparation of draft. Chinmayee Dash: Formal analysis, writing- proof reading, Benadict Rakesh: Resources, Writing- Reviewing and Editing. Kamatchi Jothiramalingam Sankaran : Supervision, Methodology, validation, Writing- Reviewing and Editing, Conceptualization. Data availability Statement Data are available from the corresponding author upon request References Z. Li, D. Guo, Y. Liu, H. Wang, and L. Wang, “Recent advances and challenges in biomass-derived porous carbon nanomaterials for supercapacitors,” 2020. doi: 10.1016/j.cej.2020.125418. T. D. Nguyen, M. T. N. Nguyen, and J. S. Lee, “Carbon-Based Materials and Their Applications in Sensing by Electrochemical Voltammetry,” 2023. doi: 10.3390/inorganics11020081. D. Holmannova, P. Borsky, T. Svadlakova, L. Borska, and Z. Fiala, “Carbon Nanoparticles and Their Biomedical Applications,” 2022. doi: 10.3390/app12157865. J. Deng, M. Li, and Y. 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Saikia, “Graphene/Graphene Derivatives from Coal, Biomass, and Wastes: Synthesis, Energy Applications, and Perspectives,” 2022. doi: 10.1021/acs.energyfuels.2c00976. T. Li, R. Ma, X. Xu, S. Sun, and J. Lin, “Microwave-induced preparation of porous graphene nanosheets derived from biomass for supercapacitors,” Microporous and Mesoporous Materials , vol. 324, 2021, doi: 10.1016/j.micromeso.2021.111277. F. Zhou et al. , “Direct Plasma-Enhanced-Chemical-Vapor-Deposition Syntheses of Vertically Oriented Graphene Films on Functional Insulating Substrates for Wide-Range Applications,” 2022. doi: 10.1002/adfm.202202026. L. Ge et al. , “A review of comprehensive utilization of biomass to synthesize carbon nanotubes: From chemical vapor deposition to microwave pyrolysis,” 2024. doi: 10.1016/j.jaap.2023.106320. R. Ikram, B. M. Jan, and W. Ahmad, “Advances in synthesis of graphene derivatives using industrial wastes precursors; prospects and challenges,” 2020. doi: 10.1016/j.jmrt.2020.11.043. X. 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Tan, and T. Liu, “Bio-Based Aerogel Based on Bamboo, Waste Paper, and Reduced Graphene Oxide for Oil/Water Separation,” Langmuir , vol. 38, no. 10, 2022, doi: 10.1021/acs.langmuir.1c02821. M. Mukherjee, S. K. Ghadei, B. Rakesh, U. Balaji, R. Sakthivel, and K. J. Sankaran, “Fluorine-Free Sustainable Three-Dimensional Superhydrophobic and Superoleophilic Robust Foam for Efficient Oil/Water Separation,” ACS Applied Engineering Materials , vol. 2, no. 2, 2024, doi: 10.1021/acsaenm.3c00626. M. Xu et al. , “Multifunctional 3D polydimethylsiloxane modified MoS2@biomass-derived carbon composite for oil/water separation and organic dye adsorption/photocatalysis,” Colloids Surf A Physicochem Eng Asp , vol. 637, 2022, doi: 10.1016/j.colsurfa.2022.128281. L. Fan et al. , “In situself-foaming preparation of hydrophobic polyurethane foams for oil/water separation,” New Journal of Chemistry , vol. 45, no. 31, 2021, doi: 10.1039/d0nj05208f. G. Lamour et al. , “Contact angle measurements using a simplified experimental setup,” J Chem Educ , vol. 87, no. 12, 2010, doi: 10.1021/ed100468u. A. F. Stalder, T. Melchior, M. Müller, D. Sage, T. Blu, and M. Unser, “Low-bond axisymmetric drop shape analysis for surface tension and contact angle measurements of sessile drops,” Colloids Surf A Physicochem Eng Asp , vol. 364, no. 1–3, 2010, doi: 10.1016/j.colsurfa.2010.04.040. L. Qiu, Y. Sun, and Z. Guo, “Designing novel superwetting surfaces for high-efficiency oil-water separation: Design principles, opportunities, trends and challenges,” 2020. doi: 10.1039/d0ta02997a. T. Thanh Doan Nguyen et al. , “In-depth understanding of the photoreduction of graphene oxide to reduced-graphene oxide on TiO2 surface: Statistical analysis of X-ray photoelectron and Raman spectroscopy data,” Appl Surf Sci , vol. 581, 2022, doi: 10.1016/j.apsusc.2021.152325. A. C. Ferrari and J. Robertson, “Resonant Raman spectroscopy of disordered, amorphous, and diamondlike carbon,” Phys Rev B Condens Matter Mater Phys , vol. 64, no. 7, 2001, doi: 10.1103/PhysRevB.64.075414. W. Choi, A. Tuteja, J. M. Mabry, R. E. Cohen, and G. H. McKinley, “A modified Cassie-Baxter relationship to explain contact angle hysteresis and anisotropy on non-wetting textured surfaces,” J Colloid Interface Sci , vol. 339, no. 1, 2009, doi: 10.1016/j.jcis.2009.07.027. M. Yang et al. , “Superhydrophobic/superoleophilic modified melamine sponge for oil/water separation,” Ceram Int , vol. 49, no. 7, 2023, doi: 10.1016/j.ceramint.2022.12.001. H. Yan et al. , “Engineering polydimethylsiloxane with two-dimensional graphene oxide for an extremely durable superhydrophobic fabric coating,” RSC Adv , vol. 6, no. 71, 2016, doi: 10.1039/c6ra14362h. X. Yun, Z. Xiong, Y. He, and X. Wang, “Superhydrophobic lotus-leaf-like surface made from reduced graphene oxide through soft-lithographic duplication,” RSC Adv , vol. 10, no. 9, 2020, doi: 10.1039/c9ra10373b. S. Park, J. An, J. R. Potts, A. Velamakanni, S. Murali, and R. S. Ruoff, “Hydrazine-reduction of graphite- and graphene oxide,” Carbon N Y , vol. 49, no. 9, 2011, doi: 10.1016/j.carbon.2011.02.071. Schemes Scheme 1 is available in the Supplementary Files section Supplementary Files Scheme1.png Scheme 1. Schematic representation of the fabrication of rGO@PU foam. Supportinginformation.docx Cite Share Download PDF Status: Published Journal Publication published 18 Jun, 2025 Read the published version in Waste and Biomass Valorization → Version 1 posted Reviewers agreed at journal 21 Mar, 2025 Reviewers invited by journal 21 Mar, 2025 Editor invited by journal 22 Feb, 2025 Editor assigned by journal 16 Feb, 2025 First submitted to journal 14 Feb, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6034955","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":432242921,"identity":"ce7711ab-8e55-4800-85b3-a6fb2e5f86ad","order_by":0,"name":"Kamatchi Jothiramalingam Sankaran","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA90lEQVRIie3QsWoCMRzH8R8I7fIH10jK+Qp/ERQp+CyK0ClHuztUl7r4AIIv4SSOoUKzxD2lHe64oavFqdihd9hKSzE6OuQLl3BJPuQ4IBQ6wwR0PhYPSlrvlzunkYtOPvEpBD+EiuN8/MMqQ5Nu7mz7tjwdvz8+q080R6ME6eIwkbB1OXG91uR1NVvGc8aVtYyuPUwiWEhalxgu3hEhFNB98BGTbWl9z1Wnkh2pviVeIqEbktyS2Sl835L/Ax+pDGzjmqzhmrvhnNRJkGLtI8KZ7IWe+hy5XraJ51EkLk2afngIhP77TsWg/5/7VXng3Q6FQqEQ8AU6LFZZgkqQ1gAAAABJRU5ErkJggg==","orcid":"","institution":"CSIR-IMMT: Council of Scientific and Industrial Research Institute of Minerals and Materials