Desalination of aqueous mixture containing nano-sized particles using fouling resistant reverse osmosis membrane

Patent metadata

Field	Value
Publication number	US-2016303516-A1
Application number	US-201415036568-A
Country	US
Kind code	A1
Filing date	Dec 15, 2014
Priority date	Jan 7, 2014
Publication date	Oct 20, 2016
Grant date	—

Abstract

A method for treating a NaCl containing aqueous mixture comprising at least 2 ppm of anionic nano particles comprising the step of passing the mixture through a spiral wound element to produce a permeate stream and concentrate stream wherein the concentrate stream has a relatively higher concentration of nano particles than the permeate stream, wherein the spiral wound element includes a composite polyamide membrane comprising a porous support and a thin film polyamide layer, and wherein the membrane is characterized by having: i) a NaCl rejection and a nano particle rejection of at least 99% when tested with an aqueous solution containing 2000 ppm NaCl and 2 ppm anionic nano particles at 25 C, pH 8 and 1 mPa (150 psi); and ii) a dissociated carboxylate content of at least 0.3 moles/kg of polyamide at pH 9.5 as measured by Rutherford Backscattering (RBS).

First claim

1 . A method for treating a NaCl containing aqueous mixture having a pH of equal to or less than 5 and comprising at least 2 ppm of anionic silica nano particles having a size of 5 to 50 nm and an isoelectric point less than pH 4, the method comprising the step of passing the mixture through a spiral wound element at a flux of less than 50 1/m 2 hr to produce a permeate stream and concentrate stream wherein the concentrate stream has a relatively higher concentration of nano particles than the permeate stream, wherein the spiral wound element includes a composite polyamide membrane comprising a porous support and a thin film polyamide layer, and wherein the membrane is characterized by having:
i) a NaCl rejection and a nano particle rejection of at least 99% when tested with an aqueous solution containing 2000 ppm NaCl and 5 ppm of silica nano particles having a size of 7 nm at 25° C., pH 8 and 1 MPa (150 psi); and ii) a dissociated carboxylate content of at least 0.3 moles/kg of polyamide at pH 9.5 as measured by Rutherford Backscattering (RBS).

2 . The method of claim 1 wherein from 1 to 50 ppm of a polymer is added to the aqueous mixture prior to passing through the spiral wound element wherein the polymer is selected from at least one of: polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl acetate, polyacrylates, poly(oxyethylene), poly(acrylic acid), poly(methacrylic acid), poly(acrylamide), poly(ethylene imine), poly(4-vinylpyridine) and water soluble cellulosics.

3 . The method of claim 2 wherein the polymer comprises polyvinyl alcohol having a Mw of from 600 to 100,000 g/mole.

4 . (canceled)

5 . (canceled)

6 . The method of claim 1 wherein the aqueous mixture has a pH of equal to or less than 3 prior to passing through the spiral wound element.

7 . The method of claim 1 wherein the membrane is characterized by having a dissociated carboxylate content of at least 0.4 moles/kg of polyamide at pH 9.5 as measured by Rutherford Backscattering (RBS).

Assignees

• Dow Global Technologies Llc

Inventors

• Paul Mou
• Roy Abhishek
• Tomlinson Ian A

Classifications

• B01D61/04

  Feed pretreatment · CPC title

• B01D63/10

  Spiral-wound membrane modules · CPC title

• B01D67/0088

  Physical treatment with compounds, e.g. swelling, coating or impregnation · CPC title

• B01D69/10

  Supported membranes; Membrane supports · CPC title

• B01D61/025

  Reverse osmosis; Hyperfiltration · CPC title