Trivalent Aluminum Ions Research Articles

Interdiffusion studies in the system MgOAl 2O 3

The rate of formation of single crystal MgAl 2O 3 by reaction between single crystals MgO and Al 2O 3 can be described by k = 1·19 × 10 2 exp ( −88,000 RT ) above 1750°C, and below this temperature by k = 1·17 × 10 4 exp ( −125,000 RT ) . The reaction rate was independent of the crystallographic orientation of Al 2O 3 crystals. Interdiffusion coefficients of Al 3+ ions in MgO were determined over the temperature range 1565–1900°C. Wagner's recent analysis and the graphical technique by Greskovich and Stubican were used for the calculation of interdiffusion coefficients. For a concentration of one mole % Al 2O 3 in MgO the interdiffusion coefficient can be expressed as D ́ = 2·20 exp ( −76,000 RT ) . The interdiffusion coefficients increased with the mole fraction of cation vacancies. They were independent of the crystallographic orientation of the Al 2O 3 crystals and were in the range of 10 −7–10 −10 cm 2 sec −1 for the temperatures and concentrations studied. The enhanced diffusion below 1620°C was observed if the powdered Al 2O 3 was used. The selfdiffusion coefficient of Al 3+ and Cr 3+ ions in MgO were calculated. Trivalent aluminum ions diffuse faster than Cr 3+ ions in MgO.

Electrokinetic Behavior of Aluminum Species in Dilute Dispersed Kaolinite Systems

The objective of this study was to examine the specific behavior of the different aluminum ion species including hydrated trivalent aluminum ion, hydrolyzed polymeric multivalent aluminum ions, and colloidal aluminum hydroxide in aluminum‐kaolinite interactions with the subsequent destabilization of a dispersed system of negatively charged clay particles. The major experimental work investigated the various destabilization phenomena at three arbitrarily chosen final pH values: pH 3, pH 5, and pH 8. Microelectrophoretic techniques were used throughout this study in order to reveal any significant differences in the electrokinetic properties of the flocs which might be attributed to specific hydrolysis products, and also to elucidate the charge reversal phenomena due to the specific adsorption of the polymeric multivalent aluminum ions.

The effect of the lattice on the optical absorption band width and the Raman effect of the U-centre

The rate of formation of single crystal MgAl2O3 by reaction between single crystals MgO and Al2O3 can be described by k = 1·19 × 102 exp (−88,000RT) above 1750°C, and below this temperature by k = 1·17 × 104 exp (−125,000RT). The reaction rate was independent of the crystallographic orientation of Al2O3 crystals.Interdiffusion coefficients of Al3+ ions in MgO were determined over the temperature range 1565–1900°C. Wagner's recent analysis and the graphical technique by Greskovich and Stubican were used for the calculation of interdiffusion coefficients. For a concentration of one mole % Al2O3 in MgO the interdiffusion coefficient can be expressed as D́ = 2·20 exp (−76,000RT). The interdiffusion coefficients increased with the mole fraction of cation vacancies. They were independent of the crystallographic orientation of the Al2O3 crystals and were in the range of 10−7–10−10 cm2 sec−1 for the temperatures and concentrations studied. The enhanced diffusion below 1620°C was observed if the powdered Al2O3 was used.The selfdiffusion coefficient of Al3+ and Cr3+ ions in MgO were calculated. Trivalent aluminum ions diffuse faster than Cr3+ ions in MgO.

Phonons in crystalline solids and dilute bose gases

The rate of formation of single crystal MgAl2O3 by reaction between single crystals MgO and Al2O3 can be described by k = 1·19 × 102 exp (−88,000RT) above 1750°C, and below this temperature by k = 1·17 × 104 exp (−125,000RT). The reaction rate was independent of the crystallographic orientation of Al2O3 crystals.Interdiffusion coefficients of Al3+ ions in MgO were determined over the temperature range 1565–1900°C. Wagner's recent analysis and the graphical technique by Greskovich and Stubican were used for the calculation of interdiffusion coefficients. For a concentration of one mole % Al2O3 in MgO the interdiffusion coefficient can be expressed as D́ = 2·20 exp (−76,000RT). The interdiffusion coefficients increased with the mole fraction of cation vacancies. They were independent of the crystallographic orientation of the Al2O3 crystals and were in the range of 10−7–10−10 cm2 sec−1 for the temperatures and concentrations studied. The enhanced diffusion below 1620°C was observed if the powdered Al2O3 was used.The selfdiffusion coefficient of Al3+ and Cr3+ ions in MgO were calculated. Trivalent aluminum ions diffuse faster than Cr3+ ions in MgO.

Hydrolysis and Exchange Reactions of the Aluminum Ion in Hectorite and Montmorillonite Suspensions

AbstractThe hydrolysis and exchange reactions of the aluminum ion in hectorite and montmorillonite clay suspensions were studied in an attempt to characterize the nature of exchangeable and nonexchangeable aluminum. In agreement with theoretical considerations of the effect of charge on the electrostatic adsorption of ions, the degree of hydrolysis of the aluminum ions adsorbed on the clay was found to be lower than that in the equilibrium dialyzate. The degree of hydrolysis of the aluminum ions in the dialyzate was, in turn, shown to be lower than that of an aqueous aluminum chloride solution having the same total concentration of aluminum as the dialyzate. The hydrolysis of aluminum ions in clay suspensions is thus suppressed rather than increased as has been suggested. Consistent with this observation, virtually all of the exchangeable aluminum was found to be present in the form of trivalent aluminum ions without any evidence for the formation of basic polymeric aluminum ions even upon addition of moderate amounts of base. It was also shown why the region of maximum buffer action of an Alsaturated clay may differ markedly from that given by the pK value corresponding to the first‐stage hydrolysis of the aluminum ion. The fixation of aluminum by clays in nonexchangeable form was not found to produce any substantial reduction in exchange capacity, and was, therefore, attributed to precipitation of aluminum hydroxide.

Inorganic pH Dependent Cation Exchange Charge of Soils

AbstractSodium hydroxide titration curves were determined on H resin treated montmorillonite, untreated acid and neutral soils of different origins and on the same soils with an H resin treatment. The acid montmorillonite titration curve reveals four buffer ranges corresponding to hydronium ions (range I), monomelic trivalent aluminum ions Range II), and two pH dependent charge ranges. Untreated acid soils contained pH dependent buffer zones governed jointly by the organic fraction, the soil pH, the presence of monomeric trivalent aluminum, and the exchange blocking mechanisms of other cations. Following an H resin treatment, soils containing less than 2 per cent of organic matter exhibited a clearly defined third buffer range (Range III) from pH 5.5 to 7.6. The inflection points are masked in the pH dependent buffer range in soils containing more than 2 per cent organic matter. The presence of added aluminum increased the pH dependent charge in an acidified montmorillonite while added ferric iron slightly decreased it. The natural acid weathering processes in soils result in some blocking of pH dependent charge as in Dodge soil of Wisconsin (KCl pH 4.5). When greater acidity develops, a large pH dependent charge results, as in Coolville soil in Ohio (KCl pH 4.0), and the lime requirement of the soil thus increases greatly.