High flux hollow fiber ultrafiltration membranes and process for the preparation thereof

Patent metadata

Field	Value
Publication number	US-9364797-B2
Application number	US-201113819692-A
Country	US
Kind code	B2
Filing date	Sep 13, 2011
Priority date	Sep 14, 2010
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

The present invention relates to the production of high flux hollow fiber ultrafiltration membrane prepared from poly(acrylonitrile-co-methacrylic acid), (polysulfone and poly(acrylonitrile-co-methacrylic acid)) and (polysulfone and ion exchange resin (sulfonated polystyrene-divinyl benzene copolymer)) blend and the point-of-use filtration unit there from for water purification and disinfection. The produced membrane has an active layer with pore size which effectively rejects pathogens and other bacteria from contaminated water while allowing the passage of water to produce biologically pure water for drinking. Therefore, the present invention relates to development of hollow fiber ultrafiltration membrane that delivers biologically pure water at a desirable rate, that is at a rate 25-200 liters/m2.h. The membrane performance in terms of flux and rejection efficiency is dependent on polymer material type and surface properties. The hollow fiber membrane with interpenetrated structure prepared from a blend of polysulfone and a copolymer of acrylonitrile and methacrylic acid is advantageous over the membranes made either from polysulfone or the copolymer alone in terms of durability, strength, elasticity, smoothness, flux, separation efficiency, fouling resistance properties. The surface modified blend membranes with acid groups which have smaller pore size and surface charge exhibit further improvement in the separation efficiency. Using the hollow fiber membranes a point-of-use water filtration unit which is simple, compact, inexpensive device that does not require electricity has been developed to produce 150-300 ml/min product water when attached to a tab from overhead tank of about 3 meter height.

First claim

The invention claimed is:

1. A high flux, hollow fiber ultrafiltration polymeric membrane comprising blend of polysulfone (PSF) and copolymer in the ratio ranging between 96:4 to 99.5:0.5 (w/w) wherein copolymer is selected from poly(acrylonitrile-co-methacrylic acid) (PANMA) or sulfonated polystyrene-divinyl benzene copolymer as cation exchange resin (CXR).

2. The high flux, hollow fiber ultrafiltration polymeric membrane of claim 1 , wherein said membrane comprises poly(acrylonitrile-co-methacrylic acid) (PANMA).

3. The high flux, hollow fiber ultrafiltration polymeric membrane of claim 1 , wherein said membrane is useful for water purification, declamation and disinfection.

4. The high flux, hollow fiber ultrafiltration membranes of claim 1 , wherein the outer and inner diameter of the fiber is in the range of 1000 to 1100 micrometer and 700 to 750 micrometer respectively.

5. The high flux, hollow fiber ultrafiltration membranes of claim 1 , wherein the fiber wall thickness is in the range of 125 to 175 micrometer.

6. The high flux, hollow fiber ultrafiltration membranes of claim 1 , wherein said membranes comprises an outer and inner skin layer thickness is in the range of 1.7 to 2 μm.

7. The high flux, hollow fiber ultrafiltration membranes of claim 1 characterized by Nephelometric Turbidity Unit (NTU) reduction percentage is in the range of 98-99.5% from feed water having up to 100 NTU.

8. The high flux, hollow fiber ultrafiltration membranes of claim 1 characterized by bacterial reduction log value of said membrane is in the range of 4 to 6.

9. The high flux, hollow fiber ultrafiltration membranes of claim 1 characterized by molecular weight cut-off (MWCO) is in the range of 20 to 50KDa based on polyethylene glycol separation.

10. The high flux, hollow fiber ultrafiltration membranes of claim 1 characterized by pure water flux is in the range of 80 to 250 l/m 2 .h, bursting pressure is in the range of 45 to 50 psi, flux recovery ratio is in the range of 80 to 95 and separation efficiency of 20 kDa polyethylene glycol is in the range of 60 to 90.

11. The high flux, hollow fiber ultrafiltration membranes of claim 1 characterized by pure water permeability is in the range of 50-200 liters/m 2 .hr at 20 to 25 psi.

12. A water filtration unit comprising a high flux, hollow fiber ultrafiltration polymeric membrane according to claim 1 .

13. The water filtration unit of claim 12 , wherein said unit does not require electricity producing 150-300 ml/min product water when attached to a tab from overhead tank of about 3 meter height.

14. A process for the preparation of high flux, hollow fiber ultrafiltration polymeric membrane and the said process comprising the steps of:
a) dissolving 19-20% w/w polysulphone, 2-5% w/w polyvinylpyrrolidone and 0.2 to 0.8% w/w of a copolymer in 70-80% w/w polar organic solvent under constant stirring at rate in the range of 1400 to 1600 rpm at a temperature in the range of 80° C. to 100° C. for period in the range of 3 to 4 hours followed by pushing at 17 to 20 psi nitrogen pressure to prepare a transparent spinning dope; wherein the copolymer is selected from poly(acrylonitrile-co-methacrylic acid) or sulfonated polystyrene-divinyl benzene copolymer as cation exchange resin (CXR);
b) extruding spinning dope as obtained in step (i) through external orifice of a double orifice spinneret maintaining extrusion rate in the range of 30 to 100 g/minute;
c) flowing water through the internal orifice of a double orifice spinneret maintaining flow rate is in the range of 20 to 50ml/minute;
d) maintaining polymer extrusion rate in the range of 35 to 42 meters/minute for period in the range of 3 to 4 hrs;
e) gelling the outer surface of the extruded hollow fiber in water bath maintained at temperature in the range of 25 to 30° C. followed by washing
with water and immerging in methanol for period in the range of 4 to 5 hrs to obtain hollow fiber ultrafiltration polymeric membrane.

15. A process as claimed in step (a) of claim 14 , wherein organic solvent used is selected from the group consisting of dimethylformamide (DMF), N-Methyl-2-pyrrolidone (NMP) or Dimethyl sulfoxide (DMSO).

16. A process of claim 14 , wherein the membranes were spun with a production rate of 8,400 to 10,800 meters length in a batch.

Assignees

• Reddy Alamuru Venktarami
• Ray Paramita
• Singh Puyam Sobhindro
• Kallem Parashuram
• Maurya Sandipkumar
• Trivedi Jitendra Jaydevprasad
• Council Scient Ind Res

Inventors

• Reddy Alamuru Venktarami
• Ray Paramita
• Singh Puyam Sobhindro
• Kallem Parashuram
• Maurya Sandipkumar
• Trivedi Jitendra Jaydevprasad

Classifications

• B01D71/68 Primary

  Polysulfones; Polyethersulfones · CPC title

• B01D2323/42

  Details of membrane preparation apparatus · CPC title

• B01D61/145

  Ultrafiltration · CPC title

• B01D69/08

  Hollow fibre membranes (manufacture of hollow fibres D01D5/24, D01F1/08) · CPC title

• B01D71/76

  Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 (rubbers in general B01D71/24) · CPC title