Activated Alumina Works To Lower Fluoride to Safe Levels in Drinking Water

Water fluoridation is a double edged sword.  In the U.S. fluoride has been added to most water streams in order to help prevent tooth decay.  (I should mention fluoride naturally occurs in a lot of drinking water sources throughout the world).  However fluoride can be damaging to bones at higher doses and it can even be fatal if you take in large quantities of it.

The desiccant activated alumina plays a very important role in reducing fluoride levels in water.  By doing this activated alumina leaves enough fluoride in water for people to receive its potential health benefits while at the same time it makes sure that health damaging amounts of fluoride do not remain in drinking water.

In 1994 the World Health Organization recommended that fluoride levels in water should be contained from 0.5-1mg/L.  Fluoride levels above 1mg should undergo defluoridation, which can be done three different ways: with chemicals and precipitation, with membrane based technologies, or with ion exchange and adsorption.

A lot of times these methods are used in combination.  For example, when fluoride levels are above 15ppm using lime which falls under the chemicals and precipitation category should be used because they can handle the high levels of fluoride.  Once that level is lowered using lime, activated alumina, which falls under the adsorption category, should be used to reduce to the fluoride content to below 1ppm since activated alumina can purify water up to 99%.

How does Activated Alumina work in removing fluoride from water?

Activated alumina adsorbs fluoride because fluoride is attracted to alumina.  It wants to make aluminum fluoride which it does once it comes into contact with activated alumina.  The alumina fluoride will remain stuck to the alumina beads so long as the pH level of the water remains below 6.  If water’s pH remains lower than a 6 the effectiveness of activated alumina starts to be reduced.  It can also allow aluminum to get in your water, although aluminum does not typically dissolve in water.

Note: Reverse osmosis is used to remove aluminum from water and so can certain distillers.  Aluminum does not typically get into water because water has a difficult time dissolving it.

It’s recommended that you pre-treat activated alumina with aluminum sulfate before you use it in order to improve the first adsorption runs.  After pretreatment it’s important to remember that adsorption reactions with activated alumina are  flow-rate dependent.  Although activated can handle high flow rates and still work, its adsorption capacity is reduced and this could lead to having to do additional cycles.  Doubling the flow rate allowed 33% more fluoride through the activated alumina beds, thus reducing activated alumina effectiveness in adsorbing fluoride.

There is a possibility of other ions interfering with the adsorption process when working with activated alumina, this is due to water in the U.S. containing other ions.  These ions are usually sodium chloride, sodium sulfate, and sodium bicarbonate.  Sodium chloride and sodium sulfate do not interfere with the adsorption process, but sodium bicarbonate can reduce the capacity of activated alumina between 33% and 70%.

Activated alumina like most desiccants can be regenerated.   Sodium hydroxide, aluminum sulfate, or sulfuric acid are applied to a lye solution with the activated alumina, allowing the adsorbent to be regenerated.  Once regenerated activated alumina can continue to be re-used, and when used properly activated alumina can last years.

Activated alumina is essential in removing fluoride in water up to 99% and making water safe for people to drink.

Sources:

http://www.watersanitationhygiene.org/References/EH_KEY_REFERENCES/WATER/Water%20Quality/Fluoride/Defluoridation%20Using%20Activated%20Alumina%20%28UNICEF%29.pdf

http://www.bibliotecapleyades.net/salud/salud_fluor23.htm

World Health Organization: http://whqlibdoc.who.int/trs/WHO_TRS_846.pdf

http://www.tramfloc.com/tf133.html

Double Flow Rate = 33% decrease in adsorption capacity, reverse osmosis, and ions.  http://www.purewateroccasional.net/newnewsletter8.html

Water below pH of 6 reduces effectiveness of Activated Alumina http://greenlivingqa.com/content/fluoride-filtration-using-alum

Differences Between Glycol Treatment and Desiccant Treatment

Water removal from a natural gas stream (drying) is an important step in processing natural gas, it prevents corrosion in pipelines and also prevents plugging of pipelines by removing free water and hydrates.  Natural gas drying is preceded by the removal of oil and condensate from the natural gas stream.  Currently there are two common processes which see to the removal of water from gas streams: glycol treatment and desiccant treatment.

