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

Journal Article · · Journal of Materials Research

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.

Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE). Solar Energy Technologies Office (EE-4S); USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
89233218CNA000001
OSTI ID:
1544698
Report Number(s):
LA-UR-19-22797
Journal Information:
Journal of Materials Research, Vol. 34, Issue 19; ISSN 0884-2914
Publisher:
Materials Research SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 12 works
Citation information provided by
Web of Science

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