Silica-coated rutile

Values of A, 4 for nitrogen adsorption at 0 = 0.1 are recorded in Table 10.13, which also contains the corresponding adsorption energy data for silica-coated rutile. It was independently confirmed that the surface properties of the latter sample, which had a coating of 2.6% dense silica, were very similar to those of pure silica (Furlong etal., 1980). 

Table 10.13. Differential energies of adsorption of nitrogen at 77 K on rutile and silica-coated rutile. ...

The surface hydration-hydroxylation structure of titania, proved previously mainly by IR studies using dry titania powders, also seems to hold when these powders are dispersed in water. An interesting approach, therefore, is to probe directly the uptake of water from the gas phase by DS-coated rutile surfaces [42]. Water adsorption isotherms are presented in Figure 52.14. The dual nature of titania surface sites, a property not seen with other common oxides such as silica and alumina, leads to an unusual type of water adsorption isotherm for titania. The isotherm shows two distinct knees (Figure 52.14) connected by a region where adsorption increases linearly with the partial vapor pressure of water. The explanation for this adsorption behavior is rather complex [42] and beyond the scope of this chapter. This behavior is believed to be due to the presence of hydrated surface cation sites. 

Titanium dioxide (E171, Cl white 6) is a white, opaque mineral occurring naturally in three main forms rutile, anatase, and brookite. More than 4 million tons of titanium dioxide are produced per year and it is widely used for industrial applications (paints, inks, plastics, textiles) and in small amounts as a food colorant. ° "° Production and properties — Titanium oxide is mainly produced from ilmenite, a titaniferous ore (FeTiOj). Rutile and anatase are relatively pure titanium dioxide (Ti02) forms. Titanium oxide pigment is produced via chloride or sulfate processes via the treatment of the titanium oxide ore with chlorine gas or sulfuric acid, followed by a series of purification steps. High-purity anatase is preferred for utilization in the food industry. It may be coated with small amounts of alumina or silica to improve technological properties. 

The liquid phase coating of rutile pigments with silica markedly suppressed the activity of the pigments 4 and the modelling of pigment discolouration has been undertaken . In polyethylene... 

Chem. Descrip. Rutile titanium dioxide, alumina/silica surf, treatment Uses Pigment for exterior applies., top coat rigid vinyl siding, acrylic applies., polyester, powd. coatings... 

Chem. Descrip. Rutile titanium dioxide (93%) with alumina/silica/zirconia inorg. coating... 

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