Aluminum from dissolved

Most metals will precipitate as the hydroxide in the presence of concentrated NaOH. Metals forming amphoteric hydroxides, however, remain soluble in concentrated NaOH due to the formation of higher-order hydroxo-complexes. For example, Zn and AP will not precipitate in concentrated NaOH due to the formation of Zn(OH)3 and Al(OH)4. The solubility of AP in concentrated NaOH is used to isolate aluminum from impure bauxite, an ore of AI2O3. The ore is powdered and placed in a solution of concentrated NaOH where the AI2O3 dissolves to form A1(0H)4T Other oxides that may be present in the ore, such as Fe203 and Si02, remain insoluble. After filtering, the filtrate is acidified to recover the aluminum as a precipitate of Al(OH)3. 

The process for obtaining aluminum from bauxite was worked out in 1886 by Charles Hall (1863-1914), just after he graduated from Oberlin College. The problem that Hall faced was to find a way to electrolyze Al203 at a temperature below its melting point of 2000°C. His general approach was to look for ionic compounds in which Al203 would dissolve at a reasonable temperature. After several unsuccessful attempts, Hall found that cryolite was the... 

Figure 13-10 Relation of total aluminum (including dissolved and suspended species) in 1 000 Norwegian lakes as a function of the pH of the lake water. The more acidic the water, the greater the aluminum concentration. [From G. Howells. Acid Rain and Add Waters, 2nd ed. (Hertfordshire Elis Horwood, 1995).]...

Determine the amount (in moles) of electrons needed to produce the indicated substance in an electrolytic cell (a) 5.12 g of copper from a copper(II) sulfate solution (b) 200 g of aluminum from molten aluminum oxide dissolved in cryolite (c) 200 L of oxygen gas at 273 K and 1.00 atm from an aqueous sodium sulfate solution. 

Total (dissolved plus particulate) aluminum concentrations in North Atlantic precipitation samples collected in 1988 ranged from 6.1 to 824 g/L (ppb). A comparison with atmospheric aluminum concentrations presented previously indicates that one liter of precipitation cleanses the aluminum from an equivalent of 0.5 to 7 million cubic meters of air. 

Nitric acid reacts with all metals except the precious metal series and certain alloys. Although chromium, iron and aluminum readily dissolve in dilute nitric acid, the concentrated acid forms a metal oxide layer that protects (passivates) the metal from further oxidation53. 

Leaching by chemically dissolving the aluminum from Raney alloys (Ni, Co, Fe, and Cu) can be mentioned here (see this Handbook, Part A, chapter 2.1.2). Melt-... 

Thirty-three grams (0.19 mol) of aluminum ethoxide is vacuum-distilled into a 250-ml. round-bottomed flask, and 80 g. (0.6 mol) of vacuum-distilled ethyl acetoacetate (59.8° at 8 mm.) is added. Other aluminum alkoxides cannot be substituted successfully for aluminum ethoxide in this synthesis since some substitution of the alkyl group of the alk-oxide, for ethyl, appears to occur in the resulting aluminum acetoacetate derivative. The flask is fitted with a reflux condenser, and the mixture is heated gently with an oil bath the temperature is raised gradually from 85 to 140° over a period of 4 hours. The aluminum ethoxide dissolves slowly as the reaction proceeds, and the ethyl alcohol formed is distilled off at 170° and 25 mm. (A considerably lower temperature can be used if a better vacuum source is available.) At the end of 4 hours the product is cooled to room... 

Recent studies have very clearly delineated the importance of aluminum in sediments for both the opal dissolution rate and the observed asymptotic H4Si04 concentration. The incorporation of aluminum into opal and the hypothesized reprecipitation of H4Si04 from dissolving opal suggest that the silica cycle may exert a significant influence on the cycling of major constiments... 

Copper and aluminum wire seem similar. Both are used in electrical wiring. But the aluminum visibly dissolves in this caustic solution, and the copper wire does not. The bubbles you observed rising from the dissolving aluminum are hydrogen, which explains why thin strips of aluminum foil are added to some lye-based drain cleaners to provide agitation to help break up clogs. 

X-Ray photoelectron spectroscopy data showed an increase of about 20% in the Al/Si ratio as the outgassing temperature was increased from 773 to 1173 K, indicating that the surface concentration of A1 increased (169). Treat-ment with HCl to dissolve nonstructural aluminum produced a 15% decrease in the aluminum content of the sample calcined at 1173 K with respect to the 773 K sample. Subsequently, a small extent of dealumination occurred during the dehydroxylation at high temperature. It was suggested that aluminum from the lattice was extracted on calcination and resulted in an aluminalike species that stayed within the cavities of the zeolite. 

