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Author  |
Cravotta, C.A., III; Trahan, M.K. |
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Title |
Limestone drains to increase pH and remove dissolved metals from acidic mine drainage |
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Journal Article |
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Year |
1999 |
Publication |
Appl. Geochem. |
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14 |
Issue |
5 |
Pages |
581-606 |
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Keywords |
manganese oxide redox processes sulfate waters iron-oxides adsorption ions oxidation surfaces environments aluminum |
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Abstract |
Despite encrustation by Fe and Al hydroxides, limestone can be effective for remediation of acidic mine drainage (AMD). Samples of water and limestone (CaCO3) were collected periodically for 1 a at 3 identical limestone-filled drains in Pennsylvania to evaluate the attenuation of dissolved metals and the effects of pH and Fe- and Al-hydrolysis products on the rate of CaCO3 dissolution. The influent was acidic and relatively dilute (pH < 4; acidity < 90 mg) but contained 1-4 mg . L-1 of O-2, Fe3+, Al3+ and Mn2+. The total retention time in the oxic limestone drains (OLDs) ranged from 1.0 to 3.1 hr. Effluent remained oxic (O-2 > 1 mg . L-1) but was near neutral (pH = 6.2-7.0); Fe and Al decreased to less than 5% of influent concentrations. As pH increased near the inflow, hydrous Fe and Al oxides precipitated in the OLDs, The hydrous oxides, nominally Fe(OH)(3) and Al(OH)(3), were visible as loosely bound, orange-yellow coatings on limestone near the inflow. As time elapsed, Fe(OH)(3) and Al(OH)(3) particles were transported downflow. The accumulation of hydrous oxides and elevated pH (> 5) in the downflow part of the OLDs promoted sorption and coprecipitation of dissolved Mn, Cu, Co, Ni and Zn as indicated by decreased concentrations of the metals in effluent and their enrichment relative to Fe in hydrous-oxide particles and coatings on limestone. Despite thick (similar to 1 mm) hydrous-oxide coatings on limestone near the inflow, CaCO3 dissolution was more rapid near the inflow than at downflow points within and the OLD where the limestone was not coated. The high rates of CaCO3 dissolution and Fe(OH3) precipitation were associated with the relatively low pH and high Fe3+ concentration near the inflow. The rate of CaCO3 dissolution decreased with increased pH and concentrations of Ca2+ and HCO3- and decreased Pco(2). Because overall efficiency is increased by combining neutralization and hydrolysis reactions, an OLD followed by a settling pond requires less land area than needed for a two-stagetreatment system consisting of an anoxic limestone drain and oxidation-settling pond or wetland. To facilitate removal of hydrous-oxide sludge, a perforated-pipe subdrain can be installed within an OLD. (C) 1999 Elsevier Science Ltd. |
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0883-2927 |
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Jul; Limestone drains to increase pH and remove dissolved metals from acidic mine drainage; Isi:000080043300004; file:///C:/Dokumente%20und%20Einstellungen/Stefan/Eigene%20Dateien/Artikel/10102.pdf; AMD ISI | Wolkersdorfer |
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CBU @ c.wolke @ 17470 |
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22 |
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Author |
Dill, S.; Cowan, J.; Wood, A.; Bowell, R.J. |
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Year |
1998 |
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Pages |
329-342 |
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Keywords |
hydrogeology mining water sulfate oxidation pyrite corrosion economy membrane processes precipitation processes treatment |
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Proceedings International Mine Water Association Symposium |
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2 |
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Nel Petrus Johannes, L. |
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Mine Water and Environmental Impacts |
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062-02294-0-3 |
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Notes |
A Review of Sulfate Removal Options from Mine Waters; 1; AMD ISI | Wolkersdorfer; FG 'de' |
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CBU @ c.wolke @ 9596 |
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402 |
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Author |
Diz, H.R. |
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Title |
Chemical and biological treatment of acid mine drainage for the removal of heavy metals and acidity |
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1997 |
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acid mine drainage; copper; effluents; ferrous iron; heavy metals; iron; manganese; metals; nickel; oxidation; pH; pollution; precipitation; rates; tailings; temperature; waste water; zinc 22, Environmental geology |
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Ph.D. thesis |
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Virginia Polytechnic Institute and State University, |
Place of Publication |
Blacksburg |
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Chemical and biological treatment of acid mine drainage for the removal of heavy metals and acidity; GeoRef; English |
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CBU @ c.wolke @ 6316 |
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400 |
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Author |
Evangelou, V.P. |
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Title |
Pyrite microencapsulation technologies: Principles and potential field application |
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Journal Article |
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Year |
2001 |
Publication |
Ecological Engineering |
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17 |
Issue |
2-3 |
Pages |
165-178 |
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Keywords |
mine water treatment Acid mine drainage Acidity Alkalinity Amelioration Coating Oxidation Surface reactions |
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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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CBU @ c.wolke @ 10063 |
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37 |
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Author |
Evangelou, V.P. |
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1995 |
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293 pp |
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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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