Membrane for the separation of material mixtures and method for production thereof
The invention relates to a membrane for the separation of material mixtures by the principle of vapor permeation or pervaporation, in particular for the dewatering of organic solvents, comprising at least one support layer and at least one material-selective separation layer located thereon, and a method for production of such a membrane. The material-selective separating layer is made from polyvinyl alcohol, containing at least one metallic element and/or a derivative thereof. The method includes the addition of polyvinyl alcohol to a solvent, adding an organometallic compound to the solvent/polyvinyl alcohol mixture, and then applying the solvent/polyvinyl alcohol/organometallic compound mixture to the support layer as the material-selective separating layer.
1. A membrane for the separation of material mixtures according to vapor permeation or pervaporation methods, especially for the dewatering of organic solvents, the membrane comprising at least one support layer and at least one material-selective separation layer on the support layer, the material-selective separation layer comprising organometallic compounds and polyvinyl alcohol, which contain at least one of a metallic element and metallic element derivative and wherein the organometallic compounds are crosslinked with the polyvinyl alcohol.
2. A membrane according to claim 1 , further comprising the molecular weight of the polyvinyl alcohol being between about 20,000 and about 200,000 g/mol.
3. A membrane according to claim 2 , wherein the molecular weight lies essentially in a region between 100,000 to 150,000 g/mol.
4. A membrane according to claim 1 , wherein the polyvinyl alcohol is made by hydrolysis, and has an hydrolysis degree between about 50 and about 100%.
5. A membrane according to claim 4 , wherein the hydrolysis degree is between about 98% and about 100%.
6. A membrane according to claim 1 , further wherein the polyvinyl alcohol for the formation of the material-selective separation layer is dissolved in a solvent thereby forming a solution.
7. A membrane according to claim 6 , wherein the concentration of the solution lies in between about 0.5 wt. % to about a solubility limit of the polyvinyl alcohol.
8. A membrane according to claim 7 , wherein the concentration is between about 1 wt. % to about 5 wt. %.
9. A membrane according to claim 1 , wherein at least one of the metallic element and its derivative is substantially uniformly distributed in the separation layer.
10. A membrane according to claim 9 , wherein the derivative is titanium dioxide Ti02.
11. A membrane according to claim 1 , wherein the support layer is formed so as to be porous.
12. A membrane according to claim 1 , wherein the support layer is made of at least one of a polymer and a polymer modification.
13. A membrane according to claim 1 , wherein the carrier layer is made of an inorganic material.
14. A membrane according to claim 1 , wherein the support layer consists of an inorganic/organic blended membrane.
15. A method for making a membrane for the separation of material mixtures by permeation or pervaporation methods, especially for the dewatering of organic solvents, said method comprising the steps of:
providing at least one support layer and at least one material-selective separation layer applied to the support layer;
adding polyvinyl alcohol to a solvent;
adding an organometallic compound to the solvent/polyvinyl alcohol mixture;
applying the solvent/polyvinyl alcohol/organometallic compound mixture to the support layer as a material-selective separating layer; and
complexing the organometallic compound for addition to the solvent/polyvinyl alcohol mixture.
16. A method according to claim 15 , wherein the step of complexing results in acetylazation.
17. A method according to claim 15 , wherein the organometallic compound is tetraethylorthotitanate or tetraorthopropylenzirkonate.
18. A method according to claim 15 , wherein the organometallic compound containing solvent/polyvinyl alcohol/organometallic compound mixture after its application to the support layer together with the support layer is subjected to a thermal treatment.
19. A method according to claim 18 , wherein subsequent to the application of the separation layer forming mixture onto the support layer the entire element is subjected to a first thermal treatment at a temperature in the region of 100° for drying.
20. A method according to claim 19 , wherein after the first thermal treatment the entire element is subjected to a second thermal treatment at a temperature in the region of about +120° C. to about +200° C., for cross-linking the support layer with the material-selective layer and for the in situ formation of metal oxides in the material-selective layer.
21. A method according to claim 20 , wherein the temperature of the second thermal treatment is between about 160° C. and about 180° C.