In another experiment, residual WTR after DMP treatment was used as feed, and fresh WTR used as sweep solution for the diffusion dialysis experiment. The total aluminum recovered with time was noted on both the feed and sweep side. The results are shown in Figure 34.30. It can be observed that the pH dropped to a significant value on the sweep side from 6.9 to 3.5. Simultaneously, about 40% of total aluminum was dissolved in the process. 

Approximately 9 parts by weight of the oxime of phenylpropanone was dissolved in approximately 60 parts by weight of 95% ethanol, containing 5 parts by weight of a nickel catalyst, prepared by dissolving aluminum from a nickel-aluminum alloy by means of caustic alkali. The resulting mixture was sealed in a bomb under a hydrogen pressure of 1880 lbs. per sq. in. and reduction was effected for a period of 3-1/3 hrs. at a temperature of 25° C., at the conclusion of which period the pressure was found to have dropped to approximately 1680 lbs. per sq. in. The pressure was then released and the catalyst removed by... 

Good descriptions of the production of aluminum can be found in the literature (Grjotheim etal. [7], Grjotheim and Welch [8], Grjotheim and Kvande [9], Burkin [10], and Peterson and Miller [11]). Referring to Fig. 2 [12], the first step in the production of aluminum from its ore ( bauxite ) is the selective leaching of the aluminum content (present as oxides/hy dr oxides of aluminum) into hot concentrated NaOH solution to form sodium aluminate in solution. After solution purification, very pure aluminum hydroxide is precipitated from the cooled, diluted solution by addition of seed particles to nucleate the precipitation. After solid-liquid separation the alumina is dried and calcined. These operations are the heart of the Bayer process and the alumina produced is shipped to a smelter where the alumina, dissolved in a molten salt electrolyte, is electrolyt-ically reduced to liquid aluminum in Hall- Heroult cells. This liquid aluminum,... 

Carbothermic reduction in the presence of an alloying element, such as copper, iron, or silicon, to decrease aluminum vapor pressures decreases volatility problems but requires a further stage to recover aluminum from the alloy product. It may be selectively dissolved from the alloy with a more volatile metal, such as mercury, lead, or zinc, and then the aluminum recovered by distillation. Or, the tendency for aluminum halides to form more volatile monohalides at high temperatures, which revert to the trihalides at lower temperatures (Eq. 12.25) may be employed. 

Recipe from [1170] Metallic aluminum was dissolved in a plastic vessel in 3 M NaOH at 65°C. The solution was aged for 7 days at 25°C, then centrifuged, and the precipitate was washed with diluted HNO, (pH 4) and with water. 

Metals are important resources and have a wide range of applications. Metals are often extracted from ores. Once the ore is mined, the metals must be extracted, usually by chemical or electrolytic reduction. Pyrometallurgy uses high temperatures to convert ore into raw metals, while hydrometalluigy employs aqueous chemistry for the same purpose. The methods used depend on the metal and their contaminants. Most metals are obtained by hydrometallurgical processes such as aqueous acids or alkalis are predominantly used to dissolve the metal oxides, sulfides, or silicates. Electrowinning and solvent extraction are frequently used to recover and concentrate the metals. A limited number of high-temperature molten salts have also been used for the recovery of refractory metals, such as titanium and aluminum, from their ores... 

CHEMICAL PROPERTIES stable under ordinary conditions of use and storage reported to dissolve aluminum from scratched or heated aluminum surfaces conditions which may contribute to instability include distilling to dryness and excessive temperatures or prolonged reflux, such as in batch distillations hazardous polymerization will not occur can react with strong oxidizers and alkalies FP (39°C, 102°F) LFLAJFL (1.8%, 14%) AT (286°C, 547°F). 

A quantitative study was made of the products resulting from the reaction of air with aluminum bromide dissolved in n-butane in molal proportions C4Hio/AlBrs/Oj=100/9.5/0.30. It was found that all of the oxygen entered the reaction the gases which were pumped off, to 10 nun. of mercury at liquid nitrogen temperature, consisted of 95% nitrogen and... 

The thermodynamic data for fluoride complexes of aluminum, from published literature (12), were recalculated to zero ionic strength by means of the Debye-Hiickel equation. These, with stability data from our experiments with aluminum hydroxide species, provide a basis for deciding which complexes will be predominant when pH and dissolved fluoride concentrations are known. Conclusions drawn concerning the hydroxide species show that the polymeric aggregates of Al(OH)3 should be considered colloidal and they are not included in this calculation as equilibrium solute species. Hydroxide complexes of significance are the monomer A10H- and the anion Al(OH)4". Fluoride complex species constitute the series AlFn " where n ranges from one to six. 

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