Why has the amount of refined brine water and pure water added increased after replacing the ion membrane in the electrolyzer?

As the operating time of the electrolyzer increases, its current efficiency declines, and the amounts of refined brine water and pure water added gradually decrease! I wonder if anyone has noticed that, after an electrolyzer has its ion membranes completely replaced with new ones, it’s evident that more pure water and concentrated salt water need to be added compared to when old membranes were in use! Logically, no matter what the operating condition of the ion membrane is, as long as the current remains constant, the amount of sodium ions that pass through should remain fixed, because it is the sodium ions that carry the charge through the ion membrane! Then, the current flowing through must require that many sodium ions to pass through the ion membrane, but why does the aforementioned phenomenon occur then?

After replacing the membrane, the anode efficiency of the cell will be better than before; with a constant current, the flow rate of brine entering the cell should increase. As the old membrane is in use for a longer period of time, its water permeability increases, which results in more water seeping back from the anode. After replacing it with a new membrane, less water seeps back from the anode, so more water needs to be added at the cathode. That’s probably how it works; this is just for reference only. Any similarities are purely coincidental.

As the operating time of the ion membrane increases, its current efficiency decreases, and the amount of brine and pure water required also decreases! After an electrolyzer has its ion membranes completely replaced with new ones, it is evident that the amount of pure water and concentrated salt water required is greater than when old membranes are used! This is because after replacing the membrane, the electrolytic efficiency of the cell improves compared to before; with a constant current, the flow rate of brine entering the cell should increase. More water will be added to the cathode!

I can sense an increase in the amount of pure water, but it doesn’t seem that obvious when the amount of brine increases. The increase in pure water volume is mainly due to the improved efficiency of the membrane, which reduces the amount of water that migrates; therefore, to maintain the desired concentration, it is necessary to increase the water volume on the cathode side. Additionally, for the operation of the new membrane, it is generally necessary to maintain an appropriate amount of brine addition and a relatively high concentration of the anode solution, in order to ensure proper formation of the membrane channels. http://bbs.hcbbs.com/thread-147807-1-1.html

With a constant current level, the higher the efficiency, or when the device is just started up, a larger amount of brine is usually added to the electrolyzer. This is because the concentration at the outlet of the electrolyzer is controlled by the process of electrolyzing brackish water; the higher the efficiency, the more dilute the brackish water becomes, so it is necessary to increase the amount of saltwater fed into the electrolyzer. The higher the efficiency, the higher the alkali concentration; consequently, more water is required. Otherwise, a high concentration leads to high electricity consumption.

Of course, higher production requires more raw materials – that’s definitely the case! The improvement in current efficiency merely creates the conditions for increasing production~

I have been thinking about this issue these past two days, and my opinion is that, under ideal conditions, the ion membrane is selective toward cations; conductivity is achieved as sodium ions pass from the anode through the ion membrane to the cathode. However, in actual operation, the hydroxide ions produced at the cathode always tend to migrate toward the anode due to the action of the electrodes. Since ion membranes cannot be perfect enough to completely prevent the migration of hydroxide ions, a small amount of them always migrate from the cathode to the anode, where they together with sodium ions carry out the task of conducting electricity. This leads to a decrease in the amount of sodium ions migrating as part of the effective current, thereby causing product loss. I = I_sodium + I_hydroxide. Therefore, as operation time increases, the ion membrane’s ability to block hydroxide ions gradually decreases, resulting in an increase in the migration of hydroxide ions; simultaneously, the efficiency of sodium ions also declines accordingly. Therefore, the consumption of pure water containing sodium chloride for feeding into the cell decreases as well, in order to maintain the concentration of the electrolyte. On the other hand, due to the reduced efficiency of the ion exchange membrane, an increase in the electromigration of water molecules along with sodium ions also leads to a reduction in the amount of raw materials fed into the cell! ! This is my personal opinion; I hope everyone can give me some advice! !

After the membrane replacement, the current efficiency is high, which also leads to an increased consumption of pure water