Technology","correspondingAuthor":true,"prefix":"","firstName":"Kamatchi","middleName":"Jothiramalingam","lastName":"Sankaran","suffix":""},{"id":432242922,"identity":"90c4229b-6d36-4576-95e1-9b725aa755df","order_by":1,"name":"Monami Mukherjee","email":"","orcid":"","institution":"CSIR IMMT: Council of Scientific and Industrial Research Institute of Minerals and Materials Technology","correspondingAuthor":false,"prefix":"","firstName":"Monami","middleName":"","lastName":"Mukherjee","suffix":""},{"id":432242923,"identity":"cd1b64d4-e675-4590-a322-472d3f44aa71","order_by":2,"name":"Anita Mallick","email":"","orcid":"","institution":"CSIR-IMMT: Council of Scientific and Industrial Research Institute of Minerals and Materials Technology","correspondingAuthor":false,"prefix":"","firstName":"Anita","middleName":"","lastName":"Mallick","suffix":""},{"id":432242924,"identity":"eed7affd-609d-41d7-adae-bbe33b4b3f21","order_by":3,"name":"K. Bharati Pradhan","email":"","orcid":"","institution":"CSIR IMMT: Council of Scientific and Industrial Research Institute of Minerals and Materials Technology","correspondingAuthor":false,"prefix":"","firstName":"K.","middleName":"Bharati","lastName":"Pradhan","suffix":""},{"id":432242925,"identity":"cb96a6af-4d55-43b9-addf-b90069d727f7","order_by":4,"name":"Chinmayee Dash","email":"","orcid":"","institution":"CSIR-IMMT: Council of Scientific and Industrial Research Institute of Minerals and Materials Technology","correspondingAuthor":false,"prefix":"","firstName":"Chinmayee","middleName":"","lastName":"Dash","suffix":""},{"id":432242926,"identity":"d0bcf227-39aa-45dc-b8b2-d593689c19ab","order_by":5,"name":"Benadict Rakesh","email":"","orcid":"","institution":"CSIR-IMMT: Council of Scientific and Industrial Research Institute of Minerals and Materials 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inset.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6034955/v1/3c0052b72a8f5cace91e78c2.png"},{"id":79658217,"identity":"a1a132ae-56fd-409c-a6d9-4411b3b66224","added_by":"auto","created_at":"2025-04-01 09:12:12","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":89426,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Raman spectrum of carbonized sugar cane bagasse, GO, rGO, (b) represent the ID/IG ratio, defect density and the distance between the defects.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6034955/v1/cf5ed849a15cce3356258d57.png"},{"id":79658218,"identity":"61c41d11-0947-44e2-8593-6d50fff171cb","added_by":"auto","created_at":"2025-04-01 09:12:13","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":201053,"visible":true,"origin":"","legend":"\u003cp\u003e(a1-a3) represents the state of three different periods of water droplet adherence on the rGO-coated foam substrate, (b) represents the wettabilityperformance of the rGO@PU foam for mango juice, tea, soya sauce, milk, tomato sauce, and glycerine, (c1-c3) OCA of rGO@PU.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6034955/v1/6eec2d8957c9228f8f9aeb3e.png"},{"id":79658221,"identity":"979f79ab-fb4f-4cb4-9728-991f79cfcb26","added_by":"auto","created_at":"2025-04-01 09:12:13","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":113361,"visible":true,"origin":"","legend":"\u003cp\u003e(a) domineering effect of superhydrophobic nature, which is extremely resistant to wetting by lipids, (b) effect of pH, (c) temperature, (d) salt concentration.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6034955/v1/4daf7b162918008ed4e636dc.png"},{"id":79658226,"identity":"6475d89c-6434-4891-bc8e-f29ec2ac8127","added_by":"auto","created_at":"2025-04-01 09:12:13","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":119659,"visible":true,"origin":"","legend":"\u003cp\u003e(a) adsorption capacity of various oils and organic solvents of rGO@PU foam, (b) adsorption capacity of rGO@PU foam up to 20 cycles.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6034955/v1/26a6577c96d33729c5487b29.png"},{"id":79658225,"identity":"2e27ab54-3046-4d2d-a2c3-a5841baa888c","added_by":"auto","created_at":"2025-04-01 09:12:13","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":237439,"visible":true,"origin":"","legend":"\u003cp\u003e(a-f) Cleaning of oils from the surface and underwater using rGO@PU foam.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6034955/v1/25b560367251d7a85890b63b.png"},{"id":85231454,"identity":"00a68e95-6f5c-44e5-84f1-d80ff533445f","added_by":"auto","created_at":"2025-06-23 16:08:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1824457,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6034955/v1/af619d4d-310c-482b-ad38-86c36c3478ff.pdf"},{"id":79658224,"identity":"a5fa3bbd-ef4d-410f-b6ac-0b17d519f208","added_by":"auto","created_at":"2025-04-01 09:12:13","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":317665,"visible":true,"origin":"","legend":"\u003cp\u003eScheme 1. Schematic representation of the fabrication of rGO@PU foam.\u003c/p\u003e","description":"","filename":"Scheme1.png","url":"https://assets-eu.researchsquare.com/files/rs-6034955/v1/b7a37a0899ad1970e56b9f97.png"},{"id":79658727,"identity":"c27a2747-bd38-46af-841b-ba615776825e","added_by":"auto","created_at":"2025-04-01 09:20:13","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":1585014,"visible":true,"origin":"","legend":"","description":"","filename":"Supportinginformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6034955/v1/a15ce2bb28d49c372316efb0.docx"}],"financialInterests":"","formattedTitle":"Preparation of superhydrophobic/superoleophilic sugarcane bagasse-derived reduced graphene oxide anchored foam with application in oil/water separation","fulltext":[{"header":"Statement of Novelty","content":"\u003cp\u003eThis research presents a novel, sustainable, and cost-effective approach for oil-water separation by utilizing sugarcane bagasse-derived graphene oxide (GO) to fabricate reduced graphene oxide-coated polyurethane foam (rGO@PU). Unlike conventional methods that rely on expensive and non-renewable materials, this study pioneers the valorization of agricultural bio-waste, specifically sugarcane bagasse, to synthesize advanced carbon nanomaterials. The facile dip-coating and reduction process ensures uniform deposition of rGO, imparting the foam with exceptional superhydrophobic (WCA of 158.96\u0026deg;) and superoleophilic (oil contact angle ~0\u0026deg;) properties. The rGO@PU foam demonstrates superior adsorption capacities (25-50 g/g) across various oils and effectively separates both heavy and light oils from water. The integration of bio-waste valorization, low-cost fabrication, and high-performance oil adsorption showcases a significant advancement in sustainable material design for environmental remediation, particularly in addressing large-scale oil spill challenges.