Dépouillements

Kinetics of saprolitic laterite leaching by sulphuric acid at atmospheric pressure / Wei Luo in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 458–462 Titre : Kinetics of saprolitic laterite leaching by sulphuric acid at atmospheric pressure Type de document : texte imprimé Auteurs : Wei Luo, Auteur ; Qiming Feng, Auteur ; Leming Ou, Auteur Année de publication : 2011 Article en page(s) : pp. 458–462 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Oxide  ores  Ore  mineralogy  Leaching  Reaction  kinetics Résumé : Mineralogical analyses of the saprolitic laterite material have been characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermal analysis, scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). Results showed that the saprolitic laterite material consists mainly of nickel-substituted lizardite showing the pebble-like morphology and traces of magnetite and phlogopite. Leaching results showed that as much as 84.8% nickel could be leached under the experimental conditions of 10% (v/v) H2SO4, 90 °C reaction temperature, leached within 5 min, particle size d50 = 25 μm, stirring at 500 rpm and liquid to solid ratio 3:1. The kinetics of nickel and magnesium leaching from the saprolitic laterite material have been investigated in a mechanically stirred reactor and the activation energies were determined to be 53.9 kJ mol−1 for nickel and 59.4 kJ mol−1 for magnesium respectively, which are characteristic for a chemical reaction controlled process. The similarity of the activation energies of nickel and magnesium leaching from the saprolitic laterite material by sulphuric acid means that nickel in lizardite is loosely bound within the octahedral layer and almost all of the nickel could be leached simultaneously with magnesium but without complete decomposition of the silicate structure. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268750900260X [article] Kinetics of saprolitic laterite leaching by sulphuric acid at atmospheric pressure [texte imprimé] / Wei Luo, Auteur ; Qiming Feng, Auteur ; Leming Ou, Auteur . - 2011 . - pp. 458–462. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 458–462 Mots-clés : Oxide  ores  Ore  mineralogy  Leaching  Reaction  kinetics Résumé : Mineralogical analyses of the saprolitic laterite material have been characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermal analysis, scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). Results showed that the saprolitic laterite material consists mainly of nickel-substituted lizardite showing the pebble-like morphology and traces of magnetite and phlogopite. Leaching results showed that as much as 84.8% nickel could be leached under the experimental conditions of 10% (v/v) H2SO4, 90 °C reaction temperature, leached within 5 min, particle size d50 = 25 μm, stirring at 500 rpm and liquid to solid ratio 3:1. The kinetics of nickel and magnesium leaching from the saprolitic laterite material have been investigated in a mechanically stirred reactor and the activation energies were determined to be 53.9 kJ mol−1 for nickel and 59.4 kJ mol−1 for magnesium respectively, which are characteristic for a chemical reaction controlled process. The similarity of the activation energies of nickel and magnesium leaching from the saprolitic laterite material by sulphuric acid means that nickel in lizardite is loosely bound within the octahedral layer and almost all of the nickel could be leached simultaneously with magnesium but without complete decomposition of the silicate structure. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268750900260X

Single and binary component sorption of the fission products Sr2+, Cs+ and Co2+ from aqueous solutions onto sulphate reducing bacteria / N. Ngwenya in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 463–470 Titre : Single and binary component sorption of the fission products Sr2+, Cs+ and Co2+ from aqueous solutions onto sulphate reducing bacteria Type de document : texte imprimé Auteurs : N. Ngwenya, Auteur ; E. M. N. Chirwa, Auteur Année de publication : 2011 Article en page(s) : pp. 463–470 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Spent  fuel  reprocessing  Sulphate  reducing  bacteria  Nuclear  waste  processing Résumé : This study investigates the removal of the fission products Sr2+, Cs+ and Co2+ in single and binary metal solutions by a sulphate reducing bacteria (SRB) biomass. The effect of initial concentration and pH on the sorption kinetics of each metal was evaluated in single metal solutions. Binary component equilibrium sorption studies were performed to investigate the competitive binding behaviour of each metal in the presence of a secondary metal ion. Results obtained from single metal equilibrium sorption studies indicated that SRB have a higher binding capacity for Sr2+ (qmax = 416.7 mg g−1), followed by Cs+ (qmax = 238.1 mg g−1), and lastly Co2+ (qmax = 204.1 mg g−1). Among the binary systems investigated, Co2+ uptake was the most sensitive, resulting in a 76% reduction of the sorption capacity (qmax) in the presence of Cs+. These findings are significant for future development of effective biological processes for radioactive waste management under realistic conditions. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509002842 [article] Single and binary component sorption of the fission products Sr2+, Cs+ and Co2+ from aqueous solutions onto sulphate reducing bacteria [texte imprimé] / N. Ngwenya, Auteur ; E. M. N. Chirwa, Auteur . - 2011 . - pp. 463–470. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 463–470 Mots-clés : Spent  fuel  reprocessing  Sulphate  reducing  bacteria  Nuclear  waste  processing Résumé : This study investigates the removal of the fission products Sr2+, Cs+ and Co2+ in single and binary metal solutions by a sulphate reducing bacteria (SRB) biomass. The effect of initial concentration and pH on the sorption kinetics of each metal was evaluated in single metal solutions. Binary component equilibrium sorption studies were performed to investigate the competitive binding behaviour of each metal in the presence of a secondary metal ion. Results obtained from single metal equilibrium sorption studies indicated that SRB have a higher binding capacity for Sr2+ (qmax = 416.7 mg g−1), followed by Cs+ (qmax = 238.1 mg g−1), and lastly Co2+ (qmax = 204.1 mg g−1). Among the binary systems investigated, Co2+ uptake was the most sensitive, resulting in a 76% reduction of the sorption capacity (qmax) in the presence of Cs+. These findings are significant for future development of effective biological processes for radioactive waste management under realistic conditions. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509002842

