TITANIUM DIOXIDE

Synonyms:
TITANIUM DIOXIDE  ; Dioxide DE TITANE  ; oxyde de titane (IV), TiO2; TiO2; cas 13463-67-7; Cas no:13463-67-7;  Titanium dioxide (rutile); titanium dioxide; TITANIUM DIOXIDE  ; Dioxide DE TITANE  ; OXYDE DE TİTANE (IV), TİO2; TİO2; CAS 13463-67-7; TITANIUM DIOXIDE  ; Dioxide DE TITANE  ; OXYDE DE TİTANE (IV), TİO2; TİO2; CAS 13463-67-7; CAS NO:13463-67-7;  TİTANİUM DİOXİDE (RUTİLE); TİTANİUM DİOXİDE; TİTANİUM DİOXIDE  ; DİOXYDE DE TİTANE  ; TITANIUM DIOXIDE  ; Dioxide DE TITANE   ; TİTANİUM DİOXIDE  ; DİOXYDE DE TİTANE   ; TİTANİUM DİOXİDE RUTİLE; Tıtanıum Dıoxıde  ; Dıoxyde De Tıtane  ; Oxyde De Titane (Iv), Tio2; Tio2; Cas 13463-67-7; Cas No:13463-67-7;  Titanium Dioxide (Rutile); Titanium Dioxide; Titanium Dioxıde  ; Dioxide De Titane  ; Tıtanıum Dıoxıde  ; Dıoxyde De Tıtane   ; Titanium Dioxıde  ; Dioxide De Titane   ; Titanium Dioxide Rutile; tıtanıum dıoxıde  ; dıoxyde de tıtane  ; oxyde de titane (ıv), tio2; tio2; cas 13463-67-7; cas no:13463-67-7;  titanium dioxide (rutile); titanium dioxide; titanium dioxıde  ; Dioxide de titane  ;Tıtanıum Dıoxıde  ; Dıoxyde De Tıtane   ; Titanium Dioxıde  ; Dioxide De Titane   ; Titanium Dioxide Rutile; tıtanıum dıoxıde  ; dıoxyde de tıtane  ; oxyde de titane (ıv), tio2; tio2; cas 13463-67-7; cas no:13463-67-7;  titanium dioxide (rutile); titanium dioxide; titanium dioxıde  ; Dioxide de titane  ; tıtanıum dıoxıde  ; dıoxyde de tıtane   ; titanium dioxıde  ; Dioxide de titane   ; titanium dioxide rutile; TiO2; TiO2; CAS NO:13463-67-7;  TİTANİUM DİOXİDE (RUTİLE); TİTANİUM DİOXİDE; TİTANİUM DİOXIDE  ; DİOXYDE DE TİTANE  ; TITANIUM DIOXIDE  ; Dioxide DE TITANE   ; TİTANİUM DİOXIDE  ; DİOXYDE DE TİTANE   ; TİTANİUM DİOXİDE RUTİLE; Tıtanıum Dıoxıde  ; Dıoxyde De Tıtane  ; Oxyde De Titane (Iv), Tio2; Tio2; Cas 13463-67-7; Cas No:13463-67-7;  Titanium Dioxide (Rutile); Titanium Dioxide; Titanium Dioxıde  ; Dioxide De Titane  ; Tıtanıum Dıoxıde  ; Dıoxyde De Tıtane   ; Titanium Dioxıde  ; Dioxide De Titane   ; Titanium Dioxide Rutile; tıtanıum dıoxıde  ; dıoxyde de tıtane  ; oxyde de titane (ıv), tio2; tio2; cas 13463-67-7; cas no:13463-67-7;  titanium dioxide (rutile); titanium dioxide; titanium dioxıde  ; Dioxide de titane  ; tıtanıum dıoxıde  ; dıoxyde de tıtane   ; titanium dioxıde  ; Dioxide de titane   ; titanium dioxide rutile; TiO2; TiO2 ; Titanyum dioksit anastaz  ; Titanium dioksit anastaz  ; Titanyum dioksyt anastaz  ; Titanyum dioksit ; di oxyde de titane  ; Dioxide de titane; Dioxide de titan  ; Di Oxyde de titane  ; tıtanıum dıoxıde  ; dıoxyde de tıtane   ; titanium dioxıde  ; Dioxide de titane   ; titanium dioxide rutile; TiO2; TiO2; CAS NO:13463-67-7;   Dıoxyde De Tıtane   ; Titanium Dioxıde  ; Dioxide De Titane   ; Titanium Dioxide Rutile; tıtanıum dıoxıde  ; dıoxyde de tıtane  ; oxyde de titane (ıv), tio2; tio2; cas 13463-67-7; cas no:13463-67-7;  titanium dioxide (rutile); titanium dioxide; titanium dioxıde  ; Dioxide de titane  ; tıtanıum dıoxıde  ; dıoxyde de tıtane   ; titanium dioxıde  ; Dioxide de titane   ; titanium dioxide rutile; TiO2; TiO2 ; Titanyum dioksit anastaz  ; Titanium dioksit anastaz  ; Titanyum dioksyt anastaz  ; Titanyum dioksit ; di oxyde de titane  ; Dioxide de titane; Dioxide de titan  ; Di Oxyde de titane  ; Dioxyde de titane; dioxyde de titan; Titanyum Dioksit; Titanium Dioksit; Titanyum Diyoksit

