Aluminum complexes mixed oxides

Bauxite, the main aluminum ore, is a mixed oxide-hydroxide, A1(0)0H, contaminated with Si02, Fc2 O3, clay, and other hydroxide salts. To isolate the aluminumcontaining material, the ore is treated with a strongly basic solution, whose high hydroxide concentration causes the solid to dissolve as a soluble complex ion,... 

Binary systems synthesized consisted of Cu/Fe, Ni/Fe, Cu/Al and Ni/Al and Cu/Cr for 4-10 wt percent Cu or Ni in the calcined mixed oxide. Anionic complexing agents acetic, citric and oxalic acids and EDTA were used in molar ratios of 1 1 with the initial copper or nickel. Two stage precipitations were used starting with an initial formation of aluminum, chromium or ferric hydroxide by addition of NaOH to an aqueous solution of A1 nitrate, Cr nitrate or Fe chloride. In the second stage aqueous solutions of Cu sulfate or Ni nitrate were mixed with the initial precipitate with or without the presence of a 1 1 mole ratio of selected anionic complexing agents to complete the precipitation. A second mode of coprecipitation used was to preadsorb oxalic acid on the initially precipitated AI, Cr or Fe hydroxide. 

Aluminum metal is produced from aluminum oxide by electrolysis using the Hall-Heroult process, whose story is detailed in our Chemical Milestones Box. The melting point of AI2 O3 is too high (2015 °C) and its electrical conductivity too low to make direct electrolysis commercially viable. Instead, AI2 O3 is mixed with cryolite (Na3 AlFfi) containing about 10% CaF2. This mixture has a melting point of 1000 °C, still a high temperature but not prohibitively so. Aluminum forms several complex ions with fluoride and oxide, so the molten mixture... 

Some anions exhibit a complexing affinity toward aluminum ions. Thus, in such a situation, one should visualize the presence not only of a series of pure complexes but also of mixed ones with oxygen-containing ions, e.g., Al(OH)2Cl, Al(OH)Cl2, A1C13, Al(OH)Cl+, and A1C12+. The ionic species are soluble, and thus the interaction with complexing ions may provide an additional mechanism for solubilization of the oxide. 

These complex reactions are important for producing aluminum in industry. In the first step, one mixes Bauxite mineral with concentrated sodium hydroxide solution the tetrahydroxoaluminum complex will remove all the aluminum of the Bauxite. Then, aluminum hydroxide must be changed to aluminum oxide this compound is used in smelting flux electrolysis to finally produce pure aluminum metal. 

To a clean dry test tube at the desired temperature, calculated amounts of methyl chloride, 2,4,4-trimethyl-1 -pentene, n-nonane and the alkylaluminum compound were added and the test tube was stoppered with a rubber septum cap. The content of the test tube was mixed by shaking and the calculated amount of f-butyl chloride in methyl chloride solvent was rapidly added with a syringe. After 25 min the reaction was terminated by slow addition of prechilled methanol. During termination the septum cap was removed to prevent pressure build-up due to the formation of gaseous products. The tube was removed from the drybox and the solvent was slowly evaporated. To facilitate the separation of the organic products from the aluminum oxide residues a saturated aqueous sodium-potassium tartrate solution was slowly added at 0° C. On adding excess water, the aluminum oxide-tartrate complex can be dissolved to yield well separated aqueous and organic layers. The... 

The system resulting from mixing of aluminum oxide and polyacrylic acid in aqueous solution was determined to be very complex due to the partial dissolution of the oxide which liberates 10 4 mol/L multivalent aluminum ions in the supernatant at pH 5.0 [79], Definitely to set the chemical composition of the system, the aluminum ion concentration was fixed by dissolving the required amount of A1C13 in 10 3 mol/L KC1 at pH 4.06. Addition... 

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