Evaluating the effect and fate of impurities during pyritization of nanocrystalline FeS

Abstract

The interaction of FeS with various metals and metalloids is primarily facilitated by its extreme small crystallite size, at. structure, and surface charge properties. The mechanisms for incorporation of minor and trace elements (i.e., impurities) in the initial FeS ppt. and during the subsequent transformation of FeS to pyrite (FeS2) are not entirely clear. These processes are important because incorporation of impurities in sedimentary FeS2, a relatively insol. and thermodynamically stable mineral phase under reducing conditions, directly affects their geochem. cycling. A recent characterization of the initial FeS ppt. using synchrotron radiation and advanced XRD techniques indicates that this phase is nanocryst. and has an at. structure nearly identical to cryst. mackinawite. By conducting hydrothermal aging expts. in situ the structural transformation of FeS to FeS2 can be tracked to assess the effect and fate of impurities during these reactions. These expts. are carried out using new techniques developed to avoid compromising the reaction conditions.