\u003c/p\u003e"},{"header":"Introduction","content":"\u003cp\u003eThe global interest in achieving sustainability and circular economy has boosted the demand for utilizing biomass wastes for synthesizing nanomaterials in order to align with the concept of resource efficiency and waste management. While the disposal of biomass wastes challenges the existing financial as well as environmental costs, their conversion into valuable functional and energy materials alleviates the cost and presents an opportunity to create a closed-loop system. Biomass or agricultural wastes, which are several and abundant in nature and a renewable source, are rich in carbon and provide a sustainable foundation for developing versatile advanced carbon-based materials. The intrinsic hierarchical structural diversity of biomass and organic composition provides a natural template for producing various carbon derivatives with tailored properties.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCarbon, a fundamental element in the periodic table, is known as the foundation of all life forms and the cornerstone of modern science owing to its unparalleled versatility and structural diversity. Its unique electronic configuration enables it to form a stable and complex bond with other elements as well as itself, leading to diverse allotropic forms and derivatives from conventional graphite and diamond to advanced nanostructured graphene, carbon nanotubes (CNT) and fullerenes [1].\u0026nbsp; \u0026nbsp;These carbon-based functional materials possess remarkable properties including chemical and high thermal resistance, robust mechanical properties, lightweight, flexible, high thermal and electrical conductivity, making them indispensable in several scientific and industrial applications [2-3]. The key advantages of valorizing biomass waste in the development of carbon nanomaterials include their high carbon content, high abundancy, versatile molecular structure, diverse feedstock, more active sites, well-developed porous structures with enhanced surface area as well as maintain carbon neutrality [4-5]. However, the major challenges posed by such green feedstock are moderate or low processing yield, versatility in chemical composition and energy consumption [5]. \u0026nbsp;Out of various carbon allotropes derived from biomass wastes, graphene stands as an extraordinary two-dimensional material (2D) that embraces\u0026nbsp;\u0026nbsp;\u0026nbsp;hybridization with a single layer of carbon atoms assembled in a hexagonal lattice. The isolation of graphene marked a revolutionary advancement, unravelling its unique properties like high surface area, high percolation threshold, high mechanical strength (up to 1000 GPa), high thermal (4840-5300\u0026nbsp;\u0026nbsp;) and electrical (2 \u0026times;10\u003csup\u003e5\u003c/sup\u003e \u0026nbsp;) [6-7]. The derivative of graphene classified as graphene oxide (GO) and reduced graphene oxide (rGO) expands its utility through variable interface chemistry, enabling their applications in electronics, drug delivery, sensors, adsorbents and photocatalytic activity [8]. GO has attracted significant attention from the scientific community and is preferred over reduced rGO in several applications owing to its high oxygen-containing functional groups, high dispersion stability and lower defect density [9]. In contrast to graphene and rGO, GO is highly dispersive in water due to its oxygen-containing polar groups and increased surface charge that facilitate the interaction with water- or solvent-based suspensions [10]. In the conventional process, GO can be synthesized by the oxidation process of graphite that forms graphite oxide followed by the exfoliation of graphite oxide to GO. However, carbon-rich biomass feedstock needs to undergo graphitization before oxidation and this step involves either physical or chemical processing. Although, biomass-derived carbon nanomaterials are a safer choice to cover the discussion regarding carbon dioxide (\u0026nbsp;) emission and non-renewability, the challenges included in the synthesis process are mostly low-level products without fine molecular structure. Several methods are established to synthesize graphene from biomass including mechanical exfoliation [11], chemical exfoliation [12], chemical vapor deposition (CVD)[13] , microwave process [14] and plasma-enhanced CVD (PECVD) [15]. However, every synthesis route exhibits some limitations and challenges depending upon the application of graphene. For example, the mechanical exfoliation route generates a low yield of graphene and the exfoliated layers may have varying thickness and properties. Chemical exfoliation involves several acids and oxidizing agents that can introduce additional irrelevant functional groups and quite not always eco-friendly. The CVD route, which is excessively utilized to produce graphene, poses challenges that involve high-cost equipment with high-purity precursor gas along with large-area deposition [16- 17]. Furthermore, compared to conventional thermal treatment, the microwave technique supports biomass for uniform heat transfer and rapid heating; however, it has a low energy efficiency due to the mismatching between poor dielectric properties of biomass and microwave power [16- 18]. PECVD is reported as an eco-friendly route to exfoliate graphene into its derivatives; it is limited by its equipment complexity [16]. Out of the above-mentioned techniques, pyrolysis is reported as a convenient method to derive high graphitic carbon materials under high temperatures (300-1200\u0026deg;C) and inert atmosphere. Additionally, this bottom-up approach is viable for a large variety of biomass precursors and minimization of greenhouse to facilitate sustainability. Various agricultural waste feedstock has been investigated for their potential in carbon nanoparticles, such as jute, grass, sugarcane, corn stalk, rice husk and straw, wheat straw, bamboo, fruit wastes, coconut shell, groundnut shell, etc. Among them, sugarcane bagasse (SB) is hugely disposed of by juice makers and industries. India is the second largest sugarcane producer around the globe, produces 350 Mt of bagasse annually, and is projected to reach a value of 100-125 Mt by 2030 [19]. The carbon nanoparticle derived from SB exhibits a unique porous structure, large surface area, high adsorption capacity and