The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Charles Madic - One of the best experts on this subject based on the ideXlab platform.
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Acidic organophosphorus solvent extraction process for the purification of molybdenum in tailings from uranium Ore Treatment
Hydrometallurgy, 1997Co-Authors: Cecile Brassier-lecarme, Pascal Baron, Jean Louis Chevalier, Charles MadicAbstract:Abstract Uranium Ore often contains a significant amount of molybdenum. The main by-product of uranium extraction is an impure calcium molybdate, whose recovery could justify the development of a liquid-liquid extraction process. The knowledge of the behavior of heteropolymolybdic species in acidic solutions was exploited to investigate the use of an organophosphorus extractant to extract molybdenum from dissolution liquors of impure calcium molybdate, residues from uranium Ore Treatment. An organophosphorus solvent extraction process is proposed to recover and purify 99.7% of the molybdenum from the initial residue, free from the impurities P, V, and Si.
Gerard Blanc - One of the best experts on this subject based on the ideXlab platform.
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long term records of cadmium and silver contamination in sediments and oysters from the gironde fluvial estuarine continuum evidence of changing silver sources
Chemosphere, 2011Co-Authors: Laurent Lanceleur, Gerard Blanc, Jorg Schafer, Jeanfrancois Chiffoleau, Dominique Auger, Sophie Renault, Magalie Baudrimont, Stephane AudryAbstract:Abstract The Gironde fluvial estuarine system is impacted by historic metal pollution (e.g. Cd, Zn, Hg) and oysters ( Crassostrea gigas ) from the estuary mouth have shown extremely high Cd concentrations for decades. Based on recent work ( Chiffoleau et al., 2005 ) revealing anomalously high Ag concentrations (up to 65 mg kg −1 ; dry weight) in Gironde oysters, we compared long-term (∼1955–2001) records of Ag and Cd concentrations in reservoir sediment with the respective concentrations in oysters collected between 1979 and 2010 to identify the origin and historical trend of the recently discovered Ag anomaly. Sediment cOres from two reservoirs upstream and downstream from the main metal pollution source provided information on (i) geochemical background (upstream; Ag: ∼0.3 mg kg −1 ; Cd: ∼0.8 mg kg −1 ) and (ii) historical trends in Ag and Cd pollution. The results showed parallel concentration-depth profiles of Ag and Cd supporting a common source and transport. Decreasing concentrations since 1986 (Cd: from 300 to 11 mg kg −1 ; Ag: from 6.7 to 0.43 mg kg −1 ) reflected the termination of Zn Ore Treatment in the Decazeville basin followed by remediation actions. Accordingly, Cd concentrations in oysters decreased after 1988 (from 109 to 26 mg kg −1 , dry weight (dw)), while Ag bioaccumulation increased from 38 up to 116 mg kg −1 , dw after 1993. Based on the Cd/Ag ratio (Cd/Ag ∼ 2) in oysters sampled befOre the termination of zinc Ore Treatment (1981–1985) and assuming that nearly all Cd in oysters originated from the metal point source, we estimated the respective contribution of Ag from this source to Ag concentrations in oysters. The evolution over the past 30 years clearly suggested that the recent, unexplained Ag concentrations in oysters are due to increasing contributions (>70% after 1999) by other sources, such as photography, electronics and emerging Ag applications/materials.
