FILTRATION APPARATUS CONTAINING ALKYLATED GRAPHENE OXIDE MEMBRANE

1 . A filtration apparatus, comprising:

a support substrate; and

an alkylated graphene oxide membrane disposed on the support substrate, the alkylated graphene oxide membrane comprising a plurality of graphene oxide layers, each graphene oxide layer including at least one graphene oxide sheet covalently coupled to a chemical spacer, the chemical spacer being of Formula I:

wherein:

A is O, NH, or S;

R 1 is optionally substituted C 1 -C 5 alkyl; and

indicates a point of connection to a carbon atom on the alkylated graphene oxide sheet.

2 . The filtration apparatus of claim 1 , wherein A is O.

3 . The filtration apparatus of claim 1 , wherein R 1 is optionally substituted C 2 -C 5 alkyl.

4 . The filtration apparatus of claim 1 , wherein R 1 is selected from —CH 2 CH 3 , —(CH 2 ) 2 CH 3 , —CH(CH 3 ) 2 , —(CH 2 ) 3 CH 3 , —CH(CH 3 ) 2 CH 2 CH 3 , —CH 2 CH(CH 3 ) 2 , or —C(CH 3 ) 3 , —(CH 2 ) 4 CH 3 , —C(CH 3 ) 2 CH 2 CH 3 , —CH 2 C(CH 3 ) 3 , —(CH 2 ) 2 CH(CH 3 ) 2 , —CH(CH 3 )(CH 2 ) 2 CH 3 , —CH(CH 2 CH 3 ) 2 , —CH(CH 3 )CH(CH 3 ) 2 , and —CH 2 CH(CH 3 )CH 2 CH 3 .

5 . The filtration apparatus of claim 1 , wherein R 1 is —(CH 2 ) 2 CH 3 .

6 . The filtration apparatus of claim 1 , wherein the filtration apparatus has a conductivity rejection rate of at least 50% for synthetic weak black liquor.

7 . The filtration apparatus of claim 1 , wherein the filtration apparatus is further characterized by a flux of greater than 5.0E-04 gallons per square foot per day per psi (GFD/psi) for synthetic weak black liquor.

8 . The filtration apparatus of claim 1 , wherein each of the graphene oxide sheets is not covalently crosslinked to the adjacent graphene oxide sheet.

9 . The filtration apparatus of claim 1 , wherein the support substrate comprises one or more material selected from polypropylene (PP), polystyrene, polyethylene, polyethylene oxide, polyethersulfone (PES), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polymethylmethacrylate, polydimethylsiloxane, polyester, polyolefin, cellulose, cellulose acetate, cellulose nitrate, polyacrylonitrile, glass fiber, quartz, alumina, silver, polycarbonate, nylon, Kevlar or other aramid, and polyether ether ketone.

10 . The filtration apparatus of claim 1 , wherein the graphene oxide membrane has a thickness of about 25 nm to about 5 μm.

11 . The filtration apparatus of claim 1 , wherein the graphene oxide membrane has about 100 to about 600 graphene oxide layers.

12 . The filtration apparatus of any one of claim 1 , wherein the conductivity rejection rate is measured at room temperature.

13 . The filtration apparatus of claim 1 , wherein the filtration apparatus has a conductivity rejection of at least 60% for synthetic weak black liquor, or at least 40% for weak black liquor.

14 . A method of preparing a graphene oxide membrane, comprising:

i) agitating a first mixture of a graphene oxide material and a base in water, thereby exfoliating graphene oxide layers from the graphene oxide material;

ii) adding a C 1 -C 5 alkyl halide to the first mixture to form a second mixture;

iii) heating the second mixture for a period of time at greater than 60° C., thereby forming an alkylated graphene oxide;

iv) removing water from the second mixture to obtain the alkylated graphene oxide;

v) dispersing the alkylated graphene oxide in a solvent, thereby forming an alkylated graphene oxide dispersion; and

vi) casting the alkylated graphene oxide dispersion onto a support substrate, thereby forming the graphene oxide membrane.

15 . The method of claim 14 , wherein the base comprises NaOH, KOH, or a combination thereof.

16 . The method of claim 14 , wherein the graphene oxide material to water in the first mixture are present at a weight ratio of greater than about 1 to 900.

17 . The method of claim 14 , wherein the first mixture further comprises a phase transfer catalyst.

18 . The method of claim 17 , wherein the phase transfer catalyst is selected from tetraoctylammonium halide, benzyltriethylammonium halide, methyltricaprylammonium methyltributylammonium halide, and methyltrioctylammonium halide, hexadecyltributylphosphoniurn halide, and tetra-n-butylammonium halide.

19 . The method of claim 14 , wherein the second mixture is heated for a period of time of about 4 hours to about 24 hours.

20 . The method of claim 14 , wherein the second mixture is heated at a temperature of about 63° C. to about 67° C.

21 . The method of claim 14 , further comprising washing the alkylated graphene oxide obtained from step iv) with chloroform or methanol prior to dispersion.

22 . The method of claim 14 , wherein the solvent in step v) is an aromatic solvent.

23 . The method of claim 22 , wherein the aromatic solvent is selected from benzene, benzonitrile, benzyl alcohol, chlorobenzene, dibenzyl ether, 1,2-dichlorobenzene, 1,2-difluorobenzene, hexafluorobenzene, mesitylene, nitrobenzene, pyridine, tetralin, toluene, 1,2,4-trichlorobenzene, trifluorotoluene, and xylenes.

24 . The method of claim 22 , wherein the aromatic solvent is selected from benzene, chlorobenzene, 1,2-dichlorobenzene, 1,2-difluorobenzene, toluene, 1,2,4-trichlorobenzene, trifluorotoluene, and xylenes.

25 . The method of claim 22 , wherein the aromatic solvent is selected from benzene, chlorobenzene, toluene, and xylenes.

26 . The method of claim 14 , wherein dispersing the alkylated graphene oxide in a solvent in step v) comprises ultrasonication or high shear mixing.

27 . The method of claim 14 , wherein the C 1 -C 5 alkyl halide is C 2 -C 5 alkyl halide.

28 . The method of claim 14 , wherein the C 2 -C 5 alkyl halide is C 2 -C 5 alkyl chloride, C 2 -C 5 alkyl-iodide, or C 1 -C 5 alkyl bromide.

29 - 30 . (canceled)