TuffBrane™ AEM 50 (Cl- form)

Dry Form: The membrane can be stored dry for a significant amount of time. However, the membrane has to be conditioned (washed and rinsed) prior to use.

Wet Form: Storage for short and medium time scale (hours up to several weeks) may be done in unsealed containers in 0.5 – 1.5 wt% NaCl solution or comparable neutral pH electrolytes. For storage over a longer time period, a sealed container is recommended using afore said electrolyte with biocide to avoid biological fouling.
 

For standard alkaline fuel cell / electrolysis applications, the membrane should be converted into OH-form by treating it with 0.5 – 1.0 M NaOH or KOH solution:

Put the membrane sample in an aqueous solution of 0.5 – 1.0 M NaOH or KOH overnight at 20°C – 30°C. After thorough rinsing with deionized water (pH ~ 7), the membrane is ready to use. If possible, use closed container free of CO2 (such as a glove box) when conditioning and assembling to avoid CO2 contamination (carbonate formation may affect conductivity). The membrane in OH- form must be stored under wet / humidified and CO2-free conditions, avoid drying out the membrane in OH- form. Long-term storage in dry conditions should be preferably done in carbonate or Cl- form.

For electrochemical CO2 reduction applications, the anion exchange membrane should be converted to the carbonate or bicarbonate form by treating the membrane initially with 0.1 to 0.5 M KOH or NaOH solution and then with 0.1 to 0.5 M water soluble carbonate or bicarbonate salt solutions (such as potassium carbonate or potassium bicarbonate that is dissolved in de-ionized water or distilled water).  Fully submerging the anion exchange membrane into KOH or NaOH solution for 6 to 12 hours and then to the desired carbonate or bicarbonate salt solution for a period of 48-72 hours will be sufficient to fully convert the membrane into either carbonate or bicarbonate form.  After rinsing the membrane (which is in the carbonate form) with deionized water or distilled water, it can be assembled inside the electrochemical setup for CO2 reduction experiments. While the submersion of the membrane into the KOH or NaOH can be skipped, a longer carbonate conditioning time may be required in order to fully convert the membrane to carbonate or bicarbonate form.  Initial conversion to OH- form significantly improves the carbonate ion exchange process due to expanded pore sizes.

For other electrochemical (electrodialysis desalination, acid recovery, salt splitting, etc.) and non-electrochemical applications, the membrane should be converted into the anionic form that is relevant for the intended application.  For example, if the application requires Cl- anions to be transferred through the membrane, then this anion exchange membrane needs to be converted into the Cl- form.  In order to convert this membrane into Cl- form, it needs to be submerged into a 1-2 M salt solution of NaCl or KCl (dissolved in deionized water) for a period of 24-72 hours and then rinsed with deionized water to remove the excess salt from the membrane surface (*Note: TuffBrane™ AEM comes in Cl- form in most cases). If the intended application requires transfer of sulfate anions, then this anion exchange membrane needs to be converted into sulfate form prior to its assembly into the cell.  A neutral salt solution of Na2SO4 or K2SO4 is usually sufficient to achieve the full conversion of membrane into sulfate form after fully submerging the membrane into the salt solution for 24-72 hours at room temperature.