Fixation des ions sulfate et cuivre (II) sur des surfaces de type Oxy-hydroxyde . Cas du ferrihydrite.

Abstract

The present work is a contribution to the evaluation of the adsorbing properties of hydrous iron oxide (Ferrihydrite) in conditions similar to natural systems, by the adsorption of sulfate and copper(II) ions. A series of hydrous iron oxide samples were prepared by homogeneous precipitation from FeCb solution in the presence of SO/' ions in the first part and in the presence of Cu(II) in the second. Macroscopic studies and solid samples analysis are performed. Sulfate ions uptake is highly pH dependent. It reaches its maximum at low pH. The effect of the presence of divers cations is observed at pH>5.5. With the exception of acetate ions, the presence of the used anions decreases the sulphate adsorption. The results of DRX, DSC and IR analyses of solid samples, show the strong interaction of sulfate ions with the hydrous iron oxide. The ions adsorb by inner sphere complex mechanism except in the presence of phosphate ions, where the formation of outer sphere complex is more probable. Copper coprecipitation with the hydrous iron oxide is pH dependent. It is significant at low pH, especially in the presence of sulfate ions. The presence of lead and zinc has a moderate effect on the coprecipitation of copper. The results obtained by desorption experiments and those of solid samples analyses, show that the interaction of copper with hydrous iron oxide is in relation to pH.