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Redox Processes in Sulfide Minerals Dedic REDOX PROCESSES IN SULFIDE MINERALS by Devon John Renock A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Geology) in The University of Michigan 2010 Doctoral Committee: Associate Professor Udo Becker, Chair Professor Rodney C. Ewing Professor Kim Hayes Professor Stephen E. Kesler Assistant Professor Greg Dick DEDIC i For Bevin and Max and, of course, William H. ii ACKNOWLEDGMENTS Five years ago I decided to quit my job at a company in Ann Arbor and pursue my longtime dream of a graduate degree in geology. I would not have been able to take this step without the love and support of my wife, Bevin. Her patience and encouragement has meant everything to me these last few years. My son Max was born three weeks ago and he has been at my side for every late night writing session since (in between diapers, bottles, and burps, of course). He has been a source of inspiration and great joy, and we are so thankful that he has arrived in our lives. My parents and my family have always been there for me, and I am ever grateful for their love and support. In my years at Michigan, I am so fortunate to have been able to be mentored scientifically, professionally, and personally by my advisors, Udo Becker and Rod Ewing. It has been a privilege to study in their research group. They have provided me with incredible opportunities and given me a strong foundation from which to launch my own academic career. Most importantly, they have become good friends to me and my family. The rest of my thesis committee has also been very supportive of my work. I acknowledge Kim Hayes for encouraging me to develop collaboration with his research group in order to characterize mackinawite nanoparticles. I have had the opportunity to interact with Steve Kesler on the geology of noble metal incorporation in galena and pyrite and he has been a wealth of insightful ideas and comments. iii I am also grateful to Greg Dick for agreeing to join my committee in the final few months to review my manuscript. I am very appreciative of Tanya Gallegos from the Department of Civil and Environmental Engineering who provided numerous samples of mackinawite and many hours of good discussion that resulted in our Chemical Geology paper. My special thanks go to Dr. Satoshi Utsunomiya for the numerous Saturday mornings we spent on the transmission microscope together. He is one of the most talented scientists I have ever had the pleasure to work with. Haiping Sun and Kai Sun at the North Campus EMAL were also instrumental in helping me with my XPS analyses. Many other faculty and staff contributed to this work. My conversations and collaborations with Artur Deditius on arsenian pyrite contributed to many of the ideas that went into the galena work. I have to thank Martin Reich for helping to get me started on the calculations about coupled substitutions in sulfides. Lindsay Shuller has been a valuable resource regarding computational simulations, a confidante, a lunch buddy, and a great friend during my time here. Janine Taylor and Mike Messina helped with all of my computer and networking problems. Carl Henderson was a valuable resource for me in EMAL. Nancy Kingsbury and Anne Hudon were invaluable in all things nonscience. I should thank many of my colleagues in our research group for making my time here very rewarding. These include Elizabeth Ferriss, Frannie Skomurski, Chintalapalle Ramana, Darius Dixon, Subhashis Biswas, Qiaona Hu, Maik Lang, Jianwei Wang, Stephen Crabtree, Nadja Insel, Alex Janevski, and Jiaming Zhang. iv TABLE OF CONTENTS Dedication .......................................................................................................................... ii Acknowledgments ............................................................................................................ iii List of Figures ............................................................................................................. viii List of Tables................................................................................................................. xi Chapter 1 Introduction.................................................................................................... 1 References ...................................................................................................................... 9 Chapter 2 Chemical and structural characterization of As immobilization by nanoparticles of mackinawite (FeSm) ........................................................................ 14 Abstract ........................................................................................................................ 14 Introduction ................................................................................................................. 15 Methods ........................................................................................................................ 18 Mackinawite synthesis ............................................................................................. 18 Sample preparation ................................................................................................. 19 Transmission electron microscopy (TEM) ............................................................ 20 X-ray photoelectron spectroscopy (XPS) .............................................................. 21 Results and Discussion ................................................................................................ 24 TEM analysis............................................................................................................ 24 X-ray photoelectron spectroscopy (XPS) .............................................................. 31 Conclusions .................................................................................................................. 49 Acknowledgments........................................................................................................ 52 References .................................................................................................................... 53 Chapter 3 A first principles study of the oxidation energetics and kinetics of realgar .......................................................................................................................... 61 Abstract ........................................................................................................................ 61 Introduction ................................................................................................................. 63 v Theoretical methods .................................................................................................... 69 Computational methods and parameters .............................................................. 69 Calculation of adsorbate-adsorbate interactions .................................................. 70 Results and discussion ................................................................................................. 73 Energetics of adsorption and co-adsorption to As4S4 ........................................... 73 Kinetic study of molecular O2 adsorption to As4S4 .............................................. 97 Implications................................................................................................................ 108 Energetics ............................................................................................................... 108 Kinetics ................................................................................................................... 110 Conclusions ................................................................................................................ 117 Acknowledgments...................................................................................................... 118 References .................................................................................................................. 119 Chapter 4 A first principles study of coupled substitution in galena ...................... 129 Abstract ...................................................................................................................... 129 Introduction ............................................................................................................... 130 Computational Methods ........................................................................................... 134 First principles total-energy calculations ............................................................ 135 Calculation of cation-cation interaction parameters .......................................... 136 Monte-Carlo simulation: determination of thermodynamic properties .......... 139 Results ........................................................................................................................ 143 Determination of coupled substitution energies, ΔEsub ...................................... 143 Electronic structure ............................................................................................... 152 Enthalpy of mixing in galena ................................................................................ 155 Configurational entropy........................................................................................ 157 Gibbs free energy of mixing in galena ................................................................. 157 Discussion ..................................................................................................................
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