Ion-Exchange Membranes for the Fabrication of Reverse Electrodialysis Device

This protocol is a noise-free, clean, and sustainable way of producing energy. It can easily solve the energy crisis problem by converting the water salinity gradient into electricity. The method provides a direct list for extending large area membrane with outstanding physiochemical properties for generating efficient power using RED.

The output performance of the RED device can be scaled up and the membrane can be utilized in other electrochemical devices like phoresis and redox flow batteries. Homogeneous solution preparation, filtration, drying, control techniques, wash, membrane treatment, regulate the reproducible membrane performance. The stack alignment and pressure drop optimization are crucial for producing stable device performance.

To prepare a cation exchange membrane, add 5%sulfinitated polyetheretherketone fibers to a 250 milliliter round bottom flask and dissolve the fibers in dimethylacetamide solvent. Then shake the flask for 10 minutes so that all of the ionomer polymers settle to the bottom of the flask. Place the mixture into a silicon oil bath with a magnetic stir bar and vigorously stir the solution at 500 revolutions per minute for 24 hours at 80 degrees Celsius to obtain a homogenous solution.

On the next day, filter 30 milliliters of the solution through a 0.45 micrometer PTFE filter into a circular 18 centimeter diameter glass dish. Use an air blower to remove any bubbles before placing the dish in the oven for 24 hours at 90 degrees Celsius to generate an approximately 50 micrometer thick freestanding membrane. To extract the freestanding membrane, fill the dish with warm distilled water.

After 10 minutes, the freestanding membrane will detach from the dish. To activate the membrane, immerse the membrane in one molar sulfuric acid solution for two hours at 80 degrees Celsius, followed by at least three 10 minute washes with one liter of distilled water at room temperature per wash. Dissolve 10%by weight FAA-3 ionomer solution in NMP solvent for two hours at room temperature and 500 revolutions per minute.

At the end of the incubation, filter approximately 30 milliliters of solution through a 100 micron pore strainer into an 18 centimeter glass Petri dish. After removing any air bubbles, place the dish into a 100 degrees Celsius oven for 24 hours. Use hot distilled water to extract the dried membrane as demonstrated and activate the membrane in one liter of sodium hydroxide for two hours.

Then wash the activated membrane three times with one liter of distilled water per wash as demonstrated. After activation, cut the cation and anion exchange membranes to 49 square centimeters. To fabricate a RED stack, position a three centimeter thick PMMA plate with the electrode facing up and place a rubber gasket and spacer onto the electrode.

Place the cation exchange membrane and the anion exchange membrane on either side of the gasket. Place a silicon gasket and a spacer onto each membrane and place a second PMMA plate onto the second layer of spacers and gaskets. Then use a digital wrench drive with a 25 newton meter force to secure the setup with nuts, bolts, and washers.

When the stack has been assembled, place one titanium mesh electrode coated with a one-to-one mixture of iridium and ruthenium at the end of each plate and use crocodile clips to connect the electrodes to the source meter. At least two hours before the analysis, add five liters of a 0.01 molar low sodium chloride solution and five liters of a 0.6 molar high sodium chloride solution to individual large containers connected to a peristaltic pump and stir the solutions continuously at room temperature. To perform the RED analysis add 0.05 molar rinse solution to a third container and use rubber tubes to connect all three containers through the peristaltic pump and pressure gauges to the RED assembly.

Set the flow rate of the rinse solution to 50 milliliters per minute and the flow rate of the salt solutions to 100 milliliters per minute, and check the tubing to eliminate any crossflow or leakage. Perform a pressure gauge reading to be sure that the reading is stable. After the solutions have run through the stack at least for five minutes, use a source meter connected to both of the electrodes and to the RED stack to measure the reverse electrodialysis output performance by the galvanostat method.

The reverse electrodialysis device acts as a potential candidate for fulfilling the universal demand for future energy crises. The difference in the salinity gradient of the salt concentration gives rise to the open circuit voltage, which depends on the internal resistance of the reverse electrodialysis stack. In this analysis, the maximum power density for the reverse electrodialysis stack was about 0.7 watts per square meter, and the calculated net power density was about 0.65 watts per square meter at a fixed flow rate.

As observed, the power density of the cell increased initially to the maximum current density value before dropping in response to an increase in the internal resistance of the RED stack. It is important to regularly crosscheck the tubing connection, solution crossflow, and liquids for producing efficient and stable said performance. The preparation of a uniform large area membrane will destabilize the cell performance without fouling the membrane and solution leakage.

Furthermore, it work efficiently under stress conditions.