Alumina concentration

Figure 6. Spectra of NO on Co 8X Mo/Flltrol 90 alumina. Concentrations of Co (wt%) are Indicated on spectra.

Beck and Brink [28] have described a sensitive method for the routine assay of cobalamins in activated sewage sludge. The method involves extraction with benzyl alcohol, removal of interfering substances using a combination of gel filtration and chromatography on alumina, concentration of the extract by lyophilization, and direct determination of total cobalamin by high-speed liquid chromatography, in comparison with cobalamin standards. 

To what extent is the macroscopic proton release the direct expression of the metal/surface site reactions Table V compares the macroscopic proton coefficients (Xp ) ) with the coefficient expected if only the Cd(II) surface reactions are considered is the proton coefficient determined by considering the mole fraction of Cd(II) surface species and their formation reactions (Figure 14b). For example, when pSOH is 2.84, y = 0.11 x 1 + 0.89 x 2 = 1.89. At high alumina concentrations pSOH 2.14-2.53) the single surface reaction required to fit the data sets a limiting proton release of 2.0. 

After appropriate dilutions, samples collected for concentration determinations were analysed using the sodium gluconate - potassium fluoride method on a dosimate-titrator (Kirke, E.A., Alcoa of Australia, Kwinana, personal communication, 1986). Total alkaline, totd caustic and alumina concentrations were determined using this method. 

The relationship between aluminous sepiolite and the magnesian form is not at all clear as yet. The question of whether or not aluminous sepiolite can be precipitated directly from solution should be posed since alumina concentration in alkaline solutions (pH 7-9) is assumed to be quite low. For the present, palygorskite should probably be considered as a phase produced through solid-solution equilibria due to its high alumina content. Possibly most sepiolites are produced in this way. Even the inonomineralic deposits in saline lakes or deep sea cores contain sepiolites with high alumina contents (Parry and Reeves, 1968 McLean, et al., 1972). 

The heat of dissolution of alumina in molten cryolite, AHiis, varies with the alumina concentration, an average value [161] being AHiis = 125,000 J mol-1. When a large quantity of alumina is added to the bath, the heat needed for its heating from room temperature to the electrolyte temperature and the heat of dissolution are taken from the bath. For this reason, localized freezing occurs, with the formation of aggregates which tend to drop to the bottom of the cell. In this manner a sludge is formed [161]. 

Lillebuen and Mellerud [223] developed a model for the current efficiency as a function of various parameters. The variation with the alumina concentration showed a curve with a minimum at about 4% A1203. The authors showed that the reoxidation reaction rates may be limited by gas dissolution at low alumina contents. The presence of rather large gas bubbles reduces the gas-bath interfacial area to such a degree that the reoxidation reaction rates are being reduced and the current efficiency increased, in spite of the fact that metal solubility is increased at lower alumina concentrations [195,196,223], The current efficiency increases for alumina concentrations over 4% due to the decrease of the metal solubility in the electrolyte [195],... 

Total concentrations of silica and alumina in the fuel were 1.4 wt.% and O.S wt.% respectively (both values imply substantial soil contamination of the fuel, predominantly the wood fuel). Recoveries are good given the high silica and alumina concentrations of the bed media. Titanium, phosphorus and iron were mostly found in the coarse ash fraction and in the particle fraction of the stack flow. Alkaline-earth and alkali metals in the bed are primarily indicative of the fuel ash remaining in the bed. Substantial fractions of these elements were captured in the coarse ash fractions removed in the horizontal pass and by the cyclone, although about 10% is associated with the fine particle fraction passing the cyclone. Yields for all elements on the deposit probes are low due to the low deposit masses. 

Fig. 13 Linear potential sweep results of Zhu and Sadoway showing a large drop in current at an anode as the potential reaches a few volts (versus AI/AIF3) during the forward sweep and the persistence of the low current as the potential is subsequently swept downward. Note the dependence on alumina concentration [31],...

A very recent fundamental investigation of the anode effect is that of Vogt [32] who showed that the effect of alumina concentration on the critical current density (above which an anode effect occurs) can be explained by the alumina mass transfer, fluid dynamics of gas release and wettability of the anode. 

Fig. 31 Measurements of the rate of corrosion of a NiO-NiFe2C>4-Cu cermet anode material as a function of alumina concentration in the electrolyte. From the work of Xiao et al. [102],...

The critical parameter governing the initial layer formation was found to be the ratio of the particle diameter (in the colloidal suspension) to the pore diameter of the support. Given a certain colloidal suspension (characterised by its alumina concentration, kind and concentration of peptising acid used and ageing time) gel films could be formed on a support with pores below a critical diameter as shown in Table 8.1 [2,3]. 

By Photorearrangement of Iminoether 13 8-Methoxy-7-azabicyclo[4.2.2]deca-2,4,7,9-tetraene (13,2.4 g, 0.015 mol) was dissolved in reagent grade acetone (500 mL) and this solution was irradiated through a Pyrex filter sleeve as above. After 8 h, the solvent was evaporated in vacuo, and the resulting yellowish oil was dissolved in hexane (50-75 mL) and clarified by filtration through neutral alumina. Concentration afforded a colorless oil which was crystallized from pentane to give the product yield 2.1 g (88%) as white crystals, mp 49.5-50.5 C, identical in all respects with the sample from lactam 12. 

At low oxide content and at high alumina concentration, the reaction is 2Na3 AlFe + 3AI2O3 = 3Na2Al202F4... 

Catalyst 2, prepared from a less reactive silica sol of larger average particle size than catalyst 1 (about 12 my) begins to form gamma-alumina at about 800°. The gamma-alumina concentration steadily increases up to about 23 % in the temperature range from 800 to 1010°. Below 1010° the... 

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