Lawrence Berkeley National Laboratory

Schwertmannite is a poorly crystallized iron oxyhydroxide with essential structural sulfate that can be a major component in acid mine drainage environments. Original characterization work concluded that the sulfate was largely contained within tunnels of an ordered akaganeite-like structure based on powder XRD, analysis of IR spectra, and sulfate extraction procedures [1]. Since the original description, problems have emerged with the nature of the tunnel sulfate, and with the interpretation of the IR spectra. Other related work has shown that it is now possible to determine sulfate-iron oxide inner sphere binding unambiguously from the S K-edge XANES spectrum. Hence a reassessment of the evidence for the original schwertmannite structure was deemed necessary and timely.