Titanium dioxide

Titanium dioxide
Titanium(IV) oxide
The unit cell of rutile
Names
IUPAC names
Titanium dioxide
Titanium(IV) oxide
Other names
Titania
Rutile
 
Brookite
Identifiers
CAS Number    
13463-67-7 ☑
3D model (JSmol)    
Interactive image
ChEBI    
CHEBI:32234 ☑
ChEMBL    
ChEMBL1201136 ☒
ChemSpider    
24256 ☑
ECHA InfoCard    100.033.327
E number    E171 (colours)
KEGG    
C13409 ☒
PubChem CID    
26042
RTECS number    
XR2775000
UNII    
15FIX9V2JP ☑
CompTox Dashboard (EPA)    
DTXSID3021352 
InChI[show]
SMILES[show]
Properties
Chemical formula    TiO
2
Molar mass    79.866 g/mol
Appearance    White solid
Odor    Odorless
Density    
4.23 g/cm3 (rutile)
3.78 g/cm3 ( )
Melting point    1,843 °C (3,349 °F; 2,116 K)
Boiling point    2,972 °C (5,382 °F; 3,245 K)
Solubility in water    Insoluble
Band gap    3.05 eV (rutile)[1]
Magnetic susceptibility (χ)    +5.9·10−6 cm3/mol
Refractive index (nD)    
2.488 ( )
2.583 (brookite)
2.609 (rutile)
Thermochemistry
Std molar
entropy (So298)    50 J·mol−1·K−1[2]
Std enthalpy of
formation (ΔfH⦵298)    −945 kJ·mol−1[2]
Hazards
Safety data sheet    ICSC 0338
EU classification (DSD) (outdated)    Not listed
NFPA 704 (fire diamond)    
NFPA 704 four-colored diamond
010
Flash point    Non-flammable
NIOSH (US health exposure limits):
PEL (Permissible)    TWA 15 mg/m3[3]
REL (Recommended)    Ca[3]
IDLH (Immediate danger)    Ca [5000 mg/m3][3]
Related compounds
Other cations    Zirconium dioxide
Hafnium dioxide
Related Titanium oxides    Titanium(II) oxide
Titanium(III) oxide
Titanium(III,IV) oxide
Related compounds    Titanic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
Titanium dioxide, also known as titanium(IV) oxide or titania /taɪˈteɪniə/, is the naturally occurring oxide of titanium, chemical formula TiO
2. When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891. Generally, it is sourced from ilmenite, rutile, and  . It has a wide range of applications, including paint, sunscreen, and food coloring. When used as a food coloring, it has E number E171. World production in 2014 exceeded 9 million tonnes.[4][5][6] It has been estimated that titanium dioxide is used in two-thirds of all pigments, and pigments based on the oxide have been valued at $13.2 billion.[7]

Occurrence
Titanium dioxide occurs in nature as the minerals rutile and  . Additionally two high-pressure forms are known minerals: a monoclinic baddeleyite-like form known as akaogiite, and the other is an orthorhombic α-PbO2-like form known as brookite, both of which can be found at the Ries crater in Bavaria.[8][9][10] It is mainly sourced from ilmenite ore. This is the most widespread form of titanium dioxide-bearing ore around the world. Rutile is the next most abundant and contains around 98% titanium dioxide in the ore. The metastable   and brookite phases convert irreversibly to the equilibrium rutile phase upon heating above temperatures in the range 600–800 °C (1,110–1,470 °F).[11]

