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Solar Photocatalytic Water Purification: Microfluidic Reactors as a Model System

Oxford-Princeton collaborative workshop. Solar Photocatalytic Water Purification: Microfluidic Reactors as a Model System. Jiandi Wan and Howard Stone. Outline. Motivation: concerns in water purification Water purification: goals of next generation systems

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Solar Photocatalytic Water Purification: Microfluidic Reactors as a Model System

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  1. Oxford-Princeton collaborative workshop Solar Photocatalytic Water Purification: Microfluidic Reactors as a Model System Jiandi Wan and Howard Stone

  2. Outline • Motivation: concerns in water purification • Water purification: goals of next generation systems • Outlook: challenges of photocatalytic microfluidic reactors • Solar photocatalytic water purification • Applications of micro/nanotechnology (microfluidics) in water purification

  3. Clean water crisis • 80% of urban rivers in China are • contaminated to varying degrees • 1.2 billon people globally • lack access to clean water • Millions of people die • annually due to water • related diseases • Qu, et al. Critical Reviews in Environmental Science and Technology, 2010, 40, 519–560. Shannon, et al. • Nature, 2008, 452, 301-310.

  4. Concerns in water crisis • Drinking water production: Disinfection: extensive chemicals treatments, e.g., chlorine, and high power UV expose. • Waste water treatment (industrial and municipal): Decontamination (metal ions): extensive chemicals treatments , e.g., chelating chemicals, and absorbents, or membrane technology • Seawater desalination: reverse osmosis membrane

  5. Engineering “natural” systems for water purification • Next-generationsystems: low-environmental-impact, low-energy-intensive, and high efficiency • Solar photocatalytic detoxification and disinfection: solar reactors, photocatalyts, hybrid photocatalytic-biological process, and photocatalytic membrane process. • Micro/nanotechnology in water purification: carbon nanotubes membranes, nanofiber membranes, nanoporous ceramics, clays, and micro/nanofluidics. • Peters, et al. Chem. Eng. Technol. 2010, 33, 1233–1240. Shannon, et al. Nature, 2008, 452, 301-310. • Hochstrat, et. al. Desalination and water treatment, 2010, 18, 96-102. Valli, et al. Int. J. Nuclear • Desalination, 2010 , 4, 49-57. Blanco-Galvez, et al. J Solar Energy Engineering. 2007, 129, 4-15.

  6. Photocatalytic detoxification and disinfection of water • 1. Photo-induced charge separation • 2. Generation of hydroxyl radicals • 3. Oxidation of organics • Belhacova, et al. J Chem Technol Biotechnol , 1999, 74, 149-–154.

  7. Photocatalytic disinfection Blanco-Galvez, et al. J Solar Energy Engineering. 2007, 129, 4-15.

  8. Photocatalytic reactors for water detoxification (immobilized TiO2) • TiO2 on optical • fibers • TiO2 on • membranes • TiO2 in microfluidic • channels Lin, et al. J. Applied Electrochemistry, 2005, 35, 699–708. Lindstrom, et al. AIChE J. 2007, 53, 3 695-702. Molinari, et al. J Membrane Science, 2002, 206, 399–415.

  9. Challenges of photocatalytic detoxification and disinfection of water • Characterization standards: detoxification efficiency is strongly dependent on the structure and reactivity of pollutants, catalysts, and the reaction environment. • Commercial • viability • Photocatalyst: slow kinetics, low photoefficiency, and narrow coverage of solar spectrum • Reaction • Efficiency • Hybrid process: integrative photocatalytic process with biological and membrane process • Overall • Efficiency • Blanco-Galvez, et al. J Solar Energy Engineering. 2007, 129, 4-15. Friedmann et al. Applied Catalysis B: • Environmental 2010, 99, 398–406.

  10. Micro/nanofluidics in water purification • Microfluidics act as sensors for detection of toxic compounds in water. Cleary, et al. IEEE sensors Journal. 2008, 5, 508-515. Curtis, et al. Lab on a chip. 2009, 9, 2176–2183 • Microfluidics for detecting and capturing microorganism in water. Balasubramanian, et al. Lab on a chip 2007, 7, 1315–1321. Liu, et al.Water Science & Technology: Water Supply, 2007, 7, 165-172. Chieko, et al. J Microbiological Methods 2007, 68, 643-647. • Micro/nanofluidics for water desalination. Kim, et al. Nature Nanotechnology. 2010, 5, 297-301.

  11. Photocatalytic microfluidic reactors • Microfluidic model system to integrate hydrodynamics with photochemical reactions • Quantitative understanding photocatalytic reactions under flow conditions, e.g. flow in porous media • Establish protocols for standardize parameters for photocatalytic water purification • Microfluidic approaches for synthesis of effective photocatalytic nanoparticles • Nanoparticles with high photoefficiencyand broad solar spectrum coverage • Integrative photocatalytic microfluidic devices with membrane or biological process

  12. Outlook • Clean water production • Effective device fabrication

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