Source:JASE-W Japanese Smart Energy Products & Technologies

https://www.jase-w.eccj.or.jp/technologies/index.html

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Keywords

Y1

material or partZ4

electricity

E21

ceramic products
AGC Inc.

Ion-Exchange Membrane for the Production of Caustic Soda
Features
The AGC Group has satisfied the ever-changing needs for environmental considerations and safety of themethods for the production of caustic soda. Caustic soda is an essential industrial chemical required inmanufacture of various products including synthetic fibers, paper and pulp, and detergent. It is produced
by electrolyzing the raw material, a solution of sodium chloride. Mercury (in the mercury method) andasbestos (in the diaphragm method) were used for its production in the past. However, as discharge ofthese materials in the environment might become a cause of pollution, the Government of Japan
requested the manufacturers of the products mentioned above to develop new production methods in theearly 1970’s.
In response to this request, the AGC Group began the development of the ion-exchange membrane
method, a method to produce caustic soda and chlorine by electrolyzing sodium chloride solution in thepresence of a selectively permeable ion-exchange membrane which only allows certain ions to passthrough it, in 1974. AGC Inc. developed a fluorine-based ion-exchange membrane for the production ofcaustic soda, “FLEMION™”*, a highly durable activated cathode which could realize significant energy
saving and a electrolyzing technology using them in 1975.
* One of the products by the FORBLUE™ Family, AGC Group offers unique, eco-friendly solutions for separating
various chemicals under the FORBLUE™ Family.

Basic Concept or Summary
Ion-exchange
The ion-exchange membrane method, themembrane
diaphragm method and the mercury method
have been used for producing caustic soda, Chlorine gas
Hydrogen gas
chlorine and hydrogen by electrolyzing
sodium chloride solution (in the electrolysis
soda industry). As only the ion-exchange
membrane method is used in Japan, theSodium
principle of the electrolysis of sodium chloride
Caustic soda
chloride
solution in this method is explained in thesolution
following.
Anode
In the ion-exchange membrane method,
Cathodesodium chloride solution is divided in theanodic and cathodic sides by anion-exchange membrane made of specialresin. The ion-exchange membrane used inthis method has a specific characteristic ofallowing only cations (positively-charged ions)to pass through it while not allowing anions
AnodicCathodic chamberchamber Sodium chloride Water(negatively-charged ions) to do so.
solution
As shown in the figure on the right, chlorine,
caustic soda and hydrogen are produced by electrolyzing sodium chloride solution with the electricity
applied to the solution through the electric terminals while sodium chloride solution and water are supplied
to the cathodic and anodic chambers, respectively, in the ion-exchange membrane method.
As the anodic chamber is filled with sodium chloride solution, there are sodium ions (Na+) and chloride
ions (Cl-) in the chamber. When electricity is applied to the solution, movement of the ions will occur. Since
Na+ ions are cations, they will move from the anodic chamber, through the membrane and into thecathodic chamber, while Cl- ions will remain in the anodic chamber, since they are anions. Then, they will
move to the anode, release electrons and become chlorine gas (Cl2) on the anode.
Meanwhile, part of water supplied into the cathodic chamber has been broken down to hydrogen ions (H+)
and hydroxide ions (OH-). When electricity is applied to the solution, hydrogen ions will move to thecathode, acquire electrons on the cathode and become hydrogen gas (H2). Meanwhile, the hydroxide ionswill move toward the anodic chamber. However, their movement will be blocked by the ion-exchange
membrane and they will remain in the cathodic chamber with the sodium ions which have moved fromanodic chamber. As a consequence, there will be a solution of caustic soda (NaOH) generated in thecathodic chamber.
Source: http://www.jsia.gr.jp/explanation_03.html

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FLEMION™

“FLEMION™” is an ion-exchange membrane for the production of caustic soda highly evaluated by its
users as being a “membrane which works well with extremely low voltage electricity and, thus, is suitablefor energy conservation.”
Effects or Remarks
This ion-exchange membrane method (membrane method) is characterized by not only the fact that nohazardous materials are used in it but also the fact that it enables significant energy conservation. TheAGC Group has realized approx. 40 % of energy reduction compared with the mercury method and thediaphragm method in the caustic soda production, taking advantage of this characteristic.
The AGC Group has not only developed a new method of caustic soda production but also improved andupgraded “FLEMION™” itself. As the production of caustic soda from sodium chloride solution made frompoorly refined raw materials which contains significant amount of impurities is on the increase in certain
areas recently, the group developed “FLEMION™ F8080” in 2011 which can be used with voltage lower
than the voltage used for the previous membranes and, thus, consumes less electric power and which isstrongly resistant to impurities in sodium chloride solution. Developed the “FLEMION F-9010™” achieving
lower voltage and power consumption, and launched it commercially in 2019.
Installation in Practice or Schedule
Domestic

The technology used in the ion-exchange membrane method has been developed into
one of the technologies which represent the technological excellence of Japan, with assistance and efforts made by many people involved in the development including those in thegovernment. Its use in the commercial production began in 1979. The ion-exchange membrane method became the only caustic soda production method used in Japan in 1999.
This technology, which has many advantages including high quality and energy conservation, is being exported to various countries in the world.

Overseas

Overseas, the ion exchange membrane method is mainstream, while the diaphragm
method and mercury method are still used occasionally. Moreover, as the Minamata
Convention on Mercury came into effect, caustic soda production using the mercury
method will be banned by 2025. For this reason, it is expected that more and more manufacturers will switch to the ion exchange membrane method in the future.

Photo credit: AGC Inc.

Contact:

AGC Inc.
AGC Chemicals, FORBLUE Division, FLEMION Business Group
Tel: +81-3-3218-5031
URL: https://www.agc-chemicals.com/jp/ja/fluorine/products/forblue/