Brine precipitation

A brine precipitation plant works on the same principles as a seawater magnesia plant. However, there are some differences in operations. As subsurface brine sources have a higher concentration of magnesium salts than 

---

Injected alkali reaction with formation brine (precipitation) and minerals (dissolution and ion exchange)... 

Mexico Petioles, S.A. de C.V. Brine precipitation Approx. 40,000 tonnes caustic, fused, hydroxide, and dead bum... 

Figure 3.2 Generalized flow diagram of a seawater/brine precipitation process.

Chains located at the back-end help to break up and deagglomerate a wet filter cake or sludge. This arrangement is typically used when calcining seawater or brine precipitated magnesia. 

Synthetic magnesium hydroxide slurry is produced using either seawater- or brine-precipitated magnesium hydroxide filter cake that has the desired solids content of the finished slurry. To produce pumpable slurry, the... 

Sometimes, flocculation of particles is useful by increasing the rate of sedimentation. With typical brine precipitates, the flocculants most frequently used are acrylic... 

Table 24. Isotopic composition of lead in brines, precipitate from brines, and vein and stratiform ores possibly related to brines...

A mixture of l-(r-Boc)indol-2-yl-tri- -butylstannanc (1.2 mmol) and 4-bromo-benzonitrile (1.0 mmol) and Pd(PPh3)2C , (0.02 mmol) in dry dioxane (5 ml) was heated at I00°C overnight under nitrogen. The reaction mixture was cooled, diluted with EtOAc and stirred for 15 min with 15% aq. KF. The precipitate was removed by filtration and washed with EtOAc. The EtOAc layer was separated, washed with brine, dried (Na2S04) and concentrated. The residue was purified by chromatography on silica. The yield was 66%. 

Brine Preparation. Sodium chloride solutions are occasionally available naturally but they are more often obtained by solution mining of salt deposits. Raw, near-saturated brines containing low concentrations of impurities such as magnesium and calcium salts, are purified to prevent scaling of processing equipment and contamination of the product. Some brines also contain significant amounts of sulfates (see Chemicals FROMBRINe). Brine is usually purified by a lime—soda treatment where the magnesium is precipitated with milk of lime (Ca(OH)2) and the calcium precipitated with soda ash. After separation from the precipitated impurities, the brine is sent to the ammonia absorbers. 

Recovery of Ammonia. The filter Hquor contains unreacted sodium chloride and substantially all the ammonia with which the brine was originally saturated. The ammonia may be fixed or free. Fixed ammonia (ammonium chloride [12125-02-97]) corresponds stoichiometrically to the precipitated sodium bicarbonate. Free ammonia includes salts such as ammonium hydroxide, bicarbonate, and carbonate, and the several possible carbon—ammonia compounds that decompose at moderate temperatures. A sulfide solution may be added to the filter Hquor for corrosion protection. The sulfide is distilled for eventual absorption by the brine in the absorber. As the filter Hquor enters the distiller, it is preheated by indirect contact with departing gases. The warmed Hquor enters the main coke, tile, or bubble cap-fiUed sections of the distiller where heat decomposes the free ammonium compounds and steam strips the ammonia and carbon dioxide from the solution. 

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. 

The brine clean-up consists of skimming and settling steps to free the solution from oil, clays, and other impurities. Sulfuric acid is then added until a pH of <2.5 is reached ensuring iodine Hberation by oxidation, precipitation of the soluble barium contained in the brine, and recovery of the remaining iodine. 

Part of the continuously recirculated solution is bled off and sent to the iodine finishing process. Iodine finishing consists of contacting this bleed of concentrated acidic iodide solution with gaseous chlorine, through which iodine is formed by oxidation and precipitated. After iodine precipitation, the resulting acidic mother Hquor, saturated with free iodine, is pumped back to acidify the clarified brine and to recover the remaining iodine. 

Uranium ores are leached with dilute sulfuric acid or an alkaline carbonate [3812-32-6] solution. Hexavalent uranium forms anionic complexes, such as uranyl sulfate [56959-61-6], U02(S0 3, which are more selectively adsorbed by strong base anion exchangers than are other anions in the leach Hquors. Sulfate complexes are eluted with an acidified NaCl or ammonium nitrate [6484-52-2], NH NO, solution. Carbonate complexes are eluted with a neutral brine solution. Uranium is precipitated from the eluent and shipped to other locations for enrichment. Columnar recovery systems were popular in South Africa and Canada. Continuous resin-in-pulp (RIP) systems gained popularity in the United States since they eliminated a difficult and cosdy ore particle/leach hquor separation step. 

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. 

Preparation and Manufacture. Magnesium chloride can be produced in large quantities from (/) camalhte or the end brines of the potash industry (see Potassium compounds) (2) magnesium hydroxide precipitated from seawater (7) by chlorination of magnesium oxide from various sources in the presence of carbon or carbonaceous materials and (4) as a by-product in the manufacture of titanium (see Titaniumand titanium alloys). 

---