Effects of modified sugar cane and plantain pseudo-stem fibers for oil spill remediation

Abstract

This article presents the experimental results on the effects of surface functionalization of plantain pseudo-stem fiber (PF) and sugar cane fiber (SF) sorbents on the absorption of crude oil and the separation oil/water mixture. The modification involved coating the SF and PF with TiO₂, graphene oxide (GO), and stearic acid (SA). The fibers were cut and sonicated in hexane and ethanol in succession for ∼45 min and dried at 60 °C for 24 h. 0.5 g of PF and SF were bagged into 2 g empty tea bags. The GO and ethanol solutions of ∼3–5 mg/mL were coated onto the SF and PF and dried for 12 h and subsequently contacted with instant ocean salt and crude oil fractions. The results show that the SA, TiO₂ nanoparticles, and GO sheets contribute a large surface area and high surface roughness which provide excellent hydrophobicity. The modified SF and PF recorded ∼144° and ∼126° from ∼63° and ∼46° contact angles as well as ∼10.29 g/g and ∼5.77 g/g absorption respectively. The sorbent materials demonstrate crude oil and oil/water separation indicating a promising technique for oil spill remediation.

Keywords:

• Sorbent material
• plantain pseudo-stem fiber
• sugar cane fiber
• oil spill remediation
• hydrophobicity
• oleophilicity

REVIEWING EDITOR:

• Ian Phillip Jones, University of Birmingham, United Kingdom of Great Britain and Northern Ireland

SUBJECTS:

• Marine & Aquatic Science
• Environmental Management
• Environmental Studies
• Conservation – Environment Studies
• Material Science
• Materials Science
• Chemical Engineering
• Civil, Environmental and Geotechnical Engineering
• Materials Science
• Mining, Mineral & Petroleum Engineering

1. Introduction

Oil spills have deleterious effects on the environment, especially the marine ecosystem (Abidli et al., 2020; Chu et al., 2015; Garcia et al., 2020; Niu et al., 2021; Turco et al., 2015; Wang et al., 2015; Wang et al., 2015). It is estimated that ∼120 million gallons of crude oil and its refined products are spilled into the ocean annually (Peterson et al., 2003; Wu et al., 2021).

Several strategies have been implemented to address crude oil spills including ultrasonics, chemical dispersants, in-situ combustion, skimming, and vacuuming. However, these existing approaches present several challenges, including substantial energy use, resource, and time requirements. Moreover, they frequently demonstrate high toxicity and often fall short in terms of efficiency (Abidli et al., 2020; Garcia et al., 2020; Huang et al., 2020; Sadatshojaie et al., 2021; Torres et al., 2020).

Therefore, the need for enhanced technologies with reduced toxicity, cheap, rapid response, superior performance, and reusability in response to oil spills to mitigate the environmental impacts cannot be overemphasized (ben Hammouda et al., 2021; Dhaka & Chattopadhyay, 2021; Ghafoori et al., 2022; Gupta & Tai, 2016; Hoang et al., 2021). Photocatalysts and their modified forms have shown great promise in tackling oil spill and have been reported in prior studies by Agyei-Tuffour et al. (2020), Shi et al. (2021) and Zoghi and Allahyari (2022), environmentally friendly dispersants by Adofo et al. (2022), Nyankson, DeCuir, et al. (2015), Nyankson, Olasehinde, et al. (2015), and Shah et al. (2020). Photothermal materials development for highly viscous crude oil clean up (Chang et al., 2018; Ku et al., 2021; Niu et al., 2021; Wu et al., 2021) and the use of enhanced sorbent materials (ben Hammouda et al., 2021; Idris et al., 2014; Songsaeng et al., 2019; Vocciante et al., 2019; Yen Tan et al., 2021). The development of environmentally friendly and low-cost oil sorbent materials with high absorption capacity and hydrophobicity (Yen Tan et al., 2021) for oil spill remediation (Ku et al., 2021; Laitinen et al., 2017; Wang et al., 2015) is currently attracting significant attention in research endeavors.

These researches point to the effectiveness of sorbents (Bhardwaj & Bhaskarwar, 2018; Mardiyati et al., 2022; Yurak et al., 2021; Zamparas et al., 2020) in recovering liquids, particularly crude oil, employing a sorption mechanism (Bazargan et al., 2015; Hoang et al., 2021; Yurak et al., 2021).

Both natural and synthetic sorbents have been researched (Nyankson, Rodene, et al., 2015; Yurak et al., 2021) with preferences for natural fibers since they are less expensive, easier to handle, have high mechanical qualities, use less energy during production, and are biodegradable (Ahmad et al., 2015; Dhaka & Chattopadhyay, 2021; Dittenber & GangaRao, 2012; Hoang et al., 2021; Mojžiš et al., 2019; Rangappa & Siengchin, 2018; Singh et al., 2020; Zamparas et al., 2020). In addition, the handling of these fibrous materials in their natural state does not change their chemical constitution (Holbery & Houston, 2006). They provide fast absorption of oil through a mechanism that enables them to fill the pores within them (Ku et al., 2021).

Natural sorbents can be obtained from various plant components, including the stems, leaves, seeds, or fruits of plants (Dey & Haripavan, 2023; Loh et al., 2013; Narayanasamy et al., 2022). Examples such as cotton fibers, corn stalks, and non-woven wool have been employed as sorbent materials in the past (Deschamps et al., 2003; Devarshi et al., 2023; Kovačević et al., 2023; Santos et al., 2021; Yang et al., 2022) (Husseien et al., 2009). Sugar cane fiber (SF) and plantain pseudo-stem fiber (PF) are some other cheap examples of natural fibers obtained from waste (Danso, 2021; Juela et al., 2021). They contain lignocellulosic residues, exhibiting significant potential for utilization as sorbents (Danso, 2021; Juela et al., 2021). Sugar cane fiber is primarily made up of 50–70% SiO₂ (Faisal & Muhammad, 2016; Prabhath et al., 2023; Sholeh et al., 2021). The inherent combination of silica and lignin in the sugar cane fiber makes it a good candidate for sorption activities (Mardiyati et al., 2022). Given the sterling qualities of the sugar cane and plantain pseudo-stem fibers, they can be employed as typical porous substrates to fabricate modified sorbents (Huda et al., 2008; Loh et al., 2016; Loh et al., 2013; Zhou et al., 2021) for crude oil spill remediation.

Standardization of sorbent materials, as outlined by ASTM F726-12, categorizes them into four types. Bagged sugar cane and plantain pseudo-stem fibers fall into the Type III category, characterized by enclosed sorbents in outer permeable fabric or netting resembling pillows or booms (Bazargan et al., 2015).

In developing sorbent materials for oil spill remediation, high selectivity, sorption capacity, easy collection and recyclability of the materials is critical (Singh et al., 2020; Turco et al., 2015). Functionalization using TiO₂, graphene oxide (GO), and stearic acid (SA) as agents can enhance the intrinsic hydrophobicity of the otherwise hydrophilic natural sorbent materials (Iliyasu et al., 2022; Ma et al., 2016; Ramesh et al., 2022; Zhou et al., 2021) and make them good candidates for oil spill remediation.

