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U.S.-Israel Workshop on Nanotechnology for Water Purification
10 U.S.-Israel Workshop on Nanotechnology for Water Purification Richard C. Sustich Center of Advanced Materials for Puri facation of Water with Systems, University of Illinois at Urbana-Champaign, Urbana, I L , U S A
Introduction 10.1.1 Workshop Objectives 10.2 Technical Presentations 10.2.1 Contaminant Detection and Sensing 10.2.2 Membrane Synthesis and Membrane Processes 10.2.3 Contaminant Reduction and/or Removal 10.2.4 Biofouling and Disinfection 10.2.5 Water Security and Infrastructure Resilience 10.3 Gap Analysis and Future Research Needs 10.3.1 Membrane Synthesis and Membrane Processes 10.3.2 Biofouling and Disinfection .10.3.3 Contaminant Removal 10.3.4 Sensors 10.4 Collaborative Research Projects 10.1
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Abstract In March 2006, the Center of Advanced Materials for Purification of Water with Systems (WaterCAMPWS), a National Science Foundation Science and Technology Center, and the Israel National Nanotechnology Initiative (INNI) convened an international workshop to assess nanotechnology opportunities for water purification. This chapter summarizes the state of research presented at the workshop and the participants’ assessment of future nanotechnology research needs for water purification, and describes 12 joint international research projects identified by the researchers in the areas of (a) membrane synthesis and processes, (b) biofouling and disinfection, (c) contaminant removal, and (d) environmental monitoring and scnsor developrnent and application.
Savage et al. (eds.), N m o t e c h n o l o ~Applications foT C l e m I.Vatc.1, 131-1-10, 0 2009 William Andrew Inc.
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10.1 Introduction The 2006 joint United States - Israel Nanotechnology for Water Purification workshop brought together more than 50 researchers and included 20 technical presentations and breakout discussions focused on identifying knowledge gaps and future nanotechnology research needs for water purification.
10.1.1 Workshop Objectives The workshop was organized around the following objectives:
1. To assess the current state of nanotechnology applications for water purification through presentation of current research in the areas of (a) desalination and water reclamation/reuse, (b) detection and removal of trace contaminants of concern, and (c) disinfection for human consumption. 2. To identify gaps in (a) the scientific. understanding and characterization of materials and aqueous interactions at the nanoscale, (b) the ability to synthesize nanomaterials and systems with specific, desirable characteristics, (c) the understanding and minimization of fouling in nanotechnology applications in the aqueous environment. 3 . To identify current and future opportunities for nanotechnology to enhance the resilience of existing water purification and distribution infrastructure to natural and anthropogenic catastrophes, including acts of terrorism. 4. To assess and prioritize the identified gaps (point 2) and opportunities (point 3 ) according to their relative impact on potential progress in water purification. 5. To inventory the capabilities of workshop participants to address identified gaps and opportunities. 6. To identify and initiate partnership opportunities among participants to effectively address the gaps and opportunities.
10.2
Technical Presentations
Workshop participants gave 19 technical presentations representing the current state of nanotechnology research in the United States and Israel, organized under the following themes:
10.2.1 Contaminant Detection and Sensing Shimshon Belkin, Hebrew University of Jerusalem, Israel, reported on the development of whole cell biosensors, genetically selected microbial cells with
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high sensitivity to specific toxicants; cell immobilization platforms and signal transduction strategies; and the ticsign of a “toxicity analyzer” [l].Yi Lu, University of Illinois at Urbana- Champaign, United States, described low parts per billion sensors for a variety of metal and organic contaminants based on combinatorial in vitro selection of highly selective catalytic DNA, and both fluorescent and colorimetric signaling for laboratory and field applications [a]. Robert Marks, Ben-Gurion University of the Negrev, Israel, described a conceptual model for a “Lab-in-a-Pen” incorporating chemilumiriescent fiberoptic immunosensors for hepatitis C, West Nile and Ebola viruses, cholera and ovarian cancer using silane or electropolymerization on Indium-tin-oxide (IT0)-coated fiber optics; bioluminescent fiber-optic whole-cell biosensors for gentoxicants, heavy metals and endocrine disruptors; and a chcmiluminescent phagocyte-based sensor [ 3 ] . Israel Schechter, Technion-Israel Institute of Technology (IIT), Israel, discussed the application of laser-induced breakdown spectroscopy, polymeric film sensors coupled to fluorescence fluctuation spectroscopy for dissolved and particulate sampling and analysis [4].Finally, Michael Strano, University of Illinois at Urbana-Champaign, United States, described the synthesis and demonstration of several solution-phase, nearinfrared sensors based on functionalized single-walled carbon nanotubes [5].
10.2.2 Membrane Synthesis and Membrane Processes Yoram Cohen, university of California at Los Angeles, United States, described the application of tethered polymer-modified (TPM) surfaces to create selective pervaporation membranes and fouling-resistant nanofiltrationl ultrafiltration membranes [6]. Ovadia Lev, Hebrew University of Jerusalem, Israel, described development of two nanoscale probes, fluorescent-labeled MS2 bacteriophages and gold nanoparticles, for direct , online evaluation of membrane pore-size integrity [7]. Charles Linder, Ben-Gurion University, Israel, detailed advances in developing chemically stable nanofiltration membranes for tertiary wastewater applications [8].Anne Mayes, Massachusetts Institute of Technology, Unitcd States, described development of self-assembling, anti-fouling polymer filtration membranes incorporating amphiphilic graft copolymers exhibiting improved flux retention [9]. Finally, Yoram Oren, Ben-Gurion Univcrsity, Israel, described preparation of highly oriented heterogeneous electrodialysis membranes by exposing resin particles, non-conductive liquid polymer precursor, and a cross-linker to low-frequency alternating current during membrane curing, resulting in membranes exhibiting >lo0 greater conductivity than conventional, non-oriented membranes [lo].
