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Accelerated precipitation of ochre for mine water remediation
A42
Goldschmidt Conference Abstracts 2006
Accelerated precipitation of ochre for mine water remediation
A multi-proxy approach of the Bajocian sedimentary crisis in western Tethys
J.M. BEARCOCK, W.T. PERKINS
V. BEAUMONT1, A. BARTOLINI2, R. MAS1, S. GARDIN2, J. GAILLARDET3, B. CHETELAT3, L. O’DOGHERTY4, J. SANDOVAL5, F. CECCA2
Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, UK ([email protected]; [email protected]) 1
Metal-rich mine drainage is a worldwide environmental problem, its treatment can be passive or active. This paper discusses a series of laboratory scale experiments which investigated the accelerated precipitation of ochre for the treatment of metal-rich mine waters. A variety of naturally occurring Fe oxy-hydroxides, a problematic waste material, have been collected from mine discharges. These were added to a range of mine waters to investigate accelerated precipitation of ochre as a remediation method. This removes Fe which co-precipitates elements from the drainage solution. The most effective ‘‘ochre’’, green rust (GR), is discussed here. Results: Parys Mountain, N Wales, is an example of a metalrich AMD discharge with a pH of 2.7. The raw water contains 75 mg L 1 Fe and 24 mg L 1 Zn. GR particles, at 5 g L 1, were added, accelerating precipitation. Dissolved Fe and Zn were rapidly reduced to 12 and 5 mg L 1, respectively after 10 min, and to 6 and 2 mg L 1, respectively after 1 h. The control, with no added particles, was not affected by exposure to the air alone and the concentrations remained constant. The addition of particles to CMD from the Ynysarwed site in S Wales had similar effects. This site has an Fe concentration of 50 mg L 1, a pH of 6, and 1.6 mg L 1 dissolved O2. Air was added to initiate precipitation. The control experiment showed a decrease in Fe concentration, caused by this addition of air. The Fe dropped to 48 mg L 1 after 10 min, and 40 mg L 1 after an hour. The addition of particles accelerated ochre precipitation; 5 g L 1 of GR particles caused the concentration of Fe to reduce to 13 mg L 1 after 10 min, and 6 mg L 1 after an hour. Bwlch, a former Pb/Zn mine, has neutral (pH 6.6), low Fe (2.4 mg L 1), high Zn (21 mg L 1) discharge. FeSO4 was added to give 40 mg L 1 Fe. The addition of 5 g L 1 GR particles enabled the resulting rapid precipitation of Fe to scavenge the Zn. The Zn was reduced to 0.3 mg L 1 after 10 min, and 0.1 mg L 1 after an hour. The Fe was returned to its original concentration after 10 min, and after an hour was reduced to 1 mg L 1. The accelerated precipitation of Fe has the potential to enhance passive and/ or active treatment of mine waters. The produced ochre can be recycled back into the system to encourage more precipitation of Fe oxy-hydroxides from these toxic mine waters. The rapid nature of the precipitation causes co-precipitated elements to be absorbed, which generates a more stable solid waste. doi:10.1016/j.gca.2006.06.192
IFP, Dept. de Ge´ochimie, Rueil-Malmaison, France ([email protected]) 2 Universite´ Paris 6, CNRS-UMR 5143 ‘‘Pale´obiodiversite´ et Pale´oenvironnements’’; Paris, France 3 IPGP, Lab. Ge´ochimie et Cosmochimie, Paris, France 4 Facultad de Ciencias del Mar y Ambientales, Dept. Ciencias de la Tierra, Casem, Spain 5 Universidad de Granada, Dept. de Estratigrafia y Paleontologia, Granada, Spain A carbonate productivity crisis is recorded in western Tethys during the Early Bajocian (170 Ma) and coincides with the onset of biosiliceous sedimentation in several tethysian basins. A d13Ccarb positive excursion of regional extent preceded the crisis (Bartolini et al., 1996; Bartolini and Cecca, 1999) giving evidence of a global perturbation of the carbon cycle. The birth of the Pacific Plate and also a major pulse of subduction related magmatism (Bartolini and Larson, 2001) may have triggered an increase of atmospheric CO2 level at this period, while opening of the Liguro-Piemontese Ocean may have cause rearrangement of oceanic stream patterns of circulation. Bartolini and Larson (2001) suggest that these global conditions lead to eutrophication of marine environment and possibly acidification both inducing an ecological crisis for the main carbonate factories. In order to test the likelihood of proposed hypotheses, two sections of Early Bajocian age were investigated according to a geochemical multi-proxy approach. The first section from the Subbetic realm (South Spain) is characterized by calcareous marly alternation deposited in hemipelagic environment. The second section from Umbria-Marche area is constituted by mudstones and cherts deposited in a pelagic environment. Geochemical data acquired include d13Corg, d15Norg, 87Sr/86Sr d11B. Results suggest an acidification of oceanic water concommittant with the carbon isotope excursion, while primary productivity appears perturbated with no evidence of anoxic event.
