CHROMIUM SPECIATION IN HAZARDOUS, CEMENT-BASED WASTE FORMS

XANES and EXAFS techniques were used to determine the oxidation states and local structural environment of Cr in cement-based waste forms. R esults show that Cr in untreated Portland cement formulations remains as toxic Cr6+, while slag additives to the cement reduce Cr6+ to the l ess toxic, less mobile Cr3+ species. EXAFS analysis suggests that the Cr6+ species is surrounded by four nearest oxygen atoms, while the red uced Cr3+ species is surrounded by six oxygen atoms. The fitted Cr-O b ond lengths for Cr6+ and Cr3+ species are around 1.66 and 1.98 Angstro m, respectively.