This study examines the vaporization percentage and partitioning of heavy metals Cd, Pb and Zn during thermal treatment of wastes with added PVC, heavy metals or phosphate, and the efficiency of sorbents for removal of these metallic compounds in flue gas of an industrial solid waste incinerator. Firstly, vaporization experiments were carried out to determine the behavior of heavy metals during combustion under various conditions (type of waste, temperature, presence of chloride or phosphate ...). The experimental results show relatively high vaporization percentage of metallic compounds within fly ash and limestone matrix while heavy metals within sediments treated with phosphoric acid are less volatile. Vaporization of metals increases with increasing temperature and with chloride addition. The thermal behavior of the selected heavy metals and their removal by sorbents (sodium bicarbonate, activated carbon) was also studied in an industrial solid waste incinerator. These pilot scale experiments confirm that heavy metals are concentrated in fly ashes and cyclone residues, thus effectively controlling their release to the atmosphere.

We report the preparation of hydroxyapatite in powdered form by aqueous reaction of calcium nitrate or hydroxide with phosphate ion at room temperature. With a slow maturation step of 48 h avoiding heat, the resulting products show large specific surface areas above 150 m 2 /g. The specific surface areas also depend on stirring speed with a maximum observed with gentle mixing. Ageing causes a decrease in specific surface area which tends to stabilize near 100 m 2 /g following a 1 year period. The hydroxyapatite may be spray dried and conserve interesting physical properties for environmental applications.

The synthesis of hydroxyapatite is described starting from calcium carbonate and monoammoniumphosphate in stoichiometric amounts. The novel aspect concerns the reaction conditions which are simple mixing in water at ambient pressure and 60°C. The calcium carbonate solid phase slowly evolves CO 2 gas and buffers the solution at a pH value of 8.05 where hydroxyapatite precipitates. The main advantages of this reaction pathway are the absence of nitrate salts, the availability of the starting materials and the purity of the final product.