ටයිටේනියම් ඩයොක්සයිඩ්

Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring of , chemical formula O₂. When used as a , it is called titanium white, Pigment White 6, or . It is noteworthy for its wide range of applications, from paint to to when it is given the E number E171.

Occurrence

Titanium dioxide occurs in nature as the well-known naturally occurring minerals , and , additionally two high pressure forms, the form and the α-PbO₂ form have been found at the in . The most common form is rutile, which is also the most stable form. Anatase and brookite both convert to rutile upon heating., anatase and brookite all contain six coordinate titanium. Additionally there are three metastable forms produced synthetically and five high pressure forms:

Form	Crystal system	Synthesis
		Hydrolysis of K2Ti4O9 followed by heating
TiO2(H), form		Oxidation of the related potassium titanate bronze, K0.25TiO2
TiO2(R), form		Oxidation of the related lithium titanate bronze Li0.5TiO2
TiO2(II)-( form)
form, (7 coordinate Ti)
TiO2 -OI
cubic form	cubic
TiO2 -OII, ,

The naturally occurring oxides can be mined and serve as a source for commercial titanium. The metal can also be mined from other minerals such as or , or one of the purest forms, rutile beach sand. and get their from rutile impurities present in them.

Spectral lines from titanium oxide are prominent in stars, which are cool enough to allow molecules of this chemical to form. Titanium Dioxide can be found in most of the leading skin/face products.

නිපදවීම

Crude titanium dioxide is purified via in the . In this process, the crude ore (containing at least 90% TiO₂) is reduced with carbon, oxidized with chlorine to give . This titanium tetrachloride is distilled, and re-oxidized with oxygen to give pure titanium dioxide.

Another widely used process utilizes as the titanium dioxide source, which is digested in . The by-product is crystallized and filtered-off to yield only the titanium salt in the digestion solution, which is processed further to give pure titanium dioxide. Another method for upgrading ilmenite is called the .

භාවිත

Titanium dioxide is the most widely used white pigment because of its brightness and very high (n=2.7), in which it is surpassed only by a materials. Approximately 4 million tons of pigmentary TiO₂ are consumed annually worldwide. When deposited as a thin film, its refractive index and colour make it an excellent reflective optical coating for and some , for example "mystic fire ". TiO₂ is also an effective in powder form, where it is employed as a pigment to provide whiteness and to products such as , , , papers, , foods, (i.e. pills and tablets) as well as most . Opacity is improved by optimal sizing of the titanium dioxide particles.

Used as a white , it has E number E171. Titanium dioxide is often used to whiten skim milk; this has been shown statistically to increase skim milk's palatability.

In and products, titanium dioxide is used both as a pigment and a . It is also used as a pigment and .

This pigment is used extensively in plastics and other applications for its UV resistant properties where it acts as a UV absorber, efficiently transforming destructive UV light energy into heat.

In titanium dioxide acts as an opacifier and seeds formation.

In almost every with a physical blocker, titanium dioxide is found because of its high refractive index, its strong UV light absorbing capabilities and its resistance to discolouration under light. This advantage enhances its stability and ability to protect the skin from ultraviolet light. Sunscreens designed for infants or people with sensitive skin are often based on titanium dioxide and/or , as these mineral UV blockers are less likely to cause skin irritation than chemical UV ingredients, such as .

Titanium oxide is also used as a .

As a photocatalyst

Titanium dioxide, particularly in the anatase form, is a under ultraviolet light. Recently it has been found that titanium dioxide, when spiked with nitrogen ions, or doped with metal oxide like tungsten trioxide, is also a photocatalyst under visible and UV light. The strong of the oxidizes water to create . It can also oxidize oxygen or organic materials directly. Titanium dioxide is thus added to paints, cements, windows, tiles, or other products for sterilizing, deodorizing and anti-fouling properties and is also used as a . It is also used in the , a type of chemical solar cell.

The photocatalytic properties of titanium dioxide were discovered by in 1972 . The process on the surface of the titanium dioxide was called the Honda-Fujishima effect .

Titanium dioxide has potential for use in energy production: as a photocatalyst, it can

1. carry out ; i.e., break water into hydrogen and oxygen. Were the hydrogen collected, it could be used as a fuel. The efficiency of this process can be greatly improved by doping the oxide with carbon, as described in "Carbon-doped titanium dioxide is an effective photocatalyst" .
2. produce electricity when in nanoparticle form. Research suggests that by using these nanoparticles to form the pixels of a screen, they generate electricity when transparent and under the influence of light. If subjected to electricity on the other hand, the nanoparticles blacken, forming the basic characteristics of a LCD screen. According to creator Zoran Radivojevic, Nokia has already built a functional 200-by-200-pixel monochromatic screen which is energetically self-sufficient.

In 1995 the Research Institute of discovered the phenomenon for glass coated with titanium dioxide and exposed to sun light. A discovery by Professor Fujishima and his group This resulted in the development of and coatings.

TiO₂ incorporated into outdoor building materials, such as paving stones in or paints, can substantially reduce concentrations of airborne pollutants such as and .

A photocatalytic cement that uses titanium dioxide as a primary component was included in 's Top 50 Inventions of 2008 .

For wastewater remediation

TiO₂ offers great potential as an industrial technology for detoxification or of due to several factors.

1. The process occurs under ambient conditions very slowly, direct UV light exposure increases the rate of reaction.
2. The formation of photocyclized intermediate products, unlike direct techniques, is avoided.
3. Oxidation of the substrates to CO₂ is complete.
4. The photocatalyst is inexpensive and has a high turnover.
5. TiO₂ can be supported on suitable reactor substrates.

