STABILISATION OF HEAVY METALS FROM DREDGED SEDIMENT. TAILORING OF RESIDUE PROPERTIES

摘要

This study assesses the technology to treat heavy metals from dredged sediments using phosphoric acid (The Novosol~® process, developed by Solvay ) with the goal of converting metals, mainly Pb, Cd, Zn and Cu to insoluble metallic phosphates. The effectiveness of the treatment was evaluated by performing the chemical reaction in a tubular reactor, followed by convective drying and maturation of the treated sediment at ambient temperature and finally thermal destruction of the organic matter by calcinations (500°C-700°C). Selected variables (acid concentration, volume fraction of solids, flow rate, drying and calcination temperature and time) were investigated. Laboratory scale experiments were carried out with various combinations of these parameters. The influence of the quantity of acid on drying times, the physical property of the sediment and the stabilization of the heavy metals are discussed.