Bilayer electrospun membranes for treating fracking wastewater via membrane distillation

Patent metadata

Field	Value
Publication number	US-11628408-B2
Application number	US-202117342089-A
Country	US
Kind code	B2
Filing date	Jun 8, 2021
Priority date	Jun 9, 2020
Publication date	Apr 18, 2023
Grant date	Apr 18, 2023

Abstract

A bilayer electrospun membranes for treating hydraulic fracking wastewater via membrane distillation, and more particularly to bilayer electrospun membranes having an omniphobic layer to prevent low-surface tension solution wicking and an oleophobic antifouling surface to prevent foulant depositing on the membrane. Nanoparticles are decorated on the omniphobic surface through electrochemical interaction, which is coated with a fluorine monomer on the nanoparticles. A zwitterionic co-polymer is grafted using self-assembly between hydroxy groups on the antifouling surface generated by alkaline treatment and anchor segment epoxy groups on zwitterionic co-polymer.

First claim

What is claimed is:

1. A bilayer electrospun membrane, comprising:
an omniphobic, permeate-facing surface configured to suppress scale formation and low-surface tension compounds from wicking and fouling the membrane; the omniphobic surface comprising nanoparticle fibers decorated or grown thereon through electrochemical interactions; the omniphobic surface further comprising the nanoparticle fibers coated with a fluorine monomer; and
an oleophobic, feedstock-facing surface configured to prevent foulants from depositing on and adsorbing to the membrane; the oleophobic surface comprising a zwitterionic antifouling co-polymer poly(glycidyl methacrylate-sulfobetaine methacrylate) grafted thereto.

2. The membrane of claim 1 wherein the bilayer electrospun membrane is a bilayer polyvinylidene difluoride, electrospun membrane.

3. The membrane of claim 2 wherein the nanoparticle fibers are negatively charged silica nanoparticle fibers.

4. The membrane of claim 2 wherein the fluorine monomer is 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

5. The membrane of claim 2 wherein the omniphobic surface further comprises a positively charged monomer.

6. The membrane of claim 5 wherein the positively charged monomer is cetyltrimethylammonium bromide.

7. The membrane of claim 1 wherein the zwitterionic co-polymer is grafted to the oleophobic surface through epoxy ring-opening reactions.

8. A process comprising the step of fracking wastewater vi membrane distillation using the bilayer electrospun membrane of claim 1 .

9. An electrospun zwitterionic membrane, the membrane comprising:
an omniphobic surface comprising (a) a positively charged cetyltrimethylammonium bromide monomer, (b) negatively charged silica nanoparticle fibers decorated or grown on the cetyltrimethylammonium bromide monomer, and (c) a fluorine monomer coated on the silica nanoparticle fibers; and
an oleophobic surface comprising a zwitterionic antifouling co-polymer poly(glycidyl methacrylate-sulfobetaine methacrylate) grafted thereto through epoxy ring-opening reactions.

10. The electrospun zwitterionic membrane of claim 9 wherein the fluorine monomer is 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

11. A process comprising the step of treating fracking wastewater via membrane distillation using the electrospun zwitterionic membrane of claim 9 .

12. A bilayer membrane distillation membrane for separation of hydraulic fracturing-produced water via membrane distillation, the membrane comprising:
polyvinylidene difluoride-cetyltrimethylammonium bromide fibers configured to face a permeate stream, the polyvinylidene difluoride-cetyltrimethylammonium bromide fibers modified to form an omniphobic surface of the membrane, the omniphobic surface comprising salinized silica nanoparticles; and
alkali-treated polyvinylidene difluoride nanofibers configured to face a feed stream, the polyvinylidene difluoride nanofibers modified to form a hydrophilic surface of the membrane, the hydrophilic surface comprising a zwitterionic poly(glycidyl methacrylate-sulfobetaine methacrylate) polymer grafted to the alkali-treated polyvinylidene difluoride nanofibers.

13. A process comprising the step of treating fracking wastewater via membrane distillation using the bilayer membrane distillation membrane of claim 12 .

14. A process for preparing a polyvinylidene difluoride (PVDF) membrane, the process comprising the steps of:
(a) electrospinning a PVDF polymer solution to form a PVDF fiber membrane;
(b) fabricating an omniphobic surface of the PVDF fiber membrane, comprising the steps of:
contacting the PVDF fiber membrane with a positively charged cetyltrimethylammonium bromide (CTAB) monomer to generate positively charged PVDF-CTAB fibers;
growing negative charged silica nanoparticles on the positively charged PVDF-CTAB fibers through electrostatic absorption interaction;
coating a fluorine monomer on the silica nanoparticles to fabricate the omniphobic surface of the PVDF fiber membrane; and

(c) fabricating an oleophobic surface of the PVDF fiber membrane, comprising the steps of:
contacting the PVDF fiber membrane with an alkaline solution to generate hydroxy groups;
grafting a zwitterionic co-polymer poly(glycidyl methacrylate-sulfobetaine methacrylate) on the hydroxy groups through epoxy ring-opening reactions to fabricate the oleophobic surface of the PVDF fiber membrane.

15. The process of claim 14 wherein the alkaline solution is sodium hydroxide (NaOH).

Assignees

• Univ Arkansas

Inventors

• Almodovar Jorge
• Wickramasinghe Ranil
• Chiao Yu-Hsuan
• Castilla-Casadiego David Alfonso

Classifications

• B01D71/701

  Polydimethylsiloxane · CPC title

• B01D71/401

  Polymers based on the polymerisation of acrylic acid, e.g. polyacrylate · CPC title

• B01D67/00931

  by introduction of specific groups after membrane formation, e.g. by grafting · CPC title

• B01D61/364

  Membrane distillation · CPC title

• B01D71/34

  Polyvinylidene fluoride · CPC title