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Thermodynamic Study of Aqueous Rare Earth

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Thermodynamic Study of Aqueous Rare Earth THERMODYNAMICS OF AQUEOUS SOLUTIONS KRISTY M. ERICKSON B.Sc., University of Lethbridge, 2005 A Thesis Submitted to the School of Graduate Studies of the University of Lethbridge in Partial Fulfillment of the Requirements for the Degree [MASTER OF SCIENCE] Department of Chemistry and Biochemistry University of Lethbridge LETHBRIDGE, ALBERTA, CANADA © Kristy M. Erickson, 2007 A STUDY OF THE THERMODYNAMICS OF AQUEOUS RARE EARTH ELEMENT CONTAINING TRIFLATE SALT SYSTEMS KRISTY M. ERICKSON Approved: (Print Name) (Signature) (Rank) (Highest Date Degree) _________________ _______________________ ___________ ___________ _____ Supervisor _________________ _______________________ ___________ ___________ _____ Thesis Examination Committee Member _________________ _______________________ ___________ ___________ _____ Thesis Examination Committee Member _________________ _______________________ ___________ ___________ _____ External Examiner _________________ _______________________ ___________ ___________ _____ Chair, Thesis Examination Committee ii “Thermodynamics is not difficult if you can just keep track of what it is you are talking about.” -William F. Giauque, Nobel Laureate 1949 (as cited in Bent, 1972) iii ABSTRACT Relative densities and relative massic heat capacities have been measured for aqueous solutions of triflic acid (CF3SO3H), sodium triflate (NaCF3SO3), gadolinium triflate (Gd(CF3SO3)3), dysprosium triflate (Dy(CF3SO3)3), neodymium triflate (Nd(CF3SO3)3), erbium triflate (Er(CF3SO3)3), ytterbium triflate (Yb(CF3SO3)3), and yttrium triflate (Y(CF3SO3)3) at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa. The resulting densities and massic heat capacities have been used to calculate out apparent molar volume and apparent molar heat capacity data for each of the investigated aqueous systems. The concentration dependencies of the apparent molar volumes and apparent molar heat capacities have been modeled using Pitzer-ion interaction equations. Single ion volumes and heat capacities have been calculated using estimates of the apparent molar properties at infinite dilution obtained from the Pitzer-ion interaction equations. These single ion values have, where possible, been compared with those previously reported in the literature. Also, relative densities have been measured for aqueous solutions of CF3SO3H, Gd(CF3SO3)3, Nd(CF3SO3)3, and Yb(CF3SO3)3 at T = (323.15, 348.15, 373.15, and 423.15) K and p = (5.00, 10.00, and 15.00) MPa. The resulting densities have been used to calculate apparent molar volumes. The concentration dependences of these properties have also been modeled using Pitzer-ion interaction equations. The apparent molar volumes have been used to calculate single ion volumes which, in turn, have been compared with those previously reported in the literature. This thesis also attempts to model the temperature, pressure, and concentration dependencies of the reported apparent molar properties of each system investigated using iv an equation of state commonly referred to as the density model. Where possible, the results of this model have been compared with those results from models previously reported in the literature. v Acknowledgements I would first like to thank my parents, Neil and Wanda, and my brother, Jeremy, for all their love and support over the last 20 years of my education and their continuing support for my work in the future. I would also like to thank my friends Allison, Warren, Scott, Troy, Jennifer, and all the Chemistry and Biochemistry graduate students at the University of Lethbridge. Without their help and support, I never would have made it this far, and with so many wonderful memories. I am greatly indebted to my supervisor, Dr. Andrew Hakin, who allowed me to work in his lab as an undergraduate and subsequently as a graduate student. Without his guidance and support, I surely never would have accomplished all that I have in these past two years. I am also grateful for his trust in my abilities to represent his research at the International Conference on Chemical Thermodynamics (ICCT 2006) gathering in August, 2006. The experience was truly eye opening and it has been a pleasure working with Andy these last two years. I would like to thank my committee members, Dr. Marc Roussel and Dr. Kenneth Vos for their continuing support and assistance throughout my graduate degree. I would also like to thank Dr. Lee Wilson (University of Saskatchewan) for acting as my external examiner. Appreciation should also be given to Heinz Fischer and Frank Klassen, who helped me modify and reconstruct the high temperature and pressure vibrating tube densimeter that will be discussed in Chapters 3 and 5. They are