What is the ion exchange method? What is the working principle of the ion exchange method?

Ion exchange method

Using a specific cation exchange resin to replace the calcium and magnesium ions in the water with sodium ions. Due to the high solubility of sodium salt, the formation of scale caused by the increase in temperature is avoided. This method is currently the most commonly used standard method. The main advantages are: The effect is stable and accurate, and the process is mature. Water softening equipment in this way is generally called “ion exchanger” (because most of the sodium ion exchange resin is used, it is also called “sodium ion exchanger”).

The working principle of the ion exchange method

Ion exchange resin is a polymer with corresponding functional gene groups. In general, conventional sodium ion exchange resins contain a large amount of sodium ions.
When the content of calcium and magnesium ions in the water is high, the ion exchange resin can release sodium ions, and the functional gene groups are combined with calcium and magnesium ions, so that the content of calcium and magnesium ions in the water decreases and the hardness of the water decreases. Hard water becomes soft water, which is the working process of water softening equipment.
When a large number of functional gene clusters on the resin are combined with calcium and magnesium ions, the softening ability of the resin decreases. Sodium chloride solution can be used to flow through the resin. At this time, the sodium ion content in the solution is high, and the functional gene clusters will release calcium and magnesium ions. When combined with sodium ions, the resin restores its exchange capacity. This process is called “regeneration”.

Due to the needs of reagent work, the standard workflow of water softening equipment mainly includes:
Five processes: work (sometimes called water production, the same below), backwash, salt absorption (regeneration), slow flush (replacement), and fast flush. All processes of different softened water equipment are very similar, but due to the actual process or the need for control, there may be some additional processes. Any water softening equipment based on sodium ion exchange is developed on the basis of these five processes (among which, fully automatic water softening equipment will increase the brine reinjection process).

Backwashing

After working for a period of time, the equipment will intercept a lot of dirt brought by the raw water on the top of the resin. After the dirt is removed, the ion exchange resin can be completely exposed and the regeneration effect can be guaranteed. The backwashing process is that water flows in from the bottom of the resin and flows out from the top, so that the dirt intercepted by the top can be washed away. This process generally takes about 5-15 minutes.

Salt absorption (regeneration)

the process of injecting salt water into the resin tank. The traditional equipment uses a salt pump to inject the salt water, while the fully automatic equipment uses a dedicated built-in ejector to suck in the salt water (the inlet water must have a certain pressure). In the actual working process, the regeneration effect of salt water flowing through the resin at a slower speed is better than that of simply immersing the resin with salt water. Therefore, the softening water equipment is regenerated by the method of slowly flowing salt water through the resin. This qualified process is generally It takes about 30 minutes, and the actual time is affected by the amount of salt used.

Slow flushing (replacement)

After the salt water flows through the resin layer, the process of slowly flushing all the salt in the resin with raw water at the same flow rate is called slow flushing, because there are still a large number of functional gene groups in this process. Calcium and magnesium ions are exchanged by sodium ions. According to actual experience, this process is the main process of regeneration, so many people call this process replacement. This process is generally the same as the salt absorption time, which is about 30 minutes.

Fast flushing

In order to thoroughly flush the remaining salt, the resin should be flushed with raw water at a flow rate close to the actual work. The final effluent of this process should be soft water that meets the standard. Under normal circumstances, the fast flushing process is 5-15 minutes.

The salt absorption operation of manual water softening equipment refers to the operation method of reverse osmosis pretreatment resin regeneration, and the details are as follows:

After the resin absorbs a certain amount of calcium and magnesium ions, it must be regenerated. The time is about every 48 hours of operation (when the raw water is municipal tap water), it must be regenerated once. The regeneration process is to wash the resin layer with industrial salt in the salt tank, and replace the hardness ions such as calcium and magnesium on the resin. With the regeneration waste liquid discharged out of the tank, the resin restores its softening exchange capacity (the water softener is not available. Iodized salt and calcium salt are used as regenerating agents, and salt is added to the salt tank regularly to ensure the saturation concentration of brine). The regeneration time is recommended at night. After the equipment is shut down, the salt should be absorbed and left overnight. The next day, it must be backwashed and normalized. After the washing step is cleaned, start the host.

Resin regeneration steps: open the salt inlet valve, close the other valves, start the raw water pump, suck all the salt water in the salt tank into the softener, and leave it for more than 4 hours.
Salt washing: After the resin is regenerated, the salt in the softener must be rinsed before it can be used. Follow the manual valve flushing method (including positive flushing and back flushing).

C100E ion exchange resin

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