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Title: Progressive Oxidation of Pyrite in Five Bituminous Coal Samples: An As XANES and 57Fe Mossbauer Spectroscopic Study

Abstract

Naturally occurring pyrite commonly contains minor substituted metals and metalloids (As, Se, Hg, Cu, Ni, etc.) that can be released to the environment as a result of its weathering. Arsenic, often the most abundant minor constituent in pyrite, is a sensitive monitor of progressive pyrite oxidation in coal. To test the effect of pyrite composition and environmental parameters on the rate and extent of pyrite oxidation in coal, splits of five bituminous coal samples having differing amounts of pyrite and extents of As substitution in the pyrite, were exposed to a range of simulated weathering conditions over a period of 17 months. Samples investigated include a Springfield coal from Indiana (whole coal pyritic S = 2.13 wt.%; As in pyrite = detection limit (d.l.) to 0.06 wt.%), two Pittsburgh coal samples from West Virginia (pyritic S = 1.32-1.58 wt.%; As in pyrite = d.l. to 0.34 wt.%), and two samples from the Warrior Basin, Alabama (pyritic S = 0.26-0.27 wt.%; As in pyrite = d.l. to 2.72 wt.%). Samples were collected from active mine faces, and expected differences in the concentration of As in pyrite were confirmed by electron microprobe analysis. Experimental weathering conditions in test chambers were maintained asmore » follows: (1) dry Ar atmosphere; (2) dry O{sub 2} atmosphere; (3) room atmosphere (relative humidity {approx}20-60%); and (4) room atmosphere with samples wetted periodically with double-distilled water. Sample splits were removed after one month, nine months, and 17 months to monitor the extent of As and Fe oxidation using As X-ray absorption near-edge structure (XANES) spectroscopy and {sup 57}Fe Mossbauer spectroscopy, respectively. Arsenic XANES spectroscopy shows progressive oxidation of pyritic As to arsenate, with wetted samples showing the most rapid oxidation. {sup 57}Fe Mossbauer spectroscopy also shows a much greater proportion of Fe{sup 3+} forms (jarosite, Fe{sup 3+} sulfate, FeOOH) for samples stored under wet conditions, but much less difference among samples stored under dry conditions in different atmospheres. The air-wet experiments show evidence of pyrite re-precipitation from soluble ferric sulfates, with As retention in the jarosite phase. Extents of As and Fe oxidation were similar for samples having differing As substitution in pyrite, suggesting that environmental conditions outweigh the composition and amount of pyrite as factors influencing the oxidation rate of Fe sulfides in coal.« less

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930388
Report Number(s):
BNL-81110-2008-JA
Journal ID: ISSN 0883-2927; APPGEY; TRN: US200904%%670
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Geochemistry; Journal Volume: 22; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; ABSORPTION; ALABAMA; ARSENIC; BITUMINOUS COAL; COAL; ELECTRON MICROPROBE ANALYSIS; HUMIDITY; INDIANA; MOESSBAUER EFFECT; OXIDATION; PITTSBURGH; PYRITE; SEMIMETALS; SENSITIVITY; SPECTROSCOPY; SULFATES; SULFIDES; WATER; WEATHERING; WEST VIRGINIA; national synchrotron light source

Citation Formats

Kolker,A., and Huggins, F. Progressive Oxidation of Pyrite in Five Bituminous Coal Samples: An As XANES and 57Fe Mossbauer Spectroscopic Study. United States: N. p., 2007. Web. doi:10.1016/j.apgeochem.2006.10.006.
Kolker,A., & Huggins, F. Progressive Oxidation of Pyrite in Five Bituminous Coal Samples: An As XANES and 57Fe Mossbauer Spectroscopic Study. United States. doi:10.1016/j.apgeochem.2006.10.006.
Kolker,A., and Huggins, F. Mon . "Progressive Oxidation of Pyrite in Five Bituminous Coal Samples: An As XANES and 57Fe Mossbauer Spectroscopic Study". United States. doi:10.1016/j.apgeochem.2006.10.006.
@article{osti_930388,
title = {Progressive Oxidation of Pyrite in Five Bituminous Coal Samples: An As XANES and 57Fe Mossbauer Spectroscopic Study},
author = {Kolker,A. and Huggins, F.},
abstractNote = {Naturally occurring pyrite commonly contains minor substituted metals and metalloids (As, Se, Hg, Cu, Ni, etc.) that can be released to the environment as a result of its weathering. Arsenic, often the most abundant minor constituent in pyrite, is a sensitive monitor of progressive pyrite oxidation in coal. To test the effect of pyrite composition and environmental parameters on the rate and extent of pyrite oxidation in coal, splits of five bituminous coal samples having differing amounts of pyrite and extents of As substitution in the pyrite, were exposed to a range of simulated weathering conditions over a period of 17 months. Samples investigated include a Springfield coal from Indiana (whole coal pyritic S = 2.13 wt.%; As in pyrite = detection limit (d.l.) to 0.06 wt.%), two Pittsburgh coal samples from West Virginia (pyritic S = 1.32-1.58 wt.%; As in pyrite = d.l. to 0.34 wt.%), and two samples from the Warrior Basin, Alabama (pyritic S = 0.26-0.27 wt.%; As in pyrite = d.l. to 2.72 wt.%). Samples were collected from active mine faces, and expected differences in the concentration of As in pyrite were confirmed by electron microprobe analysis. Experimental weathering conditions in test chambers were maintained as follows: (1) dry Ar atmosphere; (2) dry O{sub 2} atmosphere; (3) room atmosphere (relative humidity {approx}20-60%); and (4) room atmosphere with samples wetted periodically with double-distilled water. Sample splits were removed after one month, nine months, and 17 months to monitor the extent of As and Fe oxidation using As X-ray absorption near-edge structure (XANES) spectroscopy and {sup 57}Fe Mossbauer spectroscopy, respectively. Arsenic XANES spectroscopy shows progressive oxidation of pyritic As to arsenate, with wetted samples showing the most rapid oxidation. {sup 57}Fe Mossbauer spectroscopy also shows a much greater proportion of Fe{sup 3+} forms (jarosite, Fe{sup 3+} sulfate, FeOOH) for samples stored under wet conditions, but much less difference among samples stored under dry conditions in different atmospheres. The air-wet experiments show evidence of pyrite re-precipitation from soluble ferric sulfates, with As retention in the jarosite phase. Extents of As and Fe oxidation were similar for samples having differing As substitution in pyrite, suggesting that environmental conditions outweigh the composition and amount of pyrite as factors influencing the oxidation rate of Fe sulfides in coal.},
doi = {10.1016/j.apgeochem.2006.10.006},
journal = {Applied Geochemistry},
number = 4,
volume = 22,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}