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Synthesis of special ion exchange resin(II)

Synthesis of special ion exchange resin(II)

  • 2022-11-09
2、 Amphoteric resin

Amphoteric resin is a kind of ion exchange resin with cation and anion groups in the same resin particle. The two groups in this kind of resin are close to each other, which can combine with each other to meet the ions in the solution, and can exchange ions with cation and anion at the same time. After saturation, only a large amount of water washing is needed to regenerate the resin and restore its original exchange capacity. The two groups of amphoteric resin must be strong acid weak base type, weak acid strong base type or weak acid weak base type. Strong acid strong base resin can not show the characteristics of amphoteric resin.
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The synthesis methods of amphoteric resin are as follows:

1. Functional monomer copolymerization

Such as vinyl sulfonic acid and vinyl pyridine or acrylamide.

2. The weak acid weak base amphoteric resin is prepared by copolymerization and copolymerization of methyl acrylate and functional monomer (such as allylamine) and hydrolysis.

3. Monomer copolymerization and functionalization

For example, copolymerization of styrene and butenedioic anhydride, chloromethylation, amination and hydrolysis; Copolymerization, amination and sulfonation of styrene and vinyl chloride; Copolymerization, chloromethylation, sulfonation and hydrolysis of styrene and acrylonitrile or methyl acrylate; Styrene and divinylbenzene copolymers are chloromethylated, aminated, sulfonated, etc.

4. The cation (or anion) exchange resin absorbs appropriate monomers and polymerizes them. The ion exchange resin used for functionalization is cross-linked, which can be regarded as a cage. The polymer chain polymerized from the absorbed monomer is linear, which can be regarded as a snake. The cross-linked chain and linear chain are twisted together, and the adjacent cation and anion exchange groups are combined with each other, so that the linear chain will not escape. Therefore, it is called snake cage resin. The concept of thermal regeneration is derived from the special properties of such resins: the adsorption amount of salt in hot water is less than that in cold water, or the ion exchange equilibrium of such resins (containing weak acid and weak base groups) will be affected by temperature.

5. Composite resin

It is to wrap the fine powder of anion and cation resins into a ball with a polymer (such as polyvinyl alcohol) with good hydrophilicity. It has a good effect as a heat regeneration resin [70].

Thermal regeneration resin is an amphoteric resin with weak acid and weak base groups. It is used for desalination of brackish water and wastewater and regeneration with hot water. The dissociation degree of hot water is dozens of times higher than that of normal temperature water, and the dissociation at this time will regenerate the resin.

The titration curve of acrylic weak acid resin is not smooth enough. For example, when IRC-50 is used for thermal regeneration, the utilization rate of the group is only 10% (for 1760mg/L NaCl solution). However, judging from the titration curve, the amphoteric resin with carboxylic acid group and dimethylamine group can have a group utilization rate of more than 30% when used for desalination of 29300mg/L NaCl solution.

Another important use of amphoteric resin is to remove salts in polar organic matters by ion retardation method. If the saline sucrose solution is passed into the amphoteric resin column, the strong electrolyte in the solution is trapped by the resin (ion exchange), and the sucrose is discharged with the effluent. Then rinse with water, the weak acid or weak alkali salt on the resin is hydrolyzed, and the inorganic salt exchanged to the resin is also washed out, so that sucrose is separated from the inorganic salt. It is different from the common ion exchange resin desalination method in that acid and alkali regeneration are not required.

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