photochemical purification of water and air · reaction kinetics. this idea is thought to be very...

Photochemical Purification ofWater and Air

Thomas Oppenländer

InnodataFile Attachment9783527610891.jpg

Thomas Oppenländer


Author

Thomas OppenländerUniversity of Applied Sciences(Fachhochschule) FurtwangenDepartment of Mechanical andChemical EngineeringJakob-Kienzle-Str. 1778054 Villingen-SchwenningenGermanyEmail: [email protected]

José Franco-Pereira, who received the degree of aMagister Artium (M.A.) in film and media sci-ences at the University of Frankfurt (Germany),kindly designed the cover picture.

Library of Congress Card No.:Applied for.

British Library Cataloguing-in-Publication Data:A catalogue record for this book is available fromthe British Library.

Bibliographic information published byDie Deutsche BibliothekDie Deutsche Bibliothek lists this publication inthe Deutsche Nationalbibliografie; detailed biblio-graphic data is available in the Internet at.

2003 WILEY-VCH VerlagGmbH & Co. KGaA, Weinheim

All rights reserved (including those of translationin other languages). No part of this book may bereproduced in any form – by photoprinting, mi-crofilm, or any other means – nor transmitted ortranslated into machine language without writtenpermission from the publishers. Registerednames, trademarks, etc. used in this book, evenwhen not specifically marked as such, are not tobe considered unprotected by law.

Printed in the Federal Republic of Germany.

Printed on acid-free paper.

Composition K + V Fotosatz GmbH, BeerfeldenPrinting betzdruck GmbH, DarmstadtBookbinding Litges & Dopf BuchbindereiGmbH, HeppenheimISBN 3-527-30563-7

n This book was carefully produced. Nevertheless,author and publisher do not warrant the informa-tion contained therein to be free of errors. Rea-ders are advised to keep in mind that statements,data, illustrations, procedural details or otheritems may inadvertently be inaccurate.

The field of Advanced Oxidation Processes (AOPs) or Advanced Oxidation Technolo-gies (AOTs) is of relatively recent vintage. However, AOPs/AOTs are proving to beimportant contributions to the treatment of water and air to remove harmful andtoxic contaminants. Thus, it is gratifying to see this very comprehensive andauthoritative treatise appear covering all aspects of AOPs/AOTs. These range fromthe treatment of industrial wastewaters, drinking water (both contaminant re-moval and disinfection), ultrapure water to the purification and deodorizing of air.Light sources include low pressure and medium pressure UV lamps, flash lamps,incoherent excimer lamps and sunlight itself.

This treatise includes 146 figures, 17 worked out examples and 37 tables (manyof which contain valuable collections of data and references). Each of the ninechapters cites extensive references, including very recent papers where the readercan follow up information in more detail.

Professor Oppenländer is well qualified to write about AOPs/AOTs, since hehas contributed to this literature in a very significant manner. It is thus particular-ly valuable to see the application of incoherent excimer lamps covered so well, asubject that has been a central part of his research. Finally, it is good to see care-ful attention being made to consistent terms, definitions and units in accord withIUPAC recommendations.

This book will be of considerable value to graduate students, science and engi-neering faculty, scientists, process engineers and sales engineers in industry,government regulators and health professionals and all others with an interest inpurifying our water and air.

James R. BoltonPresident, Bolton Photosciences Inc.628 Cheriton Cres., NW, Edmonton AB, Canada T6R 2M5

V

Foreword

Thomas Oppenländer studied chemistry at the University of Würzburg (Germany).He received his doctoral degree (Dr. rer. nat.) in 1984 working in the researchgroup of Waldemar Adam on 185-nm-photochemistry of azoalkanes in solution.The following year was spent as a postdoctoral fellow at Colorado State University(Fort Collins, USA) in the group of Albert I. Meyers being involved in the asym-metric synthesis of dihydropyridines and NADH mimics. From 1985 to 1991 hewas affiliated with F. Hoffmann-La Roche in Basel (Switzerland). Here he wasengaged in research on drug phototoxicity and on the photochemical productionof fine chemicals. Since 1991 he has been a full professor at the University ofApplied Sciences (Fachhochschule) of Furtwangen (Germany) in the Departmentof Mechanical and Chemical Engineering, where he has been involved in photo-initiated advanced oxidation technologies. His main interests concentrate on thepotentials of novel incoherent excimer lamps for photochemical treatment ofwater and air.

