# titanium dioxide

> chemical compound

**Wikidata**: [Q193521](https://www.wikidata.org/wiki/Q193521)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Titanium_dioxide)  
**Source**: https://4ort.xyz/entity/titanium-dioxide

## Summary
Titanium dioxide (TiO₂) is a naturally occurring chemical compound widely used as a white pigment, food coloring (E171), and excipient in pharmaceuticals, cosmetics, and sunscreens. It is valued for its high refractive index, opacity, and UV-blocking properties, making it essential in industries ranging from paints to personal care products. As a stable, non-toxic oxide of titanium, it also serves as a biocompatible material in medical and industrial applications.

## Key Facts
- **Chemical formula**: TiO₂, with a molecular mass of **79.938 daltons**.
- **CAS Registry Number**: 13463-67-7; **InChI**: `InChI=1S/2O.Ti`; **InChIKey**: `GWEVSGVZZGPLCZ-UHFFFAOYSA-N`.
- **E-number**: E171 (approved as a food additive).
- **Density**: **4.26 g/cm³** at 20°C.
- **Melting point**: **1,843°C** (3,349°F); **boiling point**: **2,500–3,000°C** (4,532–5,432°F, depending on conditions).
- **Vapor pressure**: **0 mmHg** at 20°C (non-volatile).
- **Ionization energy**: **9.54 eV** (first ionization).
- **Solubility**: Insoluble in water; chemically inert under most conditions.
- **Crystal structures**: Exists in three mineral forms—**rutile** (most stable), **anatase**, and **brookite**.
- **Uses**:
  - **Food industry**: White coloring agent (E171).
  - **Pharmaceuticals**: Excipient and pigment.
  - **Cosmetics/Sunscreens**: UV filter (CI 77891).
  - **Industrial**: Pigment in paints, plastics, and paper (e.g., "Titanweiß" or "Titanium White").
  - **Medical**: Biocompatible material for implants; photosensitizer in research.
- **Safety classifications**:
  - **NFPA 704**: Health (1), Flammability (0), Reactivity (0).
  - **OSHA exposure limits**: Time-weighted average (TWA) of **15 mg/m³** (8-hour workday).
  - **NIOSH ID**: 0617; **immediately dangerous to life or health (IDLH)**: **5,000 mg/m³**.
  - Classified as an **occupational carcinogen** (inhalation of fine particles).
- **Regulatory identifiers**:
  - **PubChem CID**: 26042; **ChEBI ID**: 32234; **ChemSpider ID**: 24256.
  - **EC Number**: 236-675-5; **HSDB ID**: 869; **RTECS Number**: XR2775000.
- **Hazard associations**: Titanium dioxide exposure linked to respiratory risks in occupational settings.
- **Notable aliases**: Titania, rutile, anatase, E171, CI 77891, 二酸化チタン (Japanese), 钛白粉 (Chinese), диоксид титана (Russian).

## FAQs

### What is titanium dioxide used for?
Titanium dioxide is primarily used as a **white pigment** in paints, plastics, and paper due to its opacity and brightness. It is also a **food additive (E171)** for coloring, a **UV filter in sunscreens**, and an **excipient in pharmaceuticals**. In industrial applications, it serves as a catalyst support, photocatalyst, and biocompatible material for medical implants.

### Is titanium dioxide safe?
Titanium dioxide is **generally recognized as safe (GRAS)** in food and cosmetic applications when used within regulatory limits. However, **inhalation of fine particles** (e.g., in occupational settings) is classified as an **occupational carcinogen** by NIOSH. The **EU banned E171** in food in 2022 due to concerns over nanoparticle toxicity, while the **FDA maintains its approval** in the U.S. under specified conditions.

### What are the different forms of titanium dioxide?
Titanium dioxide occurs in three **crystalline forms**:
1. **Rutile**: The most stable and common form, used in pigments and sunscreens.
2. **Anatase**: Less stable but more photocatalytically active, used in self-cleaning surfaces and solar cells.
3. **Brookite**: Rare and metastable, with limited industrial use.
Each form has distinct optical and physical properties, influencing its applications.

### How does titanium dioxide work in sunscreens?
Titanium dioxide **blocks UV radiation** by reflecting and scattering UVB and UVA rays. Unlike chemical sunscreens, it sits on the skin’s surface, making it ideal for sensitive skin. It is often combined with **zinc oxide** for broader UV protection and is a key ingredient in **mineral sunscreens**.

