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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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Volume |
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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Kalin, M.; Cairns, J.; McCready, R. |
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Title |
Ecological engineering methods for acid mine drainage treatment of coal wastes |
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Journal Article |
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Year |
1991 |
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Resources, conservation and recycling |
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5 |
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2-3 |
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265-275 |
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The treatment of acid mine drainage (AMD) through the utilization of alkali generating microbes has potential as an alternate approach to conventional lime treatment. Organic matter, a source of fixed carbon for the alkali generating microbial ecosystem, has been tested in 6 different types of AMD. The AMD characteristics range in acidities from 2 mg/l to 900 mg/l (CaCO3 equivalent), while sulphate concentrations range from 75 to 7300 mg/l. Alkali generating populations identified include iron reducers, sulphate reducers and ammonifiers. In coal AMD amended with organic matter, the microbial alkali generation is dominated by ammonifiers. Concentrations of Al, Fe and Zn in the AMD water decreased with concurrent increases in pH (3.2 to 6.5) in localized areas in the test cells. |
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Ecological engineering methods for acid mine drainage treatment of coal wastes; Science Direct |
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CBU @ c.wolke @ 17276 |
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39 |
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Burgess, J.E.; Stuetz, R.M. |
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Title |
Activated Sludge for the Treatment of Sulphur-rich Wastewaters |
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Journal Article |
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2002 |
Publication |
Miner. Eng. |
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15 |
Issue |
11 |
Pages |
839-846 |
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Keywords |
acid rock drainage biooxidation biotechnology environmental waste processing acid-mine drainage sulfate-reducing bacteria biological treatment waste-water metals acclimation remediation oxidation reduction removal |
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The aim of this investigation was to assess the potential of activated sludge for the remediation of sulphur-rich wastewaters. A pilot-scale activated sludge plant was acclimatised to a low load of sulphide and operated as a flow-through unit. Additional sludge samples from different full-scale plants were compared with the acclimatised and unacclimatised sludges using batch absorption tests. The effects of sludge source and acclimatisation on the ability of the sludge to biodegrade high loads of sulphide were evaluated. Acclimatisation to low-sulphide concentrations enabled the sludge to degrade subsequent high loads which were toxic to unacclimatised sludge. Acclimatisation was seen to be an effect of selection pressure on the biomass, suggesting that the treatment capability of activated sludge will develop after acclimation, indicating potential for treatment of acid mine drainage (AMD) by a standard wastewater treatment process. Existing options for biological treatment of AMD are described and the potential of activated sludge treatment for AMD discussed in comparison with existing technologies. (C) 2002 Elsevier Science Ltd. |
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0892-6875 |
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Nov.; Activated Sludge for the Treatment of Sulphur-rich Wastewaters; Isi:000179970500009; file:///C:/Dokumente%20und%20Einstellungen/Stefan/Eigene%20Dateien/Artikel/10093.pdf; AMD ISI | Wolkersdorfer |
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CBU @ c.wolke @ 10093 |
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40 |
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Sheoran, A.S.; Sheoran, V. |
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Title |
Heavy metal removal mechanism of acid mine drainage in wetlands: A critical review |
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Journal Article |
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Year |
2006 |
Publication |
Minerals Engineering |
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19 |
Issue |
2 |
Pages |
105-116 |
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Keywords |
Acid mine drainage Metal removal mechanism Wetlands |
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Acid mine drainage (AMD) is one of the most significant environmental challenges facing the mining industry worldwide. Water infiltrating through the metal sulphide minerals, effluents of mineral processing plants and seepage from tailing dams becomes acidic and this acidic nature of the solution allows the metals to be transported in their most soluble form. The conventional treatment technologies used in the treatment of acid mine drainage are expensive both in terms of operating and capital costs. One of the methods of achieving compliance using passive treatment systems at low cost, producing treated water pollution free, and fostering a community responsibility for acid mine water treatment involves the use of wetland treatment system. These wetlands absorb and bind heavy metals and make them slowly concentrated in the sedimentary deposits to become part of the geological cycle. In this paper a critical review of the heavy metal removal mechanism involving various physical, chemical and biological processes, which govern wetland performance, have been made. This information is important for the siting and use of wetlands for remediation of heavy metals. |
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Heavy metal removal mechanism of acid mine drainage in wetlands: A critical review; Science Direct |
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Call Number |
CBU @ c.wolke @ 17252 |
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41 |
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Potgieter-Vermaak, S.S.; Potgieter, J.H.; Monama, P.; Van Grieken, R. |
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Title |
Comparison of limestone, dolomite and fly ash as pre-treatment agents for acid mine drainage |
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Journal Article |
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Year |
2006 |
Publication |
Minerals Engineering |
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19 |
Issue |
5 |
Pages |
454-462 |
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Acid rock drainage Mining Tailings Environmental |
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The physical, chemical and biological nature of Vaal Dam water, the main source of water in Gauteng, South Africa, is often affected by underground water pollution (acid mine water) and industrial effluents. The ecological significance and detrimental effects necessitate investigations into treating the water prior to discharge into public streams. Although several acid mine water treatment techniques and methods exist, they all have certain disadvantages. Lime treatment is the most common approach. In this investigation, limestone, dolomite and fly ash were selected as pre-treatment agents based on their low cost. Simulated acid mine water containing these agents was tested using a Jar Test apparatus. Samples were analyzed before and after treatment for pH, ferrous, ferric, calcium, magnesium and sulphate ions. The study demonstrated that the quality of the water improved with an increase in the amount and surface area of the raw material dosed and an increase in contact time. It was also influenced by the chemical composition of the acid mine water and aeration. Chemical cost savings of 38% are achieved when lime is replaced with limestone, and cost savings of 23% and 48% can be accomplished when limestone is substituted with dolomite and fly ash respectively. This could result in significant savings to the gold and coal mining industries, and could lead to a mutual benefit/gain between industrialists/polluters and the public. |
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0892-6875 |
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Apr.; Comparison of limestone, dolomite and fly ash as pre-treatment agents for acid mine drainage; Science Direct |
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CBU @ c.wolke @ 17461 |
Serial |
42 |
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