Photocatalysis and Water Purification

Water is one of the essential resources on our planet. Therefore, fresh water and the recycling of waste-water are very important topics in various areas. Energy-saving green technologies are a demand in this area of research.

Photocatalysis comprises a class of reactions which use a catalyst activated by light. These reactions include the decomposition of organic compounds into environmental friendly water and carbon dioxide, leading to interesting properties of surfaces covered with a photocatalyst:
they protect e.g. against incrustation of fouling matter, they are self-cleaning, antibacterial and viricidal. Therefore, they are attractive candidates for environmental applications such as water purification and waste-water treatment.

This book introduces scientists and engineers to the fundamentals of photocatalysis and enlightens the potentials of photocatalysis to increase water quality. Also, strategies to improve the photocatalytic efficacy are pointed out: synthesis of better photocatalysts, combination of
photocatalysis with other technologies, and the proper design of photocatalytic reactors. Implementation of applications and a chapter on design approaches for photocatalytic reactors round off the book.

'Photocatalysis and Water Purification' is part of the series on Materials for Sustainable Energy and Development edited by Prof. G.Q. Max Lu. The series covers advances in materials science and innovation for renewable energy, clean use of fossil energy, and greenhouse gas mitigation and associated environmental technologies.

Auteur
Professor Pierre Pichat is first class Research Director at the French National Center for Scientific Research (CNRS) in Lyon. He has been active in heterogeneous photocatalysis for more than three decades, and founded the laboratory of "Photocatalyse, Catalyse et Environment" at the Ecole Centrale de Lyon. He has published a great number of research papers and several review articles dealing with photocatalytic reactions and materials.
At the "9th International Conference on TiO2 photocatalysis: fundamentals and applications", held in 2004 in San Diego, he received an Appreciation Award acknowledging his pioneering contributions; this award has been conferred to only three scientists in 20 years.

Contenu

PREFACE

PART I: Fundamentals: Active Species, Mechanisms, Reaction Pathways

IDENTIFCATION AND ROLES OF THE ACTIVE SPECIES GENERATED ON VARIOUS PHOTOCATALYSTS
Key Species in Photocatalytic Reactions
Trapped Electron and Hole
Superoxide Radical and Hydrogen Peroxide (O2 and H2O2)
Hydroxyl Radical (OH)
Singlet Molecular Oxygen (1O2)
Reaction Mechanisms for Bare TiO2
Reaction Mechanisms of Visible-Light-Responsive Photocatalysts
Conclusion

PHOTOCATALYTIC REACTION PATHWAYS - EFFECTS OF MOLECULAR STRUCTURE, CATALYST, AND WAVELENGTH
Introduction
Methods for Pathway Determination
Prototypical Oxidative Reactivity in Photocatalytic Degradations
Prototypical Reductive Reactivity in Photocatalytic Degradations
The Use of Organic Molecules as Test Probes for Next-Generation Photocatalysts
Modified Catalysts: Wavelength-Dependent Chemistry of Organic Probes
Conclusions

PHOTOCATALYTIC MECHANISMS AND REACTION PATHWAYS DRAWN FROM KINETIC AND PROBE MOLECULES
The Photocatalyic Rate
Surface Speciation
Multisite Kinetic Model
Conclusion

PART II: Improving the Photocatalytic Efficacy

DESIGN AND DEVELOPMENT OF ACTIVE TITANIA AND RELATED PHOTOCATALYSTS
Introduction - a Thermodynamic Aspect of Photocatalysis
Photocatalytic Activity: Reexamination
Design of Active Photocatalysts
A Conventional Kinetics in Photocatalysis: First-Order Kinetics
A Conventional Kinetics in Photocatalysis: Langmuir - Hinshelwood Mechanism
Topics and Problems Related to Particle Size of Photocatalysts
Recombination of a Photoexcited Electron and a Positive Hole
Evaluation of Crystallinity as a Property Affecting Photocatalytic Activity
Electron Traps as a Possible Candidate of a Recombination Center
Donor Levels - a Meaning of n-Type Semiconductor
Dependence of Photocatalytic Activities on Physical and Structural Properties
Synergetic Effect
Doping
Conclusive Remarks

MODIF IED PHOTOCATALYSTS
Why Modifying?
Forms of Modification
Modified Physicochemical Properties

IMMOBILIZATION OF A SEMICONDUCTOR PHOTOCATALYST ON SOLID SUPPORTS: METHODS, MATERIALS, AND APPLICATIONS
Introduction
Immobilization Techniques
Supports
Laboratory and Industrial Applications of Supported Photocatalysts
Conclusion

WASTEWATER TREATMENT USING HIGHLY FUNCTIONAL IMMOBILIZED TIO2 THIN-FILM PHOTOCATALYSTS
Introduction
Application of a Cascade Falling-Film Photoreactor (CFFP) for the Remediation of Polluted Water and Air under Solar Light Irradiation
Application of TiO2 Thin-Film-Coated Fibers for the Remediation of Polluted Water
Application of TiO2 Thin Film for Photofuel Cells (PFC)
Preparation of Visible-Light-Responsive TiO2 Thin Films and Their Application to the Remediation of Polluted Water
Conclusions

SENSITIZATION OF TITANIA SEMICONDUCTOR: A PROMISING STRATEGY TO UTILIZE VISIBLE LIGHT
Introduction
Principle of Photosensitization
Dye Sensitization
Polymer Sensitization
Surface-Complex-Mediated Sensitization
Solid Semiconductor/Metal Sensitization
Other Strategies to Make Titania Visible Light Active
Conclusions

PHOTOELECTROCATALYSIS FOR WATER PURIF ICATION
Introduction
Photoeffects at Semiconductor Interfaces
Water Depollution at Photoelectrodes
Photoelectrode Materials
Electrodes Preparation and Reactors
Conclusions

PART III: Effects of Photocatalysis on Natural Organic Matter and Bacteria

PHOTOCATALYSIS OF NATURAL ORGANIC MATTER IN WATER: CHARACTERIZATION AND TREATMENT INTEGRATION
Introduction
Monitoring Techniques
By-products from the Photocatalytic Oxidation of NOM and its Resultant Disinfection By-Products (DBPs)
Hybrid Photocatalysis Technologies for the Treatment of NOM
Conclusions

WATERBORNE ESCHERICHIA COLI INACTIVATION BY TIO2 PHOTOASSISTED PROCESSES: A BRIEF OVERVIEW
Introduction
Physicochemical Aspects Affecting the Photocatalytic E. coli Inactivation
Using of N-Doped TiO2 in Photocatalytic Inactivation of Waterborne Microorganisms
Biological Aspects
Proposed Mechanisms Suggested for Bacter