Doped membranes

Abstract

Synthetic membranes for the removal, isolation or purification of substances from a liquid. The membranes include at least one hydrophobic polymer and at least one hydrophilic polymer. 5-40 wt.-% of particles having an average particles size of between 0.1 and 15 μm are entrapped. The membrane has a wall thickness of below 150 μm. Methods for preparing the membranes in various geometries, and use of the membranes for the adsorption, isolation and/or purification of substances from a liquid are explored.

1 . A membrane for the removal of substances from a liquid, the membrane comprising at least one hydrophobic polymer selected from the group consisting of polysulfones, polyethersulfones, polyarylethersulfones, polyamides and polyacrylonitriles and at least one hydrophilic polymer, the membrane comprising 1-40 wt.-% of at least one of hydrophilic particles and hydrophobic particles, the particles having an average diameter of between 0.1 μm and 15 μm. 
     
     
         2 . The membrane according to  claim 1 , wherein the particles have an average diameter of between 0.1 μm and 10 μm. 
     
     
         3 . The membrane according to  claim 1  wherein the hydrophobic particles are chosen from the group consisting of activated carbon, carbon nanotubes, hydrophobic silica, styrenic polymers, polydivinylbenzene polymers and styrene-divinylbenzene copolymers. 
     
     
         4 . The membrane according to  claim 1 , wherein the hydrophilic particles are anion or cation exchange particles. 
     
     
         5 . The membrane according to  claim 4  wherein the anion exchange particles are based on polyquaternary ammonium functionalized styrene divinylbenzene copolymers. 
     
     
         6 . The membrane according to  claim 5  wherein the anion exchange particles are based on polyquaternary ammonium functionalized vinylimidazolium methochloride vinylpyrrolidone copolymers. 
     
     
         7 . The membrane according to  claim 5  wherein the polyquaternary ammonium copolymer is a copolymer of styrene and divinylbenzene with dimethyl(2-hydroxyethyl) ammonium and/or trimethylbenzyl ammonium functional groups. 
     
     
         8 . The membrane according to  claim 1  wherein the membrane is one of a hollow fiber membrane and a flat sheet membrane. 
     
     
         9 . The membrane according to  claim 1  wherein the wall thickness of the hollow fiber is below 150 μm. 
     
     
         10 . The membrane according to  claim 1  wherein the particles are present in an amount of from 20 wt.-% to 35 wt.-% relative to the weight of the membrane. 
     
     
         11 . The membrane according to  claim 1  wherein the membrane is at least one of a microporous membrane, a protein separation membrane and an ultrafiltration membrane. 
     
     
         12 . A method for preparing a hollow fiber membrane comprising at least one hydrophobic polymer selected from the group consisting of polysulfones, polyethersulfones, polyarylethersulfones, polyamides and polyacrylonitriles and at least one hydrophilic polymer, the membrane comprising 1-40 wt.-% of at least one of hydrophilic particles and hydrophobic particles, the particles having an average diameter of between 0.1 μm and 15 μm, the method comprising
 (a) grinding the particles to an average diameter of at least 15 μm in an aqueous solution; 
 (b) combining the at least one hydrophilic and the at least one hydrophobic polymer with the suspension of (a); 
 (c) stirring the polymer particle suspension to obtain a homogeneous polymer solution wherein the particles are suspended; 
 (d) degassing the polymer particle suspension; 
 (e) extruding the polymer particle suspension through an outer ring slit of a nozzle, wherein a center fluid is extruded through an inner opening of the nozzle; 
 (f) immersing the precipitating fiber in a bath of non-solvent; 
 (g) washing the membrane. 
 
     
     
         13 . A method for preparing a flat sheet membrane comprising at least one hydrophobic polymer selected from the group consisting of polysulfones, polyethersulfones, polyarylethersulfones, polyamides and polyacrylonitriles and at least one hydrophilic polymer, the membrane comprising 1-40 wt.-% of at least one of hydrophilic particles and hydrophobic particles, the particles having an average diameter of between 0.1 μm and 15 μm, the method comprising
 (a) grinding the particles to an average diameter of at least 15 μm in an aqueous solution; 
 (b) combining the at least one hydrophilic and the at least one hydrophobic polymer with the suspension of (a); 
 (c) stirring the polymer particle suspension to obtain a homogeneous polymer solution wherein the particles are suspended; 
 (d) degassing the polymer particle suspension; 
 (e) casting the polymer particle suspension as a uniform film onto a smooth surface; 
 (f) washing the membrane. 
 
     
     
         14 . The method according to  claim 12 , wherein the water of (a) is the total amount of water which is needed for forming the final polymer solution. 
     
     
         15 . (canceled) 
     
     
         16 . A method for at least one of the adsorption of compounds, the isolation of compounds and the purification of a liquid, the method comprising preparing a hollow fiber membrane comprising at least one hydrophobic polymer selected from the group consisting of polysulfones, polyethersulfones, polyarylethersulfones, polyamides and polyacrylonitriles and at least one hydrophilic polymer, the membrane comprising 1-40 wt.-% of at least one of hydrophilic particles and hydrophobic particles, the particles having an average diameter of between 0.1 μm and 15 μm, and exposing the at least one of the compounds and the liquid to the membrane. 
     
     
         17 . The method of  claim 16 , wherein the compounds are selected from the group consisting of nucleic acids, unconjugated bilirubin, chenodeoxycholic acid, diazepam, cytokines and endotoxins. 
     
     
         18 . A device for at least one of the adsorption of compounds and purification of a liquid, the device comprising at least one of hollow fiber membranes and flat sheet membranes, the at least one of hollow fiber membranes and flat sheet membranes comprising at least one hydrophobic polymer selected from the group consisting of polysulfones, polyethersulfones, polyarylethersulfones, polyamides and polyacrylonitriles and at least one hydrophilic polymer, the at least one of hollow fiber membranes and flat sheet membranes comprising 1-40 wt.-% of at least one of hydrophilic particles and hydrophobic particles, the particles having an average diameter of between 0.1 μm and 15 μm. 
     
     
         19 . The membrane according to  claim 2  wherein the hydrophobic particles are chosen from the group consisting of activated carbon, carbon nanotubes, hydrophobic silica, styrenic polymers, polydivinylbenzene polymers and styrene-divinylbenzene copolymers. 
     
     
         20 . The membrane according to  claim 2  wherein the hydrophilic particles are anion or cation exchange particles. 
     
     
         21 . The membrane according to  claim 19  wherein the hydrophilic particles are anion or cation exchange particles.