References Bartolini, A., Baumgartner, P.O., Hunziker, J., 1996. Eclogae geol. Helv. 89 (2), 811–844. Bartolini, A., Cecca, F., 1999. CRAS 329, 587–595. Bartolini, A., Larson, R., 2001. Geology 29 (8), 735–738. doi:10.1016/j.gca.2006.06.193
Goldschmidt Conference Abstracts 2006
Accelerated precipitation of ochre for mine water remediation
A multi-proxy approach of the Bajocian sedimentary crisis in western Tethys
J.M. BEARCOCK, W.T. PERKINS
V. BEAUMONT1, A. BARTOLINI2, R. MAS1, S. GARDIN2, J. GAILLARDET3, B. CHETELAT3, L. O’DOGHERTY4, J. SANDOVAL5, F. CECCA2
Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, UK ([email protected]; [email protected]) 1
Metal-rich mine drainage is a worldwide environmental problem, its treatment can be passive or active. This paper discusses a series of laboratory scale experiments which investigated the accelerated precipitation of ochre for the treatment of metal-rich mine waters. A variety of naturally occurring Fe oxy-hydroxides, a problematic waste material, have been collected from mine discharges. These were added to a range of mine waters to investigate accelerated precipitation of ochre as a remediation method. This removes Fe which co-precipitates elements from the drainage solution. The most effective ‘‘ochre’’, green rust (GR), is discussed here. Results: Parys Mountain, N Wales, is an example of a metalrich AMD discharge with a pH of 2.7. The raw water contains 75 mg L 1 Fe and 24 mg L 1 Zn. GR particles, at 5 g L 1, were added, accelerating precipitation. Dissolved Fe and Zn were rapidly reduced to 12 and 5 mg L 1, respectively after 10 min, and to 6 and 2 mg L 1, respectively after 1 h. The control, with no added particles, was not affected by exposure to the air alone and the concentrations remained constant. The addition of particles to CMD from the Ynysarwed site in S Wales had similar effects. This site has an Fe concentration of 50 mg L 1, a pH of 6, and 1.6 mg L 1 dissolved O2. Air was added to initiate precipitation. The control experiment showed a decrease in Fe concentration, caused by this addition of air. The Fe dropped to 48 mg L 1 after 10 min, and 40 mg L 1 after an hour. The addition of particles accelerated ochre precipitation; 5 g L 1 of GR particles caused the concentration of Fe to reduce to 13 mg L 1 after 10 min, and 6 mg L 1 after an hour. Bwlch, a former Pb/Zn mine, has neutral (pH 6.6), low Fe (2.4 mg L 1), high Zn (21 mg L 1) discharge. FeSO4 was added to give 40 mg L 1 Fe. The addition of 5 g L 1 GR particles enabled the resulting rapid precipitation of Fe to scavenge the Zn. The Zn was reduced to 0.3 mg L 1 after 10 min, and 0.1 mg L 1 after an hour. The Fe was returned to its original concentration after 10 min, and after an hour was reduced to 1 mg L 1. The accelerated precipitation of Fe has the potential to enhance passive and/ or active treatment of mine waters. The produced ochre can be recycled back into the system to encourage more precipitation of Fe oxy-hydroxides from these toxic mine waters. The rapid nature of the precipitation causes co-precipitated elements to be absorbed, which generates a more stable solid waste. doi:10.1016/j.gca.2006.06.192
IFP, Dept. de Ge´ochimie, Rueil-Malmaison, France ([email protected]) 2 Universite´ Paris 6, CNRS-UMR 5143 ‘‘Pale´obiodiversite´ et Pale´oenvironnements’’; Paris, France 3 IPGP, Lab. Ge´ochimie et Cosmochimie, Paris, France 4 Facultad de Ciencias del Mar y Ambientales, Dept. Ciencias de la Tierra, Casem, Spain 5 Universidad de Granada, Dept. de Estratigrafia y Paleontologia, Granada, Spain A carbonate productivity crisis is recorded in western Tethys during the Early Bajocian (170 Ma) and coincides with the onset of biosiliceous sedimentation in several tethysian basins. A d13Ccarb positive excursion of regional extent preceded the crisis (Bartolini et al., 1996; Bartolini and Cecca, 1999) giving evidence of a global perturbation of the carbon cycle. The birth of the Pacific Plate and also a major pulse of subduction related magmatism (Bartolini and Larson, 2001) may have triggered an increase of atmospheric CO2 level at this period, while opening of the Liguro-Piemontese Ocean may have cause rearrangement of oceanic stream patterns of circulation. Bartolini and Larson (2001) suggest that these global conditions lead to eutrophication of marine environment and possibly acidification both inducing an ecological crisis for the main carbonate factories. In order to test the likelihood of proposed hypotheses, two sections of Early Bajocian age were investigated according to a geochemical multi-proxy approach. The first section from the Subbetic realm (South Spain) is characterized by calcareous marly alternation deposited in hemipelagic environment. The second section from Umbria-Marche area is constituted by mudstones and cherts deposited in a pelagic environment. Geochemical data acquired include d13Corg, d15Norg, 87Sr/86Sr d11B. Results suggest an acidification of oceanic water concommittant with the carbon isotope excursion, while primary productivity appears perturbated with no evidence of anoxic event.
References Bartolini, A., Baumgartner, P.O., Hunziker, J., 1996. Eclogae geol. Helv. 89 (2), 811–844. Bartolini, A., Cecca, F., 1999. CRAS 329, 587–595. Bartolini, A., Larson, R., 2001. Geology 29 (8), 735–738. doi:10.1016/j.gca.2006.06.193