larger pore volume making it a potential candidate for several advanced applications [20]. One such critical exploration is oil-water separation, where the superhydrophobic and superoleophilic properties of efficient and sustainable materials play a crucial role. The water pollution arising from oil spillage, development of oil production and oil wastewater generated from various industrial processes poses a grave threat to marine species, human health and national development. Recent highlights surface on the oil spill incident in Chennai, India, originating from the Chennai Petroleum Corporation Ltd (CPCL) that has reported to cross at least 20 sq. km into the sea, posing a major threat to aquatic life. \u0026nbsp;A variety of traditional methods have been delivered for oil-water separation such as skimming, gravity separation, air flotation, flocculation, centrifugation and filtration [21- 22]. However, these methods are limited by their low processing efficiency, high operational cost and ineffectiveness for oil-water emulsion separation. Among these, adsorption offers several advantages, including highly efficient selective separation, separation of oil from oil-water emulsion, and eco-friendly, making it a preferred method of the separation process. \u0026nbsp;The growing demand for materials of separate oils and organic contaminants has attracted porous oil-absorbing materials such as graphene, hydrophobic nano silica, polydopamine, CNT, etc. However, the practical applicability of these materials is hampered by their cost, environmental incompatibility, low stability and poor usability [23] . As an alternative, foam-based three-dimensional (3D) effective adsorbents have been widely used for oil/water separation due to their comprehensive benefits such as low density, 3D porous network and special wettability. Various 3D porous materials such as functional sponges, carbon aerogels, nickel foam and resin foams have been studied; however, sponges particularly garnered significant attention for their high efficacy towards oil adsorption capacity [24- 25]Among various foaming materials, polyurethane (PU) foam captured substantial attention due to its larger surface area, good mechanical strength, lightweight, high permeability and low cost [24- 26]. However, commercially available PU foam exhibits hydrophilic property that makes it less effective for selective adsorption of oil. Therefore, the structural modification of these PU foams is a prerequisite step to transform the surface into hydrophobic and oleophilic. \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHerein, the sugarcane bagasse-derived rGO anchored PU (rGO@PU) foam is prepared by a facile method and reported for the selective adsorption of oil from the oil-water mixture. The bottom-up pyrolysis route is employed to derive GO from sugarcane bagasse to eliminate volatile and hydrophilic compounds. The commercial PU foams are dispersed with GO and then dipped in an organic substrate to induce rGO. Sugarcane bagasse-derived GO serves as a scaffold to support the PU foam. In addition, introducing organic substrate that produces amine groups during the reduction process of GO to rGO helps to construct superhydrophilic and superoleophilic surfaces for stable and efficient repelling of water and adsorption of several oils. The rGO@PU foam shows superhydrophobic behavior in different salt concentrations, temperatures and pH, indicating the exceptionally strong and stable attribute of rGO@PU foam. The tunable structural, defect characteristic and the surface properties of rGO@PU foam significantly influence its wettability and adsorption properties. The superoleophilic rGO@PU foam exhibit excellent oil affinity and the presence of rGO related functional group on the foam enhances adsorption capacity, making it highly favourable for effective oil-water separation application. In consequence, this work offers a green and sustainable development of graphene based materials from biomass waste for the effective exploitation of oil/water separation. \u0026nbsp;\u0026nbsp;\u003c/p\u003e"},{"header":"Experimental Methods","content":"\u003cp\u003e\u003cstrong\u003eMaterials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSugarcane bagasse was taken from a sugar milling industry in Bhubaneswar, Odisha, India. Pure chemicals such as tetrahydrofuran (THF), hydrazine hydrate 80%, acetone, ethanol, sodium chloride (NaCl), isopropanol, toluene, butanol and hexane chloroform were procured from Central Drug House (CDH) fine chemicals Pvt. Ltd., New Delhi and polyurethane (PU) foam was purchased from Neustro Poly Products Pvt Ltd. All chemicals were used without further refinement. Oils such as pump oil, hydraulic oil, kerosene, mobile, paraffin, vegetable oil, engine oil, coconut oil, mustard oil, terpene, petrol, diesel and crude oil were purchased from Bhubaneswar, India. Double distilled water was used for all synthesis and treatment processes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of GO from sugarcane bagasse\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe sugarcane bagasse was chopped into small pieces and thoroughly washed with deionized (DI) water. It was then dried in a hot air oven at 100\u0026deg;C for 4 h. The dried bagasse was pulverized and sieved to obtain particles of approximately 25 microns. The pulverizing phase decreased mean particle size and increased specific surface area. The sieved sample was carbonized and subsequently annealed in a tube furnace under an inert atmosphere of argon gas at 800\u0026deg;C for 5h to obtain GO. The annealing temperature and thermal stability for the carbonized sample were determined from the thermal degradation profile of TGA and crystallization temperature observed in DSC, as shown in Fig. S1. Finally, the GO sample was allowed to cool in an argon atmosphere to reach room temperature.