Electrospray-Printed Three-Tiered Composite Membranes with Enhanced Mass Transfer Coefficients for Phenol Removal in an Aqueous–Aqueous Membrane Extractive Process

Abstract

The aqueous-aqueous membrane extractive process is an ideal approach to remove recalcitrant organics from highly saline and harsh wastewater. However, it is still challenging to develop highly efficient membranes for the extractive process. In this work, three-tiered polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) nanofiber/nonwoven fabric composite membranes were prepared by electrospinning and electrospray printing for the first time. An ultrathin and defect-free PDMS selective layer was fabricated on the surface of a PVDF/nonwoven fabric nanofibrous substrate by electrospray printing. Meanwhile, the thicknesses of the PDMS selective layer were able to be finely controlled by electrospray printing. The novel three-tiered composite membrane #N3-1 with the thinnest PDMS layer (3.0 ± 0.4 μm) and a thin and porous supporting layer showed an exceptionally high <i>k</i>_<i>0</i> of 37.9 ± 2.8 × 10^-7 m/s and an excellent salt rejection above 99.95% over a 105 h continuous operation. Moreover, #N3-1 exhibited outstanding <i>k</i>_<i>0</i> at feed pH of 2 and 11 over 100 h without loss of salt rejection. In addition, the effects of the nonwoven fabric supporting layer on the phenol mass transfer coefficient (<i>k</i>_<i>0</i>, m/s) of resultant extractive membranes were also studied symmetrically. A thin and porous nonwoven supporting layer #N3 was capable of improving the <i>k</i>_<i>0</i> of resultant composite membrane significantly.