10.2.3 Contaminant Reduction and/or Removal Charles Werth, University of Illinois at Urbana-Champaign, United States, evaluated an alumina-supported, palladium-copper bimetallic catalyst for
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nitrate reduction for drinking water applications arid discussed fouling impacts from a variety of natural groundwater constituents [ll]. Miron Landau, Ben-Gurion University of the Negev, Israel, described the nanocasting of manganese-cerium oxide catalysts using ordcred mesoporous silica as a removable casting matrix and their applicability for catalytic wet oxidation of organic constituents in industrial wastewaters [12]. Thomas Mayer, Sandia National Laboratories, United States, described the desalination research and arsenic removal research programs of the United States Department of Energy and federal laboratories [13]. Finally, Moshe Sheintuch, Technion-IIT, Israel, reported assembly of a continuous process catalytic reactor for nitrate reduction incorporating bimetallic palladium-copper catalysts on activated carbon cloth support structure, which compared favorably to silica-supported catalysts [14].
10.2.4 Biofouling and Disinfection Carlos Doesertz, Technion-IIT, Israel, discussed the processes of biofilm formation and attachment [15]. Menachem Elimelcch, Yale University, United States, reported on the role of foulant-foulant intermolecular adhesion forces in reverse osmosis membrane fouling and the correlation of elevated calcium and alginate levels to fouling severity [16]. Ovadia Lev, Hebrew University of Jerusalem, Israel, described the current process-specification approach and application of engineering indicators in assuring adequate drinking water disinfection, and the challenges to assuring public safety using emerging disinfection technologies such as ozone [17]. Lastly, Jian-Ku Shang, University of Illinois at Urbana-Champaign, reported the synthesis of quaternary titanium oxide nanoparticles exhibiting disinfection capabilities under visible, as opposed to ultraviolet, light [18].
10.2.5 Water Security and Infrastructure Resilience Michael Royer, U.S. Environmental Protection Agency, described the Agency’s Watersentiriel Initiative to design and demonstrate a pilot contarninarit detection system and response protocol for drinking water utilities that incorporates real-time distribution system water quality monitoring; intensive sampling and analysis for high-priority chemical, biological, and radiological contaminants; integration of water system data with existing public health surveillance systems; and robust customer complaint assessment [ 191.
10.3 Gap Analysis and Future Research Needs Workshop attendees participated in a series of focused discussion sessions to assess current scientific knowledge gaps and identify future research needs for key areas of water purification science and technology.
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10.3.1 Membrane Synthesis and Membrane Processes Minimization of membrane fouling and preservation of membrane functionality by appropriate feed pretreatment to remove nanoparticles and foulants (organic, inorganic, and biological) are essential for successful operation of water treatment, reclamation, and desalination technologies. Research opportunities include enhanced feed characterization (suspended particle composition and morphology, particle-particle and particleesolute interactions) ; biofilm and scale formation (impact of feed water constituents, surface charge, chemistry, particleesurface effects on attachment and growth, role of suspended nanoparticles in scale formation) and mitigation strategies (selective separation of critical precursors, chemical and biological demineralizatiori mechanisms); active anti-fouling membranes incorporating functionalized surfacc and pore nanocatalysts; nanobased, fast-response monitors for feed water quality monitoring and membrane performance/integrity assessment. Development of new, substantially more robust membranes will be dependent on increased Understanding and capabilities in characterizing materials and aqueous interactions at the nanoscale. Areas of critical interest include nanostructure-membrane performance relationships; nanostructure impacts on membrane selectivity, transport, and membrane chemical and mechanical stability; multiscale computation methods for assessing material interactions (particleeparticle, particleesolute, particleesurface, solute-surface) on water and ion transport in confined spaces; casting methodologies for uniform scale-up from nanostructures to commercially relevant membranes. Residuals management plays a significant role in membrane performance and residuals management is a major operational cost in membrane-based purification systems. Substantive advances in residuals minimization and treatment of critical contaminants will require better Understanding of the role of nanoparticlcs and their structure on crystallization, more robust modeling of crystal growth and characterization of crystallites, enhanced understanding of the role and mechanisms of antiscalants in growth control, and methodologies to stabilize supersaturated solutions without precipitation or scale formation.
10.3.2
Biofouling and Disinfection
Controlling the growth of biological organisms and the formation of biofilms is critical both to sustainable operation of water purification systems and to the prevention of disease. Key research opportunities identified by workshop participants in understanding the causes and minimization of biofouling and the deactivation of pathogens include the stimuli and processes responsible for the formation of the initial biofilm layers, strategies for inhibiting initial biofilm formation; surface design and characteristics (e.g., catalytically active moieties) that are resistant to biological attachment, including structural components (e.g., membrane spacers); surface and system design and characteristics that increase shear to minimize cellular attachment; effect of polarization
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layers on biofilm attachment and growth; methods to detect onset of biofilm formation; adhesion mechanisnis for antimicrobial materials on membranes and structural surfaces; strategies and niechanisms for disruption and detachment of biofilms (e.g., acid catalysis, enzymes, biosignal substances); formation pathways, characterization and toxicity of disinfection byproducts; characterization of titania, titania-alumina, and other mixed-metallic oxidative catalysts as altcrnative antiniicrobial agents, and methods for photocatalytic viral deactivation. Point-of-use design for distributed supply systenis, wetweather (e.g., stormwater, combined sewer overflow, sanitary sewer overflow) discharges, and disaster recovery applications were also identified a s critical research areas for successful nanotechnology diffusion.
10.3.3 Contaminant Removal Advances beyond current strategies for removal of critical contaminants or for transformation of critical contaminants to nontoxic forms will require enhanced understanding of molecular transformations, rianostructured systems, and material synthesis, including better understanding of the relationship between nanocatalyst structure and oxidation-reduction pathways for target contaminants, and react ion site competition among contaminant mixtures. Fast computational models are needed to evaluate new catalysis candidates. New surface characterization techniques, for example, spectroscopically active adsorbent probes to characterize surface composition and new cornputation tools to interpret surface characterization will also be essential for improved nanocatalyst synthesis. Lastly, improvements in controlled synthesis of hierarchical nanostructured mixed-metal oxide catalysts, for example, Coo-TiO, and Pd-Cu/C, are warranted for application in tricking-bed and fixed-bed heterogeneous react or systems.