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFabrication of rGO@PU foam\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBefore treatment, the original PU foam was cut into small cubes, each measuring 1 \u0026times; 1 \u0026times; 1 cm\u0026sup3;. The foam cubes were then ultrasonically cleaned for 45 minutes in THF, followed by additional cleaning in ethanol and DI water to remove any external stains and impurities. After the cleaning process, the foams were dried in a hot-air oven at 80\u0026deg;C for 3 h. To prevent moisture adsorption, the cleaned foams were immediately transferred to an airtight container upon removal from the oven. To prepare the GO suspension, 0.03 g of GO derived from sugarcane bagasse was dispersed in 10 mL of DI water using ultrasonic treatment for 1 h to avoid any kind of accumulation. The cleaned PU foam was then gradually immersed in the GO suspension and allowed to soak for 1 h under ambient conditions. After soaking, the foams were dried at 80\u0026deg;C in a hot-air oven for 4 h to eliminate any additional water, resulting in GO-coated PU foam. The coated foam was subsequently immersed in 25 mL of 80% hydrazine hydrate and placed in an oven to facilitate the reduction of GO to rGO. After the reduction process, the foam was rinsed with DI water to eliminate residual hydrazine hydrate and dried again in the hot-air oven at 90 \u0026deg;C for 6 hours, yielding the final rGO@PU foam.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCharacterization\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Raman characteristics were investigated using a Renishaw in Via micro-Raman spectrometer (\u0026lambda; =532 nm) to know the crystalline quality of the materials. The structural morphology of the materials was observed using a Zeiss Evo 15 Field emission scanning electron microscope (FESEM) equipped with an energy-dispersive X-ray (EDX) detector. To prepare the sample for the FESEM, first, a slice of foam was taken and the foam\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003ewas placed on a copper tape fixed on the sample holder of the SEM. The sample was then subjected to gold sputtering in order to avoid charging. The conditions of SEM measurements are a sputter ion pump (i) 2.61 \u0026times; 10\u0026minus;8 Pa;\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e(ii) 4.2 \u0026times; 10\u0026minus;7 Pa; vacuum: 1.8 \u0026times; 10\u0026minus;4 Pa; beam power (emission current): 42.60 \u0026mu;A; accelerator volt: 15 kV; mode\u0026minus;secondary electron detector; and working distance: 8 mm. The microstructural features of the materials were observed using JEOL transmission electron microscopy (TEM) equipped with energy-dispersive X-ray. The selected area electron diffraction (SAED) pattern was taken under 20 cm camera length and 1000 \u0026mu;m aperture in TEM. The TEM samples of the rGO composite were prepared by the extraction of rGO from PU foam in an ethanol solution using the ultrasonication process and by drop-casting on a TEM Cupper (Cu) grid.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eContact angle and oil-water separation measurements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003c/strong\u003eThe samples were analyzed for their contact angle using a digital microscope camera. A 5 \u0026mu;L water droplet was placed as a probe liquid on the sample surface, and the droplet\u0026apos;s image was captured. ImageJ software with the drop-analysis plugin was used to determine the contact angle \u0026nbsp;[27-28]. The standard error of the contact angle measurement was calculated from five readings taken at different locations on the samples. Kerosene and chloroform were used to demonstrate oil/water separation on the surface and underwater. The weight of the rGO@PU foam was measured. The foam was then immersed in oil and various organic solvents for 1 minute, and its weight was measured again to determine the adsorption capacity. The adsorption capacities of different oils were calculated using a specific equation [29]\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"529\" height=\"35\"\u003e\u003c/p\u003e\n\u003cp\u003ewhere m\u003csub\u003e1\u003c/sub\u003e and m\u003csub\u003e2\u003c/sub\u003e are the weight of the foam before and after adsorption of oils/organic solvents, respectively.\u0026nbsp;\u003c/p\u003e"},{"header":"Results And Discussion","content":"\u003cp\u003e\u003cstrong\u003eStructural analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFig. 1(a) shows the FESEM micrographs of the rGO@PU foam. The 3D structure with the interconnected pores. These pore structures in the foams facilitate the adsorption and internal transport of the rGO to act as a hydrophobic/oleophobic substrate. Furthermore, the high-magnified FESEM micrograph shown at the inset of Fig. 1(a) illustrates the deposition of rGO on the skeleton of PU foam, which signifies a rough, wrinkled and homogenous coating of rGO existed on PU foam. The surface of PU foam is closely packed by those rGO, creating a multiscale roughness structure, which depicts the transition of hydrophilic PU foam to hydrophobic one. Fig. S3 shows the quantification of O and C by using EDX. Moreover, Fig.1(b) shows the HRTEM micrograph of the rGO with wrinkled structures, and the inset shows the SAED pattern of the ring-structured rGO pattern.\u003c/p\u003e\n\u003cp\u003eRaman spectroscopy is an indispensable technique used to investigate the degree of disorderness, crystallinity and number of layers present in carbon-based materials. Here, the spectra are collected for the carbonized sugarcane bagasse, sugarcane-derived GO and rGO-coated foam and the peaks are fitted with 3 Gaussian bands Fig.2 (a). All three samples show signature D and G bands at 1360 cm\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003eand 1590 cm\u003csup\u003e-1\u003c/sup\u003e attributed to the in-plane vibration of carbon atoms in the graphitic lattice and signify the characteristic peak of the carbon-contained materials [30] The appearance of the G band probe the formation of sp\u003csup\u003e2\u003c/sup\u003e-hybridized carbon network that caused due to in-plane vibration of C-C stretching [31], where D-band indicates the density of structural defects and disorders. Out of the three samples shown, the GO spectrum exhibits a higher D-band intensity relative to the G-band, indicating a comparatively higher degree of distortions in the localized 2-D structures. Moreover, the wide spectrum and the outspread area under D-bands peaks convey the formation of graphitic amorphous phase due to sp\u003csup\u003e3\u003c/sup\u003e carbon content upon oxidation effect introduced due to thermal forces. The presence of the sp3 bond introduces distortion and defects in regular sp2 lattice, leading to a higher defect density. After a thorough observation of the nature of peaks, further information was extracted from the fitting parameters to evaluate the degree of disorderness, defect density and crystallite size. The degree of disorderness and crystallite size in the carbon atoms can be evaluated by estimating the intensity ratio of D and G band