Glycol treatment primarily uses triethylene glycol , diethylene glycol, or tetraethylene glycol to adsorb and remove the water from the natural gas stream.  Glycol will adsorb water from liquid gas streams in a dehydrator.  As glycol adsorbs water it becomes heavier and sinks to the bottom of the dehydrator.  After the glycol has adsorbed the water it is boiled out of the dehydrator leaving behind liquid natural gas.

Desiccant dehydration requires the use of adsorption towers, which contain desiccant usually molecular sieve, activated alumina, or silica gel.  Wet natural gas is passed through the top of the tower which contains thousands of pounds of sieve or alumina beads and by the time it reaches the bottom of the tower the water will be removed from the gas stream.  Multiple adsorption towers are used during this process to allow over saturated desiccant to be regenerated.  In other words while one tower has gas running through it another tower is regenerating the previously used (and now over-saturated) desiccant.

The advantage of using dry desiccants is their ability to adsorb and reduce the water from natural gas streams to lower concentrations than glycol.  Pipelines require that water content in gas streams not exceed 7lb/MMSCF (million standard cubic feet) and dry desiccants can achieve this level easily (up to 2lb/MMSCF).  Glycol dehydrators can achieve this level but usually at the bare minimum and sometimes they don’t make the requirement and have to go through the treatment process again.  Although glycol treatment is more popular right now, dry desiccants appear to be more effective at drying natural gas.

http://www.kwintl.com/glycol-dehydrators.html

5 Ways You Didn’t Know Silica Gel Could Be Used

Silica gel is the most widely used desiccant in the world today, and it can be encountered in all different shapes, sizes, and colors.  Silica gel can be used industrially for adsorbing air dryers and and compressors, or you may find it in everyday items (for example in your vitamin pill canister)  in the form of tiny little packets.  It’s an adsorbent with many uses and chances are you have encountered silica gel in your life.  Its widespread use by consumers and industries have allowed silica gel to be used in creative new ways.  Here are 5 ways silica gel is being used that you may not have known about.

1. Storage of Musical Instruments -  Silica gel’s ability to reduce humidity has made silica gel packets a must for musicians who have to carry their equipment around in cases.  By placing little silica gel packets in instrument cases the silica gel reduces damage to instruments by reducing the amount of moisture and humidity that is collected while instruments are in storage or are traveling.
2. Drying Out Wet Cell Phones – If you ever get your cell phone wet, you know you might be forced into to having to buy an expensive new phone.  Well maybe not… if your quick enough you can remove the battery and memory cards and stick these parts as well as the phone in bowl filled with small silica gel packets.  The silica gel should do the trick and adsorb any liquid that is still attached to your phone.  Leave the phone  there for about 24 hours before you turn it back on and your cell phone should work fine.
3.  Camera Lens Protection – If you ever find yourself  taking photos underwater silica gel can be used protect your camera lens from condensation and unwanted moisture.  When going underwater to take photos you can put some small silica gel packets in the casing along with the camera, this protects against moisture and condensation.
4. Cat Litter – Silica gel can now be bought as cat litter and it’s highly effective too.  It has a higher adsorption rate than clay cat litter, it doesn’t clump, and it can turn color (from white to yellow) to let you know it’s time for a change out.  Silica gel cat litter also adsorbs smells, and is also odorless itself which is convenient if you hate the smell of cat litter.
5. Air Freshener – Now we’ve said silica gel is odorless, but that doesn’t mean it can’t be used to adsorb pleasant aromas as well.  If you take silica gel and soak the beads in fragrant smelling oils you can create your own scented silica gels, or your own air freshener.

These are some of the clever ways we’ve seen silica gel being used, and we would like to know if you have tried using silica gel in any of the ways mentioned above.  If you have any other clever uses for silica gel that were not posted here please share them.