10.3.4 Sensors The ability to sense a wide range of environmental and system conditions, and to detect select contaminants with high specificity and sensitivity is emerging as one of the most critical aspects for the efficient and effective operation of water purification technologies, for extending the useful lifetimes of water and wastewater infrastructure assets, and for protecting the public and infrastructure assets from natural and anthropogenic threats. A number of nanoscale sensor approaches were identified for further research and potential development, including combinatorial selection of aptamers for sensing presence of biofilins cells; solid-phase, polymer-film extraction/laser-inducedfluorescence for capture and detection of polycyclic aromatic hydrocarbons; impedirnetric and colorimetric sensors incorporating hormonal and other binding receptors in synthetic lipid bilayer membranes for detection of endocrine disruptors; impedimetric sensors embedded directly into treatment membranes and on pipe surfaces for detection of biofilm formation.
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10.4 Collaborative Research Projects The most significant outcome of the workshop was the identification of a series of 12 international collaborative projects directed at practical applications of nanotechnology for improving water quality. Four of these projects (Table 10.1) were selected for priority funding based on their perceived benefits to water purification and their potential for commercial development within the next five years. Independent work toward these projects continues in both the United States and Israel while conference organizers in both countries solicit funding to facilitate a second workshop in 2009 or 2010. Further information regarding the workshop, full abstracts of the technical presentations, and descriptions of the 12 joint research projects established during the workshop can be found at the website http://www.watercampws. uiuc.edu/ index. php? menu-i t em 'id= 114.
T a b l e 10.1 Projects Selected for P r i o r i t y F u n d i n g at the U S - I s r a e l W o r k s h o p o n Nanotechnology for Water Purification 1. Novel polymer morphologies for u n i q u e m e m b r a n e selectivity
United States Ann Mayes, Toyota Professor of Materials Science and Engineering, Massachusetts Institute of Technology Charles Werth, Civil and Environmental Engineering Department, University of llinois at Urbana-Champaign (UIUC) I,57d Moris S. Eisen, Professor, Department of Chemistry, Technion Israel Institute of Technology Israel Schechter, Professor, Department of Chemistry, Technion Israel Institute of Technology Charles Linder, Department for Desalination and Water Treatment, Zuckerberg Institute for Water Research (ZIWR), Ben-Gurion University of the Negev Viatcheslav F'reger, Department for Desalination and Water Treatment, ZIWR, Ben-Gurion University of the Negev Water filtration technologies employing polymer membranes, especially submerged membrane bioreactors (MBRs), suffer from severe fouling and flux limitations. Methods are sought to improve upon the porous ultrafiltration (UF) membranes currently employed in MBRs and other water treatment processes where biofoulants are present in high concentration. Polymer filtration membranes incorporating amphiphilic graft copolymers have been developed consisting of a poly (vinylidene fluoride) (PVDF) backbone and polyoxyethylene methacrylate (POEM) side chains, PVDF-g-POEM. These materials molecularly self-assemble into bicontinuous nanoscale domains of semicrystalline PVDF, providing structural integrity, and poly (ethylene oxide) (PEO) , providing selective transport channels of well-defined size and anti-fouling character. (Continued)
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Table 10.1 P r o j e c t s Selected for P r i o r i t y F u n d i n g at t h e U.S.-Israel o n Nanotechnology for Water Purification (Continued)
Workshop
Collaborative work in this area will further develop the following findings: Ultrafiltration membranes coated with PVDF-$-POEM exhibit fluxes higher than commercial thin film composite nanofiltration ( N F ) membranes. These membranes also show excellent resistance to fouling by model biomolcculecontaining solutions (proteins, polysaccharides, and natural organic matter) and oily microemulsions in high concentrations ( 1 0 0 ~ 4 0 , 0 0 0ppm). The hydrophilic nanochannels approximately 2 nm in width exhibit molecular sieving ability. 2. Antimicrobial m e m b r a n e coatings Un.ited States Jian-Ku Shang, Material Science Department, UIUC Thomas Mayer, Sandia National Laboratories Israel Carlos Dosoretz, professor, Faculty of Civil and Environmental Engineering, Technion Israel Institute of Technology Roni Kasher, Department for Desalination and Water Treatment, Zuckerberg Institute for Water Research (ZIWR), Ben-Gurion University of the Negev
Membrane surfaces present opportunities for biological attachment and biofilin growth. Researchers will investigate developnient of coatings with antirnicrobial capabilities that can be applied to existing membranes to minimize biological attachment and biofilm formation.
3. C h a r a c t e r i z a t i o n of m i x e d m e t a l oxide n a n o s t r u c t u r e d materials for p h o t o c a t a l y t i c oxidative d e s t r u c t i o n of biological toxins United Sta.tes Dion Dionysiou, Associate Professor, Department of Civil and Environmental Engineering, University of Cincinnati Timothy Strathmann, Assistant Professor, Department of Civil and Environmental Engineering, UIUC Penny Miller, Assistant Professor, Department of Chemistry, Rose-Hulman Institute of Technology
Israel Miron Landau, Professor, Department of Chemical Engineering, Ben-Gurion university of the Negcv Following on exciting findings in work on degradation of biological toxins, especially information on reaction pathways, investigators will study the deployment of mixed metal oxide nanostructured materials in various environments. Dionysiou and Landau are working with Co-TiO, nanocomposite materials and will work to characterize optimum Co loading requirements using impregnation and other techniques, as well as determine optimum Co concentration limits. Strathmann and Miller are working with TiON rianomaterials and will work on the rriechariisrns responsible for micropollutant photocatalysis with undoped and N-doped TiO,, assess micropollutant photocatalysis by rare earth metal doped TiOL materials, quantify coiitaminant degradation and the production of reactive oxygen species by doped materials irradiated with different light energies and sources of light, and quantify thc effect of water quality variables (e.g., pH) and nontarget water constituents (e.g., hurnics) on photocatalysis kinetics. (Continued)
10: U.S.-ISRAEL WORKSHOP ON NANOTECHNOLOGY, SUSTICH Table 10.1 Projects Selected for P r i o r i t y f i n d i n g at t h e U.S.-Israel o n Nanotechnology for Water Purification ( C o n t i n u e d )
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4. E a r l y sensing of biofilm formation for process a n d m a i n t e n a n c e
optimization United States Yi-Lu, Professor, Department of Chemistry, UIUC
Ismel Shimshon Belkin, Professor, Institute of Life Sciences, Hebrew University of .Jerusalem Robert Marks, Department of Biotechnology Engineering, Ben-Gurion University of the Negev Israel Schechter, Professor, Department of Chemistry, Technion Israel Institute of Technology Optimization of cleaning schedules can minimize operational inconvenience and costs in maintaining membrane systems, and extend membrane life by minimizing irreversible fouling. The decision to initiate cleaning can best be made by direct detection of biofilm formation on the membrane surface. Investigators will look at the mechanisms of biological attachment to surfaces to identify potential biochemical signals of attachment and explore development of nanoscale sensors that can be applied to membrane surfaces for biofilm detection. Approach: Genetic engineering and on-site immobilization of a whole-cell microbial sensor that will sense the presence of minute concentrations of metabolites excreted by newly forming biofilms.
