Peggy A. O’Day Timothy L. Corley Martha H. Conklin John E. Villinski 2001 <p><span>The reductive dissolution of MnO</span>₂<span> by Fe(II) under conditions simulating acid mine drainage (pH 3, 100 mM SO</span>₄²^-<span>) 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 MnO</span>₂<span> was reduced and Fe(III) precipitated, primarily as ferrihydrite. Simultaneously, we observed an additional phase, with the local structure of jacobsite (MnFe</span>₂<span>O</span>₄<span>), 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.</span></p> application/pdf 10.1021/es001356d en American Chemical Society In situ spectroscopic and solution analyses of the reductive dissolution of Mn02 by Fe(II) article