Effect of chloride ions on leaching rate of chalcopyrite / Kyoungkeun Yoo in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 471–477 Titre : Effect of chloride ions on leaching rate of chalcopyrite Type de document : texte imprimé Auteurs : Kyoungkeun Yoo, Auteur ; Soo-kyung Kim, Auteur ; Jae-chun Lee, Auteur Année de publication : 2011 Article en page(s) : pp. 471–477 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Chalcopyrite  leaching  Chloride  leaching  solution  Chlorocuprate(I)  Cuprous  ion Résumé : The effect of chloride on chalcopyrite leaching has been investigated by performing batch leaching tests with three kinds of leaching solutions and using Hiroyoshi’s model, which suggests that a zone of rapid leaching exists between the critical potential (Ec, equilibrium redox potential for the reduction of CuFeS2 to Cu2S) and the oxidation potential (Eox, equilibrium redox potential for the oxidation of Cu2S). The results of the leaching tests show that the leaching rate in hydrochloric acid solution is the fastest and that the relationship between the Cu leaching rate and oxidation–reduction potential (ORP) follows Hiroyoshi’s model. Thermodynamic calculations indicate that, with an increase in the chloride concentration, the concentration of cuprous ions increases as the chlorocuprate(I) complex ions are formed and the contribution of cuprous ions to the critical potential is greater than that of cupric ions, even though the concentration of cuprous ions is lower than that of cupric ions. This fact suggests that the formation of chlorocuprate(I) ions in a chloride solution may improve the chalcopyrite leaching rate by increasing the critical potential. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509002854 [article] Effect of chloride ions on leaching rate of chalcopyrite [texte imprimé] / Kyoungkeun Yoo, Auteur ; Soo-kyung Kim, Auteur ; Jae-chun Lee, Auteur . - 2011 . - pp. 471–477. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 471–477 Mots-clés : Chalcopyrite  leaching  Chloride  leaching  solution  Chlorocuprate(I)  Cuprous  ion Résumé : The effect of chloride on chalcopyrite leaching has been investigated by performing batch leaching tests with three kinds of leaching solutions and using Hiroyoshi’s model, which suggests that a zone of rapid leaching exists between the critical potential (Ec, equilibrium redox potential for the reduction of CuFeS2 to Cu2S) and the oxidation potential (Eox, equilibrium redox potential for the oxidation of Cu2S). The results of the leaching tests show that the leaching rate in hydrochloric acid solution is the fastest and that the relationship between the Cu leaching rate and oxidation–reduction potential (ORP) follows Hiroyoshi’s model. Thermodynamic calculations indicate that, with an increase in the chloride concentration, the concentration of cuprous ions increases as the chlorocuprate(I) complex ions are formed and the contribution of cuprous ions to the critical potential is greater than that of cupric ions, even though the concentration of cuprous ions is lower than that of cupric ions. This fact suggests that the formation of chlorocuprate(I) ions in a chloride solution may improve the chalcopyrite leaching rate by increasing the critical potential. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509002854

Study of the deterioration of acid resins in cyclic duty / A.B. Nesbitt in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 478–485 Titre : Study of the deterioration of acid resins in cyclic duty Type de document : texte imprimé Auteurs : A.B. Nesbitt, Auteur Année de publication : 2011 Article en page(s) : pp. 478–485 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Hydrometallurgy  Ion  exchange  Oxidation Résumé : Two case studies are presented in which a continuous loss of capacity in two samples of acid resin, are observed over 900 cycles of loading and regeneration. By completing the batch kinetic testing of the resin at different turbulences and calculating the intra-particle diffusion rates of the counter and co-ion, the effect of turbulence on the independence/dependence of the intra-particle diffusion could be established. A systematic loss in capacity and change in kinetics is reported in both case studies and it is postulated that the reason for this is the loss of active sites within the resin matrix. The significance of this observation is that standard tests done for a new resin application could significantly overestimate the commercial performance of the resin concerned. This paper proposes a method in which resin might be studied prior to inclusion in a particular process, with the objective of determining its effective life span. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509002957 [article] Study of the deterioration of acid resins in cyclic duty [texte imprimé] / A.B. Nesbitt, Auteur . - 2011 . - pp. 478–485. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 478–485 Mots-clés : Hydrometallurgy  Ion  exchange  Oxidation Résumé : Two case studies are presented in which a continuous loss of capacity in two samples of acid resin, are observed over 900 cycles of loading and regeneration. By completing the batch kinetic testing of the resin at different turbulences and calculating the intra-particle diffusion rates of the counter and co-ion, the effect of turbulence on the independence/dependence of the intra-particle diffusion could be established. A systematic loss in capacity and change in kinetics is reported in both case studies and it is postulated that the reason for this is the loss of active sites within the resin matrix. The significance of this observation is that standard tests done for a new resin application could significantly overestimate the commercial performance of the resin concerned. This paper proposes a method in which resin might be studied prior to inclusion in a particular process, with the objective of determining its effective life span. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509002957

