| 1. |
- Javadi, Alireza, et al.
(författare)
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Formation of hydrogen peroxide by chalcopyrite and its influence on flotation
- 2013
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Ingår i: Minerals & metallurgical processing. - 0747-9182. ; 30:4, s. 212-219
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Tidskriftsartikel (refereegranskat)abstract
- Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by chalcopyrite (CuFeS2), which is a copper iron sulfide mineral, during grinding, was investigated. It was observed that chalcopyrite generated H2O2 in pulp liquid during wet grinding and also the solids when placed in water immediately after dry grinding. The generation of H2O2 in either wet or dry grinding was thought to be due to a reaction between chalcopyrite and water where the mineral surface is catalytically active in producing •OH free radicals by breaking down the water molecule. Effect of pH in grinding medium or water pH in which solids are added immediately after dry grinding showed lower the pH value more was the H2O2 generation. When chalcopyrite and pyrite are mixed in different proportions, the formation of H2O2 was seen to increase with increasing pyrite fraction in the mixed composition. The results of H2O2 formation in pulp liquid of chalcopyrite and together with pyrite at different experimental conditions have been explained by Eh-pH diagrams of these minerals. This study highlights the necessity of revisiting the electrochemical and/or galvanic interaction mechanisms between the chalcopyrite and pyrite in terms of their flotation behaviour.
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| 2. |
- Javadi, Alireza, et al.
(författare)
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Formation of hydrogen peroxide by sphalerite
- 2013
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Ingår i: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 125, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by sphalerite ((Zn, Fe) S) was examined during its grinding process. It was observed that sphalerite generated H2O2 in pulp liquid during wet grinding and also when the freshly ground solids placed in water immediately after dry grinding. The generation of H2O2 in either wet or dry grinding was thought to be due to a reaction between sphalerite and water where the mineral surface is catalytically active to produce OH• free radicals by breaking down the water molecule. Effect of pH on the formation of H2O2 by sphalerite was shown that the acidic pH generated more H2O2. Mixtures of pyrite, chalcopyrite and galena with sphalerite on the formation of H2O2 were also probed. It was shown that the concentration of H2O2 increases with increasing pyrite or chalcopyrite fraction in pyrite–sphalerite, chalcopyrite–sphalerite mixtures but with an increase in galena proportion, the concentration of H2O2 decreased in galena–sphalerite mixture. The oxidation or dissolution of one mineral than the other in a mixture can be explained better with the extent of H2O2 formation in the pulp liquid than galvanic interactions. It is clear of the greater role of H2O2 in the oxidation of sulphides or aiding the extensively reported galvanic interactions since the amount of H2O2 generated with a specific mineral followed the rest potential series. This study highlights the necessity of further investigations into the role of H2O2 in electrochemical and/or galvanic interaction mechanisms between pyrite, chalcopyrite and galena with sphalerite.
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| 3. |
- Javadi, Alireza, et al.
(författare)
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Sulphide mineral flotation : a new insight into oxidation mechanisms
- 2013
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Ingår i: XIII International Seminar on Mineral Processing Technology. - Madras : Indian Institute of Technology Madras. - 9788192855202 ; , s. 169-182
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Konferensbidrag (refereegranskat)abstract
- The formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by sulphide minerals during grinding was investigated. It was found that pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite (ZnS), and galena (PbS), which are the most abundant sulphide minerals on Earth, generated H2O2 in pulp liquid during wet grinding in the presence and absence of dissolved oxygen in water and also when the freshly ground solids were placed in water immediately after dry grinding. Pyrite generated more H2O2 than the other sulphide minerals and the order of H2O2 production by the minerals was found to be pyrite > chalcopyrite >sphalerite> galena. The pH of water influenced the extent of hydrogen peroxide formation where higher amounts of H2O2 were produced at highly acidic pH. The amount of H2O2 formed also increased with increasing sulphide mineral loading and grinding time due to increased surface area and its interaction with water.The sulphide surfaces are highly catalytically active due to surface defect sites and unsaturation because of broken bonds and capable of breaking down the water molecule leading to hydroxyl free radicals. The type of grinding medium on formation of hydrogen peroxide by pyrite revealed that the mild steel produced more H2O2 than stainless steel grinding medium, where Fe2+ and/or Fe3+ ions played a key role in producing higher amounts of H2O2.Furthermore, the effect of mixed sulphide minerals, i.e., pyrite–chalcopyrite, pyrite–galena, chalcopyrite–galena and sphalerite–pyrite, sphalerite–chalcopyrite and sphalerite–galena on the formation of H2O2 showed increasing H2O2 formation with increasing pyrite fraction in chalcopyrite–pyrite composition. In pyrite–sphalerite, chalcopyrite–sphalerite or galena– sphalerite mixed compositions, with the increase in pyrite or chalcopyrite proportion, the concentration of H2O2 increased but with increase in galena proportion, the concentration of H2O2 decreased. By increasing the pyrite proportion in pyrite–galena mixture, the concentration of H2O2 increased. Similarly, in the mixture of chalcopyrite–galena, the concentration of H2O2 increased with increasing chalcopyrite fraction. The results of H2O2formation in pulp liquid of individual sulphide minerals and in combination at different experimental conditions have been explained by Eh–pH diagrams of these minerals and the existence of free metal ions that are equally responsible for H2O2 formation besides the catalytic activity of surfaces. The results of the amount of H2O2 production also corroborate with the rest potential of the sulphide minerals; higher the rest potential more is the formation of H2O2. Most likely H2O2 is responsible for the oxidation of sulphide minerals and dissolution of non-ferrous metal sulphides in the presence of ferrous sulphide besides the galvanic interactions.This study highlights the necessity of revisiting the electrochemical and/or galvanic interactions between the grinding medium and sulphide minerals, and interaction mechanisms between pyrite and other sulphide minerals in terms of their flotation behaviour in the context of the inevitable existence of H2O2 in the pulp liquid.