The excellent TiO₂ photocatalyst combined with hydrophilic GO (Cote et al., 2010; de Oliveira et al., 2022; Ganesh et al., 2013; Nguyen et al., 2019; Some et al., 2013; Zhang et al., 2022) can increase the surface roughness of the material, therefore, providing it with special wettability (Baig et al., 2019; Liu et al., 2021; Zhou et al., 2021).

Stearic acid (SA) is a low-cost saturated fatty acid in the human body and therefore has no physical toxicity and is capable of enhancing the hydrophobicity of a material (Ma et al., 2016; Patti et al., 2021; Satria & Saleh, 2022; Zhou et al., 2021). Again, it is employed widely in research regarding medicine preparation (Galvão et al., 2020; Huang et al., 2008; Karnnet et al., 2005; Ma et al., 2016; Yang et al., 2020).

In this study, natural sorbent materials made up of sugar cane (SF) and plantain pseudo-stem (PF) fibers were loaded into tea bags to fabricate a viable type III sorbent material. The materials employed in this fabrication were inexpensive, common, biodegradable, and for that matter environmentally friendly, and supported proper utilization of waste.

The modification of the fabricated sorbent was accomplished through a low-cost, environmentally friendly, and easy-to-perform method of dip coating making use of the solution of ethanol, TiO₂, SA, and GO. The effects of the individual and combined surface modifiers on the SF and PF fibers and their oil uptake capacity have been presented. The potential of the modified SF and PF sorbent materials as an economical and environmentally benign approach toward oil spill remediation was demonstrated.

Thus, this research may open a new avenue for exploring bagged SF and PF sorbents as robust viable, economically, oleophilic, hydrophobic, and environmentally friendly sorbents for cleaning up oil spills.

2. Materials and methods

2.1. Materials

Sugar cane fiber (SF) and Plantain Pseudo-stem (PF) were obtained locally. Graphene oxide (GO), Stearic acid (SA), hexane, ethanol, and TiO₂ nanoparticles were purchased from Sigma-Aldrich, UK. All chemicals were analytical grade Deionized (DI) water, produced from an Elga water purification system (Medica DV25), with a resistance of 18.2 MΩ/cm was used in all experiments. Agbami Crude oil from Nigeria with a density of 889.9 kg/m³, and an American Petroleum Institute (API) gravity of 27.03 at 15 °C was obtained from Tema Oil Refinery (TOR), Tema, Ghana. 2 g Yellow-label Lipton tea bags were obtained from the market. Petrol and diesel were obtained from Shell Ghana. Shell Helix HX 3 20W-50 Multi-Grade Motor Oil for diesel and gasoline engines was obtained from Shell Ghana.

2.1.1. Preparation of SF and PF sorbent materials

The SF and PF sorbent materials were prepared to the type III standard of sorbent materials (Bazargan et al., 2015). The plantain stem fibre was obtained from the stem of the plantain tree while the sugar cane fibre was also obtained from the stalk of the sugar cane. They were washed with water and sun-dried. The fibers were rewashed using hexane and ethanol in succession. Hexane was added first and agitated with a shaker for 45 min After drawing off the hexane, ethanol was added and agitated for another 45 min before pouring off. The residue was then dried in an oven at 60 °C for 24 h.

0.5 g of smooth fibers of the plantain and sugar cane were bagged into new empty 2 g yellow label Lipton tea bags to form the SF and PF sorbent materials.

2.1.2. Modification of the SF and PF sorbent materials

GO and ethanol solution were prepared separately to different concentrations of 3, 4, and 5 mg/ml subjected to an ultrasonic treatment with a sonicator for 30 min. Then, 100 mg or a variable amount (150, 200, and 250 mg) of TiO₂ and 400 mg or a variable amount (200, 300, 500, and 600 mg) of stearic acid were added to 4 mg/ml GO-ethanol solution and subjected to further ultrasonic treatment for another 30 min. Subsequently, the SF and PF sorbent materials were immersed into the GO-ethanol, SA, and TiO₂ solution for 30 min of ultrasonic treatment. They were then continuously immersed in the solution for 24 h before the products were taken out. Finally, the samples were dried at 40 °C for 12 h in an oven.

The following acronyms/abbreviations were adopted along the manuscript to represent different substances as they appear in Figures 1a–f, 2a–d, 3a, b, and 4a, b. Specifically, “T” stands for TiO₂, “G” for GO (Graphene Oxide), and "S" for SA (Stearic Acid). A combination of abbreviations and numbers has been used to label various samples of SF and PF sorbents used in this study. Each label consists of abbreviated letters prefixed with numbers indicating the quantity of each substance used for the surface modification. To make it more user-friendly, the numbers have been downscaled by a factor of 100 (e.g. “×100 mg”).

Figure 1. (a–d) Water contact angle (WCA) and time for water droplets to linger on the surface of the modified and unmodified PF sorbents and (e and f) water contact angle (WCA) and time for the water droplets to linger on the surface of the SF and its modified form showing the optimization of the chemicals used in the modification process. 4 mg/mL (2) of GO (G) and 400 mg (4) of stearic acid (SA), and 100 mg (1) of TiO₂ (T) were used.

Figure 2. (a). Uptake/absorption capacities of the SF and PF modified and unmodified sorbents for some oils (b) uptake capacity/absorption capacity of the unmodified and modified SF sorbents in a crude oil/seawater environment, (c and d) recyclability of the modified PF and SF sorbents respectively for 5 cycles making use of crude oil.

Figure 3. Schematic diagram of the sorption mechanism of the bagged sorbents (a) at the initial stage and (b) at the final stage.

Figure 4. Microscopic images of (a) packed fibers in the tea bag, (b) the surface of the unmodified bagged sorbent (c) the surface of the modified bagged sorbent, (d) the modified fibers’ interaction with crude oil, (e) unmodified sorbent interaction with water and (f) modified sorbent’s interaction with crude oil.

For example, the sample labeled “4S2G1T/SF” represents a sorbent material formed by dip coating SF in a mixture of SA, GO, and TiO₂ in the proportions of 400 mg (4):200 mg (2):100 mg (1) respectively in 50 mL of ethanol.

2.1.3. Preparation of the synthetic sea salt

Synthetic seawater was prepared by dissolving 35 g of instant ocean salt obtained from Instant Ocean (Blacksburg, VA) in 1 L of distilled water. The mixture was stirred continuously for 24 h at room temperature to ensure complete dissolution of the salt particles.

2.2. Characterization

2.2.1. Fourier transform infra-red (FTIR) spectroscopy

A Vertex 70 v (Bruker) Fourier Transform Infrared (FTIR) spectrometer was used to record the FTIR spectra in the transmission mode of the modified and unmodified PF and SF sorbent materials. The spectra were carried out within the wavenumber range of 4000–400 cm⁻¹ with 4 cm⁻¹ resolution. The data was analyzed using the Opus software.

