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However, during the defluoridation process the hydroxyapatite dissolves, and increases the pH and phosphate ion concentration which makes the defluoridated water unfit for drinking. [46] Recently, a ″calcium amended-hydroxyapatite″ defluoridation technique was suggested to overcome the phosphate leaching from hydroxyapatite. [ 46 ]
Amorphous calcium phosphate in combination with casein phosphopeptide has been used as a dental treatment to treat incipient dental decay. ACP sees its main use as an occluding agent, which aids in reducing sensitivity. Studies have shown that it does form a remineralized phase of hydroxyapatite consistent with the natural enamel.
The alum dosage is also insufficient to cause toxicity in humans, and is often similar to alum doses used in conventional drinking water treatment. [8] To reduce negative biological effects, the accepted limit for dissolved aluminum concentrations in a water body is 50 μg Al/L and pH should be restricted to a range of 5.5-9. [2]
Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted bonding with calcium ions. Soft water also extends the lifetime of plumbing by reducing or eliminating scale build-up in pipes
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
Negatives include higher costs and it skilled labour. This process is not suitable for water with high salinity. [2] Calcium amended-hydroxyapatite is the most recent defluoridation technique in which aqueous calcium is amended to the fluoride contaminated water prior to contact with uncalcined synthetic hydroxyapatite adsorbent. [8]
The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca 2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well.
Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH −, F − and Cl − ion, respectively, in the crystal. The formula of the admixture of the three most common endmembers is written as Ca 10 ( PO 4 ) 6 (OH,F,Cl) 2 , and the crystal unit cell formulae of the ...