Symposium Organizers
John Georgiadis University of Illinois, Urbana-Champaign
Randall T. Cygan Sandia National Laboratories
Maria M. Fidalgo de Cortalezzi Buenos Aires Institute of Technology
Thomas M. Mayer Sandia National Laboratories
V1: Challenges and Opportunities in Water Treatment
Session Chairs
Tuesday PM, November 27, 2007
Room 308 (Hynes)
9:30 AM - **V1.1
Challenges in Water R&D Directions.
Raphael Semiat 1 2
1 Chemical Engineering, Technion IIT, Haifa Israel, 2 Grand Water Research Institute, Technion IIT, Haifa Israel
Show AbstractThe world is facing drought. Many countries are suffering from lack of water or polluted water. Desalination techniques can convert seawater, brackish or slightly polluted water into drinkable high quality water. Solutions based on evaporation techniques and membrane processes can be applied, yet the cost is still high for farmers who live on simple agriculture. Proximity to the ocean facilitates seawater desalination. Desalination of brackish water and the treatment of sewage water and industrial wastewater is the key for solving environmental problems while helping to resolve the water shortage situation. More R&D is needed in order to further reduce the cost of the produced water.New technologies are needed for making improved membranes for different types of water treatment. Development of better heat transfer surfaces may improve significantly the cost of evaporation processes. Better surface treatments are needed to prevent fouling of different types and to prevent corrosion. Better understanding required, of the fouling mechanisms, the interaction between the foulants, the surfaces and new and old types of anti-foulants molecules, prevention of bio films and more. New techniques are needed for the removal of special contaminants – organic matter, arsenic, boron, nutrients and other contaminates, either with large surface nano catalysts or easy to regenerate adsorbents.It is important to note that water is the cheapest commodity on earth. The new technologies need to accommodate the low cost of water and the related problematic issues for the farmers, while maintaining good quality of the product.
10:00 AM - **V1.2
Modifying Polyamide Membrane Performance by Form Complexes With the Acid Chloride Monomer.
William Mickols 1 , Jim Thorpe 1
1 , Dow FilmTec, Edina, Minnesota, United States
Show AbstractShortly after their invention, thin film composites became the dominant membranes in both reverse osmosis and nanofiltration. The FT-30 technology has been growing quickly over the past 20 years and has become the dominant desalination technology in both seawater and brackish water. The individual membrane installations have also grown in size. The number of standard eight inch by forty inch long elements in a single water purification plant has risen to 50,000 and will double in the near future. Growth will continue to accelerate as long as the pressure required to produce the needed water decreases and the purity increases. This requires an increase in the membrane A-value and maintaining or decreasing the B-value. FT-30 thin film composite membranes are composed of a thin aromatic polyamide supported on a porous polysulfone support. Modifying the formation of thin film composite polyamide membranes is an important area for improving the performance of these membranes. We have developed chemicals that form a complex with the acid chloride (one of the monomers) use to produce the aromatic polyamides. In this case the compounds form complexes with the acid chloride monomer used in the membrane production. The complex forms in solution when the modifier has the correct site. The central site can be a metal or a near metal. The other portion of the molecule is the organic portion of the molecule which allows these metals and non metals to be readily soluble in the same solvents as the acid chloride. The addition of these additives can improve the flux of the membrane by up to fifty percent. The concentration dependences indicate a one to one stoichiometric ratio gives the best performance. The remarkably low concentrations affect the bulk properties of the solvent minimally. One class of the additives was the tri-phenyl derivatives of metals from phosphorous through bismuth. Changing the electronegativity through this sequential modification of the additives changes the improvement in flux from 0 to 50%. These tri-phenyl derivatives have pyramidal structures where the phenyl moieties occupy three out of the four sites. One site is the exposed metal which makes up the binding site.The addition of these compounds improve the flux of the membrane by up to 50% giving new possibilities and new membrane performance.
10:30 AM - **V1.3
Carbon Nanotube Nanofluidics.
Francesco Fornasiero 1 , Hyung Gyu Park 1 2 , Jason Holt 1 , Michael Stadermann 1 , Costas Grigoropoulos 2 , Aleksandr Noy 1 , Olgica Bakajin 1
1 Chemistry, Materials & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Mechanical Engineering Department, University of California Berkeley, Berkeley, California, United States
Show AbstractCarbon nanotubes are an excellent platform for the fundamental studies of transport through channels commensurate with molecular size. Water transport through carbon nanotubes is also believed to be similar to transport in biological channels such as aquaporins. I will discuss the transport of gas, water and ions through microfabricated membranes with sub-2 nanometer aligned carbon nanotubes as ideal atomically-smooth pores. The measured gas flow through carbon nanotubes exceeded predictions of the Knudsen diffusion model by more than an order of magnitude (1). The measured water flow exceeded values calculated from continuum hydrodynamics models by more than three orders of magnitude and is comparable to flow rates extrapolated from molecular dynamics simulations and measured for aquaporins(1). More recent reverse osmosis experiments reveal considerable ion rejection by our membranes. Based on our experimental findings, I will discuss our current understanding of the fundamentals of water and gas transport and of ion rejection. I will also explore the potential application space that exploits these unique nanofluidic phenomena. The extremely high permeabilities of these membranes, combined with their small pore size will enable energy efficient filtration and eventually may decrease the cost of water desalination and of separations of industrial gases and biomolecules. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48, with funding from LLNL’s LDRD program, DARPA, & NSF. [1] J. Holt, H.G. Park, Y. Wang, M. Stadermann, A.B. Artyukhin, C.P. Grigoropoulos, A. Noy and O. Bakajin, Fast Mass Transport Through Sub-2-Nanometer Carbon Nanotubes, Science, 312, 1034 (2006)
11:30 AM - V1.4
Physical Characterization of a Model System Designed to Elucidate Interactions in Polyamide Reverse Osmosis Membranes.
Dale Huber 1 , Bruce Bunker 1 , Chrisopher Orendorff 1 , Todd Monson 1 , Todd Alam 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractThe interactions of water and salt with a reverse osmosis membrane are critical to the advancement of this technology, but are difficult to characterize in a structurally complex system such as a commercial membrane. We have taken the approach of developing a similar, but simpler model system to begin probing the molecular level interactions that govern performance. Towards this end, we have synthesized a series of polymer monolayers of nylon-6,6 using an in situ growth approach. This methodology allows us to produce a thin film of nylon with strictly controlled molecular weight and a high graft density. This produces a convenient model system with a smooth, even surface and a well-controlled structure that is conducive to surface sensitive analyses. These films are chemically similar to the polyamide and polyaramid films used in commercial reverse osmosis membranes but are more easily characterized and are more reproducibly made in a laboratory environment. We have characterized these films both dry and in contact with water and water vapor using a variety of surface sensitive techniques including neutron reflectometry, solid state NMR, and a quartz crystal microbalance. When dry, the nylon monolayers are fully dense and appear highly crystalline, a surprising result for such thin films. When exposed to water or water vapor, the polymers become disordered and mobile and there is evidence for localization of water in specific regions of the polymer. We have also seen evidence for the segregation of salts in the vicinity of these thin polymer films. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
11:45 AM - V1.5
Model Reverse Osmosis Membrane Thin Films: A Spectroscopic Investigation of Structure and Water Interactions.
Christopher Orendorff 1 , Todd Alam 1 , Dale Huber 1 , Bruce Bunker 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractReverse osmosis (RO) membranes play a critical role in global water desalination and remediation efforts and are ubiquitous in commercial operations. The performance of these membranes, typically made of polyamides or cellulose acetate polymers, is dominated by interactions at the water/polymer interface. We have developed thin polymer films as experimental models to study these interfacial interactions of RO systems. The structure of Nylon 6,6 thin films and their interactions with water are characterized by solid-state NMR and vibrational spectroscopy to give a detailed molecular understanding of the interface. In the dehydrated state, films are predominantly amorphous with evidence for Nylon chain-chain interactions due to hydrogen-bonding. Upon exposure to water, chain-chain hydrogen bonding is disrupted by hydrating water; imparting significant disorder in these systems. Results will lead to a better understanding of current membrane material behavior and improved performance of next generation materials. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.
12:00 PM - V1.6
Interactions of Single Wall Carbon Nanotubes with Hydrated Ions.
Apurva Mehta 1 , Samuel Webb 1 , Erik Nelson 1 , Jason Holt 2
1 , Stanford Synchrotron Radiation Laboratory, Menlo Park, California, United States, 2 Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractThe determination of hydrated ion structure is one of the major endeavors in the field in ionic solution chemistry and is relevant in fields such as electrochemistry, catalysis, and desalination. Prior studies [1] have indicated that under supercritical conditions, for example, rubidium ion coordination changes dramatically relative to that in bulk solution. A more recent study [2] suggests that nanoscale confinement within the pores of activated carbon leads to a large decrease in water coordination around both cations and anions and an ordered structure.Another model nanoscale channel suitable for investigations of confinement-induced ordering and ion coordination changes is a single wall carbon nanotube (SWCNT). Recent work has demonstrated enhanced water flow through sub-2nm CNT membranes [3], with potential applications in desalination. Knowledge of how ions are structured at the interface with these hydrophobic, nanoscale channels will prove useful in tailoring the design of such membranes for this application.We have carried out x-ray absorption spectroscopy measurements to examine the structure of hydrated Rb and Br ions interacting with CNTs. Examining the Br-edge, we note pronounced differences in the pre-edge region for Br interacting with the CNTs relative to bulk solution. These differences may relate to an electronic interaction between the hydrated Br ions and the CNTs. Modeling work is underway to better understand this phenomenon. Examining the extended x-ray region (EXAFS) of the Br spectrum, we also note pronounced differences between CNT samples and bulk solution. While the bulk RbBr solution reveals the expected octahedral coordination for Br-, with a mean Br-O distance of 3.27Å, the CNT sample shows a very different coordination, with the data best fit by a two shell model. A few water molecules (~3) are coordinated at a Br-O distance of 2.73Å, while a much larger number (~9) are coordinated in a second shell at a distance of 3.33Å, similar to that of bulk solution. Whether this higher water density reflects the hydrophobicity of the CNT surface or is confinement-related is not clear at present. Experiments underway with other graphene-like materials should help shed light on this issue.References[1] Fulton et al., J. Chem. Phys. 105, 2161 (1996).[2] Ohkubo et al., J. Am. Chem. Soc., 124, 11860 (2002).[3] J. K. Holt, H. G. Park et al., Science 312, 1034 (2006).This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48 with funding from the LDRD program.
