Introduction
Oil is globally used as the primary energy source and as a raw material for chemicals and synthetic polymers. The oil demand is high transported from the source to various destinations worldwide. The Persian Gulf is the home of many offshore oil and gas operations. It is also busy with oil transports by ships and pipelines. About 25,000 tanker movements occur in the Strait of Hormuz annually. Sixty percent of all the oil is transported by sea. An oil spill occurs when being transported due to accidents or deliberate acts. For sustainable development, the disposal of the sorbents used has been a primary concern. The oil sorption and retention behavior of sorbents are influenced by the oil’s physical characteristics, structure, and material, thus impacting the cleanup approaches.
Oil Sorbents
Absorbents are the materials that soak up liquids based on scientific mechanisms. Oil contaminants on the surface of the water can be recovered through sorbents (Zhang et al., 2019). The absorption and adsorption mechanisms are used either separately or together. Absorbents must be water-repellant and oleophilic to help combat oil spills (Chau et al., 2021). Oil sorbents can transform the liquid contaminant into easily moved solids without draining (Zamparas et al., 2020). They efficiently remove oil pollutants from water and are inexpensive, making them economically viable. Sorbents are affordable, easily stored, and can be used with untrained personnel (Oliveira et al., 2021). After getting used, they must be disposed of or cleaned appropriately before reusing.
Current Oil Absorbents and The Problems Faced
Synthetic absorbents, including artificial materials made from plastic, are designed to adsorb liquids. They also include rubber materials and cross-linked polymers, which absorb oil spills and swell up in the process (Oliveira et al., 2021). The most commonly used manufactured synthetic absorbent can absorb spills 70 times their weight, making them efficient (Zhang et al., 2019). They are expensive but can cover many areas affected by oil contamination. The materials may take many years to degrade, making them a threat to the natural environment (Zamparas et al., 2020). Excessive use of artificial synthetic absorbents can cause cleanup problems. As a result, it is essential to use recycled organic and naturally occurring absorbents, including fibrous waste materials such as paper and face masks.
Impact of Recycled Fibrous Waste
Sorbent materials are used to soak up liquids through either adsorption or absorption. Fiber-based materials efficiently absorb oil contaminants into the fibers and are highly recyclable (Li et al., 2020). Examples include raw cotton, kapok fiber from agricultural products, milkweed fiber, acylated cotton, and nonwoven polypropylene (Doshi et al., 2018). They repel water outside and retain oil, although they tend to absorb both, questioning their effectiveness. An increase in temperature tends to increase the oil sorption capacity in these materials. Fiber diameters determine the oil retention rate (Loh et al., 2021). The viscosity of the liquid plays a significant role in determining the fiber materials’ rate of fluid absorption capacity (Han et al., 2016). Fluids with higher viscosity take extra time to penetrate the pores. The materials tend to soak up light oils more quickly than heavy ones.
Fibrous materials Useful in Oil Sorption
The recyclable fiber materials used for oil spill recovery are significant inventions in the current century as most are environmentally friendly. Typical forms of recyclable fiber materials include cotton, kapok, milkweed, and polypropylene (Doshi et al., 2018). Oil sorption can be done using raw cotton fibers that engage in the adsorption mechanism whereby the surface waxes interact with the liquid. Agricultural products contain kapok fiber that contains 23 percent pentosane, 13 percent lignin, and 64 percent cellulose; kapok fiber has hydrophobic characteristics (Doshi et al., 2018). Milkweed fiber absorbs light oil spills; its fiber diameters range from 20 to 50 micrometers (Doshi et al., 2018). Polypropylene is commonly used and is ideal for oil spill recovery in the marine environment. The absorption property of these materials relies on the number of pores available between each fiber.
Aerogels Use to Absorb Oil
The continuous liquid phase in aerogels is replaced with air, resulting in a solid porous material. Aerogels have distinctive characteristics: low density, high surface area, and high porosity. The attributes allow for massive sorption and flotation of the materials on water. They can be prepared using organic, inorganic, and natural biomaterials (Han et al., 2016). Typical raw materials used in making these environmentally friendly sorbents include recycled waste, paper waste, waste newspaper, rice straw cellulose, and cellulose nanofibers (Chau et al., 2021). The recovery methods adopted by the mentioned materials include mechanical, distillation, and extraction. Most of the raw materials possess the amphiphilic characteristic hence the need to add hydrophobic moieties on the surface of the sorbent. (Doshi et al., 2018) Using fiber-based materials is advantageous; they can be recycled and are inexpensive.
