A COMPARISON OF THE EFFECTIVENESS OF ONE AND TWO STAGES, THE PRECIPITATION METHOD IN THE PURIFICATION PROCESS OF SALT SOLUTION

Sodium Chloride (NaCl) is a strategic commodity. In the chemical industry, salt is the primary raw material for the production of chlorine gas (Cl2), hydrochloric acid (HCl), sodium hydroxide (NaOH), sodium sulfate (Na2SO4), sodium carbonate (Na2CO3), and sodium bicarbonate (NaHCO3).1 Some types of salt suitable for use are analytical grade salt, pharmaceutical salt, miscellaneous salt, industrial salt, consumption salt, and salts for making salted fish-tanning skin.2,3 Analytical grade salt is high-purity with a 99.5 - 100.5% NaCl content and a low concentration of other compounds. The salt is widely used for laboratory purposes, such as chemical reagents, standard solutions, and microbiological media. Analytical grade salt specifications
refer to Sigma Aldrich, Merck, and Fisher Scientific standards. Meanwhile, pharmaceutical salt is used in
the pharmaceutical industry to manufacture cosmetics and solutions for injection. Table-1 shows NaCl, calcium, magnesium, sulfate, and water quality requirements for analytical grade and pharmaceutical salt.4,5 Generally, to increase salt quality, it is necessary to have the stages of the purification process to increase NaCl content and reduce impurities of ions such as SO4 2-, Mg2+, Ca2+, and K+ . Several studies have been investigated to improve the quality of salt using precipitation with NaOH, Na2CO3, and poly aluminium chloride6 , hydro extraction7,8, coagulation process 9-12, HDPE membrane 13, and greenhouse prism14, evaporation and purification with recrystallization and chemical methods by the addition of chemicals Ca(OH)2, NaOH, and Na2CO3 15, separation and purification from desulfurization wastewater of thermal power plantE3S16 but the results are only able to produce industrial and food-grade salt. Generally, analytical grade and pharmaceutical NaCl production require a purification process technology commonly carried out by precipitation and ion exchange methods.