Calcium Hydroxapatite for the removal of heavy metals and fluoride

Calcium Hydroxapatite for the removal of heavy metals and fluoride

Fluoride adsorption by calcium hydroxyapatite
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Calcium Hydroxyapatite  for heavy metals and fluoride removal from potable and waste water.

Hydroxyapatite is a naturally occurring form of the mineral calcium apatite—calcium, phosphorous, and oxygen—that grows in hexagonal crystals. Hydroxyapatite is the main mineral of which tooth enamel and dentine are composed off, as well as bones .Calcium Hydroxyapatite has  the formula Ca5(PO4)3(OH), but it is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. The OH ion can be replaced by fluoridechloride or carbonate, producing fluorapatite or chlorapatite.

The natural Calcium Hydroxypatite  limestone based media is   chemically activated in conjunction with aluminium.  The media is typically supplied as a moist media with particle size of average 1 mm. Pacific Water Technology has proven this media for various commercial applications for the removal of contaminants from potable and waste water.  Fluoride is removed from aqueous solutions  by fluoride ions displacing the hydroxide group in the mineral . This process is reversible, therefor enabling this media to be regenerated.  Heavy metals are also adsorbed by the media , therefor making  it a very versatile filtration media for removal of various contaminants.  The Calcium hydroxyapatite media has superior  performance to other media including bone char , fluoride specific ion exchange resins and activated alumina.

Hydroxyapatite  Features and Benefits

  • High capacity and shorter contact time
  • Very safe to use; no dissolution of toxic and hazardous substances
  • High efficiency, NEWDEF®1 can remove  up to 99% fluoride  in raw water.
  • Limited inhibition by other competing ions
  • Lower regeneration cost and simple regeneration process
  • Not only restricted to Fluoride ,but can remove iron and manganese as well
  • Can be regenerated.  More:

 

Below are the results from a trial performed with the media , using a two minute contact time . The water was spiked with various contaminant levels  ,exceeding what you would typically find in natural or potable water sources.

Contaminant:                       Percentage  Reduction:

Fluoride                                        99%

Lead                                               98%

Copper                                          99%

Arsenic                                          96%

Manganese                                    99%

Zinc                                                 99%

The required contact time compared to  activated alumina is  significantly shorter , therefor making this media much more practical and economical for  water filtration applications.

 

 

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