References 1. Shiriishon Bclkin, “On-chip canaries: while-cell early warning sentinels,” U.S. -~Israel Workshop on Nanotechnology for Wat,cr Purification, Arlington, VA, 2006. 2. Yi Lu, “DNA biosensors for trace contaniinaiits in water,’’ U.S.-Israel Workshop oii Nanotechnology for Water Purification, Arlington, VA, 2006. 3. Robert Marks, “The 7th sense: bionic fiber-optic biosensors,“ US-Israel Workshop on Nanotechnology for Water Purification, Arlington, VA. 2006. 4. Israel Schechtcr, “New method for on-line analysis of particulates in water,” U.S. -Israel Workshop on Nanotechnology for Water Purification, Arlington, VA, 2006. 5. Michael Strano, “Detection of aqueous contaniiriaiits usiiig t,he near infrared band-gap fluorescence of single-wallcd carbon riaiiotubes,” U.S.-Israel Workshop on Nanotechnology for Water Purification, Arlington, VA, 2006. 6. Yoram Coheri, “Membrane surface nano-structuring: selectivity enhimcement, fouling rediict,ion arid mineral scale formation,” U.S.-Israel Workshop 011Nanotechnology for Water Purification, Arlington, VA, 2006. 7. Ovadia Lev, Jcririy Gun, and Vit,aly Gitis, “Naiiornetric indicators for water filtration and membrane integrity,” U.S.-Israel Workshop on NanotechIiology for Wdt,er Purification, Arliiigt,on, VA, 2006. 8. C. Linder and Y. Oreri, “Relationships between material parameters of iianofiltration iricrribranes arid the rcsultant nicriibrane pcrfoririance,” U.S.--Israel Workshop on Nanotechnology for Wakr Purification, Arlingtoii, VA, 2006. 9. Ariiie Mayes, “High flux, anti-fouliiig polyrricr mernbrarics form sclf-assembling graft copolymers,” U.S.-Israel Workshop on Nanotechnology for Wat,er Purification, Arlington, VA, 2006.
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10. Yorarri Orcrri, C. Liiider, V. Fregcr, Y . Mirsky, V. Shapiro, and 0. Kedmi, “Highly coriductivc riano-tloniaiii based ion cxcliaiige Ineiiibraiics,” US.-Israel Workshop on Naiiot,ecliiiology for Wat,er F’urificat,ioii, Arlington, VA, 200G. 11. B r i m Cliapliri, John Sliaplcy, and Cliarlcs Wcrtli. “1rripac:t of ~i;itiiralwater solutes on nitrate reduction by aliiiiiina-siiI)portc~l pti-cii catalysts,” U.S.~-Isracl Workshop o n Nanotechnology for Wat,er Purifica(.ioii, Arlington, VA, 2006. 12. M.V. Laritiau, Ll. Acca -Wolfovicli, A. Brcmiicr, and M. Herskowitz, “Nariostruct,ured Mil-Ce mixed oxide catalyst for purification of industrial wastewat,er,” U.S.-Israel Workshop on Nanot,echriologv for Water Purification, Arlington, VA, 2006. 13. Tlionias Mayer, “Nanot,eclinologies for desaliiiat,ioii arid arsenic removal,” U.S.-Israel Workshop on Nanotechnology for Water Purification, Arlington, VA, 2006. 14. Moslie Sheirit,uch, Irena Efreiiicnko, arid Uri hlatat,ov-Meytal, “Process developnicmt, of cata1yt)ic w a k r denit,rificatioii: catalyst optiniizatiori, reactor desigii arid qiiaiituni chtmic:al conil.)ut,atioris,” U.S.-Israel Workshop on Nanotechnology for Water Purification. Arlington. VA, 2006. 15. Carlos Dosoret,z, ”Biofoiiliiig build-up on dense rrienibraries in pressure-driven separation processes for wast,t:water treatment,,” U.S. -Israel Workshop on Nnnotcclinology for Water Purification, Arlingt,on, VA, 2006. 16. Meiiaclicni Eliiriclecli, “Relating organic fuuliiig of revers(: osrriosis mc:inbrarics t,o intcrniolcciilar adhesion forces,” U.S.-Israel Workshop OII Na1iotec:hnology for Water Purification, Arlington, VA, 2006. 17. Ovadia Lev arid Jcnriy Gun, “Assuring ;idequate disinfection of drinking water,” U.S.-Israel Workshop on Naiiotechiiology for Water Purification, Arlington, VA, 2006. 18. P.G. Wu, R..C. Xic, J. Inilay, arid J.K. Sliang, “Antirnicrohial materials for wat,er disinfection bascd on visible-light active phot,ocatalysts,” US-Israel Workshop oii Nariotcchiiology for Water Purification, Arlington, VA, 2006. 19. Michael R q e r , “Emerging challenges in wuter security arid infrastructure resilience,” U.S.Israel Workshop on Nanotechnology for Water Purification, Arlingtun, VA, 2006.
