Effective separations of oil/water mixtures and emulsions are challenges worldwide due to the increasing production of oily industrial wastewater and frequent oil spills which result from industrial accidents and the sinking of oil tankers. and other ships. In 2010, the explosion of BP's Deepwater Horizon oil rig resulted in 210 million gallons of oil spilling into the Gulf of Mexico. Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”?Get an original essayTraditional oil/water separation techniques such as air flotation, gravity separation combined with skimming, absorbent materials oil, coagulation and flocculation are limited. and are not effective in separating emulsions, making additional processing necessary. Therefore, facile synthesis of superoleophobic or superhydrophobic materials attracts much attention from industries. Consequently, there is a need to develop new materials that would allow oil/water separations to be carried out efficiently, at low cost, with high performance. selectivity. Recently, materials possessing both superhydrophobic and superoleophilic properties have attracted widespread attention due to their ability to effectively separate oils, organic pollutants, and other hydrophobic organic solvents from water. Although such previously developed materials can be effective agents for oil/water separation, they are easily fouled, or even blocked, by oils due to their intrinsic oleophilicity. Additionally, because water is generally denser than oil, it tends to settle below an oil phase, forming a barrier layer above the separation material and inhibiting the permeation of oil into it. . Consequently, materials possessing superhydrophobic and superoleophilic character are not suitable for the separation of water-rich oil/water mixtures or oil-in-water emulsions. Inspired by the wetting behavior of fish scales, it was possible to construct underwater superoleophobic surfaces in oil/water. three-phase water/solid systems. The development of simple, inexpensive, environmentally friendly, and easily scalable underwater superhydrophilic and oleophobic materials may lead to a more practical, alternative, and feasible approach for oil/water separations.OLEOPHOBICITYOleophobia is a phenomenon in which a material does not allow oil to spread on it, i.e. the contact angle of oil on the material is >90°. However, oleophobic materials do not guarantee complete non-wetting behavior in a material. To ensure complete non-wetting behavior, the contact angle between material and oil must be > 150°. This is called a superoleophobic material. RELATIONSHIP BETWEEN CONTACT AREA, SURFACE ROUGHNESS AND OLEOPHOBIC BEHAVIOR. This is the Cassie-Baxter equation for the oil contact angle in an oil/water/solid system with a rough surface where, the surface fraction of the solid the contact angle of the droplet d oil on a smooth surface in water the contact angle of the oil droplet on a rough surface in water A smaller area fraction indicates a lesser possibility of the oil droplet coming into contact with the solid surface, and the greater the oil contact angle. in the water. Melamine sponges have a very rough surface, which reveals a fairly low surface fraction of solid and a large contact angle with the oil. It is aboutYoung's equation for the contact angle of oil in water on a flat surface where OA: the oil/air interface tension?OA: the contact angle of oil in air? WA: the tension of the water/air interface?WA: the contact angle of water in the air?OW: the tension of the oil/water interface?OW: the contact angle of the oil in waterSince the surface tension of oil and organic liquids is much lower than that of water, we can see that hydrophilic surfaces in air can become oleophobic in water. The melamine sponge becomes superoleophobic when immersed in water. The underwater oil droplets were almost spherical on the surface of the melamine sponge and exhibited high contact angles (>150°). The rough surface structure and superhydrophilicity of the melamine sponge combine to give a particular wettability characterizing a three-phase oil/water/solid system. MELAMINE SPONGE Melamine sponge is a commercially available three-dimensional porous material consisting of a formaldehyde-melamine-sodium bisulfite. copolymer. These sponges have a superhydrophilic and superoleophilic character. Melamine sponges pre-moistened with water exhibit superhydrophilicity and superoleophobicity and could be used in efficient oil/water separation. Wang et al. presented a simple and inexpensive dipping method for the fabrication of superhydrophilic and underwater superoleophobic polyvinylpyrrolidone (PVP)-modified melamine sponge. Melamine sponges are commercially available three-dimensional porous materials exhibiting underwater superhydrophilicity and superoleophobicity. When immersed in PVP solution to improve its oleophobicity, the as-prepared modified melamine sponge exhibited high separation capacity, enabling the separation of oil/water mixtures continuously for up to 12 h without any increase in the oil content in the filtrate. The excellent performance of PVP-modified melamine sponge in oil/water and its preparation by an industrially