Studies of incipient oxidation of pyrite for improved rejection. Seventh quarterly technical progress report, April 1, 1994--June 30, 1994

Technical Report · Sat Oct 01 04:00:00 EDT 1994

OSTI ID:10188918

Yoon, R H; Richardson, P E

The major objectives of this work are (i) to determine the Eh-pH conditions under which pyrite is stable, (ii) to determine the mechanism of the initial stages of pyrite oxidation, and (iii) to determine if the semiconducting properties of pyrite effects its oxidation behavior. It is known that moderate oxidation of pyrite produces a hydrophobic surface product. This hydrophobic product makes it extremely difficult to depress pyrite in coal flotation circuits. The eventual objective of this work is to prevent pyrite oxidation in order to better depress pyrite in coal flotation circuits. In this work clean, unoxidized pyrite surfaces are being produced by fracturing pyrite electrodes in an electrochemical cell. It has been shown that by holding the potential at different values during fracture and measuring the current passed at fracture, pyrite oxidation or reduction can be precisely controlled, or prevented. It has also been found that fresh pyrite surfaces created by fracture in an electrochemical cell begin to oxidize at potentials that are about 200 mV more negative than the potentials reported in the literature for pyrite oxidation. This is attributed to the fact that most work on pyrite has employed polished electrodes that have pre-existing oxidation products on the surface. Electrochemical reduction and oxidation of these pre-existing products essentially mask the oxidation of pyrite itself. In addition, photocurrent measurements show that freshly fractured pyrite surfaces are charged negatively. This negative charge is believed to result from an intrinsic, acceptor-like surface state. This report period, electrochemical impedance spectroscopy (EIS) has been conducted on pyrite from different sources. In addition, EIS studies have been conducted on an electrode that was first fractured in situ and then polished.

• Research Organization: Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Mining and Minerals Engineering
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG22-92PC92547
• OSTI ID: 10188918
• Report Number(s): DOE/PC/92547--T5; ON: DE95001173; BR: AA1525050
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010300
COAL
DESULFURIZATION
ELECTROCHEMICAL CELLS
ELECTROCHEMISTRY
ELECTRODES
EXPERIMENTAL DATA
FLOTATION
INHIBITION
OXIDATION
PH VALUE
PREPARATION
PROGRESS REPORT
PYRITE
SPECTROSCOPY
SURFACES