Cotton Fiber
Raw cotton is highly effective at absorbing oil from water. Modified cotton fiber has also emerged as an alternative sorbent that is efficient in sorption (Zhang et al., 2019). It can be fabricated in various forms, just like raw cotton, easing its use. Natural cotton has a waxy coating that makes it naturally hydrophobic (Zamparas et al., 2020). Given its positive environmental footprint and high sorption capacity, natural cotton is considered an ecologically friendly sorbent. Cotton can use the three main processes of oil removal at once. At first, adsorption is experienced when the oil clings to the surface of the cotton fibers. The cotton fibers can also absorb the oil, and lastly, the capillary action is used; this is when the oil is sucked up and let to flow into the channel spaces between the fibers.
Agricultural Waste Materials
Agricultural waste is preferred in cleaning oil spills from water surfaces due to its buoyancy and biodegradation. The success of these materials in cleaning up oil contaminants depends on the oil type, salinity of the crude oil, temperature, and oil film thickness (Hammouda et al., 2021). Kapok fiber is an agricultural product with very high oil absorbency characteristics (Loh et al., 2021). It is fluffy, odorless, resistant to rot, non-toxic, and non-allergic. Cornstalk fibers in the corn cob effectively remove contaminants from water (Oliveira et al., 2021). The material is far more effective when dry as it is buoyant, removing waste without sinking. Agricultural waste materials like banana peels and rice husks can absorb oil into the fibers present and repel water. Their unique characteristic makes them effective in oil spill cleaning.
Waste Print Papers
The use of paper worldwide results in the creation of more waste. Each year about 100 tons of wastepaper are produced; these materials can be reused and effectively clean oil contaminants (Han et al., 2016). Han et al. (2016) indicated that treated waste paper could remove heavy metal ions from water. Paper is made from cellulose fiber and can be used as a bio-adsorbent. Waste paper is efficient as a sorbent as it is readily available, cheap, easy to use, and highly effective. It is a low-cost cellulosic material that is present in abundance (Han et al., 2016). The ready availability makes it a better raw material for fabricating carbo-based sorbents.
Surgical Face Masks
Surgical masks have been used widely during the Covid-19 pandemic period. They are made of polypropylene fibers, making them effective in separating oil from water (Oliveira et al., 2021). The fibrous material contains tiny pores which facilitate the transport of liquids into the sorbents; they are then retained after sorption (Han et al., 2016). Polypropylene is the leading sorbent in sorption among all the present fiber materials (Zhang et al., 2019). Masks possess oleophilic and hydrophobic properties.
Additionally, they have high oil adsorption capacity and are not much costly. The fibrous structures present in the material make it possible to act as a sorbent (Hammouda et al., 2021). The materials can be recycled and used as sorbent; as a result, the pollution caused by it will be reduced.
Conclusion
Oil is commonly used worldwide as a source of heat, making it a precious commodity. Oil spills can occur during transportation, especially at sea, resulting in pollution. Sorbents can be adopted to eliminate the threat and are readily available. Fibrous materials are effective in absorbing oil and are found in recyclable materials such as paper and surgical masks. Polypropylene fiber is the most effective fibrous material in oil sorption among all the other sorbents. Other potential sources include agricultural materials which contain fiber and are easily accessible. Adopting the use of these recyclable fibrous materials is cost-effective. It also results in the reduction of waste pollution as some of the materials are used daily.
References
Chau, M., Truong, T., Hoang, A., & Le, T. (2021). Oil spill cleanup by raw cellulose-based absorbents: A green and sustainable approach. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 23(5), 1-14. Web.
Doshi, B., Sillanpää, M., & Kalliola, S. (2018). A review of bio-based materials for oil spill treatment. Water Research, 135, 262-277. Web.
Hammouda, S., Chen, Z., An, C., & Lee, K. (2021). Recent advances in developing cellulosic sorbent materials for oil spill cleanup: A state-of-the-art review. Journal of Cleaner Production, 311(6), 01-20. Web.