ACTINYL ION CRYSTAL CHEMISTRY AND ITS IMPACT ON STRUCTURAL TOPOLOGIES AND ENVIRONMENTAL FATE A Dissertation Submitted to the Graduate School of the University of Notre Dame in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Jessica M. Morrison Peter C. Burns, Director Graduate Program in Civil Engineering and Geological Sciences Notre Dame, Indiana April 2013 © Copyright 2013 Jessica M. Morrison ACTINYL ION CRYSTAL CHEMISTRY AND ITS IMPACT ON STRUCTURAL TOPOLOGIES AND ENVIRONMENTAL FATE Abstract by Jessica M. Morrison The modern study of the actinide elements began more than 70 years ago, yet much remains to be explored about how these radioactive elements behave in complicated systems like the soils at Department of Energy sites, the forests near Chernobyl or the ocean waters off Fukushima. The fundamental study of actinide chemistry provides a basis for understanding the mechanisms that control actinide migration in the environment. Here two major themes are presented in which one explores the structural properties of U(VI) uranyl germanates as they relate to U(VI) uranyl silicates and the emergence of cation-cation interactions as a structural feature, and the other offers a glimpse at the behavior of Np(V) and U(VI) during the growth of rock- forming minerals for the purpose of understanding the inorganic controls of crystal growth on environmental remediation. Hydrothermal synthesis and single crystal X-ray diffraction were employed in the study of U(VI) uranyl germanates. For the study of Np(V) incorporation into Jessica M. Morrison rock-forming minerals, a variety of room temperature syntheses were conducted before a simple synthesis in aqueous solution was devised. Characterization methods included ICP-MS in solid and solution modes and XPS. This research demonstrated (1) the structural differences between U(VI) uranyl germanates and silicates by introducing new (VI) uranyl germanate compounds with uncommon structural features, like cation-cation interactions and chains of GeO5 tetrahedra; and (2) the potential for structural incorporation to play a role in neptunium mobility in the subsurface by showing that calcite has a higher affinity for neptunium than gypsum during synthetic growth. To my grandmother, Daisy Rowe, who never learned to read; to my mother, Linda Dalton, the only one of fifteen siblings to complete high school; to my nieces, Madison and Annabella, who will inherit the moon; to my husband, Brandon, for everything else. ii CONTENTS FIGURES..................................................................................................................................................... vi TABLES ........................................................................................................................................................x PREFACE .................................................................................................................................................xiii ACKNOWLEDGMENTS ....................................................................................................................... xiv CHAPTER 1: INTRODUCTION ............................................................................................................ 1 1.1 History and Usage ............................................................................................................. 2 1.2 Rationale for Study ........................................................................................................... 3 1.3 Overview and Scope ......................................................................................................... 8 CHAPTER 2: RESEARCH DESIGN AND METHODS ...................................................................10 2.1 Inorganic Synthesis Methods .....................................................................................10 2.1.1 Hydrothermal Synthesis .............................................................................10 2.1.2 Ambient Synthesis ........................................................................................11 2.1.2.1 Evaporation .................................................................................. 11 2.1.2.2 Diffusion ......................................................................................... 13 2.2 Materials Characterization ..........................................................................................16 CHAPTER 3: STRUCTURAL OVERVIEW OF HEXAVALENT URANIUM GERMANATES AND SILICATES ..........................................................................................................................22 3.1 Introduction to the Crystal Chemistry of Hexavalent Uranium ....................22 3.2 Overview of Germanium and Silicon Occurrence, Coordination and Structures ....................................................................................................................25 3.3 Structural descriptions of uranyl germanates .....................................................27 3.3.1 Sheets containing isolated tetrahedra ..................................................27 3.3.2 Frameworks containing isolated tetrahedra ......................................27 3.3.3 Frameworks containing dimers of tetrahedra ...................................28 3.3.4 Frameworks containing chains of tetrahedra ....................................28 3.3.5 Frameworks containing rings of tetrahedra .......................................29 3.4 Structural descriptions of uranyl silicates.............................................................34 3.4.1 Sheets containing isolated tetrahedra: The uranophane-group minerals .........................................................................................................34 3.4.2 Sheets containing rings of tetrahedra ...................................................37 3.4.3 Frameworks containing isolated tetrahedra ......................................37 iii 3.4.4 Frameworks containing dimers of tetrahedra ...................................37 3.4.5 Frameworks containing chains of tetrahedra ....................................38 3.4.6 Frameworks containing rings of tetrahedra .......................................38 3.5 Discussion ..........................................................................................................................45 CHAPTER 4: SYNTHESES, STRUCTURES, AND CHARACTERIZATION OF AN OPEN- FRAMEWORK URANYL GERMANATE ...............................................................................48 4.1 Experimental Section .....................................................................................................49 4.2 Results .................................................................................................................................59 4.3 Discussion ..........................................................................................................................62 CHAPTER 5: U(VI) URANYL CATION-CATION INTERACTIONS IN FRAMEWORK GERMANATES .............................................................................................................................64 5.1 Experimental Section .....................................................................................................66 5.2 Results .................................................................................................................................83 5.3 Discussion ..........................................................................................................................87 CHAPTER 6: CONTROLLED NUCLEATION AND GROWTH OF CALCITE IN AN AQUEOUS SYSTEM ....................................................................................................................91 6.1 Synthesis Review .............................................................................................................92 6.1.1 Aqueous-Inorganic .......................................................................................92 6.1.2 Organic-Mediated Aqueous-Inorganic ..................................................92 6.1.3 Template/Seed Aqueous-Inorganic .......................................................93 6.1.4 Mechanical Modification.............................................................................94 6.2 Experimental Section .....................................................................................................94 6.3 Results and Discussion ..................................................................................................99 CHAPTER 7: INORGANIC CONTROLS ON NEPTUNIUM MOBILITY IN THE SUBSURFACE VIA CRYSTAL GROWTH .......................................................................... 105 7.1 Methods ........................................................................................................................... 110 7.2 Results .............................................................................................................................. 117 7.3 Discussion ....................................................................................................................... 123 CHAPTER 8: CONCLUSIONS AND FUTURE WORK ............................................................... 128 8.1 Importance of this research ..................................................................................... 128 8.2 Uranyl Germanates ...................................................................................................... 129 8.3 Neptunium Incorporation ........................................................................................