Aluminum hydrometallurgy

The Alcoa (Aluminum Company of America) process involves the electrolysis of aluminum chloride which is carried out in a molten bath of the composition 50% sodium chloride, 45% lithium chloride and 5% aluminum chloride, maintained at 700 °C. The Bayer process, which involves the production of pure alumina by the dissolution of bauxite with caustic soda and which has been described in the chapter on hydrometallurgy, must be taken into account while presenting a complete picture of the aluminum extraction flowsheet. It... 

Zhang, P. W. Inoue, K. Yoshizuka, K. Tsuyama, H. Extraction and selective stripping of molybdenum(VI) and vanadium(IV) from sulfuric acid solution containing aluminum(III), cobalt(II), nickel(II) and iron(III) by LIX 63 in Exxsol D80. Hydrometallurgy 1996, 41, 45-53. 

One of the most important developments in the field of hydrometallurgy has been the application of elevated pressures and temperatures to complex sulfide and oxide ores (B21, F8, G8, M5, M6). The pressure-leaching of bauxite ores by the Bayer process (E3) is probably the first successful commercial application of this technique. The bauxite ore is leached with sodium hydroxide solution with a specific gravity of 1.36-1.4 at 160-170°C for 1 2 hr under a working pressure of 100 psig. The alumina is produced by calcining the aluminum hydrate precipitated from the leach liquor. 

The metals considered by the NCST are aluminum, copper, lead, zinc, and magnesium. With a view toward the demand for these metals and their alloys, the plans proposed by the NCST panel include (I) facilities for hydrometallurgy and electrometallurgy, (2) production of magnesium, and (3) production of high-strength aluminum and magnesium alloys for the defense and space industries. 

Industrial applications of diffusion dialysis for acid recovery include recovery of acids from waste acid from surface treatment of steel and stainless steel, from alumilite treatment, from the etching process of aluminum and titanium, and in other hydrometallurgy industries. The recovery rate of acid can be controlled by changing the flow velocity of the waste solution and water in the dialyzer, in which solutions flow counter-current. For hydrochloric acid, as explained before,... 

In the past hundred years, a different process, hydrometallurgy hydro means "water"), has been employed to extract metals from ores by use of aqueous chemical solutions, a process called leaching. The first two uses of hydrometallurgy were for the extraction of gold from low-grade ores and for the production of aluminum oxide, or alumina, from bauxite, an aluminum-bearing ore. 

Annamalai V, Hiskey JB, Murr LE (1978) The effects of kinetic variables on the stmcture of copper deposits cemented on pure aluminum discs a scanning electron microscopic study. Hydrometallurgy 3 163... 

Pyrometallurgy, metallurgy at high temperatures, is considered with particular attention to iron. Hydrometallurgy, the extraction of metals using aqueous solutions, is discussed with particular attention to aluminum. 

Section 23.3 Hydrometallurgy is tiie use of chemical processes occurring in aqueous solution to separate a mineral from its ore or one particular element from otiiers. In leaching, an ore is treated with an aqueous reagent to dissolve one component selectively. In e Bayer process aluminum is selectively dissolved from bauxite by treatment with concentrated NaOH solution. 

In electrometallurgy, electrolysis is used to produce metals from their compounds. For example, the Hall process is an electrometallurgical process crucial to aluminum production. The main source of aluminum is bauxite, AI2O3 n H2O. A hydrometallurgi-cal process, the Bayer process, separates bauxite from the irou aud silicon dioxide with which it is usually found. In this process, the bauxite is heated in a concentrated aqueous NaOH solution under high pressure. The aluminum oxide dissolves, leaving the other oxides behind in solid form. 

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