Introduction 10.1.1 Workshop Objectives 10.2 Technical Presentations 10.2.1 Contaminant Detection and Sensing 10.2.2 Membrane Synthesis and Membrane Processes 10.2.3 Contaminant Reduction and/or Removal 10.2.4 Biofouling and Disinfection 10.2.5 Water Security and Infrastructure Resilience 10.3 Gap Analysis and Future Research Needs 10.3.1 Membrane Synthesis and Membrane Processes 10.3.2 Biofouling and Disinfection .10.3.3 Contaminant Removal 10.3.4 Sensors 10.4 Collaborative Research Projects 10.1
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Abstract In March 2006, the Center of Advanced Materials for Purification of Water with Systems (WaterCAMPWS), a National Science Foundation Science and Technology Center, and the Israel National Nanotechnology Initiative (INNI) convened an international workshop to assess nanotechnology opportunities for water purification. This chapter summarizes the state of research presented at the workshop and the participants’ assessment of future nanotechnology research needs for water purification, and describes 12 joint international research projects identified by the researchers in the areas of (a) membrane synthesis and processes, (b) biofouling and disinfection, (c) contaminant removal, and (d) environmental monitoring and scnsor developrnent and application.
Savage et al. (eds.), N m o t e c h n o l o ~Applications foT C l e m I.Vatc.1, 131-1-10, 0 2009 William Andrew Inc.
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10.1 Introduction The 2006 joint United States - Israel Nanotechnology for Water Purification workshop brought together more than 50 researchers and included 20 technical presentations and breakout discussions focused on identifying knowledge gaps and future nanotechnology research needs for water purification.
10.1.1 Workshop Objectives The workshop was organized around the following objectives:
1. To assess the current state of nanotechnology applications for water purification through presentation of current research in the areas of (a) desalination and water reclamation/reuse, (b) detection and removal of trace contaminants of concern, and (c) disinfection for human consumption. 2. To identify gaps in (a) the scientific. understanding and characterization of materials and aqueous interactions at the nanoscale, (b) the ability to synthesize nanomaterials and systems with specific, desirable characteristics, (c) the understanding and minimization of fouling in nanotechnology applications in the aqueous environment. 3 . To identify current and future opportunities for nanotechnology to enhance the resilience of existing water purification and distribution infrastructure to natural and anthropogenic catastrophes, including acts of terrorism. 4. To assess and prioritize the identified gaps (point 2) and opportunities (point 3 ) according to their relative impact on potential progress in water purification. 5. To inventory the capabilities of workshop participants to address identified gaps and opportunities. 6. To identify and initiate partnership opportunities among participants to effectively address the gaps and opportunities.
10.2
Technical Presentations
Workshop participants gave 19 technical presentations representing the current state of nanotechnology research in the United States and Israel, organized under the following themes:
10.2.1 Contaminant Detection and Sensing Shimshon Belkin, Hebrew University of Jerusalem, Israel, reported on the development of whole cell biosensors, genetically selected microbial cells with
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high sensitivity to specific toxicants; cell immobilization platforms and signal transduction strategies; and the ticsign of a “toxicity analyzer” [l].Yi Lu, University of Illinois at Urbana- Champaign, United States, described low parts per billion sensors for a variety of metal and organic contaminants based on combinatorial in vitro selection of highly selective catalytic DNA, and both fluorescent and colorimetric signaling for laboratory and field applications [a]. Robert Marks, Ben-Gurion University of the Negrev, Israel, described a conceptual model for a “Lab-in-a-Pen” incorporating chemilumiriescent fiberoptic immunosensors for hepatitis C, West Nile and Ebola viruses, cholera and ovarian cancer using silane or electropolymerization on Indium-tin-oxide (IT0)-coated fiber optics; bioluminescent fiber-optic whole-cell biosensors for gentoxicants, heavy metals and endocrine disruptors; and a chcmiluminescent phagocyte-based sensor [ 3 ] . Israel Schechter, Technion-Israel Institute of Technology (IIT), Israel, discussed the application of laser-induced breakdown spectroscopy, polymeric film sensors coupled to fluorescence fluctuation spectroscopy for dissolved and particulate sampling and analysis [4].Finally, Michael Strano, University of Illinois at Urbana-Champaign, United States, described the synthesis and demonstration of several solution-phase, nearinfrared sensors based on functionalized single-walled carbon nanotubes [5].
10.2.2 Membrane Synthesis and Membrane Processes Yoram Cohen, university of California at Los Angeles, United States, described the application of tethered polymer-modified (TPM) surfaces to create selective pervaporation membranes and fouling-resistant nanofiltrationl ultrafiltration membranes [6]. Ovadia Lev, Hebrew University of Jerusalem, Israel, described development of two nanoscale probes, fluorescent-labeled MS2 bacteriophages and gold nanoparticles, for direct , online evaluation of membrane pore-size integrity [7]. Charles Linder, Ben-Gurion University, Israel, detailed advances in developing chemically stable nanofiltration membranes for tertiary wastewater applications [8].Anne Mayes, Massachusetts Institute of Technology, Unitcd States, described development of self-assembling, anti-fouling polymer filtration membranes incorporating amphiphilic graft copolymers exhibiting improved flux retention [9]. Finally, Yoram Oren, Ben-Gurion Univcrsity, Israel, described preparation of highly oriented heterogeneous electrodialysis membranes by exposing resin particles, non-conductive liquid polymer precursor, and a cross-linker to low-frequency alternating current during membrane curing, resulting in membranes exhibiting >lo0 greater conductivity than conventional, non-oriented membranes [lo].