peaks. Moreover, the defect density and the distance between the defects are also calculated and all together presented in Fig. 2(b). The empirical estimation suggested that GO (0.96) and rGO (0.88) exhibit comparatively higher \u0026nbsp; value than carbonized sugarcane bagasse and amounts to less than 1.00 ( \u0026lt;1.00). This observation is attributed to a greater degree of lattice distortion of sp\u003csup\u003e3\u0026nbsp;\u003c/sup\u003ehybridization due to oxidized graphene. Briefly explains, the greater the ratio of two intensities, the more will be disordered of the morphology of the sample. Besides, the lateral crystallite size 13.27 ( ) is observed to be higher in both GO and rGO cases with lower defect density, suggesting a nanocrystalline structure of graphitic phase with fewer defects. These above-described results confirm the alternation of the structural integrity of the carbonized sugarcane bagasse upon the thermal event and thermal event-assisted reduction, making it suitable for the tailored oil-water separation application.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eWetting Characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFigure 3 shows a series of optical micrograph images of rGO@PU obtained from contact angle measurement. Fig. 3(a1) - (a3) represents the state of three different periods of water droplet adherence on the rGO-coated foam substrate. It can be seen that the water droplet adheres to the foam substrate relatively constantly over time. The maximum time is recorded for 30 min with a maximum WCA of 158.96\u0026deg;. Such value remains the same in all three-time frames and indicates the superhydrophobic behaviour of preparing the rGO-coated foam. It also signifies the force of adhesion between the water droplet and the surface of the sponge is relatively excellent.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFig. 3(b) reveals the wettability performance of the rGO@PU foam with a 5 \u0026mu;L drop of mango juice, tea, soya sauce, milk, tomato sauce, and glycerine. In each of the cases, the contact angle of the rGO@PU foam is recorded to be 158.96\u0026deg;, indicating the domineering effect of superhydrophobic nature, which is extremely resistant to wetting by lipids. Fig. 4(a). It affirms the potential application of the rGO@PU foam for requiring lipid repellence. The uniform coating of the rGO throughout the network of the foam enhances the surface roughness of materials, which is evident from FESEM \u0026nbsp; micrographs. This roughness plays a key role for trapping air pockets that reduces solid-liquid contact area, leading to superhydro phobicity. This characteristic follows the Cassie-Baxter non-wetting phenomenon, [32] where air pockets trapped within the rough surface contribute to the high-lipid contact angle, preventing lipids from penetrating the material. The functionalization during the reduction process of the foam introduces hydrophobic functional groups in the microstructure, hence achieving lower surface energy. The presence of these functional groups facilitates the interaction with various liquids, making the surface not only the water but also several organic solvents efficiently.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAdditionally, chemical firmness (varying pH, temperature, and salt concentration) experiments were carried out on the superhydrophobic rGO@PU\u0026nbsp;foam to evaluate its practical usability. Fig.4(b) shows the measured WCA values at pH values from 1-13. It is observed that the WCA values remain high across the range of pH levels, implying stable, superhydrophobicity regardless of exposure to strongly acidic and basic environments of the rGO@PU foam. The superhydrophobic properties of the prepared foam are further analysed under varying temperatures from 283 K to 373 K, as illustrated in Fig. 4(c). The WCA is observed to remain consistently high, above 150\u0026deg;, across a wide temperature range, indicating the material\u0026apos;s thermal stability to maintain water repellence regardless of temperature fluctuations. This stability across varying temperatures and pH levels underscores the robustness and suitability of the rGO@PU foam for applications in environments where thermal conditions and chemical exposures may vary significantly. In the next investigation, WCA on the surface of the foam is measured at different salt concentrations, ranging from 1 M to 7 M Fig. 4(d). The consistent high contact angles across all concentrations suggest that the superhydrophobic properties of the material are stable and unaffected by the presence of salts, even at low to high concentrations. Together, these results confirm the material robust and uniform water-repellent properties, making it suitable for applications requiring resistance to both a wide range of liquids and saline environments.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOleophilicity is a substantial parameter to study the oil/water separation that provides evidence of the performance of the adsorption of oils. In this case, the oil contact angle (OCA) is estimated by taking 5 \u0026mu;L oil as a probe liquid and dropped on the surface of the as-prepared rGO@PU foam. The optical micrographs from the contact angle are shown in Fig. 3(c). The oil droplet has made contact with the surface for 5 ms, as shown in the figure, however, it is quickly distorted and later spread over completely in 10 ms, as shown in Fig. 3 (c1-c3). The rGO coating and low energy of oils render the effective adsorption of oil into the microstructure of the foam and reveal the superoleophilic behaviour.