In situ investigation and visualisation of microbial attachment and colonisation in a heap bioleach environment / Cindy-Jade Africa in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 486–491 Titre : In situ investigation and visualisation of microbial attachment and colonisation in a heap bioleach environment : The novel biofilm reactor Type de document : texte imprimé Auteurs : Cindy-Jade Africa, Auteur ; Susan T.L. Harrison, Auteur ; Megan Becker, Auteur Année de publication : 2011 Article en page(s) : pp. 486–491 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Bioleaching  Microbial  attachment  Biofilm  A.  ferrooxidans  L.  ferriphilum  Fluorescent  in  situ  hybridisation Résumé : In this paper, the development of a novel means of investigating the attachment and subsequent biofilm formation of mineral bioleaching micro-organisms to mineral surfaces in situ is described. The protocol was developed to investigate the interactions of micro-organisms with sulfide minerals and low-grade chalcopyrite ore under conditions resemblant of a bioheap environment. The method makes use of a biofilm reactor in which thin sections of mineral ore are mounted. The reactor is operated as a continuous flow-through system. Attachment of pure and mixed cultures of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum is assessed. The technique allows for the investigation of microbial ecology with special regard to microbe–mineral attachment, site and mineral specific associations of micro-organisms and spatial organisation of microbial communities present through the use of fluorescent microscopy techniques. Preliminary fluorescent in situ hybridisation (FISH) analysis of the attachment of L. ferriphilum and A. ferrooxidans to massive chalcopyrite sections, as well as to low-grade chalcopyrite containing ore sections is presented. In the case of both low-grade and massive sulfide mineral samples, attachment of mixed micro-colonies was observed in regions where surface defects were prevalent. In low-grade samples, preferential attachment was observed in regions where sulfide minerals were present. The density of the attached micro-colonies increased with an increase in contacting time (from 20, 72 and 96 h) and was indicative of an actively growing mono-layered biofilm. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509003203 [article] In situ investigation and visualisation of microbial attachment and colonisation in a heap bioleach environment : The novel biofilm reactor [texte imprimé] / Cindy-Jade Africa, Auteur ; Susan T.L. Harrison, Auteur ; Megan Becker, Auteur . - 2011 . - pp. 486–491. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 486–491 Mots-clés : Bioleaching  Microbial  attachment  Biofilm  A.  ferrooxidans  L.  ferriphilum  Fluorescent  in  situ  hybridisation Résumé : In this paper, the development of a novel means of investigating the attachment and subsequent biofilm formation of mineral bioleaching micro-organisms to mineral surfaces in situ is described. The protocol was developed to investigate the interactions of micro-organisms with sulfide minerals and low-grade chalcopyrite ore under conditions resemblant of a bioheap environment. The method makes use of a biofilm reactor in which thin sections of mineral ore are mounted. The reactor is operated as a continuous flow-through system. Attachment of pure and mixed cultures of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum is assessed. The technique allows for the investigation of microbial ecology with special regard to microbe–mineral attachment, site and mineral specific associations of micro-organisms and spatial organisation of microbial communities present through the use of fluorescent microscopy techniques. Preliminary fluorescent in situ hybridisation (FISH) analysis of the attachment of L. ferriphilum and A. ferrooxidans to massive chalcopyrite sections, as well as to low-grade chalcopyrite containing ore sections is presented. In the case of both low-grade and massive sulfide mineral samples, attachment of mixed micro-colonies was observed in regions where surface defects were prevalent. In low-grade samples, preferential attachment was observed in regions where sulfide minerals were present. The density of the attached micro-colonies increased with an increase in contacting time (from 20, 72 and 96 h) and was indicative of an actively growing mono-layered biofilm. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509003203

Development of a process for the separation of zinc and copper from sulfuric liquor obtained from the leaching of an industrial residue by solvent extraction / Ligiane R. Gouvea in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 492–497 Titre : Development of a process for the separation of zinc and copper from sulfuric liquor obtained from the leaching of an industrial residue by solvent extraction Type de document : texte imprimé Auteurs : Ligiane R. Gouvea, Auteur ; Carlos A. Morais, Auteur Année de publication : 2011 Article en page(s) : pp. 492–497 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Solvent  extraction  Extractive  metallurgy  Hydrometallurgy  Environmental Résumé : This paper describes a study of the separation of zinc and copper from the leach liquor generated in the treatment of the zinc residue (29.6 g/L Zn and 37.4 g/L Cu) by liquid–liquid extraction. In it, the influence