Titanium Dioxide In Supplements-How Does Titanium Dioxide Degrade

Titanium dioxide (TiO2) is a white, powdery substance that is widely used as a pigment in paints, plastics, and papers, as well as in sunscreen products for its ability to reflect and scatter ultraviolet (UV) light. It is also known for its photocatalytic properties, which means it can break down certain substances when exposed to light.

The degradation of titanium dioxide primarily occurs through the following ways:

1. **Photocatalytic Degradation:**

– When titanium dioxide is exposed to UV light, it can absorb the energy and become excited. This excitation promotes the transfer of an electron from the conduction band to the valence band, creating electron-hole pairs.

– These electron-hole pairs can then react with water and oxygen in the environment to produce highly reactive species such as hydroxyl radicals (•OH) and superoxide anions (O2•-).

– These reactive species can initiate the breakdown of organic materials on the surface of the TiO2, effectively degrading pollutants, odors, bacteria, and viruses.

2. **Thermal Degradation:**

– At high temperatures, titanium dioxide can undergo thermal degradation, which involves breaking down the crystal structure of the TiO2. This process can lead to a loss of photocatalytic activity and a change in the physical properties of the material.

3. **UV-Induced Discoloration:**

– Prolonged exposure to UV light can also cause changes in the crystal structure of TiO2, which may result in a change of color or a loss of opacity. This is less of a degradation in the traditional sense but rather a modification of the material’s appearance.

4. **Mechanical Wear and Abrasion:**

– In applications where titanium dioxide is used as a pigment or in coatings, physical wear and tear can abrade the surface, leading to a reduction in the concentration of TiO2 and a decrease in its effectiveness.

5. **Chemical Attack:**

– In certain environments, especially those with high acidity or alkalinity, titanium dioxide can be subject to chemical attack, which can alter its surface properties and reduce its photocatalytic efficiency.

The rate and extent of degradation depend on several factors, including the purity of the TiO2, its crystalline phase (anatase, rutile, or brookite), particle size, the presence of impurities or dopants, and the intensity and wavelength of the incident light. In practical applications, the stability of titanium dioxide is an important consideration, and various strategies are employed to enhance its resistance to degradation, such as surface modifications or the use of stabilizers.