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIt is valuable to know the impact of rGO in encouraging superhydrophobic and superoleophilic behaviour on PU foam. The superhydrophobicity of rGO@PU foam is ascribed to low surface energy formed by the coated rGO. When the GO nanosheet is enclosed on the foam skeleton, the high surface area of GO and strong accretion effect between the overlapping layers make the GO sheet stably wrap around the foam [33- 34]In addition, there is a strong van der Waals interaction between the GO and the skeleton of the PU foam, which causes an even and steady coating [35] The thermal behaviour of GO in the presence of hydrazine hydrate leads to the breakdown of oxygen-containing functional groups, facilitating the reduction of GO [36] Additionally, reduction lead to local sheet deformation and have a deoxygenating effect, which would enhance the great binding between the rough rGO sheets. The non-wetting behaviour of rGO@PU foam is due to the creation of the Cassie-Baxter surface with low surface energy, which forms an air gap between the surface and water. For comparison, we took pristine PU foams. The WCA, with corresponding SEM morphologies of these samples, is shown in Fig. S2. \u0026nbsp;The WCA, with Hence, rGO@PU foam displayed high water repellence. However, oils, due to their low surface energy, promoted the flow of rGO@PU foam, resulting in oleophilicity. Hence, when the rGO@PU foam is placed in the oil-water emulsion, the air in the holes of the foam is occupied by the oil due to the capillary effect, van der Waals force, and hydrophobic interaction, whereas the air pores of rGO@PU foam repel water. Therefore, the air-filled superhydrophobic foam is changed during the oil adsorption process into oil-filled foam, promoting quick oil adsorption.\u003c/p\u003e\n\u003cp\u003eFig. 5 (a) explains the adsorption capacities of various oils and solvents, highlighting significant differences across the rGO@PU foam. The adsorption capacity of rGO@PU foam to various oils and organic solvents is found to be in the range of 20\u0026ndash;60 g/g. \u0026nbsp;It is observed that oils and solvents with low viscosity, such as chloroform, butanol, acetone, petrol, and ethanol, show much higher adsorption capacity and get saturated in just 2.5 s. The highest adsorption capability is achieved by toluene (50.0 g/g) followed by isopropanol (45.7 g/g), ethanol (42.2 g/g), acetone (40), butanol (40.7 g/g) and terpene (40.6 g/g) than its weight. \u0026nbsp;The differences in adsorption behaviour are likely due to the varying physical and chemical properties of the substances, such as molecular size, viscosity, and polarity, which influence their interaction with the adsorbent material. This is due to the low viscosity of oils that promoted easy penetration into the low surface energy framework of rGO@PU foam. Whereas high viscous oils and solvents such as mustard oil, pump oil, hydraulic oil, and crude oils could be adsorbed and saturated within 8 to 10 s. This suggests that the adsorption mechanism is highly dependent on the nature of the adsorbate, and the faster adsorption rates observed for lighter hydrocarbons indicate more efficient interaction with the adsorbent rGO@PU foam.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOil/water separation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRapid adsorption is the significant course for efficient oil-adsorbing materials to avert the spread of oil spills and reduce ecological devastation. In this work, the adsorption kinetic curves of the rGO@PU foam for various oils and organic solvents are shown in Fig. 5(a). The 3D bar shown in Fig. 5 (b) shows the adsorption capacity of three different hydrocarbons\u0026mdash;petrol, diesel, and mobil\u0026mdash;over a range of adsorption cycles, from cycle 1 to cycle 20. Petrol exhibits the highest adsorption capacity, reaching nearly 40.5 g/g in each cycle, with minimal variation, indicating strong and consistent adsorption performance. Diesel follows with an adsorption capacity of around 35.2 g/g, which also remains stable throughout the cycles. Mobil shows the lowest adsorption capacity, stabilizing at approximately 22.6 g/g, but still makes no compromises across the cycles. The uniformity of adsorption capacity for all three hydrocarbons across multiple cycles suggests that the adsorbent material used is durable and effective for repeated use without significant degradation in performance. This stability is particularly important in applications where repeated adsorption-desorption processes are necessary. The differences in adsorption capacity between the hydrocarbons likely result from their varying molecular characteristics, with Petrol, a lighter hydrocarbon, having the highest adsorption capacity, while the heavier Mobil shows a lower capacity. This insight highlights the rGO@PU foam\u0026rsquo;s effectiveness for multiple uses and the varying adsorption behaviour based on hydrocarbon properties. The foam demonstrates high oil adsorption efficiency; however, as time progresses, the equilibrium is achieved as the adsorption sites within the pores of the foam are occupied, resulting in saturation beyond which no uptake occurs, as shown in Fig. S4. It is recognised that depending on the densities of oils and solvents, they occupy the top or bottom surface of the water, which influences oil spill cleanup. Here, diesel and chloroform with two different densities are selected as light and heavy oil, respectively to demonstrate the oil spill clean-up from the oil-water mixture. \u0026nbsp;Fig. 6 (a\u0026ndash;c) shows the utilization of rGO@PU foam for the removal of diesel at the surface of the water, whereas Fig. 6 (d-f) displays the chloroform removal from the bottom of the water. When the oil adsorption process is complete, the oil-loaded foam can float on the water surface but not sink into the water either in the diesel-water mixture or in the chloroform-water mixture, suggesting its outstanding adsorption selectivity and buoyancy. These results clearly show that the rGO@PU foam possesses an excellent adsorption selectivity of clean-up and exclusion of organic solvents of different densities.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study demonstrates a feasible method to develop an oil-adsorbent material, i.e., rGO@PU foam, based on rGO coating on the skeleton of a commercially available PU foam through a dipping-dying process. GO is prepared from sugarcane bagasse and decorated on the skeletal structure of PU foam followed by the reduction process using hydrazine hydrate to finally fabricate rGO@PU foam. The rGO coating is introduced to induce the desired hydrophobicity and oleophilicity with reducing surface energy. The prepared rGO@PU foam shows very high effectivity towards superhydrophobic and superoleophilic properties for various sources of liquids and oils. Furthermore, the foam defines its superiority in various pH levels, temperatures and salt concentrations. \u0026nbsp;In addition, rGO@PU foam demonstrates a very high selectivity in oil-water separation, potentially capable of swiftly absorbing both surface oils and submerged oils. It shows good removal capabilities for the oil droplets of diesel-in-water and chloroform-in-water mixture. Therefore, the superhydrophobic/superoleophobic rGO@PU could be a promising sorbent candidate for addressing large-scale applications in oil spills and chemical leak clean-up operations.