VI

Curriculum vitae

This book is aimed at researchers, engineers, and students who deal with prob-lems in the expanding field of photo-initiated process technologies of water or airtreatment. It lays claim to be a mine of information related to these interdisciplin-ary topics and presents a selection of the most important primary and secondaryliterature in this area of research and development. Clearly not all references ofthe vast research literature could be incorporated. The detailed discussion ofmany examples taken from the current scientific literature facilitates access to re-search topics of particular interest from different but interrelated point of views.This is supported by tables that collect together interesting studies, which dealwith new developments of photochemical advanced oxidation processes and tech-nologies allowing easy access to the primary scientific literature. A most impor-tant feature of this book is that it presents many detailed figures for the purposeof visualization of photochemical and photophysical phenomena, for the presenta-tion of the underlying basic principles and for the interpretation of important re-search results. Additionally, several helpful example calculations are presented todemonstrate the use of quoted equations dealing, for example, with photons andreaction kinetics. This idea is thought to be very helpful in the understanding ofthe mathematical relationships presented

Thus, the reader will become acquainted with the basic knowledge that is essen-tial for an understanding of photochemical processes. This will enable him/her tocarry out laboratory and large-scale experiments with the aim of developing andimproving AOPs. There are many researchers and engineers in water and air in-dustries who require more extensive and novel information than that which is ob-tainable from textbooks that have their emphasis placed on tradition. Therefore,this book intends to supply such missing information to as great an extent as ispossible.

To avoid any misinterpretations concerned with the digit style of numbers, thedecimal point is used throughout the book instead of a comma (i.e. computer no-tation: 1.03 instead of 1,03, except for some graphical representations). In repre-sentative molecular structures, spin-paired non-bonding electrons around an atomof a molecule are represented (if necessary) by a bold line “�”, in accord withcommonly used Lewis-structures. Single electrons are represented by a dot “•”. Afull arrow (�) indicates shifts of electron pairs, whereas single electron shifts are

VII

Preface

shown by using a half arrow (�). In photoscience an asterisk (*) usually denotesan electronically exited state of a molecule or atom, whereas in molecular orbital(MO) theory it marks an anti-bonding molecular orbital.

The occasional use of commercial names to identify materials and instrumentsin no way implies endorsement or recommendation by the author.

Thomas Oppenländer, November 2002

PrefaceVIII

Introduction 1

1 AOPs and AOTs 5

2 Why UV and Oxidation/Disinfection? 192.1 Global Water Resources and Resulting Water Market 192.2 Present and Historical Dimensions of the Radiation Concept 242.3 Some Historical Landmarks of the Development of AOTs 29References 32

3 Interaction of UV/VIS Radiation with Matter 373.1 Photoscience in Research and Development 373.2 Physical Constants and Standard Values Used in Photochemistry 403.3 The Electromagnetic Wave 403.4 The Photon Stream and Planck’s Equation 413.5 Electromagnetic Spectral Ranges of Interest in Photochemistry 443.6 Conversion of Energy Units and Other Useful Conversions 463.7 Photon Energies, Bond Dissociation Energies, Threshold Wavelengths

and Absorption Onset of Molecules 513.8 Absorption of UV Radiation by Molecules 553.9 The Beer–Lambert Relationship 563.10 The Nature of Electronically Excited States 603.11 The Jablonski Diagram 643.12 Absorption of UV/VIS Radiation by Solids 663.13 UV/VIS Radiation as a Specific Reagent: Quantum Yield, Quantum

Efficiency, Actinometry and Photoreaction Kinetics 683.14 Terms Associated with the Emission and Receipt of Electromagnetic

Radiation 733.15 Safety Precautions for Radiant Sources 75References 76

4 VUV and UV Radiant Sources and their Characteristics 794.1 Types of Lamps used in AOP Research and Development 794.2 Specific Properties of Mercury Arc Lamps 83

IX

Contents

4.3 Development of Incoherent Excimer Lamps 874.4 Typical Photon Flow of VUV or UV Lamps 944.5 The Sun as Radiation Source 94References 97

