Mode of occurrence of arsenic in four US coals

An integrated analytical approach has been used to determine the mode of oc currence of arsenic in samples of four widely used US coals: the Pittsburgh , Illinois #6, Elkhorn/Hazard, and Wyodak. Results from selective leaching, X-ray absorption fine structure (XAFS) spectroscopy, and electron micropro be analysis show that pyrite is the principal source of arsenic in the thre e bituminous coals, but the concentration of As in pyrite varies widely. Th e Wyodak sample contains very little pyrite; its arsenic appears to be prim arily associated with organics, as As3+, or as arsenate. Significant (10-40 %) fractions of arsenate, derived from pyrite oxidation, are also present i n the three bituminous coal samples. This information is essential in devel oping predictive models for arsenic behavior during coal combustion and in other environmental settings. Published by Elsevier Science B.V.