Double-layered cellulose nanofiber material, method of manufacturing, membranes, and use thereof

1. A double-layered material consisting of a cellulose nanofibrous (CNF) layer and a graphene oxide (GO) nanolayer coating, wherein the double-layered material comprises 1-2 wt. % of GO in relation to a total weight of the double-layered material, the GO nanolayer coating has a thickness of about 100-220 nm, the double-layered material has a thickness of 19.3±4.0 μm, and the CNF layer is free of a chemical cross-linker.

2. The double-layered material according to claim 1 , wherein a pore size of the double-layered material is 5-10 nm as measured with the Barrett-Joyner-Halenda (BJH) method.

3. The double layered material according to claim 1 , wherein the double-layered material has one surface with the GO nanolayer coating, wherein the surface zeta potential of the surface with the GO nanolayer coating is below −50 mV.

4. A method for purification of water, comprising passing the water through a double-layered material consisting of a cellulose nanofibrous (CNF) layer and a graphene oxide (GO) nanolayer coating, wherein the double-layered material comprises 1-2 wt. % of GO in relation to a total weight of the double-layered material, the GO nanolayer coating has a thickness of about 100-220 nm, the double-layered material has a thickness of 19.3±4.0 μm, and the CNF layer is free of a chemical cross-linker, such that particles present in said water are removed from the water by said double-layered material.

5. A method for manufacturing a double-layered material, comprising the steps of:

a) obtaining a cellulose nanofibrous (CNF) suspension, dispersing said CNF suspension in water to form a CNF dispersion, and sonicating said CNF dispersion;

b) forming a CNF layer of the CNF dispersion formed in step a) to form a substrate;

c) obtaining a GO suspension in water, dispersing said GO suspension in water to form a GO dispersion, and sonicating said GO dispersion;

d) applying the GO dispersion formed in step c) to the substrate layer as a coating on top of the CNF layer formed in step b) to obtain a double-layered material; and

e) drying the double-layered material obtained in step d);

wherein the substrate consists of the CNF layer the GO nanolayer coating has a thickness of about 100-220 nm, the double-layered material has a thickness of 19.3±4.0 μm, and the CNF layer is free of a chemical cross-linker.

6. The method according to claim 5 , wherein steps b) and d) are performed using vacuum filtration, and in step b) the CNF layer is formed on a substrate filter paper, and further comprising a step f) peeling off the double-layered material from the substrate filter paper.

7. The method according to claim 5 , wherein the double-layered material is formed using roller coating or spray coating.

8. The method of claim 5 , wherein the double-layered material comprises 1-2 wt. % of GO in relation to a total weight of the double-layered material.

9. The double-layered material according to claim 1 , wherein the GO nanolayer coating has a thickness of 100-200 nm.

10. The double-layered material according to claim 1 , wherein the double-layered material is characterized by an increased water permeability (L/m −2 ·L/·h·bar), compared to the water permeability of the CNF layer alone.

11. The double-layered material according to claim 1 , wherein the increased water permeability is increased at least 5-fold, compared to the water permeability of the CNF layer alone.

12. The double-layered material according to claim 1 , wherein the double-layered material comprises standing GO sheets inserted into the CNF layer.