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What is the principle of ion exchange membranes
2020/11/1
Ion exchange resin is a type of polymer material with ion exchange function.In a solution,it can exchange its own ions with the same number of ions in the solution.According to the properties of exchange groups,ion exchange resins can be divided into two categories:cation exchange resins and anion exchange resins.
Cation exchange resins mostly contain acidic groups such as sulfonic acid(-SO3H),carboxylic acid(-COOH),or phenolic acid(-C6H4OH),where hydrogen ions can exchange with metal ions or other cations in the solution.For example,polymers of styrene and divinylbenzene undergo sulfonation treatment to form strong acidic cation exchange resins.The structural formula can be simply expressed as R-SO3H,where R represents the resin matrix.The exchange principle is as follows
2R-SO3H+Ca2+(R-SO3)2Ca+2H+
This is also the principle of hard water softening.
Anion exchange resins contain alkaline groups such as quaternary amino[-N(CH3)3OH],amino(-NH2),or imine(-NH2).They can generate OH-ions in water and can exchange with various anions.The exchange principle is as follows
R-N(CH3)3OH+Cl-R-N(CH3)3Cl+OH-
Due to the reversible ion exchange process,used ion exchange resins are generally washed with appropriate concentrations of inorganic acids or bases,which can be restored to their original state and reused.This process is called.Cation exchange resins can be washed with dilute hydrochloric acid,dilute sulfuric acid,and other solutions;Anion exchange resins can be treated with solutions such as sodium hydroxide.
Ion exchange resins have a wide range of uses,mainly for separation and purification.For example,it is used for softening hard water and producing deionized water,recovering metals from industrial wastewater,separating rare and precious metals,and separating and purifying antibiotics.
Cation exchange resins mostly contain acidic groups such as sulfonic acid(-SO3H),carboxylic acid(-COOH),or phenolic acid(-C6H4OH),where hydrogen ions can exchange with metal ions or other cations in the solution.For example,polymers of styrene and divinylbenzene undergo sulfonation treatment to form strong acidic cation exchange resins.The structural formula can be simply expressed as R-SO3H,where R represents the resin matrix.The exchange principle is as follows
2R-SO3H+Ca2+(R-SO3)2Ca+2H+
This is also the principle of hard water softening.
Anion exchange resins contain alkaline groups such as quaternary amino[-N(CH3)3OH],amino(-NH2),or imine(-NH2).They can generate OH-ions in water and can exchange with various anions.The exchange principle is as follows
R-N(CH3)3OH+Cl-R-N(CH3)3Cl+OH-
Due to the reversible ion exchange process,used ion exchange resins are generally washed with appropriate concentrations of inorganic acids or bases,which can be restored to their original state and reused.This process is called.Cation exchange resins can be washed with dilute hydrochloric acid,dilute sulfuric acid,and other solutions;Anion exchange resins can be treated with solutions such as sodium hydroxide.
Ion exchange resins have a wide range of uses,mainly for separation and purification.For example,it is used for softening hard water and producing deionized water,recovering metals from industrial wastewater,separating rare and precious metals,and separating and purifying antibiotics.
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