Evaluation of mercury stabilization mechanisms by sulfurized biochars determined using X-ray absorption spectroscopy
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Date
2018-04-05
Authors
Liu, Peng
Ptacek, Carol J.
Elena, Krista M. A.
Blowes, David W.
Gould, W. Douglas
Finfrock, Y. Zou
Wang, Alana O.
Landis, Richard C.
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
The application of biochar to treat mercury (Hg) in the environment is being proposed on an increasing basis due to its widespread availability and cost effectiveness. However, the efficiency of Hg removal by biochars is variable due to differences in source material composition. In this study, a series of batch tests were conducted to evaluate the effectiveness of sulfurized biochars (calcium polysulfide and a dimercapto-related compound, respectively) for Hg removal; Hg-loaded biochars were then characterized using synchrotron-based techniques. Concentrations of Hg decreased by >99.5% in solutions containing the sulfurized biochars. Sulfur X-ray absorption near-edge structure (XANES) analyses indicate a polysulfur-like structure in polysulfide-sulfurized biochar and a thiol-like structure (shifted compared to dimercapto) in the dimercapto-sulfurized biochar. Micro-X-ray fluorescence (μ-XRF) mapping and confocal X-ray micro-fluorescence imaging (CXMFI) analyses indicate Hg is distributed primarily on the edges of sulfurized biochar and throughout unmodified biochar particles. Hg extended X-ray absorption fine structure (EXAFS) analyses show Hg in enriched areas is bound to chlorine (Cl) in the unmodified biochar and to S in sulfurized biochars. These results indicate that Hg removal efficiency is enhanced after sulfurization through the formation of strong bonds (Hg-S) with S-functional groups in the sulfurized biochars.
Description
The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.jhazmat.2017.12.051 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Keywords
Biochar, Confocal X-ray micro-fluorescence imaging, Mercury, Polysulfur, X-ray absorption spectroscopy