Progressive evaporation of brine of sebkha Mchiguig, central Tunisia: a geo-economical comparative study of salt and brine

Abstract

This work is meant to study the formation of salt through a progressive evaporation of water of sebkha Mchiguig. The precipitated salt in the case of sebkha Mchiguig is variable along the progressive evaporation. Weights of salt before each phase of precipitation indicate a heterogeneous evaporation process cumulating at 394 g L−1. With an increasing evaporation of Mchiguig brine, the number of precipitated mineral species increased. The cumulative number of species along the evaporation process reaches 12: Halite (NaCl) (81–96%), epsomite (MgSO4·7H2O) (7–14%), magnesite (MgCO3) (1–3%), polyhalite K2Ca2Mg(SO4)4, 2H2O (2–5%), the ikaite CaCO3.6(H2O) (2.1%), langbeinite K2Mg2(SO4)3 (0.4%), celestite SrSO4 (2.1%), sodium ozonide (NaO3) (1.5%), allenite MgSO3(H2O)6 (0.8%) hydromagnesite Mg5(CO3)4(OH)2·4H2O (0.2%) and magnesium chloride MgCl2 (0.3%). Also, the thermodynamic theoretical modeling of the Mchiguig brine shows convergence with geochemical and mineralogical experimental data. The saline system of Mchiguig represents a geo-economic interest by its big quantity of halite and varieties of accessory minerals. However, a special care should be given to environmental and hydrodynamic repercussions of the overuse of water budget.