Titanium dioxide has eight modifications – in addition to rutile,  , akaogiite, and brookite, three metastable phases can be produced synthetically (monoclinic, tetragonal, and orthorombic), and five high-pressure forms (α-PbO2-like, baddeleyite-like, cotunnite-like, orthorhombic OI, and cubic phases) also exist:

Form    Crystal system    Synthesis
Rutile    Tetragonal    
     Tetragonal    
Brookite    Orthorhombic    
TiO2(B)[12]    Monoclinic    Hydrolysis of K2Ti4O9 followed by heating
TiO2(H), hollandite-like form[13]    Tetragonal    Oxidation of the related potassium titanate bronze, K0.25TiO2
TiO2(R), ramsdellite-like form[14]    Orthorhombic    Oxidation of the related lithium titanate bronze Li0.5TiO2
TiO2(II)-(α-PbO2-like form)[15]    Orthorhombic    
Akaogiite (baddeleyite-like form, 7 coordinated Ti)[16]    Monoclinic    
TiO2 -OI[17]    Orthorhombic    
Cubic form[18]    Cubic    P > 40 GPa, T > 1600 °C
TiO2 -OII, cotunnite(PbCl2)-like[19]    Orthorhombic    P > 40 GPa, T > 700 °C
The cotunnite-type phase was claimed by L. Dubrovinsky and co-authors to be the hardest known oxide with the Vickers hardness of 38 GPa and the bulk modulus of 431 GPa (i.e. close to diamond's value of 446 GPa) at atmospheric pressure.[19] However, later studies came to different conclusions with much lower values for both the hardness (7–20 GPa, which makes it softer than common oxides like corundum Al2O3 and rutile TiO2)[20] and bulk modulus (~300 GPa).[21][22]

The oxides are commercially important ores of titanium. The metal is also be mined from other ores such as ilmenite or leucoxene, or one of the purest forms, rutile beach sand. Star sapphires and rubies get their asterism from rutile impurities present.[23]

Titanium dioxide (B) is found as a mineral in magmatic rocks and hydrothermal veins, as well as weathering rims on perovskite. TiO2 also forms lamellae in other minerals.[24]

Molten titanium dioxide has a local structure in which each Ti is coordinated to, on average, about 5 oxygen atoms.[25] This is distinct from the crystalline forms in which Ti coordinates to 6 oxygen atoms.

A ball-and-stick chemical model of an   crystal
Structure of  . Together with rutile and brookite, one of the three major polymorphs of TiO2.
Production

Evolution of the global production of titanium dioxide according to process
The production method depends on the feedstock. The most common mineral source is ilmenite. The abundant rutile mineral sand can also be purified with the chloride process or other processes. Ilmenite is converted into pigment grade titanium dioxide via either the sulfate process or the chloride process. Both sulfate and chloride processes produce the titanium dioxide pigment in the rutile crystal form, but the Sulfate Process can be adjusted to produce the   form.  , being softer, is used in fiber and paper applications. The Sulfate Process is run as a batch process; the Chloride Process is run as a continuous process.[26]

Plants using the Sulfate Process require ilmenite concentrate (45-60% TiO2) or pretreated feedstocks as suitable source of titanium.[27] In the sulfate process, ilmenite is treated with sulfuric acid to extract iron(II) sulfate pentahydrate. The resulting synthetic rutile is further processed according to the specifications of the end user, i.e. pigment grade or otherwise.[28] In another method for the production of synthetic rutile from ilmenite the Becher Process first oxidizes the ilmenite as a means to separate the iron component.

An alternative process, known as the chloride process converts ilmenite or other titanium sources to titanium tetrachloride via reaction with elemental chlorine, which is then purified by distillation, and reacted with oxygen to regenerate chlorine and produce the titanium dioxide. Titanium dioxide pigment can also be produced from higher titanium content feedstocks such as upgraded slag, rutile, and leucoxene via a chloride acid process.