### What industries rely on titanium dioxide?
- **Paints/Coatings**: Provides opacity and durability (e.g., "Titanium White" in artist paints).
- **Food/Cosmetics**: E171 for whitening (e.g., candies, toothpaste, skincare).
- **Plastics/Paper**: Enhances brightness and UV resistance.
- **Pharmaceuticals**: Used as a colorant and excipient in tablets.
- **Energy**: Photocatalyst in **solar cells** and **hydrogen production**.
- **Medical**: Biocompatible coatings for implants (e.g., dental, orthopedic).

### What are the environmental impacts of titanium dioxide?
Titanium dioxide is **non-toxic to aquatic life** in bulk form but may pose risks as **nanoparticles**, which can accumulate in ecosystems. Its production involves **energy-intensive mining** (e.g., ilmenite ores) and **chemical processing**, contributing to carbon emissions. However, it is **chemically inert** and does not bioaccumulate.

### How is titanium dioxide regulated?
- **Food**: Approved as E171 in the U.S. (FDA) and formerly in the EU (banned in 2022).
- **Cosmetics**: Permitted as CI 77891 (EU/US).
- **Occupational safety**: OSHA sets a **TWA of 15 mg/m³**; NIOSH recommends **respiratory protection** for fine particles.
- **Environmental**: Classified as **non-hazardous waste** under EPA guidelines.

### What are the alternatives to titanium dioxide?
- **Food**: Calcium carbonate, rice starch, or vegetable-based colorants.
- **Sunscreens**: Zinc oxide (mineral) or chemical UV filters (e.g., avobenzone).
- **Pigments**: Zinc oxide, lithopone, or organic dyes (though less opaque).
- **Industrial**: Silicon dioxide or aluminum oxide (for some applications).

## Why It Matters
Titanium dioxide is one of the **most widely used white pigments globally**, with an annual production exceeding **9 million tons**. Its **opacity, stability, and non-toxicity** make it indispensable in **paints, plastics, and food**, where it enhances brightness and durability. In **sunscreens**, it provides **broad-spectrum UV protection** without irritating sensitive skin, while its **photocatalytic properties** enable innovations in **self-cleaning surfaces** and **renewable energy** (e.g., splitting water for hydrogen fuel). Despite its benefits, concerns over **nanoparticle safety** and **occupational hazards** have spurred regulatory scrutiny, particularly in the EU, where its use in food was banned. As a **biocompatible material**, it also plays a critical role in **medical implants**, reducing rejection risks. Its versatility underscores its status as a **cornerstone of modern materials science**.

## Notable For
- **Most widely used white pigment**: Dominates the **paint, plastic, and paper industries**, accounting for **~70% of global pigment demand**.
- **Highest refractive index** of any white pigment (2.7 for rutile), providing **superior opacity** at lower concentrations.
- **First mineral sunscreen**: Enabled **broad-spectrum UV protection** without chemical absorption, revolutionizing sun care for sensitive skin.
- **Photocatalytic properties**: Used in **self-cleaning surfaces** (e.g., tiles, windows) and **air/water purification** systems.
- **Biocompatibility**: Critical for **medical implants** (e.g., dental, orthopedic) due to its **inertness and corrosion resistance**.
- **Food industry staple**: E171 was used in **~36% of food products** (e.g., candies, chewing gum) before the EU ban.
- **Industrial durability**: Resistant to **heat, chemicals, and UV degradation**, making it ideal for outdoor coatings.

---

### Chemical Properties and Structure
Titanium dioxide (TiO₂) is a **transition metal oxide** with a **tetragonal crystal structure** in its rutile and anatase forms. Its **high refractive index** (2.5–2.7) and **strong UV absorption** stem from its **electronic band gap** (~3.0–3.2 eV), which varies by crystal form:
- **Rutile**: Most stable, with a **band gap of 3.0 eV**; used in **pigments and sunscreens**.
- **Anatase**: More photocatalytically active (**band gap 3.2 eV**), used in **solar cells and environmental applications**.
- **Brookite**: Metastable, with limited industrial use.

