Facile approach of eco-friendly superhydrophilic/underwater superoleophobic zinc-functionalized polyurethane foams for continuous oil-water separation

Not only for scientific research but study for continuous oil/water separation is also essential for practical application, especially in the oil industry. Cleaning oily wastewater and oil-spill pollution nowadays have taken much attention due to the rapid development of technology worldwide. Material that exhibits remarkable superwettability toward oil and water is considered a promising candidate, especially for superhydrophilic/superoleophobic material due to its water-wetting behaviour and anti-oil-fouling properties. In this work, the commercial polyurethane foam (PUF) was coated with zinc nanoparticles (Zn-NPs) by using a facile dip-coating method. In addition, PUF-Zn NPs were modified with malic acid (MA) and tetra ethylene glycol (TEG) to achieve superhydrophilicity and formed PUF-Zn-MA-TEG nanocomposite. This material exhibits excellent underwater oil contact angle (OCA ∼ 158°), and water contact angle (WCA ∼ 0°). The water absorption capacity was tested with the result as much as 31.5 g/g from its original weight. Surprisingly, the immiscible oil/water mixture and complicated oil/water emulsion can also be separated with high efficiency (up to 99.5%) and water permeate flux (up to 7000 L m⁻² h⁻¹). Based on its long-term performance and high mechanical stability and durability, the developed nanocomposite could be used in a broad range of industrial applications.