The five largest TiO
2 pigment processors are in 2019 Chemours, Cristal Global, Venator, Kronos, and Tronox, which is the largest one.[29][30] Major paint and coating company end users for pigment grade titanium dioxide include Akzo Nobel, PPG Industries, Sherwin Williams, BASF, Kansai Paints and Valspar.[31] Global TiO
2 pigment demand for 2010 was 5.3 Mt with annual growth expected to be about 3-4%.[32]

Specialized methods
For specialty applications, TiO2 films are prepared by various specialized chemistries.[33] Sol-gel routes involve the hydrolysis of titanium alkoxides, such as titanium ethoxide:

Ti(OEt)4 + 2 H2O → TiO2 + 4 EtOH
This technology is suited for the preparation of films. A related approach that also relies on molecular precursors involves chemical vapor deposition. In this application, the alkoxide is volatilized and then decomposed on contact with a hot surface:

Ti(OEt)4 → TiO2 + 2 Et2O
Applications
The most important application areas are paints and varnishes as well as paper and plastics, which account for about 80% of the world's titanium dioxide consumption. Other pigment applications such as printing inks, fibers, rubber, cosmetic products, and food account for another 8%. The rest is used in other applications, for instance the production of technical pure titanium, glass and glass ceramics, electrical ceramics, metal patinas, catalysts, electric conductors, and chemical intermediates.[34]

Pigment
First mass-produced in 1916,[35] titanium dioxide is the most widely used white pigment because of its brightness and very high refractive index, in which it is surpassed only by a few other materials (see list of indices of refraction). Titanium dioxide crystal size is ideally around 220 nm (measured by electron microscope) to optimize the maximum reflection of visible light. The optical properties of the finished pigment are highly sensitive to purity. As little as a few parts per million (ppm) of certain metals (Cr, V, Cu, Fe, Nb) can disturb the crystal lattice so much that the effect can be detected in quality control.[36] Approximately 4.6 million tons of pigmentary TiO2 are used annually worldwide, and this number is expected to increase as use continues to rise.[37]

TiO2 is also an effective opacifier in powder form, where it is employed as a pigment to provide whiteness and opacity to products such as paints, coatings, plastics, papers, inks, foods, medicines (i.e. pills and tablets), and most toothpastes. In paint, it is often referred to offhandedly as "brilliant white", "the perfect white", "the whitest white", or other similar terms. Opacity is improved by optimal sizing of the titanium dioxide particles.

TiO2 has been flagged as possibly carcinogenic. In 2019, it was present in two thirds of toothpastes on the French market. Bruno Le Maire, a minister in the Edouard Philippe government, promised in March 2019 to remove it from that and other alimentary uses.[38]

Thin films
When deposited as a thin film, its refractive index and colour make it an excellent reflective optical coating for dielectric mirrors; it is also used in generating decorative thin films such as found in "mystic fire topaz".

Some grades of modified titanium based pigments as used in sparkly paints, plastics, finishes and cosmetics - these are man-made pigments whose particles have two or more layers of various oxides – often titanium dioxide, iron oxide or alumina – in order to have glittering, iridescent and or pearlescent effects similar to crushed mica or guanine-based products. In addition to these effects a limited colour change is possible in certain formulations depending on how and at which angle the finished product is illuminated and the thickness of the oxide layer in the pigment particle; one or more colours appear by reflection while the other tones appear due to interference of the transparent titanium dioxide layers.[39] In some products, the layer of titanium dioxide is grown in conjunction with iron oxide by calcination of titanium salts (sulfates, chlorates) around 800 °C[40] One example of a pearlescent pigment is Iriodin, based on mica coated with titanium dioxide or iron (III) oxide.[41]

The iridescent effect in these titanium oxide particles is unlike the opaque effect obtained with usual ground titanium oxide pigment obtained by mining, in which case only a certain diameter of the particle is considered and the effect is due only to scattering.

Sunscreen and UV blocking pigments
In cosmetic and skin care products, titanium dioxide is used as a pigment, sunscreen and a thickener. As a sunscreen, ultrafine TiO2 is used, which is notable in that combined with ultrafine zinc oxide, it is considered to be an effective sunscreen that is less harmful to coral reefs than sunscreens that include chemicals such as oxybenzone and octinoxate.

