Super-hydrophilic electrospun PAN nanofibrous membrane modified with alkaline treatment and ultrasonic-assisted PANI in-situ polymerization for highly efficient gravity-driven oil/water separation

Polyaniline (PANI) is utilized in numerous membrane-based oil/water emulsion separation systems due to its simple synthesis, low cost, chemical stability, and abundant amino functional groups. However, it is still challenging to benefit from the highest efficiency of the PANI-modified membrane in oil/water separation. Herein, PANI was favorably functionalized electrospun polyacrylonitrile (PAN) nanofiber through the establishment of electrostatic interaction and hydrogen bonding between aniline monomer and alkalinized PAN (APAN) nanofibers followed by aniline polymerization under ultrasonic irradiation (APAN/PANI-S) for high-performance oil/water emulsion separation. The uniform and efficient coating of PANI on APAN nanofiber led to the APAN/PANI-S nanofibrous membrane demonstrating outstanding physical stability in harsh acidic and basic conditions. In addition, the APAN/PANI-S nanofibrous membrane illustrated a super-hydrophilic and underwater super-oleophobic surface nature, which resulted in an extraordinary water flux of about 2289 LMH and oil rejection of around 99.69 % in oil/water separation under the gravity driving force. Furthermore, the homogenous penetration of PANI across the APAN nanofibrous membrane as a result of ultrasound-assisted polymerization caused the APAN/PANI-S nanofibrous membrane to show excellent mechanical stability (∼14.07 MPa) and antifouling properties (water flux of>981 LMH and oil rejection above 98 %) during 15-cycle oil/water emulsion separation. These results indicate that the APAN/PANI-S nanofibrous membrane with superior oil/water separation performance could be a promising candidate from a practical application point of view.