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Silver fluxes to the Gironde Estuary - Eleven years (1999-2009) of monitoring at the watershed scale
Applied Geochemistry, 2011Co-Authors: Laurent Lanceleur, Alexandra Coynel, Jorg Schafer, Cécile Bossy, Aurélie Larrose, Matthieu Masson, Gerard BlancAbstract:Abstract Although Ag has long been recognized as highly toxic to aquatic organisms and as an efficient tracer of urban wastewater inputs, there are very few data available on Ag levels and fluxes in rivers and estuaries. Due to anomalously high Ag concentrations in oysters from the estuary mouth, dissolved (Ag D ) and particulate Ag (Ag P ) concentrations in rivers of the Gironde Estuary watershed were studied. Using daily discharge, Suspended particulate matter (SPM) data and monthly measured Ag D and Ag P , the respective fluxes were estimated at the three main entries of the Gironde Estuary and at selected key sites at the outlets of different sub-watersheds for multiple years of the past decade. Dissolved and particulate Ag concentrations were 0.5 ng/L (detection limit) to 5.7 ng/L and 0.13–13.9 mg/kg in all rivers, except for the Riou-Mort River (up to 1260 ng/L and 261 mg/kg) that has been heavily polluted by former Zn Ore Treatment and remaining waste tailings. At all sites Ag transport mainly (73–100%) occurred in the particulate phase, i.e. strongly depended on hydrological parameters. Comparing Th-normalised (i.e. grain size independent) Ag P levels at the different sites including one remote site showed that the regional background is best described by Ag P /Th P = 0.026. The anthropogenic components in Ag P levels and fluxes ranged from 24% to 90% at all sites, except for the Riou-Mort River (81–99%). Although this former Ore Treatment site still is an evident Ag source to the Lot-Garonne fluvial–estuarine system, its contribution to Ag fluxes at the main entry of the Gironde Estuary (i.e. 0.33–2.44 t/a at the La Reole site) is 2 /a and 0.028–6.05 g/person/a, respectively. The results obtained suggest that the Gironde fluvial–estuarine system is contaminated by Ag inputs from various sources, but further work is necessary to (i) identify and quantify the major sources and (ii) produce comparable data for other systems, which would be useful for the evaluation of Ag contamination at a larger scale.
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groundwater contributions to metal transport in a small river affected by mining and smelting waste
Water Research, 2007Co-Authors: Alexandra Coynel, Aymeric Dabrin, Naig Girardot, Jorg Schafer, Gerard BlancAbstract:Abstract The Riou Mort watershed, strongly affected by former coal mining and Zn Ore Treatment, has been the major source of the historical polymetallic pollution of the Lot–Garonne–Gironde fluvial–estuarine system. Two decades after the end of Ore Treatment, the former industrial area still contributes important amounts of metals/metalloids from various, partly unidentified, sources to the downstream river system. This study presents the high spatial variability of metal/metalloid (Cd, Zn, As, Sb, U, V) concentrations in water and suspended particulate matter (SPM) from eight observation sites during a short, intense flood event. Despite important dilution effects, the observed concentration levels at the different sites suggested additional Cd and Zn inputs, probably from polluted groundwater. This formerly unknown metal source was then localized and characterized by sampling water and SPM along two longitudinal profiles during different hydrological situations. Groundwater inputs of “truly dissolved” ( −1 , respectively) in the source zone were consistent with values measured in samples from the near aquifer (5400–13,000 and 200,000–400,000 μg l −1 ). The present work induced concrete remediation actions (pumping and Treatment of the polluted groundwater), that are expected to strongly reduce dissolved Cd and Zn emissions into the Riou Mort River.
Cecile Brassier-lecarme - One of the best experts on this subject based on the ideXlab platform.
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Acidic organophosphorus solvent extraction process for the purification of molybdenum in tailings from uranium Ore Treatment
Hydrometallurgy, 1997Co-Authors: Cecile Brassier-lecarme, Pascal Baron, Jean Louis Chevalier, Charles MadicAbstract:Abstract Uranium Ore often contains a significant amount of molybdenum. The main by-product of uranium extraction is an impure calcium molybdate, whose recovery could justify the development of a liquid-liquid extraction process. The knowledge of the behavior of heteropolymolybdic species in acidic solutions was exploited to investigate the use of an organophosphorus extractant to extract molybdenum from dissolution liquors of impure calcium molybdate, residues from uranium Ore Treatment. An organophosphorus solvent extraction process is proposed to recover and purify 99.7% of the molybdenum from the initial residue, free from the impurities P, V, and Si.
Gilles Colinet - One of the best experts on this subject based on the ideXlab platform.