Nanosized titanium dioxide is found in the majority of physical sunscreens because of its strong UV light absorbing capabilities and its resistance to discolouration under ultraviolet light. This advantage enhances its stability and ability to protect the skin from ultraviolet light. Nano-scaled (particle size of 20–40 nm)[42] titanium dioxide particles are primarily used in sunscreen lotion because they scatter visible light much less than titanium dioxide pigments, and can give UV protection.[37] Sunscreens designed for infants or people with sensitive skin are often based on titanium dioxide and/or zinc oxide, as these mineral UV blockers are believed to cause less skin irritation than other UV absorbing chemicals. Nano-TiO2 blocks both UV-A and UV-B radiation, which is used in sunscreens and other cosmetic products. It is safe to use and it is better to environment than organic UV-absorbers.[43]

TiO
2 is used extensively in plastics and other applications as a white pigment or an opacifier and for its UV resistant properties where the powder disperses light – unlike organic UV absorbers – and reduces UV damage, due mostly to the particle's high refractive index.[44]

Other uses of titanium dioxide
In ceramic glazes, titanium dioxide acts as an opacifier and seeds crystal formation.

It is used as a tattoo pigment and in styptic pencils. Titanium dioxide is produced in varying particle sizes, oil and water dispersible, and in certain grades for the cosmetic industry.

Research
Photocatalyst
Nanosized titanium dioxide, particularly in the   form, exhibits photocatalytic activity under ultraviolet (UV) irradiation. This photoactivity is reportedly most pronounced at the {001} planes of  ,[45][46] although the {101} planes are thermodynamically more stable and thus more prominent in most synthesised and natural  ,[47] as evident by the often observed tetragonal dipyramidal growth habit. Interfaces between rutile and   are further considered to improve photocatalytic activity by facilitating charge carrier separation and as a result, biphasic titanium dioxide is often considered to possess enhanced functionality as a photocatalyst.[48] It has been reported that titanium dioxide, when doped with nitrogen ions or doped with metal oxide like tungsten trioxide, exhibits excitation also under visible light.[49] The strong oxidative potential of the positive holes oxidizes water to create hydroxyl radicals. It can also oxidize oxygen or organic materials directly. Hence, in addition to its use as a pigment, titanium dioxide can be added to paints, cements, windows, tiles, or other products for its sterilizing, deodorizing, and anti-fouling properties, and is used as a hydrolysis catalyst. It is also used in dye-sensitized solar cells, which are a type of chemical solar cell (also known as a Graetzel cell).

The photocatalytic properties of nanosized titanium dioxide were discovered by Akira Fujishima in 1967[50] and published in 1972.[51] The process on the surface of the titanium dioxide was called the Honda-Fujishima effect (ja:本多-藤嶋効果).[50] Titanium dioxide, in thin film and nanoparticle form has potential for use in energy production: as a photocatalyst, it can break water into hydrogen and oxygen. With 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.[52] Further efficiency and durability has been obtained by introducing disorder to the lattice structure of the surface layer of titanium dioxide nanocrystals, permitting infrared absorption.[53] Visible-light-active nanosized   and rutile has been developed for photocatalytic applications.[54][55]

In 1995 Fujishima and his group discovered the superhydrophilicity phenomenon for titanium dioxide coated glass exposed to sun light.[50] This resulted in the development of self-cleaning glass and anti-fogging coatings.

Nanosized TiO2 incorporated into outdoor building materials, such as paving stones in noxer blocks[56] or paints, can substantially reduce concentrations of airborne pollutants such as volatile organic compounds and nitrogen oxides.[57] A cement that uses titanium dioxide as a photocatalytic component, produced by Italcementi Group, was included in Time Magazine's Top 50 Inventions of 2008.[58]

Attempts have been made to photocatalytically mineralize pollutants (to convert into CO2 and H2O) in waste water.[59] TiO2 offers great potential as an industrial technology for detoxification or remediation of wastewater due to several factors:[60]

The process uses natural oxygen and sunlight and thus occurs under ambient conditions; it is wavelength selective and is accelerated by UV light.
The photocatalyst is inexpensive, readily available, non-toxic, chemically and mechanically stable, and has a high turnover.
The formation of photocyclized intermediate products, unlike direct photolysis techniques, is avoided.
Oxidation of the substrates to CO2 is complete.
TiO2 can be supported as thin films on suitable reactor substrates, which can be readily separated from treated water.[61]
The photocatalytic destruction of organic matter is also exploited in photocatalytic antimicrobial coatings,[62] which are typically thin films applied to furniture in hospitals and other surfaces susceptible to be contaminated with bacteria, fungi, and viruses.

