Caustic Soda

About Caustic Soda

• It is also known as sodium hydroxide (NaOH).
• Properties: It is a corrosive white crystalline solid. 
  • It is highly alkaline and readily dissolves in water, releasing hydroxide ions (OH⁻) and resulting in a pH of approximately 14.
• Production process: Commercial caustic soda is mainly produced through the chlor-alkali process, which involves the electrolysis of brine (sodium chloride solution).
  • It involves Membrane cell technology, which is the modern, energy-efficient standard for producing caustic soda and chlorine gas through the electrolysis of brine (saltwater).
• Uses: It is widely used in the manufacture of soaps, rayon, paper, explosives, dyes, and petroleum products.
  • It is also used in cotton processing, laundering and bleaching, metal cleaning, electroplating, oxide coating, electrolytic extraction, and is a common ingredient in commercial drain and oven cleaners.
• Production in India: The majority of its domestic production (non-captive) is in the Western region of the country, mainly in Gujarat, Maharashtra and Rajasthan.
  • India has about 32 to 37 caustic soda plants, with an annual production of more than five million metric tonnes.

About the New Environmental Standards

• Under new environmental standards , caustic soda plants operating with membrane cell technology are required to undergo a fish-survival bioassay test to evaluate the toxicity of their wastewater.
• The regulations mandate that at least 90% of fish must survive after being exposed to 100% wastewater for 96 hours under laboratory conditions.
• This test is intended to determine whether the treated effluent is harmful to aquatic life, beyond merely complying with individual chemical discharge limits.
• In addition, the standards prescribe specific limits for pH, chloride concentration, suspended solids, dissolved solids, water consumption, and wastewater generation.