Open AccessBeam‐induced redox transformation of arsenic during As K ‐edge XAS measurements: availability of reducing or oxidizing agents and As speciation
Author(s) -
Han Young-Soo,
Jeong Hoon Young,
Hyun Sung Pil,
Hayes Kim F.,
Chon Chul-Min
Publication year - 2018
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s1600577518002576
Subject(s) - oxidizing agent , arsenic , x ray absorption spectroscopy , redox , genetic algorithm , transformation (genetics) , environmental chemistry , enhanced data rates for gsm evolution , chemistry , inorganic chemistry , materials science , absorption spectroscopy , metallurgy , computer science , biology , physics , optics , evolutionary biology , biochemistry , organic chemistry , telecommunications , gene
During X‐ray absorption spectroscopy (XAS) measurements of arsenic (As), beam‐induced redox transformation is often observed. In this study, the As species immobilized by poorly crystallized mackinawite (FeS) was assessed for the susceptibility to beam‐induced redox reactions as a function of sample properties including the redox state of FeS and the solid‐phase As speciation. The beam‐induced oxidation of reduced As species was found to be mediated by the atmospheric O 2 and the oxidation products of FeS [ e.g. Fe(III) (oxyhydr)oxides and intermediate sulfurs]. Regardless of the redox state of FeS, both arsenic sulfide and surface‐complexed As(III) readily underwent the photo‐oxidation upon exposure to the atmospheric O 2 during XAS measurements. With strict O 2 exclusion, however, both As(0) and arsenic sulfide were less prone to the photo‐oxidation by Fe(III) (oxyhydr)oxides than NaAsO 2 and/or surface‐complexed As(III). In case of unaerated As(V)‐reacted FeS samples, surface‐complexed As(V) was photocatalytically reduced during XAS measurements, but arsenic sulfide did not undergo the photo‐reduction.