Crosslinked cellulosic nanofiltration membranes

Abstract

The present invention relates to a nanofilter formed by using a porous ultrafiltration membrane as a precursor, and carefully controlling reaction conditions so as to maintain sufficient hydrophilic nature of the membrane while causing the pore structure to close to a nanofilter range (less than 400 Daltons). This produces a solvent stable cellulose nanofiltration membrane capable of operating at satisfactory flux in aqueous solutions, and being low binding to organic biomaterials.

1 ) A hydrophilic nanofiltration membrane comprising crosslinked cellulose capable of operation in polar organic solvents. 
     
     
         2 ) The membrane of  claim 1  wherein the polar organic solvent is a dipolar aprotic solvent. 
     
     
         3 ) The membrane of  claim 1  wherein the polar organic solvent comprises aqueous mixtures of polar organic solvents. 
     
     
         4 ) The membrane of  claim 1  wherein the dipolar aprotic organic solvent comprises aqueous mixtures of dipolar aprotic organic solvents. 
     
     
         5 ) A nanofiltration membrane comprising crosslinked cellulose, capable of operation in dipolar aprotic solvents, said membrane comprising a cellulose ultrafiltration membrane reacted with a multifunctional crosslinking reagent through hydroxyl groups in the anhydroglucose units, under conditions whereby sufficient hydroxyl groups are left unreacted to provide a hydrophilic membrane. 
     
     
         6 ) A hydrophilic nanofiltration membrane comprising crosslinked cellulose capable of operation in dipolar aprotic solvents, suitable for removing organic solutes of greater than about 400 Daltons from organic solvent solutions. 
     
     
         7 ) The membrane of  claim 1  further comprising a negative surface charge chemically bonded to its surfaces. 
     
     
         8 ) The membrane of  claim 5  further comprising a negative surface charge chemically bonded to its surfaces. 
     
     
         9 ) The membrane of  claim 6  further comprising a negative surface charge chemically bonded to its surfaces. 
     
     
         10 ) The membrane of  claim 1  further comprising a positive surface charge chemically bonded to its surfaces. 
     
     
         11 ) The membrane of  claim 5  further comprising a positive surface charge chemically bonded to its surfaces. 
     
     
         12 ) The membrane of  claim 6  further comprising a positive surface charge chemically bonded to its surfaces. 
     
     
         13 ) A method of removing organic solutes from organic aqueous or aqueous-organic solvent solutions comprising passing the solution through a hydrophilic crosslinked cellulose nanofiltration membrane, said membrane comprising a cellulose ultrafiltration membrane capable of operation in dipolar aprotic solvents. 
     
     
         14 ) A method of removing organic solutes from organic aqueous or aqueous-organic solvent solutions comprising passing the solution through a crosslinked cellulose nanofiltration membrane, said membrane comprising a cellulose ultrafiltration membrane capable of operation in dipolar aprotic solvents, reacted with a multifunctional crosslinking reagent through hydroxyl groups in the anhydroglucose units, under conditions whereby sufficient hydroxyl groups are left unreacted to provide a hydrophilic membrane. 
     
     
         15 ) The membrane of  claim 1  further comprising the membrane has a support layer. 
     
     
         16 ) The membrane of  claim 5  further comprising the membrane has a support layer. 
     
     
         17 ) The membrane of  claim 6  further comprising the membrane has a support layer. 
     
     
         18 ) The membrane of  claim 1  further comprising the membrane has a support layer capable of operation in dipolar aprotic solvents. 
     
     
         19 ) The membrane of  claim 5  further comprising the membrane has a support layer capable of operation in dipolar aprotic solvents. 
     
     
         20 ) The membrane of  claim 6  further comprising the membrane has a support layer capable of operation in dipolar aprotic solvents. 
     
     
         21 ) The membrane of  claim 1  further comprising the membrane has a support layer formed of a microporous membrane. 
     
     
         22 ) The membrane of  claim 5  further comprising the membrane has a support layer formed of a microporous membrane. 
     
     
         23 ) The membrane of  claim 6  further comprising the membrane has a support layer formed of a microporous membrane. 
     
     
         24 ) The membrane of  claim 1  further comprising the membrane has a support layer formed of a microporous membrane and wherein the microporous membrane is comprised of ultrahigh molecular weight polyethylene. 
     
     
         25 ) The membrane of  claim 5  further comprising the membrane has a support layer formed of a microporous membrane and wherein the microporous membrane is comprised of ultrahigh molecular weight polyethylene. 
     
     
         26 ) The membrane of  claim 6  further comprising the membrane has a support layer formed of a microporous membrane and wherein the microporous membrane is comprised of ultrahigh molecular weight polyethylene.