2、 Production of detergent
Sodium hydroxide saponified oil can be used to make soap and react with alkyl aromatic sulfonic acid to produce the active component of detergent. In addition, sodium hydroxide can also be used to produce sodium phosphate as a component of detergent.
1) Soap:
Soap manufacturing is the oldest and most extensive use of caustic soda.
Sodium hydroxide has been used for traditional daily use. Until today, the demand for caustic soda for soap, soap and other kinds of washing products still accounts for about 15% of caustic soda.
The main component of fat and vegetable oil is triglyceride (triacylglycerol)
Its alkali hydrolysis equation is:
(RCOO) 3C3H5 (grease)+3NaOH=3 (RCOONa) (higher fatty acid sodium)+C3H8O3 (glycerol)
This reaction is the principle of producing soap, so it is named saponification reaction.
Of course, the R base in this process may be different, but the generated R-COONA can be used as soap.
Common R – are:
C17H33 -: 8-heptadecenyl, R-COOH is oleic acid.
C15H31 -: n-pentadecyl, R-COOH is palmitic acid.
C17H35 -: n-octadecyl, R-COOH is stearic acid.
2) Detergent:
Sodium hydroxide is used to produce various detergents, and even today’s washing powder (sodium dodecylbenzene sulfonate and other components) is also produced from a large amount of caustic soda, which is used to neutralize the excess fuming sulfuric acid after sulfonation reaction.
3、 Textile industry
1) The textile industry often uses sodium hydroxide solution to produce viscose fiber. Artificial fibers, such as rayon, rayon, and rayon, are mostly viscose fibers, which are made from cellulose, sodium hydroxide, and carbon disulfide (CS2) as raw materials into viscose solution, and then spun and condensed.
2) Sodium hydroxide can also be used for fiber treatment and dyeing, and for mercerizing cotton fiber. After the cotton fabric is treated with caustic soda solution, the wax, grease, starch and other substances covering the cotton fabric can be removed, and the mercerizing color of the fabric can be increased to make the dyeing more uniform.
4、 Smelting
1) Use sodium hydroxide to process bauxite to extract pure alumina;
2) Use sodium hydroxide to extract tungstate as raw material for tungsten smelting from wolframite;
3) Sodium hydroxide is also used to produce zinc alloy and zinc ingot;
4) After being washed with sulfuric acid, petroleum products still contain some acidic substances. They must be washed with sodium hydroxide solution and then washed with water to get refined products.
5、 Medicine
Sodium hydroxide can be used as a disinfectant. Prepare 1% or 2% caustic soda water solution, which can be used as a disinfectant for the food industry, and can also disinfect tools, machinery, and workshops contaminated by oil dirt or concentrated sugar.
6、 Paper making
Sodium hydroxide plays an important role in the paper industry. Due to its alkaline nature, it is used in the process of boiling and bleaching paper.
The raw materials for papermaking are wood or grass plants, which contain not only cellulose, but also a considerable amount of non-cellulose (lignin, gum, etc.). Adding dilute sodium hydroxide solution can dissolve and separate non-cellulose components, thus making pulp with cellulose as the main component.
7、 Food
In food processing, sodium hydroxide can be used as an acid neutralizer, and can also be used to peel fruit lye. The concentration of sodium hydroxide solution used for peeling varies with the variety of fruit. For example, 0.8% sodium hydroxide solution is used in the production of canned oranges with full de-coated sugar syrup; For example, sodium hydroxide solution with a concentration of 13%~16% is used to produce sugar water peach.
China’s National Food Safety Standard for the Use of Food Additives (GB2760-2014) stipulates that sodium hydroxide can be used as a processing aid for the food industry, and the residue is not limited.
8、 Water treatment
Sodium hydroxide is widely used in water treatment. In sewage treatment plants, sodium hydroxide can reduce the hardness of water through neutralization reaction. In the industrial field, it is the regenerant of ion exchange resin regeneration. Sodium hydroxide has strong alkalinity and relatively high solubility in water. Because sodium hydroxide has relatively high solubility in water, it is easy to measure the dosage and can be used in various fields of water treatment.
The use of sodium hydroxide in water treatment includes the following points:
1) Eliminate water hardness;
2) Adjust the pH value of water;
3) Neutralize the wastewater;
4) Eliminate heavy metal ions in water through precipitation;
5) Regeneration of ion exchange resin.
9、 Chemical experiment.
In addition to being used as a reagent, it can also be used as an alkaline desiccant because of its strong water absorption and deliquescence. It can also absorb acid gas (for example, in the experiment of sulfur burning in oxygen, sodium hydroxide solution can be put into a bottle to absorb toxic sulfur dioxide).
In short, sodium hydroxide is widely used in many fields, including the manufacturing of chemicals, paper making, aluminum smelting, tungsten smelting, rayon, artificial cotton and soap manufacturing, as well as in the production of dyes, plastics, pharmaceuticals and organic intermediates, the regeneration of old rubber, the production of sodium metal, water electrolysis and inorganic salt production, as well as the production of borax, chromate, manganate, phosphate, etc., which requires a large amount of caustic soda, namely sodium hydroxide.
10、Energy sector
In the field of energy, sodium hydroxide can be used for fuel cell production. Like batteries, fuel cells can provide clean and efficient power for many applications, including transportation, material handling, and fixed, portable and emergency standby power applications. Epoxy resin made by adding sodium hydroxide can be used for wind turbines.
