Controlling of incipient oxidation of pyrite for improved rejection. Sixth quarterly technical progress report, January 1, 1994--March 31, 1994

Technical Report · Fri Jul 01 04:00:00 EDT 1994

DOI:https://doi.org/10.2172/10162799· OSTI ID:10162799

Yoon, R H; Richardson, P E

The major objectives of this work are (1) to determine the Eh-pH conditions under which pyrite is stable, (2) to determine the mechanism of the initial stages of pyrite oxidation, and (3) to determine if the semiconducting properties of pyrite affect 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 preexisting oxidation products on the surface. Electrochemical reduction and oxidation of these preexisting products essentially mask the oxidation of pyrite itselL 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, voltammetric and photocurrent studies have been carried out as a function of pH and the photoresponse of pyrites from different sources have been determined.

• 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: 10162799
• Report Number(s): DOE/PC/92547--T4; ON: DE94014515; BR: AA1525050
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010300
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400
COAL PREPARATION
ELECTROCHEMISTRY
FLOTATION
INHIBITION
OXIDATION
PH VALUE
PREPARATION
PROGRESS REPORT
PYRITE
VOLTAMETRY