Activated Alumina is manufactured from aluminium hydroxide producing a highly porous material. Besides filtering fluoride, arsenic and selenium in drinking water, the compound is used as a desiccant (to keep things dry by absorbing water from the air). It is made of aluminum oxide, the same chemical substance as sapphire and rubies minus the impurities. It has a very high surface-area-to-weight ratio. That means it has a lot of very small pores, almost like tunnels, that run throughout it.
Method:
Activated alumina filters can easily reduce fluoride levels from .5 ppm to less than .1 ppm. The amount of fluoride leached from the water being filtered depends on how long the water is actually touching the alumina filter media. Basically, the more alumina in the filter, the less fluoride will be in the filtered water. Lower temperature water, and lower pH water (acidic water) are filtered more effectively too.
Compound: Activated alumina, when used as a fluoride filter, can be regenerated by a solution of lye (sodium hydroxide; NaOH), sulfuric acid (H2SO4), or alum (KAl(SO4)2).
Pros and Cons:
Activated alumina filtration systems have some advantages and some problems. Their effective lifespan is fairly short, they are relatively expensive, and people don't like the word alumina in the name because it sounds too much like aluminum. That being said, filters with activated alumina are popular. They are most often used in conjunction with other filters, usually carbon, since activated alumina alone does little for water except remove fluoride and arsenic. It does not improve the taste or remove chemical contaminants like pesticides. By using an activated alumina cartridge combined with a carbon cartridge, you get a good, broad-range water filter.
How it Works:
In this process, water containing the contaminant is passed through a cartridge or canister of activated alumina. The alumina absorbs the contaminant and freshwater continues to the service faucet. The cartridge of activated alumina has to be replaced periodically. It is important to determine by testing when the contaminant removal capability of the device is exhausted, so the treatment technique will remove, not contribute, the contaminant. Also, activated alumia devices will accumulate bacteria, so treated water will have height bacteria counts than raw water.
Cleaning:
Activated Alumina requires periodic cleaning with an appropriate regenerate such as alum or acid in order to remain effective.
Where to Purchase:
http://www.aquasmart.com/Additional Reading:
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