of the extractant type and concentration, aqueous phase acidity, contact time and stripping agent concentration were investigated. Organophosphorus extractants (D2EHPA, IONQUEST®801 and CYANEX®272) and the chelating extractants (LIX®63, LIX®984N and LIX®612N-LV) were also investigated. The organophosphorus reagents are selective for zinc, while the chelating extractants are selective for copper. In the experiment, D2EHPA was found to be the best extractant. A sulfuric acid solution was used in the stripping study. Five continuous experiments were carried out until an optimal condition for the separation of the metals Zn and Cu was achieved. Experiment 5 was carried out in three extraction steps, three scrubbing stages and five stripping stages. In this experiment, a pregnant strip solution containing 125 g/L Zn and 0.01 g/L Cu was obtained and the concentration of the metals in the raffinate was 28.3 g/L Cu and 0.49 g/L Zn. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000026 [article] Development of a process for the separation of zinc and copper from sulfuric liquor obtained from the leaching of an industrial residue by solvent extraction [texte imprimé] / Ligiane R. Gouvea, Auteur ; Carlos A. Morais, Auteur . - 2011 . - pp. 492–497. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 492–497 Mots-clés : Solvent  extraction  Extractive  metallurgy  Hydrometallurgy  Environmental Résumé : This paper describes a study of the separation of zinc and copper from the leach liquor generated in the treatment of the zinc residue (29.6 g/L Zn and 37.4 g/L Cu) by liquid–liquid extraction. In it, the influence of the extractant type and concentration, aqueous phase acidity, contact time and stripping agent concentration were investigated. Organophosphorus extractants (D2EHPA, IONQUEST®801 and CYANEX®272) and the chelating extractants (LIX®63, LIX®984N and LIX®612N-LV) were also investigated. The organophosphorus reagents are selective for zinc, while the chelating extractants are selective for copper. In the experiment, D2EHPA was found to be the best extractant. A sulfuric acid solution was used in the stripping study. Five continuous experiments were carried out until an optimal condition for the separation of the metals Zn and Cu was achieved. Experiment 5 was carried out in three extraction steps, three scrubbing stages and five stripping stages. In this experiment, a pregnant strip solution containing 125 g/L Zn and 0.01 g/L Cu was obtained and the concentration of the metals in the raffinate was 28.3 g/L Cu and 0.49 g/L Zn. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000026

Thorium and uranium extraction from rare earth elements in monazite sulfuric acid liquor through solvent extraction / Janúbia C. B. S. Amaral in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 498–503 Titre : Thorium and uranium extraction from rare earth elements in monazite sulfuric acid liquor through solvent extraction Type de document : texte imprimé Auteurs : Janúbia C. B. S. Amaral, Auteur ; Carlos A. Morais, Auteur Année de publication : 2011 Article en page(s) : pp. 498–503 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Hidrometallurgy  Mineral  processing  Process  optimization  Extractive  metallurgy Résumé : This paper describes the process of extraction of thorium and uranium from the sulfuric liquor generated in the chemical monazite treatment through a solvent extraction technique. The influence of the extractant type and concentration, contact time between phases, type and concentration of the stripping solution and aqueous/organic volumetric ratio were investigated. The results indicated the possibility of extracting, simultaneously, thorium and uranium from a solvent containing a mixture of Primene JM-T and Alamine 336. The stripping was carried out with a hydrochloric acid solution. After selecting the best conditions for the process, a continuous experiment was carried out in a mixer-settler circuit using four stages in the extraction step, five stages of stripping and one stage of the solvent regeneration. A loaded stripping solution containing 29.3 g/L of ThO2 and 1.27 g/L of U3O8 was obtained. The metals content in the raffinate was below 0.001 g/L, indicating a thorium extraction of over 99.9% and a uranium extraction of 99.4%. The rare earths content in the raffinate was 38 g/L of RE2O3. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268751000004X [article] Thorium and uranium extraction from rare earth elements in monazite sulfuric acid liquor through solvent extraction [texte imprimé] / Janúbia C. B. S. Amaral, Auteur ; Carlos A. Morais, Auteur . - 2011 . - pp. 498–503. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 498–503 Mots-clés : Hidrometallurgy  Mineral  processing  Process  optimization  Extractive  metallurgy Résumé : This paper describes the process of extraction of thorium and uranium from the sulfuric liquor generated in the chemical monazite treatment through a solvent extraction technique. The influence of the extractant type and concentration, contact time between phases, type and concentration of the stripping solution and aqueous/organic volumetric ratio were investigated. The results indicated the possibility of extracting, simultaneously, thorium and uranium from a solvent containing a mixture of Primene JM-T and Alamine 336. The stripping was carried out with a hydrochloric acid solution. After selecting the best conditions for the process, a continuous experiment was carried out in a mixer-settler circuit using four stages in the extraction step, five stages of stripping and one stage of the solvent regeneration. A loaded stripping solution containing 29.3 g/L of ThO2 and 1.27 g/L of U3O8 was obtained. The metals content in the raffinate was below 0.001 g/L, indicating a thorium extraction of over 99.9% and a uranium extraction of 99.4%. The rare earths content in the raffinate was 38 g/L of RE2O3. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268751000004X

