Titanium Dioxide Sunscreen-How Is Titanium Dioxide Obtained
Titanium dioxide (TiO2), also known as titania, is a white, powdery mineral that is widely used as a pigment in paints, plastics, papers, and foods, among other applications. It is obtained from various sources and through different processes, with the two main production methods being the sulfate process and the chloride process.
### Sulfate Process
The sulfate process is the older and more traditional method of producing titanium dioxide. Here’s a general outline of the steps involved:
1. **Mining**: Titanium dioxide is primarily extracted from ilmenite (FeTiO3) and rutile (TiO2), which are mined from open pit or underground mines.
2. **Crushing and Grinding**: The mined ore is crushed and ground to a fine powder.
3. **Pulping and Acid Treatment**: The powdered ore is mixed with water to create a pulp, which is then treated with sulfuric acid to dissolve the titanium components, leaving impurities behind.
4. **Hydrolysis**: The resulting titanium sulfate solution is hydrolyzed to form hydrated titanium dioxide.
5. **Purification**: The hydrated titanium dioxide is purified to remove any remaining impurities.
6. **Calcination**: The hydrated titanium dioxide is heated (calcined) to remove water and convert it into pure, anatase or rutile phase titanium dioxide.
7. **Pigment Production**: The calcined product is then milled and surface-treated to optimize its properties for various applications.
### Chloride Process
The chloride process is a more modern method that is considered to be more environmentally friendly and efficient:
1. **Mining**: As with the sulfate process, the raw materials are mined, typically rutile or ilmenite.
2. **Crushing and Grinding**: The ore is crushed and ground to increase the surface area for reaction.
3. **Oxygen Chlorination**: The powdered ore is heated in the presence of chlorine gas to produce titanium tetrachloride (TiCl4).
4. **Purification**: The titanium tetrachloride is purified to remove any trace metals.
5. **Oxidation**: The purified titanium tetrachloride is oxidized in a high-temperature reactor with oxygen to form titanium dioxide.
6. **Hydrolysis and Calcination**: The resulting titanium dioxide is hydrolyzed and calcined to obtain the final pigment.
7. **Surface Treatment**: The pigment is surface-treated to enhance its properties for specific applications.
Both processes produce high-purity titanium dioxide, but the chloride process tends to result in a pigment with more consistent particle size and shape, which can be advantageous for certain applications. The choice of method often depends on factors such as cost, environmental impact, and the desired properties of the final product.