Brine purification magnesium

Brine purification. The system sodium bicarbonate-sodium chloride-magnesium carbonate-water. Ind. Eng. Chem., 26 1099-1104. 

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. 

The first step in brine purification is chemical treatment to remove certain impurities. The elements of hardness (calcium and magnesium) must be removed, along with iron and heavy metals. This is done by precipitation, adding a source of carbonate ion to remove calcium and a source of hydroxide ion to remove the other metals. Sulfate ion also can be removed by precipitation, using either calcium or barium ion. Precipitation processes cannot usefully be considered in isolation. The nature of the solids formed in this way determines how they will behave in the later processes that are designed for their physical removal. The subsections that follow therefore describe in a general way the flow behavior and settling rates of precipitated particles. Later sections of the chapter cover the details of sedimentation and filtration of the solids. 

Brine Purification. In mercury cells, traces of heavy metals in the brine give rise to dangerous operating conditions (see p. 32), as does the presence of magnesium and to a lesser extent calcium (521. In membrane cells, divalent ions such as Ca or Mg are harmful to the membrane. The circulating brine must be rigorously purified to avoid any buildup of these substances to undesirable levels [7]. Calcium is usually precipitated as the carbonate with sodium carbonate magnesium and iron, as hydroxides with sodium hydroxide and sulfate, as barium sulfate. 

Upon cooling to room temperature, a gray precipitate forms and the reaction is quenched with 220 mL of saturated, aqueous ammonium chloride. The resulting mixture is poured into a 1-L separatory funnel and extracted with 220 mL of diethyl ether. The organic fraction is washed two times with 100 mL of water, and once with 100 mL of brine, dried over magnesium sulfate, filtered, and concentrated under reduced pressure to provide 44.1 g of crude product as a pale yellow oil. Purification of this material by bulb-to-bulb distillation (140-145°C, 0.5 mm) (Note 11) into a chilled (-78°C) receiving flask yields 41.0 g (92%) of 2 as a clear, colorless oil (Note 12). 

Novel ion-exchange technology has recently been developed for purification of brine. Different resins have been developed for removal of sulphate impurities as well as calcium and magnesium hardness. The process is very simple and since only water is consumed to regenerate the ion-exchange resins, the operating costs are extremely low. The equipment, which is similar to that currently widely utilised for purification of waste acid, is very compact. It is expected that commercial-scale systems of both types will be installed later in 2000. 

The mixture of alcohols is placed in a 1000-mL round-bottomed flask, dissolved in 300 mL of ether, and cooled to 0°C. To this solution is added via an addition funnel over a 30-min period a mixture of sodium dichromate dihydrate (27.5 g, 0.092 mol), 100 mL of water, and 10.2 mL of coned sulfuric acid. The mixture is stirred at 0°C for 1 hr, warmed to room temperature where stirring is maintained overnight, diluted with 200 mL of water, and poured into a separatory funnel. The layers are separated and the aqueous phase is extracted with ether (3 x 200 mL). The combined organic layers are washed with saturated sodium bicarbonate solution (200 mL) and brine (200 mL), dried over anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to give 16.8-17.8 g (61-65%) of verbenone (Note 7). Final purification is achieved by distillation of the oil through a 5-in Vigreux column at reduced pressure (dry ice-acetone cooled receiver) 13.1 g (47%), bp 108-110°C (5 mm) (Note 8). 

Methyl magnesium chloride (3.0 Molar solution in THF, 790 mmol) was added dropwise over 30 min to the CeCI3 slurry at 0°C. After stirring 2 hours, the mixture was cooled to -5°C and a toluene (600 mL) solution of the ethyl 2-(3(S)-(3-(2-(7-chloro-2-quinolinyl)ethenyl)phenyl)-3-hydroxy-propyl)benzoate (152 mmol) was added dropwise over 1 hour. The reaction mixture was stirred another hour before the addition of 2 M HOAc (600 mL) and toluene (600 mL). The organic layer was washed with saturated aq. NaHC03 and with brine. Concentration in vacuo and purification of the residue by flash chromatography (30% EtOAc in toluene) gave 63.48 g (91%) of the 2-(2-(3(S)-(3-(2-(7-chloro-2-quinolinyl)ethenyl)phenyl)-3-hydroxypropyl)phenyl)-2-propanol. 

To a cold solution of N-Boc-L-serine (32.4 g, 0.16 mol. Note 5) in dimethylformamide (150 ml) is added solid potassium carbonate (24.3 g, 0.176 mol). After stirring for 10 min in an ice-water bath, methyl iodide (20.0 mL, 46.3 g, 0.32 mol -Caution Methyl iodide is toxic and a suspected carcinogen that should be handled in a well-ventilated fume hood.) is added to the white suspension and stirring continued at 0°C for 30 min whereupon the mixture solidifies. The reaction is warmed to room temperature and stirred for an additional hour or so at which point TLC analysis indicates complete formation of the methyl ester (Note 6). The reaction mixture is filtered by suction and the filtrate partitioned between ethyl acetate (300 mL) and water (300 mL). The organic phase is washed with brine (2 x 300 mL), dried with magnesium sulfate, filtered and concentrated to give 29.8 g (86% yield) of N-Boc-L-serine methyl ester as a pale amber oil which is used without further purification (Notes 7 and 8).2... 

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