| Abstract: | The fixation of slightly soluble substances on inert carriers offers the possibility to examine the exchange of heavy metals at these phases under dynamic conditions. Investigations are presented for the exchange of Zinc under various conditions (pH, different concentrations of other cations such as Na+ and Ca2+ or of NTA as a chelating agent) on fixed MnO2-hydrate, Fe(OH3), CaCO3 and a natural clay-slate. Batch-experiments showed that all phases are able to sorb Zinc with MnO2-hydrate as the best sorbent for this metal (highest sorption constant and capacity). Column desorption experiments demonstrate that a decrease of the pH of the aqueous phase or an addition of NTA remobilise Zinc from MnO2-hydrate, Fe(OH)3, CaCO3 and also from the clay-slate. The same effect of releasing sorbed metal (with exception of the CaCO3-phase) show Na+ or Ca2+ containing solutions. Therefore Zinc is bonded under natural conditions on the oxihydrates and the clay-slate in a labile, ion-exchangeable form in contrast to CaCO3, on which Zinc is sorbed probably as the carbonate. |