12:15 PM - V1.7
Ion Permeation into Synthetic Nanopores Based on Electronic Structure Calculations.
Kevin Leung 1
1 Surface and Interface Sciences, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractAccurate predictions of free energy changes associated with salt permeation into water-filled synthetic nanopores are potentially critical for designing novel, solid state osmotic membranes for water treatment. Large scale Density Functional Theory (DFT) calculations, which accurately account for the electronic polarizability of water and the material substrate as well as the electrostatic environment in nanopores, may revolutionize our modeling and understanding of such processes. We apply DFT, ab initio molecular dynamics (AIMD), and DFT-parameterized force fields to examine sodium and chloride ions inside carbon nanotubes (CNT) and nanoporous silica. After applying appropriate corrections, these ions are found to exhibit binding energies of up to several eV inside dry, metallic CNT arrays, which suggests that the electronic polarizability of nanotubes may not be negligable when determining their potential use as osmotic membranes. We also apply coarse-grained pore models and atomistic water force fields to examine the consequences of silica nanopore interior surface charge distributions previously determined using DFT-based calculations [Leung, Rempe & Lorenz, Phys. Rev. Lett. 96:095504 (2006)]. We will show that selective surface functionalizations may lead to strong interactions between ions and nanopore surfacess that are poorly screened by the confined water. These interactions may be exploited for preferential ion transport in or exclusion from synthetic membranes. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S.~Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL8500.
12:30 PM - **V1.8
Creating Advanced Water Treatment Membranes using Nanocomposite Materials Technology.
Eric Hoek 1 2
1 Henry Samueli School of Engineering & Applied Science, UCLA, Los Angeles, California, United States, 2 , UCLA California NanoSystems Institute, Los Angeles, California, United States
Show AbstractMost membranes used globally for desalination and advanced water treatment processes are based on polymer materials concepts that are now more than 30 years old. Optimal separation performance, energy efficiency, and fouling resistance of conventional polymeric membranes are nearly fully realized, but membrane filtration and desalination processes remain relatively non-selective, energy-intensive, and fouling-prone. These constraints remain in the face of rising worldwide demand for clean water and the sustainability imperatives to control energy use. However, the ‘age of nanotechnology’ has brought forth entirely new classes of functional materials that can be explored for use in creation of advanced water treatment membranes. For example, we are exploring new methods of fabricating reverse osmosis membranes using nanocomposite materials technology. Low-energy and fouling-resistant membranes already have been created and tested in the laboratory. Preliminary results from our laboratory research will be presented and I will discuss the potential implications and applications for nanocomposite membrane technology in desalination and advanced water treatment.
V2: Organic Fouling and Fundamentals
Session Chairs
Tuesday PM, November 27, 2007
Room 308 (Hynes)
2:30 PM - **V2.1
Atomic Force Microscopy as a Tool to Characterize the Fouling Mechanisms of Polymeric Membranes by Biomacromolecules.
Menachem Elimelech 1 , Anne Mayes 2 , Seoktae Kang 1 , Ayse Asatekin 2
1 Chemical Engineering, Yale Univ, New Haven, Connecticut, United States, 2 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractIn this presentation, we will describe the use of interfacial force measurements by atomic force microscopy (AFM) to characterizes the fouling mechanisms of polymeric reverse osmosis, nanofiltration, and ultrafiltration membranes by biomacromolecules (proteins and polysaccharides). We will highlight the specific role of divalent cations, such as calcium and magnesium. Our work demonstrates that the rate of fouling is directly proportional to the magnitude of the measured adhesion forces. The adhesion forces are significantly increased by bridging of biomacromolecules by calcium ions. In addition to illuminating the mechanisms of membrane fouling, we will illustrate the use of interfacial force measurements to explain the antifouling mechanisms of a novel ultrafiltration membrane incorporating hydrophilic brush layers.
3:00 PM - V2.2
A Molecular Basis for Biofouling: Interactions of Alginic Acid, Aqueous Ions, and Membranes.
Randall Cygan 1 , Thomas Perry 2
1 Geochemistry Department, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractA molecular understanding of porous membrane materials—the critical component of modern water treatment methods—can have a profound impact on water supply, decontamination, and desalination technologies. Of considerable practical importance in the use of these membranes, which are often vulnerable to degradation by biofouling and other organic-related processes, is the maintenance of high flux and selectivity for water purification. The microbial content of surface water, groundwater, and even treated water can readily produce significant amounts of nano-sized fouling materials that preferentially bind to the polymeric reverse osmosis (RO) membranes and ultimately lead to degraded performance. Progress in desalination technology demands a scientific understanding of the nanoscale and molecular processes associated with the organic fouling of membranes. Only then can RO membranes be intelligently engineered for both high-chemical selectivity, fast transport of pure water, and long lifetimes with minimal fouling. Toward this goal, we have used molecular simulations to develop a fundamental understanding of how alginate interacts with aqueous ions and various functional groups of the RO membrane. Alginate is used as a model exudate to provide a relatively simple compound to represent the complex chemistries and structures associated with natural microbial extracellular polymeric substances (EPS).Classical and quantum-based molecular simulations of alginate systems provide a comparison of the binding strengths of various functional groups with selected metal cations. These competitive interactions are also important with regard to alginate-membrane interactions and have significant impact on the selectivity of metal cations and efficient desalination. Conformations of disacharride and polysaccharide models of alginate and their influence on cation binding were critically evaluated. Molecular dynamics simulation of the torsion angles of the ether linkage between various monomeric subunits identified local and global energy minima for selected disaccharides. The ability of disaccharide subunits and selected polymer models to bind calcium and magnesium ions was also investigated. Structural and energy differences are controlled, in part, by the torsion of the ether linkage between monosaccharide units of the alginate.Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
3:15 PM - V2.3
Antimicrobial Behavior of Ceramic Thin Films.
Roger Narayan 1 , R. Brigmon 2 , C. Berry 2
1 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States, 2 Environmental Biotechnology Section, Savannah River National Laboratory, Aiken, South Carolina, United States
Show AbstractMicroorganisms can colonize water-carrying surface and form sessile communities known as a biofilms. The sustained delivery of antimicrobial agents into the local environment may prevent biofilm formation and avoid large, ongoing costs associated with chemical agents. We have examined the use of novel diamondlike carbon-based ceramic thin films with antimicrobial properties. These materials were examined using scanning electron microscopy, transmission electron microscopy, visible Raman spectroscopy, and nanoindentation. Transmission electron microscopy of the DLC-silver and DLC-platinum composite films revealed that the silver and platinum self-assemble into nanoparticle arrays within the diamondlike carbon matrix. Microbial biofilm attachment testing was performed using gram positive bacteria. It is believed that a galvanic couple forms between platinum and silver, which accelerates silver ion release and provides more robust antimicrobial activity. These materials may provide unique biological functionalities and improved lifetimes for next generation water-carrying systems.
3:30 PM - V2.4
Anti-fouling Ultrafiltration Membranes Containing Polyacrylonitrile-graft-poly(ethylene oxide) Comb Copolymer Additives.
Ayse Asatekin 1 , Seoktae Kang 3 , Menachem Elimelech 3 , Michael Rubner 2 , Anne Mayes 2
1 Department of Chemical Engineering, MIT, Cambridge, Massachusetts, United States, 3 Department of Chemical Engineering, Yale University, New Haven, Connecticut, United States, 2 Department of Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractMembrane fouling is one of the most important challenges faced in membrane ultrafiltration (UF) operations. In this study, polyacrylonitrile-graft-poly(ethylene oxide) (PAN-g-PEO), an amphiphilic comb copolymer with a water-insoluble polyacrylonitrile (PAN) backbone and hydrophilic poly(ethylene oxide) (PEO) side chains, was used as an additive in the manufacture of novel PAN UF membranes. During casting, the PAN-g-PEO additive segregates to form a PEO brush layer on all membrane surfaces, including internal pores. Wettability, pure water permeability, and resistance to irreversible fouling increased with the addition of PAN-g-PEO. In 24-hour dead-end filtration studies, blend membranes prepared with 20 wt% PAN-g-PEO (comb PEO content: 39 wt%) were found to resist irreversible fouling by 1000 ppm solutions of bovine serum albumin (BSA), sodium alginate, humic acid, and produced water from an oil well, recovering the initial pure water flux completely by a pure water rinse or backwash. This exceptional anti-fouling performance holds promise for extending UF membrane lifetimes without need for aggressive cleaning procedures. Furthermore, in cross-flow tests, the retention of BSA by the membrane was observed to be constant. This indicates the possibility of separating macromolecules without a shift in the molecular weight cut-off in time due to fouling.
3:45 PM - V2.5
Mechanisms of Organic Fouling of Forward Osmosis (FO) Membranes.