2.2.2. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS)

The SEM image analysis used the Phenom-World ProX desktop scanning electron microscope. Optical images were captured at the lowest magnification of 20×. Backscattered images were captured at different magnifications (minimum to maximum) using an image intensity and high-resolution voltage mode of 10 kV using the backscatter detector until the best image focusing ends. Further, using the Phenom ProSuite software (element identification), EDS point analysis at 15 KV, duration of 30 s, and map analysis at 15 KV, duration of 4 min 26 s were used for the elemental identification, distribution, and concentration respectively.

2.2.3. X-ray fluorescence (XRF) spectroscopy analysis

The XRF analysis was carried out using the Rigaku NEX CG desktop XRF which analyzes from ₁₁Na to ₉₂U non-destructively. Four grams (4 g) of the sample was weighed in a sample cup and subjected to X-ray fluorescence to obtain major oxides and elemental constituents using the fundamental parameters method double determination approach analysis. It was conducted in an atmosphere of Helium at a flow rate of 0.660 L/min for powder samples, tube voltage = 50 kV, and tube current = 1.00 mA.

2.2.4. Thermogravimetric analysis (TGA)

The TA Instruments SDT 2960 Simultaneous DTA-TGA was employed for thermogravimetric analysis (TGA) of the tea bags, plantain pseudo-stem fiber (PF), sugar cane fiber (SF), unmodified SF and PF sorbents (UMSF and UMPF respectively), and modified SF and PF sorbents (MSF and MPF respectively). The analysis was carried out in an air environment, using a 10 °C/min heating rate.

2.2.5. Mechanical testing of the properties of unmodified and modified tea bag

The mechanical testing of the tensile properties of the modified and unmodified sorbents bags were done using the universal testing machine, Mark 10 at 10 min mm⁻¹.

2.2.6. Static contact angle measurement

The water static contact angle (WCA) and oil static contact angle were measured by dropping a deionized water droplet or oil droplet from a micropipette as an indicator on the sponge at room temperature and pictures were taken using iPhone 11 camera and calculated with ImageJ 1.53t from Wayne Rashband and contributors, National Institute of Health, USA (http://imagej.nih.gov/ij.Java1.8.0_345) in conjunction with Drop analysis plugin. Three measurements with different positions on sponges were performed per sample and the average was calculated.

2.2.7. Water repellency experiment

The sorbent materials were entirely immersed in a 250 mL beaker with 150 mL water by applying an external force which was removed after 2 min. The modified sorbent materials floated on the surface of the water whereas the unmodified sorbent materials were submerged beneath the surface of the water.

2.2.8. Hydrophobicity and oleophilicity test

The hydrophobic/oleophilic properties of unmodified and modified sorbent materials were tested by placing the crude oil and water droplets on the top surface of both the modified and unmodified sorbent materials. The water droplets stayed on the surface of the modified material for some time whereas the crude oil droplets were absorbed almost immediately. On the other hand, both the water and crude oil droplets were almost immediately absorbed when exposed to the surface of the unmodified sorbent materials.

2.3. Absorption studies

In the oil sorption tests crude oil (CO), petrol (P), diesel (D), hexane (H), and Shell Helix HX 3 20W-50 Multi-Grade Motor Oil were used. The initial weight of the unmodified and modified sorbent materials before being immersed in the crude oil was recorded as M₁. After contact with the oils, the sorbent materials became quickly saturated after 30 min. After, they were allowed a dripping time of 10 min. The final weight was then recorded as M₂. The oil sorption capacity/uptake capacities of the sorbents were calculated and estimated using the following equation: (1) $$\text{Oil absorption capacity}/\text{Uptake capacity}/\text{Sorption Capacity}(\mathrm{g}/\mathrm{g})=\frac{M_{2 }-M_1}{M_1}$$(1)

2.4. Crude oil/water separation capacity

An attempt was made to examine the crude oil/water separation capacity of the modified and unmodified SF and PF sorbent materials. A 250 mL beaker was filled with a mixture of 50/50 v/v of crude oil and synthetic seawater. The initial weights of the sorbent materials were recorded and then they were placed in the mixture for a contact time of 24 h. After this, they were taken out of the mixture and permitted a dripping time of one (1) minute before their respective final weights were measured. Their absorption capacities were calculated using Equation (1)(1) $$\text{Oil absorption capacity}/\text{Uptake capacity}/\text{Sorption Capacity}(\mathrm{g}/\mathrm{g})=\frac{M_{2 }-M_1}{M_1}$$(1) . The absorbed crude oil was recovered by squeezing it out of the sorbent materials.

2.5. Reusability

The test of the absorption-desorption properties of the sorbents was modeled after the method used by Bayraktaroglu et al. (2021). It was used for the reusability experiments conducted in crude oil. First, the sorbents were contacted with the crude oil for 30 min around which they reached their maximum absorbency. After, they were allowed to release the absorbed liquids under gravity for one hour. This process was repeated 5 times.

3. Results and discussions

3.1. Surface morphological analysis of SF and PF sorbents

The surface characteristics of both the sorbent materials were examined using SEM/EDX analysis, with the outcomes depicted in Figure 5a–l. The fibrous materials, namely SF and PF, utilized in the fabrication of the sorbents exhibited a smooth surface, as evident in Figure 5e, i, along with the accompanying microscopy image and the SEM image of the bagged surface in Figures 5a and 6a, respectively. Furthermore, the SEM image of the SF revealed the presence of pores in the structure, as depicted in Figure 5i. Subsequently, following the modification process illustrated in Figure 5j, the porous skeleton structure of the fibrous materials remained predominantly unchanged. However, a few pores were discreetly coated by the modifying materials, as observed in comparison to the SEM image in Figure 5i. Notably, the modified surfaces (Figures 5b, f and j and 6b) also exhibited increased roughness in comparison to their untreated counterparts (Figures 5a, e, and i and 6a). This increase in roughness serves as a tangible indicator of the incorporation of surface-modifying materials, namely SA, GO, and TiO₂, both on the surface (Figure 5b and within the bulk of the sorbent materials, as illustrated in Figure 5e and f. This transformation is further corroborated by microscopy images of the surface of the sorbent materials in Figure 6a and b.

Figure 5. (a–d) SEM-EDS of unmodified and modified surfaces of the bagged sorbent material respectively, (e–h) SEM-EDS of unmodified and modified surfaces of the plantain pseudo-stem fiber respectively, and (i–l) SEM-EDS of the unmodified and modified surfaces of the sugar cane fibers respectively.

Figure 6. (a and b) Microscopy images of unmodified and modified surfaces of the sorbent material respectively.

The presence of these surface-modifying materials, SA, GO, and TiO₂, was again confirmed through EDS analysis, both on the surface and within the fibers of the sorbent materials, as evidenced in Figure 5d, h, and l by the presence of Ti in the peaks as compared the unmodified surfaces shown in Figure 5c, g and k which showed no Ti. This analysis underscores the efficacy of the dip coating method in successfully modifying the SF and PF sorbent materials.