Other applications

It is also used in resistance-type (a type of ).

Titanium dioxide is what allows between an and .

Titanium dioxide in solution or suspension can be used to cleave protein that contains the amino acid at the site where proline is present. This breakthrough in cost-effective protein splitting took place at in 2006.

Titanium dioxide on silica is being developed as a form of odor control in . The purchased photocatalyst is vastly cheaper than the purchased silica beads, per usage, and prolongs their effective odor-eliminating life substantially.

Titanium dioxide is also used as a material in the , a new electronic .

It can be employed for solar energy conversion based on , , or sensitized TiO2 using as solid .

It has also been recently incorporated as a photocatalyst into dental bleaching products. It allows the use of decreased concentrations of hydrogen peroxide in the bleaching agent, thus claimed to achieve similar bleaching effects with less side effects (e.g.:transient sensitivity, change in tooth surface topography, etc ...)

It is also used by film and television companies as a substitute for when filming scenes which require a setting.

Historical uses

The , the map of America ("") that was allegedly drawn during mid-15th century based on data from the , has been declared a forgery on the basis that its ink contains traces of the TiO₂-form anatase; TiO₂ was not synthetically produced before the 1920s. In 1992, a counter-claim was made that the compound can be formed from ancient ink.^[]

Titanium dioxide white paint was used to paint the rocket, which is so far the only rocket that has sent astronauts to the moon. In 2002, a spectral analysis of , a celestial object, showed that it had titanium dioxide on it, giving evidence it may be a Saturn V .

See also

• , a building material incorporating TiO₂.

Toxicology

Titanium dioxide dust, when inhaled, has recently been classified by the International Agency for Research on Cancer (IARC) as an IARC Group 2B carcinogen possibly carcinogenic to humans. Titanium dioxide accounts for 70% of the total production volume of pigments worldwide. It is widely used to provide whiteness and opacity to products such as paints, plastics, papers, inks, foods, and toothpastes. It is also used in cosmetic and skin care products, and it is present in almost every sunblock, where it helps protect the skin from ultraviolet light.

With such widespread use of titanium dioxide, it is important to understand that the IARC conclusions are based on very specific evidence. This evidence showed that high concentrations of pigment-grade (powdered) and ultrafine titanium dioxide dust caused respiratory tract cancer in rats exposed by inhalation and intratracheal instillation. The series of biological events or steps that produce the rat lung cancers (e.g. particle deposition, impaired lung clearance, cell injury, fibrosis, mutations and ultimately cancer) have also been seen in people working in dusty environments. Therefore, the observations of cancer in animals were considered, by IARC, as relevant to people doing jobs with exposures to titanium dioxide dust. For example, titanium dioxide production workers may be exposed to high dust concentrations during packing, milling, site cleaning and maintenance, if there are insufficient dust control measures in place. However, it should be noted that the human studies conducted so far do not suggest an association between occupational exposure to titanium dioxide and an increased risk for cancer.

The Workplace Hazardous Materials Information System (WHMIS) is Canada's hazard communication standard. The WHMIS Controlled Products Regulations require that chemicals, listed in Group 1 or Group 2 in the IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, be classified under WHMIS Class D2A (carcinogenic). The classification decision on titanium dioxide has been published on the IARC website and in a summary article published in The Lancet.

Representatives from Health Canada (National Office of WHMIS) recently consulted with the Quebec CSST and CCOHS (the two main agencies providing WHMIS classifications to the public) regarding the implications of the IARC decision to the WHMIS classification of titanium dioxide. It was agreed that titanium dioxide does now meet the criteria for WHMIS D2A (carcinogen) based on the information released by IARC to date, and that it is not necessary to wait for release of the full monograph.

Manufacturers and suppliers of titanium dioxide are advised to review and update their material safety data sheets and product labels based on this new information as soon as possible. Employers should review their occupational hygiene programs to ensure that exposure to titanium dioxide dust is eliminated or reduced to the minimum possible. Workers should be educated concerning this potential newly recognized risk to their health and trained in proper work procedures.

References

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2. A natural shock-induced dense polymorph of rutile with α-PbO₂ structure in the suevite from the Ries crater in Germany, Ahmed El Goresy, Ming Chen, Philippe Gillet, Leonid Dubrovinsky, Günther Graup and Rajeev Ahuja, Earth and Planetary Science Letters, 192, 4, 2001, 485-495,
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External links

• International Chemical Safety Card 0338
• "Nano-Oxides, Inc. - Nano Powders, LEGIT information on Titanium Dioxide TiO₂" (PDF). www.nano-oxides.com. සම්ප්‍රවේශය November. {{}}: Check date values in: |accessdate= (); Unknown parameter |accessyear= ignored (|access-date= suggested) ()
• NIOSH Pocket Guide to Chemical Hazards
• "Fresh doubt over America map", bbc.co.uk, 2002
• Titanium Dioxide Classified as Possibly Carcinogenic to Humans, 2007 (if inhaled as a powder)
• A description of TiO₂ photocatalysis 2007-01-12 at the Wayback Machine
• Crystal structures of the three forms of TiO₂ 2009-01-31 at the Wayback Machine
• , 2006
• "A Concrete Step Toward Cleaner Air", Bruno Giussani, BusinessWeek.com, , 2006
• "Titanium Dioxide Classified as Possibly Carcinogenic to Humans", Canadian Centre for Occupational Health and Safety, August, 2006