Baoxia Mi 1 , Menachem Elimelech 1
1 Environmental Engineering, Yale University, New Haven, Connecticut, United States
Show AbstractForward osmosis (FO) is a relatively new process for water desalination. Application of FO as an alternative to pressure-driven membrane processes (RO and NF) in water treatment has been gaining attention in recent years. To date, however, there are no systematic studies on FO fouling behavior and the governing mechanisms. This study investigates organic fouling of FO membrane from two perspectives: (i) the role of intermolecular adhesion forces in the fouling behavior of different organic foulants, (ii) the mechanisms controlling the flux decline caused by the fouling layer.We use atomic force microscopy (AFM) to study the foulant-membrane and foulant-foulant interactions to gain a better understanding of the fouling mechanisms. Studies are preformed with three organic foulants: alginate, Aldrich humic acid (AHA), and BSA and with various solution chemistries. Comparing the AFM force measurements with the fouling results shows that the foulant-foulant adhesion force plays a very important role in controlling the organic fouling in FO processes. A stronger foulant-foulant adhesion force is generally found to correspond to higher fouling rate. We also use a mathematical model to identify the mechanisms controlling the flux decline caused by the adsorbed alginate fouling layer. There are two ways for the fouling layer to cause flux decline: one is by increasing hydraulic resistance, and the other by enhancing concentration polarization (enhanced osmotic pressure). We found that enhanced osmotic pressure plays a more important role than hydraulic resistance in causing the flux decline in FO processes.
4:30 PM - **V2.6
Metastable Statics and Dynamics of Liquid Water.
Eugene Stanley 1
1 Dept. of Physics, Boston Univ., Boston, Massachusetts, United States
Show AbstractWater is perhaps the most ubiquitous, and the most essential, of any molecule on earth. Indeed, it challenges the imagination of even the most creative science fiction writers (such as K. Vonnegut) to picture what life would be like without water, and one often hears the adage "biology cannot be understood until water is understood"). Despite 300 years of research, however, the 63 anomalies that distinguish water from other liquids lack a coherent explanation (http://www.lsbu.ac.uk/water/anmlies.html) so sometimes water is called the prototype "complex fluid". This talk will introduce some of these 63 unsolved mysteries, and will demonstrate some recent progress in solving them using concepts borrowed from various disciplines including chemistry and physics. In particular, we will present evidence from experiments designed to test the hypothesis [1,2] that water displays a special transition point (which is not unlike the "tipping point" immortalized in Malcolm Gladwell's book of the same title). The general idea that when water is near this tipping point, it can separate into two distinct liquid phases distinguished by their density. This new concept of a critical point is also proving useful in understanding some of the anomalies of other liquids, such as silicon, silica, and carbon.The talk will also discuss related water mysteries, such as the puzzling behavior of water near a protein [3], and the breakdown of the Stokes-Einstein relation in supercooled water [4].This work, supported by the NSF Chemistry Division, has been carried out with many collaborators, among whom are S. V. Buldyrev, P. Kumar, P. H. Poole, F. Sciortino, and L. Xu, and has been heavily influenced by a number of experimentalists including S.-H. Chen, F. Mallamace, O. Mishima, and J. Teixeira.1. P. H. Poole, F. Sciortino, U. Essmann, and H. E. Stanley, "Phase Behavior of Metastable Water", Nature 360, 324 (1992).2. L. Xu, P. Kumar, S. V. Buldyrev, S.-H. Chen, P. H. Poole, F. Sciortino, and H. E. Stanley, "Relation between the Widom Line and the Dynamic Crossover in Systems with a Liquid-Liquid Critical Point", Proc. Natl. Acad. Sci. 102, 16558 (2005). 3. P. Kumar, Z. Yan, L. Xu, M. G. Mazza, S. V. Buldyrev, S.-H. Chen. S. Sastry, and H. E. Stanley, "Glass Transition in Biomolecules and the Liquid-Liquid Critical Point of Water", Phys. Rev. Lett. 97, 177802 (2006).4. P. Kumar, S. V. Buldyrev, S. L. Becker, P. H. Poole, F. W. Starr, and H. E. Stanley, "Relation between the Widom line and the Breakdown of the Stokes--Einstein Relation in Supercooled Water", Proc. Natl. Acad. Sci. 104, 9575 (2007).
5:00 PM - V2.7
Development and Application of an Accurate Dissociative Water Potential for Bulk and Confined Water and for Water-Silica Interactions.
T. Mahadevan 1 , Stephen Garofalini 1
1 Materials Sci. and Eng., Rutgers University, Piscataway, New Jersey, United States
Show AbstractA new interatomic potential for water that allows for dissociation of the water molecule and matches experimental liquid properties, such as the liquid equation of state, structure, diffusion, cohesive energy, dipole moment, and frequency spectrum, was developed for use in molecular dynamics simulations. The simulations use a multi-body potential, with both pair and three body terms, and the Wolf summation method for the long-range Coulomb interactions. A major feature in the potential is the use of a subtle change in the short-range O-H repulsive interaction as a function of temperature and/or pressure in order to accurately reproduce the experimental density-temperature curve between 273K and 373K at 1 atm, as well as high pressure data at various temperatures. Using only the change in this one parameter, the simulations reproduce the above-mentioned properties of water, as well as the liquid-vapor coexistence curve. Although the water molecules could dissociate, no dissociation is observed at room temperature. However, behavior of the hydronium ion was studied by introduction of an extra H+ into a cluster of water molecules. Migration of the hydronium complex is observed via multiple exchanges of an H+ ion from one hydronium to an adjacent H2O molecule. Mechanisms of exchange similar to DFT calculations are observed. Both Eigen and Zundel configurations, as well as more complex configurations, are observed in the migration of the hydronium. Application of this potential to simulations of water on silica surfaces shows dissociative surface reactions and hydroxylation of silica and the role of hydroniums in this behavior. Additional reactions involving water in confined spaces and penetration of water into the subsurface will also be discussed.
5:15 PM - V2.8
A Materials Science Review of the Structure of Water and of Useful Ultradilute Aquasols.
Rustum Roy 1
1 Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractThe most abundant ceramic material on earth and the most important to human life and health is water in condensed matter states. The literature on the structure of water, studied largely by chemists, and their data describe mainly the vast array of molecules which may be present. This paper starts with the detailed review of the materials science perspective, based on a century of glass structure research, and on HPHT phase relations in covalently-bonded materials in the liquid state. It presents a new model of the structure of water as the 3-D arrangement of an inhomogenous distribution of molecular (oligomers) in space. Following that, we present detailed data on the structure of ultradilute aquasols with outstanding biological properties which are described briefly. The solid phases are studied by SEM, TEM, HRTEM, Cryo-TEM and the liquid phase by ICP, UV-VIS, Raman and FTIR. In the case of metallic Ag sols, the particles are 30-50 nm clusters consisting of 5-10 nm sub-units often coated with oxide layers. The UV-VIS shows a consistent concentration-dependent set of absorptions within the 200-350 nm range. The Raman spectra are less and the FTIR the least sensitive to change. Similar systematic changes appear with the degree of succussions in both aqua- and alcosols.
5:30 PM - V2.9
Single Mode 2.45 Ghz Microwave Caused Changes in the Structure of Water, and their Remarkable Stability.
Manju Rao 1 , Steven Sedlmayr 2 , Rustum Roy 3 1
1 Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania, United States, 2 , Sedlmayr Technologies, LLC, Paradise Valley, Arizona, United States, 3 School of Materials, Arizona State University, Tempe, Arizona, United States
Show Abstract One of us has demonstrated in a dozen recent papers the most remarkable effects of single mode magnetic fields at 2.45 GHz on de-crystallizing, without melting, the most important technological families of solid, crystalline matter. Ferrites, TiO2, BaTiO3, Si, etc.) In a new device which will be described, this approach has been extended to liquids. In the case of distillation of pure (R-O) water, the 2.45 GHz single mode fields alter the structure and properties of the water very considerably. Extensive characterization data by UV-VIS, Raman spectroscopy and ICP chemical analysis carried out at different institutions will be presented to show the extraordinary structural changes, including in the main O-H stretching band. The changes moreover are stable for at least months, under normal handling.
5:45 PM - V2.10
Resonant Spectral Control of NaCl Crystal Growth from Aqueous Solution.
Amar Bhalla 1 , Ruyan Guo 1 , Juliana Brooks 2 , Mark Mortenson 2
1 Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania, United States, 2 , General Resonance, LLC, Havre de Grace, Maryland, United States
Show AbstractThis paper describes the growth of NaCl crystals from both saturated and unsaturated aqueous NaCl solutions, using resonant spectral irradiation with Na electronic emission wavelengths.Experiments have been conducted and repeated in two institutions. The most significant observations include the following data, obtained under temperature controlled conditions, with: a) resonant spectral irradiation; b) non-resonant irradiation; and c) no irradiation:1)Primary and secondary nucleation rates are both increased with resonant spectral irradiation, compared to either non-resonant irradiation or no irradiation.2)The thermal equilibrium for primary nucleation is shifted to a higher temperature with resonant spectral irradiation. 3)NaCl crystals are grown from thermally unsaturated (3° C hotter) solution using resonant spectral irradiation.4)NaCl crystals are grown from aqueously diluted (1-6%) unsaturated solution using resonant spectral irradiation.5)Crystal morphology is significantly changed using resonant spectral irradiation (e.g. with Na-D line irradiation the 111 growth predominates vs. the 001 growth found without radiation).The relative ease with which resonant spectral irradiation can shift thermal and concentration equilibria in aqueous crystal growth solutions, invites a reconsideration of the basic processes of crystallization as well as the influence of resonant spectral wavelengths in materials processes.