The impact of the modification on the pores of the fibers of sorbent materials manifested in a slight reduction in their sorption capacities, a phenomenon illustrated in Figure 1e and f. Moreover, the efficacy of the modification process has been sufficiently demonstrated by the notable increase in the Water Contact Angle (WCA) of the modified sorbents as seen in Figures 1a, 7a, and 8a.

Figure 7. (a–d) Photographic images of the water droplets on the surfaces of the unmodified SF, modified SF, unmodified PF, and unmodified PF sorbent materials respectively, and (e–h) Photographic images of crude oil droplets on the surfaces of the unmodified SF, modified SF, unmodified PF, and unmodified PF sorbent materials respectively.

Figure 8. (a–f). Water Contact Angle (WCA) and time for water droplets to linger on the surface of the modified and unmodified SF sorbents using varying amounts of SA (S), GO (G), and TiO2 (T) in the surface modification.

3.2. Chemical and structural analyses of S.F and P.F

FT-IR was used to investigate the TiO₂, GO, and SA and how they interact with the sorbent materials. The investigation on the interaction was undertaken on the surface of the bagged modified and unmodified sorbents as well as on the fibers within the bags. The results are presented in Figure 9a–c.

Figure 9. a–c. FTIR of a. unmodified and modified surfaces of the bagged PF and SF sorbent materials, b. the unmodified and modified PF and SF fibers in the bagged sorbent materials and c. SA, TiO₂ and GO.

The FTIR spectra of the SA (Figure 9c) exhibit major peaks at 2919 cm⁻¹ and 2848 cm⁻¹, corresponding to the asymmetric and symmetric stretching vibrations of the –CH2– band, respectively (Chen et al., 2011; He et al., 2019; Yang et al., 2011). The peak at 1701 cm⁻¹ is also associated with –COOH (Li et al., 2017; Sood et al., 2022; Zhu et al., 2016). Concerning the GO (Figure 7c) the characteristic peaks (GO) spanning 400–900 cm⁻¹, 2847 – 3721 cm⁻¹, and the peaks at 1638 cm⁻¹ and 1056 cm⁻¹ can be assigned to O–H, C–H, C = C stretching, and C–O, respectively (Andrijanto et al., 2016; Faniyi et al., 2019; Khalili, 2016; Wang et al., 2011; Zhu et al., 2010). In addition, in the FTIR spectrum of TiO₂ (Figure 9c), the broad peak at 3500 cm⁻¹ is indicative of the hydroxyl group O–H (Mamaghani et al., 2018; Zhong et al., 2022), while Choi et al. (2004) also ascribe Ti–O bond to the wavenumbers between 600 cm⁻¹ and 800 cm⁻¹ (León et al., 2017; Mahmoudi et al., 2024; Mihaly Cozmuta et al., 2015; Mugundan et al., 2015).

The FTIR analyses conducted on both the unmodified fibers within the bagged sorbent materials and the surface of the bagged sorbent materials revealed striking similarities (Figure 9a and b). This uniformity suggests that all components involved are derived from plant-based materials, underscoring their shared environmentally friendly nature. The spectral bands at 432, 525, 556, and 860 cm⁻¹ are indicative of the C–H showing the presence of lignin (Scheufele et al., 2015). The results show that typical strong bands of the fibers are attributed to O–H stretching intramolecular hydrogen bonds for cellulose at 3330 cm⁻¹, C–H stretching at 2852–2919 cm⁻¹, C–O stretching vibration for the acetyl and ester linkages in lignin, hemicellulose, pectin at 1727 cm⁻¹ and the aromatic ring present in lignin and absorbed water at 1603 cm⁻¹ which are all associated with the SF and PF before the surface treatments (Ahmad et al., 2018; Kumar et al., 2020; Melesse et al., 2022; Zaheer et al., 2014).

After the surface modification/functionalization with SA, GO, and TiO₂, the spectral bands observed in the unmodified SF and PF sorbent materials were seen to be altered in the FTIR spectrum (Figure 9a and b). The effect of this surface modification can be observed through the main spectral bands. The spectral bands at 432, 525, 556, and 860 cm⁻¹ indicate Ti-O stretching vibration for TiO₂ with 1603 cm⁻¹ and 3330 cm⁻¹ indicating O–H. There were significant alterations seen between the unmodified PF and modified PF sorbent materials both internally with the fibers and externally on the surface of the bagged sorbent materials suggesting hydrogen bonds between GO and TiO₂. It was observed that the bands in the modified fibers as well as the surfaces were reduced significantly which can be attributed to the introduction of the SA, GO, and TiO₂ during the modification process.

Considering the unmodified SF and modified SF fibers, the spectral band at 2852–2919 cm⁻¹ indicating the C–H bond reduced drastically and the band at 3330 cm⁻¹ indicating O–H increased in the modified SF, suggesting an interaction between C–H and O–H of SA and GO respectively as compared to the unmodified. These alterations observed in the modified PF and SF fibers and the sorbent material surfaces could be attributed to the interaction between the GO, SA, TiO₂, and the sorbent material and the fibers contained in it. Zhou and co-workers present a similar interaction between the SA, TiO_2, and the GO with the melamine sponge in their work (Zhou et al., 2021). The above results show that the surface modification of the sorbent material was successful and confirmed by the SEM/EDX results in Figure 5a–l.

3.3. Compositional analysis of the SF and PF

In Table 1, we present the chemical composition of PF and SF, as assessed via X-ray fluorescence (XRF) analysis. Notably, SF stands out with a significantly elevated SiO₂ content, registering at 17.35, in contrast to the PF's SiO₂ content of 10.2. This SiO₂ component holds significant importance in the material’s absorption capacity, playing a pivotal role in its oil-absorbing capabilities (Filipović et al., 2010; Kamgar & Hassanajili, 2020; Lu et al., 2007; Mazrouei-Sebdani et al., 2019).

Table 1. Chemical Composition of the SF and PF.

Component	Average mass % of Plantain Fiber	Average mass % of sugarcane fiber
SiO2	10.2	17.35
K2O	37.8	17.85
CaO	34.4	27
Fe2O3	1.65	4.995
CuO	5.69	12.9
ZrO2	2.14	11.35
MgO	2.59	–
P2O5	2.89	–
SO3	–	4.415
Others	2.64	4.14

The inherent silica content with lignin found in sugar cane and plantain fibers enhances its oil-absorption capabilities (Mardiyati et al., 2022). The GO combines with the silica in the fibers to create a strong affinity for oil absorption (Ben Hammouda et al., 2021). It creates a strong adhesion between the sorbents and the oil. This phenomenon elucidates why the sorbent material composed of sugar cane fibers demonstrates superior absorption performance in comparison to that composed of plantain fibers as presented in Figure 4a.

3.4. Mechanical properties of tea bag, PF and SF fibers, modified PF and SF sorbents

Thermogravimetric analysis (TGA) was utilized to assess the thermal stability, moisture absorption, and decomposition characteristics of the tea bags, plantain pseudo-stem fiber (PF), sugar cane fiber (SF), unmodified SF and PF sorbents (UMSF and UMPF, respectively), and modified SF and PF sorbents (MSF and MPF, respectively).

