Sodium Hydroxide commonly known as Caustic Soda is a strong alkali compound, which reacts readily with various substances. Caustic Soda is highly corrosive in nature and is a by-product of Chlorine manufacturing process. It is available in various forms such as pellets, flakes, granular & solution form across industries. The commonly available forms are Caustic soda flakes, Caustic soda pearls & Liquid caustic soda.
Properties of Caustic Soda:
- White solid
- Highly soluble in water & dissolution is highyly exothermic.
- Low solubility in ethanol & methanol
- Insoluble in ether & other non-polar solvents.
- Strong base
- Readily absorbs water (hygroscopic) and carbon dioxide from the air
- Strong electrolyte
- Not volatile, but can rise easily in air as an aerosol
Manufacturing Process for Caustic Soda:
Production of caustic soda (sodium hydroxide, NaOH) is based on the electrolysis of brine. In this process, brine is electrolytically decomposed to elemental chlorine (in the anode compartment), and sodium hydroxide solution and elemental hydrogen (in the cathode compartment).
The overall reaction for the electrolytic production of caustic soda and chlorine is:
Chlor-alkali electrolyses process equations:
The electrolytic route to making caustic soda, by using sodium chloride as a raw material, is a co-product process.
Manufacturers use either of two electrolytic processes to produce caustic soda solution and chlorine. These processes are:
- Diaphragm cell
- Membrane cell
- Mercury cell
Caustic Soda Solid has various applications in different industries. Some of the main applications are:
Sodium hydroxide is a major raw material used Paper & pulp industry for pulping of wood. The white liquor solution used in the Kraft process to separate lignin from cellulose fibres has caustic soda as a key component. It also acts a bleaching agent in the later stages of the process by bleaching the brown pulp.
In textile industry; wax and oil needs to be removed from the fibre to make the fibre receptive to bleaching, dying, etc. Caustic soda is used in textiles to remove wax & oils. Caustic soda treatment provides tensile strength and lustre to the fabric.
Soap and detergents industry
In soap and detergent industry, caustic soda is used for saponification process of converting fats into soap. It is used in manufacturing anionic surfactants for detergent and cleaning products.
In Oil and Gas industry uses caustic soda in the exploration, production and processing of petroleum and natural gas, where it neutralizes acid gas such as hydrogen sulphide & carbon dioxide. Thus, it removes objectionable smells originating from hydrogen sulfide (H2S) and mercaptans.
In Alumina refineries, Caustic soda is used in Bayer’s process of aluminium extraction. Caustic soda dissolves bauxite ore; raw material for Aluminium production.
Water treatment industry
Sodium hydroxide is used in water treatment to raise the pH of water. Increased pH causes the water to become less corrosive to plumbing and thus the amount of lead, copper and other toxic metals that can dissolve into drinking water decreases significantly.
Caustic Soda is used in the production of renewable fuels, by being used for pH adjustment and formation of in situ sodium methylate in bioethanol and biodiesel processing.