A B S T R A C TThe sorption of divalent copper and nickel ions from aqueous solutions on natural and synthetic hydroxyapatites was investigated in batch mode at 25 and 40˚C and over metal concentration range of 20-800 mg/L. Effect of initial pH solution was also investigated for two values pH 4.5 and pH 6. The sorption equilibrium data were well fitted by Langmuir's model. Both hydroxyapatites are efficient to remove copper and nickel ions, despite their different compositions and morphologies. The sorption mechanism involved an ion exchange between calcium ions of hydroxyapatite and metal ions along with pronounced precipitation, particularly in case of the synthetic hydroxyapatite. Higher sorption efficiencies were observed with the synthetic hydroxyapatite towards copper ions, similar values for both synthetic and natural hydroxyapatites were found towards Ni ion's sorption and lower values at pH 6.

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Abstract. 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. Ca 2+ ions can substituted completely or partly by cations such as metallic ions (Ni 2+ ; Cu 2+ ; Co 2+ and Cd 2+ ). PO 3− 4 ions can be replaced by anions such as AsO 3− 4 , CO 2− 3 , . . . etc. Sorption of Cu 2+ and Ni 2+ from aqueous solutions on natural (NA) and synthetic (SA) apatite was investigated in batch mode at 25 • C and 40 • 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 • 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 Ni 2+ or Cu 2+ present in aqueous solution at concentrations between 20-800 mg/L.

Permeable reactive barrier (PRB) containing zero valent iron (ZVI), plaster and additives to make a porous composite structure was tested to remove an organic nitro compound as model pollutant. An aqueous solution of 4-nitroaniline (PNA) was passed through a porous plaster composite column and chemical degradation quantified by UV-Vis spectroscopy. PNA was reduced to p-phenylenediamine and the rate of the reduction was strongly related to ZVI amount, pollutant volume, and the contact rate with metal particles. The parameters could be controlled by reactor design and operation. The columns were made to test the materials for making precast plaster blocks containing ZVI. The results showed that such porous plaster blocks could be efficient as retaining walls for environmental applications.