| Records |
Author  |
Evangelou, V.P. |
| Title |
Pyrite microencapsulation technologies: Principles and potential field application |
Type |
Journal Article |
| Year |
2001 |
Publication |
Ecological Engineering |
Abbreviated Journal |
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| Volume |
17 |
Issue |
2-3 |
Pages |
165-178 |
| Keywords |
mine water treatment Acid mine drainage Acidity Alkalinity Amelioration Coating Oxidation Surface reactions |
| Abstract |
In nature, pyrite is initially oxidized by atmospheric O2, releasing acidity and Fe2+. At pH below 3.5, Fe2+ is rapidly oxidized by T. ferrooxidans to Fe3+, which oxidizes pyrite at a much faster rate than O2. Commonly, limestone is used to prevent pyrite oxidation. This approach, however, has a short span of effectiveness because after treatment the surfaces of pyrite particles remain exposed to atmospheric O2 and oxidation continuous abiotically. Currently, a proposed mechanism for explaining non-microbial pyrite oxidation in high pH environments is the involvement of OH- in an inner-sphere electron-OH exchange between pyrite/surface-exposed disulfide and pyrite/surface-Fe(III)(OH)n3-n complex and/or formation of a weak electrostatic pyrite/surface-CO3 complex which enhances the chemical oxidation of Fe2+. The above infer that limestone application to pyritic geologic material treats only the symptoms of pyrite oxidation through acid mine drainage neutralization but accelerates non-microbial pyrite oxidation. Therefore, only a pyrite/surface coating capable of inhibiting O2 diffusion is expected to control long-term oxidation and acid drainage production. The objective of this study was to examine the feasibility in controlling pyrite oxidation by creating, on pyrite surfaces, an impermeable phosphate or silica coating that would prevent either O2 or Fe3+ from further oxidizing pyrite. The mechanism underlying this coating approach involves leaching mine waste with a coating solution composed of H2O2 or hypochlorite, KH2PO4 or H4SiO4, and sodium acetate (NaAC) or limestone. During the leaching process, H2O2 or hypochlorite oxidizes pyrite and produces Fe3+ so that iron phosphate or iron silicate precipitates as a coating on pyrite surfaces. The purpose of NaAC or limestone is to eliminate the inhibitory effect of the protons (produced during pyrite oxidation) on the precipitation of iron phosphate or silicate and to generate iron-oxide pyrite coating, which is also expected to inhibit pyrite oxidation. The results showed that iron phosphate or silicate coating could be established on pyrite by leaching it with a solution composed of: (1) H2O2 0.018-0.16 M; (2) phosphate or silicate 10-3 to 10-2 M; (3) coating-solution pH [approximate]5-6; and (4) NaAC as low as 0.01 M. Leachates from column experiments also showed that silicate coatings produced the least amount of sulfate relative to the control, limestone and phosphate treatments. On the other hand, limestone maintained the leachate near neutral pH but produced more sulfate than the control. |
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0925-8574 |
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July 01; Pyrite microencapsulation technologies: Principles and potential field application; file:///C:/Dokumente%20und%20Einstellungen/Stefan/Eigene%20Dateien/Artikel/10063.pdf; Science Direct |
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| Call Number |
CBU @ c.wolke @ 10063 |
Serial |
37 |
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| Author |
Evangelou, V.P. |
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Book Whole |
| Year |
1995 |
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293 pp |
| Keywords |
solution chemistry surface chemistry acid mine drainage (AMD) molecular oxidation mechanics microbial role, kinetics, control, ameliorates and limitations microencapsulation |
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Pyrite oxidation and its control: solution chemistry, surface chemistry, acid mine drainage (AMD), molecular oxidation mechanisms, microbial role, kinetics, control, ameliorates and limitations, microencapsulation |
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0-8493-4732-7 |
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Pyrite oxidation and its control: solution chemistry, surface chemistry, acid mine drainage (AMD), molecular oxidation mechanisms, microbial role, kinetics, control, ameliorates and limitations, microencapsulation; Boca Raton, Fla. : CRC Press, cop. 1995; Opac |
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CBU @ c.wolke @ 6935 |
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385 |
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| Author |
Evangelou, V.P. |
| Title |
Potential microencapsulation of pyrite by artificial inducement of FePO (sub 4) coatings |
Type |
Book Chapter |
| Year |
1994 |
Publication |
Special Publication – United States. Bureau of Mines, Report: BUMINES-SP-06B-94 |
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96-103 |
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acid mine drainage chemical reactions leaching oxidation pollutants pollution pyrite remediation sulfides tailings theoretical studies waste disposal weathering rinds 22, Environmental geology |
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Proceedings of the International land reclamation and mine drainage conference and Third international conference on The abatement of acidic drainage; Volume 2 of 4; Mine drainage |
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Potential microencapsulation of pyrite by artificial inducement of FePO (sub 4) coatings; GeoRef; English; 2007-045209; International land reclamation and mine drainage conference; International conference on The abatement of acidic drainage, Pittsburgh, PA, United States, April 24-29, 1994 References: 11; illus. |
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| Call Number |
CBU @ c.wolke @ 16711 |
Serial |
386 |
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