Titanium dioxide



Titanium dioxide
IUPAC name Titanium dioxide
Titanium(IV) oxide
Other names Titania
Brookite
Identifiers
CAS number 13463-67-7
RTECS number XR2775000
Properties
Molecular formula O2
Molar mass 79.87 g/mol
Appearance White solid
Density 4.23 g/cm3
Melting point

1870 °C (3398 °F)

Boiling point

2972 °C (5381.6 °F)

Solubility in other solvents Insoluble
Thermochemistry
Std enthalpy of
formation ΔfHo298 		−944 mol
Hazards
EU classification not listed
NFPA 704
0
1
0
 
Flash point non-flammable
Related Compounds
Other cations Titanium(II) oxide
Titanium(III) oxide
Titanium(III,IV) oxide
Zirconium dioxide
Hafnium dioxide
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring food colouring.

Natural occurrence

Titanium dioxide occurs in four forms:

  • rutile, a tetragonal mineral usually of prismatic habit, often twinned;
  • anatase or octahedrite, a tetragonal mineral of dipyramidal habit;
  • orthorhombic mineral. Both anatase and brookite are relatively rare minerals;
  • monoclinic mineral.

Titanium dioxide occurrences in nature are never pure; it is found with contaminant metals such as asterism from rutile impurities present in them.[1]

Production

Crude titanium dioxide is purified via oxygen to give pure titanium dioxide.[2]

Another widely used process utilizes sulfuric acid. The by-product iron(II) sulfate is crystallized and filtered-off to yield only the titanium salt in the digestion solution, which is processed further to give pure titanium dioxide.

Applications

Titanium dioxide is the most widely used white pigment because of its brightness and very high E number E171. In cosmetic and skin care products, titanium dioxide is used both as a pigment and a thickener. It is also used as a tattoo pigment and styptic pencils.

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 ceramic glazes titanium dioxide acts as an opacifier and seeds avobenzone.

Titanium oxide is also used as a semiconductor.[3]

As a photocatalyst

Titanium dioxide, particularly in the anatase form, is a catalyst. It is also used in the Graetzel cell, a type of chemical solar cell.

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

  1. carry out hydrolysis; 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". [4]
  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.

As TiO2 is exposed to UV light, it becomes increasingly hydrophilic; thus, it can be used for anti-fogging coatings or self-cleaning windows. TiO2 incorporated into outdoor building materials, such as paving stones in volatile organic compounds and nitrogen oxides.

For wastewater remediation

TiO2 offers great potential as an industrial technology for detoxification or wastewater 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 photolysis 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 lambda probes (a type of oxygen sensor).

Titanium dioxide is what allows osseointegration between an artificial medical implant and bone.

Titanium dioxide in solution or suspension can be used to cleave proline at the site where proline is present. This breakthrough in cost-effective protein splitting took place at ASU in 2006.[5]

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

The Pilkington Activ glass has a special nano-scale, extremely thin hydrophilic coating of microcrystalline titanium oxide which catalyses the break-down of organic surface contamination by ultraviolet light from the sun. [6]

Historical uses

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

Titanium dioxide white paint was used to paint the Saturn V rocket, which is so far the only rocket that has sent astronauts to the moon. In 2002, a spectral analysis of J002E3, a celestial object, showed that it had titanium dioxide on it, giving evidence it may be a Saturn V S-IVB.

See also

  • Noxer, a building material incorporating TiO2.

References

  1. ^ Emsley, John (2001). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford: Oxford University Press, pp. 451 – 53. ISBN 0-19-850341-5. 
  2. ^ Titanium Dioxide Manufacturing Processes. Millennium Inorganic Chemicals. Retrieved on 2007-09-05.
  3. ^ M. D. Earle (1942). "The Electrical Conductivity of Titanium Dioxide". Physical Review 61 (1-2): 56.
  4. ^ (Document Unavilable)
  5. ^ B. J. Jones, M. J. Vergne, D. M. Bunk, L. E. Locascio and M. A. Hayes (2007). "Cleavage of Peptides and Proteins Using Light-Generated Radicals from Titanium Dioxide". Anal. Chem. 79 (4): 1327-1332. doi:10.1021/ac0613737.
  6. ^ Eco glass cleans itself with Sun
 
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