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