Magnesium chloride, electrolysis molten

Oyster shells or other seashells are calcined in a kiln to produce calcium oxide, which when added to seawater precipitates magnesium ion as magnesium hydroxide.This is neutralized with hydrochloric acid to give magnesium chloride. Electrolysis of molten MgClj yields magnesium metal and chlorine. Hydrochloric acid can be recovered by burning the chlorine with natural gas. 

Russian Process Technology. Magnesium production ia the former Soviet Union is apparently done via molten chloride electrolysis (29,30). The basic process uses camaOite [1318-27-0], MgCl2 KCl 6H20, either from natural deposits or as a by-product of processiag natural salt deposits, as its... 

Calculate the mass of magnesium that can he plated onto the cathode hy the electrolysis of molten magnesium chloride, using a current of 3.65 A for 55.0 min. 

FIGURE 12.18 A schematic diagram of the electrolytic cell used in the Dow process for magnesium. The electrolyte is molten magnesium chloride. As the current generated by the external source passes through the cell, reduction occurs at the cathode and oxidation at the anode. The products of the electrolysis are magnesium metal and chlorine gas. 

Magnesium metal is produced by the electrolysis of molten magnesium chloride using inert electrodes. 

Extracting magnesium from sea water is an efficient and economical process. Sea water is mixed with lime, CaO, from oyster shells to form insoluble magnesium hydroxide, Mg(0H)2, which can be easily filtered out. Hydrochloric acid is added to the solid to form magnesium chloride. The electrolysis of molten magnesium chloride will produce pure magnesium metal. 

The final step in the production of magnesium from seawater is the electrolysis of molten magnesium chloride, in which the overall reaction is... 

After the water is evaporated, the solid magnesium chloride is melted (m.p. 708°C) in a large steel electrolysis cell that holds as much as 10 tons of the molten salt. The steel in the cell acts as the cathode during electrolysis, with graphite anodes suspended from the top. The cell reaction is... 

After the water is evaporated, the solid magnesium chloride is melted in a steel cell. The molten magnesium chloride contains both Mg and Cl ions. In a process called electrolysis, an electric current is passed through the cell to reduce the Mg ions and oxidize the Ch ions. The half-reactions are... 

If the cost of electricity to produce magnesium by the electrolysis of molten magnesium chloride is 155 per ton of metal, what is the cost (in dollars) of the electricity necessary to produce (a) 10.0 tons of aluminum, (b) 30.0 tons of sodium, (c) 50.0 tons of calcium ... 

Davy electrolysed fused hydroxides of potassium and sodium in 1807, and in this way he discovered the metals potassium and sodium. A number of important metals are still produced by a similar route, the electrolysis of fused salts, including sodium (Na), magnesium (Mg), calcium (Ca) and aluminium (Al). Sodium, magnesium and calcium are all produced via electrolysis of the molten chloride. Taking molten sodium chloride (NaCl), as an example, the reactions are as follows. 

Exotic metals such as titanium and zirconium are produced from their respective chlorides, which are formed by reacting chlorine with the oxides. Thus, metallic titanium is produced by reacting TiCLj with molten sodium or magnesium, while metallic zirconium is made by reaction of ZrCU with magnesium. Molten salt electrolysis of magnesium chloride generates magnesium metal and chlorine, and fused salt electrolysis of sodium chloride and calcium chloride mixtures produces metallic sodium. 

Worldwide, 94% of the chlorine is made by the electrolysis of brine. Sodium hydroxide and hydrogen are prodnced as by-products. A few plants produce potassium hydroxide as well as, or instead of, sodinm hydroxide by the electrolysis of potassium chloride solutions. Abont 3% of the chlorine is made by other processes. These include electrolysis of hydrochloric acid electrolysis of molten sodinm or magnesium chloride, which, respectively, produce sodium or magnesium metal as well as chlorine " nitric acid oxidation of potassinm chloride to make nitrosyl chloride, which is further oxidized by oxygen to make potassium nitrate, and the oxidation of hydrochloric acid directly with oxygen or air using a catalyst, or indirectly throngh the formation and snbsequent oxidation of metal chlorides. ... 

Preparation of pure lithium-metal traps and ingots (molten lithium chloride electrolysis). Even if in some older processes the metal was prepared by direct metallothermic reduction of the lithium oxide with magnesium or aluminum, today lithium metal is essentially obtained directly by molten-salt electrolysis of LiCl-KCl according to a process... 

