Wikipedia

Titanium dioxide

Titanium dioxide,also known astitanium(IV) oxideortitania/taɪˈteɪniə/,is theinorganic compoundderived fromtitaniumwith the chemical formulaTiO
2.When used as apigment,it is calledtitanium white,Pigment White 6(PW6), orCI 77891.[4]It is a white solid that is insoluble in water, although mineral forms can appear black. As a pigment, it has a wide range of applications, includingpaint,sunscreen,andfood coloring.When used as a food coloring, it hasE numberE171. World production in 2014 exceeded 9 million tonnes.[5][6][7]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 a price of $13.2 billion.[8]

Titanium dioxide
Titanium(IV) oxide
Unit cellof titanium dioxide (rutile form)
TitaniumOxygen
The unit cell of rutile
Names
IUPAC names
Titanium dioxide
Titanium(IV) oxide
Other names
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.033.327Edit this at Wikidata
E number E171(colours)
KEGG
RTECS number
  • XR2775000
UNII
  • InChI=1S/2O.TicheckY
    Key: GWEVSGVZZGPLCZ-UHFFFAOYSA-NcheckY
  • InChI=1/2O.Ti/rO2Ti/c1-3-2
    Key: GWEVSGVZZGPLCZ-TYTSCOISAW
  • O=[Ti]=O
Properties
TiO
2
Molar mass 79.866 g/mol
Appearance White solid
Odor Odorless
Density
  • 4.23 g/cm3(rutile)
  • 3.78 g/cm3(anatase)
Melting point 1,843 °C (3,349 °F; 2,116 K)
Boiling point 2,972 °C (5,382 °F; 3,245 K)
Insoluble
Band gap 3.21eV (anatase)[1]

3.15eV (rutile)[1]

+5.9·10−6cm3/mol
  • 2.488 (anatase)
  • 2.583 (brookite)
  • 2.609 (rutile)
Thermochemistry
50 J·mol−1·K−1[2]
−945 kJ·mol−1[2]
Hazards
NFPA 704(fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
0
0
Flash point not flammable
NIOSH(US health exposure limits):
PEL(Permissible)
 TWA 15mg/m3[3]
REL(Recommended)
 Ca[3]
IDLH(Immediate danger)
 Ca [5000mg/m3][3]
Safety data sheet(SDS) ICSC 0338
Related compounds
Othercations
 Zirconium dioxide
Hafnium dioxide
Titanium(II) oxide
Titanium(III) oxide
Titanium(III,IV) oxide
Related compounds
 Titanic acid
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).

Structure

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In all three of its main dioxides,titaniumexhibitsoctahedral geometry,being bonded to six oxide anions. The oxides in turn are bonded to three Ti centers. The overall crystal structures ofrutileandanataseare tetragonal in symmetry whereasbrookiteis orthorhombic. The oxygen substructures are all slight distortions ofclose packing:in rutile, the oxide anions are arranged in distorted hexagonal close-packing, whereas they are close to cubic close-packing in anatase and to "double hexagonal close-packing" for brookite. Therutile structureis widespread for other metal dioxides and difluorides, e.g. RuO2and ZnF2.

Molten titanium dioxide has a local structure in which each Ti is coordinated to, on average, about 5 oxygen atoms.[9]This is distinct from the crystalline forms in which Ti coordinates to 6 oxygen atoms.

Structure ofanatase.Together with rutile and brookite, one of the three majorpolymorphsof TiO2.

Synthetic and geologic occurrence

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Synthetic TiO2is mainly produced from the mineralilmenite.Rutile,andanatase,naturally occurring TiO2,occur widely also, e.g. rutile as a 'heavy mineral' in beach sand.Leucoxene,fine-grained anatase formed by natural alteration of ilmenite, is yet another ore.Star sapphiresandrubiesget theirasterismfrom oriented inclusions of rutile needles.[10]

Mineralogy and uncommon polymorphs

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Titanium dioxide occurs in nature as the mineralsrutileandanatase.Additionally two high-pressure forms are known minerals: amonoclinicbaddeleyite-like form known asakaogiite,and the other has a slight monoclinic distortion of theorthorhombicα-PbO2structure and is known as riesite. Both of which can be found at theRies craterinBavaria.[11][12][13]It is mainly sourced fromilmenite,which is the most widespread titanium dioxide-bearing ore around the world. Rutile is the next most abundant and contains around 98% titanium dioxide in the ore. The metastable anatase 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).[14]