10.2.3 Contaminant Reduction and/or Removal Charles Werth, University of Illinois at Urbana-Champaign, United States, evaluated an alumina-supported, palladium-copper bimetallic catalyst for
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nitrate reduction for drinking water applications arid discussed fouling impacts from a variety of natural groundwater constituents [ll]. Miron Landau, Ben-Gurion University of the Negev, Israel, described the nanocasting of manganese-cerium oxide catalysts using ordcred mesoporous silica as a removable casting matrix and their applicability for catalytic wet oxidation of organic constituents in industrial wastewaters [12]. Thomas Mayer, Sandia National Laboratories, United States, described the desalination research and arsenic removal research programs of the United States Department of Energy and federal laboratories [13]. Finally, Moshe Sheintuch, Technion-IIT, Israel, reported assembly of a continuous process catalytic reactor for nitrate reduction incorporating bimetallic palladium-copper catalysts on activated carbon cloth support structure, which compared favorably to silica-supported catalysts [14].
10.2.4 Biofouling and Disinfection Carlos Doesertz, Technion-IIT, Israel, discussed the processes of biofilm formation and attachment [15]. Menachem Elimelcch, Yale University, United States, reported on the role of foulant-foulant intermolecular adhesion forces in reverse osmosis membrane fouling and the correlation of elevated calcium and alginate levels to fouling severity [16]. Ovadia Lev, Hebrew University of Jerusalem, Israel, described the current process-specification approach and application of engineering indicators in assuring adequate drinking water disinfection, and the challenges to assuring public safety using emerging disinfection technologies such as ozone [17]. Lastly, Jian-Ku Shang, University of Illinois at Urbana-Champaign, reported the synthesis of quaternary titanium oxide nanoparticles exhibiting disinfection capabilities under visible, as opposed to ultraviolet, light [18].
10.2.5 Water Security and Infrastructure Resilience Michael Royer, U.S. Environmental Protection Agency, described the Agency’s Watersentiriel Initiative to design and demonstrate a pilot contarninarit detection system and response protocol for drinking water utilities that incorporates real-time distribution system water quality monitoring; intensive sampling and analysis for high-priority chemical, biological, and radiological contaminants; integration of water system data with existing public health surveillance systems; and robust customer complaint assessment [ 191.
10.3 Gap Analysis and Future Research Needs Workshop attendees participated in a series of focused discussion sessions to assess current scientific knowledge gaps and identify future research needs for key areas of water purification science and technology.
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10.3.1 Membrane Synthesis and Membrane Processes Minimization of membrane fouling and preservation of membrane functionality by appropriate feed pretreatment to remove nanoparticles and foulants (organic, inorganic, and biological) are essential for successful operation of water treatment, reclamation, and desalination technologies. Research opportunities include enhanced feed characterization (suspended particle composition and morphology, particle-particle and particleesolute interactions) ; biofilm and scale formation (impact of feed water constituents, surface charge, chemistry, particleesurface effects on attachment and growth, role of suspended nanoparticles in scale formation) and mitigation strategies (selective separation of critical precursors, chemical and biological demineralizatiori mechanisms); active anti-fouling membranes incorporating functionalized surfacc and pore nanocatalysts; nanobased, fast-response monitors for feed water quality monitoring and membrane performance/integrity assessment. Development of new, substantially more robust membranes will be dependent on increased Understanding and capabilities in characterizing materials and aqueous interactions at the nanoscale. Areas of critical interest include nanostructure-membrane performance relationships; nanostructure impacts on membrane selectivity, transport, and membrane chemical and mechanical stability; multiscale computation methods for assessing material interactions (particleeparticle, particleesolute, particleesurface, solute-surface) on water and ion transport in confined spaces; casting methodologies for uniform scale-up from nanostructures to commercially relevant membranes. Residuals management plays a significant role in membrane performance and residuals management is a major operational cost in membrane-based purification systems. Substantive advances in residuals minimization and treatment of critical contaminants will require better Understanding of the role of nanoparticlcs and their structure on crystallization, more robust modeling of crystal growth and characterization of crystallites, enhanced understanding of the role and mechanisms of antiscalants in growth control, and methodologies to stabilize supersaturated solutions without precipitation or scale formation.
10.3.2
Biofouling and Disinfection
Controlling the growth of biological organisms and the formation of biofilms is critical both to sustainable operation of water purification systems and to the prevention of disease. Key research opportunities identified by workshop participants in understanding the causes and minimization of biofouling and the deactivation of pathogens include the stimuli and processes responsible for the formation of the initial biofilm layers, strategies for inhibiting initial biofilm formation; surface design and characteristics (e.g., catalytically active moieties) that are resistant to biological attachment, including structural components (e.g., membrane spacers); surface and system design and characteristics that increase shear to minimize cellular attachment; effect of polarization
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layers on biofilm attachment and growth; methods to detect onset of biofilm formation; adhesion mechanisnis for antimicrobial materials on membranes and structural surfaces; strategies and niechanisms for disruption and detachment of biofilms (e.g., acid catalysis, enzymes, biosignal substances); formation pathways, characterization and toxicity of disinfection byproducts; characterization of titania, titania-alumina, and other mixed-metallic oxidative catalysts as altcrnative antiniicrobial agents, and methods for photocatalytic viral deactivation. Point-of-use design for distributed supply systenis, wetweather (e.g., stormwater, combined sewer overflow, sanitary sewer overflow) discharges, and disaster recovery applications were also identified a s critical research areas for successful nanotechnology diffusion.
10.3.3 Contaminant Removal Advances beyond current strategies for removal of critical contaminants or for transformation of critical contaminants to nontoxic forms will require enhanced understanding of molecular transformations, rianostructured systems, and material synthesis, including better understanding of the relationship between nanocatalyst structure and oxidation-reduction pathways for target contaminants, and react ion site competition among contaminant mixtures. Fast computational models are needed to evaluate new catalysis candidates. New surface characterization techniques, for example, spectroscopically active adsorbent probes to characterize surface composition and new cornputation tools to interpret surface characterization will also be essential for improved nanocatalyst synthesis. Lastly, improvements in controlled synthesis of hierarchical nanostructured mixed-metal oxide catalysts, for example, Coo-TiO, and Pd-Cu/C, are warranted for application in tricking-bed and fixed-bed heterogeneous react or systems.
