XAS STUDY OF ASO43- AND SEO42- SUBSTITUTED SCHWERTMANNITES

Synthetic schwertmannite samples with varying amounts of arsenate and selenate substituting for sulfate were examined by XAS methods in an a ttempt to characterize the location of the anion complexes. Selenate a ppears to both substitute directly for sulfate within tunnels in the s tructure, and sorb onto the outside of crystallites. No disruption of the basic structure appears with selenate substitution. However, arsen ate appears mainly to sorb to the outside of crystallites, destabilizi ng the structure and poisoning growth.