Titanium dioxide has twelve known polymorphs – in addition to rutile, anatase, brookite, akaogiite and riesite, three metastable phases can be produced synthetically (monoclinic,tetragonal,and orthorhombic ramsdellite-like), and four high-pressure forms (α-PbO2-like,cotunnite-like, orthorhombic OI, and cubic phases) also exist:

Form Crystal system Synthesis
Rutile Tetragonal
Anatase Tetragonal
Brookite Orthorhombic
TiO2(B)[15] Monoclinic Hydrolysis of K2Ti4O9followed by heating
TiO2(H),hollandite-like form[16] Tetragonal Oxidation of the related potassium titanate bronze, K0.25TiO2
TiO2(R),ramsdellite-like form[17] Orthorhombic Oxidation of the related lithium titanate bronze Li0.5TiO2
TiO2(II)-(α-PbO2-like form)[18] Orthorhombic
Akaogiite(baddeleyite-like form, 7 coordinated Ti)[19] Monoclinic
TiO2-OI[20] Orthorhombic
Cubicform[21] Cubic P > 40 GPa, T > 1600 °C
TiO2-OII,cotunnite(PbCl2)-like[22] Orthorhombic P > 40 GPa, T > 700 °C

Thecotunnite-type phase was claimed to be the hardest known oxide with theVickers hardnessof 38 GPa and thebulk modulusof 431 GPa (i.e. close to diamond's value of 446 GPa) at atmospheric pressure.[22]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 Al2O3and rutile TiO2)[23]and bulk modulus (~300 GPa).[24][25]

Titanium dioxide (B) is found as amineralin magmatic rocks and hydrothermal veins, as well as weathering rims onperovskite.TiO2also formslamellaein other minerals.[26]

Production

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Industrial key players in the production of titanium dioxide - 2022

The largestTiO
2pigment processors areChemours,Venator,Kronos[de],andTronox.[27][28]Major paint and coating company end users for pigment grade titanium dioxide includeAkzo Nobel,PPG Industries,Sherwin Williams,BASF,Kansai PaintsandValspar.[29]GlobalTiO
2pigment demand for 2010 was 5.3 Mt with annual growth expected to be about 3–4%.[30]

Evolution of the global production of titanium dioxide according to process

The production method depends on the feedstock. In addition to ores, other feedstocks include upgradedslag.Both the chloride process and the sulfate process (both described below) produce titanium dioxide pigment in the rutile crystal form, but the sulfate process can be adjusted to produce theanataseform. Anatase, being softer, is used in fiber and paper applications. The sulfate process is run as abatch process;the chloride process is run as acontinuous process.[31]

Chloride process

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Main article:Chloride process

Inchloride process,the ore is treated with chlorine and carbon to givetitanium tetrachloride,a volatile liquid that is further purified by distillation. The TiCl4 is treated withoxygento regenerate chlorine and produce the titanium dioxide.

Sulfate process

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In the sulfate process, ilmenite is treated withsulfuric acidto extractiron(II) sulfate pentahydrate.This process requires concentrated ilmenite (45–60% TiO2) or pretreated feedstocks as a suitable source of titanium.[32]The resulting synthetic rutile is further processed according to the specifications of the end user, i.e. pigment grade or otherwise.[33]

Examples of plants using the sulfate process are theSorel-Tracyplant ofQIT-Fer et Titaneand theEramet Titanium & Ironsmelter inTyssedalNorway.[34]

Becher process

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Main article:Becher process

TheBecher processis another method for the production of synthetic rutile from ilmenite. It first oxidizes the ilmenite as a means to separate the iron component.