10.3.4 Sensors The ability to sense a wide range of environmental and system conditions, and to detect select contaminants with high specificity and sensitivity is emerging as one of the most critical aspects for the efficient and effective operation of water purification technologies, for extending the useful lifetimes of water and wastewater infrastructure assets, and for protecting the public and infrastructure assets from natural and anthropogenic threats. A number of nanoscale sensor approaches were identified for further research and potential development, including combinatorial selection of aptamers for sensing presence of biofilins cells; solid-phase, polymer-film extraction/laser-inducedfluorescence for capture and detection of polycyclic aromatic hydrocarbons; impedirnetric and colorimetric sensors incorporating hormonal and other binding receptors in synthetic lipid bilayer membranes for detection of endocrine disruptors; impedimetric sensors embedded directly into treatment membranes and on pipe surfaces for detection of biofilm formation.
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10.4 Collaborative Research Projects The most significant outcome of the workshop was the identification of a series of 12 international collaborative projects directed at practical applications of nanotechnology for improving water quality. Four of these projects (Table 10.1) were selected for priority funding based on their perceived benefits to water purification and their potential for commercial development within the next five years. Independent work toward these projects continues in both the United States and Israel while conference organizers in both countries solicit funding to facilitate a second workshop in 2009 or 2010. Further information regarding the workshop, full abstracts of the technical presentations, and descriptions of the 12 joint research projects established during the workshop can be found at the website http://www.watercampws. uiuc.edu/ index. php? menu-i t em 'id= 114.
T a b l e 10.1 Projects Selected for P r i o r i t y F u n d i n g at the U S - I s r a e l W o r k s h o p o n Nanotechnology for Water Purification 1. Novel polymer morphologies for u n i q u e m e m b r a n e selectivity
United States Ann Mayes, Toyota Professor of Materials Science and Engineering, Massachusetts Institute of Technology Charles Werth, Civil and Environmental Engineering Department, University of llinois at Urbana-Champaign (UIUC) I,57d Moris S. Eisen, Professor, Department of Chemistry, Technion Israel Institute of Technology Israel Schechter, Professor, Department of Chemistry, Technion Israel Institute of Technology Charles Linder, Department for Desalination and Water Treatment, Zuckerberg Institute for Water Research (ZIWR), Ben-Gurion University of the Negev Viatcheslav F'reger, Department for Desalination and Water Treatment, ZIWR, Ben-Gurion University of the Negev Water filtration technologies employing polymer membranes, especially submerged membrane bioreactors (MBRs), suffer from severe fouling and flux limitations. Methods are sought to improve upon the porous ultrafiltration (UF) membranes currently employed in MBRs and other water treatment processes where biofoulants are present in high concentration. Polymer filtration membranes incorporating amphiphilic graft copolymers have been developed consisting of a poly (vinylidene fluoride) (PVDF) backbone and polyoxyethylene methacrylate (POEM) side chains, PVDF-g-POEM. These materials molecularly self-assemble into bicontinuous nanoscale domains of semicrystalline PVDF, providing structural integrity, and poly (ethylene oxide) (PEO) , providing selective transport channels of well-defined size and anti-fouling character. (Continued)
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Table 10.1 P r o j e c t s Selected for P r i o r i t y F u n d i n g at t h e U.S.-Israel o n Nanotechnology for Water Purification (Continued)
Workshop
Collaborative work in this area will further develop the following findings: Ultrafiltration membranes coated with PVDF-$-POEM exhibit fluxes higher than commercial thin film composite nanofiltration ( N F ) membranes. These membranes also show excellent resistance to fouling by model biomolcculecontaining solutions (proteins, polysaccharides, and natural organic matter) and oily microemulsions in high concentrations ( 1 0 0 ~ 4 0 , 0 0 0ppm). The hydrophilic nanochannels approximately 2 nm in width exhibit molecular sieving ability. 2. Antimicrobial m e m b r a n e coatings Un.ited States Jian-Ku Shang, Material Science Department, UIUC Thomas Mayer, Sandia National Laboratories Israel Carlos Dosoretz, professor, Faculty of Civil and Environmental Engineering, Technion Israel Institute of Technology Roni Kasher, Department for Desalination and Water Treatment, Zuckerberg Institute for Water Research (ZIWR), Ben-Gurion University of the Negev
Membrane surfaces present opportunities for biological attachment and biofilin growth. Researchers will investigate developnient of coatings with antirnicrobial capabilities that can be applied to existing membranes to minimize biological attachment and biofilm formation.
3. C h a r a c t e r i z a t i o n of m i x e d m e t a l oxide n a n o s t r u c t u r e d materials for p h o t o c a t a l y t i c oxidative d e s t r u c t i o n of biological toxins United Sta.tes Dion Dionysiou, Associate Professor, Department of Civil and Environmental Engineering, University of Cincinnati Timothy Strathmann, Assistant Professor, Department of Civil and Environmental Engineering, UIUC Penny Miller, Assistant Professor, Department of Chemistry, Rose-Hulman Institute of Technology
Israel Miron Landau, Professor, Department of Chemical Engineering, Ben-Gurion university of the Negcv Following on exciting findings in work on degradation of biological toxins, especially information on reaction pathways, investigators will study the deployment of mixed metal oxide nanostructured materials in various environments. Dionysiou and Landau are working with Co-TiO, nanocomposite materials and will work to characterize optimum Co loading requirements using impregnation and other techniques, as well as determine optimum Co concentration limits. Strathmann and Miller are working with TiON rianomaterials and will work on the rriechariisrns responsible for micropollutant photocatalysis with undoped and N-doped TiO,, assess micropollutant photocatalysis by rare earth metal doped TiOL materials, quantify coiitaminant degradation and the production of reactive oxygen species by doped materials irradiated with different light energies and sources of light, and quantify thc effect of water quality variables (e.g., pH) and nontarget water constituents (e.g., hurnics) on photocatalysis kinetics. (Continued)
10: U.S.-ISRAEL WORKSHOP ON NANOTECHNOLOGY, SUSTICH Table 10.1 Projects Selected for P r i o r i t y f i n d i n g at t h e U.S.-Israel o n Nanotechnology for Water Purification ( C o n t i n u e d )
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4. E a r l y sensing of biofilm formation for process a n d m a i n t e n a n c e
optimization United States Yi-Lu, Professor, Department of Chemistry, UIUC
Ismel Shimshon Belkin, Professor, Institute of Life Sciences, Hebrew University of .Jerusalem Robert Marks, Department of Biotechnology Engineering, Ben-Gurion University of the Negev Israel Schechter, Professor, Department of Chemistry, Technion Israel Institute of Technology Optimization of cleaning schedules can minimize operational inconvenience and costs in maintaining membrane systems, and extend membrane life by minimizing irreversible fouling. The decision to initiate cleaning can best be made by direct detection of biofilm formation on the membrane surface. Investigators will look at the mechanisms of biological attachment to surfaces to identify potential biochemical signals of attachment and explore development of nanoscale sensors that can be applied to membrane surfaces for biofilm detection. Approach: Genetic engineering and on-site immobilization of a whole-cell microbial sensor that will sense the presence of minute concentrations of metabolites excreted by newly forming biofilms.
