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Master's Thesis 2008:076 MASTER'S THESIS Selective Removal of Impurity Elements from Maurliden Västra Complex Sulphides Flotation Concentrate Awe Samuel Ayowole Luleå University of Technology Master Thesis, Continuation Courses Minerals and Metallurgical Engineering Department of Chemical Engineering and Geosciences Division of Process Metallurgy 2008:076 - ISSN: 1653-0187 - ISRN: LTU-PB-EX--08/076--SE ACKNOWLEDGEMENT First and foremost my profound gratitude goes to my Creator, The Everlasting King of Glory, Who has given me the privilege to be alive and pass through the rigorous academic programme successfully. Secondly, I would like to express my deepest appreciation to my supervisor, Professor Åke Sandström. His guidance, incisive advice and support throughout this work were of the utmost importance. I wish to say a special thank you to Birgtta Nyberg for her relentless efforts to analyse my samples whenever I contacted her. Also, the chemical analysis of the samples done by Jan-Eric Sundkvist and Joachim Pettersson, both from Boliden Minerals AB, is highly appreciated. Further thanks to all the employees at the Division of Process Metallurgy, Luleå University of Technology, in particular, Chandra Sekhar Gahan, Fredrik Engström and Ryan Robinson, for their untiring efforts to analyze my samples. Besides, I give many thanks to all my friends who have contributed in one way or the other to my success. I say thank a million times. Moreover, I will be ingrate, if the financial assistance offered me by the Swedish Institute (SI) is not acknowledged, without this financial reinforcement, my dream of undertaking this program at this citadel of learning, LTU, would have been a mirage. I say, SI, forward ever and backward never. More power to your elbow. Also, my profound appreciation goes to VINNOVA “STRATEGISKT GRUVFORSKNINGSPROGRAM”, Boliden Minerals AB, LKAB and Lundin Mining for their financial supports during the course of undertaking this project. I say many thanks to you all. Finally, my heart-felt appreciations go to my loving wife, Patricia, and my blessed sons, Stephen and Emmanuel, for their understanding and perseverance. I love you all. Samuel Ayowole Awe September 2008, Luleå, Sweden 2 TABLE OF CONTENT ACKNOWLEDGEMENT ......................................................................................................... 2 TABLE OF CONTENT ............................................................................................................. 3 ABSTRACT............................................................................................................................... 4 1.0 INTRODUCTION................................................................................................................ 5 1.1 Background ...................................................................................................................... 5 1.2 The Aim of this Work ...................................................................................................... 8 1.3 The Scope of the Study .................................................................................................... 8 2.0 LITERATURE REVIEW..................................................................................................... 9 2.1 Mineralization of Boliden Operation Areas..................................................................... 9 2.2 Copper: Sources and Applications ................................................................................. 10 2.3 Arsenic: Properties and its problems.............................................................................. 12 2.4 Antimony: Properties and Dissolution Chemistry ......................................................... 13 2.5 Complex Copper Sulphide Concentrates: Processing and Impurity Removal Techniques .............................................................................................................................................. 15 2.6 Recovery of Antimony from the Leach Liquor.............................................................. 17 3.0 MATERIALS AND METHODS....................................................................................... 19 3.1 Materials......................................................................................................................... 19 3.2 Methods.......................................................................................................................... 19 3.2.1 Particle Size Analysis.............................................................................................. 19 3.2.2 Mineralogical Investigations................................................................................... 20 3.2.3 Chemical Leaching Experiment.............................................................................. 20 4.0 RESULTS AND DISCUSSION ........................................................................................ 22 4.1 Particle Size Distribution ............................................................................................... 22 4.2 Mineralogical Composition of the Concentrates............................................................ 23 4.3 Alkaline Sodium Hypochlorite Leaching....................................................................... 25 4.4 Acidic Cupric Chloride Leaching .................................................................................. 27 4.5 Alkaline Sulphide Leaching........................................................................................... 28 4.5.1 Influence of sulphide ion concentration on metal recovery .................................... 29 4.5.2 Effect of solids concentration on metal recovery.................................................... 32 4.5.3 Influence of temperature on recovery of antimony and arsenic.............................. 33 4.5.4 Leaching kinetics of antimony from the concentrate.............................................. 34 5.0 CONCLUSIONS AND RECOMMENDATIONS............................................................. 35 5.1 Conclusions .................................................................................................................... 35 5.2 Recommendations .......................................................................................................... 36 REFERENCES......................................................................................................................... 37 APPENDICES.......................................................................................................................... 40 3 ABSTRACT Impurity removal is one of the major problems encountered in copper metallurgy today because relatively pure copper ores reserves are becoming exhausted, and the resources of unexploited ores often contain relatively high amounts of several impurity elements like antimony, arsenic, mercury and bismuth, which need to be eliminated. The present work is concerned to pre-treat an antimony-arsenic-bearing copper concentrate by selective dissolution of the impurities, therefore, upgrading the concentrate for pyro-processing. To accomplish this, selective dissolution of antimony and arsenic from a tetrahedrite-containing copper concentrate by alkaline hypochlorite, acidic cupric chloride and alkaline sulphide leach solutions were investigated. Alkaline hypochlorite solution shows high degree of selectivity in solubilising antimony and arsenic but low recoveries while the acidic cupric chloride solution is highly selective to zinc and lead with insignificant recovery of antimony and arsenic. However, alkaline sulphide solution proves to be greatly selective to dissolve the impurity elements from the concentrate with high yields of the elements into the leach liquor. Moreover, further studies on alkaline sulphide solution leaching efficiency were conducted in order to ascertain the optimum conditions for antimony and arsenic recovery. The investigated parameters were sulphide ions concentration, solids concentration, leaching temperature and leaching kinetics. 4 1.0 INTRODUCTION 1.1 Background Mining has been a part of everyday life in Sweden for at least a thousand years. There is archaeological evidence of mining in the 7th century at what is known as the Falun copper mine, which was operated continuously for more than a millennium. A joint stock company was formed in 1288, probably the oldest in the world, to run the Falun copper mine until its closure in 1993. The mine is now a UNESCO World Heritage site [1]. Sweden is one of the leading ore and metal-producing countries in the European Union (EU). Mining and metal production are still important Swedish industries today. Sweden has a very rich mining history which has been relevant to the economic development of the country and it is by far the largest iron ore producer in the EU as well as the leading producers of base and precious metals. The total annual production of ores and metals in Sweden amounts to about 45 million tonnes, half of which is iron ore and the rest are gold, silver, copper, zinc and lead ore [2]. Sweden reported copper production of 305 000 tons of copper concentrate in 2003 compared to 263 000 tons produced in 2002. Most of Sweden’s polymetallic deposits are of the massive and disseminated sulphide types, with only one sediment hosted base metal deposit. Complex types of mineralization are common in Europe and in Sweden such complex mineral sulphides are found both in the Skellefteå field and in the mining area in Bergslagen [3]. Most of
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