Flame-retardant superhydrophobic coating derived from fly ash on polymeric foam for efficient oil/corrosive water and emulsion separation

Developing novel oil sorbents with both superhydrophobicity and flame resistance reveals an enticing prospect for oil/water separation. In this study, superhydrophobic foam with superior flame retardancy and sorption capability is reported through a simple one-step fabrication route in alkaline water/ethanol system containing dopamine, fly ash (FA) and dodecanethiol (DT). The introduction of FA endows the foam with excellent flame retardancy, and the as-prepared foam reveals improved flame resistance compared with original and polydopamine (PDA) coated foams, The obtained foams can quickly absorb various types of oils up to 34-47 times of their own weight, and the absorbed oils can be repeatedly recovered by a simple vacuum filtration process. The foams can also maintain their high hydrophobicity after long term immersion in different corrosive solutions and oils, and are able to be used for removing the oils from corrosive high-temperature water. More importantly, the foams with FA coating can effectively separate a broad range of oil-in-water emulsions with high efficiency (>93.0%). The outstanding separation property of the as-prepared foams and their eco-friendly, low-energy, and inexpensive fabrication process imply the great potential for oily wastewater treatment and oil spill cleanup.