Asim et al. (2020) outline the thermal degradation of natural fibers typically occurs in three stages. First, there is the loss of moisture through evaporation, a stage in which chemically treated or modified fibers generally exhibit lower moisture content. This is primarily because the modified sorbents become resistant to moisture hence the reduction in moisture contents (Aravindh et al., 2022; Gholampour & Ozbakkaloglu, 2020). The second stage involves the decomposition of cellulose and hemicellulose, occurring within the temperature range of 220–350 °C. The third stage is attributed to the decomposition of non-cellulosic substances such as lignin, spanning a broader temperature range of 200–500 °C (Hossain et al., 2014).

Figure 10a and b generally adhere to this degradation pattern, albeit with slight variations. The initial mass loss occurs within the temperature range of 10–110 °C for all analyzed samples, with mass losses ranging from 6% to 8%. The second stage of degradation takes place within the temperature range of 180–390 °C, accompanied by corresponding mass losses ranging from 2% to 8%. Notably, the modified sorbents (MSF and MPF) exhibit lower mass losses compared to the unmodified sorbents (UMSF and UMPF) in this stage.

Figure 10. (a) TGA and (b) thermographic analysis for derivatives of mass min⁻¹ versus temperature for the tea bag, plantain pseudo-stem fiber (PF), sugar cane fiber (SF), unmodified SF and PF sorbents (UMSF and UMPF, respectively), and modified SF and PF sorbents (MSF and MPF, respectively).

The third degradation stage occurs within the temperature range of 410–480 °C. Additionally, a fourth stage of degradation is observed around the temperature range of 600–650 °C which may be due to further decomposition of the remaining non-cellulosic content.

It is observed that the modified sorbents are more thermally stable than the fibers or the bags alone. Researchers agree that this observation may be due absence or reduction in hemicellulose and lignin content of the modified sorbents (Aravindh et al., 2022; Gholampour & Ozbakkaloglu, 2020; Hossain et al., 2014). These findings provide insights into the thermal behavior and decomposition kinetics of the investigated sorbents, shedding light on their suitability for oil spill remediation applications.

3.5. Mechanical properties of unmodified and modified tea bag

The mechanical properties of the tea bag must be outlined since the durability and utilization of the sorbent material are dependent on it. Given this, the tensile strength and strain as well as Young’s modulus were determined.

Using the data from Table 2 and Equations (1)–(3) the tensile strength, strain, and Young’s modulus of the unmodified and modified tea bags were calculated and presented in Table 3. (1) $$\epsilon =\frac{L_2-L_1}{L_1}=\frac{\Delta L}{L_1}$$(1) (2) $$\sigma =\frac{F}{A}$$(2) (3) $$E=\frac{\sigma }{\epsilon }$$(3)

Table 2. Parameters used in the calculation of the tensile properties of the unmodified and modified tea bag.

Material	Dimensions (×10^−3)/(m)	(Area × 10^−4)/(m^2)	Force (F)/(N)	Initial length (L1×10^−3)/(m)	Final length (L2 × 10^−3)/(m)
Unmodified Tea bag	32.64 × 29.76	9.7	3.0	32.64	45.65$$
Modified tea bag.	18.03 × 16.39$$	3.0	3.0	18.03	29.06$$

Table 3. Tensile properties of the unmodified and modified tea bag.

Materials	Tensile strength ($\mathit{\sigma })/\mathit{\text{MPa}}$	Tensile Strain ($\mathit{\epsilon })$	Young’s Modulus (E)/(GPa)
Unmodified tea bag	3.1	0.4	7.75
Modified tea bag	10.2	0.61	16.72

From Table 3 it is observed that the tensile properties of the unmodified tea bags increased upon their modification. An increase in strain means the introduction of ductility into the tea bags after the modification. In effect, the chemical modification with TiO₂, SA, and GO resulted in an improvement in the mechanical properties. This improvement is due to the removal or a reduction in the hemicellulose and lignin content (Aravindh et al., 2022; Gholampour & Ozbakkaloglu, 2020). Similar observations were made by researchers upon the treatment of fibers with other chemicals (Aravindh et al., 2022; Gholampour & Ozbakkaloglu, 2020; Hossain et al., 2014).

3.6. Oleophilicity and hydrophobicity of SF and PF sorbent materials

To study the crude oil/water separation ability, the crude oil and water droplets were dropped separately onto the modified and unmodified sorbent materials. The crude oil was absorbed immediately by both the modified and unmodified materials in a matter of seconds exhibiting their oleophilic nature. In contrast, water droplets exhibited prolonged retention on the surface of the modified sorbents before permeating them while the unmodified ones rapidly absorbed them within a matter of seconds (refer to Figures 1 and 8). The above observations show that the unmodified SF and PF sorbent materials were hydrophilic and oleophilic while the modified materials became hydrophobic and oleophilic. This means the surface modification using SA, GO, and TiO₂ was able to make the otherwise hydrophilic materials hydrophobic.

Again, the fact that the water droplets could be observed in spherical shapes on the surface of the modified sorbent materials while the crude oil was absorbed into the matrix of the sorbent materials confirms the porous nature of the sorbent materials. Other researchers also noted a similar observation when working with both untreated and treated cotton, as well as treated and untreated melamine sponges (Deschamps et al., 2003; Zhou et al., 2021).

3.7. Water repellency

Water repellency is a crucial property for absorbent or sorbent materials, particularly in the context of oil spill remediation (Rather et al., 2017; Wang et al., 2019). To test this property, the modified and unmodified sorbent materials were entirely immersed in water in a beaker by applying an external force. After the external force was removed, the modified sorbent materials instantaneously floated on the top of the water surface without any surrounding water droplets adhering to the surface, exhibiting water repellency. However, the unmodified sorbent material floated beneath the surface of the water showing it is not able to repel water. The above-observed water repellency of the modified sorbents points to their hydrophobic nature.

3.8. Surface wettability

In determining the surface wettability, Zhou et al. (2021) made use of surface water static contact angle (WCA) as an important factor to determine the wettability and oil absorption selectivity of the modified sorbent materials. The photographic images of the water droplets on the surface of the SA, GO, and TiO₂ modified and unmodified natural sugar cane fibers (SF) and the plantain pseudo-stem fiber (PF) sorbent materials have been presented in Figure 7a–d.

The calculated water contact angles are presented in Figures 1a and c and 8a, c, and e. Notably, the water contact angle increased from an intrinsic value of 63°–144° and 46°–126° for the modified SF (refer to Figure 8c) and PF (refer to Figure 1a and c) sorbent materials respectively indicating the introduction of a significant hydrophobic property. This agrees with what Law (2014, 2015), Hebbar et al. (2017), and co-workers have postulated that a water contact angle between 90° and 150° suggests hydrophobicity whereas above 150° suggests superhydrophobicity. Given the foregoing, the evidence points to the fact that the hydrophilic natural sorbent materials through surface modification using TiO_2, GO, and SA were made hydrophobic.