feasible process suggest that it has potential applicability in academic and industrial settings. Behavior OF THE RAW SPONGE When a droplet of water was placed on the surface of the raw melamine sponge, it spread and soaked into it instantly. , which gives a contact angle of approximately 0°. The same situation occurred when using an oil droplet. Both processes were completed within 1 s, suggesting both the hydrophilic and oleophilic nature of the melamine sponge in air. The melamine sponge became superoleophobic when immersed in water. When we immersed the melamine sponge in water, the water became trapped in its rough microstructure (a layer of water forms on the skeleton of the sponge) which then formed an oil-composite interface. /water/solid in the presence of oil. The trapped water molecules significantly reduced the contact area between the oil and the sponge surface, resulting in a large contact angle with the oil. The pre-moistened sponge showed similar behavior for other organic solvents like n-hexane, diesel, and isooctane. A water separation experiment, driven by gravity alone, was carried out in which a sponge was fixed between two glass tubes, then an oil/water mixture (1:2 v/v) was poured into the upper tube . The water quickly passed through the pre-moistened melamine sponge and entered the beaker below. During this time, all oil was retained above the sponge, due to the underwater superoleophobicity of the pre-moistened melamine sponge. The flow was quite high. PROBLEM WITH THE RAW SPONGE In the continued experiments ofoil/water separation of diesel/water mixtures, however, diesel penetrated through the melamine sponge within 3 minutes. The raw sponge was unable to separate the emulsions. NECESSARY MODIFICATION OF RAW SPONGE The melamine sponge was modified with polyvinylpyrrolidone (PVP) to improve its oleophobicity by the following process. Polyvinylpyrrolidone (PVP) (C6H9NO)n is a water-soluble polymer. It is soluble in water and other polar solvents. It exhibits excellent wetting properties in solution form and forms films. Therefore, it can be used as a coating agent or as an additive to ensure a good coating. A piece of raw sponge was soaked in 1.0 wt% aqueous PVP for 30 min. The treated sample was dried at 85°C. It was then cured at 150°C for 5 minutes. The obtained sample was washed several times with hot water (50 °C). In the compression procedure, for the emulsion separation experiments, the PVP-modified sponge was compressed into a compact form. CHARACTERIZATION OF THE MODIFIED SPONGE The modified melamine sponge retained the microstructure of the virgin melamine sponge. FESEM images of the pristine sponge showed that the surface of the PVP-modified sponge was compressed into a compact form. fibers in the virgin melamine sponge were quite smooth and plain. Upon treatment with PVP, FESEM images showed that some sort of deposition had taken place on these fibers. This deposition has made the fibers quite rough, which greatly enhances oleophobia, considering the Cassie-Baxter equation and Young's equation mentioned above. Since the PVP aqueous solution used was very dilute (1.0 wt.% strength), any effect of the deposition is only visible at the microstructural level. Despite deposition, the morphology was largely preserved in the modified sponge compared to its original state. For further inspection of the coating on the fibers of the modified sponge, Fourier transform infrared spectroscopy (FTIR) was performed on the raw sponge and the modified sponge. for comparison. In the spectrum of the modified sponge, a peak appears at 1654 cm-1 which is attributed to the C=O groups of PVP. This peak is not present in the raw sponge spectrum. It can therefore be said that the rough coating of the modified sponge, as shown in the FESEM images, is PVP. It successfully adhered to the surface of the sponge fibers. IMPROVED PERFORMANCE AFTER MODIFICATION Using the PVP-modified melamine sponge, we were able to perform continuous separations of diesel/water and n-hexadecane/water mixtures for up to 12 hours, with no oil in the collected water. water throughout the process, indicating the effectiveness of separating the oil/water mixture using the modified sponge. Successful separation of several oil/water and organic solvent/water mixtures, including those containing n-hexadecane, isooctane, and diesel, has been observed. We performed a continuous oil/water separation test by continuously adding water into the upper glass tube while maintaining the height of the oil/water mixture at 7 cm. The absence of oil content in the filtrate further demonstrated the robustness and antifouling properties of the melamine sponge. Oil/water mixtures, including those containing n-hexane, n-hexadecane and isooctane, could separate during these continuous separation tests over a period of at least 1 h while maintaining a value of high flux (L m-2 h-1). This only proves that the PVP, which was deposited on the sponge, has attached itself very strongly to the cotton fiber and fulfills its function by improving the roughness to reinforce the oleophobia. EMULSION SEPARATION Emulsified oil in wastewater is also a problem.