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Soil contamination near a former Zn-Pb Ore-Treatment plant: Evaluation of deterministic factors and spatial structures at the landscape scale
Journal of Geochemical Exploration, 2014Co-Authors: Amandine Liénard, Yves Brostaux, Gilles ColinetAbstract:Abstract Historical soil contamination within a 3 km radius of a former Ore Treatment plant was evaluated. A total of 247 topsoil samples were collected in a stratified random sampling design taking into account three factors: land use (LU), soil type (ST) and wind direction (WD). Concentrations of trace elements (Cd, Co, Cr, Cu, Ni, Pb and Zn) and major elements (Ca, Mg, K, Fe, Al, Mn) as well as various soil properties (pH water , pH KCl , TOC and N) were measured. Total Cd, Pb and Zn concentrations were higher than typical background values. Enrichment factors for these three metals were, respectively, 260, 77.4 and 35.5. Principal component analysis (PCA) and factor analysis segregated anthropogenic contamination as a premier factor in influencing concentrations, followed by a second lithogenic factor. The anthropogenic origin of substantial contamination was confirmed through mapping of sample locations relative to contaminant sources. Factor 1 (26.5% of the variance) impacts a large area around the contaminated site and is also indicative of WD influence. Factor 2 (23.9% of the variance) is naturally linked to the local lithology and geology. LU and soil fertility are, respectively, represented by factor 3 (16.5% of the variance), which is linked to pH, and factor 4 (9.3% of the variance), related to organic content. The significance of landscape factors in the spatial distribution of metallic trace elements (MTE) was assessed with an ANCOVA using “distance to the source” as a covariate. Results of the analysis support the hypothesis that Cd, Cu, Pb and Zn concentrations are mainly driven by anthropogenic factors, specifically historical industrial activity at the former Ore Treatment plant. The ANCOVA also provides a means to quantify the impact of LU and ST as well, particularly on MTE availability in soils. The presence of MTE in soil poses known, and potentially significant, risks to both human health and the environment.
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PhytOremediation of contaminated sites in urban environment : preliminary results of a study focussed on Lubumbashi.
2007Co-Authors: Gilles Colinet, Layla Saad, Alfred Cubaka, Michel Ngongo, Grégory Mahy, Nathalie Verbruggen, Laurent Bock, Pierre Jacques MeertsAbstract:A specific flora has developped in Central Africa on soils which are naturally rich in Cu and Co. Mining and Ore Treatment activities in the Katanga province (RDC) have generated contaminations which endanger ecosystem viability and/or human health. A survey of edaphic conditions prevailing for plant growing on natural metalliferous outcrops, the « copper hills », in mining sites (quarries), and in contaminated areas around metal smelters, is conducted as a first stage of a phytOremediation-based research programme. Soluble, available and total content in some metallic trace elements have been measured. The first results show a relatively high heterogeneity inside and between sites. But the main finding is related to the very different nature of contamination between the three types of sites. This point constitutes an additionnal difficulty that should be taken into account for the selection of metallophytic species from the copper hills or the quarries in order to vegetalize a site contaminated by atmospheric fall outs from metal smelters in Lubumbashi.
Jorg Schafer - One of the best experts on this subject based on the ideXlab platform.
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long term records of cadmium and silver contamination in sediments and oysters from the gironde fluvial estuarine continuum evidence of changing silver sources
Chemosphere, 2011Co-Authors: Laurent Lanceleur, Gerard Blanc, Jorg Schafer, Jeanfrancois Chiffoleau, Dominique Auger, Sophie Renault, Magalie Baudrimont, Stephane AudryAbstract:Abstract The Gironde fluvial estuarine system is impacted by historic metal pollution (e.g. Cd, Zn, Hg) and oysters ( Crassostrea gigas ) from the estuary mouth have shown extremely high Cd concentrations for decades. Based on recent work ( Chiffoleau et al., 2005 ) revealing anomalously high Ag concentrations (up to 65 mg kg −1 ; dry weight) in Gironde oysters, we compared long-term (∼1955–2001) records of Ag and Cd concentrations in reservoir sediment with the respective concentrations in oysters collected between 1979 and 2010 to identify the origin and historical trend of the recently discovered Ag anomaly. Sediment cOres from two reservoirs upstream and downstream from the main metal pollution source provided information on (i) geochemical background (upstream; Ag: ∼0.3 mg kg −1 ; Cd: ∼0.8 mg kg −1 ) and (ii) historical trends in Ag and Cd pollution. The results showed parallel concentration-depth profiles of Ag and Cd supporting a common source and transport. Decreasing concentrations since 1986 (Cd: from 300 to 11 mg kg −1 ; Ag: from 6.7 to 0.43 mg kg −1 ) reflected the termination of Zn Ore Treatment in the Decazeville basin followed by remediation actions. Accordingly, Cd concentrations in oysters decreased after 1988 (from 109 to 26 mg kg −1 , dry weight (dw)), while Ag bioaccumulation increased from 38 up to 116 mg kg −1 , dw after 1993. Based on the Cd/Ag ratio (Cd/Ag ∼ 2) in oysters sampled befOre the termination of zinc Ore Treatment (1981–1985) and assuming that nearly all Cd in oysters originated from the metal point source, we estimated the respective contribution of Ag from this source to Ag concentrations in oysters. The evolution over the past 30 years clearly suggested that the recent, unexplained Ag concentrations in oysters are due to increasing contributions (>70% after 1999) by other sources, such as photography, electronics and emerging Ag applications/materials.
