| 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 |
Goulet, R.R. |
| Title |
Changes in dissolved and total Fe and Mn in a young constructed wetland: Implications for retention performance |
Type |
Journal Article |
| Year |
2001 |
Publication |
Ecological Engineering |
Abbreviated Journal |
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| Volume |
17 |
Issue |
4 |
Pages |
373-384 |
| Keywords |
mine water treatment |
| Abstract |
Surface-flow wetlands are generally considered sinks for Fe and Mn but they may also export and affect the partitioning of these metals. This study was undertaken to evaluate the effect of a young constructed wetland on the retention and transformation of both dissolved and particulate Fe and Mn. Duplicate water samples were collected every three days at the inlet and outlet structures of the Monahan Wetland, Kanata, Ontario, from spring of 1997 to 1999. While on a yearly basis the wetland showed significant retention of che dissolved phase, the retention of total Fe and Mn was poor. There were strong seasonal differences in retention and, during the winter, the wetland was a source. The wetland transformed dissolved into particulate Fe and Mn from spring to fall whereas during the winter, dissolved Fe and Mn were released. Changes in pH, alkalinity and temperature could explain 11% and 40% of the outlet variation in the ratio of dissolved to total Fe and Mn respectively. Furthermore, from spring to late summer, planktonic algal biomass was negatively related to the ratio of dissolved to total Fe and Mn implying a role in Fe and Mn transformations in young wetlands where emergent and submerged vegetation have yet to dominate the system. (C) 2001 Elsevier Science B.V. All rights reserved. |
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Changes in dissolved and total Fe and Mn in a young constructed wetland: Implications for retention performance; Wos:000169881900004; Times Cited: 5; ISI Web of Science |
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CBU @ c.wolke @ 17050 |
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124 |
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Schoeman, J.J.; Steyn, A. |
| Title |
Investigation into alternative water treatment technologies for the treatment of underground mine water discharged by Grootvlei Proprietary Mines Ltd into the Blesbokspruit in South Africa |
Type |
Journal Article |
| Year |
2001 |
Publication |
Desalination |
Abbreviated Journal |
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| Volume |
133 |
Issue |
1 |
Pages |
13-30 |
| Keywords |
underground mine water treatment technologies reverse osmosis electrodialysis reversal ion-exchange water quality brine disposal treatment costs |
| Abstract |
Grootvlei Proprietary Mines Ltd is discharging between 80 and 100 Ml/d underground water into the Blesbokspruit. This water is pumped out of the mine to keep the underground water at such a level as to make mining possible. The water is of poor quality because it contains high TDS levels (2700-3800 mg/l) including high concentrations of iron, manganese, sulphate, calcium, magnesium, sodium and chloride. This water will adversely affect the water ecology in the Blesbokspruit, and it will significantly increase the TDS concentration of one of the major water resources if not treated prior to disposal into the stream. Therefore, alternative water desalination technologies were evaluated to estimate performance and the economics of the processes for treatment of the mine water. It was predicted that water of potable quality should be produced from the mine water with spiral reverse osmosis (SRO). It was demonstrated that it should be possible to reduce the TDS of the mine water (2000-2700-3400-4500 mg/l) to potable standards with SRO (85% water recovery). The capital costs (pretreatment and desalination) for a 80 Ml/d plant (worst-case water) were estimated at US$35M. Total operating costs were estimated at 88.1c/kl. Brine disposal costs were estimated at US$18M. Therefore, the total capital costs are estimated at US$53M. It was predicted that it should be possible to produce potable water from the worst-case feed water (80 Ml/d) with the EDR process. It was demonstrated that the TDS in the feed could be reduced from 4178 to 246 mg/l in the EDR product (65% water recovery). The capital costs (pretreatment plus desalination) to desalinate the worst-case feed water to potable quality with EDR is estimated at US$53.3M. The operational costs are estimated at 47.6 c/kl. Brine disposal costs were estimated at US$42M. Therefore, the total capital costs are estimated at US$95.3 M. It was predicted that it should be possible to produce potable water from the mine water with the GYP-CIX ion- exchange process. It was demonstrated that the feed TDS (2000- 4500 mg/l) could be reduced to less than 240 mg/l (54% water recovery for the worst-case water). The capital cost for an 80 Ml/d ion-exchange plant (worst-case water) was estimated at US$26.7M (no pretreatment). Operational costs were estimated at 60.4 c/kl. Brine disposal costs were estimated at US$55.1M. Therefore, the total desalination costs were estimated at US$81.8M. The capital outlay for a SRO plant will be significantly less than that for either an EDR or a GYP-CIX plant. The operating costs, however, of the RO plant are significantly higher than for the other two processes. Potable water sales, however, will bring more in for the RO process than for the other two processes because a higher water recovery can be obtained with RO. The operating costs minus the savings in water sales were estimated at 17.2; 6.7 and US$8.6M/y for the RO, EDR and GYP-CIX processes, respectively (worst case). Therefore, the operational costs of the EDR and GYP-CIX processes are the lowest if the sale of water is taken into consideration. This may favour the EDR and GYP-CIX processes for the desalination of the mine water. |
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0011-9164 |
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Feb. 10; Investigation into alternative water treatment technologies for the treatment of underground mine water discharged by Grootvlei Proprietary Mines Ltd into the Blesbokspruit in South Africa; Isi:000167087500002; file:///C:/Dokumente%20und%20Einstellungen/Stefan/Eigene%20Dateien/Artikel/10184.pdf; AMD ISI | Wolkersdorfer |
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no |
| Call Number |
CBU @ c.wolke @ 17480 |
Serial |
23 |
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Foucher, S.; Battaglia-Brunet, F.; Ignatiadis, I.; Morin, D. |
| Title |
Treatment by sulfate-reducing bacteria of Chessy acid-mine drainage and metals recovery |
Type |
Journal Article |
| Year |
2001 |
Publication |
Chemical Engineering Science |
Abbreviated Journal |
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| Volume |
56 |
Issue |
4 |
Pages |
1639-1645 |
| Keywords |
Acid mine drainage Sulfate-reducing bacteria Sulfide precipitation Hydrogen transfer Fixed bed column reactor |
| 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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no |
| Call Number |
CBU @ c.wolke @ 10064 |
Serial |
54 |
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| Author |
Govind, R. |
| Title |
Treatment of acid mine drainage using membrane bioreactors |
Type |
Journal Article |
| Year |
2001 |
Publication |
Bioremediation of Inorganic Compounds |
Abbreviated Journal |
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| Volume |
6 |
Issue |
9 |
Pages |
1-8 |
| Keywords |
mine water treatment |
| Abstract |
Acid mine drainage is a severe water pollution problem attributed to past mining activities. The exposure of the post-mining mineral residuals to water and air results in a series of chemical and biological oxidation reactions, that produce an effluent which is highly acidic and contains high concentrations of various metal sulfates. Several treatment techniques utilizing sulfate reducing bacteria have been proposed in the past; however few of them have been practically applied to treat acid mine drainage. This research deals with membrane reactor studies to treat the acid mine drainage water from Berkeley Pit in Butte, Montana using hydrogen-consuming sulfate reducing bacteria. Eventually, the membrane reactor system can be applied towards the treatment of acid mine drainage to produce usable water. |
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Treatment of acid mine drainage using membrane bioreactors; Isip:000175098600001; Times Cited: 0; ISI Web of Science |
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no |
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CBU @ c.wolke @ 17051 |
Serial |
162 |
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