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Open Rxg276 Final Thesis 2017.Pdf The Pennsylvania State University The Graduate School Department of Chemical Engineering CHEMICALLY-DRIVEN TRANSPORT OF COLLOIDAL PARTICLES AND MOLECULES A Dissertation in Chemical Engineering by Rajarshi Guha 2017 Rajarshi Guha Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August 2017 The dissertation of Rajarshi Guha was reviewed and approved* by the following: Darrell Velegol Distinguished Professor of Chemical Engineering Committee Co-Chair Dissertation Co-Advisor Manish Kumar Professor of Chemical Engineering Committee Co-Chair Dissertation Co-Advisor Ayusman Sen Distinguished Professor of Chemistry Dissertation Co-Advisor Thomas K. Wood Professor of Chemical Engineering Special Signatory Dissertation Co-Advisor Michael Hickner Professor of Materials Science and Engineering, Chemical Engineering Philip Savage Professor of Chemical Engineering Head of the Department of Chemical Engineering *Signatures are on file in the Graduate School iii ABSTRACT Chemically-driven transports are ubiquitous in nature and govern the working principles of several biochemical processes. Understading the mechanisms involved in such transport processes would enable us to answer and potentially solve many problems in separation, diagnostics, energy, electronics and communications. In this dissertation, I primarily addressed chemically-driven transports which arise from artificial and natural concentration gradients. The two major chemically-driven transports discussed in this dissertation are electrokinetic transport and molecular chemotaxis. Diffusiophoresis and diffusioosmosis are electrokinetic flows of colloidal particles and fluids respectively, which result from interaction of ionic concentration gradients with charged surfaces. Molecular chemotaxis, on the other hand, is solely driven by chemical potential gradients and dictated by the binding affinity between two molecules. High pressure reverse osmosis membrane separation peocesses are limited by fouling phenomena which limit the process efficiency and result in frequent shutdowns. This problem was addressed first by identifying diffusiophoresis as one of the leading mechnaisms of colloidal fouling in reverse osmosis systems and then a scalable solution was proposed by modifying the membrane surface with catalytic activity. Diffusiophoresis and diffusioosmosis mechanisms were also found to exist in an evaporating droplet with salt and colloidal particles, which result in spatio-temporal modulation of deposited patterns. These electrokinetic mechasims associated with droplet evaporation were successfully used to develop novel particle separation, cancer diagnosis and energy efficient solar cell fabrication. Finally, molecular chemotaxis mechanism of dyes in concentration gradients of neutral polymers was investigated. It was found that hydropobic attraction and charge-dipole interaction between dye and polymer molecules were active mechanism responsible for chemotaxis in microfluidics and dialysis systems. Understanding this phenomenon would enable us to develop novel molecular separation techniques and to build programmable devises implementing chemotactic logic gates. iv TABLE OF CONTENTS List of Figures .......................................................................................................................... viii List of Tables ........................................................................................................................... xix Acknowledgements .................................................................................................................. .xx Chapter 1 Motivation and Research Goals .............................................................................. 1 Motivation .................................................................................................................. 1 Research Goals ........................................................................................................... 5 1.3 Overview of dissertation.............................................................................................7 1.3.1 Diffusiophoresis contributes significantly to colloidal fouling in low salinity reverse osmosis systems ............................................................................................... 7 1.3.2 Reactive Micromixing Eliminates Fouling and Concentration Polarization in Reverse Osmosis Membranes ........................................................................... 8 1.3.3 Modulation of spatio-temporal particle patterning in evaporating droplets: Applications to diagnostics and materials science ........................................... 9 1.3.4 Chemotaxis modulation of molecular dyes with non-covalent interactions…10 References .................................................................................................................. .11 Chapter 2 Diffusiophoresis contributes significantly to colloidal fouling in low salinity reverse osmosis systems ....................................................................................................... 14 Introduction ................................................................................................................ 14 2.2 Materials and Methods. .............................................................................................. 20 2.2.1 Membranes, particles and chemicals………………………………………………….………..20 2.2.2 Reverse osmosis system……………………………………………………………………………...20 2.2.3 Experimental Procedure……………………………………………………………………………...22 2.2.4 Model System Description…………………………………………………..22 2.2.5 Governing Equations………………………………………………………....23 2.3 Results. ...................................................................................................................... 27 2.3.1 Experimental RO flux decline by colloidal fouling depends on the salt used in the experiment…………………………………………………………………………………….27 2.3.2 Modeled Cake Enhanced Concentration Polarization was different for different salts ………………………………………………………………………………………………...28 2.3.3 Different values of CECP for different salts set up different diffusiophoretic driving forces for particle deposition………………………………………………………………….29 2.3.4 Particle deposition rate trends calculated incorporating the effect of DP correlates with experimentally observed cake formation rate and flux decline…………………………32 v 2.4 Discussion .................................................................................................................. 34 2.5 Conclusions……………………………………………………………………….....38 2.6 Acknowledgements .................................................................................................... 38 2.7 References…………………………………………………………………………...38 Chapter 3 Reactive micromixing eliminates fouling and concentration polarization in reverse osmosis membranes………………………………………………………………...42 3.1 Introduction ................................................................................................................ 42 3.2 Materials and Methods ............................................................................................... 47 3.2.1 Polydopamine coating and anchoring of CuO and MnO2 nanoparticles on membrane surfaces Methods of zeta potential measurement .............................. 48 3.2.2 Nanoparticle characterization using XRD, SEM and TEM 2.4.2 Streaming potential .......................................................................................................................... 49 3.2.3 Kinetic evaluation of membrane performance using methylene blue decolorization …………………………...................................................................................49 3.2.4 Cross flow RO system for run time evaluation of membrane performance….49 3.2.5 Biofilm control experiment with E. coli in stirred cell setup………………...50 3.3 Results and Discussion ............................................................................................. 47 3.3.1 Catalytic metal oxide nanoparticles can be successfully grown and immobilized on commercial NF/RO membranes........................................................................47 3.3.2 RO flux decline due to colloidal and organic fouling can be completely reversed by pulse addition of ppm levels of H2O2 to catalytic membranes.........................53 3.3.3 Concentration polarization can be reduced/eliminated by reactive micromixing in the presence of H2O2………………………………………………………….55 3.3.4 CuO NPs reduces bacterial attachment to the membranes…………………....57 3.3.5 Implementability and scale-up considerations from energy perspective for proposed catalytic/ reactive membrane approach………………………………………..58 3.4 Conclusions ............................................................................................................... .60 3.5 Acknowledgements………………………………………………………………….60 3.6 References…………………………………………………………………………...61 Chapter 4 Modulation of Spatio-temporal Particle Patterning in Evaporating Droplets: Applications to Diagnostics and Materials Science ...................................................................... .68 4.1 Introduction…………………………………………………………………………..68 4.2 Materials and Methods…………………………………………………………….....69 4.2.1 Materials .......................................................................................................... .70 Particle Patterning Experiments ...................................................................... .70 4.2.3 Characterization techniques…………………………………………………...71 4.2.4 Zeta potential measurements………………………………………………….72
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