EXTRACTIVE PROCESS FOR PREPARING HIGH PURITY MAGNESIUM CHLORIDE HEXAHYDRATE

This paper reports a method for the preparation of magnesium chloride hexahydrate (bischofite) from Sebkha el Melah of Zarzis Tunisian natural brine. It is a five-stage process based on crystallization by isothermal evaporation and chemical precipitation. The first two steps were dedicated to the crystallization of sodium chloride and potassium-magnesium double salts, respectively. Then, the resulting liquor was desulfated using calcium chloride solution. After that, another isothermal evaporation stage was implemented in order to eliminate potassium ions in the form of carnallite, KCl center dot MgCl2 center dot 6H(2)O. At the end of this step, the recovered solution, primarily composed of magnesium and chloride ions, was treated by dioxan in order to precipitate magnesium chloride as MgCl2 center dot 6H(2)O center dot C4H8O2. This compound dried at constant temperature of 100 degrees C gave good quality magnesium chloride hexahydrate. Besides this salt, the various by-products obtained from the different treatment stages are also useful.