V3: Poster Session: Advanced Water Technology
Session Chairs
Wednesday AM, November 28, 2007
Exhibition Hall D (Hynes)
9:00 PM - V3.1
New Porous Photocatalysts for Effective Water Decontamination.
Maryam Zarei Chaleshtori 1 , Geoffrey Saupe 2
1 Environmental Science and Engineering, University of Texas at El Paso, El Paso, Texas, United States, 2 Chemistry, University of Texas at El Paso, El Paso, Texas, United States
Show Abstract9:00 PM - V3.10
Solid-state NMR Investigation on Al(III) Complexation with Silica Sufaces.
Jacqueline Houston 1 , Julie Herberg 2 , Susan Carroll 1 , Robert Maxwell 2
1 Energy and Environment, Lawrence Livermore National Laboratory, Livermore , California, United States, 2 Chemistry, Materials, Life Sciences , Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractInhibition of silica dissolution rates by dissolved Al(III) has been observed for a number of years. Because sorption of Al(III) has been suggested as the cause for inhibition, characterizing the structural form of Al(III) associated with the silicate solid is crictical towards understanding its surface chemistry. In order to identify the coordination geometry and chemical environment of Al(III), we use both bulk and surface-selective solid-state NMR techniques [27Al MAS-NMR and 27Al{1H} and 27Si{1H} CP/MAS-NMR]. From the 27Al NMR data, the predominate species is tetrahedral Al ([4]Al), and because there is little cross-polarization from protons bound to oxygens near Al(III) sites, [4]Al most likely exists as part of an Al-O-Si framework. Because the [4]Al signal persists even when the dissolved Si concentration is low, we rule out Al-O-Si precipitation and propose an ion exchange mechanism in which dissolved Al exchanges with four-coordinate silicon at the surface of the solid.
9:00 PM - V3.2
Complex Fluids for Membrane-Based Separations.
Sangil Han 1 , Stephen Martin 1
1 Chemical Engineering, Virginia Tech, Blacksburg, Virginia, United States
Show Abstract9:00 PM - V3.3
Polyacrylonitrile-graft-poly(ethylene glycol) (PAN-g-PEG) for Size-selective, Fouling Resistant Nanofiltration (NF) Membranes.
Ayse Asatekin 1 , Elsa Olivetti 2 , Michael Rubner 2 , Anne Mayes 2
1 Department of Chemical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Department of Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractManufacturing high-flux, fouling resistant membranes with good selectivity in the desired size range is among the main challenges of the membrane industry. To address these needs, the amphiphilic graft copolymer polyacrylonitrile-graft-poly(ethylene glycol) (PAN-g-PEG), was synthesized and used in the fabrication of nanofiltration (NF) membranes. NF membranes were prepared by coating commercial ultrafiltration membranes by a thin film of graft copolymer. The incompatibility of the backbone and the side-chains causes phase separation, while the covalent bonds between the two components lead to a large interfacial area between the two phases. The resultant microphase separation creates hydrophilic “nanochannels” that allow water passage and sieve molecules larger than the diameter of the channels. This phase separation was investigated by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Pure water permeability, size selectivity and the fouling resistance of membranes prepared by this method were tested using dead-end filtration cells. These membranes display pure water permeabilities higher than commercial NF membranes as well as high resistance to irreversible fouling by common foulants. Also, the uncharged nature of PAN-g-PEG coated NF membranes is unlike common commercial NF membranes, which are negatively charged. This results in selectivity based only on size, which can be a valuable property for separations in the food and pharmaceutical industries. Its high organic rejections combined with ionic permeability and high flux also make these membranes promising for NF membrane bioreactors.
9:00 PM - V3.4
Wastewater Treatment Using Sunlight and Titanium Dioxide Nanocrystals.
Nathan Roberts 1 , Leslie Van Hoose 1 , Jonathan Gafford 1 , Andrew Ernest 2 , Tingying Zeng 1
1 Chemistry, Western Kentucky University, Bowling Green, Kentucky, United States, 2 Center for Water Resource Studies, Western Kentucky University, Bowling Green, Kentucky, United States
Show AbstractTitanium dioxide (TiO2) is a wide bandgap semiconductor. It is a cheap, non-toxic, harvesting sunlight in the ultraviolet range. Upon the absorption of sunlight, photon-induced electrons and holes are created, and transported to its nanoparticle surface. Substances, such as organic pollutants in wastewater can be decomposed to CO2 and other small non-toxic mineral species once they interact with the electrons or holes due to the redox reactions. This is called photodegradation. We successfully synthesized different morphology TiO2 anatase nanocrystals, and used them to treat rural wastewater. Our research demonstrated the feasibility to effectively photodecompose organic pieces in the wastewater using optimized anatase nanocrystals under light illumination.
9:00 PM - V3.5
Simultaneous Cr(VI) Reduction and Naphthalene Oxidation in Aqueous Solutions by UV/TiO2.
Ricardo Gutierrez 1 , Sergio Flores 1 , Miguel Valenzuela 1
1 Lab. Catalisis y Materiales, Instituto Politecnico Nacional, Mexico City Mexico
Show AbstractHeterogeneous photocatalysis is considered among the new Advanced Oxidation Processes (AOP) for air and water purification treatments. Besides of the main field of application in organic pollutants removal, the photocatalytic water decontamination can also be used for the recovery or the detoxification of inorganic pollutants. Research in our laboratory is directed toward adapting the simultaneous reduction and oxidation reactions by a semiconductor photochemistry approach. Hence, the aim of the present work was to study the simultaneous Cr(VI) reduction and the naphthalene oxidation by aqueous TiO2 suspensions under UV-light illumination (UV/TiO2). Aqueous solutions of K2CrO4 containing 60 ppm of Cr (VI) and 10 ppm of naphthalene were suspended in TiO2 (Degussa, P-25) and irradiated with an array of 8 black light lamps (8W) in a thermostated batch reactor. A nitrogen flow was continuously added to the reactor to purge the dissolved air in the solutions and the pH was varied in the range of 3 to12. UV-Vis and fluorescence spectroscopies were used to determine Cr (VI) and naphthalene concentration, respectively.The effects of reaction time, reactants concentration, pH,TiO2 loading and light intensity on the conversion of Cr(VI) and naphthalene were mainly studied. The reduction reaction rates of Cr (VI) were significantly higher under acidic conditions than the alkaline ones. In contrast, the naphthalene conversion was practically not affected by the pH. The presence of naphthalene functioned as a hole scavenger enhancing the photocatalytic reduction of Cr(VI) by the photogenerated electrons.
9:00 PM - V3.6
Grafting of Cage-molecules on Polymer-modified Surfaces for Selective Heavy-metal Captation.
Sebastien Roussel 1 , Pascal Viel 1 , Laurent Mauclaire 2 , Serge Palacin 1
1 Chemistry of Surfaces and Interfaces, CEA, Gif sur Yvette France, 2 LIONS, CEA, Gif sur Yvette France
Show AbstractAbsorption on resins is often used as secondary step in the treatment of water-based effluents, in order to reach very low concentrations. The separation of the trapped effluents from the resins and the regeneration of the resins for further use create wide volumes of secondary effluents coming from the washings of the resins with chemical reagents. We propose an alternative solution based on a « surface strategy » through adsorption phenomena and electrical control of the expulsion stage. The final goal is to limit or ideally to avoid the use of chemical reagents at the expulsion (or regeneration) stage of the depolluting process.Our "surface strategy" is based on selective complexation of target ions within polymer films grafted on conducting substrates. Selectivity towards designated ions is thus brought by designed complexing sites, such as cage molecules that show selective inclusion properties: cyclodextrins or calixarenes. Recent works have shown, that per (3,6 anhydro) β-cyclodextrin (β-PaCD) exhibit high affinity and selectivity for the Pb2+ and Co2+ captation. In the present work, we grafted β-PaCD derivatives on conducting substrates and studied the affinity of the resulting complexing surface towards Pb2+ and Co2+The parent β-PaCD was modified to allow its grafting: three different groups were tested, each one related to specific electrografted primer. (i) Propanol groups were added to β-PaCD by a functionalization of terminals hydroxyl groups with bromo-propanol. We have noted a polymerization of the propanol which gave access to different length of linker for the immobilization of the molecule. Different substitution degrees of the hydroxyl groups are obtained. The terminal hydroxyl of propanol arm is used to couple the cage molecules to a grafted polyaniline via a di isocyanate linker.(ii) Same propanol groups and di-isocyanate linkers were used to link the modified cyclodextrins to an electrografted PMAN film where the nitrile groups had previously been reduced in amines.(iii) Carboxylic groups were introduced on the β-PaCD by substitution of the hydroxyl group by different carboxylic acid with different chain length . The reaction was carried out with bromo carboxylic acids, which gave different degrees of substitution of hydroxyls group of the β-PaCD. The interest of the variation of the length is to modify the free rotation of the cage molecule once immobilized. The carboxylic acid synthesized was used in a classical peptide coupling with grafted PAA film.The modifications of the β-PaCD will be described, together with the different couplings that were achieved with electro grafted polymer primers. XPS, IRRAS and EQCM were used to characterize the final films.Finally, the captation of Pb2+ by the CD-containing grafted films were followed. First results of electro-induced Pb2+ release from the films will also be given.
9:00 PM - V3.8
Kinetics of Arsenic and Chromium Reduction/adsorption in Water Treated with Micro/nano Iron and Iron Oxide Particles.
