Aluminum hydrolysis reactions

Over the last three decades, two general approaches have been proposed in the literature for describing the interactions of sulfate in soils. The first approach is that of a chemical nature where thermodynamic interrelationships with speciation of cations and anions present in soil solution and the interaction with the soil surface are the major mechanisms. These models may be referred to as chemical models. Examples of such models include that of Cosby et al. (1986), Reuss and Johnson (1986), De Vries et al. (1994), among others. A common feature of these models is that both ion exchange and aluminum hydrolysis reactions are similar. Their capability of quantifying these processes varies according to whether the interactions are... 

Hem, J. D., and Roberson, C. E. (1988) Aluminum Hydrolysis Reactions and Products in Mildly Acidic Aqueous Systems. In Chemical Modeling of Aqueous Systems, Vol. II, D. C. Melchior and R. L. Bassett, Eds., ACS Series 416, Washington, DC. 

Aluminum Hydrolysis Reactions and Products in Mildly Acidic Aqueous Systems... 

Aluminum hydrolysis reactions arc particularly sensitive to pH and temperature, and to the concentrations of other ligands that might compete with OH in complex formation. The most important inorganic competitor is F (2). Certain organic ligands also can form strong complexes with aluminum (3). Hydrolysis reactions of aluminum also arc influenced by sulfate, and hydroxysulfate solids may control aluminum solubility in acidic solutions (4). 

Phosphides are binary compounds containing anionic phosphorus (P ). Heavy metal, alkali, and alkaline earth metal phosphides exist but few of them are commercially important. Phosphides hydrolyze to the flammable and toxic gas phosphine (PH3). The hydrolysis reaction of aluminum phosphide is given below ... 

Ethyl aluminum dichloride (EADC) is used in the rnanufacmre of certain catalysts for making LDPE. Occasionally, the batch operation involving the catalyst production results in an off-spec lot. This off-spec lot is washed from the reactor (impregantor) with water and hexane, and must be sent to a waste disposal facility. The facility treats this waste in a hydrolysis reaction (i.e., with water and mild agitation). If the reaction is exothermic, what are the potential air pollution and fire problems associated with the waste treatment ... 

There is another type of hydrolysis reaction that leads to acidic solutions. When a compound such as aluminum chloride is dissolved in water, the cation becomes strongly solvated. The extremely energetic... 

Aluminum polycations are obtained by the controlled hydrolysis of AI(III) solutions the extent of the hydrolysis reaction can be monitored with pH measurements. The products of the hydrolysis reactions, I.e. the successive generation of polycations of Increasing degree of polymerization with Increasing extent of hydrolysis, must be Inferred from non-equilibrium measurements. Thus, equilibria between many polycatlonic species, I.e. [Al2lOH)2] , [A124(0H)5q]" 12, etc., were proposed. More recently, " A1 NMR has... 

In water, the ions of rare earth metals, aluminum and zirconium are hydrolyzed and do not give well-defined polarographic reduction waves. In aprotic solvents, however, the solvolysis reactions do not occur as easily as the hydrolysis reactions in water. Thus, in solvents like DMSO, DMF and AN, these ions give... 

With these kinetic factors in mind, it is still of interest to attempt to get some idea of the possible soluble species and their relationship to aluminum solubility. The data for polymeric aluminum hydrolysis products are those for 50°C. reported by Biedermann (2), who has described the two reactions... 

Because aluminum is a group 3A element, it has an oxidation number of +3. The ethoxide ligand is the anion of ethanol, HOCH2CH3, and has a charge of —1. Since aluminum ethoxide is a neutral compound, its formula must be Al(OCH2CH3)3. The hydrolysis reaction, which breaks the Al-OCH2CH3 bonds and forms Al-OH bonds, requires one H20 molecule for each ethoxide ligand ... 

First investigations of hydrolysis of aluminum alkoxides were performed in the 1950s and 1960s [1252, 285]. Stolarek [1536] studied hydrolysis reactions with the aim of the preparation of aluminum oxide as a carrier for catalysts. 

Pawlowski and Schartel92 have added 1 or 5 wt % of boehmite to blends of PC/ABS with PTFE and RDP or bisphenol A bis(diphenylphosphate). The release of water from AlOOH influences the decomposition of the material by enhancing the hydrolysis of PC and RDP. Consequently, the condensed action of RDP or BDP is perturbed. The reaction of the arylphosphate with boehmite replaces both the formation of anhydrous alumina and alumina phosphate on the one hand, and the cross-linking of arylphosphate with PC on the other hand, since less phosphate is available to perform condensed-phase action. The reaction with arylphosphate therefore decreases the char formation, but the formation of aluminum phosphate could enhance barrier properties. On the whole, even high levels of fire retardancy can be achieved (V-0 ratings) the combination of boehmite with arylphosphates acting in the condensed phase seems very complex, particularly when the host polymer can undergo hydrolysis reactions due to water release. 

