How to make sodium chlorite?

How to make sodium chlorite?
The commonly used method for manufacturing sodium chlorite is electrolysis, and of course there are methods such as sulfur dioxide reduction method and metal oxide method to manufacture sodium chlorite.

There are many ways to manufacture chlorous acid. Considering the comprehensive cost, environmental impact, output and other factors, the following methods are often seen.


  1. Electrolysis method: Electrolyze the salt solution in a three-chamber electrolytic cell separated by an ion-exchange membrane, gaseous chlorine dioxide is continuously passed into the shade chamber, and the sodium chlorite solution produced by the reaction is obtained by spray drying. The advantage of this method is that the product has high purity, saving raw materials such as caustic soda, and the cost is low; the disadvantage is that the investment in building a factory is large, and the production process and operation are complicated.

  2. Reduction method: first prepare chlorine dioxide from sodium chlorate, and then react chlorine dioxide with a reducing agent in an alkaline medium to obtain sodium chlorite. Common reducing agents mainly include hydrogen peroxide, zinc powder, lead monoxide, and carbonaceous materials. According to different reducing agents, it can be subdivided into: (1) Metal powder method: use zinc, cadmium, lead, magnesium and other powders, among which zinc powder has a better effect. Chlorine dioxide is reduced with zinc powder to produce zinc chlorite, and then double-decomposed with sodium hydroxide to obtain sodium chlorite. Zinc hydroxide is precipitated and separated to obtain sodium chlorite solution, which is evaporated and crystallized to obtain the finished product. This method reacts violently, has the risk of explosion, and the zinc powder is expensive, which is not conducive to large-scale production. (2) Peroxide method: It is obtained by oxidizing chlorine dioxide with inorganic oxides, such as hydrogen peroxide and sodium peroxide. Usually hydrogen peroxide is used as the reducing agent, which is called the hydrogen peroxide method. The by-product of this method is water, the aftertreatment is simple, the reaction is smooth, the high-purity product is easy to obtain, and the yield is high. It is one of the main methods for industrial production of sodium chlorite at present. The disadvantage is that reducing agents such as hydrogen peroxide are more expensive.

  3. The metal oxide method uses the reduction of suboxides such as lead, manganese, cobalt, nickel, copper, cerium, and iron to become high-valent oxides, reducing chlorine dioxide and reacting with sodium hydroxide. Among these oxides, the lead monoxide method is preferable. This method can recover oxides, regenerate them into low atomic valence compounds, and recycle them. The disadvantage is that the reaction is more complicated and the lead compound is more toxic.

  4. The carbonaceous material method is obtained by reducing chlorine dioxide with carbonaceous materials in an alkaline medium. In order to avoid the reaction of carbon dioxide generated by the reaction with sodium hydroxide to form sodium carbonate, calcium hydroxide can be added to form calcium carbonate Precipitate out. The reducing agent of this method needs to be ground very finely, and the dosage is very large; and the concentration of the lye needs to be very dilute, so that the improvement of the concentration of the solution is limited to a certain extent.

  5. Chlorine Dioxide Industrial Act:The Chlorine Dioxide Industrial Process is a method commonly used to manufacture sodium chlorite. The following is an introduction to the manufacture of sodium chlorite by the chlorine dioxide industrial method:

  •  Oxidant preparation: First, an oxidant solution of chlorine dioxide (ClO2) is prepared. Commonly used oxidants are sodium chlorate (NaClO3) and concentrated sulfuric acid (H2SO4). After sodium chlorate solution and sulfuric acid are mixed, they react under appropriate temperature and reaction conditions to produce chlorine dioxide gas.

  • Sodium chlorite generation: chlorine dioxide gas is cooled by a condenser and converted into sodium chlorite (NaClO2) through a series of chemical reactions. The process involves reacting chlorine dioxide gas with an alkaline substance, such as sodium hydroxide, to produce a sodium chlorite solution.

  • Purification and concentration: After sodium chlorite is generated, the solution needs to go through a series of purification steps to remove impurities to obtain high-purity sodium chlorite. Purification may include steps such as filtration, precipitation and washing.