Parameswar Hari 1 , Aaron Isley 2 , Greg Medders 2 , Gordon Purser 2
1 Physics, University of Tulsa, Tulsa, Oklahoma, United States, 2 Chemistry and Biochemistry, University of Tulsa, Tulsa, Oklahoma, United States
Show AbstractChromium (Cr) and arsenate species are toxic compounds widely found as contaminants in industrial and metallurgical environments. Environmental health problems related to industrial waste streams and related drinking water contaminations can commonly occur. Around the world- from Bangladeshi water wells to Oklahoman metal plating sites- toxic levels of chromium and arsenic (As) leach into potable water. Our paper describes a flow loop system that relies on magnetic nanoscale particles, iron and iron oxide (nanorust), for the removal of these toxic metals. The nanorust particles have an extremely high surface area which allows for the rapid removal of these metal oxides. Perhaps even more importantly, nanorust (iron oxide) also has the unique advantage that it can be easily removed and re-concentrated using inexpensive low field magnetic (0.290 T) separation techniques. We will present results on treating low and high levels of As and Cr in water with micro (200 microns) particles and nano particles of mesh size ranging from 100 nm to 22 nm and, nanorust of 12 nm in size. Determination of Cr and As concentrations at the PPb level was attained using a ICP-MS and flow-design system. Based on the data obtained in treating As and Cr, we will describe the kinetics of redox and adsorption mechanism of micro iron partices, nano iron and nanorust in removing the toxic metals from contaminated water.
9:00 PM - V3.9
Water, Alcohol and Acetone Liquid Phases under Different Freezing Techniques.
Carlos Chesman 1 , Neymar da Costa 1 , Jose Americo Moura 1 , Dory Helio Anselmo 1 , Ananias Mariz 1
1 Departamento de Física, UFRN, Natal, Rio Grande do Norte, Brazil
Show AbstractWater still shows, on its critical properties and phase transitions, problems of actual scientific interest, mainly because of several open questions, and also because of insufficiency of the current theoretical models, mainly related to the explanation of the several solid phases this substance has. Actually, nowadays we know more than 13 crystalline forms (polymorphism) [1]. To experimentally investigate the behavior of the water solid phases, we have used three cooling techniques (domestic refrigerator, liquid nitrogen and Peltier cell [2]), and employed, as comparing and calibrating systems, alcohol and acetone (both P.A.). In this work the temperatures as functions of freezing time were collected for the three systems. All the freezing measurements were performed were with distilled water (H2O) alcohol (C6H5-OH) and acetone (CH3COCH3) for analysis into a 50.0 ml volume of a Becker. Experimentally, the systems are monitored by a data acquisition unit which has a 20 channels module with GPIB interfacing, on which we can program the readings and save them through appropriate software. The results allow the characterization of the phase transitions liquid-solid on the three liquids, with metastable phase being observed for water, acetone and alcohol, as an indication of the consistency of the different experimental apparatus.[1] P. Debenedetti and H. E. Stanley, Physics Today 40, June (2003).[2] D. Astrain, J.G. Vian JG and J. Albizua, Applied Thermal Engineering, 25 (17-18): 3149, (2005).
Symposium Organizers
John Georgiadis University of Illinois, Urbana-Champaign
Randall T. Cygan Sandia National Laboratories
Maria M. Fidalgo de Cortalezzi Buenos Aires Institute of Technology
Thomas M. Mayer Sandia National Laboratories
V4: Interfacial Properties and Catalysts
Session Chairs
Maria Fidalgo de Cortalezzi
Wednesday AM, November 28, 2007
Room 308 (Hynes)
9:30 AM - **V4.1
Advances in Understanding Water Interfacial Structures with Phase-sensitive Sum-frequency Vibrational Spectroscopy.
Y. Ron Shen 1 , Na Ji 1 , Chungshan Tian 1 , Victor Ostroverkhov 1
1 Physics, University of California at Berkeley, Berkeley, California, United States
Show AbstractMolecular structures of water interfaces are of critical importance in many disciplines. They have been the focus of many recent investigations. Unfortunately there are serious controversies among researchers that make even the qualitative picture of the interfacial structures confusing. In most experimental studies, surface-specific sum-frequency vibrational spectroscopy (SFVS) has been the preferred analytical tool to probe the surface molecular structure. It provides a vibrational spectrum described by absolute square of the surface nonlinear susceptibility, which contains vibrational resonances. The approach often adopted to analyze the spectrum is to fit the observed spectrum by an analytical expression, assuming the resonances in it are discrete. However, the fitting is not unique in practice. Different fittings by different research groups have led to different sets of resonances and hence different interpretations of the interfacial structure. Actually, the assumption of discrete resonances in the water/vapor spectrum is incorrect. Continuous variation of hydrogen-bonding geometry and strength around interfacial water molecules shifts and spreads the OH stretch frequency continuously into a highly inhomogeneously broadened band. To access complete information on the resonant structure, knowing the intensity spectrum is not enough; we need to obtain the spectrum of the imaginary part of the surface nonlinear susceptibility directly from experiment, in analogy to the imaginary part of the optical dielectric constant (for absorption or emission) in linear spectroscopy. Such measurements become possible with the newly developed phase-sensitive SFVS (PS-SFVS). Our applications of PS-SFVS to water interfaces allow us to resolve the existing controversies and obtain better and more detailed understanding of the interfaces. We shall focus on water/vapor interfaces in this talk.This work was supported by NSF-STC WaterCAMPWS and DOE.
10:00 AM - V4.2
Mechanical Properties of Interfacial Water: Water on Model Polymer Surfaces.
Bruce Bunker 1 , Jack Houston 1 , Dale Huber 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractInteractions between water and polymeric materials are critical for applications ranging from water treatment technologies to biomedical materials to coatings for anti-friction and stiction in micromachines and other mechanical devices. In all of these applications, key performance characteristics can be determined by how water organizes itself at the water:polymer interface. We are currently studying how water behaves in the vicinity of self-assembled monolayers that are grown with exact sequences of monomeric units to create model polymer surfaces in which the structure and chemistry of the polymer is known to atomic resolution. This talk will highlight how we are interrogating the mechanical properties associated with the water:polymer interface using a scanning probe system called the interfacial force microscope (IFM). The polymers under investigation are model nylon monolayers in which chain sequences and terminal end groups are systematically varied. With the IFM, we can probe how water influences the mechanical properties of the polymer, as well as how the ordering of water above the nylon surface influences the viscosity and interfacial friction of water near the interface. When combined with results obtained using other techniques (including the quartz crystal microbalance, NMR, vibrational spectroscopy, and neutron scattering), the results show that: 1) Small quantities of water are sufficient to transform the nylon film from a rigid, crystalline phase into a much softer and compliant material (shown by other techniques to be amorphous). 2) A layer of ordered water forms above the immediate nylon:water interface that is up to 4-5 nanometers thick, has a viscosity that is orders of magnitude higher than that of bulk water, and exhibits unusual interfacial friction behavior. Similar layers have been seen previously via IFM on classical anti-fouling polymers such as polyethylene oxide. Variations in the properties of the ordered water will be presented as a function of polymer composition, and the implications of the ordered water on technologies such as reverse osmosis membranes for the purification of salt water will be discussed.
10:15 AM - V4.3
Surface Charge and Hydrodynamic Damping at Solid/Water Interface Studied by Dynamic Atomic Force Microscopy.
Yan Wu 1 , Chaitanya Gupta 2 , Mark Shannon 1
1 Mechanical Science and Engineering, University of Illinois, Urbana, Illinois, United States, 2 Chemical and Biomolecular Engineering, University of Illinois, Urbana, Illinois, United States
Show AbstractRecently there is a growing interest in micro- and nanofluidic devices for selective adsorption and detection of various compounds in water. Quantitative measurements of surface charge and hydrodynamic damping at the solid/water interface are important for understanding fluid transport at the nanometer scale, where the critical dimension of the devices is at the same order of magnitude of the Debye length of the electrolyte solutions. Previous studies have shown the static force curves measured using atomic force microscopy (AFM) can be used to extract the surface charge properties. During a static force curve measurement, the force produced from overlapping electrical double layers is detected by the cantilever deflection signal as a charged AFM probe is brought near a charged sample surface at a constant speed. However, the interaction between the probe and sample at very short distances (less than 3 nm) is often missed in static force measurements due to the “jump into contact” phenomenon. Dynamic force measurements can potentially overcome this barrier since their higher sensitivity makes it possible to use stiffer cantilevers than those used in static measurements. During a dynamic force measurement, the cantilever oscillates at a fixed frequency. The amplitude and phase change of the cantilever oscillation are measured as the probe is brought near the sample surface. Furthermore, dynamic force measurements allow the hydrodynamic damping force to be characterized at the same time as the electrical double layer force. In this study, the dynamic force curve between a mica surface and a silicon nitride probe were measured as a function of tip-sample distance in potassium nitrate solutions with four different salt concentrations, which give four different Debye lengths ranged from 3nm to 30 nm. A linear dynamic model based on the assumption of simple harmonic oscillation was used to relate the measured amplitude and phase signals to the force gradient of the electric double layer interaction and hydrodynamic damping at the solid/water interface. Static force curves of a mica surface probed by a silica colloidal probe in the same potassium nitrate solutions were also measured for comparison. The results demonstrate that dynamic force AFM is capable of capturing the difference in surface charge and hydrodynamic damping between electrolyte solutions with varied ionic strengths at the nanometer range from the solid/water interfaces, which is useful for the design and the characterization of micro- and nanofluidic devices.
10:30 AM - V4.4
A Search for Possible Universal Anomalous Transport of Water in Meso-/Nano- Porous Materials.
