With a surface area of over 200 m²/g, Activated alumina is commonly used as a desiccant and a filter of fluoride, arsenic and selenium in drinking water. It is made of aluminium oxide (alumina; Al2O3) and has a very high surface-area-to-weight ratio due to its tunnel-like pores.
Activated alumina is used for several adsorbent and catalyst applications such as the adsorption of catalysts in polyethylene and hydrogen peroxide production. It also acts as a selective adsorbent for chemicals such as arsenic, fluoride, and sulphur removal from gas streams (Claus Catalyst process).
Being highly adsorbent, water vapour in water and gases stick to the Activated Alumina and is trapped inside. Handlers can release the trapped water molecules by heating the desiccant to ~200 °C.
Activated alumina is also widely used to remove fluoride from drinking water, easily reducing fluoride levels from 10.0 ppm (parts per million) to less than 1.0 ppm. The amount of fluoride removed from the water being filtered depends on how long the water actually touches the alumina filter media. With increased alumina, the amount of fluoride left in the filtered water decreases. Lowering the temperature and the pH of the water enables more effective filtering as well, with the ideal pH for being 5.5, which allows for up to a 95% removal rate.
Activated alumina can also be used in high vacuum applications. It works as a charge material in fore-line traps to prevent oil generated by rotary vane pumps from back streaming into the system.