KINETICS OF LEACHING OF COVELLITE IN FERRIC-SULFATE-SULFURIC ACID MEDIA by Carlos Angeles B.Eng., Universidad Nacional Mayor de San Marcos, 2011 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Materials Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) August 2015 © Carlos Angeles, 2015 Abstract Hydrometallurgy methods to extract copper are becoming more frequently applied in modern industry. However, the leaching kinetics for certain minerals like covellite is poorly understood. This thesis investigates the kinetics of covellite leaching in a ferric-sulfate-sulfuric acid media, with an emphasis first placed on the understanding of the effect of the most common variables such as temperature and redox potential. A natural mineral sample of covellite and an ore sample from the Oyu Tolgoi project in Mongolia were obtained for the leaching studies. The leaching temperature was varied from 20° to 90°C, the total iron concentration varied from 0.1 mol/L to 0.5 mol/L, the Fe+3/Fe+2 ratios varied from 0.1 to 10. The leaching results showed that an increase in temperature will result in an increase in the rate and extent of copper extraction. However, the redox potential or Fe+3/Fe+2 ratio have little to no effect on the final copper extraction. These factors had only a modest impact on copper leach kinetics. The final copper extractions for covellite from Butte, Montana and covellite containing ore from Oyu Tolgoi at the same temperature were very similar. The key factor to improve copper extraction from covellite containing ores is to maximize the leach temperature. The other factors appear to be much less important. These findings provide the basis for process design and optimization of industrial leaching processes of covellite. ii Preface Financial support for this work was provided by Rio Tinto. I was responsible for conducting the research, preparing and analyzing the results, and writing progress reports and this thesis. The work was done under the supervision of Dr. David Dreisinger. iii Table of Contents Abstract .......................................................................................................................................... ii Preface ........................................................................................................................................... iii Table of Contents ......................................................................................................................... iv List of Tables ............................................................................................................................... vii List of Figures ............................................................................................................................. viii List of Abbreviations .................................................................................................................. xii Acknowledgements .................................................................................................................... xiii Dedication ................................................................................................................................... xiv Chapter 1: Introduction ................................................................................................................1 1.1 Scope of Present Study and Research Objectives ........................................................... 2 Chapter 2: Literature Review .......................................................................................................3 2.1 General Copper Information ........................................................................................... 3 2.2 Copper Price.................................................................................................................... 7 2.3 Covellite ........................................................................................................................ 10 2.3.1 Research on Covellite Leaching ............................................................................... 11 2.3.2 Covellite Leaching .................................................................................................... 15 2.3.3 Covellite Industrial Leaching Operations ................................................................. 19 2.4 Summary of Literature Review ..................................................................................... 21 Chapter 3: Objectives ..................................................................................................................22 Chapter 4: Experimental Procedures ........................................................................................23 4.1 Materials ....................................................................................................................... 23 iv 4.2 Experimental Conditions .............................................................................................. 23 4.2.1 Temperature .............................................................................................................. 23 4.2.2 Ferric/Ferrous Concentration .................................................................................... 24 4.2.3 Potential .................................................................................................................... 24 4.2.4 Sulfuric Acid Concentration – pH Control ............................................................... 24 4.2.5 Particle Size .............................................................................................................. 25 4.2.6 Stirring Speed and Effect on Mixing ........................................................................ 25 4.3 Samples Preparation...................................................................................................... 25 4.4 Chemical Analysis of the Mineral Sample ................................................................... 27 4.5 Mineralogical Characterization of the Sample ............................................................. 29 4.5.1 Acid Soluble Copper ................................................................................................. 31 4.6 Equipment and Experimental Set-up ............................................................................ 31 4.6.1 Permanganate use as Oxidant ................................................................................... 34 4.7 Leaching Procedure ...................................................................................................... 35 4.8 Sampling Program ........................................................................................................ 35 4.9 Sampling Analysis ........................................................................................................ 36 4.9.1 Liquid Sample Analysis ............................................................................................ 36 4.10 Sample and Waste Management ................................................................................... 37 Chapter 5: Results and Discussion .............................................................................................38 5.1 Mineralogical Characterization ..................................................................................... 38 5.2 Experimental Work Conditions .................................................................................... 41 5.3 Results of the Chemical Leaching Experiments for Covellite from Butte Montana .... 42 5.3.1 Effect of Temperature Control – Only Ferric in Solution ......................................... 42 v 5.3.2 Mathematical Model for the Butte, Montana sample based on temperature effect .. 45 5.3.3 Effect of Ferric/Ferrous Ratio ................................................................................... 47 5.3.4 Effect of Ferric/Ferrous Ratio at 40ºC using Permanganate ..................................... 51 5.3.5 Effect of Ferric/Ferrous Ratio at 50ºC using Permanganate ..................................... 55 5.3.6 Effect of Ferric/Ferrous Ratio at 60ºC using Permanganate ..................................... 58 5.3.7 Effect of Ferric/Ferrous Ratio at 70ºC using Permanganate ..................................... 60 5.3.8 Effect of Ferric/Ferrous Ratio at 80ºC using Permanganate ..................................... 63 5.3.9 Effect of Ferric/Ferrous Ratio at 90ºC using Permanganate ..................................... 65 5.4 Results of the Chemical Leaching Experiments: Oyu Tolgoi Covellite ....................... 68 Chapter 6: Conclusions and Recommendations .......................................................................71 6.1 Conclusions ................................................................................................................... 71 6.2 Industrial Applications .................................................................................................. 73 6.3 Recommendations for Future Work.............................................................................. 73 Bibliography .................................................................................................................................74 vi List of Tables Table 2.1 Principal Commercial Copper Minerals [2].................................................................... 7 Table 2.2 Leaching Kinetics observed for Covellite dissolution