Carbon membranes

1. A process for the production of a carbon membrane comprising:

(i) reacting a mixture of cellulose and hemicellulose with sufficient acid to hydrolyze the cellulose linkages to form oligosaccharides or monosaccharides;

(ii) casting the mixture to form a film,

(iii) drying said film; and

(iv) carbonising said film.

2. A process as claimed in claim 1 wherein said acid is trifluoroacetic acid.

3. A process as claimed in claim 1 wherein a metal salt is added to the mixture of step (i).

4. A process as claimed in claim 3 wherein said metal salt forms 0.5 to 6 wt % of said mixture.

5. A process as claimed in claim 3 wherein said metal salt is iron (III) nitrate.

6. A process as claimed in claim 1 wherein the mixture of cellulose and hemicellulose is provided using wood pulp.

7. A process as claimed in claim 1 wherein steps (i) to (iii) take 7 to 100 days.

8. A process as claimed in claim 7 wherein steps (i) to (iii) take 21 to 35 days.

9. A process as claimed in claim 1 wherein the final carbonisation temperature is 500 to 600° C.

10. A process as claimed in claim 1 wherein the carbonisation step (iv) comprises at least two dwells.

11. A process as claimed in claim 1 wherein step (iv) is effected in the absence of a catalyst.

12. A process as claimed in claim 1 further comprising a regeneration step (v) in which a current is applied across the carbon membrane.

13. A process as claimed in claim 10 wherein said current is 1 to 60 mA.

14. A carbon membrane obtainable by the process of claim 1 .

15. A process for the separation of a gas from a gas mixture comprising said gas, said process comprising passing said gas mixture through a carbon membrane of claim 14 .

16. A process as claimed in claim 15 wherein said membrane is periodically or continuously regenerated by passage of direct current therethrough.

17. A process as claimed in claim 15 wherein the gas being separated is carbon dioxide or hydrogen.