Electrocoagulation could be a suitable method for removal fluiroride from solution that contain sodium. However you would have to correct pH before the treatment.

Reverse Osmosis will remove fluoride. Some ion exchange systems might.

There is a treatment technique widely used in India for the removal of fluoride from drinking water. It is called as 'Nalgonda Technique' .In this process alum and lime are added to the raw water and stirred for some time, flocs are formed out of alum and fluoride gets adsorbed to this which later settles down and can be filtered out.

You can use adsorption process by using different adsorbents as this process is generally considered the most effective and suitable method due to its simplicity, effectiveness and relatively low cost .Of many adsorbents, multivalent metal oxides and hydroxides and metals incorporated ion exchange resins were reported to have high F removal capacities

Electrocoagulation at the correct pH, Reverse Osmosis, both will remove Fluoride but not selectively. Other ions also will get removed to different extents

Calcium ions, you have just to deside which counterions you would like to have.For example CaCl2. In this case CaF2 is precipitating and Cl- stays in solution. Then centrifuge the white precipitate. The only negative side effect is that Ca is precipitating as hydroxide too.

the precipitation in the form of H2SiF6 after addition to the leachate of a sodium salt NaCl was chosen. Ten series of tests were carried out from on liter of leachate: 100 ml of leachate were added to various amounts of NaCl at ambient temperature with stirring during 30 minutes. The reactive mixtures were filtered and the precipitates dried and milled before being analyzed by X-ray diffraction.

the precipitation in the form of H2SiF6 after addition to the leachate of a sodium salt NaCl was chosen. Ten series of tests were carried out from on liter of leachate: 100 ml of leachate were added to various amounts of NaCl at ambient temperature with stirring during 30 minutes. The reactive mixtures were filtered and the precipitates dried and milled before being analyzed by X-ray diffraction.

Use inexpensive abundantly available adsorbent; discarded bones which improved excellent efficiency for fluoride removal. Fast, efficient, and applicable at any pH range.

Activated alumina or Ca(PO)4 waste like bones as mentioned by Zainab are adsorbents. Quaternary amine complexes such as found in Chitosan can also remove. Ion exchange can work, if you take a low cost water softening resin exhausted by calcium ions (hardness) resulting in CaF2 precipitation, not "exchange". In exchange, Cl has a higher equivalent weight, and will bump the Fluoride ion off.

Activated carbon

If the question relates to water intended for consumption (drinking-water), then there is a book published by WHO and freely downloadable at http://www.who.int/water_sanitation_health/publications/fluoride_drinking_water/en/ that may well be of interest and provides an overview of treatment options and experience with their application.

Activated carbon obtained from Nigerian Bamboo is relatively cheap. The adsorption capacity of this Activated carbon on the fluoride will depend on the surface area and volumetric flow rate of the fluoride slurry/effluent.

There are various techniques for the removal of fluoride from groundwater. Some of them are :

(1) Precipitation and complexiation ( Nalgonda Technique ),

(2) Activated alumina,

(3) Electro chemical

(4) Polymer resins.

For detailed study kindly go through my published papers.

Dear Jamie Bartram, Virendra Saxena and all who have contributed their experience and views on this issue, Thank you very much all of you.

I have two issue here, one is high Conc. of F (4-5%) and presence of Na in the solution, I think ion exchange will not work here.

Second is the selective adsorption, if we adsorb F on adsorbent (like Activated carbon....) how to recover it for useful thing and recycling of the adsorbent.

We can find plenty of paper on sorption of pollutant but lots of paper missed its recycling, it is like we collect something from one place and dump it to another place. I think, it will not solve the problem completely,

Here I am looking for complete solution like selective separation of F and its reuse for valuable thing.

Since fluoride is very high, I think adding calcium chloride will favorably precicipitate fluoride in the form of CaF2. Do you have a detailed water quality analysis for ions of other sparigly soluble salts. You can eliminate Ca(OH)2 precipitation by adding HCl and reducing the pH. However, if it is open system, CaCO3 can also precicipitate.

Best cheap ways to remove fluoride uptake is based on Activated alumina.

For reducing the Fluoride from solution, even 4 to 5 ppm, Electro chemical and polymer resins techniques can work up to satisfaction level. However recovery of F can be tried.

date pits activated carbon ( physical ( N2 gas ) or chemical ( 85% phoshoric acid ) is the best ( very cheap , easy obtained , prepared and good charterization . In addation , bone char obtained from camel bone give also good effeciency

Dear Atul,

You will get good fluoride removal with activated carbons doped with Al. But activated carbon is not selective. Removal performances are going to be affected by salt content in natural water and other elements usually associte to F as As. usually, adsoption tests are not carried out with natural water.

We published two papers on arsenic adsorption by iron doped carbons using natural well water, you can see them in my RG profile and we are actually working on F removal:

-Synthesis, characterization and performance in arsenic removal of iron-doped activated carbons prepared by impregnation with Fe(III) and Fe(II)

-Arsenic removal by iron-doped activated carbons prepared by ferric chloride forced hydrolysis

I agree that activated alumina is extensively used.

I suggest activated alumina.

The best method is by using waste bones, you can get up to 100% removal, especially chicken bones 

It is a cheap sustainable environmentally friendly approach

The precipitation of Na2SiF6 is more effective at room temperature using twice the stoichiometric amount of NaCl required. A typical test, 3.36g of NaCl (twice the stoichiometric amount necessary) were added to 100 ml of leachate (fluoride content = 8.74g/l) and subjected to stirring for half an hour.

Dear All,

Use of Adsorbents is quite effective. But in case of Water having high Iron content, the media might become clogged very often, which will need either time to time regeneration of Activated Alumina or replacement of the same. In that situation, use of Activated Alumina or other adsorbents at household level filtration may eventually turn out to be problematic. 

Moreover, strict monitoring ( through testing of filtered water ) is also necssary, which will facilitate to check the effectiveness of the Adsorbent, as the time elapsed. In the absence of that the filter with such adsorbents may not be helpful; however the users will still consider the same as capable of removing of Fluoride, even after the expiry of it's life.

Thanks and Regards.

Nripendra Kumar Sarma

Nagaon, Assam, India 

Dear Nripendra Kumar Sarma, you correct but I think there is no alternative other than membrane filtration followed by adsorption. As membrane filtration will remove what you worried about iron and selective adsorption will remove the other species/containment of worry.

But still problem  will not completely, regeneration of adsorbent is again a big issue .... 

Another possibility, you can use slag waste from stainless steel processes.