ELECTROSPUN NANOFIBERS FOR OIL-WATER SEPARATION

With the development of industry and urbanization, the fast-growing demand for petroleum products has signifificantly intensifified the exploitation, processing, and transportation of crude oil and its byproducts (Pintor et al., 2016; Sarbatly et al., 2016). However, due to the frequent oil-spill accidents and enormous release of oily sanitary sewage and industrial wastewater, disastrous oil pollution continues to occur around the world (e.g., in Alaska, the Galapagos Islands, France, the Gulf of Mexico, and Bohai Bay in China) (Peterson et al., 2003; Banks, 2003; Diez et al., 2007; Schrope, 2011; Li et al., 2016). Leaked oils in water mainly consist of petroleum hydrocarbon and other toxic chemicals which cause long-term harm to living things in the water and signifificantly threaten human health (Peterson et al., 2003; Munilla et al., 2011) . Conversely, the presence of water in fuel oil products is hazardous for automobiles, ships, and even aeroplanes, since the water may breed microbes in the oil pipeline, affect the lubrication properties of fuel, or etch the cylinder, which would destroy the engines (Wang et al., 2017). Thus effective oilewater separation methods are highly desirable to meet the needs of both oily wastewater remediation and fuel oil purifification.

Many factors need to be taken into consideration to develop an effective oilewater separation method, especially the type of oil/water mixture and its viscosity (Nordvik et al., 1996). Generally, oils form different types of mixtures with water, including oil slicks, oil-in-water emulsions, and water-in-oil emulsions, depending on the oil/water ratio and the forming conditions (Shi et al., 2013).  illustrates the process of generating different oil/water mixtures (Nordvik et al., 1996). Conventional oilewater separation methods, such as gravity separation, skimming, and air flflotation, are useful for the treatment of oil slicks and unstable emulsions but suffer from limitations of low processing effificiency and high operation cost; these methods are also insuffificient to separate stable emulsions. Biological agents and chemical dispersants can break up stable oil/water emulsions, but secondary pollution is often introduced and a relatively long treatment time is needed. Thus alternative methods for oilewater separation are urgently required (Kota et al., 2012; Ma et al., 2016a; Ge et al., 2016; Peng and Guo, 2016).

(A) Map of the oil-polluted shorelines of the Gulf of Mexico. (B) Digital photos showing volunteers cleaning up the oil spill. (C) Kelp after an oil spill. (D) A bird covered in oil.

Paper link：https://www.sciencedirect.com/book/9780323512701/electrospinning-nanofabrication-and-applications