Interactions between calcium phosphate and heavy metal ions in aqueous solution

Synthetic and natural calcium phosphates were tested for removal metallic pollution in aqueous solution. Calcium phosphates with Ca/P ratio between 1,33 and 1,67 are fluently called apatite. They have a strong capacity to immobilize metallic ions when they are brought into contact with aqueous solutions. Ca2+ ions can substituted completely or partly by cations such as metallic ions (Ni2+; Cu2+; Co2+ and Cd2+). PO43- ions can be replaced by anions such as AsO43-, CO32-, ... etc. Sorption of Cu2+ and Ni2+ from aqueous solutions on natural (NA) and synthetic (SA) apatite was investigated in batch mode at 25 degrees C and 40 degrees C and over metal concentration range of 20-800 mg/L. Other experiments of co-precipitation metal-apatite (metal-TCP) were investigated in static mode at 25 degrees C. The results characterization of NA and SA apatite by FTIR, SEM, and ICP confirm their composition and apatitic structure. The results confirm efficiency of these calcium phosphates to decontaminate, by adsorption or co-precipitation, metallic ions such as Ni2+ or Cu2+ present in aqueous solution at concentrations between 20-800 mg/L.