Sunscreen With Titanium Dioxide-How To Produce Titanium Dioxide

Titanium dioxide (TiO2) is a white pigment used in a variety of products, including paints, coatings, plastics, paper, and sunscreen. It is also used in the manufacturing of food and cosmetics. There are two main processes for producing titanium dioxide: the sulfate process and the chloride process.

### Sulfate Process

The sulfate process, also known as the wet process, is the older and more common method of producing titanium dioxide. Here’s a general overview of the steps involved:

1. **Raw Material Extraction**: Titanium is usually extracted from ilmenite (FeTiO3), rutile (TiO2), or leucoxene (a concentrate of natural titanium minerals).

2. **Pulverization**: The raw material is finely ground to increase the surface area for reaction.

3. **Reaction with Sulfuric Acid**: The powdered ore is mixed with sulfuric acid (H2SO4) to form a sulfate solution of titanium. This step is highly exothermic and requires careful temperature control.

“`

TiO2 + H2SO4 → Ti(SO4)2 + H2O

“`

4. **Separation of Impurities**: Impurities such as iron are removed by adding硫酸铵 ((NH4)2SO4) and filtering the mixture.

5. **Hydrolysis**: The titanium sulfate solution is hydrolyzed to form hydrated titanium dioxide.

“`

Ti(SO4)2 + 2H2O → TiO2·xH2O + 2H2SO4

“`

6. **Purification**: The hydrated titanium dioxide is purified by washing to remove any remaining sulfate and other impurities.

7. **Calcination**: The hydrated titanium dioxide is heated (calcined) to remove water and convert it into an anatase or rutile form, which are the two most common crystalline forms of titanium dioxide.

“`

TiO2·xH2O → TiO2 + xH2O (evaporation)

“`

8. **Surface Treatment**: Finally, the titanium dioxide may be surface-treated with various chemicals to improve its properties for specific applications.

### Chloride Process

The chloride process, also known as the dry process, is a more modern method that is gaining popularity due to its efficiency and environmental benefits:

1. **Raw Material Preparation**: Similar to the sulfate process, the raw material is usually ilmenite or rutile.

2. **Reaction with Chlorine**: The ore is chlorinated in a fluidized bed reactor at high temperatures to produce titanium tetrachloride (TiCl4).

“`

TiO2 + 2Cl2 + 2C → TiCl4 + 2CO

“`

Note: Coke or coal is often used as a reducing agent.

3. **Purification**: The TiCl4 is purified by fractional distillation to remove any volatile impurities.

4. **Oxidation**: The purified TiCl4 is oxidized in an oxygen-fired reactor to produce titanium dioxide.

“`

TiCl4 + O2 → TiO2 + 2Cl2

“`

5. **Surface Treatment**: As with the sulfate process, surface treatment may be applied to enhance the properties of the titanium dioxide.

6. **Packaging**: The final product is then packaged for sale or use in various applications.

Both processes require careful environmental controls to manage emissions and by-products, such as chlorine gas and sulfuric acid, which can be hazardous if not handled properly. The choice between the sulfate and chloride processes depends on factors such as the cost of raw materials, the desired quality of the titanium dioxide, and environmental regulations.