References 1. Shiriishon Bclkin, “On-chip canaries: while-cell early warning sentinels,” U.S. -~Israel Workshop on Nanotechnology for Wat,cr Purification, Arlington, VA, 2006. 2. Yi Lu, “DNA biosensors for trace contaniinaiits in water,’’ U.S.-Israel Workshop oii Nanotechnology for Water Purification, Arlington, VA, 2006. 3. Robert Marks, “The 7th sense: bionic fiber-optic biosensors,“ US-Israel Workshop on Nanotechnology for Water Purification, Arlington, VA. 2006. 4. Israel Schechtcr, “New method for on-line analysis of particulates in water,” U.S. -Israel Workshop on Nanotechnology for Water Purification, Arlington, VA, 2006. 5. Michael Strano, “Detection of aqueous contaniiriaiits usiiig t,he near infrared band-gap fluorescence of single-wallcd carbon riaiiotubes,” U.S.-Israel Workshop on Nanotechnology for Water Purification, Arlington, VA, 2006. 6. Yoram Coheri, “Membrane surface nano-structuring: selectivity enhimcement, fouling rediict,ion arid mineral scale formation,” U.S.-Israel Workshop 011Nanotechnology for Water Purification, Arlington, VA, 2006. 7. Ovadia Lev, Jcririy Gun, and Vit,aly Gitis, “Naiiornetric indicators for water filtration and membrane integrity,” U.S.-Israel Workshop on NanotechIiology for Wdt,er Purification, Arliiigt,on, VA, 2006. 8. C. Linder and Y. Oreri, “Relationships between material parameters of iianofiltration iricrribranes arid the rcsultant nicriibrane pcrfoririance,” U.S.--Israel Workshop on Nanotechnology for Wakr Purification, Arlingtoii, VA, 2006. 9. Ariiie Mayes, “High flux, anti-fouliiig polyrricr mernbrarics form sclf-assembling graft copolymers,” U.S.-Israel Workshop on Nanotechnology for Wat,er Purification, Arlington, VA, 2006.
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10. Yorarri Orcrri, C. Liiider, V. Fregcr, Y . Mirsky, V. Shapiro, and 0. Kedmi, “Highly coriductivc riano-tloniaiii based ion cxcliaiige Ineiiibraiics,” US.-Israel Workshop on Naiiot,ecliiiology for Wat,er F’urificat,ioii, Arlington, VA, 200G. 11. B r i m Cliapliri, John Sliaplcy, and Cliarlcs Wcrtli. “1rripac:t of ~i;itiiralwater solutes on nitrate reduction by aliiiiiina-siiI)portc~l pti-cii catalysts,” U.S.~-Isracl Workshop o n Nanotechnology for Wat,er Purifica(.ioii, Arlington, VA, 2006. 12. M.V. Laritiau, Ll. Acca -Wolfovicli, A. Brcmiicr, and M. Herskowitz, “Nariostruct,ured Mil-Ce mixed oxide catalyst for purification of industrial wastewat,er,” U.S.-Israel Workshop on Nanot,echriologv for Water Purification, Arlington, VA, 2006. 13. Tlionias Mayer, “Nanot,eclinologies for desaliiiat,ioii arid arsenic removal,” U.S.-Israel Workshop on Nanotechnology for Water Purification, Arlington, VA, 2006. 14. Moslie Sheirit,uch, Irena Efreiiicnko, arid Uri hlatat,ov-Meytal, “Process developnicmt, of cata1yt)ic w a k r denit,rificatioii: catalyst optiniizatiori, reactor desigii arid qiiaiituni chtmic:al conil.)ut,atioris,” U.S.-Israel Workshop on Nanotechnology for Water Purification. Arlington. VA, 2006. 15. Carlos Dosoret,z, ”Biofoiiliiig build-up on dense rrienibraries in pressure-driven separation processes for wast,t:water treatment,,” U.S. -Israel Workshop on Nnnotcclinology for Water Purification, Arlingt,on, VA, 2006. 16. Meiiaclicni Eliiriclecli, “Relating organic fuuliiig of revers(: osrriosis mc:inbrarics t,o intcrniolcciilar adhesion forces,” U.S.-Israel Workshop OII Na1iotec:hnology for Water Purification, Arlington, VA, 2006. 17. Ovadia Lev arid Jcnriy Gun, “Assuring ;idequate disinfection of drinking water,” U.S.-Israel Workshop on Naiiotechiiology for Water Purification, Arlington, VA, 2006. 18. P.G. Wu, R..C. Xic, J. Inilay, arid J.K. Sliang, “Antirnicrohial materials for wat,er disinfection bascd on visible-light active phot,ocatalysts,” US-Israel Workshop oii Nariotcchiiology for Water Purification, Arlington, VA, 2006. 19. Michael R q e r , “Emerging challenges in wuter security arid infrastructure resilience,” U.S.Israel Workshop on Nanotechnology for Water Purification, Arlingtun, VA, 2006.