Determination of oxygen gas–liquid mass transfer rates in heap bioleach reactors / Jochen Petersen in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 504–510 Titre : Determination of oxygen gas–liquid mass transfer rates in heap bioleach reactors Type de document : texte imprimé Auteurs : Jochen Petersen, Auteur Année de publication : 2011 Article en page(s) : pp. 504–510 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Leaching  Heap  leaching  Bio-leaching  Oxygen  Gas–liquid  mass  transfer Résumé : A detailed experimental study is described which was conducted to determine the rate of oxygen gas–liquid mass transfer within the packed bed of heap bioleach reactors at different temperatures (22–68 °C), using the Na2SO3 method. The raw data was analysed using a simplified film mass transfer model, making corrections for oxygen solubility in concentrated solution and for increased water vapour partial pressure at elevated temperatures. The results compared favourably against two independent experimental leach studies, indicating kLa values between 33 and 46 h−1. The value varied with the particle size distribution of the packing, with kLa assuming larger values for those packings that had a higher fines contents. While kLa increases with temperature, the solubility of oxygen decreases simultaneously, resulting in net mass transfer rates being relatively unaffected by temperature in the range studied. This indicates that thermophile heap bioleach reactors are likely to operate under gas–liquid mass transfer limitations, especially at high altitude. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000075 [article] Determination of oxygen gas–liquid mass transfer rates in heap bioleach reactors [texte imprimé] / Jochen Petersen, Auteur . - 2011 . - pp. 504–510. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 504–510 Mots-clés : Leaching  Heap  leaching  Bio-leaching  Oxygen  Gas–liquid  mass  transfer Résumé : A detailed experimental study is described which was conducted to determine the rate of oxygen gas–liquid mass transfer within the packed bed of heap bioleach reactors at different temperatures (22–68 °C), using the Na2SO3 method. The raw data was analysed using a simplified film mass transfer model, making corrections for oxygen solubility in concentrated solution and for increased water vapour partial pressure at elevated temperatures. The results compared favourably against two independent experimental leach studies, indicating kLa values between 33 and 46 h−1. The value varied with the particle size distribution of the packing, with kLa assuming larger values for those packings that had a higher fines contents. While kLa increases with temperature, the solubility of oxygen decreases simultaneously, resulting in net mass transfer rates being relatively unaffected by temperature in the range studied. This indicates that thermophile heap bioleach reactors are likely to operate under gas–liquid mass transfer limitations, especially at high altitude. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000075

Hydrometallurgical process development for the production of a zinc sulphate liquor suitable for electrowinning / D. Herrero in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 511–517 Titre : Hydrometallurgical process development for the production of a zinc sulphate liquor suitable for electrowinning Type de document : texte imprimé Auteurs : D. Herrero, Auteur ; P.L. Arias, Auteur ; B. Güemez, Auteur Année de publication : 2011 Article en page(s) : pp. 511–517 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Electrowinning  Hydrometallurgy  Leaching  Wasteprocessing Résumé : This study deals with the development of an innovative hydrometallurgical process for zinc recovery from Waelz Oxide, a concentrate of zinc and lead oxides obtained pyrometallurgically from the treatment of EAF dusts. Its main objective is the production of a zinc sulphate liquor to be used as feedstock in electrolytic processes. The process requires different stages to achieve this goal. The first stage consists of a double-sulphuric-acid-leaching, achieving a 88% lixiviation of the zinc present in the Waelz Oxide. After the leaching, to fulfil the strict requirements of an electrolysis feed, some purifying stages, such as oxidation, removing more than the 99% of the iron present in the leach liquor, and cementation to remove cadmium, lead and copper were investigated. Finally, if the concentration of some metallic impurity is above the accepted level for electrolytic processes, an additional purification stage could be considered. Through this process, sulphate zinc liquors with a zinc purity of around 99.75%, containing less than 135 ppm of metallic impurities, could be obtained. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000221 [article] Hydrometallurgical process development for the production of a zinc sulphate liquor suitable for electrowinning [texte imprimé] / D. Herrero, Auteur ; P.L. Arias, Auteur ; B. Güemez, Auteur . - 2011 . - pp. 511–517. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 511–517 Mots-clés : Electrowinning  Hydrometallurgy  Leaching  Wasteprocessing Résumé : This study deals with the development of an innovative hydrometallurgical process for zinc recovery from Waelz Oxide, a concentrate of zinc and lead oxides obtained pyrometallurgically from the treatment of EAF dusts. Its main objective is the production of a zinc sulphate liquor to be used as feedstock in electrolytic processes. The process requires different stages to achieve this goal. The first stage consists of a double-sulphuric-acid-leaching, achieving a 88% lixiviation of the zinc present in the Waelz Oxide. After the leaching, to fulfil the strict requirements of an electrolysis feed, some purifying stages, such as oxidation, removing more than the 99% of the iron present in the leach liquor, and cementation to remove cadmium, lead and copper were investigated. Finally, if the concentration of some metallic impurity is above the accepted level for electrolytic processes, an additional purification stage could be considered. Through this process, sulphate zinc liquors with a zinc purity of around 99.75%, containing less than 135 ppm of metallic impurities, could be obtained. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000221