  • Concentration and stability adjustment: The purified sodium chlorite solution needs to be concentrated to achieve the desired concentration. Concentration can be achieved by evaporation or other suitable methods. At the same time, in order to ensure the stability of sodium chlorite, it may be necessary to adjust the pH value and temperature of the solution.

  • Storage and Packaging: Finally, the high-purity sodium chlorite solution will be stored and packaged. Sodium chlorite solutions are usually stored in dedicated containers, such as plastic buckets or stainless steel containers. During the packaging process, it is necessary to ensure strict compliance with safety operating procedures to ensure the safety of employees and the quality of products.

    Chlorine-Dioxide-Industrial Act.webp

Because the electrolysis method is the most commonly used one, we will divide it into two parts, one is the laboratory electrolysis method to produce chlorous acid, and the other is the industrial electrolysis method to produce sodium chlorite to introduce.

How to make sodium chlorite in the lab?

In the laboratory, sodium chlorite can be prepared using electrolysis. Here are the basic steps to make sodium chlorite in the lab:


  • Salt (Sodium Chloride, NaCl)

  • Purified water (H2O)

  • Electrolyzer

  • Titanium or platinum electrodes

  • DC power supply

  • pH paper or pH meter

  • Personal protective equipment such as safety glasses, lab gloves, and lab coat


  1. Prepare the electrolyzer: Place two electrodes in the electrolyzer, one as the anode and one as the cathode. Usually a titanium or platinum electrode is used as the cathode, make sure the electrode is completely submerged in the solution.

  2. Prepare a saline solution: Dissolve an appropriate amount of table salt (sodium chloride) in purified water to prepare a saline solution. Make sure the table salt is completely dissolved.

  3. Filling the electrolytic cell: Pour the prepared brine solution into the electrolytic cell to ensure that the liquid level is higher than the electrodes.

  4. Connect the power supply: Connect the anode and cathode to the positive and negative poles of the DC power supply respectively. Set appropriate current and voltage values.

  5. Start electrolysis: Turn on the power to start the electrolysis process. During electrolysis, chlorine ions (Cl-) are oxidized at the anode to produce chlorine gas (Cl2), while reduction reactions occur at the cathode to produce hydrogen gas (H2) and hydroxide ions (OH-).

  6. Sodium chlorite is collected: As the electrolysis proceeds, chlorine and hydrogen gases are evolved, forming sodium chlorite (NaClO) in solution. Sodium chlorite will cause the solution to take on the properties of a bleach.

  7. pH adjustment: Use pH paper or a pH meter to measure the pH of the solution. If necessary, the pH of the solution can be adjusted to bring it into the proper range by adding an acid or base.

  8. STORAGE AND USE: Transfer the prepared sodium chlorite solution to an appropriate container and store properly. When using, dilute as needed and follow relevant safety guidelines.

It should be noted that when preparing sodium chlorite in the laboratory, laboratory safety regulations must be followed and appropriate personal protective measures must be taken.

This includes wearing safety glasses, lab gloves, and a lab coat, etc. In addition, work should be done in a well-ventilated area for safety and to prevent the accumulation of harmful gases.

When preparing sodium chlorite in the laboratory, you also need to pay attention to the following:

  • Strictly control the current and voltage values to avoid excessive current density and excessive electrolysis reaction rate, resulting in product quality degradation or danger.

  • Monitor the pH of the solution regularly to ensure it is in the proper range. A pH value that is too high or too low may affect the stability and effectiveness of sodium chlorite.

  • Be careful during operation to avoid the electrolyzer from tipping over or splashing the solution to prevent accidents and chemical damage.

  • When preparing and using sodium chlorite solution, strictly follow the relevant safety operation guidelines and waste disposal guidelines to ensure the safety of the laboratory and the environment.

Finally, it is worth emphasizing that if you do not have sufficient laboratory experience or do not have the necessary equipment and safety measures, it is best to choose to purchase commercially produced sodium chlorite solutions to ensure safety and quality reliability.