The compound’s **chemical formula (TiO₂)** reflects its **stoichiometric ratio**, though real-world samples may contain trace impurities (e.g., iron, chromium) from mining. Its **InChIKey (`GWEVSGVZZGPLCZ-UHFFFAOYSA-N`)** and **SMILES (`O=[Ti]=O`)** confirm its simple yet stable structure.

---

### Industrial Production
Titanium dioxide is produced via two primary methods:
1. **Sulfate Process** (older, ~40% of global production):
   - **Ilmenite ore (FeTiO₃)** is digested in **sulfuric acid**, producing **titanyl sulfate (TiOSO₄)**.
   - **Hydrolysis** yields **hydrated TiO₂**, which is **calcined** at **800–1,000°C** to form the final pigment.
   - **Byproducts**: Iron sulfate (often repurposed or landfilled).

2. **Chloride Process** (preferred for high-purity applications):
   - **Rutile ore** is **chlorinated** at **900–1,000°C** to form **titanium tetrachloride (TiCl₄)**.
   - **Oxidation** of TiCl₄ with **oxygen** at **1,500°C** produces **pure TiO₂** and **chlorine gas** (recycled).
   - **Advantages**: Higher purity, smaller particle size, and lower environmental impact.

**Global production**: ~**9 million tons/year**, with **China, the U.S., and Germany** as leading producers. The **chloride process** dominates (~60%) due to its efficiency and lower waste.

---

### Applications by Industry

#### Paints and Coatings
- **Primary use**: **White pigment** in **architectural paints, industrial coatings, and artist materials** (e.g., "Titanium White").
- **Properties**: **High hiding power** (requires **~20% less pigment** than alternatives like zinc oxide), **UV resistance**, and **durability**.
- **Market share**: ~**50% of global TiO₂ demand** (2023).
- **Notable products**: **Sherwin-Williams**, **PPG Industries**, and **AkzoNobel** paints.

#### Food and Pharmaceuticals
- **E171**: Used as a **whitening agent** in **candies, chewing gum, sauces, and medications** (e.g., tablets, capsules).
- **Regulatory status**:
  - **FDA**: Approved as a **color additive** (21 CFR 73.575).
  - **EU**: Banned in **2022** (EFSA concluded insufficient safety data for nanoparticles).
- **Alternatives**: **Calcium carbonate**, **rice starch**, or **vegetable-based colorants**.

#### Cosmetics and Personal Care
- **CI 77891**: **UV filter** in **sunscreens, foundations, and lipsticks**.
- **Mechanism**: **Reflects/scatter UV rays** (unlike chemical filters, which absorb them).
- **Nanoparticle concerns**: **<100 nm particles** may penetrate skin; **EU requires labeling** for nano-TiO₂.
- **Brands**: **La Roche-Posay**, **Neutrogena**, **L’Oréal**.

#### Plastics and Paper
- **Plastics**: Enhances **brightness, opacity, and UV resistance** in **PVC, polyolefins, and engineering plastics**.
- **Paper**: Improves **whiteness and printability** (used in **~30% of coated paper**).
- **Key players**: **DuPont**, **Chemours**, **Tronox**.

#### Energy and Environmental Applications
- **Photocatalysis**: Anatase TiO₂ **degrades organic pollutants** under UV light (used in **self-cleaning windows** and **air purifiers**).
- **Solar cells**: **Dye-sensitized solar cells (DSSCs)** use TiO₂ as a **semiconductor**.
- **Hydrogen production**: **Photoelectrochemical water splitting** for **green hydrogen**.

#### Medical and Dental
- **Biocompatibility**: Used in **orthopedic implants** (e.g., hip/knee replacements) and **dental implants** due to **corrosion resistance**.
- **Drug delivery**: TiO₂ nanoparticles investigated for **targeted cancer therapies**.
- **Standards**: **ASTM F67** (unalloyed titanium) and **ISO 5832** (implant materials).

---

### Safety and Toxicology
#### Occupational Hazards
- **Inhalation risks**: **Fine particles** (especially **<10 µm**) can cause **lung inflammation** and are classified as **Group 2B carcinogens** (IARC).
- **Exposure limits**:
  - **OSHA TWA**: **15 mg/m³** (8-hour workday).
  - **NIOSH IDLH**: **5,000 mg/m³**.
- **Protection**: **Respirators (N95/P100)**, ventilation, and **wet processing** to reduce dust.

