Send to

Choose Destination
Environ Sci Technol. 2001 Mar 15;35(6):1157-63.

In situ spectroscopic and solution analyses of the reductive dissolution of MnO2 by Fe(II).

Author information

Department of Hydrology and Water Resources, The University of Arizona, Tucson 85721-0011, USA.


The reductive dissolution of MnO2 by Fe(II) under conditions simulating acid mine drainage (pH 3, 100 mM SO4(2-)) was investigated by utilizing a flow-through reaction cell and synchrotron X-ray absorption spectroscopy. This configuration allows collection of in situ, real-time X-ray absorption near-edge structure (XANES) spectra and bulk solution samples. Analysis of the solution chemistry suggests that the reaction mechanism changed (decreased reaction rate) as MnO2 was reduced and Fe(III) precipitated, primarily as ferrihydrite. Simultaneously, we observed an additional phase, with the local structure of jacobsite (MnFe2O4), in the Mn XANES spectra of reactants and products. The X-ray absorbance of this intermediate phase increased during the experiment, implying an increase in concentration. The presence of this phase, which probably formed as a surface coating, helps to explain the reduced rate of dissolution of manganese(IV) oxide. In natural environments affected by acid mine drainage, the formation of complex intermediate solid phases on mineral surfaces undergoing reductive dissolution may likewise influence the rate of release of metals to solution.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for American Chemical Society
Loading ...
Support Center