Metal titanium dioxide

SUNETAL. Spectroscopy of Metal-Titanium Dioxide Systems... 

Common pollutants in a titanium dioxide plant include heavy metals, titanium dioxide, sulfur trioxide, sulfur dioxide, sodium sulfate, sulfuric acid, and unreacted iron. Most of the metals are removed by alkaline precipitation as metallic hydroxides, carbonates, and sulfides. The resulting solution is subjected to flotation, settling, filtration, and centrifugation to treat the wastewater to acceptable standards. In the sulfate process, the wastewater is sent to the treatment pond, where most of the heavy metals are precipitated. The precipitate is washed and filtered to produce pure gypsum crystals. All other streams of wastewater are treated in similar ponds with calcium sulfate before being neutralized with calcium carbonate in a reactor. The effluent from the reactor is sent to clarifiers and the solid in the underflow is filtered and concentrated. The clarifier overflow is mixed with other process wastewaters and is then neutralized before discharge. 

Chen J, Ollis DF, Rulkens WM (1999) Kinetic processes of photocatalytic mineralization of alcohols on metallized titanium dioxide. Water Res 33 1173-1180... 

Tiwari, V., Jiang, J., Sethi, V. and Biswas, P. (2008) One-step synthesis of noble metal titanium dioxide nanocomposites in a flame aerosol reactor. Applied Catalysis A General, 345, 241-246. 

See Potassium dioxide Metals Titanium dioxide Metals Zinc peroxide Alone, etc. 

Zakrzewska, K., Radecka, M., Kruk, A. and Osuch, W., Noble metal/titanium dioxide nanocermets for photoelectrochemical applications , Solid State Ionics, 2003 157(1-4) 349-356. 

Although some of the metals in the second and third transition series are certainly important, the first-row metals constitute the extremely significant and useful structural metals. In addition to the metals themselves, an enormous number of alloys containing these metals are widely used, as are many compounds of the metals. Of all the compounds of the transition metals, titanium dioxide, Ti02, is produced in the largest quantity (approximately 2 billion lb/year) because of its extensive use in paints. 

Titanium is neither mutagenic nor carcinogenic. Ti-tanocene (an organic compound), however, induced fibrosarcoma when injected intramuscularly in rats. This same compound was carcinogenic against the Ehrlich ascites tumor in mice. There have been reports of tumors induced with the pure metal. Titanium dioxide did not induce tumors when administered orally however, a few lung tumors were detected after titanium dioxide dust was inhaled by rats. 

Titanium tetrachloride is used as an intermediate in the production of titanium metal, titanium dioxide, and titanium chloride pigments, as a polymerization catalyst, in the manufacture of iridescent glass and faux pearls, and with ammonia to produce smoke screens. It is also used as a catalyst in many organic syntheses in the chemical industry. Titanium tetrachloride was formerly used with potassium bitartrate as a mordant in the textile industry, and with dye-woods in dyeing leather. 

Titanium dioxide can be improved by doping with metals. Titanium dioxide participates in photochemical processes. Its mechanism involves the formation of positive holes in the valence band and electron promotion to the conductive band irradiated by UV. Both electrons and holes react with the surrounding material. By doping Ti02 crystals with various metals, electron and hole recombination centers are formed. Also, the crystal is coated with a layer of hydrous oxides which decompose hydroxyl radicals. This is applied to various grades of Ti02 which gives them a unique performance in applications where UV durability is required. 

Titanium IV) oxide, T1O2. See titanium dioxide. Dissolves in concentrated alkali hydroxides to give titanates. Mixed metal oxides, many of commercial importance, are formed by TiOj. CaTiOj is perovskite. BaTiOa, per-ovskite related structure, is piezoelectric and is used in transducers in ultrasonic apparatus and gramophone pickups and also as a polishing compound. Other mixed oxides have the il-menite structure (e.g. FeTiOj) and the spinel structure (e.g. MgjTiO ). 

Titanium metal is considered to be physiologically inert. When pure, titanium dioxide is relatively clear and has an extremely high index of refraction with an optical dispersion higher than diamond. 

The original yams were marketed as silk substitutes for use in apparel, hosiery, lace, home furnishings, ribbons, braids, and in a whole range of fabrics using blends with cotton or wool yams. As the end uses expanded beyond silk replacement, the harsh metallic luster of the yam proved disadvantageous and dull "matt" fibers had to be developed. Oil dulling was invented (11) in 1926, and an improved method using titanium dioxide was developed (12) in 1929. 

