Solar brine composition

Recovery from Brines. Natural lithium brines are predominately chloride brines varying widely in composition. The economical recovery of lithium from such sources depends not only on the lithium content but on the concentration of interfering ions, especially calcium and magnesium. If the magnesium content is low, its removal by lime precipitation is feasible. Location and avadabiHty of solar evaporation (qv) are also important factors. 

TABLE 6.3 Salinities and Compositions, in Percent by Weight of Dissolved Salts, for Some Major Brine Sources of Solar Salt... 

C at a depth of 900 m and 360°C at 2,100 m. At Cerro Prieto, geothermal power-production wells draw brines from depths of 780-1,450 m with temperatures of 250° to 344°C. The northern reservoir contains a concentrated brine with a very complex chemical composition, and is estimated to contain a total of 165 million tonnes of KCl. Plans have been made for further solar evaporation of the Cerro Prieto geothermal power plant exhaust brine to recover the potash. However, the project has not yet become operational. 

The first salt produced by solar evaporation, many centuries ago, would have had approximately the composition tabulated above. Its taste would have been very bitter. Technology began to advance when someone noticed that the taste deteriorated rapidly toward the end of the evaporation. By draining off the last small volume of brine and harvesting the salt already formed, the solution responsible for the bitterness, still referred to as bitterns, was isolated. Similarly, someone noticed at some point that the first material precipitated was not salt. By making a cut on the front end, transferring the brine after the onset of NaCl precipitation to another pond, the amount of gypsum in the product was also reduced. This simple technique is the essence of the methods used today. 

Figure 16.16 Typical composition of solar pond brine.

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