Interfacial coordination mediated surface segregation of halloysite nanotubes to construct a high-flux antifouling membrane for oil-water emulsion separation

Forced surface segregation of hydrophilic nanoparticles on the hydrophobic polymer matrix is considered as the effective strategy to fabricate high performance hybrid membrane for oil/water separation. In this work, the halloysite nanotubes (HNTs) were successively modified with dopamine (PDA) and tannic acid (TA) coatings to obtain the hydrophilic nanoparticles (NPs) of HNTs-DA-TA. Next, the obtained HNTs-DA-TA NPs were blended with polyethersulfone (PES) to prepare the oil/water separation membrane via the phase inversion in the coagulation bath containing Fe3+. We have found that the interfacial coordination between TA and Fe3+ is able to enhance the surface segregation of hydrophilic HNTs-DA-TA NPs on hydrophobic PES membrane, which not only contributes to the formation of asymmetric porous membrane, but also can prevent the loss of nanotubes during the phase transitions. Thanks to these advantages, the water flux of nanocomposite membranes was significantly increased (up to 682 L m(-2) h(-1)), which was similar to 3.4 times than that of the pristine PES membrane (199 L m(-2) h(-1)), whereas the rejection was still kept at a high state. After three cycles of separation, the water flux recovery rate can reach up to 91%, which was also much higher than 56% of the pristine PES.