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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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Tsukamoto, T.K.; Miller, G.C. |
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Title |
Methanol as a Carbon Source for Microbiological Treatment of Acid Mine Drainage |
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Journal Article |
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Year |
1999 |
Publication |
Water Res. |
Abbreviated Journal |
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33 |
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6 |
Pages |
1365-1370 |
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mine water treatment mining activity sulfate-reducing bacteria microbial activity acid mine drainage methanol passive treatment systems sulfate-reducing bacterium sp-nov |
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Sulfate reducing passive bioreactors are increasingly being used to remove metals and raise the pH of acidic waste streams from abandoned mines. These systems commonly use a variety of organic substrates (i.e. manure, wood chips) for sulfate reduction. The effectiveness of these systems decreases as easily accessible reducing equivalents are consumed in the substrate through microbial activity. Using column studies at room temperature (23-26 degrees C), we investigated the addition of lactate and methanol to a depleted manure substrate as a method to reactivate a bioreactor that had lost >95% of sulfate reduction activity. A preliminary experiment compared sulfate removal in gravity fed, flow through bioreactors in which similar masses of each substrate were added to the influent solution. Addition of 148 mg/l lactate resulted in a 69% reduction in sulfate concentration from 300 to 92 mg/l, while addition of 144 mg/l methanol resulted in an 88% reduction in sulfate concentration from 300 to 36 mg/l. Because methanol was found to be an effective sulfate reducing substrate, it was chosen for further experiments due to its inherent physical properties (cost, low freezing point and low viscosity liquid) that make it a superior substrate for remote, high elevation sites where freezing temperatures would hamper the use of aqueous solutions. In these column studies, water containing sulfate and ferrous iron was gravity-fed through the bioreactor columns, along with predetermined methanol concentrations containing reducing equivalents to remove 54% of the sulfate. Following an acclimation period for the columns, sulfate concentrations were reduced from of 900 mg/l in the influent to 454 mg/l in the effluent, that reflects a 93% efficiency of electrons from the donor to the terminal electron acceptor. Iron concentrations were reduced from 100 to 2 mg/l and the pH increased nearly 2 units. (C) 1999 Elsevier Science Ltd. |
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0043-1354 |
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Apr; Methanol as a Carbon Source for Microbiological Treatment of Acid Mine Drainage; Isi:000079485400004; file:///C:/Dokumente%20und%20Einstellungen/Stefan/Eigene%20Dateien/Artikel/10197.pdf; AMD ISI | Wolkersdorfer |
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CBU @ c.wolke @ 10197 |
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50 |
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Author |
Holtzhausen, L. |
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Title |
Minewater treatment technology revved up |
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Journal Article |
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2005 |
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Water Sewage and Effluent |
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25 |
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2 |
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24-26 |
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Geobase: Related Topics geobase: related topics (901) water treatment |
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0257-8700 |
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Trade- Note; Minewater treatment technology revved up; 2710582; South-Africa; Geobase |
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CBU @ c.wolke @ 10344 |
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348 |
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Tarutis Jr, W.J.; Stark, L.R.; Williams, F.M. |
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Title |
Sizing and performance estimation of coal mine drainage wetlands |
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Journal Article |
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Year |
1999 |
Publication |
Ecological Engineering |
Abbreviated Journal |
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12 |
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3-4 |
Pages |
353-372 |
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mine water treatment coal mine drainage constructed wetlands efficiency first-order removal loading rate removal kinetics sizing zero-order removal constructed wetlands water-quality iron kinetics removal model phosphorus retention mechanism design Wetlands and estuaries geographical abstracts: physical geography hydrology (71 6 8) acid mine drainage effluent performance assessment remediation wetland management |
