The Use of Caustic Soda

    Caustic soda is a kind of caustic soda. Caustic soda (scientific name sodium hydroxide) is a strong soluble base. Soda ash (scientific name sodium carbonate) is actually a salt, because it undergoes hydrolysis in water to make the solution alkaline, and because it has some similar properties with caustic soda, it is juxtaposed with caustic soda and is called "two alkalis" in industry. Below is a summary of our uses for sodium hydroxide.

 

1. Papermaking.

The raw materials for papermaking are wood or grass plants, which contain a considerable amount of non-cellulose (lignin, gum, etc.) in addition to cellulose. Sodium hydroxide is used for delignification, and only when the lignin in the wood is removed can fibers be obtained. The non-cellulose components can be dissolved and separated by adding dilute sodium hydroxide solution, so that pulp with cellulose as the main component can be obtained.
2. Refining petroleum.

After being washed with sulfuric acid, petroleum products still contain some acidic substances, which must be washed with sodium hydroxide solution and then washed with water to obtain refined products.
3. Textile.

Cotton and linen fabrics are treated with concentrated sodium hydroxide (caustic soda) solution to improve fiber properties. Man-made fibers such as artificial cotton, artificial wool, artificial silk, etc., are mostly viscose fibers. They are made of cellulose (such as pulp), sodium hydroxide, and carbon disulfide (CS2) as raw materials to make viscose liquid. made by condensation.
4. Printing and dyeing.

After the cotton fabric is treated with caustic soda solution, the wax, grease, starch and other substances covered on the cotton fabric can be removed, and at the same time, the mercerized luster of the fabric can be increased to make the dyeing more uniform.

5. Amend the soil with lime.

In soils, the weathering of minerals may also produce acids due to the formation of organic acids as organic matter decomposes. In addition, the use of inorganic fertilizers such as ammonium sulfate and ammonium chloride will also make the soil acidic. Applying an appropriate amount of lime can neutralize the acidic substances in the soil, making the soil suitable for crop growth and promoting the reproduction of microorganisms. The increase of Ca2+ in the soil can promote the coagulation of soil colloids, which is conducive to the formation of aggregates, and at the same time can supply the calcium needed for plant growth.

6. Make soap.

The main component of soap is the sodium salt of higher fatty acid, which is usually made from oil and sodium hydroxide through saponification reaction. In addition to high-grade fatty acid salts, soap also contains fillers such as rosin, water glass, spices, and dyes. From the structural point of view, the molecule of higher fatty acid sodium contains non-polar hydrophobic part (hydrocarbon group) and polar hydrophilic part (carboxyl group). Hydrophobic groups have lipophilic properties. When washing, the grease in the dirt is stirred and dispersed into fine oil droplets. After contacting with soap, the hydrophobic group (hydrocarbon group) of the higher fatty acid sodium molecule is inserted into the oil droplet, and is combined with the oil molecule by van der Waals force. The hydrophilic group (carboxyl group) which is easily soluble in water extends out of the oil drop and inserts into the water. The main component of soap is NaOH, but NaOH is not soap. Its aqueous solution has a slippery feel and can be used to make soap. Soap is an emulsifier.
The principle is the saponification reaction:

 

CH3COOCH2CH3+NaOH=CH3COONa+CH3CH2OHCH3COONa

 

7. In the metallurgical industry, it is often necessary to convert the active ingredients in the ore into soluble sodium salts in order to remove insoluble impurities. Therefore, it is often necessary to add soda ash (it is also a flux), and sometimes caustic soda is also used. For example, in the smelting process of aluminum, soda ash and caustic soda are used in the preparation of cryolite and the treatment of bauxite. Another example is when tungsten is smelted, the concentrate and soda ash are first roasted into soluble sodium tungstate, and then powdered tungsten is obtained through acid analysis, dehydration, reduction and other processes.

