What Makes Alumina So Versatile and Superior?
The selection of Alumina over Silica is increasing rapidly. It is because of its unique characteristics and high durability. Alumina products are widely used in many industrial applications.
Alumina is a synthetically produced aluminum oxide (Al2O3). It is a white or almost colourless crystalline substance that is used in the smelting process of aluminum metal. It is treated as an active agent in chemical process and used as a raw material for an extensive variety of advanced ceramic products. Alumina is prepared from bauxite, a naturally occurring ore containing uneven amounts of hydrous aluminum oxides (water containing). Aluminium oxide is present in the nature as the mineral corundum and also in its gemstone forms ruby and sapphire.
Alumina displays unique amphoteric properties:
Al2O3 has unique amphoteric properties with both anions and cations over a broad pH range. It acts as a weak ion exchanger and has an ability to act either as an acid or a base therefore, it is called as amphoterism. Alumina has higher amphoteric properties than any other separation substrate. It is an insoluble compound that can be made by dissolving and reacting with either base or acid. From the entire metal oxides, alumina performs best in this role as an amphoteric ion exchanger. In contrast, the more usually used silica only allows for a cation exchange due to its low pH. Because of this property, the alumina products are widely used. They show both acid and base properties which makes its products unique.
Alumina is stable:
Alumina is stable throughout the pH range of 2-13. It has the ability to overcome moderately high and low pH instability of silica. When silica is used in a chromatography column at higher pH, it always gets a column collapse associated directly with its dissolution. Stability is the most important feature of Alumina. Furthermore, it also leads to the consequential development of voids in the column. These complexities are characterized by sudden decrease in plate numbers as well as sheer increase in tailing factors. The mobile phase containing phosphate can dissolve and deteriorate the performance. Therefore, it is advisable to run the silica in stationary phase column at a temperature of 50ºC and a pH of 10.
Alumina has higher values of pH pzc:
At a neutral pH, the surface of aluminium oxide does not have a negative charge and will not interrelate with charge bases using electrostatic interactions. At low pH, the alumina surface has a positive charge while at the higher pH, the surface charge is negative. The zero point charge (no net charge) of Al2O3 occurs at pH 9.2 but it can be shifted using buffers.
Alumina is suitable to use at high temperature and it does not break down like silica:
Alumina provides such high versatility and stability, which no other separation substrate can provide. It can be used for an amazingly wide range of applications. It can be used for industrial, pharmaceutical, biohazard, bioterrorism, research, environmental cleanup, toxic waste and liquid gas dehydration applications.
Alumina has Lewis acid sites: These sites are responsible for ligand exchange capacity.
Alumina can also be used to remove:
Source: Free Articles from ArticlesFactory.com
ABOUT THE AUTHOR
I have great experience in making ceramics with a variety of materials like Boron nitride, aluminium nitride, Tungsten carbide etc. I also manufactures Tungsten and Alumina products.