53-sodium hydroxide

Pls input...Sodium hydroxide (commonly known as caustic soda) is a strong alkaline inorganic compound. It appears as a white solid (in flake, granular, or block form) at room temperature, is highly soluble in water (releasing a large amount of heat during dissolution), and exhibits strong corrosiveness. As a basic chemical raw material, it is used in the production of soap, detergents (for saponification reactions), synthetic fibers (e.g., viscose fiber), and dye intermediates.

1. Sodium hydroxide, also known as caustic soda, caustic soda, caustic soda, caustic soda tablet, is an inorganic compound with the chemical formula NaOH and a relative molecular weight of 39.9970. Sodium hydroxide has a strong alkaline, extremely corrosive, can be used as acid neutralizer, with masking agent, precipitating agent, precipitation masking agent, color development agent, saponification agent, peeling agent, detergent, etc., the use is very wide.

nature
Pure sodium hydroxide is a white solid, readily soluble in water, and its aqueous solution is astringent and slippery. Sodium hydroxide is easy to absorb water when exposed to air, and the surface is wet and gradually dissolved, which is called delixing. Its relative density is 2.130. Melting point 318.4℃. Boiling point 1390℃. There are two kinds of caustic soda on the market: solid caustic soda is white, block, flake, rod, granular, brittle; Pure liquid caustic soda is colorless transparent liquid. Solid caustic soda has strong hygroscopicity. Easy to dissolve in water, heat release when dissolved, the aqueous solution is alkaline, there is a slippery sense; Soluble in ethanol and glycerol; Insoluble in acetone and ether. Extremely corrosive, corrosive to fiber, skin, glass, ceramics and so on. React with aluminum and zinc, non-metallic boron and silicon to release hydrogen; Disproportionation with halogens such as chlorine, bromine and iodine; Neutralize with acids to form salt and water.

preparation
There are two methods of industrial production of caustic soda: causticization and electrolysis. Causticizing method is divided into soda ash causticizing method and trona causticizing method according to different raw materials. Electrolysis can be divided into membrane electrolysis and ion exchange membrane method.
Soda ash causticization method: soda ash and lime are made into soda ash solution by alkali, lime milk is made from ash, causticization reaction is carried out at 99 ~ 101℃, and the causticization solution is clarified, evaporated and concentrated to more than 40% to obtain liquid caustic soda. The concentrated liquid was further boiled and solidified to produce the finished solid caustic soda. The causticized mud is washed with water, which is used for alkali conversion.
Trona causticization method: trona is pulverized, dissolved (or alkaline halide), clarified and added to lime milk for causticization at 95 ~ 100 ° C, the causticization liquid is clarified, evaporated and concentrated to about 46% NaOH concentration, the clear liquid is cooled, and the salt is further enriched to produce solid caustic soda products. The causticized mud is washed with water, which is used to dissolve trona.
Diaphragm electrolysis method: The original salinized salt is added to soda ash, caustic soda, barium chloride fine preparation to remove impurities such as calcium, magnesium, sulfate ions, etc., and then sodium polyacrylate or causticized bran is added to the clarifying tank to accelerate precipitation, and hydrochloric acid is added to neutralize after sand filtration. The brine is preheated and sent for electrolysis, and the electrolyte is preheated, evaporated, salted and cooled to obtain liquid caustic soda, which is further enriched to obtain solid caustic soda. The salt mud wash water is used to melt the salt.
Ion exchange membrane method: The primary refined salt water is filtered through the micro-porous sintered carbon tube filter, and then the chelated ion exchange resin tower is used for secondary refining, so that the calcium and magnesium content in the salt water is reduced to below 0.002%. The secondary refined salt water is electrolyzed and chlorine gas is generated in the anode chamber. Na+ in the brine in the anode chamber enters the cathode chamber through the ionic membrane and produces sodium hydroxide with the OH- in the cathode chamber. H+ is discharged directly on the cathode to produce hydrogen. In the process of electrolysis, an appropriate amount of high-purity hydrochloric acid is added to the anode chamber to neutralize the returning OH-, and the required pure water should be added to the cathode chamber. The concentration of high-purity caustic soda generated in the cathode chamber is 30% ~ 32% (mass), which can be directly used as liquid caustic soda products, and can also be further condensed to produce solid caustic soda products.

security
Rinse with water or saline for 15 minutes, and then add 2% novocaine. In severe cases, be sent to hospital for treatment. The maximum allowable concentration of caustic soda dust in the air is 0.5 mg/m3. Operators must wear work clothes, masks, protective glasses, rubber gloves, rubber aprons, rubber boots and other labor protection supplies when working. Neutral and hydrophobic ointment should be applied to the skin. The production workshop should be well ventilated. Industrial solid caustic soda should be packed in iron drums or other closed containers. The wall thickness of the drums should be above 0.5 mm, and the pressure should be above 0.5 Pa. The lid of the drums must be sealed firmly. The net weight of each barrel is 200kg, and the caustic soda tablet is 25kg. There should be a clear "corrosive goods" sign on the package. When edible liquid caustic soda is shipped in a tank or tank, it must be cleaned after two uses. Food liquid caustic soda is not allowed to be transported in tank trucks or tanks or drums for carrying liquid caustic soda obtained by electrolytic method of mercury. Food liquid caustic soda or soda tablets are allowed to be transported in plastic drums or tanks that meet the requirements of food packaging standards. The words "food additive" and the sign "corrosive substance" should be clearly displayed on the package. Belongs to the first class inorganic alkaline corrosion articles, hazard code number: GB 8.2 class 82001. UN N0.1832; IMDG CODE 8225, 8226 pages, Class 8.2. It should be stored in a ventilated and dry warehouse or shed. Packaging containers should be complete and sealed. Shall not be stored and transported with inflammable materials and acids. Pay attention to moisture-proof and rainproof during transportation. If the packaging container is found to be corroded, broken, perforated, melted and watery, etc., the packaging should be replaced immediately or used early, and the damaged container can be repaired by tin welding. When fire, water, sand and various fire extinguishers can be put out, but firefighters should pay attention to the corrosion of caustic soda dissolved in water.

1. Application :

① Used for the production of paper making and cellulose pulp .

② Used for soap, synthetic detergent, synthetic fatty acid production and animal and vegetable oil refining.

③ Textile printing and dyeing industry used as cotton desizing agent, boiling agent and mercerizing agent.

④ Chemical industry for the production of borax, sodium cyanide, formic acid, oxalic acid, phenol and so on.

⑤ The petroleum industry is used to refine petroleum products, and used in oilfield drilling mud.

⑥ Also used in the production of alumina, metal zinc and metal copper surface treatment and glass, enamel, leather, dyes.