Black Liquor Concentration by a Membrane Comprising Graphene Oxide on Porous Polymer

Abstract

The disclosed technology includes a membrane-based device configured to concentrate black liquor, which results from papermaking. Certain embodiments may comprise a nanofiltration membrane configured to remove lignin from black liquor, and the nanofiltration membrane may include a first macroporous polymer substrate and a first graphene oxide membrane covering the first macroporous polymer substrate. Some embodiments may comprise a reverse osmosis membrane, which may include a second macroporous polymer substrate and a second graphene oxide membrane covering the second macroporous polymer substrate.

What is claimed is: 
     
         1 . A membrane system comprising a nanofiltration membrane configured to remove lignin from black liquor, the nanofiltration membrane comprising:
 a first macroporous polymer substrate; and   a first graphene oxide membrane covering the first macroporous polymer substrate.   
     
     
         2 . The membrane system of  claim 1 , wherein the first macroporous polymer substrate comprises a polymer with aryl groups. 
     
     
         3 . The membrane system of  claim 2 , wherein the first macroporous polymer substrate comprises at least one of poly(sulfone) and poly(ethersulfone). 
     
     
         4 . The membrane system of  claim 1 , wherein the first macroporous polymer substrate has a thermal stability limit greater than about 70° C. 
     
     
         5 . The membrane system of  claim 1 , wherein the first graphene oxide membrane has a thickness of less than about 300 nm. 
     
     
         6 . The membrane system of  claim 1 , wherein the first microporous polymer substrate comprises a flat polymer sheet, the flat polymer sheet having a surface area greater than or equal to about 700 cm 2 . 
     
     
         7 . The membrane system of  claim 1 , wherein the first macroporous polymer substrate comprises a plurality of the flat polymer sheets rolled around a core tube to form a spiral wound membrane module. 
     
     
         8 . The membrane system of  claim 1 , wherein the first microporous polymer substrate comprises a hollow polymer tube, the hollow polymer tube having a surface area greater than or equal to about 100 cm 2 . 
     
     
         9 . The membrane system of  claim 1 , wherein the first macroporous polymer substrate comprises a plurality of the hollow polymer tubes combined to form a tubular membrane module. 
     
     
         10 . The membrane system of  claim 1 , wherein the first graphene oxide membrane comprises pores in the range of about 3 angstroms to about 10 angstroms. 
     
     
         11 . The membrane system of  claim 1 , wherein the nanofiltration membrane has a molecular weight cutoff in the range of about 300 Daltons to about 1000 Daltons. 
     
     
         12 . The membrane system of  claim 1  further comprising a reverse osmosis membrane configured to remove pulping chemicals from black liquor, the reverse osmosis membrane comprising:
 a second macroporous polymer substrate; and 
 a second graphene oxide membrane covering the second macroporous polymer substrate. 
 
     
     
         13 . The membrane system of  claim 9 , wherein the second macroporous polymer substrate comprises a polymer with aryl groups. 
     
     
         14 . The membrane system of  claim 10 , wherein the second macroporous polymer substrate comprises at least one of poly(sulfone) and poly(ethersulfone). 
     
     
         15 . The membrane system of  claim 9 , wherein the nanofiltration membrane has a first molecular weight cutoff and the reverse osmosis membrane has a second molecular weight cutoff, the second molecular weight cutoff being less than the first molecular weight cutoff. 
     
     
         16 . The membrane system of  claim 9 , wherein the reverse osmosis membrane has a molecular weight cutoff in the range of about 50 Daltons to about 300 Daltons. 
     
     
         17 . A method for processing black liquor, the method comprising flowing black liquor through a membrane system, the black liquor comprising lignin and the membrane system including a nanofiltration membrane comprising:
 a first macroporous polymer substrate; and   a first graphene oxide membrane covering the first macroporous polymer substrate.   
     
     
         18 . The method of  claim 14 , wherein the nanofiltration membrane is configured to remove at least a portion of the lignin from the black liquor. 
     
     
         19 . The method of  claim 14 , wherein the membrane system further includes a reverse osmosis membrane, the reverse osmosis membrane comprising:
 a second macroporous polymer substrate; and   a second graphene oxide membrane covering the second macroporous polymer substrate,   wherein the reverse osmosis membrane has a molecular weight cutoff less than a molecular weight cutoff of the nanofiltration membrane.   
     
     
         20 . The method of  claim 16 , wherein the black liquor further comprises pulping chemicals, and wherein the reverse osmosis membrane is configured to remove at least a portion of the pulping chemicals from the black liquor. 
     
     
         21 . A method for manufacturing a membrane system, the method comprising:
 dispersing graphene oxide powder into water;   separating exfoliated graphene oxide laminates of the graphene oxide powder from unexfoliated graphene oxide laminates of the graphene oxide powder;   depositing the exfoliated graphene oxide laminates on a polymer substrate; and   drying the exfoliated graphene oxide laminates.