Hydroxyl radical formation
Although nanosized   TiO2 does not absorb visible light, it does strongly absorb ultraviolet (UV) radiation (hv), leading to the formation of hydroxyl radicals.[63] This occurs when photo-induced valence bond holes (h+vb) are trapped at the surface of TiO2 leading to the formation of trapped holes (h+tr) that cannot oxidize water.[64]

TiO2 + hv → e− + h+vb
h+vb → h+tr
O2 + e− → O2•−
O2•− + O2•−+ 2 H+ → H2O2 + O2
O2•− + h+vb → O2
O2•− + h+tr → O2
 OH− + h+vb → HO•
e− + h+tr → recombination
Note: Wavelength (λ)= 387 nm[64] This reaction has been found to mineralize and decompose undesirable compounds in the environment, specifically the air and in wastewater.[64]

Synthetic single crystals of TiO2, ca. 2–3 mm in size, cut from a larger plate.
Nanotubes

Titanium oxide nanotubes, SEM image

Nanotubes of titanium dioxide (TiO2-Nt) obtained by electrochemical synthesis. The SEM image shows an array of vertical self-ordered TiO2-Nt with closed bottom ends of tubes.
  can be converted into inorganic nanotubes and nanowires.[65] Hollow TiO2 nanofibers can be also prepared by coating carbon nanofibers by first applying titanium butoxide.[66]

SEM (top) and TEM (bottom) images of chiral TiO2 nanofibers.[66]
Health and safety
Titanium dioxide is incompatible with strong reducing agents and strong acids.[67] Violent or incandescent reactions occur with molten metals that are electropositive, e.g. aluminium, calcium, magnesium, potassium, sodium, zinc and lithium.[68]

Many sunscreens use nanoparticle titanium dioxide (along with nanoparticle zinc oxide) which, despite reports of potential health risks,[69] is not actually absorbed through the skin.[70] Other effects of titanium dioxide nanoparticles on human health are not well understood.[71]

Titanium dioxide dust, when inhaled, has been classified by the International Agency for Research on Cancer (IARC) as an IARC Group 2B carcinogen, meaning it is possibly carcinogenic to humans.[72][73] The findings of the IARC are based on the discovery that high concentrations of pigment-grade (powdered) and ultrafine titanium dioxide dust caused respiratory tract cancer in rats exposed by inhalation and intratracheal instillation.[74] 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, the human studies conducted so far do not suggest an association between occupational exposure to titanium dioxide and an increased risk for cancer. The safety of the use of nano-particle sized titanium dioxide, which can penetrate the body and reach internal organs, has been criticized.[75] Studies have also found that titanium dioxide nanoparticles cause inflammatory response and genetic damage in mice.[76][77] The mechanism by which TiO
2 may cause cancer is unclear. Molecular research suggests that cell cytotoxicity due to TiO
2 results from the interaction between TiO
2 nanoparticles and the lysosomal compartment, independently of the known apoptotic signalling pathways.[78]

The body of research regarding the carcinogenicity of different particle sizes of titanium dioxide has led the US National Institute for Occupational Safety and Health to recommend two separate exposure limits. NIOSH recommends that fine TiO
2 particles be set at an exposure limit of 2.4 mg/m3, while ultrafine TiO
2 be set at an exposure limit of 0.3 mg/m3, as time-weighted average concentrations up to 10 hours a day for a 40-hour work week.[79] These recommendations reflect the findings in the research literature that show smaller titanium dioxide particles are more likely to pose carcinogenic risk than the larger titanium dioxide particles.

