Improved precision in As speciation analysis with HERFD-XANES at the As K-edge: the case of As speciation in mine waste

In this study, linear combination fitting (LCF) was performed on synthetic spectra generated from mixtures of eight measured reference compounds for both HERFD-XANES and transmission-detected XANES to evaluate the improvement in quantitative speciation with HERFD-XANES spectra. The reference compounds arsenolite (As2O3), orpiment (As2S3), getchellite (AsSbS3), arsenopyrite (FeAsS), ka ň kite (FeAsO4 · 3.5H2O), scorodite (FeAsO4 · 2H2O), sodium arsenate (Na3AsO4), and realgar (As4S4) were selected for their importance in mine waste systems. Statistical methods of principal component analysis and target transformation were employed to determine whether HERFD improves identification of the components in a dataset of mixtures of reference compounds. LCF was performed on HERFD- and total fluorescence yield (TFY)-XANES spectra collected from mine waste samples. Arsenopyrite, arsenolite, orpiment, and sodium arsenate were more accurately identified in the synthetic HERFD-XANES spectra compared with the transmission-XANES spectra. In mine waste samples containing arsenopyrite and either scorodite or ka ň kite, LCF with HERFD-XANES measurements resulted in fits with smaller R-factors than concurrently collected TFY measurements. The improved accuracy of HERFD-XANES analysis may provide enhanced delineation of As phases controlling biogeochemical reactions in mine wastes, contaminated soils, and remediation systems.

Source: Journal of Synchrotron Radiation - August 11, 2022 Category: Physics Authors: Saurette, E.M. Frinfrock, Y.Z. Verbuyst, B. Blowes, D.W. McBeth, J.M. Ptacek, C.J. Tags: HERFD-XANES geochemistry mine waste arsenic linear combination fitting research papers Source Type: research