| 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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CBU @ c.wolke @ 10063 |
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37 |
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| Author |
Ziemkiewicz, P.F.; Skousen, J.G.; Simmons, J. |
| Title |
Long-term Performance of Passive Acid Mine Drainage Treatment Systems |
Type |
Journal Article |
| Year |
2003 |
Publication |
Mine Water Env. |
Abbreviated Journal |
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| Volume |
22 |
Issue |
3 |
Pages |
118-129 |
| Keywords |
acidity acid load aerobic wetlands anaerobic wetlands anoxic limestone drains limestone leach beds open limestone channels slag leach beds successive alkalinity producing systems vertical flow wetlands |
| Abstract |
State and federal reclamation programs, mining operators, and citizen-based watershed organizations have constructed hundreds of passive systems in the eastern U.S. over the past 20 years to provide reliable, low cost, low maintenance mine water treatment in remote locations. While performance has been reported for individual systems, there has not been a comprehensive evaluation of the performance of each treatment type for a wide variety of conditions. We evaluated 83 systems: five types in eight states. Each system was monitored for influent and effluent flow, pH, net acidity, and metal concentrations. Performance was normalized among types by calculating acid load reductions and removals, and by converting construction cost, projected service life, and metric tonnes of acid load treated into cost per tonne of acid treated. Of the 83 systems, 82 reduced acid load. Average acid load reductions were 9.9 t/yr for open limestone channels (OLC), 10.1 t/yr for vertical flow wetlands (VFW), 11.9 t/yr for anaerobic wetlands (AnW), 16.6 t/yr for limestone leach beds (LSB), and 22.2 t/yr for anoxic limestone drains (ALD). Average costs for acid removal varied from $83/t/yr for ALDs to $527 for AnWs. Average acid removals were 25 g/m2/day for AnWs, 62 g/m2/day for VFWs, 22 g/day/t for OLCs, 28 g/day/t for LSBs, and 56 g/day/t for ALDs. It appears that the majority of passive systems are effective but there was wide variation within each system type, so improved reliability and efficiency are needed. This report is an initial step in determining passive treatment system performance; additional work is needed to refine system designs and monitoring. |
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1025-9112 |
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Long-term Performance of Passive Acid Mine Drainage Treatment Systems; 1; FG 1 Abb., 7 Tab.; AMD ISI | Wolkersdorfer |
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CBU @ c.wolke @ 17454 |
Serial |
187 |
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| Author |
Watzlaf, G.R.; Schroeder, K.T.; Kairies, C.L. |
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Type |
Book Whole |
| Year |
2000 |
Publication |
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Issue |
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Pages |
262-274 |
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passive treatment anoxic limestone drains wetlands sulfate reduction successive alkalinity-producing systems acid mine drainage ALD SAPS RAPS |
| Abstract |
Ten passive treatment systems, located in Pennsylvania and Maryland, have been intensively monitored for up to ten years. Influent and effluent water quality data from ten anoxic limestone drains (ALDs) and six reducing and alkalinity-producing systems (RAPS) have been analyzed to determine long-term performance for each of these specific unit operations. ALDs and RAPS are used principally to generate alkalinity, ALDs are buried beds of limestone that add alkalinity through dissolution of calcite. RAPS add alkalinity through both limestone dissolution and bacterial sulfate reduction. ALDs that received mine water containing less than 1 mg/L of both ferric iron and aluminum have continued to produce consistent concentrations of alkalinity since their construction. However, an ALD that received 20 mg/L of aluminum experienced a rapid reduction in permeability and failed within five months. Maximum levels of alkalinity (between 150 and 300 m&) appear to be reached after I5 hours of retention. All but one RAPS in this study have been constructed and put into operation only within the past 2.5 to 5 years. One system has been in operation and monitored for more than nine years. AIkalinity due to sulfate reduction was highest during the first two summers of operation. Alkalinity due to a limestone dissolution has been consistent throughout the life of the system. For the six RAPS in this study, sulfate reduction contributed an average of 28% of the total alkalinity. Rate of total alkalinity generation range from 15.6 gd''rn-'to 62.4 gd-'mL2 and were dependent on influent water quality and contact time. |
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Tampa |
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Proceedings, 17th Annual National Meeting – American Society for Surface Mining and Reclamation |
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Long-Term Perpormance of Alkalinity-Producing Passive Systems for the Treatment of Mine Drainage; 2; VORHANDEN | AMD ISI | Wolkersdorfer; als Datei vorhanden 4 Abb., 5 Tab. |
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no |
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CBU @ c.wolke @ 17440 |
Serial |
216 |
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| Author |
Benner, S.G.; Blowes, D.W.; Ptacek, C.J. |
| Title |
A full-scale porous reactive wall for prevention of acid mine drainage |
Type |
Journal Article |
| Year |
1997 |
Publication |
Ground Water Monitoring and Remediation |
Abbreviated Journal |
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17 |
Issue |
4 |
Pages |
99-107 |
| Keywords |
acid mine drainage alkalinity bacteria Canada case studies concentration dissolved materials drainage Eastern Canada ground water mines observation wells Ontario permeability pH pollution porous materials recharge reduction remediation site exploration Sudbury District Ontario sulfate ion surface water waste disposal water pollution Groundwater quality Groundwater problems and environmental effects Pollution and waste management non radioactive geographical abstracts: physical geography hydrology (71 6 11) geomechanics abstracts: excavations (77 10 10) geological abstracts: environmental geology (72 14 2) groundwater protection permeable barrier acid mine drainage aquifer groundwater acid min drainage contamination permeable barrier groundwater protection permeable barrier acid mine drainage aquifer Canada, Ontario, Sudbury, Nickel Rim |
| Abstract |
The generation and release of acidic drainage containing high concentrations of dissolved metals from decommissioned mine wastes is an environmental problem of international scale. A potential solution to many acid drainage problem is the installation of permeable reactive walls into aquifers affected by drainage water derived from mine waste materials. A permeable reactive wall installed into an aquifer impacted by low-quality mine drainage waters was installed in August 1995 at the Nickel Rim mine site near Sudbury, Ontario. The reactive mixture, containing organic matter, was designed to promote bacterially mediated sulfate reduction and subsequent metal sulfide precipitation. The reactive wall is installed to an average depth of 12 feet (3.6 m) and is 49 feet (15 m) long perpendicular to ground water flow. The wall thickness (flow path length) is 13 feet (4 m). Initial results, collected nine months after installation, indicate that sulfate reduction and metal sulfide precipitation is occurring. Comparing water entering the wall to treated water existing the wall, sulfate concentrations decrease from 2400 to 4600 mg/L to 200 to 3600 mg/L; Fe concentration decrease from 250 to 1300 mg/L to 1.0 to 40 mg/L, pH increases from 5.8 to 7.0; and alkalinity (as CaCO<inf>3</inf>) increases from 0 to 50 mg/L to 600 to 2000 mg/L. The reactive wall has effectively removed the capacity of the ground water to generate acidity on discharge to the surface. Calculations based on comparison to previously run laboratory column experiments indicate that the reactive wall has potential to remain effective for at least 15 years. |
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Dr. S.G. Benner, Earth Sciences Department, University of Waterloo, Waterloo, Ont. N2L 3G1, Canada |
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1069-3629 |
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Review; A full-scale porous reactive wall for prevention of acid mine drainage; 0337197; United-States 46; file:///C:/Dokumente%20und%20Einstellungen/Stefan/Eigene%20Dateien/Artikel/10621.pdf; Geobase |
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CBU @ c.wolke @ 17555 |
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67 |
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