When sulfide minerals are exposed to the oxidizing conditions of the earth's surface, their metal ions are released into solution and the S²⁻ is oxidized to either elemental sulfur or sulfate. The experiments described here used a mixed flow reactor system to determine the oxidation rates of galena and sphalerite under conditions similar to that expected in a weathering ore deposit . The specific surface area of the run solids was determined by N₂ BET procedure and the surface textures observed by SEM. The amount of Fe³⁺ converted to Fe²⁺ by the oxidation reaction was determined using an Eh electrode. Solid reaction products include, orthorhombic S(s) and anglesite (PbSO₄) from the galena oxidation and minor orthorhombic S(s) from the sphalerite oxidation. The rate equations describing the 25°C data are:
dn<sub>Fe³⁺</sub>/dt = -5.5 ± 1.1 × 10⁻³ (A)(a<sub>Fe³⁺</sub)<sup>1.06 ± 0.16</sup> for galena, and
dn<sub>Fe³⁺</sub>/dt = -1.8 ± 0.3 × 10⁻⁶ (A)(a<sub>Fe³⁺</sub>)<sup>0.47 ± 0.08</sup> for sphalerite.
Where dn<sub>Fe³⁺</sub>/dt is the rate of reduction of Fe³⁺ (moles sec⁻¹), and A is the surface area of the solid (m²). The calculated E<sub>a</sub> for galena oxidation is 48 kJ mol⁻¹ (25 - 40°C) and is 84 kJ mol⁻¹ (25 -60°C) for sphalerite oxidation. Although galena and sphalerite are both simple, cubic, monosulfides their reaction rate with ferric iron differs by about 2.5 orders of magnitude for m<sub>Fe³⁺</sub> = 10⁻³. / M.S.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/106080 |
| Date | January 1986 |
| Creators | Chermak, John Alan |
| Contributors | Geology |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | vi, 37 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 15170418 |
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