Alumina can be divided into many types according to its crystal structure and physical and chemical properties. Among them, activated alumina and ordinary alumina have the same chemical composition, but there are significant differences in properties and applications. So, are activated alumina and alumina the same substance? What are the differences between them
1.Chemical composition
- Alumina:
It is a stable oxide of aluminum, the most common form is α-alumina, with a dense structure and strong chemical inertness.
- Activated alumina:
It usually refers to transitional alumina such as γ-alumina or η-alumina, with a loose and porous microstructure and a large specific surface area.
2. Comparison of physical properties
| characteristic | Activated alumina | Alumina |
| Crystal structure | Amorphous or transition phase (γ/η type) | Stable crystal phase (α type) |
| Specific surface area | high（200-400 m²/g） | Low（＜10 m²/g） |
| Porosity | Porous structure | Dense structure |
| Thermal stability | High temperature will turn into α phase | Stable, high temperature resistance |
3.Main differences
- Activity:
Activated alumina has a large number of unsaturated bonds and hydroxyl groups on its surface, and has strong adsorption and catalytic activity; ordinary alumina is highly inert and suitable for high-temperature refractory materials.
- Applications:
o Activated alumina: desiccant, catalyst carrier, water treatment adsorbent (such as fluoride removal).
o Ordinary alumina: ceramics, abrasives, refractory materials (such as crucibles, refractory bricks).
4.Why is activated alumina “active”?
The “activity” of activated alumina mainly comes from:
- High specific surface area: The porous structure provides more adsorption sites.
- Surface hydroxyl groups: can chemically adsorb with water and gas molecules.
- Unsaturated bonds: Enhance the interaction with other substances and improve the catalytic efficiency.
In contrast, ordinary alumina (α-Al₂O₃) has a dense structure, high surface inertness, and almost no adsorption or catalytic ability.
5.Conclusion: Are activated alumina and alumina the same?
- Similarities: Both have the same chemical composition of Al₂O₃.
- Differences:
o Crystal structure: Activated alumina is γ/η type, while ordinary alumina is α type.
o Physical properties: Activated alumina is porous and has a high specific surface area, while ordinary alumina is dense and has high hardness.
o Application areas: Activated alumina is used for adsorption and catalysis, while ordinary alumina is used for refractory and ceramics.
Therefore, although activated alumina and ordinary alumina have the same chemical formula, they are different materials and have completely different uses.
6.How to choose?
- If adsorption, catalysis or drying is required, choose activated alumina.
- If high temperature resistance, wear resistance or insulation is required, choose ordinary alumina.
I hope this article can help you clearly distinguish between activated alumina and ordinary alumina so that you can make the right choice in practical applications!