Activated alumina is manufactured from aluminum hydroxide by dehydroxylating a manner that produces a highly porous material, this material can have a significantly lower surface area of 200 sq.m / g. The compound was used as drying agent (to keep things dry by air water absorption) and as a filter fluoride, arsenic and selenium in drinking water. It consists of aluminum oxide (alumina Al2O3), the chemical sapphire and ruby (but not those impurities that give color gems). It has a very high surface area-to-weight ratio. That means that has a large number of very small pores, almost as tunnels, running along it.
Activated alumina is used for a wide range of applications of adsorbents and catalysts, including adsorption catalyst in the production of polyethylene in the production of hydrogen peroxide as a selective adsorbent for many chemicals, including arsenic, fluoride, in the removing sulfur from gas streams (Catalyst Claus process).
Use as a desiccant, works through a process called adsorption. The water in the air actually sticks to the alumina itself in between the small passages, as air passes through them. The water molecules are trapped in a manner that dries the air as it passes through the filter. This process is reversible, if the desiccant and alumina is heated to approximately 200 ° C will release all the water stored therein. This process is called regeneration of the desiccant. The air always has some water in it, a means of measuring the amount of water in the air is the air dew point.
The adsorbent fluoride
Activated alumina is also widely used to remove fluoride from drinking water. In the U.S., there is widespread programs to fluoridate drinking water. However, in some regions, such as the Jaipur region of India, there is enough fluoride in the water to cause fluorosis. Activated alumina filters can easily reduce the fluoride levels less than 0.5 ppm to 0.1 ppm. The amount of fluoride leached from the filtered water depends on the time that water is touching the alumina filter media. Basically, the alumina in the filter, the less will fluoride in the final water, filtered. Low water temperature and a lower pH of the water (acidic water) were also more effectively filtered.
Activated alumina, when used as a filter of fluoride can be regenerated by sodium hydroxide solution (sodium hydroxide, NaOH), sulfuric acid (H2SO4) or alum (KAl (SO4) 2).