5 Photochemical Processes of Water Treatment 1015.1 Description of Aqueous Systems 1015.1.1 Classification of Water Constituents 1015.1.2 Analytical Parameters of Water Quality 1055.1.3 Synopsis: Water and Wastewater Treatment Technologies 1125.1.4 Synopsis: Oxidative Water Treatment Technologies and Methods of

Hydroxyl Radical Production 1145.2 Nomenclature of Photochemical AOPs 1185.2.1 Photooxidation Reactions 1195.2.2 Photocatalytic Reactions 1205.3 General Reaction Schemes 1225.3.1 Photo-Initiated Oxidations 1225.3.2 Heterogeneous Photocatalysis 1235.3.3 Homogeneous Photocatalysis 1245.3.4 Photolysis of Water 1265.4 Status of Technical Realization of Photo-initiated AOPs and

Photochemical Treatment Strategies 1275.5 Photodegradation of Water Pollutants 130References 136

6 Properties, Reactivity and Photochemistry of Auxiliary Chemicals 1456.1 Electronic Structures of Oxygen Species Involved 1456.2 Reduction Potentials 1496.3 UV Absorption Properties of Auxiliary Oxidants, Catalysts and of

Reactive Intermediates 1496.4 Physical-chemical Properties of Ozone and Hydrogen Peroxide 1556.4.1 Ozone 1556.4.2 Hydrogen Peroxide 1556.4.3 Photochemistry of Hydrogen Peroxide 1576.5 Photocatalysts 1596.6 Quantum Yields 1626.7 Primary and Secondary Reactive Species 1666.7.1 Hydrated Electrons 1676.7.2 Hydrogen Atoms 1686.7.3 Hydroxyl Radicals 1686.8 Oxidative Degradation of Organic Matter by Hydroxyl Radicals 1726.8.1 Aliphatic and Aromatic Hydrocarbons 1726.8.2 Chlorinated Hydrocarbons 1776.9 Rate Law and Rate Constants of Hydroxyl Radical Reactions 178References 183

ContentsX

7 Photooxidation and Photomineralization of Organic Matterin Water and Air 189

7.1 Aqueous Systems 1897.1.1 Substrate Oxidation and Substrate Mineralization 1897.1.2 Reaction and Kinetic Modeling of H2O2-UV AOPs 1917.1.3 Vacuum-UV Oxidation: The H2O-VUV AOP 2007.1.4 Comparative Studies of Photo-Initiated AOPs 2137.1.5 Biodegradability and Toxicological Studies 2157.2 Gaseous Systems 2197.2.1 Applicability 2197.2.2 Chemical and Physical-Chemical Aspects of Air Pollution 2217.2.3 Process Technologies of Air Treatment 225References 231

8 Process Engineering and Reactor Concepts 2398.1 Chemical Engineering 2398.2 Photoreactor Concepts 2438.3 Reactor Materials 2508.4 Influences on the Process Performance and Design Criteria 2548.5 Economic Factors and Design Parameters (Figures-of-Merit) of Photo-

Initiated AOPs 2578.6 Selected Industrial Applications 2688.6.1 Aqueous Systems 2688.6.2 Gaseous Systems 269References 273

9 UV Disinfection 279References 290

10 Alternative Glossary 295References 297

Glossary of Terms Used in Photochemistry 299

Index 353

Contents XI

Abbreviations/Symbolsa) Units Definition

[C], c mol L–1 or g L–1 Concentration b)

2,4-DCP – 2,4-DichlorophenolA m2 Areaa m–1 (SI) or cm–1 (Decadic) absorption coefficientA10, e – Absorbance (base 10 or base e)abs (superscript) – AbsorbedACM m

2 kg–1 Collector area per massACO m

2 m–3 order–1 Collector area per orderads (subscript) – AdsorbedAO – Atomic orbitalAOP – Advanced oxidation processAOT – Advanced oxidation technologya-Ox – Auxiliary oxidantaq (subscript) – Aqueous, hydratedc0 m s

–1 Speed of light in vacuumcb – Conduction bandCFBR – Contact-free batch reactorCFC – Chlorinated fluorocarbonCFU m–3 (SI), L–1, cm–3 Colony forming unitsCHC – Chlorinated hydrocarbonCSTR – Continuously stirred tank reactorDBE – Dielectric-barrier dischargeDBP – Disinfection by-productDDT – DichlorodiphenyltrichloroethaneDO – Dissolved molecular oxygenDOM – Dissolved organic matterE V Reduction potentiale (subscript) – EnergeticEbg eV Band gap energyEEA – European Environment AgencyEEM kW h kg

