Self-assembling 2D nanohydroxyapatite/sepiolite cellulose composite membranes: For ultrafast separation of oil-in-water emulsions with superoleophobic properties underwater

The study utilized hydroxyapatite/sepiolite nanotube composites to prepare a composite membrane by filtration on the surface coated with Polydopamine(PDA). A novel Hap/Sep/PDA composite membrane was constructed. Due to the excellent and extensive oil-water separation performance and wettability of Hap, as well as the outstanding specific surface area and adsorption capacity of sepiolite nanotubes, the prepared Hap/Sep/PDA membrane exhibits excellent oil-water separation performance, anti-pollution properties, and stable corrosion resistance. The separation flux for n-hexane-in-water emulsion can reach 5500 ± 370 L/(m 2 ·h), and the separation efficiency of the composite membrane for four types of oil-in-water emulsions is above 99 %, with the best performance observed for n-hexane-in-water emulsion at 99.2 %. The membrane water contact angle for HS3 composite membrane can reach 148.88 ± 1.25°. After continuous immersion in different acid and alkali environments for one week, the contact angle of HS3 is above 141°, with little change, and it has good underwater oleophobicity. This research indicates that hydroxyapatite can serve as a new generation of membrane separation environmental materials with the potential to provide research for oil-water separation under extreme conditions and salt solution separation.