Investigating heap bioleaching / Robert P. Van Hille in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 518–525 Titre : Investigating heap bioleaching : Effect of feed iron concentration on bioleaching performance Type de document : texte imprimé Auteurs : Robert P. Van Hille, Auteur ; Andries W. van Zyl, Auteur ; Nicholas R.L. Spurr, Auteur Année de publication : 2011 Article en page(s) : pp. 518–525 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Sulphide  ores  Hydrometallurgy  Bioleaching  Reaction  kinetics Résumé : This paper describes an investigation into the effect of iron concentration in the leach solution on the bioleaching of a low grade copper ore, where chalcopyrite was the dominant copper sulphide. The concentration of dissolved iron is primarily controlled by pH and the relative proportion of ferric to ferrous iron, with significant jarosite precipitation occurring above pH ≈ 1.8 in a highly oxidised system. The solution pH may be increased by the dissolution of acid soluble gangue and when iron oxidation is significantly higher than sulphur oxidation. The study was approached using two experimental systems. In the former, the leach solution was recycled through an ore bed of low aspect (reactor height divided by diameter) ratio for a portion of the experiment. During the recycle phase, no acid was added to the system and acid consumption by gangue material led to a pH increase (1.6–2.2). The resulting jarosite precipitation reduced soluble iron from 2.5 g/l to less than 250 mg/l. Copper recovery decreased, but not in proportion to the decrease in iron. This was partly attributed to adsorption on, or entrainment within, the jarosites. To study the effect of reduced iron concentration on leach performance under more controlled conditions, bioleaching was performed in packed bed column reactors with feed iron concentrations ranging from 5 g/l to 200 mg/l. Observations indicated an initial decreased rate of copper liberation with reduced iron concentration in the feed. The relationship between available Fe3+ concentration and copper liberation was not proportional. However, with time, the liberation of copper became independent of iron concentration in the percolation liquor. Further, the specific rate of copper liberation was consistently below the theoretical value on a basis of ferric iron concentration. The highest values of copper liberation were reported at the lowest iron concentrations. In summary, while increased iron concentration in solution may enhance the initial rate of leaching, mineral availability appears to dominate CuFeS2 leach kinetics through the majority of the leach. Furthermore, high iron concentrations in solution aggravate jarosite formation with concomitant retention of copper in the ore bed. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000233 [article] Investigating heap bioleaching : Effect of feed iron concentration on bioleaching performance [texte imprimé] / Robert P. Van Hille, Auteur ; Andries W. van Zyl, Auteur ; Nicholas R.L. Spurr, Auteur . - 2011 . - pp. 518–525. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 518–525 Mots-clés : Sulphide  ores  Hydrometallurgy  Bioleaching  Reaction  kinetics Résumé : This paper describes an investigation into the effect of iron concentration in the leach solution on the bioleaching of a low grade copper ore, where chalcopyrite was the dominant copper sulphide. The concentration of dissolved iron is primarily controlled by pH and the relative proportion of ferric to ferrous iron, with significant jarosite precipitation occurring above pH ≈ 1.8 in a highly oxidised system. The solution pH may be increased by the dissolution of acid soluble gangue and when iron oxidation is significantly higher than sulphur oxidation. The study was approached using two experimental systems. In the former, the leach solution was recycled through an ore bed of low aspect (reactor height divided by diameter) ratio for a portion of the experiment. During the recycle phase, no acid was added to the system and acid consumption by gangue material led to a pH increase (1.6–2.2). The resulting jarosite precipitation reduced soluble iron from 2.5 g/l to less than 250 mg/l. Copper recovery decreased, but not in proportion to the decrease in iron. This was partly attributed to adsorption on, or entrainment within, the jarosites. To study the effect of reduced iron concentration on leach performance under more controlled conditions, bioleaching was performed in packed bed column reactors with feed iron concentrations ranging from 5 g/l to 200 mg/l. Observations indicated an initial decreased rate of copper liberation with reduced iron concentration in the feed. The relationship between available Fe3+ concentration and copper liberation was not proportional. However, with time, the liberation of copper became independent of iron concentration in the percolation liquor. Further, the specific rate of copper liberation was consistently below the theoretical value on a basis of ferric iron concentration. The highest values of copper liberation were reported at the lowest iron concentrations. In summary, while increased iron concentration in solution may enhance the initial rate of leaching, mineral availability appears to dominate CuFeS2 leach kinetics through the majority of the leach. Furthermore, high iron concentrations in solution aggravate jarosite formation with concomitant retention of copper in the ore bed. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000233