–1 Electric energy per massEEO kW h m

–3 order–1 Electric energy per orderel (subscript) – ElectricEOP – Enhanced oxidation processesEp m

–2 s–1 or mol m–2 s–1 Photon irradiance (cf. Tab. 3-9)

XIII

Abbreviations and Symbols


Ep J Energy of a photoneV eV Electron voltFWHM – Full width at half maximum (half-width)g (subscript) – Gaseoush J s Planck constantH0 J m

–2 Fluence (cf. Tab. 3-9)HC – HydrocarbonHp,0 mol m

–2 Photon fluence (cf. Tab. 3-9)IC ppm, mg L–1 Inorganic carbonIC – Internal conversion (Jablonski diagram)ISC – Inter system crossing (Jablonski diagram)IUPAC – International Union of Pure and Applied

ChemistrykM s

–1 Rate constant (first order)kN,M L mol

–1 s–1 Rate constant (second order) of reactionbetween molecules N and M

l m Lengthc), penetration depth, optical path-length, photoreaction zone

LP Hg lamp – Low-pressure mercury lampm kg MassM (MM) kg mol

–1 (SI) or g mol–1 Molar mass (the subscript M specifies asubstrate molecule M)d)

MO – Molecular orbitalMP Hg lamp – Medium-pressure mercury lampNA mol

–1 Avogadro constantNOM – Natural organic matterNp; N� (� specified) mol Amount of photonsOM – Organic matterou – Odor unitP W Radiant powerP (subscript) – PhotonPAHs – Polycyclic aromatic hydrocarbonsPCBs – Polychlorinated biphenylsPCDDs – Polychlorinated dibenzo-p-dioxinesPCDFs – Polychlorinated dibenzo-p-furanesPCO – Photocatalytic oxidationPCP – Pentachlorophenol (C6Cl5HO)Pel

in W Electric input powerPIEP – Production-integrated environmental

protectionPOP – Persistent organic pollutantppb (10–9 parts/unit) ppb Parts per billionppm (10–6 parts/unit) ppm Parts per millionppmv (obsolete) ppmv Parts per million by volumeQ� J Radiant energyR – Alkyl-skeleton of an organic moleculer e) Reaction rateRf – Reduction factor

Abbreviations and SymbolsXIV


ROS – Refractory organic substancesS – Singlet state (Jablonski diagram)SC – SemiconductorSi – Scavenger moleculeSOC – Semivolatile organic compoundsSUWOX – Super critical water oxidationt h, min, s TimeT K (SI) or�C TemperatureT – Triplet state (Jablonski diagram)TC ppm, mg L–1 Total carbonTOC ppm, mg L–1 Total organic carbontrans (superscript) – TransmittedUNEP – United Nations Environment ProgramUV – Ultraviolet (200 nm ≤ � ≤ 400 nm)V m3 (SI) or L Volumev (subscript) – Visiblevb – Valence bandvib – VibrationalVIS – Visible electromagnetic radiation= lightVOC – Volatile organic compoundVUV – Vacuum-UV (100 nm ≤ � ≤ 200 nm)X – Halogen�p mol s

–1 (Einstein s–1) Photon flow� – Quantum yield f)

V̇ g) m3 s–1 or L h–1 Volume flow rate�� m

2 mol–1 (SI) or L mol–1

cm–1, or M–1 cm–1Molar (decadic) absorption coefficient b)

� – Efficiency� – Quantum efficiency� nm Wavelength� Hz, s–1 Frequency�� cm–1 Wavenumber

a) Additional terms used for the description and measurement of electromagnetic radiation are col-lected in Tab. 3-9, abbreviations of water analytical parameters are summarized in Tab. 5-1, andabbreviations and definitions of design parameters (“figures-of-merit”) are given in Tab. 8-4.

b) Many authors prefer the symbol “M” for molar concentration, rather than mol L–1.c) To avoid any misinterpretations, the physical quantity length is symbolized by l in contrast to the

numerical value 1.d) M is also used in chemical equations to denote a molecule or substrate.e) The unit depends on the reaction order.f) To distinguish the symbol for quantum yield � from photon flow �p, it is printed italic (if pos-

sible).g) Many authors use other symbols e.g., F for flow rate.