The Aluminum Company of America (known as Alcoa since 1999) was foimded in 1909 and became a msgor producer of aluminum by the HaU-Heroult process. Canada-based company Rio Tinto Alcan and Norvray-based Norsk Hydro are also msgor producers of aluminum. Msgnesium was first made commercially in Germany by I. G. Farben in the 1890 s, and later in the United States by Dow Chemical. In both instances, electrolysis of molten magnesium chloride was used to produce the magnesium. 

Electrowinning of Other Metals. Magnesium, like aluminum, is a low-density metal and is also manufactured by electrolysis. The electrolysis of molten magnesium chloride (in the presence of other metal chlorides to lower the melting point) yields mj ne-sium at the cathode. The scale of ms nesium production is not as large as that of aluminum, amounting to several hundred thousand metric tons per year. Ms -nesium is used in aircraft alloys, flares, and chemical syntheses. 

How long wiU it take to produce 1.00 X ICP kg of magnesium metal by the electrolysis of molten magnesium chloride using a current of 5.00 X 10 A ... 

Electrolysis of molten NaCl is also carried out on a large scale, yielding sodium metal at the cathode rather than hydrogen. Still other processes involve the electrolysis of fused magnesium chloride (MgCU) or the oxidation of hydrogen chloride by oxygen or air in the presence of a copper catalyst. 

Some metals are extracted in electrolytic cells. In section 11.3, you saw the extraction of sodium from molten sodium chloride in a Downs cell. Other reactive metals, including lithium, beryllium, magnesium, calcium, and radium, are also extracted industrially by the electrolysis of their molten chlorides. 

Like the alkali metals, the pure alkaline earth elements are produced commercially by reduction of their salts, either chemically or through electrolysis. Beryllium is prepared by reduction of BeF2 with magnesium, and magnesium is prepared by electrolysis of its molten chloride. 

There are no chemical reducing agents strong enough to reduce compounds of the most active metals, so these metals are produced by electrolytic reduction (Section 18.12). Lithium, sodium, and magnesium, for example, are obtained by the electrolysis of their molten chlorides. Aluminum is manufactured by the electrolysis of purified AI2O3 in molten cryolite (NaaAlFg). 

Recently, Sharma [299], at General Motors, proposed a low cost method for the production of Al-Mg alloys, which can be used in the automobile industry and for desulfurization of steel. The unit cell is shown in Figure 29. The cathode of liquid aluminum is at the bottom of the cell where magnesium is deposited. The electrolyte is a mixture of molten chlorides in which partly dehydrated MgCl2 is dissolved and the electrolysis temperature is 750°C. The same author also described another method to produce magnesium metal using an electrochemical cell with bipolar electrodes, shown in Figure 30. 

The alkaline earth metals show a wider range of chemical properties than the alkali metals. The IIA metals are not as reactive as the lA metals, but they are much too reactive to occur free in nature. They are obtained by electrolysis of their molten chlorides. Calcium and magnesium are abundant in the earth s crust, especially as carbonates and sulfates. Beryllium, strontium, and barium are less abundant. All known radium isotopes are radioactive and are extremely rare. 

Davy discovered several elements in this way, beginning in 1807. After releasing purified potassium metal from potassium hydroxide, it took him only a year to produce magnesium, strontium, barium, and calcium. Fewer than 30 elements had been isolated by 1800, but by 1850, more than 50 were known. Most of these new elements were isolated using electrolysis. Figure 17.2 shows the modern commercial electrolysis of molten rock salt. Rock salt is sodium chloride, NaCl. In this process, pure sodium metal and chlorine gas are produced. 

Metallurgy. — The metals of most of the cerium group elements have been prepared, three general methods having been used t (1) fusion of the anhydrous halides with sodium, potassium, calcium, or aluminium (2) electrolysis of the fused chlorides or of a solution of the oxide in the molten fluoride (3) heating the oxides with magnesium, calcium, or silicon. Reduction with aluminium has also been tried, but it is not satisfactory except possibly for cerium itself. Electrolysis has been the most successful, the other methods usually giving at best an alloy. 

Magnesium is often produced by electrolysis of a molten mixed chloride electrolyte containing MgCl2, at 750°C. Molten magnesium is released around the cast steel cathodes. Use an Ellingham diagram to determine the equilibrium potential necessary for decomposition. 

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