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| 4. |
- Javadi Nooshabadi, Alireza, et al.
(författare)
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Formation of hydrogen peroxide by pyrite and its influence on flotation
- 2013
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 49, s. 128-134
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Tidskriftsartikel (refereegranskat)abstract
- Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by pyrite (FeS2), the most abundant metal sulphide on Earth, during grinding was investigated. It was found that pyrite generated H2O2 in pulp liquid during wet grinding and also the solids when placed in water immediately after dry grinding. Type of grinding medium on formation of hydrogen peroxide revealed that the mild steel produced more H2O2 than stainless steel grinding medium, where Fe2+ and/or Fe3+ ions played a key role in producing higher amounts of H2O2. The effect of grinding atmosphere of air and N2 gas showed that nitrogen environment free from oxygen generated more H2O2 than air atmosphere suggesting that the oxygen in hydrogen peroxide is derived from water molecules. In addition, the solids after dry grinding producing more H2O2 than wet grinding indicate the role of pyrite surface or its catalytic activity in producing H2O2 from water. This study highlights the necessity of relooking into the electrochemical and/or galvanic interaction mechanisms between the grinding medium and pyrite in terms of its flotation behaviour.
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| 5. |
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| 6. |
- Kota, Hanumantha Rao, et al.
(författare)
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Revisiting sulphide mineral (bio) processing : a few priorities and directions
- 2013
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Ingår i: XV Balkan Mineral Processing Congress, 12-16 June 2013, Sozopol, Bulgaria.
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Konferensbidrag (refereegranskat)abstract
- Large efforts are being made to streamline the conventional (chemical and physical) technological schemes of ore processing, remediation and environmental protection towards reducing overall costs, limiting the use of dangerous substances, decreasing waste streams and improving waste disposal and recycling practice. Hitherto, search for such innovations has been performed mainly empirically and there is an urgent need to shift these technologies to be more innovative and effective. Alternative biotechnological solutions and solutions mimicking natural processes are also being proposed. However, except for bioleaching, practical exploitation of the biotechnological potential in extractive industries and accompanying environmental protection measures remains far from feasibility.Understanding of the fundamental concepts of aquatic chemistry of minerals–selective adsorption and selective redox reactions at mineral–bacteria–solution interfaces, impact innovating conventional and bio-flotation, as well as (bio)remediation/detoxification of mineral and chemical wastes. Molecular-level knowledge and coherent understanding of minerals contacted with aqueous solutions is required that underlie great opportunities in controlling abiotic and biotic mineral–solution interfaces towards the grand challenge of tomorrow’s science and mineral processing technology.
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| 7. |
- Kota, Hanumantha Rao, et al.
(författare)
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Revisiting Sulphide Mineral (Bio) Processing: A Few Priorities And Directions
- 2013
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Ingår i: Journal of Powder Metallurgy & Mining. - : OMICS Publishing Group. - 2168-9806. ; 2:4
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Tidskriftsartikel (refereegranskat)abstract
- Large efforts are being made to streamline the conventional (chemical and physical) technological schemes of ore processing, remediation and environmental protection towards reducing overall costs, limiting the use of dangerous substances, decreasing waste streams and improving waste disposal and recycling practice. Hitherto, search for such innovations has been performed mainly empirically and there is an urgent need to shift these technologies to be more innovative and effective. Alternative biotechnological solutions and solutions mimicking natural processes are also being proposed. However, except for bioleaching, practical exploitation of the biotechnological potential in extractive industries and accompanying environmental protection measures remains far from feasibility. Understanding of the fundamental concepts of aquatic chemistry of minerals–selective adsorption and selective redox reactions at mineral– bacteria–solution interfaces, impact innovating conventional and bio-flotation, as well as (bio) remediation/detoxification of mineral and chemical wastes are necessary. Molecular-level knowledge and coherent understanding of minerals contacted with aqueous solutions is required that underlie great opportunities in controlling abiotic and biotic mineral– solution interfaces towards the grand challenge of tomorrow’s science and mineral processing technology
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