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Application of ion exchange membrane in electrolysis
1. Function of ion exchange membrane
Selective directional migration of ions (aimed at balancing the ion concentration or charge of the entire solution).
2. The role of ion exchange membranes in electrochemistry
(1) Prevent the occurrence of side reactions and avoid affecting the quality of the produced products; Prevent the occurrence of unsafe factors. (For example, in electrolyzing saturated saline water, a cation exchange membrane is used to prevent Cl2 produced by the anode from entering the cathode chamber and reacting with sodium hydroxide, resulting in impure products; and to prevent explosion caused by mixing with H2 produced by the cathode).
(2) Used for the preparation, separation, purification, etc. of substances.
3. Types of ion exchange membranes
According to the particles that pass through, ion exchange membranes can be classified into various types, mainly including cation exchange membranes, anion exchange membranes, and proton exchange membranes in college entrance examination questions. Cation exchange membranes only allow cations to pass through, preventing anions and gases from passing through. Anion exchange membranes only allow anions to pass through, while proton exchange membranes only allow protons (H+) to pass through. The function of ion exchange membranes is to selectively isolate certain substances by passing certain ions and blocking certain ions.
4. Determination of ion exchange membrane type
According to the principle that the electrolyte solution is neutral, the type of membrane is determined by first writing down the electrode reactions on the cathode and anode poles. Based on the electrode reaction equation, the remaining ions near the electrode are determined. Since the solution near the electrode is electrically neutral, the direction of ion movement is determined, and the type of ion exchange membrane is determined. For example, when electrolyzing saturated saline solution, the cathode reaction equation is 2H++2e -=H2 ↑, which destroys the ionization equilibrium of water in the cathode region and leaves OH -. Na+in the anode region passes through the ion exchange membrane and enters the cathode chamber, combining with OH - to form NaOH. Therefore, the ion exchange membrane in electrolyzing saline solution is a cation exchange membrane.