There is some evidence the rare disease yellow nail syndrome may be caused by titanium, either implanted for medical reasons or through eating various foods containing titanium dioxide.[80]

Companies such as Mars and Dunkin' Donuts dropped titanium dioxide from their merchandise in 2015 after public pressure.[81] However, Andrew Maynard, director of Risk Science Center at the University of Michigan, downplayed the supposed danger from use of titanium dioxide in food. He says that the titanium dioxide used by Dunkin' Brands and many other food producers is not a new material, and it is not a nanomaterial either. Nanoparticles are typically smaller than 100 nanometres in diameter, yet most of the particles in food grade titanium dioxide are much larger.[82] Still, size distribution analyses showed that batches of food-grade TiO₂ always comprise a nano-sized fraction as inevitable byproduct of the manufacturing processes.[83]

Environmental waste introduction
Titanium dioxide (TiO₂) is mostly introduced into the environment as nanoparticles via wastewater treatment plants.[84] Cosmetic pigments including titanium dioxide enter the wastewater when the product is washed off into sinks after cosmetic use. Once in the sewage treatment plants, pigments separate into sewage sludge which can then be released into the soil when injected into the soil or distributed on its surface. 99% of these nanoparticles wind up on land rather than in aquatic environments due to their retention in sewage sludge.[84] In the environment, titanium dioxide nanoparticles have low to negligible solubility and have been shown to be stable once particle aggregates are formed in soil and water surroundings.[84] In the process of dissolution, water-soluble ions typically dissociate from the nanoparticle into solution when thermodynamically unstable. TiO2 dissolution increases when there are higher levels of dissolved organic matter and clay in the soil. However, aggregation is promoted by pH at the isoelectric point of TiO2 (pH= 5.8) which renders it neutral and solution ion concentrations above 4.5 mM.[85][86]

National bans on titanium dioxide as a food additive
In 2019, France banned the use of titanium dioxide in food from 2020 on.[87]

Trivia
The exterior of the Saturn V rocket was painted with titanium dioxide; this later allowed astronomers to determine that J002E3 was the S-IVB stage from Apollo 12 and not an asteroid.[88]

See also
Delustrant
Dye-sensitized solar cell
List of inorganic pigments
Noxer blocks, TiO2-coated pavers that remove NOx pollutants from the air
Suboxide
Surface properties of transition metal oxides
Titanium dioxide nanoparticle

Titanium Dioxide
Titanium, the ninth most common element in the Earth’s crust, is a metal commonly found in plants and animals. Titanium naturally interacts with oxygen to form titanium oxides, commonly found in ores, indigenous dusts, sands and soils.

What is Titanium Dioxide?
Many people are familiar with titanium dioxide as an active ingredient in sunscreen. Titanium dioxide works as a UV filtering ingredient in sunscreen – it helps protect a person’s skin by blocking absorption of the sun’s ultraviolet light that can cause sunburn and is also linked to skin cancer. Learn more about titanium dioxide and sunscreen.

Uses & Benefits
Pure titanium dioxide is a fine, white powder that provides a bright, white pigment. Titanium dioxide has been used for a century in a range of industrial and consumer products, including paints, coatings, adhesives, paper, plastics and rubber, printing inks, coated fabrics and textiles, as well as ceramics, floor coverings, roofing materials, cosmetics, toothpaste, soap, water treatment agents, pharmaceuticals, food colorants, automotive products, sunscreen and catalysts.

Titanium dioxide is produced in two main forms. The primary form, comprising over 98 percent of total production, is pigment grade titanium dioxide. The pigmentary form makes use of titanium dioxide’s excellent light-scattering properties in applications that require white opacity and brightness. The other form in which titanium dioxide is produced is as an ultrafine (nanomaterial) product. This form is selected when different properties, such as transparency and maximum ultraviolet light absorption, are required, such as in cosmetic sunscreens.

Pigment-grade Titanium Dioxide

Pigment-grade titanium dioxide is used in a range of applications that require high opacity and brightness. In fact, most surfaces and items that are white and pastel, and even dark shades of color, contain titanium dioxide. Pigment-grate titanium dioxide is used in a range of applications, including:

Paints and Coatings: Titanium dioxide provides opacity and durability, while helping to ensure the longevity of the paint and protection of the painted surface.  
Plastics, Adhesives and Rubber: Titanium dioxide can help minimize the brittleness, fading and cracking that can occur in plastics and other materials as a result of light exposure.
Cosmetics: Pigment-grade titanium dioxide is use in some cosmetics to aid in hiding blemishes and brightening the skin. Titanium dioxide allows for the use of thinner coatings of make-up material for the same desired effect.
Paper: Titanium dioxide is used to coat paper, making it whiter, brighter and more opaque.
Food Contact Materials and Ingredients: The opacity to visible and ultraviolet light offered by titanium dioxide protects food, beverages, supplements and pharmaceuticals from premature degradation, enhancing the longevity of the product. Specific classes of high purity pigment-grade titanium dioxide are also used in drug tablets, capsule coatings and as a decorative aid in some foods.
 