Lars Alme 1 , Eduardo de Azevedo 2 , Romulo Tenorio 2 , Jon Fossum 1 , Mario Engelsberg 2 , Paul Dommersnes 1 3
1 Department of Physics, Norwegian University of Science and Technology - NTNU, Trondheim Norway, 2 Departamento de Física , Universidade Federal de Pernambuco - UFPE, Recife Brazil, 3 Laboratoire MSC - Matière et Systèmes Complexes, Universite Paris 7, Paris France
Show AbstractWe have performed Magnetic Resonance Imaging (MRI) studies of liquid water ingress profiles in compressed paper [1] in order to explore possible universal properties of water transport in materials with interconnected meso- and nano- poresizes. The MRI measured moisture profiles in our paper samples are analyzed in terms of anomalous diffusive behaviour using a spatio (x) - temporal (t) scaling variable η = x/tγ/2 (γ ≠ 1 for anomalous diffusion). Previous studies of pressed powder samples of nano-porous zeolite particles [2,3] displayed clear indications of sub-diffusive anomalous diffusion (γ < 1), whereas our paper experiments may indicate near normal diffusive behavior (γ ~ 1).Within the same universal context, we have studied clay samples using X-ray scattering techniques [1,4]. Layered smectite clay particles posses a nano-porous layered structure in which water may intercalate and form discrete water layers [5,6], which could influence the global water transport in inter-particle clay powder meso-pores. By imposing a humidity gradient along cylindrically contained clay powder samples kept at fixed temperature, we have studied quasi-one dimensional water transport in such systems [1,4]. Our X-ray scattering data give information about the spatial ingress of the humidity front in clay powder meso-pores, as well as of water contents intercalated in the particle nano-pores. The two interlinked fronts, i.e. humidity (in meso-pores) and intercalation (in nano-pores), have been analyzed together in terms of the scaling variable η, and as for paper, the clay experiments may suggest near normal diffusive behavior, i.e. γ ~ 1.[1] Lars Ramstad Alme, Water transport in selected nanoporous media, Master thesis - Department of Physics, Norwegian University of Science and Technology (2007)[2] Eduardo N. de Azevedo, D. Vitoreti da Silva, R. E. de Souza, M. Engelsberg, Water ingress in Y-type zeolite: Anomalous moisture-dependent transport diffusivity, Phys. Rev. E 74, 041108 (2006)[3] E.N. de Azevedo, Paulo L. de Sousa, Ricardo E. de Souza, M. Engelsberg, Concentration-dependent diffusivity and anomalous diffusion: A magnetic resonance imaging study of water ingress in porous zeolite, Phys. Rev. E 73, 011204 (2006)[4] G. Løvoll, B. Sandnes, Y. Méheust, K.J. Måløy, J.O. Fossum, G.J. da Silva, M.S.P. Mundim, R. Droppa Jr., D.d.M. Fonseca, Dynamics of water intercalation fronts in a nano-layered synthetic silicate: A synchrotron X-ray scattering study, Physica B: Condensed Matter, 370, 90-98 (2005)[5] G.J. da Silva, J.O. Fossum, E. DiMasi, K.J. Måløy, S.B. Lutnæs, Synchrotron x-ray scattering studies of water intercalation in a layered synthetic silicate, Phys. Rev. E 66, 011303 (2002) [6] G.J. da Silva, J.O. Fossum, E. DiMasi, K.J. Måløy, Hydration transitions in a nanolayered synthetic silicate: A synchrotron x-ray scattering study, Phys. Rev. B 67, 094114 (2003)
11:15 AM - V4.5
Investigation of Interfacial Water in Octahedral Molecular Sieve Pores.
Tina Nenoff 1 , Nathan Ockwig 2 , Randall Cygan 2 , Todd Alam 3 , Hongwu Xu 4 , Monica Hartl 4 , Luke Daemen 4 , Kevin Leung 1
1 Surface & Interface Sciences, Sandia National Labs, Albuquerque, New Mexico, United States, 2 Geochemistry, Sandia National Labs, Albuquerque, New Mexico, United States, 3 Electronic & Nanostructured Materials, Sandia National Labs, Albuquerque, New Mexico, United States, 4 LANSCE, Los Alamos National Lab, Los Alamos, New Mexico, United States
Show AbstractZeolites and microporous materials are important materials for water purification, in particular for radioactive cations and heavy metals. Sandia Octahedral Molecular Sieves (SOMS), Na2Nb1.6Ti0.4O5.6(OH)0.4-H2O, exhibit a high selectivity for divalent cations. It is orders of magnitude better in selectivity than the sieves’ end member Na2Nb2O6-H2O. Our research is focused on understanding the effect of the confined water on the ion selectivity in SOMS.Characterization methods include inelastic neutron scattering (INS), MAS NMR, crystallographic structure refinement, and modeling/simulation. INS and NMR data indicate that the water in Na2Nb1.6Ti0.4O5.6(OH)0.4-H2O is rotationally free, highly-mobile and bulk-like water species. The occluded water in Na2Nb2O6-H2O behaves Ice-like. MD and DFT calculations of Na2Nb1.6Ti0.4O5.6(OH)0.4-H2O supports the INS and NMR data of rotationally free waters in energetically favorable locations near the framework atoms. The correlation between structure and property of the materials studied will be discussed. Sandia is a multiprogram laboratory operated by Sandia Corporation, Lockheed Martin Company, for US DOE’s NNSA, Contract DE-AC04-94-AL85000.
11:30 AM - V4.6
Nanoconfined Water Dynamics in Clinoptilolite and Heulandite Microporous Zeolites.
Nathan Ockwig 1 , Randall Cygan 1 , Tina Nenoff 2 , Luc Daemen 3 , Monika Hartl 3 , Louise Criscenti 1
1 Geochemistry, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Surface and Interface Sciences, Sandia National Laboratories, Albuquerque, New Mexico, United States, 3 Manuel Lujan Jr. Neutron Scattering Center LANSCE-LC, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractOur research is focused on understanding the dynamic behavior of nanoconfined water in the HEU class of aluminosilicate zeolites. We are specifically examining the impacts of Si/Al framework substitution and cation identity through correlation of classical molecular dynamics (MD) data and experimental data. With a generalized formula of [Ca,Na,K]4-6[Al6(Al,Si)4Si26O72 * 24H2O the isostructural minerals heulandite (HEU) and clinoptilolite (CLI) are generally considered the most abundant naturally-occurring zeolites. They possess an underlying HEU topology and can be synthesized over a range of Si/Al values (from 2.5 to 6) with a wide variety of charge-compensating cations. The distinction between these two phases is based on both their Si/Al ratios and thermal stabilities. Abundant deposits of clinoptilolite have fueled interests in commercial applications in gas separations, ion exchange, agriculture, and waste water remediation. Understanding the behavior of confined species and their impact on macroscopic properties is a challenging topic in microporous materials which spans a wide range of experimental and theoretical efforts. Water is arguably one of the most important nanoconfined species because of its ubiquitous nature and significance is many geologic and industrial processes. The structural and dynamical properties of bulk water are well understood over a wide range of conditions. It is also well known that these properties are significantly modified when water is confined on a molecular level. Despite the relatively simple molecular structure, the complex cooperative behavior of confined water remains a major challenge for current scientific research. Quantifying the dynamical behavior of water in confining systems such as zeolites is the first step towards understanding its role in macroscopic phenomena. Large-scale MD simulations are used to derive equilibrium structures, enthalpies, and dynamical behavior. Power spectra derived from atomic trajectories provide a theoretical basis for interpretation of INS. The combined theoretical and experimental approach allows a determination of the role that hydrogen bonding, charge density, and steric effects have on water confined in the zeolite phases, and evaluate which factors are the most influential.Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
11:45 AM - **V4.7
Characteristic Lifetimes of Charge Carriers and of Adsorption / Desorption in Heterogeneous Photocatalytic Water Treatment. Implications and the Development of Mesoporous Anatase as an Alternative to Conventional Catalysts.
Miguel Blesa 1 2 , Paula Araujo 2 1 , Galo Soler-Illia 1
1 Department of Chemistry, Comision Nacional de Energia Atomica, San Martin, Buenos Aires Argentina, 2 Escuela de Posgrado, Universidad nacional de General San Martin, San Martin, Buenos Aires Argentina
Show AbstractHeterogeneous Photocatalysis (HP) is one of the Advanced Oxidation Techniques (AOTs) currently being explored to decontaminate water. HP is based essentially on the properties of anatase, pure or mixed with rutile, or doped with various metals. Successful processes require intimate and extensive interaction between the catalyst and the organic pollutant, and good photoactivity. This latter factor depends on the trapping of holes in the surface to generate species leading to the oxidation of the organic molecule. The lifetime of the charge carriers is short, and, as shall be shown, may be even shorter in the presence of the pollutant. Hence, individual nanoparticles of catalyst are most of the time inactive (except immediately after a photon is absorbed). A further limitation arises in solar heterogeneous photocatalysis that depend on the availability of sunlight. On the other hand, characteristic times for adsorption / desorption are much longer: some examples shall be shown. As a way to advance to a new generation of catalysts, mesoporous anatase has been synthesized, characterized and used in trial tests to demonstrate its ability to act as a heterogeneous photocatalyst for removal of model organic pollutants. Synthesis was carried out in a tubular furnace bottom-fed with TiCl4 and water, in the presence of a texturant agent. Mesoporous amorphous titanium dioxide was trapped at the column exit, and thermally treated (TT) to obtain crystalline anatase. The product was characterized by XRD, SAD, Dark Field Microscopy, SEM, TEM and porosimetry. Meso- and micropores were found, the size of which change with TT. Photoactivity was measured using gallic acid as a model pollutant. The new concept permits to explore the possibility to separate the stages of pollutant fixation (adsorption, sorption) and pollutant mineralization. This feature is a notorious asset in attempts to develop solar photocatalytic reactors.
