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Title: Thermal desulfurization of pyrite: An in situ high-T neutron diffraction and DTA–TGA study

Abstract

To study thermal desulfurization of pyrite (FeS 2), we conducted in situ neutron diffraction experiments in the temperature range 298–1073 K. Additionally, on heating, pyrite remained stable up to 773 K, at which it started to decompose into pyrrhotite (Fe 1-xS) and S 2 gas. Rietveld analysis of the neutron data from 298 to 773 K allowed determination of the thermal expansion coefficient of pyrite (space group Pa$$\overline{3}$$) to be α V = 3.7456 × 10 -5 K -1, which largely results from the expansion of the Fe–S bond. With further increase in temperature to 1073 K, all the pyrite transformed to pyrrhotite (Fe 1-xS) at 873 K. Unit-cell parameters of Fe 1-xS (space group P6 3/mmc) increase on heating and decrease on cooling. However, the rates in cell expansion are larger than those in contraction. This hysteresis behavior can be attributed to continuous desulfurization of pyrrhotite (i.e., x in Fe 1-xS decreases) with increasing temperature until the stoichiometric troilite (FeS) was formed at 1073 K. On cooling, troilite underwent a magnetic transition to an orthorhombic structure (space group Pnma) between 473 and 573 K. In addition, using differential thermal analysis (DTA) and thermogravimetric analysis (TGA) implemented with a differential scanning calorimeter, we performed kinetic measurements of pyrite decomposition. Finally, detailed peak profile and Arrhenius (k = A exp(-E a/RT)) analyses yielded an activation energy E a of 302.3 ± 28.6 kJ/mol (based on DTA data) or 302.5 ± 26.4 kJ/mol (based on TGA data) and a ln(A) of 35.3 ± 0.1.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1];  [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE). Solar Energy Technologies Office (EE-4S); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1544698
Report Number(s):
LA-UR-19-22797
Journal ID: ISSN 0884-2914
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Materials Research
Additional Journal Information:
Journal Volume: 34; Journal Issue: 19; Journal ID: ISSN 0884-2914
Publisher:
Materials Research Society
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 36 MATERIALS SCIENCE; pyrite; pyrrhotite; troilite; neutron diffraction; deferential thermal analysis; thermogravimetric analysis; desulfurization; thermal expansion; crystal structure; phase transformation; kinetics

Citation Formats

Xu, Hongwu, Guo, Xiaofeng, Seaman, Lani Anne, Harrison, Aaron J., Obrey, Stephen J., and Page, Katharine. Thermal desulfurization of pyrite: An in situ high-T neutron diffraction and DTA–TGA study. United States: N. p., 2019. Web. doi:10.1557/jmr.2019.185.
Xu, Hongwu, Guo, Xiaofeng, Seaman, Lani Anne, Harrison, Aaron J., Obrey, Stephen J., & Page, Katharine. Thermal desulfurization of pyrite: An in situ high-T neutron diffraction and DTA–TGA study. United States. doi:10.1557/jmr.2019.185.
Xu, Hongwu, Guo, Xiaofeng, Seaman, Lani Anne, Harrison, Aaron J., Obrey, Stephen J., and Page, Katharine. Tue . "Thermal desulfurization of pyrite: An in situ high-T neutron diffraction and DTA–TGA study". United States. doi:10.1557/jmr.2019.185.
@article{osti_1544698,
title = {Thermal desulfurization of pyrite: An in situ high-T neutron diffraction and DTA–TGA study},
author = {Xu, Hongwu and Guo, Xiaofeng and Seaman, Lani Anne and Harrison, Aaron J. and Obrey, Stephen J. and Page, Katharine},
abstractNote = {To study thermal desulfurization of pyrite (FeS2), we conducted in situ neutron diffraction experiments in the temperature range 298–1073 K. Additionally, on heating, pyrite remained stable up to 773 K, at which it started to decompose into pyrrhotite (Fe1-xS) and S2 gas. Rietveld analysis of the neutron data from 298 to 773 K allowed determination of the thermal expansion coefficient of pyrite (space group Pa$\overline{3}$) to be αV = 3.7456 × 10-5 K-1, which largely results from the expansion of the Fe–S bond. With further increase in temperature to 1073 K, all the pyrite transformed to pyrrhotite (Fe1-xS) at 873 K. Unit-cell parameters of Fe1-xS (space group P63/mmc) increase on heating and decrease on cooling. However, the rates in cell expansion are larger than those in contraction. This hysteresis behavior can be attributed to continuous desulfurization of pyrrhotite (i.e., x in Fe1-xS decreases) with increasing temperature until the stoichiometric troilite (FeS) was formed at 1073 K. On cooling, troilite underwent a magnetic transition to an orthorhombic structure (space group Pnma) between 473 and 573 K. In addition, using differential thermal analysis (DTA) and thermogravimetric analysis (TGA) implemented with a differential scanning calorimeter, we performed kinetic measurements of pyrite decomposition. Finally, detailed peak profile and Arrhenius (k = A exp(-Ea/RT)) analyses yielded an activation energy Ea of 302.3 ± 28.6 kJ/mol (based on DTA data) or 302.5 ± 26.4 kJ/mol (based on TGA data) and a ln(A) of 35.3 ± 0.1.},
doi = {10.1557/jmr.2019.185},
journal = {Journal of Materials Research},
number = 19,
volume = 34,
place = {United States},
year = {2019},
month = {6}
}

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