The above content is through the laboratory manufacturer sodium chlorite, but if it is produced through industrial methods, it is the same, but the whole environment will become more complicated, and the equipment used will not be the same.

How is sodium chlorite manufactured in a factory setting?

In a factory setting, sodium chlorite (Sodium Hypochlorite) is usually manufactured by electrolysis on an industrial scale. The following are general steps, equipment requirements, and examples:


  • Raw material preparation: Prepare sodium chloride (salt) and purified water as raw materials for preparing sodium chlorite.

  • Electrolyzer preparation: Set up a large electrolyzer with built-in anode and cathode to hold enough solution. Titanium, steel or platinum are usually used as electrode materials to improve corrosion resistance.

  • Solution preparation: Dissolve an appropriate amount of sodium chloride (salt) in purified water to prepare a saline solution.

  • Tank liquid filling: Pour the prepared brine solution into the electrolytic cell to ensure that the liquid level is higher than the electrodes.

  • Electrolysis process: connect the power supply, and adjust the parameters of current and voltage. In the electrolysis process, chlorine gas, hydrogen gas and sodium chlorite are produced through anodic oxidation reaction and cathodic reduction reaction. Chlorine gas is produced at the anode, and hydrogen and sodium chlorite are produced at the cathode.

  • Separation and collection: Separate chlorine gas and hydrogen gas through corresponding separation and collection devices, and collect the generated sodium chlorite.

  • Adjust the pH value: According to the product requirements, use an appropriate amount of alkaline substances (such as sodium hydroxide) to adjust the pH value of the solution to achieve the desired concentration and stability of sodium chlorite.

  • Filtration and storage: Remove impurities through a filtration device to make the sodium chlorite solution more pure. The sodium chlorite solution is then transferred to an appropriate storage container for safe storage and ease of transport.

Equipment requirements:

Large electrolyzer: used to hold enough solution and place electrodes.

Electrodes: Anodes and cathodes made of corrosion-resistant materials such as titanium, steel, or platinum.

Corresponding power supply system: provide appropriate current and voltage to drive the electrolysis process.

Separation and collection device: used to separate and collect the gas and liquid products produced.

pH adjustment device: used to adjust the pH value of the solution.

For example:

Suppose there is a chemical company specializing in the production of sodium chlorite, and their production process is as follows:

  • Raw material preparation: Purchase high-purity sodium chloride (salt) and purified water from suppliers as raw materials.

  • Electrolyzer preparation: A series of large electrolyzers, each equipped with anodes and cathodes, are set up in the factory. The anode and cathode are usually made of corrosion-resistant titanium to ensure their stability during electrolysis.

  • Solution preparation: Dissolve a large amount of sodium chloride in purified water to form a high-concentration saline solution. The dissolution process is usually carried out in a batch tank to ensure thorough mixing and dissolution.

  • Tank Filling: Transfer the prepared brine solution into the electrolytic cell, making sure the liquid level is in place so that the electrodes are completely submerged in the solution.

  • Electrolysis process: By connecting the power supply, adjust the appropriate current and voltage parameters to start the electrolysis process. During this process, the chloride ions are oxidized at the anode to produce chlorine gas and reduced at the cathode to produce hydrogen and sodium chlorite. Chlorine gas is vented from the top of the cell, while the sodium chlorite solution is collected through an outlet at the bottom.

  • Adjust the pH value: By adding an appropriate amount of alkaline substance (such as sodium hydroxide), adjust the pH value of the sodium chlorite solution so that it is within the desired range. This can be achieved with an automated control system to ensure product consistency and quality stability.

  • Filtration and storage: Pass the resulting sodium chlorite solution through a filtration device to remove suspended solids and impurities to ensure the purity of the product. Then, the sodium chlorite solution is transferred to a dedicated storage container, labeled and stored in a secure area, pending further packaging and shipment.

This is a simplified example, the actual factory manufacturing process may be more complex, involving more controls and safety measures. Chemical companies must strictly abide by relevant safety and environmental protection regulations in the production process to ensure the safety of employees and the reliability of product quality.

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