Across the world, the exploration and transportation of crude oil has transformed many sectors. Several approaches to averting the threat of pollution have been researched, and the application of polymer strips to clean up oil spills is a growing area of interest.
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Oil spillage is one of the most prevalent anthropogenic causes of pollution that accompanies the exploration and usage of crude oil globally. In 2010, the world recorded the largest oil spill when an estimated 4.9 million barrels of crude oil engulfed the Gulf of Mexico. The continuing report of oil spills from sea accidents and the release of water-insoluble organic solvents such as benzene, dichloromethane, cyclohexane, and toluene into open waters continue to pose a severe threat to aquatic and human life.
Several remediation strategies, such as biological treatment, flotation, slag removal, and gravity separation, have been employed in remediating the accompanying challenges of crude oil explorations. All of these methods are classified into four categories as follows: i) mechanical recovery methods involving the use of sorbents, skimmers, and booms; ii) In-situ burning; iii) chemical treatments involving the use of solidifiers and dispersants, and iv) bioremediation. The most common limitations of these methods include high cost, environmental pollution (in-situ burning), incomplete separation, methodological difficulties, and low efficiency of the overall process.
Recent years have been marked by a convergence of efforts to develop improved remediation processes to find the most affordable, convenient, and practical approach to oil spill remediation. To date, physical adsorption (mechanical recovery) continues to lead in that race ahead of other methods as it is straightforward and eco-friendly. A significant factor determining the efficiency of physical adsorption is the choice of the sorbent material and its properties. An ideal sorbent should be highly oleophilic and hydrophobic at the same time. It should have high buoyancy and oil sorption capacity, and few materials can meet these requirements.
Ideal sorbents that have continued to generate much research interest are polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), aerogels, resins, foams, sponges, and polystyrene (PS) that have undergone the process of electrospinning to produce sorbents with improved surface-to-volume rations, higher oleophilic, and hydrophobic properties among others. In addition to the electrospinning method, other crucial components that affect the properties of the polymer strip include the choice of the adsorbent material. Porous polymeric composites have been reported to be an excellent choice owing to their high adsorption capacity, ease of preparation, and subsequent recycling.
While there are other methods for fabricating polymer strips at the nano and sub-micro scale, electrospinning is one of the most popular and versatile. This approach can be applied to various types of polymer sorbent materials, and the resulting strips can be modeled to exhibit novel and improved properties for effective clean-ups. Electrospinning involves melting the polymer serving as the sorbent and charging the melt through a spinneret to coagulate or solidify under a high-voltage electric field. This results in the formation of a filament or fibers. The type of polymer material and the concentration are also critical factors that dictate the morphology of the fabricated fibers upon the completion of the electrospinning process.
Meanwhile, with the increasing number of plastic wastes from both industrial and domestic uses, recycling these plastic wastes to produce useful sorbent materials for oil spill remediation is necessary. An estimated 380 million tons of plastic waste are produced globally, polluting the environment. This article reviews the recent trends in the applications of plastics as starting materials for polymer strips and how they have been employed in alleviating oil spillage.
Recent Studies and Applications
With the increasing demand for a more efficient, convenient, cost-effective, and eco-friendly approach to cleaning up oil spills, many modifications and fabrication methods have been researched, applied, and documented. In a study published in ACS Omega, the authors investigated multifunctional oil absorption with macroporous polystyrene fibers incorporating silver-doped zinc oxide. Varying morphologies of silver-doped zinc oxide (Ag-ZnO and zinc oxide (Zn)) were added to the polystyrene fibers and spun using a solvent-induced phase separation technique. The addition of Ag-ZnO enhanced the pore size, thereby increasing its hydrophobic and oleophilic properties. The authors reported that the fabricated polymer strips showed qualitative and quantitative efficacy in oil spill remediation. In addition, while both materials showed antimicrobial activity against staphylococcus aureus, the polymer strip fabricated with Ag-ZnO showed higher efficacy.
In another study published by the Royal Society of Chemistry, the authors prepared a porous superhydrophobic foam using waste plastic and applied it for oil spill clean-up. A one-step High Internal Phase Pickering Emulsion (HIPPE) fabrication technique was used, resulting in a highly stabilized emulsion that exhibits excellent superhydrophobicity, superoleophilicity, and multi-order porosity. Upon application, the results were fantastic, as the fabricated superhydrophobic foams showed a high adsorption capacity of 20.4 – 58.1 g/g. The process was fast and selective, and the foams only showed a 1% decline in their adsorption capacity after ten cycles.
In another study in the journal SN Applied Sciences, a ternary system oleophilic-hydrophobic membrane was prepared by electrospinning for an efficient gravity-driven oil-water separation system. The authors explored the use of composite nanomaterials to prepare a novel ternary mixture system that consists of cellulose acetate (CA), polystyrene (PS), and polyvinylidene fluoride (PVDF). The choice of degradable cellulose was to promote compatibility between the two polymer layers and enhance pore formation, while PVDF boosts the mechanical properties. The resulting composite material was subjected to oil/water separation tests, and the results showed that the fabricated components had superior mechanical properties, high oil flux, and separation efficiency.
Mechanical recovery involves the use of sorbents, and this is one area that continues to attract much interest for many reasons. This approach allows for novel modifications that include the choice of fabrication methods (electrospinning or High Internal Phase Pickering Emulsion (HIPPE) fabrication), plastic material, and other additives to achieve the desired physical properties for effective clean-up.
With the continuing exploration and transportation of crude oil across different parts of the world, the need for a holistic, efficient, convenient, and eco-friendly remediation approach cannot be over-emphasized.
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References and Further Readings
Ali. A., et al. (2021). Multifunctional Oil Absorption with Macroporous Polystyrene Fibers Incorporating Silver-Doped ZnO. ACS Omega, 6, 8081-8093. https://pubs.acs.org/doi/pdf/10.1021/acsomega.0c05683
Li, S., & Lee, B. K. (2022). Facile generation of crumpled polymer strips by immersion electrospinning for oil spill clean-ups. Journal of colloid and interface science, 626, 581–590. Advance online publication.
Wang, L., Dai, S., Lie, X., Wang, X. and Lu, H. (2019). A ternary system oleophilic-hydrophobic membrane prepared by electrospinning for efficient gravity-driven oil-water separation. SN Applied Sciences, 1(797). https://doi.org/10.1007/s42452-019-0805-9.
Isık, T., & Demir, M. M. (2018). Tailored electrospun fibers from waste polystyrene for high oil adsorption. Sustainable Materials and Technologies, e00084. doi:10.1016/j.susmat.2018.e00084
Yu. C., et al. (2019). Preparation of a porous superhydrophobic foam from waste plastic and its application for oil spill clean-up. Royal Society of Chemistry Adv., 9.
Ge. J., et al. (2016). Advanced Sorbents for Oil-Spill Clean-up: Recent Advances and Future Perspectives. Adv. Mater. http://dx.doi.org/10.1002/adma.201601812