Gel Preparation NiO/A C gels are prepared using the method suggested by Teichner and co-workers (4). Aluminum sec-Butylate is dissolved in sec-Butanol while Nickel Acetate is dissolved in Methanol separately. Water is added to the second mixture in near stoichiometric amounts necessary for the hydrolysis reactions. The two solutions are mixed and a precipitate of alumina is immediately formed. Gels are dried immediately after preparation, in order to eliminate the effect of aging (2). 

Similarly, the nitride, carbide, cyanide, carboxylate, and carbonate salts of aluminum are unstable in aqueous solution. Aluminum salts of strong acids form solutions of the hydrated cation (see Hydrates). These solutions are acidic owing to the partial dissociation of one of the coordinated water molecules (equation 6), the p/fa of [A1(H20)6] + being 4.95 (see Acidity Constants). Note that this is quite similar to that of acetic acid. The second step in the hydrolysis reaction yields a dihydroxide species that undergoes condensation to form polynuclear cations (see Section 8). Antiperspirants often include an ingredient called aluminum chlorhydrate that is really a mixture of the chloride salts of the monohydroxide and dihydroxide aluminum cations. The aluminum in these compounds causes pores on the surface of the skin to contract leading to a reduction in perspiration. 

Figure 4 Residues within Ga that are critical to the GTP hydrolysis mechanism include arginine-178 and threonine-181 from switch I and glutamine-204 from switch II (colored as in Fig. 2 and numbered as in Ga i coordinates are from PDB record IGFI). Magnesium ion is highlighted in yellow. The planar anion aluminum tetrafluoride, which mimics the y-phosphate leaving group in the hydrolysis reaction, is depicted in metallic red. Note the position of serine-47, the target of phosphorylation by the Y. pestis protein kinase YpkA.

Solution. We can calculate the concentration of aluminum ion in the solution after treatment with aluminum sulfate without writing the equation for the hydrolysis reaction. It is required by the solubility-product principle that the product of ion concentrations for the precipitated substance Al(OH)3 be equal to the solubility product. The expression in this case is... 

Boer and co-workers examined the reaction of sterically hindered a-chloronitroso compounds with Me3Al [111]. The conspicuous reaction sequence is interpreted in terms of initial ring rupture, methane evolution and chlorine migration from carbon to aluminum intramolecular reaction of the carbon-carbon double bond with the rather electrophilic carbon atom from the nitrile oxide moiety leads to a seven-mem-bered ring with an exocyclic double bond as shown in Sch. 75. After hydrolysis, the corresponding oxime is obtained. 

As discussed above, the presence of AI13 is usually identified via a +62.5 ppm peak in the Al-NMR spectra that arises from the central Al(0)4 site in the s-Keggin-like AI13 structure. Fu et al. (1991) and Nazar et al. (1992) noticed that additional peaks for the A1(0)4 occur in the Al-NMR spectra when AI13 solutions were reacted for extended periods of time at temperatures of 85-90°C and polymerized by titration with base. Peaks in the Al-NMR spectra appear at +64.5, +70.2, and +75.6 ppm as a peak near 0 ppm increases in intensity. The 0 ppm >eak arises from the monomeric aluminum hydrolysis complexes, mostly Al + Al(OH) at 4 < pH < 5. The peak at +64.5 ppm is weak and transient and that at 75.6 ppm only appears after extended periods of reaction. The dominant peak is at 70.2 ppm. 

Consideration of the chemical and physical properties of these accumulated substances permits some further conclusions. The volatility of surface reaction products is likely to be important, as are the ambient concentrations of ammonia, carbon dioxide, and other gases that could influence the surface acidity. Indeed, the ratio of ammonium to sulfate that has been found on zinc and aluminum surfaces after extended exposures is much lower than typical ratios for ammonium to sulfate in airborne particles (4). Clearly, ammonium is able to volatilize from these surfaces through a hydrolysis reaction or, after redistribution of anions and cations on the surface such as... 

We may as an example take the hydrolysis reactions of aluminum as total reactions from Al(OH) (Gibbsite) at an ionic strength of 0.011. The solubihty of Gibbsite has been found to be determined by the following equihbria " ... 

In the open system maintained during these titrations the hydrolysis reactions are driven by the continuous addition of A1 ions. The rate of the hydrolysis reactions can be inferred from the rate of OH addition, with appropriate adjustments, and the reaction kinetics can be evaluated. Early in the titration period the formation of monomeric aluminum hydroxy-ions (Ala) is the only reaction thermodynamically feasible as the solution is below saturation with respect to microcrystalline gibbsite. The solid point in Figure 2 represents the equilibrium concentration of Ala with respect to that solid at 25 C, I = 0.01 and pH 4.90, which was reached in about 50 minutes. 

PILC are prepared by controlled hydrolysis reactions which can be carried out in solution or in the interlamellar space of the clay (the former allows better control of the nature of the polyoxocations). In addition to the different parameters already mentioned, the calcination process also plays a key role. Three general cases may occur (i) the polyoxocations exit from the clay (no pillaring), (ii) they degrade in situ giving rise to layers of aluminum hydroxide (thick ca. 

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