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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 |
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2-3 |
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165-178 |
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Keywords |
mine water treatment Acid mine drainage Acidity Alkalinity Amelioration Coating Oxidation Surface reactions |
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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 |
Foucher, S.; Battaglia-Brunet, F.; Ignatiadis, I.; Morin, D. |
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Title |
Treatment by sulfate-reducing bacteria of Chessy acid-mine drainage and metals recovery |
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Journal Article |
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Year |
2001 |
Publication |
Chemical Engineering Science |
Abbreviated Journal |
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56 |
Issue |
4 |
Pages |
1639-1645 |
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Acid mine drainage Sulfate-reducing bacteria Sulfide precipitation Hydrogen transfer Fixed bed column reactor |
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Abstract |
Acid-mine drainage can contain high concentrations of heavy metals and release of these contaminants into the environment is generally avoided by lime neutralization. However, this classical treatment is expensive and generates large amounts of residual sludge. The selective precipitation of metals using H2S produced biologically by sulfate-reducing bacteria has been proposed as an alternative process. Here, we report on experiments using real effluent from the disused Chessy-les-Mines mine-site at the laboratory pilot scale. A fixed-bed bioreactor, fed with an H2/CO2 mixture, was used in conjunction with a gas stripping column. The maximum rate of hydrogen transfer in the bioreactor was determined before inoculation. kLa was deduced from measurements of O2 using Higbie and Danckwert's models which predict a dependence on diffusivity. The dynamic method of physical absorption and desorption was used. The maximum rate of H2 transfer suggests that this step should not be a limiting factor. However, an increase in H2 flow rate was observed to induce an increase in sulfate reduction rate. For the precipitation step, the gas mixture from the bioreactor was bubbled into a stirred reactor fed with the real effluent. Cu and Zn could be selectively recovered at pH=2.8 and pH=3.5, respectively. Other impurities such as Ni and Fe could also be removed at pH=6 by sulfide precipitation. Part of the outlet stream from the bioreactor was used to regulate and maintain the pH during sulfide precipitation by feeding the outlet stream back into the bioreactor. The replacement of synthetic medium with real effluent had a positive effect on sulfate reduction rate which increased by 30-40%. This improvement in bacterial efficiency may be related to the large range of oligo-elements provided by the mine-water. The maximum sulfate reduction rate observed with the real effluent was 200 mgl-1 h-1, corresponding to a residence time of 0.9 day. A preliminary cost estimation based on a treatment rate of 5 m3 h-1 of a mine effluent containing 5 gl-1 SO42- is presented. |
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0009-2509 |
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Feb.; Treatment by sulfate-reducing bacteria of Chessy acid-mine drainage and metals recovery; file:///C:/Dokumente%20und%20Einstellungen/Stefan/Eigene%20Dateien/Artikel/10064.pdf; Science Direct |
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CBU @ c.wolke @ 10064 |
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54 |
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Davies, G.J.; Holmes, M.; Wireman, M.; King, K.; Gertson, J.N.; Stefanic, J.M. |
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Water tracing at scales of hours to decades as an aid to estimating hydraulic characteristics of the Leadville Mine drainage tunnel |
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Journal Article |
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2001 |
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acid mine drainage Arkansas River Colorado drainage dye tracers field studies fluorescence ground water Lake County Colorado Leadville Mine Leadville mining district pH quantitative analysis recharge surveys tunnels United States water treatment 30 Engineering geology 21 Hydrogeology |
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The Leadville Mine Drainage Tunnel (LMDT) is a 3.3 kilometer structure that was constructed in the complicated geology of the Leadville mine district in the 1940's. Discharge from the LMDT is impacted by heavy metals and is treated at a plant built in 1992 operated by the United States Bureau of Reclamation. On the surface waste rock and other remnants of the mining operations litter the landscape and this material is exposed to precipitation. As a result of contact with this material, surface water often has pH of less than 3 and its containment and disposal is necessary before it impacts surface drainage and the nearby Arkansas River. Using a borehole drilled into the mine workings the U.S. EPA has devised a plan in which the impacted water is contained on the surface which then can be discharged into the mine workings to discharge from the LMDT and be treated. The percentage of water discharging from the mining district along the drainage tunnel is unknown, and since there is no access, information about the condition of the tunnel with regards to blockages is also relatively obscure. Application of quantitative water tracing using fluorescent dyes was used to model the flow parameters at the scale of hours in the tunnel and evaluate the likelihood of blockages. Because the tunnel has intersected several lithologies and faults, other locations such as discharging shafts, adits and surface streams that could be hydraulically connected to the LMDT were also monitored. An initial tracer experiment was done using an instantaneous injection, which was followed by additional injections of water. Another tracer injection was done when there was a continuous flow of impacted water into the workings. Analysis of the tracer concentration responses at water-filled shafts and at the portal were used to model the flow along the tunnel and estimate several hydraulic parameters. Waters in these settings are mixtures of components with different residence times, so, qualitative tritium data were used to evaluate residence times of decades. The combined injected tracer and tritium data as well as other geochemical data were used to infer the nature of flow and recharge into the tunnel. |
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Abstracts with Programs - Geological Society of America |
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Geological Society of America, 2001 annual meeting |
