Fluoride removal – NEWDEF ®Hydroxyapatite
Fluoride Removal using NEWDEF: Hydroxylapatite, also called hydroxyapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH). Our media is specially treated and activated using aluminium to make it more effective. The principle of fluoride removal is based on the OH− ion in the media being replaced by fluoride producing fluorapatite .
It is one of the most effective adsorbents of fluoride with much faster reaction times than Activated Alumina. In comparative performance trials using Brisbane water containing Fluoride, aluminium activated Calcium Hydroxyapatite outperformed other media including activated alumina and fluoride specific ion exchange media.
Benefits of Calcium Hydroxyapatite media:
- Much faster contact times compared to activated alumina.
- Is a natural occurring mineral that is often used as a natural mineral supplement.
- Does not release any harmful substances into the water that is to be treated.
- Can be used for waste water treatment .
- Has a higher absorption capacity compared to other media used for de-fluoridation.
The De-fluoridation capacity of hydroxyapatite is about 2~4 mg/g which is superior compared to most medias under the same conditions. The capacity is impacted by different raw water quality including fluoride concentration, temperature, co-existing ions etc..
Hydroxyapatite Features and Benefits
- High capacity and shorter contact time
- Very safe to use; no dissolution of toxic and hazardous substances
- High efficiency, hydroxyapatite can remove up to 99% fluoride in raw water.
- Limited competing interference by other ions
- Lower regeneration cost and simple regeneration process
- Not only restricted to Fluoride ,but can remove iron and manganese as well
Fluoride Removal – Performance Comparison
Fig below demonstrates that the NEWDEF® media( Hydroxyapatite) outperforms other common Defluoridation materials under the same conditions. The treated water volume before fluoride breakthrough of NEWDEF® is About 5.09—11.7 times of activated alumina and 12.9—23 times of activated Clinoptilolite.
Figure 2. The volume of water treated by different media under the same conditions, the concentration of fluoride is 2mg/L in raw water
Sodium hydroxide regeneration
It’s the reverse reaction of the defluoridation mechanism. OH– replaces F– on the particle surface. Regeneration is carried out using 0.5 to 1 % caustic solution which is recirculated for 6-12 hours.