12:15 PM - V4.8
Rapid Hydrolysis of Pesticides in the Presence of Nanostructured Titania Particles Derived from Diatom Frustules.
Samuel Shian 1 , Seung-Jin Lee 2 , Ching-Hua Huang 2 , Kenneth Sandhage 1
1 MSE, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractIn this work, we demonstrate that three-dimensional (3-D) anatase-based particles, possessing open nanoporous structures inherited from diatom frustules, exhibit enhanced non-photocatalytic activity for the hydrolysis of widely-used water soluble pesticides. Diatoms are aquatic unicellular algae that form rigid cell walls (frustules) comprised of intricate, porous, 3-D networks of amorphous silica nanoparticles. Although a wide variety of frustule morphologies exists among the tens of thousands of diatom species, the reproduction of any given species yields the same frustule shape with a high degree of fidelity. Hence, a large number of open silica nanoparticle structures of identical shape may be generated by the sustained reproduction of a particular diatom species. The reproducible, porous morphology of diatom frustules led us to consider the conversion of such bioclastic structures into nanocrystalline titania for applications in environmental remediation. Using a shape-preserving metathetic reaction-based process, silica-based diatom frustules were chemically converted into nanocrystalline anatase-based replicas at ≤350°C. In the absence of light and over a pH range of 4.5-7.9, these diatom-derived titania nanostructures exhibited significantly enhanced activity, relative to commercial P25 and NAM titania nanoparticles, for the hydrolysis of methyl parathion and methyl paraoxon (insecticides widely used for crop and fruit production). Such activity, in the absence of a strong UV light source, is quite attractive for the hydrolytic destruction of organophosphorus ester-based pesticides in remote locations. The chemical conversion process used in this study is a scalable means of converting large quantities of diatom frustules into porous, nanostructured anatase assemblies.
12:30 PM - V4.9
Doped Metaloxide Nanoparticles for Water Purification.
Clemens Burda 1 , Xiaofeng Qiu 1 , Yang Liu 2 , Jin Li 2
1 Chemistry, Case Western Reserve University, Cleveland, Ohio, United States, 2 Civil Engineering and Mechanics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, United States
Show Abstract12:45 PM - V4.10
Development of Bimetallic Catalysts for Nitrate Removal from Drinking Water.
Judith Yang 1 , Long Li 1 , Kathryn Guy 2 , Huiping Xu 1 , Mhairi Gass 4 , Crispin Hetherington 5 , Andrew Bleloch 4 , John Shapley 2 , Charlie Werth 3
1 Mechanical Eng. & Materials Sci., University of Pitttsburgh, Pittsburgh, Pennsylvania, United States, 2 Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 UK SuperSTEM Laboratory, Daresbury Laboratory, Daresbury United Kingdom, 5 Materials, Oxford University, Oxford United Kingdom, 3 Civil & Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractV5: Disinfection and Adsorbents
Session Chairs
Wednesday PM, November 28, 2007
Room 308 (Hynes)
2:30 PM - V5.1
Water Disinfection Using Semiconductor Deep Ultraviolet Light-Emitting Diodes.
Olga Bilenko 1 , Yuri Bilenko 1 , Igor Shturm 1 , Alex Lunev 1 , Maxim Shatalov 1 , Jianping Zhang 1 , Michael Shur 1 , Remis Gaska 1
1 , Sensor Electronic Technology, Inc., Columbia, South Carolina, United States
Show AbstractUltraviolet (UV) light water disinfection technology is a widely used alternative to more traditional chemical processes, which often create substantial amounts of disinfection by-products and require temperature and pH control for effective disinfection. Current UV-based purification/disinfection systems rely on low and medium pressure mercury (Hg) containing lamps that emit either monochromatic 254 nm radiation or polychromatic radiation ranging from 220 nm to 370 nm, respectively. In contrast to bulky, fragile and hazardous mercury lamps, deep ultraviolet (DUV) light emitting diodes (LEDs) are environmentally safe, easily reconfigurable, compact, robust, and inexpensive. They can be easily powered by low-voltage sources such as batteries or solar panels. Moreover, the spectral power distribution of DUV LED-based lamps can be controlled by appropriate electronics, enabling new applications in water, air and food disinfection as well as in medical diagnostics and treatment.We used for water disinfection multiple quantum well AlGaN DUV LEDs grown on sapphire substrates using our proprietary MEMOCVD® technology. UVTOP® devices consisted of LED chips that were fabricated in-house using standard semiconductor processing technology and packaged on TO-type vacuum sealed headers. The arrays of LEDs with single and multiple emission peaks were incorporated into customized water disinfection modules for germicidal experiments under DUV LED emission tuned from 250 nm to 340 nm.Test microorganisms, Escherichia coli (ATCC 11303) bacteria, were obtained from American Type Culture Collection. After activation and incubation, the bacteria suspension was diluted into different concentrations with PBS Buffer or sterile water and subjected to UV light exposure. After irradiation with DUV LED and incubation for 18-22 hours the enumeration of the bacteria as Colony Forming Units (CFU) was done by Colilert-18 method. Reduction of bacteria concentration in water was expressed as log (Nb/Na), where Nb and Na are the concentrations of viable organisms before and after irradiation, respectively.For the germicidal experiments, LED devices were submerged into water (sample of 200 ml or more) and, therefore, UV dosage normalized to the volume of water was calculated. Maximum germicidal efficiency was obtained for LEDs emitting at 275-280 nm, which is associated with the optimum combination of transmittance spectrum of water and absorption spectra of DNA and proteins. Log reduction of bacteria concentration varied linearly with UV dosage, with 6 Log reduction (99.9999%) obtained at dose of 9 mJ/ml. Finally, bacteria inactivation in flowing water reactor was demonstrated using 280 nm DUV LED. The reduction of 96.3% was obtained for the water flow rate of ~0.1 GPM with the input power consumption of only 2.4 W. These experiments demonstrate great potential of DUV LED technology for environmentally safe point-of-use UV water disinfection.
2:45 PM - V5.2
Material Challenges for the Economical Encapsulation of Deep UV Light Emitting Diodes for In-flow Water Sterilisation.
Allan Mackintosh 1 , Richard Pethrick 1 , Alexander Kuhne 1 , Martin Dawson 2 , Erdan Gu 2
1 Pure and Applied Chemistry, University of Strathclyde, Glasgow, Scotland, United Kingdom, 2 institute of photonics, University of Strathclyde, Glasogow United Kingdom
Show AbstractWater purification is one of the key issues of our time. In developing countries access to water purification facilities or distribution of chemical sterilisation agents is logistically problematic. Also, times of natural disaster contamination of water supplies can kill more people than the event itself. Deep ultra violet, DUV, 250-300nm, is known to be remarkably efficient in killing water born microbial or parasitic diseases. However, traditional sources such as mercury bulbs are undesirable, as they are prone to mechanical damage, energy inefficient, have limited flexibility in device design and the disposal of such sources is environmentally hazardous. Recently the commercialisation of DUV solid-state light emitting diodes, LEDs, opens up exciting new possibilities in water sterilisation. The use of such devices could yield highly efficient solid-state sources as water purification gates or flow chambers. The greatest contributing factor in the development has been the availability of low defect AlGaInN materials as active optical elements pioneered at the University of Southern Carolina and Kansas State. The packaging of the LED devices is complicated as most polymer materials are opaque in this region of the spectrum. The commercially available devices are currently packaged in TO cans with a sapphire or quartz window. This limits the applicability of such devices in water purification on the grounds of cost. Here we present a novel photo curable polymer, which has excellent transmission in the DUV. Several material requirements have been addressed such as the coefficient of thermal expansion, mechanical properties, barrier properties and surface modification to prevent fouling of the device. The material properties are achieved through a combination of surface treatment and inclusion of nano-composites.
3:00 PM - **V5.3
Clean Water from Small Materials: Nanotechnology in the Environment.
Vicki Colvin 1
1 Center for Biological and Environmental Nanotechnology, Rice University, Houston, Texas, United States
Show AbstractNanotechnology-enabled systems offer much promise for solving difficult environmental problems. This talk will focus on using nanotechnology to meet the challenge of providing clean and safe water to the world’s citizens. In the first example, the nanoscale behavior of magnets are the basis for developing point-of-use water purification for arsenic-rich sources. High surface area and monodisperse Fe3O4 nanocrystals will move in very low magnetic field gradients (< 100 T/m) in a size-dependent fashion. The striking size dependence of the magnetic separation process permits the first multiplexed separation of nanocrystals by magnetic field strength. We believe these nanocrystals are not acting independently in the separation, but rather reversibly aggregate due to their nanoscale size and the resulting high field gradients present at their surfaces. This phenomena makes it possible to use high specific surface area Fe3O4 nanocrystals in a magnetic separation process designed to remove arsenic. It is also possible to use nanoscale materials to destroy organic contaminants in water; in our work, we demonstrate the use of C60 for such a purpose. In water, we form a colloidal form of crystallized C60 which contains a porous and hydrophobic interior which can sequester organic contaminants. These particles act as a ‘trap and treat’ site for organics, and under ultraviolet illumination can photo-oxidize model dyes with rates comparable to commercial nano-TiO2 photocatalysts. Finally, we show how studies of the biological properties of both systems are essential for developing their applications in environmental technology. Characterization of the differential toxicology of these materials permits a correlation between nanoscale structure and biological impact to be discerned. Armed with this information, we can propose ways to design nanoenabled technologies that are ‘safe by design’.
