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

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.

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.