More than half of ion exchange devices are used for water treatment desalination, and the main types of water treatment desalination are strong acidic hydrogen cation exchange resins and strong alkaline hydroxide anion exchange resins. When hydrogen cation exchange resin comes into contact with water, an ion exchange reaction occurs, and various cations in water are adsorbed on the resin, while the hydrogen ions bound to the cation resin are exchanged. At this time, the water only contains one cation, hydrogen ions. When the hydroxide anion resin comes into contact with water and undergoes an ion exchange reaction, various anions in the water are adsorbed, resulting in only one hydroxide ion in the water. When the water passes through this hydroxide cation resin and then through the hydroxide anion resin, only two types of cations and anions (hydrogen ions and hydroxide ions) will combine to form water, completing the desalination process of water.

1. Principle of resin softening water

Soft water resin is produced by the built-in resin tank of the water softener, which replaces the hardness ions in the water as it passes through. The principle of ion exchange softening method, commonly known as "ion exchange softening method", is as follows: ion exchange water treatment refers to the use of ion exchangers to produce reversible exchange of exchangeable ions in a solution that conforms to the rules of equal substance quantity, resulting in improved water quality without substantial (chemical) changes in the structure of the exchangers. In this water treatment method, only cations participate in the exchange reaction, which is called cation exchange water treatment; Only anions participate in the exchange reaction, which is called anion exchange water treatment; Water treatment with both cations and anions involved in the exchange reaction is called cation anion exchange water treatment. Due to the varying quality of raw water and diverse requirements for effluent quality, there are many types of ion exchange and certain combinations of water treatment methods used to soften, alkali, and salt the raw water. When the ion participating in the exchange reaction in the ion exchanger is sodium ion Na+, this method is called sodium (Na) type ion exchange method, and this exchanger is called sodium (Na) type cation exchange agent. Similar methods include hydrogen (H) type ion exchange method and hydrogen (H) type cation exchange agent.

2. Principle of resin regeneration

After replacing a certain amount of hardness ions such as calcium and magnesium in water with a soft water resin, it will no longer be able to soften the water. At this time, a soft water machine is needed for resin regeneration, which is the reduction regeneration method after resin calcium pollution.

(1) When regenerating strong cation exchange resin with Na solution, it is advisable to adopt a stepwise regeneration method. Start regenerating with a low concentration Na solution, as the Ca2+concentration desorbed from the resin is high at this time, but the Na concentration is low. Even if a small amount of Ca2+Na precipitate is formed, it will be washed away by the solution. Then gradually increase the Na concentration, at which point the Ca2+concentration desorbed from the resin is low and no Na precipitation will form.

(2) Due to the fact that weak cation exchange resin is regenerated using the regenerated waste liquid of strong cation exchange resin. Therefore, while introducing acid, the weak cation exchanger must be fed with dilution water (JF9201 filtered water), and the inlet water volume should not exceed the acid inlet of the exchanger at the liquid level. Also, pay attention to observing the color of the regenerated waste liquid discharged from the weak cation exchanger. If it appears as a white turbid substance, even if the acid concentration is adjusted.

(3) After entering the acid, the weak cation exchanger must be immediately replaced and cleaned with filtered water in JF9201, and the strong cation exchanger must be immediately replaced and cleaned with refined water.

(4) In winter, due to the low temperature of the regeneration solution, calcium pollution is more likely to occur. Therefore, before regeneration, the weak cation exchanger must be cleaned and backwashed, and the pipeline for regenerating waste liquid between the weak cation exchanger and the strong cation exchanger must be backwashed to prevent problems before they occur.

This process takes 2-3 hours inside the water softener and is commonly referred to as backwash regeneration of the water softener. Depending on the model of the water softener, a certain amount of resin rejuvenator (Na) or industrial salt may be required.

Attachment: Softening resin model

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