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Silver fluxes to the Gironde Estuary - Eleven years (1999-2009) of monitoring at the watershed scale
Applied Geochemistry, 2011Co-Authors: Laurent Lanceleur, Alexandra Coynel, Jorg Schafer, Cécile Bossy, Aurélie Larrose, Matthieu Masson, Gerard BlancAbstract:Abstract Although Ag has long been recognized as highly toxic to aquatic organisms and as an efficient tracer of urban wastewater inputs, there are very few data available on Ag levels and fluxes in rivers and estuaries. Due to anomalously high Ag concentrations in oysters from the estuary mouth, dissolved (Ag D ) and particulate Ag (Ag P ) concentrations in rivers of the Gironde Estuary watershed were studied. Using daily discharge, Suspended particulate matter (SPM) data and monthly measured Ag D and Ag P , the respective fluxes were estimated at the three main entries of the Gironde Estuary and at selected key sites at the outlets of different sub-watersheds for multiple years of the past decade. Dissolved and particulate Ag concentrations were 0.5 ng/L (detection limit) to 5.7 ng/L and 0.13–13.9 mg/kg in all rivers, except for the Riou-Mort River (up to 1260 ng/L and 261 mg/kg) that has been heavily polluted by former Zn Ore Treatment and remaining waste tailings. At all sites Ag transport mainly (73–100%) occurred in the particulate phase, i.e. strongly depended on hydrological parameters. Comparing Th-normalised (i.e. grain size independent) Ag P levels at the different sites including one remote site showed that the regional background is best described by Ag P /Th P = 0.026. The anthropogenic components in Ag P levels and fluxes ranged from 24% to 90% at all sites, except for the Riou-Mort River (81–99%). Although this former Ore Treatment site still is an evident Ag source to the Lot-Garonne fluvial–estuarine system, its contribution to Ag fluxes at the main entry of the Gironde Estuary (i.e. 0.33–2.44 t/a at the La Reole site) is 2 /a and 0.028–6.05 g/person/a, respectively. The results obtained suggest that the Gironde fluvial–estuarine system is contaminated by Ag inputs from various sources, but further work is necessary to (i) identify and quantify the major sources and (ii) produce comparable data for other systems, which would be useful for the evaluation of Ag contamination at a larger scale.
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groundwater contributions to metal transport in a small river affected by mining and smelting waste
Water Research, 2007Co-Authors: Alexandra Coynel, Aymeric Dabrin, Naig Girardot, Jorg Schafer, Gerard BlancAbstract:Abstract The Riou Mort watershed, strongly affected by former coal mining and Zn Ore Treatment, has been the major source of the historical polymetallic pollution of the Lot–Garonne–Gironde fluvial–estuarine system. Two decades after the end of Ore Treatment, the former industrial area still contributes important amounts of metals/metalloids from various, partly unidentified, sources to the downstream river system. This study presents the high spatial variability of metal/metalloid (Cd, Zn, As, Sb, U, V) concentrations in water and suspended particulate matter (SPM) from eight observation sites during a short, intense flood event. Despite important dilution effects, the observed concentration levels at the different sites suggested additional Cd and Zn inputs, probably from polluted groundwater. This formerly unknown metal source was then localized and characterized by sampling water and SPM along two longitudinal profiles during different hydrological situations. Groundwater inputs of “truly dissolved” ( −1 , respectively) in the source zone were consistent with values measured in samples from the near aquifer (5400–13,000 and 200,000–400,000 μg l −1 ). The present work induced concrete remediation actions (pumping and Treatment of the polluted groundwater), that are expected to strongly reduce dissolved Cd and Zn emissions into the Riou Mort River.