Specialized methods

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For specialty applications, TiO2films are prepared by various specialized chemistries.[35]Sol-gel routes involve the hydrolysis of titaniumalkoxidessuch astitanium ethoxide:

Ti(OEt)4+ 2 H2O → TiO2+ 4 EtOH

A related approach that also relies on molecular precursors involveschemical vapor deposition.In this method, the alkoxide is volatilized and then decomposed on contact with a hot surface:

Ti(OEt)4→ TiO2+ 2 Et2O

Applications

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Pigment

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Main article:Titanium white

First mass-produced in 1916,[36]titanium dioxide is the most widely used white pigment because of its brightness and very highrefractive index,in which it is surpassed only by a few other materials (seelist 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. However,abnormal grain growthis often observed in titanium dioxide, particularly in its rutile phase.[37]The occurrence of abnormal grain growth brings about a deviation of a small number of crystallites from the mean crystal size and modifies the physical behaviour of TiO2.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.[38]Approximately 4.6 million tons of pigmentary TiO2are used annually worldwide, and this number is expected to increase as use continues to rise.[39]

TiO2is also an effectiveopacifierin powder form, where it is employed as a pigment to provide whiteness andopacityto products such aspaints,coatings,plastics,papers,inks,foods,supplements,medicines(i.e. pills and tablets), and mosttoothpastes;in 2019 it was present in two-thirds of toothpastes on the French market.[40]In food, it is commonly found in products like ice creams, chocolates, all types of candy, creamers, desserts, marshmallows, chewing gum, pastries, spreads, dressings, cakes, and many other foods.[41]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.

Thin films

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When deposited as athin film,its refractive index and colour make it an excellent reflective optical coating fordielectric 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 oxideoralumina– in order to have glittering,iridescentand orpearlescenteffects similar to crushedmicaorguanine-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.[42]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[43]One example of a pearlescent pigment is Iriodin, based on mica coated with titanium dioxide or iron (III) oxide.[44]

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

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Incosmeticandskin careproducts, titanium dioxide is used as a pigment, sunscreen and athickener.As a sunscreen, ultrafine TiO2is used, which is notable in that combined withultrafine zinc oxide,it is considered to be an effective sunscreen that lowers the incidence ofsun burnsand minimizes the prematurephotoaging,photocarcinogenesisandimmunosuppressionassociated with long term excess sun exposure.[45]Sometimes these UV blockers are combined with iron oxide pigments in sunscreen to increase visible light protection.[46]

Titanium dioxide and zinc oxide are generally considered to be less harmful tocoral reefsthan sunscreens that include chemicals such asoxybenzone,octocryleneandoctinoxate.[47]

Nanosized titanium dioxide is found in the majority of physicalsunscreensbecause of its strong UV light absorbing capabilities and its resistance to discolouration underultravioletlight. This advantage enhances its stability and ability to protect the skin from ultraviolet light. Nano-scaled (particle size of 20–40 nm)[48]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.[39]Sunscreens designed for infants or people withsensitive skinare often based on titanium dioxide and/orzinc oxide,as these mineral UV blockers are believed to cause less skin irritation than other UV absorbing chemicals. Nano-TiO2,which blocks both UV-A and UV-B radiation, is used in sunscreens and other cosmetic products.

The EU Scientific Committee on Consumer Safety considered nano sized titanium dioxide to be safe for skin applications, in concentrations of up to 25 percent based on animal testing.[49]The risk assessment of different titanium dioxide nanomaterials in sunscreen is currently evolving since nano-sized TiO2is different from the well-known micronized form.[50]The rutile form is generally used in cosmetic and sunscreen products due to it not possessing any observed ability to damage the skin under normal conditions[51]and having a higherUV absorption.[52]In 2016 Scientific Committee on Consumer Safety (SCCS) tests concluded that the use of nano titanium dioxide (95–100% rutile, ≦5% anatase) as a UV filter can be considered to not pose any risk of adverse effects in humans post-application on healthy skin,[53]except in the case the application method would lead to substantial risk of inhalation (ie; powder or spray formulations). This safety opinion applied to nano TiO2in concentrations of up to 25%.[54]

Initial studies indicated that nano-TiO2particles could penetrate the skin, causing concern over its use. These studies were later refuted, when it was discovered that the testing methodology couldn't differentiate between penetrated particles and particles simply trapped in hair follicles and that having a diseased or physically damaged dermis could be the true cause of insufficient barrier protection.[50]

SCCS research found that when nanoparticles had certain photostable coatings (e.g.,alumina,silica,cetyl phosphate,triethoxycaprylylsilane,manganese dioxide), the photocatalytic activity was attenuated and no notable skin penetration was observed; the sunscreen in this research was applied at amounts of 10 mg/cm2 for exposure periods of 24 hours.[54]Coating TiO2with alumina, silica,zirconor variouspolymerscan minimizeavobenzonedegradation[55]and enhance UV absorption by adding an additional light diffraction mechanism.[52]

TiO
2is 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.[56]

Other uses of titanium dioxide

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Inceramic glazes,titanium dioxide acts as an opacifier and seedscrystalformation.