Removal of uranium(VI) under aerobic and anaerobic conditions using an indigenous mine consortium / Simphiwe Chabalala in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 526–531 Titre : Removal of uranium(VI) under aerobic and anaerobic conditions using an indigenous mine consortium Type de document : texte imprimé Auteurs : Simphiwe Chabalala, Auteur ; Evans M. N. Chirwa, Auteur Année de publication : 2011 Article en page(s) : pp. 526–531 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Uranium(VI)  reduction  Biosorption  Indigenous  culture  High-level  waste  bioremediation Résumé : Biological uranium removal was investigated using bacteria sourced from an uranium mine in Limpopo, South Africa. Background uranium concentration in the soil from the mine was determined to be 168 mg/kg using the ICP-OES calibrated against the uranium atomic absorption standard solution. Thus the bacteria isolated from the site were expected to be resistant to uranium-6 [U(VI)] toxicity. Preliminary studies using mixed cultures suggest that uranium reduction occurs under anaerobic conditions in most cases. U(VI) reduction by obligate aerobes isolated from the soil consortium was poor. The pure cultures namely; Pseudomonas sp., Pantoea sp. and Enterobacter sp. showed a high reduction rate at pH 5–6. The initial U(VI) reduction rate determined at 50% of added U(VI) was highest in the Pseudomonas sp. at 30 mg/L. Enterobacter sp. outperformed the other two species at 200 mg/L and 400 mg/L with a rate of 63 and 198 mg/L/h, respectively. Rapid reduction was observed in all cultures during the first 4–6 h of incubation with equilibrium conditions obtained only after incubation for 24 h. The results demonstrate the potential of microbial U(VI) reduction as an alternative technology to currently used physical/chemical processes for treatment and recovery of uranium in the nuclear industry. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000245 [article] Removal of uranium(VI) under aerobic and anaerobic conditions using an indigenous mine consortium [texte imprimé] / Simphiwe Chabalala, Auteur ; Evans M. N. Chirwa, Auteur . - 2011 . - pp. 526–531. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 526–531 Mots-clés : Uranium(VI)  reduction  Biosorption  Indigenous  culture  High-level  waste  bioremediation Résumé : Biological uranium removal was investigated using bacteria sourced from an uranium mine in Limpopo, South Africa. Background uranium concentration in the soil from the mine was determined to be 168 mg/kg using the ICP-OES calibrated against the uranium atomic absorption standard solution. Thus the bacteria isolated from the site were expected to be resistant to uranium-6 [U(VI)] toxicity. Preliminary studies using mixed cultures suggest that uranium reduction occurs under anaerobic conditions in most cases. U(VI) reduction by obligate aerobes isolated from the soil consortium was poor. The pure cultures namely; Pseudomonas sp., Pantoea sp. and Enterobacter sp. showed a high reduction rate at pH 5–6. The initial U(VI) reduction rate determined at 50% of added U(VI) was highest in the Pseudomonas sp. at 30 mg/L. Enterobacter sp. outperformed the other two species at 200 mg/L and 400 mg/L with a rate of 63 and 198 mg/L/h, respectively. Rapid reduction was observed in all cultures during the first 4–6 h of incubation with equilibrium conditions obtained only after incubation for 24 h. The results demonstrate the potential of microbial U(VI) reduction as an alternative technology to currently used physical/chemical processes for treatment and recovery of uranium in the nuclear industry. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000245

Visualization of initial attachment of bioleaching bacteria using combined atomic force and epifluorescence microscopy / B. Florian in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 532–535 Titre : Visualization of initial attachment of bioleaching bacteria using combined atomic force and epifluorescence microscopy Type de document : texte imprimé Auteurs : B. Florian, Auteur ; N. Noël, Auteur ; W. Sand, Auteur Année de publication : 2011 Article en page(s) : pp. 532–535 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Bioleaching  Bacteria  Acid  rock  drainage Résumé : Bioleaching is the dissolution of metal sulfides, such as pyrite and chalcopyrite, by bacterial oxidation processes. It has been found that attachment of leaching bacteria to the mineral surface enhances the metal sulfide dissolution. The interaction of mixed cultures with respect to initial attachment processes has not been investigated. Therefore in this study we quantified and visualized initial colonization on pyrite by pure and mixed cultures. Strains of the genera Acidithiobacillus and Leptospirillum were tested. Sessile and planktonic cells were visualized by fluorescence microscopy using DAPI, FISH, Syto™ 9, lectin- and calcofluor-staining. Additionally, atomic force microscopy (AFM) was used for the investigations on cell morphology, spatial arrangement of cells on pyrite and mineral surface topography. The morphology of planktonic and sessile cells is different. Moreover, planktonic cells show differences in morphology due to the use of different substrata. By using different visualization methods it could be proven that colonization and biofilm formation on pyrite in mixed cultures is mostly dominated by Leptospirillum spp. Interactions of different species resulted in increased production of extracellular polymeric substances (EPS) or caused bacteria showing little tendency to attach when in monoculture to be incorporated into a biofilm by those that attach preferentially. Consequently, biofilm formation and metabolic diversity were furthered. One of the most important results is the finding that not all bioleaching bacteria are involved to the same extent in biofilm formation. Thus, further work shall allow us elucidate the important bacteria for biotechnological use, thereby leaching processes can be faster, more efficient and costs can be reduced. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000385 [article] Visualization of initial attachment of bioleaching bacteria using combined atomic force and epifluorescence microscopy [texte imprimé] / B. Florian, Auteur ; N. Noël, Auteur ; W. Sand, Auteur . - 2011 . - pp. 532–535. