Synthetic Hydroxyapatites Employed as Inorganic Cation-exchangers

Abstract

The manner in which ions such as Cd2+, Zn2+, Ni2+, Mg2+ and Ba2+ in aqueous solution are removed by synthetic hydroxyapatites has been probed by using both batch and column methods. The behaviour is not merely an adsorption effect but a type of ion-exchange reaction between the ions in solution and the Ca2+ ions of the apatites. The ranking of the ions according to amount exchanged was as follows: Cd2+, Zn2+ > Ni2+ > Ba2+, Mg2+. These results suggest that the apatites have a selectivity for metallic cations and can be employed as a new inorganic cation-exchanger for recovering valuable ions in waste water.