It is used as atattoopigment and instyptic pencils.Titanium dioxide is produced in varying particle sizes which are both oil and water dispersible, and in certain grades for the cosmetic industry. It is also a common ingredient in toothpaste.

The exterior of theSaturn Vrocket was painted with titanium dioxide; this later allowed astronomers to determine thatJ002E3was likely theS-IVBstage fromApollo 12and not anasteroid.[57]

Research

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Patenting activities

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Relevant patent families describing titanium dioxide production from ilmenite, 2002–2021.
Academic and public institutions having significant patent activity in titanium dioxide production. 2022

Between 2002 and 2022, there were 459patent familiesthat describe the production of titanium dioxide fromilmenite.The majority of these patents describe pre-treatment processes, such as using smelting and magnetic separation to increase titanium concentration in low-grade ores, leading to titanium concentrates or slags. Other patents describe processes to obtain titanium dioxide, either by a direct hydrometallurgical process or through the main industrial production processes, thesulfate processand thechloride process.[58]The sulfate process represents 40% of the world’s titanium dioxide production and is protected in 23% of patent families. The chloride process is only mentioned in 8% of patent families, although it provides 60% of the worldwide industrial production of titanium dioxide.[58]

Key contributors to patents on the production of titanium dioxide are companies from China, Australia and the United States, reflecting the major contribution of these countries to industrial production. Chinese companiesPangangandLomon BillionsGroups hold major patent portfolios.[58]

Photocatalyst

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Nanosized titanium dioxide, particularly in the anatase form, exhibitsphotocatalytic activityunder ultraviolet (UV) irradiation. This photoactivity is reportedly most pronounced at the {001} planes of anatase,[59][60]although the {101} planes are thermodynamically more stable and thus more prominent in most synthesised and natural anatase,[61]as evident by the often observed tetragonal dipyramidalgrowth habit.Interfaces between rutile and anatase 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.[62]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.[63]The strongoxidative potentialof thepositive holesoxidizeswaterto createhydroxyl 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 ahydrolysiscatalyst.It is also used indye-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 byAkira Fujishimain 1967[64]and published in 1972.[65]The process on the surface of the titanium dioxide was called theHonda-Fujishima effect[ja].[64]Inthin filmandnanoparticleform, titanium dioxide has the 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.[66]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.[67]Visible-light-active nanosized anatase and rutile has been developed for photocatalytic applications.[68][69]

In 1995 Fujishima and his group discovered thesuperhydrophilicityphenomenon for titanium dioxide coated glass exposed to sun light.[64]This resulted in the development ofself-cleaning glassandanti-foggingcoatings.

Nanosized TiO2incorporated into outdoor building materials, such as paving stones innoxer blocks[70]or paints, could reduce concentrations of airborne pollutants such asvolatile organic compoundsandnitrogen oxides.[71]A TiO2-containing cement has been produced.[72]

Using TiO2as a photocatalyst, attempts have been made to mineralize pollutants (to convert into CO2and H2O) in waste water.[73][74][75]The photocatalytic destruction of organic matter could also be exploited in coatings with antimicrobial applications.[76]

Hydroxyl radical formation

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Although nanosized anatase TiO2does not absorb visible light, it does strongly absorbultraviolet (UV) radiation(hv), leading to the formation of hydroxyl radicals.[77]This occurs when photo-induced valence bond holes (h+vb) are trapped at the surface of TiO2leading to the formation of trapped holes (h+tr) that cannot oxidize water.[78]

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[78]This reaction has been found to mineralize and decompose undesirable compounds in the environment, specifically the air and in wastewater.[78]
Synthetic single crystals of TiO2,ca. 2–3 mm in size, cut from a larger plate

Nanotubes

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Titanium oxide nanotubes,SEMimage
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.