8. In the chemical industry, caustic soda is used for making sodium metal and electrolyzing water. Caustic soda or soda ash is used in the production of many inorganic salts, especially in the preparation of some sodium salts (such as borax, sodium silicate, sodium phosphate, sodium dichromate, sodium sulfite, etc.). Caustic soda or soda ash is also used in the synthesis of dyes, drugs and organic intermediates.
9. Alumina production

The NaOH solution is heated to dissolve the alumina in the bauxite to obtain a sodium aluminate solution. After the solution is separated from the residue (red mud), lower the temperature, add aluminum hydroxide as a seed crystal, and stir for a long time, the sodium aluminate decomposes and separates out aluminum hydroxide, washes it, and calcines it at a temperature of 950-1200 ° C to obtain Alumina products are obtained. The solution after the precipitation of aluminum hydroxide is called mother liquor, which can be recycled after evaporation and concentration. Due to the different crystal structures of gibbsite, boehmite and diaspore, their solubility in caustic soda solution is very different, so different dissolution conditions should be provided, mainly different dissolution temperatures. Gibbsite-type bauxite can be dissolved at 125-140°C, and diaspore-type bauxite can be dissolved at 240-260°C with lime (3-7%) added.

10. Ceramics.

The role of caustic soda in ceramic manufacturing has two points: First, in the firing process of ceramics, caustic soda acts as a diluent. Second, the fired ceramic surface will be scratched or very rough. After cleaning with caustic soda solution, the ceramic surface will be smoother.
11. Disinfection:

Denature the protein of the virus. These are mainly used in the cleaning and disinfection of bottles in the wine industry.
12. Removal of waste water:

Strong sodium oxide adjusts the ph value, treats sewage, and recycles resources.
13. Chemical preparations, industrial additives.

In the pharmaceutical industry, caustic soda is mainly used to alkalize solutions or adjust the pH of medicinal solutions.
14. Electroplating, tungsten refining.

Caustic soda is used as an electroplating solution in metal plating and acts as a conductor.
15. Manufacture of silk Manufacture of rayon.

16. Tanning:

a recycling process for tanning waste ash liquid. On the one hand, between the two steps of sodium sulfide aqueous solution soaking treatment and adding lime powder soaking treatment in the existing expansion process, 30% of the tare weight is increased by 0.3-0.5%. % sodium hydroxide solution treatment step to fully expand the skin fiber to meet the process requirements and improve the quality of semi-finished products.
17. Tanning:

It is used as an alkaline medium in this product and also as a neutralizer. Add the prescribed amount of water into the reaction kettle, then pass in steam to heat up to 90°C, add polyvinyl alcohol while stirring, and after the polyvinyl alcohol is completely dissolved, then cool down to 80°C for the glue. Add hydrochloric acid in a trickle way, continue to stir for 20-30 minutes, add the formula amount of formaldehyde water, keep warm at 78-80°C, let it react for 40-50 minutes, add the prepared 10% sodium hydroxide aqueous solution for neutralization, and cool down to 60 ~70°C, then add the formulated amount of urea for amination treatment, filter the glue solution through a gauze and set it aside for later use.

18. Manufacture of phosphate and manufacture of manganate.
19. Regeneration of old rubber.
20. Detergent chemical industry is used to manufacture formic acid, oxalic acid, borax, phenol, sodium cyanide and soap, synthetic fatty acid, synthetic detergent, etc.
21. In the textile printing and dyeing industry, it is used as a solvent for cotton desizing agent, scouring agent, mercerizing agent, vat dye and Haichang blue dye.
22. Used in the smelting industry to manufacture aluminum hydroxide, aluminum oxide and metal surface treatment agents.
23. In the instrument industry, it is used as acid neutralizer, decolorizer and deodorizer. Adhesive industry is used as starch gelatinizer and neutralizer. It can be used as a peeling agent, decolorizing agent and deodorizing agent for citrus and peaches.
24. Caustic soda can also be used in the manufacture of pesticides.

 

 

The news information released by the platform is only provided as knowledge, and is only for reference and communication of industry insiders, and does not guarantee its accuracy and completeness. You should not use this as a substitute for your own independent judgment, so any information should be at your own risk and has nothing to do with Kemele. If there is any infringement, please contact us to delete!

---

  Next： Uses of ethanolamine