Electrospun Janus Membrane for Efficient and Switchable Oil-Water Separation

Electrospinning is employed to fabricate a Janus membrane that demonstrates hydrophobic behavior on one surface and hydrophilic behavior on the other. The Janus membrane is fabricated by electrospinning hydrophobic polyvinylidene fluoride (PVDF) on top of a hydrophilic membrane. The hydrophilic membrane is fabricated by electrospinning poly(N-isopropylacrylamide) (PNIPAM) and PVDF blend solution. This Janus membrane exhibits a water separation efficiency of over 99.5% at an ultra-low hydrostatic pressure of 0.7 kPa. The results demonstrate that the membrane can be used to separate both oil and water from oil in water and water in oil emulsions. The top layer of the Janus membrane selectively reduces the liquid entry pressure of one of the liquids in the emulsion and aids in its separation from the emulsion. When the water in oil emulsion contacts the PVDF layer of the Janus membrane, liquid entry pressure of the oil is considerably reduced compared to the liquid entry pressure of water. Thus, the membrane aids in the separation of oil from the emulsion and transmits it through the membrane. Similarly, the Janus membrane with PNIPAM/PVDF blend layer facing up, aids in separating and transmitting the water from oil in water emulsion.