Alumina trihydrate (ATH) is the hydrated form of aluminum oxide, with the formula Al(OH)₃. It is a key industrial chemical, widely used in flame retardants, fillers, and as the precursor to calcined alumina.
🌍 Origins and Naming
- Name Origin: “Alumina trihydrate” reflects its composition: aluminum oxide combined with three molecules of water.
- Mineral Equivalent: Gibbsite (Al(OH)₃) is the natural mineral form.
- Industrial Source: Extracted from bauxite ore via the Bayer process, where alumina trihydrate is precipitated before calcination.
🔬 Chemical and Structural Properties
- Formula: Al(OH)₃
- Crystal System: Monoclinic (gibbsite).
- Color: White, powdery when processed; crystalline gibbsite is colorless to white.
- Hardness: ~2.5–3 on Mohs scale.
- Density: ~2.4 g/cm³.
- Stability: Decomposes upon heating (~180–200 °C), releasing water and forming alumina (Al₂O₃).
⚙️ Industrial and Technological Uses
- Flame Retardants: ATH releases water vapor when heated, cooling the material and diluting combustible gases.
- Fillers: Used in plastics, rubber, and paper for whiteness, opacity, and reinforcement.
- Electrical Insulation: Improves arc resistance in polymers.
- Ceramics & Glass: Precursor to calcined alumina for refractories and advanced ceramics.
- Water Treatment: Sometimes used as a coagulant.
📖 Scientific and Environmental Significance
- Materials Science: ATH is a critical intermediate in alumina production.
- Environmental Role: Flame-retardant ATH is favored as a halogen-free alternative, reducing toxic smoke in fires.
- Geology: Gibbsite is one of the three main aluminum hydroxide minerals in bauxite (with boehmite and diaspore).
✨ Conclusion
Alumina trihydrate (Al(OH)₃) is the hydrated precursor to alumina, naturally occurring as gibbsite and industrially vital for flame retardants, fillers, and ceramics. It bridges geology (bauxite minerals) and technology (advanced materials).
In short: Alumina trihydrate = Al(OH)₃, gibbsite, precursor to alumina, key in flame retardants and fillers.
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