Ultrafine-grade, or Nanoscale Titanium Dioxide

Ultrafine-grades of titanium dioxide are most commonly used in the following specialty applications:  

Sunscreen: Nanoscale titanium dioxide becomes transparent to visible light while serving as an efficient UV light absorber. Because the particle size is so small, nano-titanium dioxide does not reflect visible light, but does absorb UV light, enabling a transparent barrier that protects the skin from the sun’s harmful rays. According to the Skin Cancer Foundation, using sunscreens containing titanium dioxide can help prevent the occurrence of skin cancer.
Catalysts: Nanoscale titanium dioxide is used as a support material for catalyst applications. Major uses include in the automotive industry to remove harmful exhaust gas emissions and in power stations to remove nitrous oxides.
Questions about sunscreen safety? Use this guide on chemical ingredients used in sunscreen.

Uses & BenefitsSafety Information
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Safety Information
The U.S. Food and Drug Administration (FDA) has assessed the safety of titanium dioxide pigment as a color additive in food, drug and cosmetic applications. FDA had issued guidance clarifying the safe use of titanium dioxide pigment as a food colorant, and has stated that titanium dioxide may be safely used in cosmetics, including cosmetics intended for use around the eye. FDA also regulates the safety and effectiveness of sunscreens and their ingredients, including nanoscale titanium dioxide.

Get answers to frequently asked questions about sunscreen safety.

Workers at titanium dioxide manufacturing plants and downstream value-chain manufacturing plants where titanium dioxide is used can be exposed to titanium dioxide dust. The U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) has established a Permissible Exposure Limit (PEL) for titanium dioxide total dust and requires employers to control workplace exposure below that PEL.

Consumer exposure to titanium dioxide dust is presumed to be extremely low, because titanium dioxide is typically fully incorporated into the end product in which it is used

Is titanium dioxide safe?
The U.S. Food and Drug Administration (FDA) has assessed the safety of titanium dioxide pigment as a color additive in food, drug and cosmetic applications, and as an ingredient in sunscreen products. FDA has also issued guidance clarifying the safe use of titanium dioxide pigment as a food colorant, and has stated that titanium dioxide may be safely used in cosmetics, including cosmetics intended for use around the eye.

What is titanium dioxide used in sunscreen?
Titanium dioxide is included in FDA’s list of acceptable active ingredients in sunscreen products. According to FDA, active ingredients in sunscreen such as titanium dioxide protect your skin from the sun’s harmful UV rays. More questions about sunscreen safety? Use our safety resource on chemical ingredients used in sunscreen.

Are there any health concerns associated with exposure to titanium dioxide?
The International Agency for Research on Cancer (IARC) has classified titanium dioxide as “possibly carcinogenic to humans,” based on studies that showed increased lung tumors in rats associated with titanium dioxide inhalation. However, extensive studies on titanium dioxide industry workers do not suggest an association between occupational exposure to titanium dioxide and an increased risk for cancer in humans.

What are the differences between pigment-grade titanium dioxide and titanium dioxide nanomaterials?
Pigment-grade titanium dioxide is manufactured at a specific particle size distribution to optimize the scattering of visible light and enhance surface opacity. Titanium dioxide is produced primarily in the pigmentary form (over 98 percent of total production), which makes use of its excellent light-scattering properties for a range of applications that require opacity and brightness.

Titanium dioxide nanomaterials are purposefully made in a much smaller particle size distribution than pigmentary particles and are transparent and more effective as UV absorbers or photocatalysts. The transparency and UV absorbance allow for effective use as a protective ingredient for sunscreens.

Why is titanium dioxide used in toothpaste?
Titanium dioxide is often used to impart whiteness to food products, cosmetics and personal care items, like toothpaste. The U.S. Food and Drug Administration (FDA) has assessed the safety of titanium dioxide as a color additive and has issued regulations approving the ingredient for these purposes.