skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Semiconductor electrochemistry coal pyrite. Quarterly technical progress report, October--December 1994

Abstract

Pyrite dissolution in acidic solution was found to involve both electrochemical oxidation and chemical decomposition. The mechanism of chemical decomposition of pyrite in acidic solution may involve surface complexation of hydrogen ions. The anodic current of pyrite was relatively small in non-aqueous solution (acetonitrile) compared with that in aqueous solution. The implication is that the direct reaction of holes with S{sub 2}{sup 2{minus}} in the pyrite lattice was not significant and that the dissolution of pyrite required the presence of water. The anodic dissolution product was elemental sulfur which was detected by X-ray diffraction.

Authors:
;
Publication Date:
Research Org.:
Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
211417
Report Number(s):
DOE/PC/91303-T17
ON: DE96008549
DOE Contract Number:
FG22-91PC91303
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jan 1995
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; 40 CHEMISTRY; PYRITE; DISSOLUTION; ELECTROCHEMISTRY; PH VALUE; X-RAY DIFFRACTION; COAL; CLEANING; DESULFURIZATION; PROGRESS REPORT; ELECTRODES; EXPERIMENTAL DATA

Citation Formats

Osseo-Asare, K., and Wei, D. Semiconductor electrochemistry coal pyrite. Quarterly technical progress report, October--December 1994. United States: N. p., 1995. Web. doi:10.2172/211417.
Copy to clipboard
Osseo-Asare, K., & Wei, D. Semiconductor electrochemistry coal pyrite. Quarterly technical progress report, October--December 1994. United States. doi:10.2172/211417.
Copy to clipboard
Osseo-Asare, K., and Wei, D. Sun . "Semiconductor electrochemistry coal pyrite. Quarterly technical progress report, October--December 1994". United States. doi:10.2172/211417. https://www.osti.gov/servlets/purl/211417.
Copy to clipboard
@article{osti_211417,
title = {Semiconductor electrochemistry coal pyrite. Quarterly technical progress report, October--December 1994},
author = {Osseo-Asare, K. and Wei, D.},
abstractNote = {Pyrite dissolution in acidic solution was found to involve both electrochemical oxidation and chemical decomposition. The mechanism of chemical decomposition of pyrite in acidic solution may involve surface complexation of hydrogen ions. The anodic current of pyrite was relatively small in non-aqueous solution (acetonitrile) compared with that in aqueous solution. The implication is that the direct reaction of holes with S{sub 2}{sup 2{minus}} in the pyrite lattice was not significant and that the dissolution of pyrite required the presence of water. The anodic dissolution product was elemental sulfur which was detected by X-ray diffraction.},
doi = {10.2172/211417},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 1995},
month = {Sun Jan 01 00:00:00 EST 1995}
}
Copy to clipboard
Technical Report:
View Technical Report (1.76 MB)
DOI:  10.2172/211417
Save / Share:
Export Metadata
Save to My Library
You must Sign In or Create an Account in order to save documents to your library.

  • ;
    This project seeks to advance the fundamental understanding of the physics-chemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid minedrainage. A novel approach to the study of pyrite aqueous electrochemistry is proposed, based on the use of both synthetic and natural ( i.e. coal-derived) pyrite specimens, the utilization of.pyrite both in the form of micro (i.e. colloidal and subcolloidal) and macro (i.e. rotating ring disk) electrodes, and the application of in-situ direct electroanalytical and spectroelectrochemical characterization techniques. The kinetic study of the reaction between sulfide and ferrous ions in solution suggested thatmore » the black species formed initially is FeHS{sup +} intermediate. To farther confirm this mechanism, the experiments aimed at establishing the stoichiometry for the intermediate were carried out thermodynamically with a stopped-flow spectrophotometric technique. The results showed that the mole ratio of H{sup {minus}}/Fe{sup 2+} is 1 to 1 for the intermediate product, which is in good agreement with the kinetic results previously obtained. Furthermore, the equilibrium constant for the reaction Fe{sup 2+} + H{sup {minus}} = FeHS{sup +} was determined as K = 10{sup 4.34}. The forward rate constant is 10{sup 3.81}(mol/l){sup {minus}1}sec{sup {minus}1} and the backward rate constant is 10{sup {minus}0.53} (mol/l){sup {minus}1} sec{sup {minus}1}.« less

  • This project seeks to advance the fundamental understanding of the physico-chemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid mine drainage. A novel approach to the study of pyrite aqueous electrochemistry is proposed, based on the use of both synthetic and natural (i.e. coal-derived) pyrite specimens, the utilization of pyrite both in the form of micro (i.e. colloidal and subcolloidal) and macro (i.e. rotating ring disk)-electrodes, and the application of in-situ direct electroanalytical and spectroelectrochemical characterization techniques. Central to this research is the recognition that pyrite is a semiconductor material. (Photo) electrochemicalmore » experiments will be conducted to unravel the mechanisms of anodic and cathodic processes such as those associated with pyrite decomposition and the reduction of oxidants such as molecular oxygen and the ferric ion.« less

  • ;
    The effects of the semiconductor properties of pyrite on its electrochemical behavior have been explored with the aid of energy level diagram which illustrate the relationship between the energy levels of the solid land the equilibrium potentials of the redox couples in the aqueous solution. A novel approach to the study of pyrite electrochemistry was initiated. This approach is based on pyrite microelectrodes synthesized via aqueous phase precipitation. Preliminary results show that photocurrents can be generated by illumination of the pyrite particles synthesized in our laboratory. Central to this research is the recognition that pyrite is a semiconductor material. (Photo)more » electrochemical experiments are conducted to unravel the mechanisms of anodic and cathodic processes such as those associated with pyrite decomposition and the reduction of oxidants such as molecular oxygen and the ferric ion.« less

  • ; ;
    The objective of this project is to study the effectiveness of a novel hydrophobic microorganism, Mycobacterium phlei (M. phlei), for the selective flocculation of coal from pyrite and ash forming minerals. During the reporting period, the flocculation efficiencies of Illinois No.6 coal with M. phlei and with polymeric flocculants such as polyethylene oxide and polyacrylamide were investigated. Results indicated that good flocculation efficiencies were obtained with M. phlei as opposed to synthetic flocculants at an acidic pH value. Floc separation studies were conducted using column flotation. It was found that very good recovery of coal with a high rejection ofmore » pyrite and ash could be obtained using M. phlei when compared with synthetic flocculants. DLVO calculations for coal/M. phlei interface showed that minimum interaction energy occurs at acidic pH values thus facilitating the adhesion of M. phlei. A good correlation between the interaction energy and adhesion, contact angle and flocculation results were noticed.« less

  • ;
    This project seeks to advance the fundamental understanding of the physicochemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid mine drainage. Pyrite particles were synthesized by aqueous precipitation and purified by means of solvent extraction to remove elemental sulfur. A purified pyrite sample containing 98.35% FeS{sub 2} was obtained and used in photoelectrochemical experiments. Illumination of pyrite microelectrodes increased both the anodic current and the dissolution rate dramatically, but it had little effect on the cathodic current and the cathodic dissolution. These results indicate that pyrite, as an n-type semiconductor, dissolves anodicallymore » through a hole transfer pathway, while cathodic dissolution involves only electron reaction.« less