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.

One-step thermal synthesis of sodium trimetaphosphate (STM) from sodium chloride and 85 wt % orthophosphoric acid as starting materials was investigated. The reaction temperature and volume-mean diameter of sodium chloride influenced strongly the elimination of chloride and the selectivity in STM. STM of high quality (99%) was obtained at 600°C from fine powder of sodium chloride. Hydrochloric acid was the only byproduct of the reaction.

Dredging of sediments is necessary in order to maintain maritime activities and for flood prevention. However the increased industrial activities are causing accumulation of pollutants in the sediments. The main contaminants are heavy metals and organic compounds. Because of the cost of storage, treatment and valorization can be economically sound. This study focuses on the technology to treat heavy metals from dredged sediments using phosphoric acid (H3PO4) (the Novosol® process developed by Solvay company) with a goal to stabilize heavy metals by capturing them in calcium phosphate matrix and to destroy organic matter by calcination at 650°C. Several studies have been conducted in this field. The stabilized materials obtained have been used in civil engineering. However these studies have never assessed the effect of the composition of the phosphoric acid on the treatment. In this paper the effect of two types of phosphoric acids with various composition and origins were compared. The investigation focuses on the effect of the phosphoric acids on the environmental behavior of metals and on the geotechnical properties of the dredged sediment.