Anatase can be converted intonon-carbon nanotubesandnanowires.[79]Hollow TiO2nanofibers can be also prepared by coatingcarbon nanofibersby first applyingtitanium butoxide.[80]

SEM(top) andTEM(bottom) images ofchiralTiO2nanofibers[80]

Health and safety

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As of 2006, titanium dioxide has been regarded as "completely nontoxic".[4]Widely-occurring minerals and even gemstones are composed of TiO2.All natural titanium, comprising more than 0.5% of the Earth's crust, exists as oxides. Although no evidence points to acute toxicity, recurring concerns have been expressed about nanophase forms of these materials. Studies of workers with high exposure to TiO2particles indicate that even at high exposure there is no adverse effect to human health.[81]

The European Union removed the authorization to use titanium dioxide (E 171) in foods, effective 7 February 2022, with a six months grace period.[82]

Titanium dioxide dust, when inhaled, has been classified by theInternational Agency for Research on Cancer(IARC) as anIARC Group 2B carcinogen,meaning it ispossibly carcinogenic to humans.[83][84] The USNational Institute for Occupational Safety and Healthrecommends two separate exposure limits. NIOSH recommends that fineTiO
2particles be set at an exposure limit of 2.4 mg/m3,whileultrafineTiO
2be 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.[85]

As of May 2023, following the European Union 2022 ban, the U.S. statesCaliforniaandNew Yorkwere considering banning the use of titanium dioxide in foods.[86]

Environmental waste introduction

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Titanium dioxide (TiO₂) is mostly introduced into the environment asnanoparticlesvia wastewater treatment plants.[87]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.[87]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.[87]In the process of dissolution, water-soluble ions typically dissociate from the nanoparticle into solution when thermodynamically unstable. TiO2dissolution 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.[88][89]

National policies on food additive use

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TiO2whitener in food was banned in France from 2020, due to uncertainty about safe quantities for human consumption.[90]

In 2021, theEuropean Food Safety Authority(EFSA) ruled that as a consequence of new understandings ofnanoparticles,titanium dioxide could "no longer be considered safe as a food additive", and the EU health commissioner announced plans to ban its use across the EU, with discussions beginning in June 2021. EFSA concluded thatgenotoxicity—which could lead tocarcinogeniceffects—could not be ruled out, and that a "safe level for daily intake of the food additive could not be established".[91]In 2022, the UK Food Standards Agency and Food Standards Scotland announced their disagreement with the EFSA ruling, and did not follow the EU in banning titanium dioxide as a food additive.[92]Health Canada similarly reviewed the available evidence in 2022 and decided not to change their position on titanium dioxide as a food additive.[93]

As of 2024, theFood and Drug Administration(FDA) in the United States permits titanium dioxide as a food additive. It is commonly used to increase whiteness and opacity in dairy products (lowfat milk, cream, ice cream, yogurt, etc), candies, frostings, fillings, and many other foods. The FDA permits the product's ingredients list to identify titanium dioxide as "color added" or "artificial colors" and does not require that titanium dioxide be explicitly named[94][95][96]despite growing scientific concerns.[97]In 2023, theConsumer Healthcare Products Association,a manufacturer's trade group, defended the substance as safe at certain limits while allowing that additional studies could provide further insight, saying an immediate ban would be a "knee-jerk" reaction.[98]

Research as an ingestible nanomaterial

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Due to the potential that long-term ingestion of titanium dioxide may be toxic, particularly to cells and functions of thegastrointestinal tract,preliminary research as of 2021 was assessing its possible role in disease development, such asinflammatory bowel diseaseandcolorectal cancer.[99]

Culture and society

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Companies such asDunkin' Donutsdropped titanium dioxide from their merchandise in 2015 after public pressure.[100]Andrew Maynard, director of Risk Science Center at theUniversity of Michigan,rejected 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.[101] Still, size distribution analyses showed that batches of food-grade TiO₂ always include a nano-sized fraction as inevitable byproduct of the manufacturing processes.[102]

See also

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Sources

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This article incorporates text from afree contentwork. Licensed under CC-BY. Text taken fromProduction of titanium and titanium dioxide from ilmenite and related applications​,WIPO.

References

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