Abbreviations and Symbols XV

Browsing the vast primary and secondary literature that deals with water or airtreatment processes and technologies very quickly leads to a point of dissatisfac-tion and confusion concerning vague interpretations of experimental results, reac-tion mechanisms, or descriptions of reactor specifications. Because water and airare essential to our life, they are of special interest not only to researchers and en-gineers but also to economists and many others. Thus, extra-scientific considera-tions such as media attention are enormous. Many of these activities generateconsiderable confusion related to water and its treatment technologies, especiallyin the case of photochemical methods.

From the chemist’s point of view, however, water in its purest form does not ex-ist in the environment. It is very difficult and costly to produce and has anoma-lous solvent properties, so that it is contaminated immediately by dissolving traceelements or compounds from its environment. On the other hand, “pure” air issimply a mixture of several gaseous compounds of well-known composition.

By thinking of nature as a huge photochemical reactor with the sun as an inten-sive source of electromagnetic radiation, the air as the gaseous component and wateras the liquid medium, the bridge to photochemical reactions in water and air is built.This led to the investigation of photo-induced and photo-initiated processes withinthese media. As a result of these understandings, photochemical technologies forwater and air treatment were developed over recent decades. Because of the interdis-ciplinary nature of this research area, which connects aqueous and gaseous chemis-try and photochemistry with engineering concepts, an almost Babylonian expansionof terms, definitions, designations and abbreviations has been observed, such asAOPs, AOTs, EOTs, EEO, EEM, ACM, ACO, H2O2-UV, H2O-VUV, photocatalysis, photo-oxidation, photo-initiated oxidation, fluence, “UV light”, “UV dose”, etc. Conse-quently, it is one objective of this book to outline, strictly define, and unify the cor-responding nomenclature used in the literature to describe the various processesand techniques (in accord with recommendations of the International Union of Pureand Applied Chemistry, IUPAC), and to address severe misinterpretations thatabound throughout the general literature, such as for example the misleading, oftenused and fundamentally incorrect term “UV catalyzed” oxidation.

Another important goal is the elaboration, clarification and discussion of theunderlying chemical, photophysical and photochemical processes and mecha-

1

Introduction

nisms, with distinct emphasis on the last, based on the historical development ofthe photon concept. Hence, the complexity arising from the diversity of reactionsin aqueous or in gaseous media with or without catalysts or auxiliary oxidants, inthe presence or absence of microorganisms, will be structured and classified onan accurate basis.

In addition, this task requires knowledge of the language of a chemist who isusually wild about chemical formulas and structures that are composed of linedrawings. Hoffmann and Laszlo (1991) enthusiastically outlined this concept.These authors stressed that the language of chemistry parallels the grammar ofour natural language (with several restrictions of course). This is also true if weintroduce the specialized language of photochemistry, so that the scheme of Hoff-mann and Laszlo may be extended to a “photochemical sentence” (excludingphotophysical deactivation processes):

Language: subject –– transitive verb –– objectChemistry: substrate –– reagent –– productPhotochemistry: substrate –– absorbed photon –– photoproduct

The interpretation of an absorbed photon as a specific reagent that transforms asubstrate under special conditions to a distinct photoproduct, i.e. which causes aphotochemical reaction, has an enormous impact on the understanding and de-sign of photochemical processes and their scaling-up. In addition, it clearly de-monstrates that light or UV radiation can never act as a catalyst, because the en-ergy of the absorbed photon is used to produce an electronically excited state of amolecule, and therefore its energy is dissipated and the photon is lost. Further-more, one should notice that the product of a chemical (thermal) reaction is notusually identical with the photoproduct that is produced in a photoreaction. Thisis a direct consequence of the higher energy introduced by photons into a molecu-lar entity compared with thermal chemistry, i.e. excited state versus ground statereactivity. This again has an important influence on the understanding of photo-chemical processes used for the purification and detoxification of water and air.

