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Open 2017 05 23 Asthagarg Phdthesis Final.Pdf The Pennsylvania State University The Graduate School Department of Chemical Engineering ZETA POTENTIALS AND MINERAL REPLACEMENT AT SURFACES IN SATURATED SALT SOLUTIONS A Dissertation in Chemical Engineering by Astha Garg 2017 Astha Garg Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August 2017 ii The dissertation of Astha Garg was reviewed and approved* by the following: Darrell Velegol Distinguished Professor of Chemical Engineering Dissertation Advisor Chair of Committee Ali Borhan Professor of Chemical Engineering Manish Kumar Assistant Professor of Chemical Engineering Ayusman Sen Distinguished Professor of Chemistry James H. Adair Professor of Materials Science and Engineering, Biomedical Engineering and Pharmacology Janna Maranas Professor of Chemical Engineering and Materials Science and Engineering Graduate Program Coordinator of Chemical Engineering *Signatures are on file in the Graduate School iii ABSTRACT Surfaces, fixed or mobile, exposed to salt solutions interact with the solution and with other surfaces through physical interactions, chemical reactions and transport. Understanding these phenomena is key to discerning the system behavior and subsequently manipulating it. A good handle on saturated salt systems can be of immense benefit to modern science and industry. However, their behavior is not adequately understood, especially from a colloidal and surface chemistry perspective. The complexity of interactions under saturated salt conditions and experimental difficulties in carrying out certain measurements have contributed to our limited understanding in this regard. The subject of this thesis is to characterize and transform the nature of surfaces exposed to saturated salt solutions through an in-depth understanding of the surface charge, fluid transport and dissolution- precipitation phenomena in these systems. The work presented here is conceptually focused on two subjects – zeta potential and mineral replacement. First, I describe careful measurements and interpretation of zeta potential which is a measure of electrical potential at the surface-solution interface. Second, I characterize mineral dissolution-precipitation reactions in terms of fluid flow, the rate and extent of mineral replacement and porosity, under a variety of controlled conditions. These experiments offer insights into the behavior of systems at saturated salt and provide quantitative measurements of key parameters that can be used to evaluate and manipulate the system behavior. iv TABLE OF CONTENTS List of Figures .......................................................................................................................... x List of Tables ........................................................................................................................... xix Acknowledgements .................................................................................................................. xx Chapter 1 Motivation and Research Goals .............................................................................. 1 1.1 Motivation .................................................................................................................. 1 1.2 Research Goals ........................................................................................................... 6 1.2.1 Zeta potential at high salt and saturated salt conditions .................................. 7 1.2.2 Mineral replacement in the KBr-KCl system .................................................. 10 1.2.3 Chemical micro-fracking of calcite through mineral replacement .................. 14 1.3 Organization of the thesis........................................................................................... 16 1.4 References .................................................................................................................. 17 Chapter 2 Theoretical background on Electrokinetics ............................................................. 20 2.1 Definition of zeta potential and the electrical double layer ....................................... 20 2.1.1 Examples and estimates .................................................................................. 21 2.2 Applications of zeta potential..................................................................................... 22 2.3 Classical theory of the EDL ....................................................................................... 23 2.3.1 Spatial distribution of charge – the Poisson-Boltzmann equation ................... 23 2.3.2 Relationship between charge density and surface potential – the Gouy- Chapman model ................................................................................................ 24 2.4 Methods of zeta potential measurement ..................................................................... 25 2.4.1 Electrophoresis based techniques .................................................................... 25 2.4.2 Streaming potential ......................................................................................... 26 2.4.3 Electroacoustics ............................................................................................... 26 2.5 Colloidal stability ....................................................................................................... 27 2.5.1 DLVO theory................................................................................................... 28 2.5.2 Rapid aggregation ........................................................................................... 29 2.6 Electrokinetics ............................................................................................................ 30 2.6.1 Electrophoresis and electro-osmosis ............................................................... 30 2.6.2 Diffusiophoresis and diffusioosmosis ............................................................. 32 2.7 References .................................................................................................................. 33 v Chapter 3 Particle Zeta Potentials Remain Finite in Saturated Salt Solutions ......................... 36 3.1 Abstract ...................................................................................................................... 36 3.2 Introduction ................................................................................................................ 37 3.3 Methods and Materials: .............................................................................................. 41 3.3.1 Measuring Zeta Potentials ............................................................................... 41 3.3.2 Experimental Details ....................................................................................... 42 3.3.3 Particle tracking and analysis .......................................................................... 46 3.3.4 Method Validation ........................................................................................... 49 3.3.5 Monte Carlo Simulations of the EDL.............................................................. 52 3.4 Results & Discussion ................................................................................................. 53 3.4.1 Particle Motions at Frequency 20 .................................................................. 53 3.4.2 Zeta potential measurements of sPSL and aPSL ............................................. 57 3.4.3 Stout and Khair zeta potential ......................................................................... 61 3.4.4 Monte Carlo simulation of the EDL ................................................................ 62 3.5 Summary and Conclusions ......................................................................................... 68 3.6 Author Contributions ................................................................................................. 69 3.7 Copyright Notice ........................................................................................................ 69 3.8 Acknowledgements .................................................................................................... 69 3.9 References .................................................................................................................. 70 Chapter 4 Relative Roles of Kinetics, Transport and Thermodynamics in Pseudomorphic Mineral Replacement ....................................................................................................... 77 4.1 Abstract ...................................................................................................................... 77 4.2 Introduction ................................................................................................................ 78 4.3 Background ................................................................................................................ 80 4.3.1 Steps in the replacement process ..................................................................... 80 4.3.2 Thermodynamics - Lippmann Diagrams ......................................................... 82 4.3.3 Porosity generation .......................................................................................... 85 4.4 Questions .................................................................................................................... 86 4.4.1 Passivation ....................................................................................................... 86 4.4.2 Solution
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