The second form consists of Pt metal but the iridium is present as iridium dioxide. Iridium metal may or may not be present, depending on the baking temperature (14). Titanium dioxide is present in amounts of only a few weight percent. The analysis of these coatings suggests that the platinum metal acts as a binder for the iridium oxide, which in turn acts as the electrocatalyst for chlorine discharge (14). In the case of thermally deposited platinum—iridium metal coatings, these may actually form an intermetallic. Both the electrocatalytic properties and wear rates are expected to differ for these two forms of platinum—iridium-coated anodes. 

Heterogeneous Photocatalysis. Heterogeneous photocatalysis is a technology based on the irradiation of a semiconductor (SC) photocatalyst, for example, titanium dioxide [13463-67-7] Ti02, zinc oxide [1314-13-2] ZnO, or cadmium sulfide [1306-23-6] CdS. Semiconductor materials have electrical conductivity properties between those of metals and insulators, and have narrow energy gaps (band gap) between the filled valence band and the conduction band (see Electronic materials Semiconductors). 

Production. Titanium is the seventh most common metallic element in the earth s cmst. Titanium minerals are plentiful in nature (19). The most common mineral /raw materials used for the production of titanium dioxide pigments are shown in Table 1. 

About 100,000 t of titanium dioxide aimuaHy are used as formulation components in the production of glass (qv), ceramics, electroceramics, catalysts, and in the production of mixed-metal oxide pigments. 

Putile Ceramic Pigments. StmcturaHy, aH mtile pigments are derived from the most stable titanium dioxide stmcture, ie, mtile. The crystal stmcture of mtile is very common for AX2-type compounds such as the oxides of four valent metals, eg, Ti, V, Nb, Mo, W, Mn, Ru, Ge, Sn, Pb, and Te as weH as haHdes of divalent elements, eg, fluorides of Mg, Mn, Fe, Co, Ni, and Zn. 

Catalytic alkylation of aniline with diethyl ether, in the presence of mixed metal oxide catalysts, preferably titanium dioxide in combination with molybdenum oxide and/or ferric oxide, gives 63% V/-alkylation and 12% ring alkylation (14). 

Chemical pigments or synthetics may be metal compounds. A good example is white titanium dioxide. Other chemical pigments include cadmium sulfide colors, iron blue, and several synthetic versions of iron oxides. 

Titanium Monoxide. Titanium monoxide [12137-20-17, TiO, has a rock-salt stmcture but can exist with both oxygen and titanium vacancies. For stoichiometric TiO, the lattice parameter is 417 pm, but varies from ca 418 pm at 46 atom % to 4I62 pm at 54 atom % oxygen. Apparendy, stoichiometric TiO has ca 15% of the Ti and O sites vacant. At high temperatures (>900° C), these vacancies are randomly distributed at low temperatures, they become ordered. Titanium monoxide may be made by heating a stoichiometric mixture of titanium metal and titanium dioxide powders at 1600°C... 

Titanium Sesc uioxide. Ti202 has the comndum stmcture. At room temperature it behaves as a semiconductor having a small (0.2 eV) band gap. At higher temperatures, however, it becomes metallic. This is associated with marked change in the mean Ti—Ti distance. As with TiO, titanium sesquioxide, Ti202, may be made by heating a stoichiometric mixture of titanium metal and titanium dioxide powders at 1600°C under vacuum in an aluminum or molybdenum capsule. 

Hydrated Titanium Oxides. Hydroxides of Ti(Il) (black) and Ti(Ill) (brown) are precipitated when an alkaU metal hydroxide is added to a solution of the corresponding salt. These precipitates, though difficult to purify (45), are powerful reduciag agents and readily oxidize ia air to form a hydrated titanium dioxide. 

The properties of hydrated titanium dioxide as an ion-exchange (qv) medium have been widely studied (51—55). Separations include those of alkaH and alkaline-earth metals, zinc, copper, cobalt, cesium, strontium, and barium. The use of hydrated titanium dioxide to separate uranium from seawater and also for the treatment of radioactive wastes from nuclear-reactor installations has been proposed (56). 

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