Application du modèle de Pitzer à l’étude de l’évaporation solaire isotherme des saumures naturelles

The brine reserves of southern Tunisian chotts and sebkhats represent a source of mineral salts of a great interest, from which mineral salts can be recovered by isothermal solar evaporation. The evolution of density and ionic composition of the treated brine, during its isothermal evaporation, was studied. The experimental pathway of the evaporated brine was plotted on the oceanic quinary diagram Na$^{+}$ , K$^{+}$ , Mg$^{2+}$, Cl$^{-}$, SO$_4$$^{2-}$ // H$_2$O. In order to better understanding the observed chemical equilibria and, especially, to predict the precipitation sequences of mineral salts, during solar evaporation at 25°C, the theoretical pathway of the same studied brine was calculated using Pitzer’s ion interaction model. The experimental, the theoretical and the calculated pathways are not the same

Étude de l'évaporation d'une saumure naturelle. Corrélation conductivité-concentrations ioniques (Na+, K+, Mg2+, Cl-,SO24)

During evaporation natural brine crystallizes different salts. The limit between two steps is generally pointed using the density of the liquid phase in equilibrium with the crystallized salt. This method presents some disadvantages when used in the field especially when the pretreated brine is used to recover epsomite by refrigerating it. The aim of this work is to establish a correlation between the measured conductivity and the specific density of a considered brine and then with its ionic composition. The plotted parameters will be used to define the highest limit before extracting magnesium sulfate from the brine

Évaporation isotherme et isobare des saumures du sud tunisien suivie par la méthode DPAO

Evaporation is the most important process to recover salts from Tunisian natural brines. So it's essential to visualize the geometrical representations of the system involved in this case Na$^+$, K$^+$, Mg$^{2+}$/CI$^-$,SO$_4^{2-}$ - H$_2$O. Those representations allow us to navigate through the diagram and to draw crystallisation paths. Many techniques have been successfully tested over the last century such as the van't Hoff projection and the Janecke one, and were used to resolve the complexity of the multicomponent problem. The DPAO is a computer based visualization method proposed to enable a simulation of brine evaporation and to foresee the solid phases deposed during the process

Saharan lithium: Brine chemistry of chotts from eastern Algeria

Salt pan brines in desert areas are globally known to be rich sources of lithium. This study reports the results of a regional survey of brine chemistry in chotts (salt pans) conducted along a 550 km long valley in the northeast Algerian Sahara, one of the major desert areas on Earth. A dataset composed of 50 samples, including brine, river, and aquifer, is integrated and discussed in order to study the characteristics of Sahara brines. Brines contain up to 66 mg L−1 of lithium, salinities up to ~400 g L−1, and magnesium concentrations ~690 times greater than that of lithium. The primary source of major ions would occurr by dissolution of ancient evaporites of the substrate by aquifer waters. Near surface lithium concentration of brines in chotts across the study area and in the aquifer Complexe Terminal defines a pattern of increasing values to the north, where maximum values coincide with chotts (Melghir and Merouane) having the largest sizes (up to 1,840 km2) and placed at the lowest altitudes (36 m below sea level). This pattern coincides with the northwards plunging structured substrate. Lithium grades increase consistently with salinity during the concentration through evaporation. However, lithium continues to concentrate beyond evolved brines whether due to the precipitation of lithium-free salts leading to lithium increases in residual brine, and/or by unknown processes supplying additional lithium. Discussed aspects are expected to drive an increasing interest on chotts, which would reveal in the future, as a stimulating opportunity for Algeria and the Saharan region.Fil: Zatout, Merzouk. University Kasdi Merbah - Ouargla. ; ArgeliaFil: López Steinmetz, Romina Lucrecia. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Hacini, Messaoud. University Kasdi Merbah - Ouargla.; ArgeliaFil: Fong, Shao Bing. University of Melbourne; AustraliaFil: M'nif, Adel. University Of Carthage; TúnezFil: Hamzaoui, A. H.. University Of Carthage; TúnezFil: López Steinmetz, Lorena Cecilia. Universidad Nacional de Córdoba. Instituto de Investigaciones Psicológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Psicológicas; Argentin