Green fabrication of superhydrophilic and underwater superoleophobic coatings with applications in oil-water separation, photocatalysis and fire-retardance

Abstract Taking advantages of strong chelation capability, fire-resistance, and highly hydrophilicity of phytic acid (PA), we designed and further fabricated PA-Sn@Mg(OH)2 (PA-Sn@MH) compounds to improve fire-resistance of MH. Multifunctional coatings consisted of PA-Sn@MH, TiO2 and waterborne polyurethane (PU) were proved to show instant superhydrophilicity when coated onto various substrates, which also showed superior underwater superoleophobicity under diverse conditions, repeated photocatalysis capability, and fire-resistance. The coated stainless steel (SS) mesh presented excellent and stable superoleophobicity under water and other corrosive/harsh conditions. Therefore, the coated mesh could successfully and quickly separate a series of oil-water mixtures. It owned superior stability that also could separate oil-corrosive liquids (include HCl, NaOH solutions, and even strong corrosive liquid of aqua regia)/NaCl/very hot water mixtures. The intrusion pressure that the surface maximally supported was around 2.3 kPa, and the water flux was as high as 62 L m-2 s-1. Moreover, the coatings could effectively and recycled photodegrade diverse oil and organic dyes, while still maintained its instant superhydrophilicity and superior underwater superoleophobicity, which successfully solved the easy oil-fouling problem of the superhydrophilic surfaces. When the coatings were deposited onto some inflammable substrates such as fabric, sponge, and paper, the coatings could endow them self-quenched flame-resistance. This paper reported an environmentally friendly, low-cost method to fabricate multifunctional coatings that showed very promising application potentials in oil-water separation, photocatalysis, and flame-retardant fields.