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Structure hydroxylated surfaces

Some metals are amphoteric. That is, they form simple cations (in acid solutions) and soluble oxyanions (in alkaline solution) only in the mid-pH range is a protective film stable. Since cathodic protection produces alkali at the structure s surface, it is important to restrict the polarisation, and thereby the amount of hydroxyl ion produced, in these cases. Thus both lead and aluminium will suffer cathodic corrosion under cathodic protection if the potential is made excessively electro negative. [Pg.122]

It i.s easiest to get a picture of the chemical structure of the surface of aluminas by starting from a fully hydroxylated surface (Fig. 3.20). [Pg.75]

Liou, Y. C., Tocilj, A., Davies, P. L., andjia, Z. (2000). Mimicry of ice structure by surface hydroxyls and water of a beta-helix antifreeze protein. Nature 406, 322-324. [Pg.94]

As mentioned above, an acidic zeolite can provide both protonic (Bronsted) and aprotonic (Lewis) sites. The Bronsted sites are typically structural or surface hydroxyl groups and the Lewis sites can be charge compensating cations or arise from extra-framework aluminum atoms. A basic (proton acceptor) molecule B will react with surface hydroxyl groups (OH ) via hydrogen bonding... [Pg.124]

Hydrated iron oxides can adsorb heavy metals. These adsorption properties arise from the presence of structural hydroxyl groups on their surface, which exhibit amphoterism (56) ... [Pg.269]

HYDROGEN BONDS BETWEEN ADSORBED MOLECULES AND THE STRUCTURAL HYDROXYL GROUPS AT THE SURFACE OF SOLIDS... [Pg.545]

The clay minerals are layer structures (38, 39, 86) incorporating, for example, sheets of interconnected Si04 tetrahedra cross-linked with sheets of A10<5 octahedra. Particles have broken bonds only on the edges of sheets. The broken bonds hydroxylate they and structural OH on the layer surfaces can dissociate to produce a pH-dependent charge in the same way as described for the surfaces of simpler oxides. Charge from this source may be referred to as originating in the hydroxylated surface. [Pg.140]

The structural and spectral complexity of clay minerals is sufficient to consider a single mineral as a multicomponent mixture in itself. Detectible by near infrared spectroscopy are adsorbed water and structural hydroxyls (25.) exchangeable and structural transition metal cations (2fL and this work), adsorbed species including atmospheric gases (22), organic materials (2) accessory minerals (2SL) and, possibly, trapped hole centers (0 -centers). Thus it is of interest to adapt NIRA to studies of mineral surface activity. We have done this by examination of a small set of highly homologous clays in which laboratory control of only one variable at a time could be accurately achieved and independently confirmed. [Pg.409]

All silicas dried from water at less than 150°C have a fully hydroxylated surface in which the surface structure terminates in silanol groups. This is readily wettable by water and water-soluble organic molecules. [Pg.313]

V. A. Tretikh, V. V. Pavlov, K. 1. Tkachenko, and A. A. Chuiko, Distribution of structural hydroxyl groups on an Aerosil surface, Theor. Eksp. Khim. 11 (1975),415 17. P. Roumeliotis and K. K. Unger, Structure and properties of -alkyldimethylsilyell-bonded silica reversed-phase packings,/. Chromatogr. 149 (1978),211-224. [Pg.135]

In conclusion, structural hydroxyl groups are observed on the surface of REY. Their formation is attributed to water ionzation by strong fields near the cation. This hydrolysis gives rise to RE-OH and a proton the latter reacts with a surface oxygen in the way stated by several investigators ... [Pg.371]


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See also in sourсe #XX -- [ Pg.82 ]

See also in sourсe #XX -- [ Pg.90 ]




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