title: Sulfur speciation in untreated and alkali treated ground-granulated blast furnace slag.
abstract: Reduced sulfur species in ground-granulated blast furnace slag (GGBFS) play an important role in immobilizing radionuclide contaminants in caustic cement-GGBFS mixtures via reductive precipitation reaction. However, sulfur (S) speciation and its stability in GGBFS have not been clearly understood. In this study, S speciation of GGBSF in alkaline radionuclide liquid waste simulant solutions was investigated using S K-edge X-ray absorption near edge structure spectroscopy (XANES) and powder X-ray diffraction (XRD) measurements. Although S mineralogy was not detectable by XRD due to the amorphous nature in GGBFS, XANES analysis revealed that GGBSF contained high concentration of sulfoxide (~57%), followed by S(0) (~37%), sulfate (~3.81%), and sulfonate (~2.33%). When GGBFS was reacted with anoxic or oxygenated alkali solutions, it retained most of sulfoxide with some changes in the fraction of elemental S, sulfonate and sulfate, indicating the involvement of reduced S species in the reductive precipitation of radionuclides. This study shows the presence of intermediate S valence species in GGBFS.
authors.affiliation: Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States. Electronic address: yarai@illinois.edu.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Arai
authors.affiliation: Department of Environmental Engineering and Earth Sciences, L.G. Rich Environmental Laboratory, 342 Computer Court, Anderson, SC 29625, United States.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Powell
authors.affiliation: Savannah River National Laboratory, Aiken, SC 29808, United States.
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Kaplan
keywords: Blast furnace slag; Slag; Sulfoxide; Sulfur speciation; XANES