Brines, chloride-rich

Fig. 7. Temperature—pH limits for crevice corrosion of titanium alloys in naturally aerated sodium chloride-rich brines. The shaded areas indicate regions...

Steinmann, M. Stille, P. 1998. Strongly fractionated REE patterns in salts and their implications for REE migration in chloride-rich brines at elevated temperatures and pressures. Comptes Rendus Academie des Sciences, Paris, II, 327, 173-180. 

Seawater is evaporated by concentrating the seawater in the first evaporation pool transporting to the next evaporation zone, in which calcium sulfate precipitates out and finally crystallizing sodium chloride in a further evaporation zone. The residual brine is rich in potassium and magnesium salts. The salt obtained is too impure to be used in electrolysis. Washing in special units is sufficient to increase the sodium chloride content to > 99%. I m- of seawater yields ca. 23 kg of sodium chloride. 

Brines. Some data are available on the direct measurement of lead isotope ratios in chloride-rich natural brines (Table 24). These brines contain unusually large heavy metal contents and are discussed in the context of an ore fluid in the previous section. 

Akaganeite, P-FeOOH, is named after the Akagane mine in Japan where it was first discovered (Mackay, 1962). It occurs rarely in nature and is found mainly in Cl-rich environments such as hot brines and in rust in marine environments. Unlike the other FeOOH polymorphs, it has a structure based on body centered cubic packing of anions (bcp) (hollandite structure) and contains a low level of either chloride or fluoride ions. It has a brown to bright yellow colour. 

In the ion-exchange method, brine solution is passed through an anion-exchange resin. Iodide (and polyiodide) anions from the solution adsorb onto the resin from which they are desorbed by treatment with caustic soda solution. The resin is treated with sodium chloride solution to regenerate its activity for reuse. The iodide solution (also rich in iodate, IO3 ions) is acidified with sulfuric acid. The acid solution is oxidized to precipitate out iodine. Iodine is purified by sublimation. 

In most commercial processes, the compound is either derived from the sea water or from the natural brines, both of which are rich sources of magnesium chloride. In the sea water process, the water is treated with lime or calcined dolomite (dolime), CaO MgO or caustic soda to precipitate magnesium hydroxide. The latter is then neutralized with hydrochloric acid. Excess calcium is separated by treatment with sulfuric acid to yield insoluble calcium sulfate. When produced from underground brine, brine is first filtered to remove insoluble materials. The filtrate is then partially evaporated by solar radiation to enhance the concentration of MgCb. Sodium chloride and other salts in the brine concentrate are removed by fractional crystallization. 

In the latter half of the nineteenth centuiy the United States was dependent on the vast Stassfurt deposits of Germany for the potassium compounds needed as fertilizers. In 1911 Congress appropriated funds for a search for domestic minerals, salts, brines, and seaweeds suitable for potash production (67). The complex brines of Searles Lake, California, a rich source of potassium chloride, have been worked up scientifically on the basis of phase-rule studies with outstanding success. Oil drillers exploring the Permian Basin for oil became aware of the possibility of discovering potash deposits through chemical analysis of the cores of saline strata. A rich bed of sylvinite, a natural mixture of sylvite (potassium chloride) and halite (sodium chloride), was found at Carlsbad, New Mexico. At the potash plane near Wendover, Utah, the raw material, a brine, is worked up by solar evaporation (67). 

Figure 8.13. Plot of expected stability field for ordered dolomite as a function of temperature, and Ca2+ Mg2+ ion ratio in 1 m and 2 m chloride brines. At the top is a histogram of Ca2+ Mg2+ ion ratios of groundwaters in contact with a variety of sedimentary rocks, showing that at temperatures above 60-70°C many Ca-rich groundwaters could be dolomitizing fluids. (After Hardie, 1987.)...

These features are likely to encourage further development of vacuum or solar evaporation salt recovery operations to work these brines in proximity to the desalination plants. In this way, various salts may be more profitably recovered from these artificially enriched seawaters for reasons similar to the present incentives to use the rich natural brine sources for sodium chloride production (Table 6.3). Similar energy savings should be obtained. 

About 10% of the raw rock, comprising silica and the like, does not dissolve. However, this material is readily removed by settling the dilute slurry in a thickener, sometimes aided by coagulants (Fig. 6.6). The clarified solution from the thickeners is then extracted with a C4, C5 alcohol mixture or trialk-ylphosphate in a series of three or more mixer settlers producing a solvent phase rich in phosphoric acid, and a raffinate of calcium chloride brine freed of phosphate. Presence of the calcium chloride salt in the aqueous phase undoubtedly assists in driving the phosphoric acid transfer to the organic phase by making the aqueous phase more polar. 

That situation has changed. Today the most important source of sodium carbonate is natural minerals, such as thermonatrite (sodium carbonate monohydrate Na2C03-H20) or natron (or natrite sodium carbonate decahydrate Na2C03-ioH20). These minerals are obtained from rocky deposits or from brines that are rich in the compound. Brine is water that is saturated with salts, such as sodium chloride, potassium chloride, and sodium carbonate. It is similar to, but saltier than, seawater. 

A meteorite that landed in Monahans, Texas, in 1998 was cut open and water was found in it it was the first time that scientists have detected water in a meteorite, an essential ingredient for life of primordial origin (Zolensky et al. 1999). The fluids are dominantly sodium chloride-potassium chloride brines, but they also eontain divalent cations such as iron, magnesium, or calcium. The Monahans belongs to a class of meteorites known as ordinary chondrites, which astronomers have believed are fragments of asteroids that contain little or no water. One explanation for the water in this meteorite is that its parent asteroid acquired it after the rock formed. A water-rich, icy projectile, such as a comet, could have plowed into the newborn asteroid and spilled some of its water. Alternatively, the water might have been incorporated into the asteroid as it coalesced (Kargel 1992, Schmitt et al. 2007)). 

Table 4.6 summarizes the major lithium-carbonate producers and suppliers. Close examination indicates that SQM s lithium-rich brine operation is now the largest lithium-carbonate operation in the world. In addition to lithium carbonate, the Minsal facility has the capacity to produce annually 300,000 tonnes of potash, which it uses at its local fertilizer operation, 250,000 tonnes of potassium chloride, and 16,000 tonnes of boric acid and, to a lesser extent, iodine. 

It should be noted that titanium aUo5 are generally not susceptible to sulfide stress cracking (SSC) in HjS-rich, sulfides, and/or sulfur containing environments (e.g., sour gas/oil well fluids). This inherent SSC resistance stems from the fact that formation of titanium sulfide corrosion products is not thermodynamically favored, such that stability of titanium s protective oxide surface film wiU prevail even at higher service temperatures. In these hot sour brine service environments, resistance to chloride-induced SCC is a more relevemt issue for titanium alloys. 

Magnesium-rich brine is also used for the production of magnesium oxide. The process involves the decomposition of magnesium chloride (MgCl2) present in brine in the temperature range of 600°C-800°C. The decomposition takes place by reaction with steam, and the reaction is represented in Equation 12.6. The Mg(OH)2 produced after the decomposition reaction is calcined as earlier to get MgO. 

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