Through the surface modification, the TiO₂ nanoparticles and GO (i.e. 2G1T/SF) introduced surface roughness, which enhanced the hydrophobicity of the modified sorbent materials as seen in Figure 1e and f. The water contact angle recorded was 136.71° and it took the water droplet on the surface of the SF-modified material 6180 s to be absorbed into the sorbate. This was slightly lower than the modification using SA alone (i.e. 4S/SF) which recorded an increase in the intrinsic water contact angle from 62.86° to 140.84° for the 4S/SF (Figure 1e) suggesting an introduction of hydrophobicity into the otherwise hydrophilic SF material even though it took 1260 s (Figure 1f) for a water droplet to stay on the surface before being absorbed. It can be inferred from the preceding that the addition of stearic acid largely contributes to the hydrophobicity of the modified sorbent material. An observation that is in agreement with what Patti et al. (2021) and Satria and Saleh (2022) and co-workers have opined.

The hydrophilic characteristics of GO (2G/SF) were confirmed, even with a noticeable rise in the intrinsic water contact angle of the SF sorbent material from 62.86° to 82.59° (refer to Figure 1e). It’s noteworthy that the angle remains below 90°, the threshold for hydrophobicity. This observation emphasizes the water affinity resulting from the modification with GO. Again, the hydrophilicity of the GO, as evidenced in the (2G/SF) modified sorbent material, is further shown by the fact that it took only 2 s for a water droplet to stay on the surface of the sorbent material before being absorbed (Figure 1f). Other studies (Cote et al., 2010; Ganesh et al., 2013; Some et al., 2013) have confirmed the hydrophilicity of the GO. This means the GO contributed to the reduction in the water contact angle of the 4S2G/SF compared to the 4S/SF. In effect, the GO’s presence in the SA and GO combination might have reduced the hydrophobicity of the SA, hence the reduced contact angle recorded by the 4S2G/SF in Figure 1e.

Furthermore, by taking advantage of the long hydrophobic CH₂ chains of stearic acid and the surface roughness of the duo, TiO_2, and the GO, the combination of the TiO₂, GO, and SA and the SF sorbent materials (i.e. 4S2G1T/SF) exhibited superior surface hydrophobicity. It recorded a water contact angle of 144.04° (Figure 1e) and the time it took the water droplet to stay on the surface of the sorbent material was 12,600 s (Figure 1f). As alluded to earlier, the GO and TiO₂ increase the surface roughness, while the SA introduces hydrophobicity into the sorbent material. Therefore, the combination of these three chemicals in the surface modification of hydrophilic SF and PF sorbent materials made them hydrophobic and thus a suitable candidate for the separation of oil/water mixtures, hence efficient for oil spill remediation. This result is corroborated by Zhou et al. (2021).

Figures 1a–d and 8a–f present the durations water droplets lingered on both modified and unmodified sorbent material surfaces before permeating into them and their water contact angles. To optimize contact angle and water droplet staying time on the modified sorbent materials, the compositions of stearic acid (SA), TiO₂, and graphene oxide (GO) were systematically varied. Examined samples included 2S2G1T/SF, 3S2G1T/SF, 4S2G1T/SF, 5S2G1T/SF, 6S2G1T/SF for modified sugar cane fibers (SF), and 2S2G1T/PF, 3S2G1T/PF, 4S2G1T/PF, 5S2G1T/PF, 6S2G1T/PF for plantain pseudo-stem fibers (PF). Figure 1a and c indicate 4S2G1T/PF reached a peak contact angle of 126.31° with a droplet staying 7335 s (Figure 1b and d). Furthermore, 6S2G1T/PF sustained a droplet for 8100 s permeating it (Figure 1b) but achieved a lower contact angle of 103.6° (Figure 1a).

Remarkably, Figure 8c and d, which show that the TiO₂ was varied, reveal that 4S2G1T/SF exhibited a contact angle of 144.04° (Figure 8c) and sustained a water droplet on the surface for an extended 12,600 s (Figure 8d), signifying its optimal performance.

Focusing on Figures 1c and d and 8c and d, GO variations were explored alongside steady SA (400 mg) and TiO₂ (100 mg). Notably, 4S2G1T/PF achieved the highest contact angle of 126° (Figure 1c) from plantain pseudo-stem fiber samples (4S1.5G1T/PF, 4S2G1T/PF, and 4S2.5G1T/PF) and maintained water droplet on its surface for 7335 s (Figure 1d). Similarly, sugar cane fiber samples (4S1.5G1T/SF, 4S2G1T/SF, 4S2.5G1T/SF) mirrored these trends, revealing that 4S2G1T/SF yielded optimal results, with a contact angle of 139° (Figure 8c) and sustaining water droplet on its surface for 10,500 seconds (Figure 8d). In addition, varying the amounts of TiO₂ and keeping the amounts of SA and GO constant (refer Figure 8e and f) also shows that the 4S2G1T/SF had the highest water contact angle and longest water retention time on the surface of the sorbent materials of 144° and 12,600 s, respectively.

Both 4S2G1T/SF and 4S2G1T/PF demonstrated peak performance. Between the PF and SF sorbents, SF materials exhibited superior results. This may be attributed to the fact that the high silica content of the sugar cane combined well with the surface-modifying materials used to enhance its intrinsic hydrophobicity.

Again, the static contact angle was utilized to assess the wettability characteristics of oil on both modified and unmodified sorbents of SF and PF, with the results depicted in Table 4. All samples exhibited contact angles in the range of 34°–52°, which are less than 90°, indicating their oleophilic nature. Zamparas et al. (2020) even though the modification process altered the contact angles, it was observed that the modified sorbents showed a slight increase in contact angles compared to their unmodified counterparts. This difference may contribute to the higher oil sorption capacity of the unmodified sorbents compared to their modified counterparts (Figure 4a), as they possess a greater oleophilic tendency.

Table 4. Static contact angles of crude oil at 1 s on the unmodified and modified sorbent surfaces.

Sorbents	Unmodified SF	Unmodified PF	Modified SF	Modified PF
Static contact angle (°)	34.2°	41.8°	36.9°	50.4°

Similarly, both unmodified and modified SF demonstrated slightly lower contact angles compared to their PF counterparts, which could explain why SF sorbs more oil than PF (Figure 4a). The above observations demonstrate the success of the modification procedure in converting the natural-based SF and PF sorbents into hydrophobic-oleophilic materials.

3.9. Uptake capacity of and PF unmodified and modified sorbents

The investigation into the sorption/uptake capacities of both modified and unmodified sorbents (SF, PF, 4S2G1T/SF, and 4S2G1T/PF) concerning crude oil, diesel, petrol, hexane, and motor oil yielded interesting findings.

The unmodified SF sorbents exhibited significant sorption capacities for crude oil, petrol, diesel, hexane, and motor oil, with values of 11.43 ± 0.57, 6.67 ± 0.33, 9.30 ± 0.47, 6.37 ± 0.32, and 9.58 ± 0.48 g g⁻¹, respectively, compared to their PF counterparts, which demonstrated values of 6.40 ± 0.32, 2.97 ± 0.15, 4.76 ± 0.24, 2.32 ± 0.12, and 7.22 ± 0.36 g g⁻¹, as depicted in Figure 2a.