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2004-013418; Geological Society of America, 2001 annual meeting, Boston, MA, United States, Nov. 1-10, 2001; GeoRef; English |
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Call Number |
CBU @ c.wolke @ 16511 |
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408 |
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Banks, S.B.; Banks, D. |
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Title |
Abandoned mines drainage; impact assessment and mitigation of discharges from coal mines in the UK |
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Book Chapter |
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Year |
2001 |
Publication |
Geoenvironmental engineering Engineering Geology |
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31-37 |
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abandoned mines coal mines cost discharge drainage England environmental effects Europe feasibility studies Great Britain mine drainage mines mitigation pollution remediation Scotland United Kingdom Western Europe 22, Environmental geology |
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Abstract |
The UK has a legacy of pollution caused by discharges from abandoned coal mines, with the potential for further pollution by new discharges as groundwaters continue to rebound to their natural levels. In 1995, the Coal Authority initiated a scoping study of 30 gravity discharges from abandoned coal mines in England and Scotland. Mining information, geological information and water quality data were collated and interpreted in order to allow a preliminary assessment of the source and nature of each of the discharges. An assessment of the potential for remediation was made on the basis of the feasibility and relative costs of alternative remediation measures. Environmental impacts of the discharges and of the proposed remediation schemes were also assessed. The results, together with previous Coal Authority studies of discharges in Wales, were used by the Coal Authority, in collaboration with the former National Rivers Authority and the former Forth and Clyde River Purification Boards, to rank discharge sites in order of priority for remediation. |
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60 |
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Yong, R.N.; Thomas, H.R. |
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Abandoned mines drainage; impact assessment and mitigation of discharges from coal mines in the UK; GeoRef; English; 2001-052748; British Geotechnical Society, second conference on Geoenvironmental engineering, London, United Kingdom, Sept. 1999 References: 12; illus. incl. 2 tables |
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CBU @ c.wolke @ 16515 |
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31 |
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Demchak, J.; Morrow, T.; Skousen, J.; Donovan, J.J.; Rose, A.W. |
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Treatment of acid mine drainage by four vertical flow wetlands in Pennsylvania Evolution and remediation of acid-sulfate groundwater systems at reclaimed mine-sites |
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Journal Article |
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2001 |
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Geochemistry – Exploration, Environment, Analysis |
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1 |
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1 |
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71-80 |
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acid mine drainage alkalinity anaerobic environment Appalachian Plateau Appalachians carbonate rocks Clearfield County Pennsylvania constructed wetlands Eh equilibrium Filson Wetlands ground water Howe Bridge Wetlands hydrology Jefferson County Pennsylvania limestone McKinley Wetlands Mill Creek watershed Moose Creek movement North America passive methods Pennsylvania pH pollution reclamation sedimentary rocks Sommerville Wetlands systems United States water treatment watersheds wetlands 22 Environmental geology 02B Hydrochemistry |
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Acid mine drainage (AMD) is a serious problem in many watersheds where coal is mined. Passive treatments, such as wetlands and anoxic limestone drains (ALDs), have been developed, but these technologies show varying treatment efficiencies. A new passive treatment technique is a vertical flow wetland or successive alkalinity producing system (SAPS). Four SAPS in Pennsylvania were studied to determine changes in water chemistry from inflow to outflow. The Howe Bridge SAPS removed about 130 mg l (super -1) (40%) of the inflow acidity concentration and about 100 mg l (super -1) (60%) iron (Fe). The Filson 1 SAPS removed 68 mg l (super -1) (26%) acidity, 20 mg l (super -1) (83%) Fe and 6 mg l (super -1) (35%) aluminium (Al). The Sommerville SAPS removed 112 mg l (super -1) (31%) acidity, exported Fe, and removed 13 mg l (super -1) (30%) Al. The McKinley SAPS removed 54 mg l (super -1) (91%) acidity and 5 mg l (super -1) (90%) Fe. Acid removal rates at our four sites were 17 (HB), 52 (Filson1), 18 (Sommerville) and 11 (McKinley) g of acid per m (super 2) of surface wetland area per day (g/m (super 2) d (super -1) ). Calcium (Ca) concentrations in the SAPS effluents were increased between 8 and 57 mg l (super -1) at these sites. Equilibrators, which were inserted into compost layers to evaluate redox conditions at our sites, showed that reducing conditions were generally found at 60 cm compost depths and oxidized conditions were found at 30 cm compost depths. Deeply oxidized zones substantiated observations that channel flow was occurring through some parts of the compost. The Howe Bridge site has not declined in treatment efficiency over a six year treatment life. The SAPS construction costs were equal to about seven years of NaOH chemical treatment costs and 30 years of lime treatment costs. So, if the SAPS treatment longevity is seven years or greater and comparable effluent water quality was achieved, the SAPS construction was cost effective compared to NaOH chemical treatment. Construction recommendations for SAPS include a minimum of 50 cm of compost thickness, periodic replacement or addition of fresh compost material, and increasing the number of drainage pipes underlying the limestone. |
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1467-7873 |
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Treatment of acid mine drainage by four vertical flow wetlands in Pennsylvania Evolution and remediation of acid-sulfate groundwater systems at reclaimed mine-sites; 2002-008380; References: 15; illus. incl. 5 tables United Kingdom (GBR); GeoRef; English |
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CBU @ c.wolke @ 16518 |
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58 |
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