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The effectiveness of wetland treatment of acid mine drainage (AMD) was assessed using three measures of performance: treatment efficiency, area-adjusted removal, and first-order removal. Mathematical relationships between these measures were derived from simple kinetic equations. Area-adjusted removal is independent of pollutant concentration (zero-order reaction kinetics), while first-order removal is dependent on concentration. Treatment efficiency is linearly related to area-adjusted removal and exponentially related to first-order removal at constant hydraulic loading rates (flow/area). Examination of previously published data from 35 natural AMD wetlands revealed that statistically significant correlations exist between several of the performance measures for both iron and manganese removal, but these correlations are potentially spurious because these measures are derived from, and are mathematical rearrangements of, the same operating data. The use of treatment efficiency as a measure of performance between wetlands is not recommended because it is a relative measure that does not account for influent concentration differences. Area-adjusted removal accounts for mass loading effects, but it fails to separate the flow and concentration components, which is necessary if removal is first-order. Available empirical evidence suggests that AMD pollutant removal is better described by first-order kinetics. If removal is first-order, the use of area-adjusted rates for determining the wetland area required for treating relatively low pollutant concentrations will result in undersized wetlands. The effects of concentration and flow rate on wetland area predictions for constant influent loading rates also depend on the kinetics of pollutant removal. If removal is zero-order, the wetland area required to treat a discharge to meet some target effluent concentration is a decreasing linear function of influent concentration (and an inverse function of flow rate). However, if removal is first-order, the required wetland area is a non-linear function of the relative influent concentration. Further research is needed for developing accurate first-order rate constants as a function of influent water chemistry and ecosystem characteristics in order to successfully apply the first-order removal model to the design of more effective AMD wetland treatment systems. |
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W.J. Tarutis Jr., Department of Natural Science, Lackawanna Junior College, 501 Vine Street, Scranton, PA 18509, United States |
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Feb.; Sizing and performance estimation of coal mine drainage wetlands; 0427766; Netherlands 46; file:///C:/Dokumente%20und%20Einstellungen/Stefan/Eigene%20Dateien/Artikel/10596.pdf; Geobase |
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CBU @ c.wolke @ 10596 |
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25 |
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Banks, D.; Younger, P.L.; Arnesen, R.-T.; Iversen, E.R.; Banks, S.B. |
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Mine-water chemistry: The good, the bad and the ugly |
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Journal Article |
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1997 |
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Environ. Geol. |
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32 |
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3 |
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157-174 |
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mine water treatment mine-water chemistry acid mine drainage mine-water pollution mine-water treatment county-durham drainage movements Pollution and waste management non radioactive Groundwater problems and environmental effects mine drainage contamination hydrogeochemistry mine water drainage acid mine drainage |
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Contaminative mine drainage waters have become one of the major hydrogeological and geochemical problems arising from mankind's intrusion into the geosphere. Mine drainage waters in Scandinavia and the United Kingdom are of three main types: (1) saline formation waters; (2) acidic, heavy-metal-containing, sulphate waters derived from pyrite oxidation, and (3) alkaline, hydrogen-sulphide-containing, heavy-metal-poor waters resulting from buffering reactions and/or sulphate reduction. Mine waters are not merely to be perceived as problems, they can be regarded as industrial or drinking water sources and have been used for sewage treatment, tanning and industrial metals extraction. Mine-water problems may be addressed by isolating the contaminant source, by suppressing the reactions releasing contaminants, or by active or passive water treatment. Innovative treatment techniques such as galvanic suppression, application of bactericides, neutralising or reducing agents (pulverised fly ash-based grouts, cattle manure, whey, brewers' yeast) require further research. |
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D. Banks, Norges Geologiske Undersokelse, Postboks 3006 – Lade, N-7002 Trondheim, Norway |
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0943-0105 |
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Oct.; Mine-water chemistry: The good, the bad and the ugly; 0337169; Germany 78; file:///C:/Dokumente%20und%20Einstellungen/Stefan/Eigene%20Dateien/Artikel/10620.pdf; Geobase |
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CBU @ c.wolke @ 10620 |
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18 |
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