\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThe authors declare that they have no financial interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank the Science and Engineering Research Board (SERB), India, the CSIR-Institute of Minerals and Materials Technology, India, via Research Projects SRG/ 2020/000329, GAP-404 and OLP-128 for the financial support. The authors acknowledge the Central Characterization Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, India, for their support in the characterization of materials.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe manuscript was written through the contributions of all authors. All authors have given approval for the final version of the manuscript. \u003cstrong\u003eMonami Mukherjee:\u0026nbsp;\u003c/strong\u003eMethodology, Conceptualization, Preparation of the test samples, Experiment, Investigation, Data processing and handling, Data curation, Writing and preparation of original draft \u003cstrong\u003eAnita Mallick\u003c/strong\u003e: Experiment, Conceptualization, Data processing and handling, Formal analysis, original draft review. \u003cstrong\u003eK. Bharati Pradhan:\u0026nbsp;\u003c/strong\u003eWriting and preparation of draft. \u003cstrong\u003eChinmayee Dash:\u003c/strong\u003e Formal analysis, writing- proof reading, \u003cstrong\u003eBenadict Rakesh:\u0026nbsp;\u003c/strong\u003eResources, Writing- Reviewing and Editing. \u003cstrong\u003eKamatchi Jothiramalingam Sankaran\u003c/strong\u003e: Supervision, Methodology, validation, Writing- Reviewing and Editing, Conceptualization.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eStatement Data are available from the corresponding author upon request\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZ. Li, D. Guo, Y. Liu, H. Wang, and L. Wang, \u0026ldquo;Recent advances and challenges in biomass-derived porous carbon nanomaterials for supercapacitors,\u0026rdquo; 2020. doi: 10.1016/j.cej.2020.125418.\u003c/li\u003e\n\u003cli\u003eT. D. Nguyen, M. T. N. Nguyen, and J. S. 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Ruoff, \u0026ldquo;Hydrazine-reduction of graphite- and graphene oxide,\u0026rdquo; \u003cem\u003eCarbon N Y\u003c/em\u003e, vol. 49, no. 9, 2011, doi: 10.1016/j.carbon.2011.02.071.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Schemes","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"waste-and-biomass-valorization","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wave","sideBox":"Learn more about [Waste and Biomass Valorization](http://link.springer.com/journal/12649)","snPcode":"12649","submissionUrl":"https://submission.nature.com/new-submission/12649/3","title":"Waste and Biomass Valorization","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Adsorption, educed graphene oxide, polyurethane foam, oil/water separation, superhydrophobic, super oleophilic, sugarcane bagasse","lastPublishedDoi":"10.21203/rs.3.rs-6034955/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6034955/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The conversion of bio-waste into carbon nanomaterials offers a sustainable and cost-effective approach to meet the growing demand for advanced functional materials and to treat the oil spill challenge in the massive water body. In this context, a sustainable, environment-friendly and efficient superhydrophobic/superoleophilic material is prepared by using sugarcane waste bagasse derived graphene oxide (GO) and functionalized to reduced graphene oxide (rGO) coated- polyurethane (PU) foam (rGO@PU) via a low-cost facile method for effective oil-water separation. The foam is dipped in the GO suspension followed by immersion in hydrazine hydrate to facilitate the reduction of GO to rGO. The scanning electron microscope (SEM) images illustrate the uniform deposition of rGO on the skeleton of PU foam. The rGO@PU foam shows a high repellency to water and affinity to various oil, with water contact angle (WCA) of 158.96° and oil contact angle of nearly 0°. Such non-wetting behaviour of the foam signifies the formation of Cassie-Baxter surface with low surface energy. Owing to its hierarchical pore structure, the adsorption capacities of rGO@PU foam for various oils are recorded in the range of 25-50 g/g. Furthermore, a demonstration is performed on the foam that successfully separated and recovered heavy oil like diesel and low oil like chloroform from the water. Hence, the GO/rGO@PU foam is evinced as an effective promising adsorbent material for oil spill cleanup.","manuscriptTitle":"Preparation of superhydrophobic/superoleophilic sugarcane bagasse-derived reduced graphene oxide anchored foam with application in oil/water separation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-01 09:12:08","doi":"10.21203/rs.3.rs-6034955/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-03-22T02:10:29+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-03-21T18:11:10+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Waste and Biomass Valorization","date":"2025-02-23T03:13:34+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-02-16T18:06:28+00:00","index":"","fulltext":""},{"type":"submitted","content":"Waste and Biomass Valorization","date":"2025-02-15T02:22:46+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"waste-and-biomass-valorization","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wave","sideBox":"Learn more about [Waste and Biomass Valorization](http://link.springer.com/journal/12649)","snPcode":"12649","submissionUrl":"https://submission.nature.com/new-submission/12649/3","title":"Waste and Biomass Valorization","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"cd131ba2-ca7c-4bb0-b128-464c5fa23ee0","owner":[],"postedDate":"April 1st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-06-23T16:05:34+00:00","versionOfRecord":{"articleIdentity":"rs-6034955","link":"https://doi.org/10.1007/s12649-025-03174-7","journal":{"identity":"waste-and-biomass-valorization","isVorOnly":false,"title":"Waste and Biomass Valorization"},"publishedOn":"2025-06-18 15:57:56","publishedOnDateReadable":"June 18th, 2025"},"versionCreatedAt":"2025-04-01 09:12:08","video":"","vorDoi":"10.1007/s12649-025-03174-7","vorDoiUrl":"https://doi.org/10.1007/s12649-025-03174-7","workflowStages":[]},"version":"v1","identity":"rs-6034955","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6034955","identity":"rs-6034955","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}