Influence de l'or sur la cristallisation des oxy-hydroxydes de fer

An experimental approach is used to characterize the role of gold during the formation of goethite and hematite from ferrihydrite. The results show that metallic gold colloids play a role during the maturation of the gel at pH 7. In such conditions, the formation of goethite is retarded in presence of colloidal gold. Gold does not affect the formation of hematite. Dissolution/reprecipitation processes responsible for the formation of goethite are slowed down by electrostatic effects of the negative gold colloids on the concentration of Fe(OH) 4 - which could be a rate limiting factor for goethite precipitation. Also Au-O-Fe surface complexes could slow down the formation of goethite.