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2017-06-26 - Colloque/Présentation - poster - Anglais - 1 page(s)

Chenoy Louise , De Weireld Guy , Hantson Anne-Lise , "Multi surface modeling of trace metals behavior in treated dredged sediment: experimental study and modeling of metals retention on artificial assemblage of natural sorbent phases." in AquaConSoil 2017-Sustainable Use and Management of Soil, Sediment and Water Resources, Lyon, France, 2017

  • Codes CREF : Environnement et pollution (DI3840)
  • Unités de recherche UMONS : Génie des Procédés chimiques et biochimiques (F505), Thermodynamique, Physique mathématique (F506)
  • Instituts UMONS : Institut des Sciences et du Management des Risques (Risques)
Texte intégral :

Abstract(s) :

(Anglais) In Walloon Region dredged sediments are classified as waste materials and must eventually (depending on their pollutant content and release) be treated before valorization or disposal. During several years 6 million of m³ of sediments have been accumulated in waterways, whose about 65% are polluted by heavy metals or organic compounds. Over the past few years SOLINDUS and VALSOLINDUS projects aimed to assess the feasibility of sediments treatment and reuse. Considering that contaminants are generally concentrated in fine fractions, the treatment developed consists in a mineralurgic process to separate unpolluted coarse fractions (> 63 µm) from polluted fine fractions (silt fraction 15-63 µm and fine fraction <15µm). An additional flotation step is then applied to the silt fraction to attempt to further purify it. In a previous work, three samples of sediment silt fraction were characterized and leaching behavior of trace metals (Zn, Cd, Pb, Cu, Ni) was studied. A multi surface model was constructed with PHREEQC v.3.0. in order to improve the comprehension of metals retention phenomena. This comprehension is of importance to improve the treatment and evaluate environmental risks linked to further sediment reuse. The geochemical model combines thermodynamic models for inorganic speciation and dissolution/precipitation of mineral phases with ion binding models to account for metals retention on the phases constituting the sediments. The generalized 2-layer model (GTLM) of Dzombak and Morel is used to model binding to iron and aluminum oxides, the Windermere Humic Aqueous Model (WHAM) VI for binding to organic matter and an ion exchange model for binding to clays. This modeling approach supposes additivity of sorption on the different phases. At this time, results of modeling represents pretty well the general behavior of trace metals in function of pH. However, the model could be improved. Indeed, real samples of sediments are complex mixtures and their accurate characterization in order to use ion-binding models is difficult. This study aims to test the modeling approach against experimental data of metals sorption to artificial assemblages of well characterized phases. The first studied system will be constituted of synthetic amorphous iron oxide which is according to the model results the preponderant sorbent phase in the sediments studied. Batch sorption experiments will be conducted firstly with Zn and Pb (alone and in mixture) as they are the most problematic trace metals in the sediment samples. The influence of quartz and calcite will be also assessed like these phases are present in large quantities in sediments. Pure clays or organic matter (purified humic or fulvic acids) could also be studied separately and further included in the artificial assemblage.