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 532–535 Mots-clés : Bioleaching  Bacteria  Acid  rock  drainage Résumé : Bioleaching is the dissolution of metal sulfides, such as pyrite and chalcopyrite, by bacterial oxidation processes. It has been found that attachment of leaching bacteria to the mineral surface enhances the metal sulfide dissolution. The interaction of mixed cultures with respect to initial attachment processes has not been investigated. Therefore in this study we quantified and visualized initial colonization on pyrite by pure and mixed cultures. Strains of the genera Acidithiobacillus and Leptospirillum were tested. Sessile and planktonic cells were visualized by fluorescence microscopy using DAPI, FISH, Syto™ 9, lectin- and calcofluor-staining. Additionally, atomic force microscopy (AFM) was used for the investigations on cell morphology, spatial arrangement of cells on pyrite and mineral surface topography. The morphology of planktonic and sessile cells is different. Moreover, planktonic cells show differences in morphology due to the use of different substrata. By using different visualization methods it could be proven that colonization and biofilm formation on pyrite in mixed cultures is mostly dominated by Leptospirillum spp. Interactions of different species resulted in increased production of extracellular polymeric substances (EPS) or caused bacteria showing little tendency to attach when in monoculture to be incorporated into a biofilm by those that attach preferentially. Consequently, biofilm formation and metabolic diversity were furthered. One of the most important results is the finding that not all bioleaching bacteria are involved to the same extent in biofilm formation. Thus, further work shall allow us elucidate the important bacteria for biotechnological use, thereby leaching processes can be faster, more efficient and costs can be reduced. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000385

Purification of rare earth elements from monazite sulphuric acid leach liquor and the production of high-purity ceric oxide / Renata D. Abreu in Minerals engineering, Vol. 23 N° 6 (Mai 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 536–540 Titre : Purification of rare earth elements from monazite sulphuric acid leach liquor and the production of high-purity ceric oxide Type de document : texte imprimé Auteurs : Renata D. Abreu, Auteur ; Carlos A. Morais, Auteur Année de publication : 2011 Article en page(s) : pp. 536–540 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Cerium  Rare  earth  metals  Cerium  oxidation  Process  optimization Résumé : The present work describes the development of an efficient and relatively simple process to obtain high grade CeO2 from sulphuric acid leach liquor. The liquor was obtained through acid digestion of monazite. The steps investigated in the process for obtaining ceric oxide were: (i) purification of the RE elements through their precipitation as rare earth and sodium double sulphate (NaRE(SO4)2·xH2O), (ii) NaRE(SO4)2·xH2O conversion into RE-hydroxide (RE(OH)3) through metathetic reaction and (iii) recovery of cerium and (iv) purification of cerium from the mixture of ceric hydroxide and manganese dioxide precipitate through dissolution of the solid with HCl and precipitation of the cerium through the addition of oxalic acid (H2C2O4) or ammonium hydroxide (NH4OH) solution. The X-ray diffraction spectra of the double sulphate obtained indicated the presence of monohydrated double sulphate. X-ray diffraction and chemical analysis indicated that the precipitation should be carried out at 70 °C and at 1.1 times the stoichiometric ratio of NaOH. An excess of 30% of KMnO4 was necessary to separate cerium from the other RE elements. Both oxalic acid and ammonium hydroxide proved efficient in the precipitation of cerium from the mixture of Ce/Mn obtained in the cerium separation. Following purification, calcinated products were obtained, assaying between 99% and 99.5% CeO2. The cerium recovery yield was greater than 98%. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268751000066X [article] Purification of rare earth elements from monazite sulphuric acid leach liquor and the production of high-purity ceric oxide [texte imprimé] / Renata D. Abreu, Auteur ; Carlos A. Morais, Auteur . - 2011 . - pp. 536–540. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 6 (Mai 2010) . - pp. 536–540 Mots-clés : Cerium  Rare  earth  metals  Cerium  oxidation  Process  optimization Résumé : The present work describes the development of an efficient and relatively simple process to obtain high grade CeO2 from sulphuric acid leach liquor. The liquor was obtained through acid digestion of monazite. The steps investigated in the process for obtaining ceric oxide were: (i) purification of the RE elements through their precipitation as rare earth and sodium double sulphate (NaRE(SO4)2·xH2O), (ii) NaRE(SO4)2·xH2O conversion into RE-hydroxide (RE(OH)3) through metathetic reaction and (iii) recovery of cerium and (iv) purification of cerium from the mixture of ceric hydroxide and manganese dioxide precipitate through dissolution of the solid with HCl and precipitation of the cerium through the addition of oxalic acid (H2C2O4) or ammonium hydroxide (NH4OH) solution. The X-ray diffraction spectra of the double sulphate obtained indicated the presence of monohydrated double sulphate. X-ray diffraction and chemical analysis indicated that the precipitation should be carried out at 70 °C and at 1.1 times the stoichiometric ratio of NaOH. An excess of 30% of KMnO4 was necessary to separate cerium from the other RE elements. Both oxalic acid and ammonium hydroxide proved efficient in the precipitation of cerium from the mixture of Ce/Mn obtained in the cerium separation. Following purification, calcinated products were obtained, assaying between 99% and 99.5% CeO2. The cerium recovery yield was greater than 98%. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268751000066X

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