Superwetting polymer-decorated SWCNT composite ultrathin films for ultrafast separation of oil-in-water nanoemulsions

Abstract

Functional membranes with a superwetting surface property have been extensively explored to achieve oil–water separation. Here, single-walled carbon nanotube/polydopamine/polyethyleneimine (SWCNT/PD/PEI) composite ultrathin films which have superhydrophilic and underwater superoleophobic properties were successfully prepared and used for the ultrafast separation of surfactant-stabilized oil-in-water nanoemulsions containing oil droplets of tens of nanometers. A SWCNT/PD/PEI composite film with an effective pore size of ∼10 nm and a thickness of ∼160 nm can effectively separate oil-in-water nanoemulsions in an ultrafast manner with fluxes up to ∼6000 L m⁻² h⁻¹ bar⁻¹, which is 10-fold higher than traditional ultrafiltration membranes with a similar rejection property. Meanwhile, this film exhibits excellent pH-stability and antifouling property. This work points a direction for designing and fabricating ultrathin and superwetting films for the effective separation of oil-in-water nanoemulsions or nano-sized oils which are hard to separate by traditional methods. The SWCNT/PD/PEI ultrathin film holds promising potential for purifying emulsified wastewater from industries and daily life and for drinking water treatment.