Latin American applied research
versión impresa ISSN 0327-0793
Brines are high concentrated aqueous solutions frequently used as raw materials for the recovery of several salts, which are industrially use-ful and necessary in some agricultural applications. This paper deals with a six-stage process for the re covery of magnesium chloride hexahydrate (bischofite) from Sebkha El Melah natural brine (South of Tunisia). It is based on successive evaporation sequences to precipitate firstly sodium chloride and then potassium-magnesium double salts. After that, the mother liquor is cooled to remove magnesium sulphate heptahydrate (epsomite). This step is essential before precipitating the potassiummagnesium double salt KCl.MgCl2.6H2O (carnallite). At the end of this step the recovered solution still contains sulphate ions which may disturb magnesium chloride extraction. In order to overcome this difficulty, a sulphate removal step has been advocated using calcium chloride solution. The treated solution becomes sulphate ion free and thus suitable to be used for bischofite preparation. The investigated procedure makes available the production of a magnesium chloride salt (purity upper than 90%) and various by-products, such as: halite (NaCl), gypsum (CaSO4.2H2O) and epsomite (MgSO4.7H2O).
Palabras llave : Brine; Isotherm Evaporation; Bischofite Recovery; Process.