Electrospun Janus Membrane for Efficient and Switchable Oil–Water Separation

Abstract

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.

Acoustophoretic assembly of millimeter-scale Janus fibers

“…Based on this observation, we assume that the compressibility factor for the monolayer is represented by a hard disk equation of state, 38 À2 . Closing eqn (8) with an equation of state allows us to implement a forward Euler numerical scheme 17 to nd area fraction as a function of position. The parameters used to numerically integrate eqn (8) are shown in Table 1.…”

“…Closing eqn (8) with an equation of state allows us to implement a forward Euler numerical scheme 17 to nd area fraction as a function of position. The parameters used to numerically integrate eqn (8) are shown in Table 1.…”

“…6 Membranes fabricated with Janus bers can be used in traditional chemical engineering operations such as distillation 7 or separation. 8 Janus bers may also serve as substrates for catalytic reactions. 9 While there are many potential applications for Janus bers, the processes for fabricating these types of materials remain limited.…”

Biocompatible Janus Membrane with Double Self‐Healing Ability for Intelligent Anticorrosion

“…[ 3 ] The concept of directional permeability was first introduced in 2010 and has attracted considerable attention in membrane research in recent years. [ 4–16 ] The main idea of directional permeability is to achieve a novel separation performance by having two layers of opposite capabilities. The application of Janus membranes is mainly concentrated in the field of oil–water separation, and they are expected to become a new candidate to replace traditional separation membranes.…”

“…The application of Janus membranes is mainly concentrated in the field of oil–water separation, and they are expected to become a new candidate to replace traditional separation membranes. [ 5–7 ] In recent years, Janus membranes have been extensively applied to battery diaphragms, [ 8–10 ] water collection, [ 11–13 ] and ultra‐fine bubbling. [ 14–16 ] Jiang et al [ 2 ] conducted an in‐depth study on the principle of directional permeation in porous Janus membranes and found that when the hydrophobic layer was placed at the top of the membrane, water easily passed through membrane layers; however, when the hydrophilic layer was placed at the top, water only spread over the membrane surface.…”