#### Environmental Impact
- **Non-toxic in bulk**: **LD50 > 5,000 mg/kg** (oral, rats); **no bioaccumulation**.
- **Nanoparticles**: May **harm aquatic organisms** (e.g., algae, fish) at high concentrations.
- **Production waste**: **Iron sulfate** (sulfate process) and **chlorine gas** (chloride process) require **treatment/recycling**.

#### Consumer Safety
- **Food (E171)**: **EU banned** in 2022; **FDA maintains approval** pending further study.
- **Sunscreens**: **Non-nano TiO₂** is considered safe; **nano-TiO₂** requires labeling in the EU.
- **Cosmetics**: **CI 77891** is permitted but subject to **nanomaterial regulations**.

---

### Regulatory Landscape
| **Region**       | **Status**                                                                 | **Key Regulations**                                                                 |
|------------------|----------------------------------------------------------------------------|------------------------------------------------------------------------------------|
| **United States** | Approved (FDA, OSHA)                                                       | **21 CFR 73.575** (food), **OSHA PEL 15 mg/m³**, **NIOSH REL 10 mg/m³ (total dust)** |
| **European Union** | **E171 banned (2022)**; **CI 77891 permitted** (with nano labeling)        | **EFSA 2021 opinion**, **REACH Annex XVII**                                        |
| **Japan**        | Approved (E171, CI 77891)                                                  | **Food Sanitation Act**, **Pharmaceutical Affairs Law**                            |
| **China**        | Approved (GB 2760-2014)                                                    | **National Food Safety Standard**                                                  |

---

### Research and Innovations
- **Photocatalysis**: TiO₂ nanoparticles used in **self-cleaning surfaces** (e.g., **Pilkington Activ™ glass**) and **water treatment** (degrading **dyes, pesticides**).
- **Cancer therapy**: **Photodynamic therapy (PDT)** leverages TiO₂’s **photosensitizing properties** to target tumors.
- **Energy storage**: TiO₂ nanotubes investigated for **lithium-ion battery anodes**.
- **3D printing**: TiO₂-reinforced **polymers** for **UV-resistant prototypes**.

---

### Economic Impact
- **Market size**: **$22 billion (2023)**, projected to reach **$30 billion by 2030** (CAGR ~5%).
- **Key players**: **Chemours**, **Tronox**, **Venator**, **Kronos**, **Lomon Billions**.
- **Price drivers**: **Energy costs** (chloride process), **environmental regulations**, and **demand from China**.
- **Trade**: **China exports ~30% of global supply**; **U.S. and EU** are net importers.

---

### Cultural and Historical Significance
- **Art**: "Titanium White" (introduced in **1920s**) became the **standard white pigment** for artists like **Picasso** and **Pollock**, replacing **lead white** due to toxicity concerns.
- **Industrial revolution**: TiO₂’s **opacity** enabled **brighter, more durable paints**, transforming **automotive and architectural coatings**.
- **Space exploration**: Used in **NASA’s spacecraft coatings** for **UV and thermal protection**.
- **Symbolism**: Represents **purity and modernity** in **cosmetics and design** (e.g., **white iPhone**).

---

### Challenges and Controversies
- **Nanoparticle safety**: **EU’s E171 ban** (2022) sparked global debates over **nanomaterial regulation**.
- **Occupational health**: **IARC classification** (Group 2B) led to **stricter workplace controls**.
- **Environmental concerns**: **Mining impacts** (e.g., **ilmenite extraction**) and **chemical waste** from production.
- **Competition**: **Zinc oxide** and **organic pigments** challenge TiO₂’s dominance in **sunscreens and coatings**.
- **Geopolitical risks**: **China’s export controls** on titanium ore affect global supply chains.

---

### Future Outlook
- **Sustainable production**: **Recycling TiO₂ from waste** (e.g., **red mud**) and **green chemistry** methods.
- **Nanotechnology**: **Safer nanoparticle designs** for **medical and environmental applications**.
- **Energy**: **TiO₂-based photocatalysts** for **hydrogen fuel** and **carbon capture**.
- **Regulatory shifts**: **Stricter global standards** for **food and cosmetic uses**.
- **Emerging markets**: **India and Southeast Asia** driving demand for **infrastructure coatings**.

## References

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