Sodium Metabisulfite used in industrial fields

Sodium Metabisulfite 

relative density 1.4, soluble in water and glycerin, slightly soluble in ethanol, insoluble in benzene. The solubility of sodium metabisulfite in water increases with the increase of temperature, it is 54g/100mL water at 20℃; it is 81.7g/mL at 100℃. The aqueous solution is acidic, and it will form stable sodium bisulfite after being dissolved in water, which is easy to decompose when wet , exposed to the air, it is easy to slowly oxidize and release SO2, and finally absorb oxygen and be oxidized to Na2SO4.

CAS NO.: 7681-57-4

Chemical formula:Na2S2O5

Division of Sodium metabisulfite 

Sodium metabisulfite is divided into industrial grade and food grade, and its quality indicators are different.

Industrial grade sodium metabisulfite is used in many industries. In the pharmaceutical industry, it is used for the purification of chloroform, phenylpropyl sulfone and benzaldehyde; in the rubber industry, it is used as a coagulant; in the printing and dyeing industry, it is used as a dechlorination agent for cotton cloth after bleaching, as a scouring aid for cotton cloth, and as a mordant for printing and dyeing; in the leather industry For leather treatment, it can make leather soft, plump, tough, waterproof, anti-folding, wear-resistant and other properties; used in the chemical industry to produce hydroxyvanillin, hydroxylamine hydrochloride, etc.; used as a developer in the photosensitive industry.

Food-grade sodium metabisulfite can be used as a bleaching agent and leavening agent for biscuits and cakes, a nutrient retainer for dehydrated vegetables, a fresh-keeping agent for stored fruits, and a bactericidal preservative for brewing and beverages.

The production process of sodium metabisulfite in China

The production process is mainly divided into two types, one is dry method and the other is wet method. Here let me introduce the wet traditional process using sulfur as raw material.

First crush the sulfur into powder, send it into the combustion furnace with compressed air, and carry out natural heating at 600-800°C. The amount of air added is twice the theoretical amount, and the SO2 concentration is 10%-13%. After cooling, dust removal and filtration Finally, the sublimed sulfur and other impurities are removed, and the gas temperature is lowered to about 50°C, and then passed into the series reactors.

Slowly add mother liquor and soda ash solution into the third-stage reactor for neutralization reaction, the reaction formula is as follows

2NaHSO3+Na2CO3=2Na2SO3+CO2↑+H2O 

The resulting sodium sulfite suspension passes through the second-stage and first-stage reactors successively, and absorbs and reacts with SO2 to generate sodium pyrosulfite crystals.

Na2SO3+SO2+H2O=2NaHSO3

2NaHSO3→Na2S2O5+H2O

Sodium Metabisulfite used in industrial fields

1. Water Treatment:

Sodium metabisulfite is employed as a water treatment agent to remove excess chlorine and chloramines from drinking water and wastewater. It acts as a dechlorination agent, ensuring that water is safe for consumption and environmentally friendly when discharged.

2. Food Industry:

In the food industry, sodium metabisulfite serves as a preservative and antioxidant. It helps extend the shelf life of products like dried fruits, fruit juices, wine, and baked goods by inhibiting microbial growth and preventing oxidation.

3. Photography:

Sodium metabisulfite plays a crucial role in photographic development processes. It functions as a reducing agent, helping to develop photographic film and prints by reducing the silver ions to metallic silver.

4. Textile Industry:

Textile manufacturers use sodium metabisulfite in dyeing and printing processes. It acts as a reducing agent to remove excess dye and unwanted color from textiles, ensuring vibrant and consistent coloring.

5. Mining and Ore Processing:

In mineral processing, sodium metabisulfite is employed as a reducing agent to control the oxidation of certain minerals, such as sulfide ores. This facilitates the separation of valuable minerals from gangue materials.

6. Pulp and Paper Industry:

Sodium metabisulfite is utilized in the pulp and paper industry as a bleaching agent and to break down lignin. It helps produce high-quality paper products with improved brightness and whiteness.

7. Leather Industry:

The leather industry uses sodium metabisulfite for tanning and dyeing processes. It helps reduce and fix dyes on leather, ensuring uniform coloration and durability.

8. Chemical Manufacturing:

Sodium metabisulfite is an essential component in various chemical processes. It is used in the production of sulfur dioxide gas, which is a precursor for many chemicals, including sulfuric acid.

9. Electronics and Semiconductor Manufacturing:

In electronics manufacturing, sodium metabisulfite can be used for cleaning and etching semiconductor materials. It aids in the removal of oxidation layers and contaminants from semiconductor surfaces.

10. Oil and Gas Industry:

- Sodium metabisulfite can be used in the oil and gas industry for applications such as scavenging oxygen and reducing corrosion in pipelines and storage tanks.

11. Pharmaceutical Industry:

- Sodium metabisulfite may be used in pharmaceutical processes as an antioxidant or reducing agent, depending on the specific requirements of drug formulations.

12. Environmental Applications:

- Sodium metabisulfite can be used in environmental applications, such as reducing the level of dissolved oxygen in wastewater to prevent corrosion and promote biological treatment.

In conclusion, sodium metabisulfite is a versatile chemical compound with a wide range of industrial applications. Its properties as a reducing agent, preservative, and antioxidant make it indispensable in various sectors, from water treatment and food production to photography and mining. Its diverse uses contribute to the efficiency, quality, and safety of processes and products across multiple industries.