Membrane Technology, Desalination and Water Purification, Physical Modeling and Advanced Characterization of Membranes, Novel and Modified Membranes for Environmental and Energy Applications Interaction of bacteria with surfaces: deposition and biofouling Fuel Cell Membranes
Transport of ions and molecules in membranes
The molecular mechanisms, by which membranes selectively separate water, salts and neutral molecules is still poorly understood. We develop advanced thermodynamic and transport models and use modern characterization techniques (AFM, EM, IR spectroscopy, electrochemistry etc.) to get insight into transport and selectivity mechanisms. This knowledge is crucial for process engineering and developing better membranes.
Modification of commercial membranes for improved performance
Industrial separation membranes are highly optimized for high removal of salt (RO, NF) or polymers and colloids (UF). Yet they offer suffer from unfavorable fouling and biofouling characteristics and poor selectivity towards certain solutes (e.g., boron in seawater desalination.) We develop facile surface modification techniques employing graft-polymerization for improved selectivity and mitigation to membrane fouling and biofouling. We also seek fundamental understanding of mechanisms that control membrane selectivity as well as fouling and biofouling of membranes.
Development of novel types of composite membrane
Development of novel types of composite membrane with unique selectivity. Current and recent projects include biomimetic membranes, electrochemically-deposited thin-films and mosaic membranes with enhanced passage of multivalent ions.
Membranes for fuel cells
Fuel cells employ ion-selective membranes such as Nafion. The application is highly demanding and required thorough understanding of the ion and water transport within the membrane and their relation to membrane structure and hydration. This understanding is utilized to build more efficient membranes with enhanced ionic conductivity by embedding Nafion in a highly oriented solid matrix.
Interaction of bacteria with surfaces: bacterial deposition and fouling-resistant surfaces
Many types of bacteria may colonize and foul surfaces by forming biofilms. The process usually starts as initial deposition of individual bacteria and, once they reach a critical density of bacteria, biofilm formation is triggered. The initial deposition involves both hydrodynamics and physic-chemical interactions (adhesion) between bacterial cells and surface. Our research centers on
(a) understanding and separating the roles of hydrodynamic and adhesive forces in initial deposition
(b) designing deposition experiments that would measure propensity of surfaces (especially, fouling-resistant membranes) to bacterial deposition and biofouling.
D. Dlamini, M. Bass, S. Levchenko, B.B. Mamba, E. Hoek, J.M. Thwala, V. Freger, Diffusion hindrance of low-molecular-weight solutes in dense membranes: an ATR-FTIR study, Desalination, Special issue on Reverse Osmosis, doi:10.1016/j.desal.2015.03.009
E. Dražević, K. Košutić, V. Kolev, V. Freger, Does hindered transport theory apply to desalination membranes? Environ. Sci & Technol. 48 (2014) 11471–11478
J. Gutman, Y. Kaufman, K. Kawahara, S. L. Walker, V. Freger, M. Herzberg, The interactions of glycosphingolipids and lipopolysaccharides with silica and polyamide surfaces: Adsorption and viscoelastic properties, Biomacromolecules, 15 (2014) 2128–2137
Y. Kaufman, S. Grinberg, C. Linder, E. Heldman, J. Gilron, Yue-xiao Shen, M. Kumar, V. Freger, Supported Bolaamphiphile Membranes for Water Filtration: Role of Lipid-Support Interactions, in J. Memb. Sci., 457 (2014) 50–61
J.W. Wang, D.S. Dlamini, A.K. Mishra, M.T.M. Pendergast, M.C.Y. Wong, B.B. Mamba, V. Freger, A.R.D. Verlifde, E.M.V. Hoek, Critical Review of Transport through Osmotic Membranes, J. Memb. Sci., 454, (2014) 516-537
R. Bernstein, V. Freger, J.-H. Lee, Y.-G. Kim, J. Lee, M. Herzberg, “Should I stay or should I go?”: Bacterial attachment versus biofilm formation on surface-modified membranes, Biofouling, 30 (2014) 367–376,
V. Kolev, V. Freger, Hydration, Porosity and Water Dynamics in the Polyamide Layer of Reverse Osmosis Membranes: a Molecular Dynamics Study, Polymer, 55 (2014) 1420-1426.
E. Dražević, K. Košutić, V. Freger, Permeability and selectivity of reverse osmosis membranes:correlation to swelling revisited, Water Research 49 (2014) 444-452
E. Margalit, A. Leshansky, V. Freger, Modeling and analysis of hydrodynamic and physicochemical effects in bacterial deposition on surfaces, Biofouling, 28 (8) (2013) 977-989
I. Marcus, M. Herzberg, S. Walker, V. Freger, Pseudomonas aeruginosa attachment on QCM-D Sensors: The role of cell and surface hydrophobicities, Langmuir, 28 (15) (2012) 6396–6402
R. Bernstein, S. Belfer, V. Freger, Improving boron removal in RO using membrane modification: Feasibility and challenges, Environ. Sci & Technol., 45 (2011) 3613-20
S. Bason, Y. Kaufman, V. Freger, Analysis of ion transport in nanofiltration using phenomenological coefficients and structural characteristics, J. Phys. Chem. B, 114 (2010) 3510–3517
M. Bass, A. Berman, A. Singh, O. Konovalov, V. Freger, The surface structure of Nafion in vapor and liquid, J. Phys. Chem. B, 114 (2010) 3784–3790
Y. Kaufman, A. Berman, V. Freger, Supported lipid bilayer membranes for water purification by reverse osmosis, Langmiur, 26(10) (2010) 7388–7395.
V. Freger, Hydration of Ionomers and Schroeder’s Paradox in Nafion, J. Phys. Chem. B, 113(1) (2009) 24-36
M. Bass, V. Freger. Hydration of Nafion and Dowex in liquid and vapor environment: Schroeder’s paradox and microstructure, Polymer 49 (2008) 497-506
V. Freger. Diffusion impedance and equivalent circuit of a multilayer film, Electrochem. Communications, 7 (2005) 957–961.
V. Freger. Swelling and morphology of the skin layer of polyamide composite membranes: an AFM study, Environ. Sci & Technol., 38 (2004) 3168-3175
V. Freger. Nanoscale heterogeneity of the polyamide membranes obtained by interfacial polymerization, Langmuir, 19 (2003) 4791-4797.