Aluminum, hydrous oxides

Aluminum, although highly electropositive, does not react with water under ordinary conditions because it is protected by a thin (2—3 nm) impervious oxide film that rapidly forms even at room temperature on nascent aluminum surfaces exposed to oxygen. If the protective film is overcome by amalgamation or scratching, water rapidly attacks to form hydrous aluminum oxide. Because of the tendency to amalgamate, aluminum and its alloys... 

As pH rises, the metal content of drainage water tends to decrease. Some metals precipitate directly from solution to form oxide, hydroxide, and oxy-hydroxide phases. Iron and aluminum are notable is this regard. They initially form colloidal and suspended phases known as hydrous ferric oxide (hfo, FeOOH n O) and hydrous aluminum oxide (HAO, AlOOH nH.2O), both of which are highly soluble under acidic conditions but nearly insoluble at near-neutral pH. 

A number of reagents containing oxide components are used in zeolite manufacture [19]. Silica is provided by addihon of sodium or other alkali silicate solutions, precipitated, colloidal, or fumed silica, or tetraalkylorthosihcate (alkyl = methyl, ethyl) and certain mineral silicates such as clays and kaolin. Alumina is provided as sodium aluminate, aluminum sulfate soluhon, hydrous aluminum oxides such as pseudo boehmite, aluminum nitrate, or aluminum alkoxides. Additional alkali is added as hydroxide or as halide salts, while organic amines and/or... 

Reacts with caustic soda solution forming gelatinous precipitate of aluminum hydroxide (hydrous aluminum oxide) yields aluminum monobasic stearate, A1(OH)2[OOC(CH2)i6CH3] when its solution is mixed with a solution of sodium stearate. 

Aluminum occurs widely in nature in silicates such as micas and feldspars, complexed with sodium and fluorine as cryolite, and in bauxite rock, which is composed of hydrous aluminum oxides, aluminum hydroxides, and impurities such as free silica (Cotton and Wilkinson 1988). Because of its reactivity, aluminum is not found as a free metal in nature (Bodek et al. 1988). Aluminum exhibits only one oxidation state (+3) in its compounds and its behavior in the environment is strongly influenced by its coordination chemistry. Aluminum partitions between solid and liquid phases by reacting and complexing with water molecules and anions such as chloride, fluoride, sulfate, nitrate, phosphate, and negatively charged functional groups on humic materials and clay. 

EC is a simple, efficient, and promising method to remove arsenic form water. Arsenic removal efficiencies with different electrode materials follow the sequence iron > titanium > aluminum. The process was able to remove more than 99% of arsenic from an As-contaminated water and met the drinking water standard of 10p,gL 1 with iron electrode. Compared with the iron electrodes, aluminum electrodes obtained lower removal efficiency. The plausible reason for less arsenic removal by aluminum in comparison to iron could be that the adsorption capacity of hydrous aluminum oxide for As(III) is much lower in comparison to hydrous ferric oxides. Comparative evaluation of As(III) and As(V) removal by chemical coagulation (with ferric chloride) and electrocoagulation has been done. The comparison revealed that EC has better removal efficiency for As(ni), whereas As(V) removal by both processes was nearly same (Kumar et al. 2004). 

Sodium Tetraphenylborate TS Dissolve 1.2 g of sodium tetraphenylborate in water to make 200 mL. If necessary, stir for 5 min with 1 g of freshly prepared hydrous aluminum oxide, and filter to clarify. 

Bauxite Mixture of hydrous aluminum oxides Major source of aluminum... 

Hydrous aluminum oxide is used frequently in chromatographic columns. Hydrous oxides of Ga, In, and the lanthanides may also be employed as inorganic ion exchangers. However, substantive research of these oxides has not been performed. 

Table 5. Spectroscopic Studies of Arsenic(V) Sorption on Hydrous Aluminum Oxides and Aluminosilicate Clay Minerals.

Ghosh, M. M., and Teoh, R. S., 1985, Adsorption of arsenic on hydrous aluminum oxide in 7th Mid-Atlantic Industrial Waste Conference, Lancaster, Pennsylvania, p. 139-155. 