Similarly, the modified SF sorbents displayed enhanced sorption capacities for crude oil, petrol, diesel, hexane, and motor oil, with values of 10.29 ± 0.51, 6.02 ± 0.30, 8.38 ± 0.42, 5.87 ± 0.29, and 8.62 ± 0.43 g g⁻¹, respectively, compared to their PF counterparts, which showed values of 5.77 ± 0.29, 2.70 ± 0.14, 4.56 ± 0.23, 2.10 ± 0.11, and 6.72 ± 0.34 g g⁻¹, respectively.

These findings underscore the efficacy of both unmodified and modified SF sorbents in absorbing various types of hydrocarbons, highlighting their potential utility in oil spill remediation and related applications.

Despite this, it was observed that the sorption capacities of the modified sorbents recorded slightly reduced values compared to the unmodified sorbents, which stands contrary to most findings on the modification of natural-based sorbents (Zamparas et al., 2020). This may be due to the surface-modifying materials that appear to occupy pore spaces within the modified PF and SF sorbent matrix, as highlighted in Figure 5f and j. Consequently, the modification materials potentially hinder the pore accessibility to a limited extent, thereby affecting the uptake/absorption capacities of the modified materials. This observation is consistent with the findings of other researchers (Bae & Choi, 2003; Deschamps et al., 2003).

These observations collectively highlight the relationship between the surface modification method used in this study and sorption performance, shedding light on the intricate mechanisms that influence material porosity and sorbent functionality. Further investigation would seem appropriate to precisely elucidate the factors contributing to this observed behavior and to refine our understanding of the interrelationship between material modifications and sorption dynamics.

3.10. Oil/water separation capacity

To better assess the practical effectiveness of the sorbent materials, we conducted a comprehensive examination of both their unmodified and modified forms in terms of their oil/water separation efficacy, as depicted in Figure 2b. These experiments, conducted with a 24-h contact time and a 1-min dripping time, offer valuable insights into their performance.

In the context of crude oil/seawater mixtures, the modified sorbent (4S2G1T/SF) exhibited the capacity to absorb crude oil effectively. Notably, the unmodified SF sorbent displayed a higher oil absorption rate than the modified SF variants. This disparity could potentially stem from the inherent tendency of SF to absorb some water along with the crude oil. Zhou et al. (2021) point to a similar observation in their work.

Moreover, the reduced oil absorption observed in the modified SF materials can be attributed to the presence of SA, GO, and TiO₂, which potentially fill the matrix pores that would otherwise, accommodate crude oil. The filling of the matrix pores by the modifying materials (SA, GO, and TiO₂) was observed in the SEM images in Figure 5f and j. An observation Deschamps et al. (2003) and Choi and Cloud (1992) have also noted.

After saturation with crude oil, the sorbent materials (4S2G1T/SF and SF) could readily release the absorbed crude oil by connecting them to a pump capable of extracting the crude oil from them (Jiang et al., 2016; Niu et al., 2021; Wang et al., 2019), highlighting their practical applicability in recovering the absorbed oil. This ease of recovery adds to the attractiveness of these materials for real-world oil spill cleanup scenarios.

Once the sorbent material comes into contact with the oil particles, they are initially attracted to the surface of the sorbent material through adsorption (Figure 3a), utilizing intermolecular forces such as London–van der Waals forces and hydrogen bonding (Ponec et al., 2018; Tran et al., 2017; Wang & Hou, 2024).

After 30 min, the oil particles then migrate to the surfaces of the fibers within the enclosed sorbent material, where they are adsorbed, and then penetrate the pores of the fibers through absorption (Figure 3b). The pores of the fibers are penetrated by capillary action (Zamparas et al., 2020). In effect, the oil particles interact with the sorbent material through the adsorption-absorption mechanism.

The surface morphological comparison between the unmodified and the modified sorbents before and after interacting with crude oil is shown in Figure 4. The surface of the sorbents exhibits a porous network of interconnected structures (Figure 4b), allowing the crude oil to be both adsorbed on the surface and absorbed by the fibers within it. The fibers are closely packed within the structure, enabling them to sorb oil as well. In effect, the sorbent material can interact with the crude oil through a sorption mechanism (Figure 4d–f). Figure A shows the oleophilic unmodified surface of the sorbent and its interaction with water (Figure 4e).

3.11. Reusability of SF and PF sorbents

The reusability of sorbents plays another crucial role in oil spill applications (Zhou et al., 2021; Bayraktaroglu et al., 2021). In doing this experiment, the sorbed oil was allowed to drain under gravity without any external as opposed to compression extrusion owing to the concerns raised by some researchers against it (Zamparas et al., 2020). The reusability performance of modified sorbents (PF and SF) was assessed by subjecting them to repeated absorption-desorption cycles in crude oil, conducted five times sequentially (Figure 2c and d). The results demonstrate that the maximum absorption performance remained consistent throughout each cycle for both sorbents, indicating their reusability in crude oil. For each cycle of adsorption-desorption, about 30% of oil is drained from the sorbent after one hour under gravity.

Following the five cycles, the PF sorbent (Figure 11a) exhibited a water contact angle of 100.5°, while the SF sorbent (Figure 11b) showed a water contact angle of 102°. Although slightly reduced, both contact angles remained within the hydrophobic range. Therefore, the hydrophobicity, absorption capacity, recovery rate, and reusability of the modified sorbents position them as promising candidates for oil spill applications.

Figure 11. (a and b) Photographic images of the PF and SF sorbents, respectively, after 5 cycles with water droplets on the surface to analyze their hydrophobic state.

Comparing the sorption capacities of the SF and PF sorbent materials with those documented for various natural sorbent materials in Table 5 from existing literature, it is evident that the SF and PF sorbents exhibit favorable performance. When compared to most natural sorbents (both modified and unmodified), except for wastepaper and pomelo peel. This suggests that the prepared sorbents have substantial potential for effective use in the remediation of crude oil spills.

Table 5. Absorption/sorption capacities of different natural sorbents.