life savers. Dr. Rene Boeré and Dr. John Vokey also deserve acknowledgements for their enlightening classes on lanthanide chemistry and statistical design. Furthermore, I would like to thank vi Dr. Peter Tremaine (University of Guelph) for his words of encouragement at the ICCT 2006 gathering and his interest in my future research. I am deeply grateful to the current and past members of the Hakin research group: Jin Lian Liu’s assistance with data collection, data analysis, and her continuing concern about my healthy eating got me through these past two years. Stephanie Jones’, Sharmeen Zahir’s, and Benjamin Ireland’s continuing assistance with data collection and analysis also helped me greatly. I am also grateful to Sharmeen and Stephanie for their continuous runs to the Dairy Queen for ice cream and to Ben for his humor and hilarious impressions of cartoon characters. Finally, I am thankful to Michael Lukacs for the help and guidance he gave me as an undergraduate student that allowed me to pursue this graduate degree. vii Table of Contents Chapter Page 1 INTRODUCTION…………………………………………………………. 1 2 THE THERMODYNAMICS OF AQUEOUS SOLUTIONS……………... 4 2.1 Introduction…………………………………………………………….. 4 2.2 Activity Coefficients…………………………………………………… 6 2.3 Partial and Apparent Molar Properties………………………………… 8 2.4 Debye-Hückel Theory and Pitzer-ion Interaction ……………………....14 2.5 The “Density” Model…………………………………………………... 19 2.6 Young’s Rule…………………………………………………………... 19 3 EXPERIMENTAL EQUIPMENT…………………………………………. 22 3.1 Introduction.............................................................................................. 22 3.2 The Picker……………………………………………………………… 23 3.2.1 The Sodev O2D Vibrating Tube Densimeter………………... 23 3.2.2 The Picker-flow Microcalorimeter…………………………... 28 3.3 The High Temperature and Pressure Vibrating Tube Densimeter…….. 34 4 THERMOCHEMICAL STUDY OF AQUEOUS SOLUTIONS OF THE RARE EARTH ELEMENT (REE) TRIFLATES AT AMBIENT PRESSURE AND NEAR AMBIENT TEMPERATURES………………... 45 4.1 Introduction…………………………………………………………….. 45 4.2 Trifluoromethanesulfonic Acid in Aqueous Solution………………….. 46 4.2.1 Experimental…………………………………………………. 46 4.2.2 Results and Conclusions……………………………………... 47 4.3 NaCF3SO3 in Aqueous Solution……………………………………….. 56 4.3.1 Experimental…………………………………………………. 56 4.3.2 Results and Conclusions……………………………………... 57 4.4 The REE Triflates in Aqueous Solution……………………………….. 66 4.4.1 Experimental…………………………………………………. 66 4.4.2 Results and Conclusions……………………………………... 68 5 A THERMOCHEMICAL STUDY OF AQUEOUS SOLUTIONS OF SELECTED REE TRIFLATES OVER AN EXTENDED SURFACE OF TEMPERATURE AND PRESSURE………………………………….. 94 5.1 Introduction…………………………………………………………….. 94 5.2 Trifluoromethanesulfonic Acid in Aqueous Solution………………….. 95 5.3 The REE Triflates in Aqueous Solution……………………………….. 105 6 THE MODELING OF APPARENT MOLAR PROPERTIES OF AQUEOUS SOLUTIONS OF THE REE TRIFLATES OVER THE TEMPERATURE RANGE T = (288.15, 298.15, 313.15, 323.15, 328.15, 348.15, 373.15, AND 423.15) K AND PRESSURE RANGE p = (0.1, 5.00, 10.00, and 15.00) MPa……….. ………………………………………126 6.1 Introduction…………………………………………………………….. 126 6.2 Modeling of Apparent Molar Volumes and Apparent Molar Heat Capacities of Aqueous Solutions of the REE Triflates Over the Temperature Range 288.15 ≤ T /(K) ≤ 328.15 K and p = 0.1 MPa…………126 viii 6.3 Modeling of the Apparent Molar Volumes of Aqueous Solutions of the REE Triflates over the Temperature Range 288.15 ≤ T /(K) ≤ 423.15 K and the Pressure Range 0.1 ≤ p /(MPa) ≤ 15.00………………. 134 7 CONCLUSIONS AND POSSIBLE FUTURE DIRECTIONS……………. 138 REFERENCES…………………………………………………………………….. 142 ix List of Tables Table Page 3.1 A comparison of apparent molar volume values at infinite dilution, 0 V2 , for NaCl(aq) solutions at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa………………………………………………… 27 3.2 A comparison of apparent molar heat capacity values at infinite 0 dilution, Cp2 , for NaCl(aq) solutions at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa……………………………………………. 34 3.3 Comparison of ρexpt and V2φ of NaBr(aq) determined using the modified vibrating tube densimeter with values that were calculated using Archer’s (1991) program for NaBr(aq)…………………………………….... 41 4.1 Calculated relative densities, relative massic heat capacities, apparent molar volumes, and apparent molar heat capacities of aqueous solutions of CF3SO3H at known concentration at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa………………………………………………… 53 4.2 Estimates of parameters of parameters to the Pitzer-ion interaction model equations, shown as equations (2.37) and (2.38), for aqueous solutions of CF3SO3H at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa……………………………………………………………. 55 4.3 Estimates of parameters to equations (4.1) to (4.8) that model the temperature dependences of V3φ and Cp,3φ values for aqueous
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