Salts and Brines

The salt used by most chlor-alkaU producers falls into the categories of rock salt and solar salt. The former is recovered from underground deposits by conventional mining and by solution mining, in which water or weak brine is pumped into an underground deposit to dissolve the salt. Solar salt results when saline water evaporates past the point of saturation in open ponds. Rock salt is the common supply in Europe and North America. Imported solar salt is the predominant supply in Japan and in many other parts of the world. There are other somces that are relatively minor in the industry as a whole but locally quite important. Saudi Arabia, for example, uses salt dredged from near-surface deposits found in low-lying areas. 

Potassium chloride ores usually are mixed salts, and so a certain amount of refining is often a part of the KCl extraction process. As a result, the material supplied to the chlor-alkali industry usually is of higher quality than the raw NaCl. Other grades of NaCl, however, are available that have also been treated to a higher purity before sale. 

With this wide variety of sources, one would expect to find great variations in the type and abundance of impurities in salt. Still, there are a number of useful generalizations. Table 7.6 shows that calcium, magnesium, and sulfate ions are the other major components of seawater and therefore the major impurities in most salts [63], and the removal or eontrol of these constituents is a primary objective of the brine purification process. The most widespread impurity in NaCl deposits is CaS04. Magnesium compounds, and to a lesser extent iron compounds, also are present in most natural salts. Oxides of silicon and aluminum are also found, as well as traces of other metals and sometimes anions such as iodide. The importance of these impurities depends greatly on the type of cell in use, and the methods used for purification of brine reflect all the above factors. 

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Aq, Aqueous C, cementing Cb, clay based D, drilling fluids FF, fracturing fluids HP, high pressure application HT, high-temperature application LT, low temperature Ob, oil based S, seawater mud SB, salt and brine tolerant. 

Spencer R. J., Lowenstein T. K., Casas E., and Pengxi Z. (1990) Origin of potash salts and brines in the Qaidam Basin, China. In Fluid—Mineral Interactions A Tribute to H. P. Eugster (eds. R. J. Spencer and I.-M. Chou). Geochemical Society, San Antonio, pp. 395-408. 

Other features of Wright Valley that have attracted attention are Lake Vanda and the associated ponds (Don Juan and Canopus), the origin of soil salts and brines, the Onyx River and related meltwater streams, the invasion of seawater into the valley, and the plants and animals that inhabit the soil and lakes of Wright VaUey (Tedrow andUgolini 1963). 

Effect on Membrane Iodine is sometimes present as an impurity in the raw salt and brine as iodide or iodate. It can precipitate as insoluble sodium paiaperiodate near the membrane cathode layer, reducing the current efficiency. 

Certain brines have excellent settling characteristics when treated. These include many of those produced from US Gulf Coast rock salt and brine wells. The problem of treat tank design becomes much simpler, and single-tank systems have been used effectively. 

Mayhew, E. J., and Heylmun, E. B. (1966). Complex Salts and Brines of the Paradox Basin. Second Symp. on Salt 1, 221-235. 

Spencer, R., Lowenstein, T. K., Casas, E., and Zhang, P. (1991). Origin of Potash Salts and Brine in the Qaidam Basin, China. Spec. Publ., Geochem. Soc. 2, 395-408 Fluid-Miner. Interact.. 

The reaction is initiated with nickel carbonyl. The feeds are adjusted to give the bulk of the carbonyl from carbon monoxide. The reaction takes place continuously in an agitated reactor with a Hquid recirculation loop. The reaction is mn at about atmospheric pressure and at about 40°C with an acetylene carbon monoxide mole ratio of 1.1 1 in the presence of 20% excess alcohol. The reactor effluent is washed with nickel chloride brine to remove excess alcohol and nickel salts and the brine—alcohol mixture is stripped to recover alcohol for recycle. The stripped brine is again used as extractant, but with a bleed stream returned to the nickel carbonyl conversion unit. The neutralized cmde monomer is purified by a series of continuous, low pressure distillations. 

Magnesium sulfate heptahydrate may be prepared by neutralization of sulfuric acid with magnesium carbonate or oxide, or it can be obtained directly from natural sources. It occurs abundantly as a double salt and can also be obtained from the magnesium salts that occur in brines used for the extraction of bromine (qv). The brine is treated with calcium hydroxide to precipitate magnesium hydroxide. Sulfur dioxide and air are passed through the suspension to yield magnesium sulfate (see Chemicals frombrine). Magnesium sulfate is a saline cathartic. 

Secondary coolants frequently are called brines because such fluids originally were mixtures of salts and water. Common refrigeration brines are water solutions of calcium chloride or sodium chloride. These brines must be inhibited against corrosion. 

Organic cross-linkers, which include glyoxal (48) and formaldehyde (qv), have also been used. Use of hypohaUte salts (49) and epichlorohydrin (50) promotes gel stabiUty. Phenol—formaldehyde cross-linking systems have been used to produce stable acrylamide copolymer gels at temperatures above 75°C and brine hardness levels above 2000 ppm (51). 

Sales of salt for regenerating ion-exchange water softeners have grown steadily in the United States, particularly in terms of revenues. The U.S. salt industry is mature and sales are not likely to increase rapidly. The dry salt industry in the United States and Canada has undergone consoHdation during the 1990s. The number of producers has continued to decline as the major salt producers have acquired smaller operations. Table 6 shows the total amount, including salt in brine, of salt sold or used in the United States for the period 1990—1994. The amount of salt sold or used in the United States in 1994 by product type is (9) ... 

Statistical data on dry salt sales are available through 1994 (9). Dry salt includes salt produced as crystalline sodium chloride, but excludes salt in brine produced for production of chlor—alkah products and other chemicals. Table 7 gives United States dry salt sales for the period 1990—1994. 

Salt preserves foods by providing a hostile environment for certain microorganisms. Within foods, salt brine dehydrates bacterial cells, alters osmotic pressure, and inhibits bacterial growth and subsequent spoilage. Dry salt and salt brine are used in several types of curing processes. Pickles are preserved in strong brine before final processing. 

In 1981, seven faciUties extracted minerals from Great Salt Lake brine, but flooding in 1983 and 1984 reduced the number to five. By 1992, four companies were operating. AH Great Salt Lake mineral extracting faciUties have solar ponds as the first stage in processing minerals from brine. 

Occurrence. Numerous brines contain lithium in minor concentrations. Commercially valuable natural brines are located at Silver Peak, Nevada (400 ppm) (40,41), and at Seades Lake, California (50 ppm) (42,43). Great Salt Lake brine contains 40 ppm and is a source not yet exploited. Seawater contains less than 0.2 ppm. Lithium production started at Silver Peak in the 1970s. The concentration of lithium in the brine is diminishing, and now the principal production occurs from brine in the Salar de Atacama, Chile. 

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