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 method for processing black liquor comprising:
removing from 90%-99% of lignin present in black liquor via filtering through a filtering membrane comprising:
a substrate; and
stacked non-crosslinked graphene oxide sheets forming a non-crosslinked graphene oxide membrane layer covering the substrate;
wherein the black liquor has pre- and post-filtering properties including:
a pre-filtering total solids concentration of 10 wt %, a temperature of between about 70° C. and about 95° C., and a pH of about 13; and
a post-filtering temperature of between about 70° C. and about 95° C. and a pH of about 13; and
wherein the graphene oxide membrane layer shields the substrate from exposure to the black liquor; and
wherein permeability of the graphene oxide membrane layer as measured by water permeation flux as a function of transmembrane pressure does not decrease after flowing the black liquor through the filtering membrane.
2. The method of claim 1 , wherein the lignin removed from the black liquor is between 95% and 99% of the lignin present in the pre-filtered black liquor.
3. The method of claim 1 , wherein the substrate has a thermal stability limit greater than the temperature of the black liquor and comprises a microporous polymer substrate comprising a polymer with aryl groups.
4. The method of claim 1 , wherein the substrate has a thermal stability limit greater than the temperature of the black liquor and comprises a macroporous polymer substrate comprising at least one of poly(sulfone) and poly(ethersulfone).
5. The method of claim 1 , wherein the graphene oxide membrane layer has a thickness of less than about 300 nm.
6. The method of claim 1 , wherein the substrate has a thermal stability limit greater than the temperature of the black liquor and comprises a microporous polymer substrate comprising a flat polymer sheet having a surface area greater than or equal to about 700 cm 2 .
7. The method of claim 1 , wherein the substrate has a thermal stability limit greater than the temperature of the black liquor and comprises a macroporous polymer substrate comprising flat polymer sheets,
wherein each polymer sheet has a surface area greater than or equal to about 700 cm 2 ,
wherein the filtering membrane comprises membrane sheets, each comprising a polymer sheet and the graphene oxide membrane layer, and
wherein the membrane sheets are rolled around a core tube to form a spiral wound membrane module.
8. The method of claim 1 , wherein the substrate has a thermal stability limit greater than the temperature of the black liquor and comprises a microporous polymer substrate comprising a hollow polymer tube having a surface area greater than or equal to about 100 cm 2 .
9. The method of claim 1 , wherein the substrate has a thermal stability limit greater than the temperature of the black liquor and comprises a macroporous polymer substrate comprising hollow polymer tubes,
wherein each polymer tube has a surface area greater than or equal to about 100 cm 2 ,
wherein the filtering membrane comprises membrane tubes, each comprising a hollow polymer tube and the graphene oxide membrane layer, and
wherein the membrane tubes are combined to form a tubular membrane module.
10. The method of claim 1 , wherein interlayer d-spacings of the stacked graphene oxide layers are in the range of about 3 angstroms to about 10 angstroms.
11. The method of claim 1 , wherein the filtering membrane has a molecular weight cutoff in the range of about 300 Daltons to about 1000 Daltons.
12. A method of processing black liquor comprising:
filtering a stream of black liquor through a filtering membrane comprising:
a polymer substrate; and
stacked non-crosslinked graphene oxide sheets forming a non-crosslinked graphene oxide membrane layer covering the substrate;
wherein the black liquor has pre- and post-filtering properties including:
a pre-filtering total solids concentration of 10 wt %, a temperature of between about 70° C. and about 95° C., and a pH of about 13; and
a post-filtering temperature of between about 70° C. and about 95° C. and a pH of about 13;
wherein the black liquor comprises lignin;
wherein the filtering removes at least 90% of the lignin from the black liquor;
wherein the graphene oxide membrane layer shields the substrate from exposure to the black liquor;
wherein the filtering membrane is configured to have a permeate flux in a range from about 10 kg/h·m 2 to about 30 kg/h·m 2 ; and
wherein permeability of the graphene oxide membrane layer as measured by water permeation flux as a function of transmembrane pressure does not decrease after performing for at least four days filtering the lignin from the black liquor.
13. The method of claim 12 , wherein the filtering membrane remains thermally and mechanically stable for at least 30 days filtering the lignin from the black liquor.
14. The method of claim 12 , wherein the lignin removed from the black liquor is between 95% and 99% of the lignin present in the pre-filtered black liquor.
15. The method of claim 12 , wherein the substrate is a sheet of microporous polymer substrate comprising a polymer with aryl groups having a surface area greater than or equal to about 700 cm 2 ; and
wherein the graphene oxide membrane layer has a thickness of less than about 300 nm.
16. The method of claim 12 , wherein the substrate is a sheet of macroporous polymer substrate comprising at least one of poly(sulfone) and poly(ethersulfone) having a surface area greater than or equal to about 700 cm 2 ; and
wherein the graphene oxide membrane layer has a thickness of less than about 300 nm.
17. The method of claim 12 , wherein the substrate is a macroporous polymer substrate comprising flat polymer sheets;
wherein each polymer sheet has a surface area greater than or equal to about 700 cm 2 ;
wherein the filtering membrane comprises membrane sheets, each comprising a polymer sheet and the graphene oxide membrane layer; and
wherein the membrane sheets are rolled around a core tube to form a spiral wound membrane module.
18. The method of claim 12 , wherein the substrate is a microporous polymer substrate comprising a hollow polymer tube or fiber having a surface area greater than or equal to about 100 cm 2 .
19. The method of claim 12 , wherein the substrate is a macroporous polymer substrate comprising hollow polymer tubes;
wherein each polymer tube has a surface area greater than or equal to about 100 cm 2 ;
wherein the filtering membrane comprises membrane sheets, each comprising a hollow polymer tube and the graphene oxide membrane layer; and
wherein the polymer tubes are combined to form a tubular membrane module.
20. The method of claim 12 , wherein interlayer d-spacings of the stacked graphene oxide layers are in the range of about 3 angstroms to about 10 angstroms; and
wherein the filtering membrane has a molecular weight cutoff in the range of about 300 Daltons to about 1000 Daltons.
21. The method of claim 1 , wherein the graphene oxide membrane layer remains thermally and mechanically stable under a surface flow velocity of the black liquor from about 0.22 to about 0.31 meters/second.
22. A method of processing black liquor comprising:
filtering a stream of black liquor comprising solids including lignin through a filtering membrane comprising a non-crosslinked graphene oxide membrane layer covering a substrate; and
removing at least 90% of the lignin from the black liquor;
wherein the black liquor has pre- and post-filtering properties including:
a pre-filtering total solids concentration of 10 wt %, a temperature of between about 70° C. and about 95° C., and a pH of about 13; and
a post-filtering temperature of between about 70° C. and about 95° C. and a pH of about 13:
wherein permeability of the graphene oxide membrane layer as measured by water permeation flux as a function of transmembrane pressure does not decrease after performing for at least four days filtering the lignin from the black liquor.
23. The method of claim 22 , wherein the filtering membrane remains thermally and mechanically stable for at least 30 days filtering the lignin from the black liquor.
24. The method of claim 22 , wherein the filtering removes at least 95% of the lignin when under from about 25 bar to about 30 bar of transmembrane pressure.