Ion exchange membrane and electrodialysis

Ion exchange membrane and electrodialysis

(1) Classification of ion exchange membranes

①Classification according to the nature of exchangeable ions is similar to ion exchange resins.

②Classification according to membrane structure and function According to the membrane structure and function, ion exchange membranes can be divided into three types: ordinary ion exchange membrane, bipolar ion exchange membrane and mosaic membrane

(2) Working principle of ion exchange membrane

Ion exchange membranes mainly use their selectivity

Li ⁺ >Na ⁺ >NH ₄ ⁺ >K ⁺ >Rb ⁺ >Cs ⁺ >Ag ⁺ >Ti ⁺ >UO ₂ ^{2 +} >Mg ²⁺ >Zn ²⁺ >Co ²⁺ >Cd ²⁺ >Ni ²⁺ > Ca ²⁺ >Sr ²⁺ >Pb ²⁺ >Ba ²⁺

①In electrodialysis, two electrodes are placed in an aqueous salt solution (such as sodium chloride solution), and an electric field is applied.

The core of electrodialysis is ion exchange membrane

Figure 10-28 Salt production electrodialyzer

②The basic principle of membrane electrolysis can be illustrated by the electrolysis of NaCl aqueous solution

2Na++2H ₂ O+2e=2NaOH+H ₂

The reaction in the cathode compartment is:

2CI ^-- 2e=Cl ₂

Electrodialyzers prepared with fluorohydrocarbon monopolar or bipolar membranes have become the main method for preparing sodium hydroxide, replacing other methods for preparing sodium hydroxide

If a layer of cathode catalyst is coated on one side of the membrane, and a layer of anode catalyst is applied to the other side and a certain voltage is applied to the two electrodes, water can be electrolyzed to produce hydrogen at the anode and oxygen at the cathode

(3) Application fields of electrodialysis technology

Since the advent of electrodialysis technology, it has shown great advantages in brackish water desalination, drinking water and industrial water preparation

With the deepening of research on electrodialysis theory and technology, China has made great innovations in the main components and structures of electrodialysis devices

Electrodialysis technology also plays an important role in the treatment of food industry, chemical industry and industrial wastewater

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