Amorphous aluminum oxide has recently been proved to extract lithium from brines and bitterns having lithium concentrations of 0.83 and 13.1 mg/1, respectively. The sorption may be explained by the formation of hydrous lithium aluminum oxide. The sorption capacity of amorphous hydrous aluminum oxide was found to be 4.0 mmol/g. For brines and bitterns the lithium concentration factors on the sorbent attained values of 370 and 130, respectively equilibrium was reached after 7 days. The desorption of lithium ions was carried out with boiling water yielding a maximum concentration factor of lithium in the eluate of 46 in reference to the initial lithium concentration of the brines. Lithium was separated from the eluates by solvent extraction with cyclohexane containing thenoyltrifluoracetone and trioctyl-phosphine oxide, subsequent back extraction with hydrochloric acid, and precipitation of lithium phosphate by addition of K3P04. The purity of the precipitate amounted to at least 95% I7 21). 

Instead of hydrous aluminum oxide, aluminum foils have very recently been proposed for the extraction of lithium from sea water. However, not the aluminium metal itself, but its corrosion product hydrous aluminum oxide formed in sea water on the metal surface was found to be the effective lithium binding agent15) thus, there seems to be no fundamental difference compared to the direct application of pure hydrous aluminum oxide. 

Hydrous aluminum oxide /°H —Al oh Li Elution with boiling water. Maximal concentration factor 46 in the eluate 17-21)... 

PZCs/IEPs of hydrous aluminum oxides (nominally AEO, wIEO) are presented in Tables 3.210 through 3.214. There may be some overlap between materials presented in this section, and those presented in Sections 3.1.1.2 and 3.1.1.4. 

PZC/IEP of Hydrous Aluminum Oxide from Carlo Erba... 

Pommerenk, P. and Schafran, G.C., Adsorption of inorganic and organic ligands onto hydrous aluminum oxide Evaluation of surface charge and the impacts on particle and NOM removal dtrring water treatment. Environ. Sci. Technol., 39. 6429. 2005. 

Sorption of As(III) to Fe(III) oxyhydroxides has been widely observed (101,105-107,109). At high pH values, As(III) can be sorbed to a greater extent than As(V). Sorption of As(III) on clays and amorphous aluminum hydroxide has been reported (102). However, removal of As(III) by coagulation with alum is generally poor (110,111). Adsorption experiments conducted with hydrous aluminum oxide under conditions comparable to water treatment with coagulants (pH 6, 120 pM total Al) showed 99% removal of As(V) but only 3% removal of As(lll) at initial arsenic concentrations of 10 and 100 pg/L (112). 

Aluminum acetylacetonate was first prepared by Combes by treatment of a mixture of hydrous aluminum oxide and acetylacetone with hydrochloric acid. Gach made the compound by the action of aluminum amalgam on acetylacetone, while Urbain and Debierne used anhydrous aluminum chloride and acetylacetone. The recommended procedure was first described by Biltz. ... 

E. Barouch, Heterocoagulation. VI. Interactions of monodispersed hydrous aluminum oxide sol with polystyrene latex, /. Colloid Interf. Sci. 1980, 76,319-329 (c) K. Csoban, E. PefFerkorn, Perikinetic aggregation induced by chromium hydrolytic polymer and sol,/. Colloid Interf. Sci. 1998, 205,516-527. 

Monomeric silica is strongly adsorbed onto the surface of hydrous aluminum oxides. There is a reaction between SiCOH) and crystalline Al(OH)j by which several reaction layers of Si02 are built up, with simultaneous decrease in pH of the suspension (68a). Formation of the first layer is rapid, but the second and third layers form progressively much more slowly. It would seem that diffusion of Al" " or AlOj" from the surface of the crystal must be involved, with the formation of a silica-rich aluminosilicate. A relatively low content of aluminum ion in the SiO-layer greatly reduces its solubility, thus explaining the deposition of SiO from a solution unsaturated with respect to pure amorphous silica. 

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