3:30 PM - V5.4
New Concept to Remove Heavy Metals from Liquid Waste Based on Electrochemical pH-switchable Immobilized Ligands.
Pascal Viel 1 , Antoine Sorin 1 , Laetitia Dubois 1 , Serge Palacin 1
1 Chemistry of Surfaces and Interfaces, CEA, Gif sur Yvette France
Show AbstractHeavy metal pollution has become an environmental problem throughout the world because heavy metals can be accumulated into the food chain and cause serious problems, not only for ecosystems but also for human health. The selective removal of industrial heavy metals from liquid waste is consequently the subject of considerable ecological and economic interest. The keys to preventing pollution in printed circuit board manufacturing, in the decoration of plastics and chemical rotogravure printing are to minimize chemical drag out, minimize the amount of water used for rinsing, and for recovery, reuse, and recycle of copper, zinc, nickel or palladium for must current. There is indeed an obvious need for clean and low cost processes able to lower the copper concentration down to one decade below the current legal threshold.Conventionally, wastewater streams are treated by chemical means and the quality of treated effluents must meet discharge standards. With concentrated heavy metal wastewater, low cost physico-chemical techniques involve precipitation of heavy metals. When traditional techniques do not reach regulation standards, completion treatments are carried out with chelating or ion exchange resins. In general, waste management becomes more difficult and more expensive as feed concentration in the waste stream decrease and for these reasons, the reuse of the extraction materials and the minimization of secondary waste volume must become the focus of scientific efforts.To limit and ideally to avoid the use of any chemical reagents at the expulsion (or regeneration) stage of the depolluting process we propose an alternative solution based on a « surface strategy » through adsorption phenomena and electrical control of the expulsion stage. Heavy metal ions were captured on active filters composed by a conducting surface covered by poly-4-vinylpyridine (P4VP) or Polyacrylic acid (PAA). Due to respectively pyridine and carboxylate groups those polymer films have chelating properties for heavy metals. Our strategy for electrical triggering of the heavy metals expulsion in aqueous medium is based on pH sensitive chelating groups. Applying moderate electro-oxidizing conditions on the conducting substrate generates acidic conditions in the vicinity of the electrode i.e. “inside” the polymer film. This allows a “switch-off” of the complexing properties of the film from the basic and complexing form of pyridine or carboxylate groups to non-complexing pyridinium or carboxylic groups. By maintaining the electro-oxidizing conditions a an "acidic wave" propagates from the electrode to the outside medium through the thickness of the film, pushing the heavy metal ions out. Interestingly, no buffer washing is necessary to restore (or “switch-on”) the complexing properties of the polymer film because the pH of the external medium is left unchanged by the electrochemical effect that affects only the vicinity of the electrode.
3:45 PM - V5.5
Water Purification Using Magnetic γ-Polyglutamic Acid.
Mikito Yasuzawa 1 , Kazuki Matsumoto 1 , Hideya Okada 2 , Makoto Ichihashi 2
1 Department of Chemical Science and Technology, The University of Tokushima , Tokushima Japan, 2 , Nippon Poly-Glu Co., Ltd, Osaka Japan
Show Abstractγ-Polyglutamic Acid (PGA) is a water soluble biodegradable polyamide, which is known as the sticky paste formed on the surface of fermented soybeans "Natto". It is also non toxic towards humans and the environment. Some of the authors have successfully applied PGA as the flocculants (absorbents) for water purification of rivers and ponds. Although, PGA flocculant is biodegradable, the removal of flocculants with impurities were essential. Therefore, filtration, which is time and energy consuming process, was required in the water purification system. The elimination of filtration process will significantly speed up the opeartion and simplify the system. In this study, magnetite was immobilized to PGA in order to introduce magnetic function to the flocculant. Properties of magnetite attached PGA were investigated. The water purification experiment was performed using pond water. Flocculants combined with impurities were immediately collected when the magnet was inserted in the vessel. Clear colorless water was able to obtain without filtration process.
4:00 PM - V5: Adsorbents
BREAK
4:30 PM - V5.6
Alumina Supported Iron Oxide Ceramic Tubes for Arsenic Abatement.
Paola Sabatini 1 , Federico Rossi 1 2 , Adolfo Marajovsky 2 , Maria Fidalgo de Cortalezzi 1
1 Chemical Engineering, ITBA, Buenos Aires Argentina, 2 , CNEA, Buenos Aires Argentina
Show AbstractGood drinking water sources have proven to be scarce, while an important number of people rely on low quality sources for their water consumption. For example, groundwater is many times contaminated with trace elements that are very toxic even in those low concentration levels. An example of this problem is the natural presence of arsenic, which is a public health issue in many countries in Latin America. In addition, high arsenic levels have been detected in rural and remote areas, many times affecting very low-income population. Thus, an easy to use, low energy demanding and economical treatment technology is needed to address this problem. We have developed cross flow ceramic adsorbers for arsenic abatement. The system can be operated with minimal trans membrane pressure difference and does not require pumping. Iron oxide nanoparticles have been deposited on porous alumina ceramic tubes to fabricate the adsorbers. The support tubes and final membrane have been characterized by surface area and porosity measurements, permeability and SEM imaging. The chemistry of the adsorption process has been investigated by EXAFS. The ceramic adsorbers were applied to the removal of arsenic from both synthetic solutions prepared in the laboratory and natural waters, to study the influence of the water matrix in the removal of arsenic. Arsenic concentrations were determined by an atomic absorption spectrometer and validated by neutron activation analysis. The process is effective in the removal of arsenic without the generation of liquid or sludge wastes, and being low cost and easy to use in remote areas may provide a valuable solution to the groundwater quality issue in Latin America.
4:45 PM - V5.7
Functionalization of Nanoporous and Nanoparticulate Materials for Removal of Contaminates in Water.
R. Shane Addleman 1 , Robert Wiacek 1 , Glen E. Fryxell 1 , J. Timothy Bays 1 , Joseph Davidson 1 , Wassana Yantasee 1 , Thanapon Sangvanich 1 , Cynthia Warner, 1 , Marvin Warner 1
1 , Pacific Northwest National Laboratory, Richland, Washington, United States
Show AbstractNanostructured materials, such as iron oxide (Fe3O4) nanoparticles and mesoporous silica have high relative surface areas resulting in structures with large potential capacities as sorbents for toxic materials. However, without selective modification of their surface chemistry these materials have limited chemical selectivity and affinity for most contaminates of concern. We present various surface chemistries utilized to functionalize these materials for the removal of heavy metals and radionuclides from water. The capabilities and limitations associated with these functionalized nanostructures for capture of trace level of heavy metals and radionuclides will be presented. The chemical affinity, capacity, kinetics and stability of the functionalized nanomaterials will be compared to those of conventional resin based sorbents and activated activated carbon.
5:00 PM - V5.8
Removal of Synthetic Organic Compounds (SOCs) by Carbon Nanotubes (CNTs).
Hyung-Nam Lim 1 , James Kilduff 1
1 C&EE, Rensselaer Polytechnic Inst, Troy, New York, United States
Show AbstractCarbon nanotubes (CNTs) offer several potential advantages over the existing state of the art adsorbents, activated carbons and carbon fibers: 1) their surfaces are inherently more hydrophobic, which exploits entropic free energy of organic compound adsorption; 2) their electronic structure is favorable for supporting pi-pi interactions with double-bonded carbon atoms, including aromatic structures; and, 3) when endcaps/sidewalls are opened via etching, sorption surfaces are located in micropores. In this research we compare 1) the uptake of different organic compounds having similar structure but differing in pi-electron density to elucidate any selectivity induced by the presence of such electrons; 2) the uptake of representative synthetic organic contaminants (SOCs) by closed- and open-ended (etched) CNTs and activated carbons (ACs); 3) evaluate the impact of competition from NOM (Natural Organic Matter).Commercially available CNTs were used as-produced or after pretreatments using heat (e.g., oxidation or annealing), acid reflux, and ozone (O3) / hydrogen peroxide (H2O2). These materials were evaluated as adsorbents for removing a broad range of SOCs from water. Organic chemicals were selected based on their relevance as environmental contaminants, and their physicochemical properties. This research will identify mechanisms of liquid phase adsorption by CNTs for a representative selection of SOCs. This research will provide a side-by-side comparison with existing adsorbents (e.g., GACs) and will provide a rational basis for selecting and preparing CNTs. This research will evaluate recent developments in nanotechnology for applications in water treatment, and will form the beginning of a database of sorption properties.
5:15 PM - V5.9
A Single-Walled Carbon Nanotube Hybrid Filter for Removal of Microbial Contaminants.
Anna Stirgwolt Brady-Estevez 1 , Seoktae Kang 1 , Menachem Elimelech 1
1 Chem./Env. Engineering, Yale University, New Haven, Connecticut, United States
Show AbstractCarbon nanotubes (CNTs) are known for their high surface areas, exceptional strength properties, extreme thermal stability, and other novel characteristics. Previous research has also indicated that CNTs might be affective in inactivating microbial pathogens. Our work studies the development of a CNT-hybrid filter by incorporating a thin CNT layer on various microporous base filters. The thin CNT layer on the filter surface is effective in filtering 100%, and inactivating more than 80% of bacteria (E. coli) deposited on the filter, suggesting an ability to eliminate or reduce biofouling of the filter. Viral removal experiments using the CNT layer of the hybrid as a depth filter have also been performed, demonstrating removal of up to the range of 5-7 log removal of the MS-2 virus applied to the filter. The development of a CNT-hybrid filter shows promise in several drinking water applications. It could provide bacterial inactivation, and viral removal at gravity-driven or low pressures.