Method and apparatus for evaluating ex-situ chemical degradation of membranes

1. A method for evaluating ex-situ chemical degradation of a membrane comprising the steps of:

submerging a membrane in an aqueous hydrogen peroxide solution and ferrous iron (Fenton solution) in a reaction vessel with a non-reactive weight configured to maximize exposure of the membrane to free hydroxyl radicals produced from the Fenton solution;

tightly sealing the reaction vessel;

heating the Fenton solution in the reaction vessel at a fixed rate to a predetermined temperature;

holding the Fenton solution in the reaction vessel at the predetermined temperature for a predetermined test period;

cooling the Fenton solution in the reaction vessel to room temperature;

analyzing the Fenton solution for fluoride ions released from the membrane due to exposure to the free hydroxyl radicals; and

determining a fluoride emission rate from the fluoride ions to obtain membrane degradation.

2. The method of claim 1 , further comprising removing the membrane and the non-reactive weight from the Fenton solution prior to analyzing.

3. The method of claim 1 , wherein the non-reactive weight comprises two magnets coated in a non-reactive coating placed on opposing sides of the membrane.

4. The method of claim 1 , wherein the reaction vessel has a single sealable opening providing access to a cavity of the reaction vessel.

5. The method of claim 1 , wherein heating the reaction vessel at a fixed rate is performed in an oven.

6. The method of claim 5 , wherein holding the predetermined temperature is performed in the oven.

7. The method of claim 1 , wherein the predetermined temperature is 80° C. or greater.

8. The method of claim 1 , wherein analyzing the Fenton solution is performed with a meter having an ion selective electrode.

9. The method of claim 1 , wherein the steps are performed on a plurality of membranes, each membrane submerged in Fenton solution in a respective reaction vessel with a respective non-reactive weight.

10. The method of claim 9 , wherein each of the plurality of membranes are identical and the predetermined test period is different for each of the plurality of membranes.

11. The method of claim 9 , wherein the plurality of membranes are each different and the predetermined test period is the same for each of the plurality of membranes.

12. A method for evaluating ex-situ chemical degradation of a membrane comprising the steps of:

placing two magnets coated in a non-reactive coating on opposing sides of the membrane, each magnet having an arcuate surface that directly contacts the membrane to minimize a contact area;

submerging the membrane with the magnets in an aqueous solution of hydrogen peroxide and iron catalyst in a reaction vessel, the magnets maximizing exposure of the membrane to free hydroxyl radicals produced from the aqueous solution;

tightly sealing the reaction vessel;

heating the aqueous solution in the reaction vessel at a fixed rate to a predetermined temperature;

cooling the aqueous solution in the reaction vessel to room temperature after a predetermined test period has lapsed;

analyzing the aqueous solution for fluoride ions released from the membrane due to exposure to the free hydroxyl radicals; and

determining a fluoride emission rate from the fluoride ions to obtain membrane degradation.

13. The method of claim 12 , wherein each magnet is cylindrical in cross-section.

14. The method of claim 12 , wherein the reaction vessel has a single sealable opening providing access to a cavity of the reaction vessel.

15. The method of claim 12 , wherein the predetermined temperature is 80° C. or greater.

16. The method of claim 12 , wherein analyzing the aqueous solution is performed with a meter having an ion selective electrode.

17. The method of claim 12 , wherein the steps are performed on a plurality of membranes, each membrane submerged in aqueous solution in a respective reaction vessel with respective magnets.

18. A method for evaluating ex-situ chemical degradation of a membrane comprising the steps of:

submerging a plurality of membranes in an aqueous solution of hydrogen peroxide and iron catalyst, each membrane submerged in a respective reaction vessel to expose the membrane to free hydroxyl radicals produced from the aqueous solution;

tightly sealing each reaction vessel;

heating at a same time the aqueous solution in each reaction vessel at a fixed rate to a predetermined temperature;

after a first elapsed time, removing one of the respective reaction vessels from the heat and cooling the aqueous solution to room temperature;

after a second elapsed time, removing another of the respective reaction vessels from the heat and cooling the aqueous solution to room temperature, and continuing removing each reaction vessel after a different elapsed time until the plurality of membranes are cooled;

analyzing the aqueous solution of each reaction vessel for fluoride ions released from the membrane due to exposure to the free hydroxyl radicals; and

determining a fluoride emission rate from the fluoride ions to obtain membrane degradation for each of the plurality of membranes.

19. The method of claim 18 , wherein a non-reactive weight is attached to each membrane, each non-reactive weight configured to maximize exposure of the membrane.

20. The method of claim 19 , wherein the non-reactive weight comprises two magnets coated in a non-reactive coating placed on opposing sides of the membrane, each magnet having an arcuate surface as a contact surface.