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 production and in hydrogen peroxide production. It also acts as a selective adsorbent for chemicals such as arsenic, fluoride, in sulphur removal from gas streams (Claus Catalyst process).
Being highly adsorbent, water vapour in water and gases sticks to the Activated Alumina itself. The water molecules will then be trapped in the alumina. 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. Its filters can easily reduce fluoride levels from 10.0 ppm to less than 1.0 ppm. The amount of fluoride leached from the water being filtered depends on how long the water is actually touching the alumina filter media. When the amount of alumina in the filter increases, the amount of fluoride existing in the filtered water decreases. Lower temperature water, and lower pH water (acidic water) are filtered more effectively too. Ideal pH for treatment is 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.