Sorbent	Modification method	Sorption capacity	Type Of Oil	API gravity/density/ viscosity of crude oil	Contact time (Min)	Dripping Time	Ref
Bagged sugar cane fiber	Raw	11.43	Crude oil	(API) gravity of 27.03 at 15 °C/ 0.8899 g/cm^3	30 min	10 min	In this study
Bagged sugar cane fiber	Dip coating with SA, GO, and TiO2 in ethanol.	10.29	Crude oil	(API) gravity of 27.03 at 15 °C/ 0.8899 g/cm^3	30 min	10 min	In this study
Bagged plantain pseudo-stem fiber	Raw	6.4	Crude oil	(API) gravity of 27.03 at 15 °C/ 0.8899 g/cm^3	30 min	10 min	In this study
Bagged plantain pseudo-stem fiber	Dip coating with SA, GO, and TiO2 in ethanol.	5.77	Crude oil	(API) gravity of 27.03 at 15 °C/ 0.8899 g/cm^3	30 min	10 min	In this study
Banana Peel	Raw	6–7	Crude Oil	41.38°/ 0.8180 g/cm^3 at 15 °C /2.29CST at 40 °C	15min	5 min	El-Din et al. (2018)
Saw Dust	Raw	4.1–6.4	Crude Oil	25.8°/0.90 g/cm^3/34 Cp	5,10,20,40,60,1440 (min)	5 min	Annunciado et al. (2005)
Coir Fiber	Raw	1.8–5.4	Crude Oil	25.8°/0.90 g/cm^3/34 Cp	5,10,20,40,60,1440 (min)	5 min	Annunciado et al. (2005)
Luffa	Raw	1.9–4.6	Crude Oil	25.8°/0.90 g/cm^3/34 Cp	5,10,20,40,60,1440 (min)	5 min	Annunciado et al. (2005)
Orange Peel	Raw	3–5	Crude Oil	The specific gravity of 0.89	5.10.15.30 and 60 (min)	5 min	El Gheriany et al. (2020)
Barley Straw	Raw	6.5–12	Crude Oil	29.66°/0.82 g/cm^3/17.18 Cs	5–30 min	5 min	Husseien et al. (2009b)
Rice Husk	Pyrolysis	6 & 9.2 for light crude and heavy crude resp.	Heavy Crude Oil and Light Crude	0.937 g/cm^3 and 0.792 g/cm^3	10 min	10 min	Angelova et al. (2011)
Rice Husk	Pyrolysis	15	Crude Oil	0.937 g/cm^3 and 0.792 g/cm^3	30 min	10 min	Kudaybergenov et al. (2013)
Rice Husk	Pyrolysis	2.98–6.22	Crude Oil	at 293 K = 869.8 kg/m^3, viscosity at 313 K = 12.28 mm^2 /s, p	5–20 min	2–3 min	Vlaev et al. (2011)
Rice Husk	Pyrolysis	6	Heavy Crude Oil	0.937 g/cm^3 and 0.792 g/cm^3	30 min	10 min	Kumagai et al. (2007)
Soybean	Mercerization	5	Crude Oil	191 kg/m^3	10 min	15 min	Wong et al. (2016)
Oil Palm Empty Fruit Bunch	Acetylation	7	Crude Oil	–	10–15 min	4 h in oven at 60°	Onwuka et al. (2018)
Cocoa Pods	Acetylation	8	Crude Oil	–	10–15 min	4 h in oven at 60°	Onwuka et al.(2018)
Wastepaper	Aerogel with MTMS	24.4	Crude Oil	–	–	–	Tang et al. (2015)
Pomelo Peel	Aerogel with MTMS	49.8	Crude Oil	–	–	–	Ratcha et al. (2014)
Kenaf core fiber (Sachet & Powder)	–	6.7–8	Crude Oil	–	2 min	15 min	Yen Tan et al. (2021)
Jute fiber	Carbonization	7.8–8.7	Crude Oil	15°: 0.8703 g/mL	15 min	30 s	Kovačević et al. (2023)

4. Conclusions and summary remarks

A hydrophobic and oleophilic natural sorbent material, economically derived from sugar cane (SF) and plantain pseudo-stem (PF) fibers, has been successfully developed in this study. Through a systematic exploration of varying concentrations of graphene oxide (GO), stearic acid (SA), and titanium dioxide (TiO₂), an optimal combination has emerged. Specifically, an ethanol solution with a GO concentration of 4 mg/ml, paired with 100 mg TiO₂ and 400 mg SA, yielded SF and PF sorbent materials with exceptional results.

Surface modification resulted in significant enhancements in water contact angles, with SF achieving 144° from an intrinsic 63°, and PF reaching 126° from an intrinsic 46°. These improvements underscore the successful augmentation of hydrophobic characteristics, a key objective of our study.

The modified SF exhibited an impressive crude oil uptake capacity of 10.29 g/g, while the PF variant reached 5.77 g/g. Notably, these remarkable results were achieved with just 30 min of contact time and 10 min of dripping time, emphasizing the efficiency of our developed sorbent materials.

In conclusion, our study demonstrates the successful synthesis of an economical and environmentally friendly sorbent material from SF and PF fibers. The optimized combination of surface modifiers has led to enhanced hydrophobic properties and remarkable oil uptake capacities. These findings underscore the potential of our sorbent materials as a practical and efficient solution for oil spill remediation.

The deficiency in the sorption capacity and reusability of SF and PF is less superior compared with some other synthetic-based sorbents. Another challenge encountered with the SF and PF natural sorbents stems from their poor oleophilic/hydrophobic properties. The synergy between the TiO₂ nanoparticles, GO, SA, and the fibers can enhance the hydrophobic characteristics of the sorbents. These are some suggestions for further work.

Author contributions

All authors contributed to the study. The research conception and design were developed by EN, BAT, and SG. Materials preparation, experimental procedures, and data collection were performed by SG, DN, and YKA. The data analyses were carried out by SG, DN, YKA, BM, BAT, and EN. The first draft of the manuscript was written by SG and all authors commented on previous versions of the manuscript. A final review of the manuscript was performed by BAT and EN. All authors read and approved the final manuscript.

Consent to participate

All authors have been personally and actively involved in substantial work leading to the paper and will take public responsibility for its content.

Consent to publish

The paper is not currently being considered for publication elsewhere.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The datasets generated during and/or analyzed during the current study are available from the corresponding authors upon reasonable request.

Additional information

Funding

The authors declare that this project was funded by the University of Ghana’s BANGA-Africa program with funding from the Carnegie Corporation of New York.

Notes on contributors

Selassie Gbogbo

Selassie Gbogbo and Yaw Kwakye Adofo are PhD students in the Department Materials Science and Engineering, University of Ghana researching into photocatalysts, nanofibers and dispersants for contaminated water and oil spill remediations.

Daniel Narh

Daniel Narh is a Research Assistant in the Department of Materials Science and Engineering. He completed his Bachelor’s degree from the same department in the area photocatalyses.

Yaw Kwakye Adofo

Selassie Gbogbo and Yaw Kwakye Adofo are PhD students in the Department Materials Science and Engineering, University of Ghana researching into photocatalysts, nanofibers and dispersants for contaminated water and oil spill remediations.

Bismark Mensah

Prof. Benjamin Agyei-Tuffour, Prof. Emmanuel Nyankson and Dr. Bismark Mensah are researchers in the Department of Materials Science and Engineering. The research interests are in composites materials for energy and environmental remediation, photocatalyses and dispersants, and mechanical behaviour of materials.

Benjamin Agyei-Tuffour

Prof. Benjamin Agyei-Tuffour, Prof. Emmanuel Nyankson and Dr. Bismark Mensah are researchers in the Department of Materials Science and Engineering. The research interests are in composites materials for energy and environmental remediation, photocatalyses and dispersants, and mechanical behaviour of materials.

Emmanuel Nyankson

Prof. Benjamin Agyei-Tuffour, Prof. Emmanuel Nyankson and Dr. Bismark Mensah are researchers in the Department of Materials Science and Engineering. The research interests are in composites materials for energy and environmental remediation, photocatalyses and dispersants, and mechanical behaviour of materials.