Aluminum interaction with functional groups

Neutral aluminum(III) species interact with a variety of functional groups. The strong Lewis acidity of aluminum(III) species enables formation of a 1 1 complex by either covalent or coordination bonding - tire former bond is constructed by more reactive anionic species R-M, RO-M or RNH-M (M = metal), and the latter... 

The zeta potential of bare kaolinite clay was determined to be —17.6 mV at pH 5.0. The strong interaction of aluminum ions with kaolinite clay at pH 5.0 was evidenced by (1) the positive values of the potential determined as a function of clay dose (Sample I) and (2) the low residual concentrations of aluminum ions in the supernatant as a function of the clay dose (Samples I and II) (Figure 25). Since the degree of hydrolysis of A1C13 determined at pH 5.0 is function of the aluminum ion concentration below a concentration of 10 mol/L, the net positive charge of the residual aluminum ions in the supernatant is expected to increase with clay dose. Therefore the interaction between modified clay and humic acids should be a function of the aluminum ion concentration, but in the present context only the relative concentration of aluminum ions and acidic groups a = [Al]/[RCOOH] is taken... 

Four different functional groups, CH2, NH2, OH, and COOH, on polypropylene (PP) and on polytetrafluoroethylene (PTFE) (process 3) as well as the unspecific O-functionahzation of these polymers with different types of O-functional groups (process 1) were tested for their adhesion-promoting properties toward aluminum top coatings. Aliphatic groups do not form significant interactions with Al [27, 28] but under appropriate conditions Al-C formation was also observed [29-32]. 

An amino-functionalized Al-sample, NH2-MIL-53(A1), was found to have the same OH groups as the amino-free sample (3700—3693 cm (716—718)) as well as additional hydroxyls (3660 (716) or 3680 cm (717,718)) attributed to OH groups interacting with the amino group via H-bonding (716—718). A decrease in the OH frequency is reported in the sequence aluminum > gallium > indium (717). 

For most samples, which are soluble in organic solvents and of low molecular weight, adsorption chromatography (also called liquid-solid chromatography, LSC) on silica gel, aluminum oxide, or other inorganic oxides is suitable. Separation is based on specific interaction of the functional groups on the surface of the adsorbent with those of the sample. Silica gel is by far the most widely used adsorbent, available in consistent quality and at comparatively low cost. Due to its ionic nature aluminum oxide offers additional selectivity however, it is more difficult to obtain products with consistent separation properties. Therefore, separations on aluminum... 

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