Activated alumina is manufactured from aluminum hydroxide by dehydroxylating it in a way that produces a highly porous material. It’s a form of aluminum oxide (Al2O3) with a myriad of industrial uses.
This material can have a surface area significantly over 200 m²/g. Activated alumina will not soften or disintegrate when immersed in liquids.
Activated alumina as a desiccant, will work by adsorption. The water in the air will stick to the alumina as the air passes through it. The water molecules become trapped so that the air is dried out as it passes through the filter. This process of regenerating the alumina is achieved when the activated alumina desiccant is heated, it will let go of all of the water stored in it, allowing it to be used over and over.
A recent industry report by Grand View Research estimates the activated alumina market will see a CAGR of 5.4% up to 2025, largely as a result of its use in water treatment applications, which continue to grow in importance, as well as its use as a catalyst in the oil and gas industry.
Much like activated carbon, the high surface area and porosity exhibited by activated alumina allows it to capture and hold on to various types of materials, lending it to be employed as an adsorbent, desiccant, and more. The primary ways in which activated alumina products are used include:
Activated alumina is a highly effective adsorbent in both gas and liquid applications, and as such, is employed by a number of industries for targeted removal of components from other media.
As an adsorbent, activated alumina is most well known for its use in water filtration applications, where it serves as a cost-effective adsorbent for removing fluoride from water. It is also capable of removing a variety of other contaminants, including arsenic, lead, and sulfur.
Similar to its role as an adsorbent, activated alumina can also adsorb water from air, allowing it to be used as a desiccant; activated alumina can capture and trap water in order to keep things dry, much like silica gel. As a desiccant, activated alumina can adsorb up to 20% of its own weight in water at a relative humidity of 50%.
Activated alumina is employed as a desiccant in a wide variety of applications, including the removal of water vapor from gases in industrial settings. Water adsorbed onto the activated alumina can then be desorbed via thermal treatment and the alumina reused.
Activated alumina is also widely used as a catalyst, with roles as the catalyst itself, as well as an inert carrier, or substrate for other catalysts.
As a catalyst, activated alumina is most well known for its role as a Claus catalyst; activated alumina is the most commonly used Claus catalyst in sulfur recovery endeavors at oil and gas refineries.
Activated alumina may be regenerated to its original adsorption efficiency by heating to a temperature between 350-600°F (177-316°C).