Method of creating greater adhesion between asymmetric PVDF active layer and PEI fiber support to obtain multilayer janus membrane

1 . A multilayer Janus membrane, comprising:

a polyvinylidene fluoride (PVDF) layer;

a polyetherimide (PEI) layer, comprising a plurality of PEI fibers; and

an intermediate layer, comprising copper oxide nanoparticles and at least one polymer selected from vinylidene fluoride and hexafluoropropylene copolymer (PVDF-HFP) and polyacrylonitrile (PAN),

wherein the intermediate layer comprises a plurality of granular particles, and is in contact and between the PVDF layer and the PEI layer, and

wherein the PEI fibers interlock between the granular particles of the intermediate layer.

2 . The multilayer Janus membrane of claim 1 , having a directional wettability, wherein the PVDF layer has a hydrophobic surface, and the PEI layer has a hydrophilic surface.

3 . The multilayer Janus membrane of claim 1 , wherein the PVDF layer has a water contact angle of 130° to 150°.

4 . The multilayer Janus membrane of claim 1 , wherein the PVDF layer has a textured porous surface comprising a plurality of PVDF pores with a mean pore size of 0.58 to 0.62 μm, and

wherein the PVDF pores are interconnected with each other, forming a plurality of vertically aligned channels.

5 . The multilayer Janus membrane of claim 4 , wherein the PVDF pores have openings at the surface, and

wherein the PVDF layer has an average surface roughness of 140 to 180 nm.

6 . The multilayer Janus membrane of claim 1 , wherein the PEI layer has a water contact angle of 40° to 50°.

7 . The multilayer Janus membrane of claim 1 , wherein the intermediate layer comprises copper oxide nanoparticles and PVDF-HFP, and

wherein the intermedia layer exhibits a water contact angle of 150° to 160°.

8 . The multilayer Janus membrane of claim 7 , wherein the granular particles of the intermediate layer form a plurality of particle clusters having non-uniform sizes, and

wherein the granular particles are distributed across the PVDF layer.

9 . The multilayer Janus membrane of claim 7 , wherein the intermediate layer has an average surface roughness of 650 to 700 nm and a mean pore size of 0.55 to 0.60 μm.

10 . The multilayer Janus membrane of claim 1 , wherein the intermediate layer comprises copper oxide nanoparticles and PAN, and

wherein the intermediate layer exhibits a water contact angle of 20° to 40° and has a mean pore size of 0.50 to 0.55 μm.

11 . The multilayer Janus membrane of claim 10 , wherein the granular particles of the intermediate layer are interconnected with a plurality of PAN fibers.

12 . The multilayer Janus membrane of claim 1 , wherein the PEI fibers intermingle in between the granular particles of the intermediate layer and anchors on the surface of the intermediate layer.

13 . The multilayer Janus membrane of claim 1 , wherein the PEI layer have a mean pore size of 0.45 to 0.50 μm.

14 . A method of fabricating a multilayer Janus membrane having a polyvinylidene fluoride (PVDF) layer, an intermediate layer and a polyetherimide (PEI) layer, comprising:

forming a PVDF solution comprising PVDF in the form of powder, lithium chloride and dimethylformamide;

casting the PVDF solution on a sandpaper substrate to form a PVDF coated sandpaper;

immersing the PVDF coated sandpaper in a mixture of water and isopropanol to form a PVDF membrane coated sandpaper having a PVDF layer with a non-textured surface on the top and a textured surface in contact with the sandpaper substrate;

electrospraying an intermediate solution comprising dimethylformamide, copper oxide nanoparticles and at least one polymer selected from vinylidene fluoride and hexafluoropropylene copolymer (PVDF-HFP) and polyacrylonitrile (PAN) onto the non-textured surface of the PVDF membrane, followed by isolating a two layer membrane from the sandpaper substrate;

mounting the two-layer membrane coated sandpaper onto a rotating drum having an aluminum foil substrate, wherein the textured surface of the PVDF is in contact with the aluminum foil substrate;

electrospinning a plurality of PEI fibers from a PEI solution onto the two-layer membrane to form a three-layer membrane, wherein the PEI solution comprises PEI and N-methyl-pyrrolidone; and

drying the three-layer membrane to form the multilayer Janus membrane.

15 . The method of claim 14 , wherein the intermediate layer comprises a plurality of granular particles, and is in contact and between the PVDF layer and the PEI layer, and

wherein the PEI fibers interlock between the granular particles of the intermediate layer.

16 . A method of water membrane distillation, comprising:

flowing a saline solution through a multilayer Janus membrane,

wherein the saline solution comprises saline at a concentration of 1 to 70,000 ppm, and

wherein the multilayer Janus membrane comprises a polyvinylidene fluoride (PVDF) layer, a polyetherimide (PEI) layer, and an intermediate layer comprising copper oxide nanoparticles and at least one polymer selected from vinylidene fluoride and hexafluoropropylene copolymer (PVDF-HFP) and polyacrylonitrile (PAN); thereby

absorbing saline on the multilayer Janus membrane to form a filtered water.

17 . The method of claim 16 , wherein the intermediate layer comprises a plurality of granular particles, and is in contact and between the PVDF layer and the PEI layer, and

wherein the PEI fibers interlock between the granular particles of the intermediate layer.

18 . The method of claim 16 , having a flux of 30 to 40 kg·m −2 ·h −1 , wherein the flowing has a duration of 1 to 60 hours.

19 . The method of claim 16 , having a saline rejection rate of at least 99%, wherein the absorbing has a duration of 1 to 60 hours.

20 . The method of claim 16 , having a constant saline rejection rate with no decline, wherein the absorbing has a duration of 1 to 60 hours.