(2gv) A Holistic Approach for Inorganic Salt Recovery from Wastes Generated from Common Salt Harvesting Activities

Recovery of salt (NaCl) and marine chemicals from natural brines and saline effluents using various separation processes.

Common salt (sodium chloride) is an essential mineral with domestic and industrial applications. Salt is a basic raw material required for the production of multiple chemicals, chlor alkali and food industries being the major consumers. The world salt production has crossed 300 million MT per annum and about 30% of the salt comes from sea brine. India ranks third among the salt producing countries in the world after China and USA with an annual production of 30 million MT. Majority of salt production in India is based on the progressive solar evaporation of brine (sea brine, sub-soil brine or lake brine) and concentration of brine in specially designed solar pans. The major ions present in brines are Na⁺, Mg²⁺, K⁺, Ca²⁺, Cl^–, SO₄^2–, CO₃^2–, Br^–, with traces of other ions/elements. By virtue of the solubility products of the individual inorganic salts a series of salts crystallizes out during the progressive evaporation. A typical sequence is CaCO₃ à CaSO₄.2H₂O à NaCl à concentrated brine. The concentrated brine after common salt crystallization is called bittern and is a rich solution of various ions. Currently this bittern generated after salt harvesting activity is a by-product which is often considered as a waste stream.

This work aims to provide a holistic approach for utilizing the sea bittern generated by salt harvesting to recover a series of products including bromine, sodium sulphate, low-sodium salt, potassium chloride and magnesium chloride.