After having discussed the fundamentals of the interaction of UV/VIS radiationwith matter, the photochemical processes of water treatment will be analyzed in re-lation to the photochemistry of the oxidative auxiliaries. The behavior of the primaryand secondary reactive species (mainly oxygen containing radicals and carbon radi-cals, respectively) is outlined in detail. After a systematic classification of photo-in-itiated oxidations, reactions related to the used oxidants, catalysts and applied excita-tion wavelengths, a detailed description of photooxidation and photomineralizationof organic matter from a chemistry point of view follows. It includes the analysis ofthe level of reactive intermediates, the level of oxidation products and a discussion oftoxicological studies. Additionally, several recent research activities and potential ap-plications of novel incoherent excimer lamps including the expanding field of vacu-um-UV (VUV) photochemistry of water are reported in detail.

Another section of the book covers the engineering concepts based on the un-derlying photochemical and chemical processes. It assesses the different types of

Introduction2

photoreactors and the various influences on the performance of the process. Mostimportantly, the economic factors of photo-initiated oxidations are worked out ac-cording to the Bolton concept of design parameters (Bolton’s “figures-of-merit”)that are directly related to the observed degradation kinetics, and thus to the costof the advanced oxidation process (AOP).

Short reviews of the recent research activities into UV disinfection of water andair and of the UV treatment techniques of polluted air are enriched by the de-scription and discussion of several selected examples of published industrial appli-cations. Many questions related to the selection of UV processes will be answeredand common pitfalls referring to UV applications addressed.

Until now, many technical and research papers concerning photo-initiated treat-ment processes of water or air are almost useless for synoptic discussions due tothe lack of precise data describing the photoreactor, its components and a compre-hensive set of the analytical and engineering parameters of the system. Thus, adetailed analysis of the experimental information necessary for the correct descrip-tion of photoprocesses (for example in technical publications) will help to facili-tate future work and communication in this interdisciplinary field of research anddevelopment.

Thus, the motto of this book is, “to purify, irradiate!”

Reference

Hoffmann R, Laszlo P (1991) Darstellungen in der Chemie – die Sprache der Chemiker, An-gew. Chem. 103: 1–16; similar article in French: Hoffmann R, Laszlo P (1989) La Représenta-tion en Chimie, Diogène, No. 147: 24–54.

Acknowledgments

I wish to express my sincere gratitude to several companies and institutions thatprovided information concerning their products and research efforts. The follow-ing companies, institutions, and persons provided specific information for me:

• a.c.k. aqua concept GmbH (Karlsruhe, Germany), M. Sörensen: case studies anda photograph of a photoreactor.

• ABB (Baden, Switzerland), U. Kogelschatz: incoherent excimer lamps and corre-sponding emission spectra. Many stimulating discussions with Dr. Kogelschatz in-itiated research concerning water and air treatment with VUV/UV excimer lamps.

• C & C Consult (Schleiden/Eifel, Germany): R. S. Chatty: technical information,investigations, and a photograph of a mobile air treatment system.

• Calgon Carbon Inc. (Pittsburgh, PA, USA), W. Lem: photograph and descriptionof a photoreactor and treatment examples.

• Dr. Hönle AG UV-Technologie (Planegg/München, Germany), P. Wind: informa-tion and a photograph concerning the surface irradiation system used for bottlescrew cap disinfection.

Acknowledgements 3

• GMBU e.V. Gesellschaft zur Förderung von Medizin-, Bio- und Umwelt-Techno-logien, Fachsektion Sensorik (Jena, Germany), D. Faßler: electronic release ofthe Conference Proceedings of the 2nd International Conference on OxidationTechnologies for Water and Wastewater Treatment, May 28–31 (2000),Clausthal-Zellerfeld (Germany).

• HDN-Technik GmbH (Rednitzhembach, Germany), K. W. Hofmann: informa-tion concerning odor abatement (gaseous systems) and waste air treatment anda photograph of a photoreactor.

• Heraeus Noblelight AG (Kleinostheim, Germany), J. P. Schulz: product informa-tion and spectra of the low-pressure and medium-pressure mercury vapor lamptypes.

• Institute for Sanitary Engineering, Water Quality and Waste Management, Uni-versity of Stuttgart (Germany), E. Thomanetz: descriptions and photographs ofphotoreactors, and treatment examples.

• UMEX GmbH (Dresden, Germany), S. Johne: electronic release of the Confer-ence Proceedings of the First International Congress on Ultraviolet Technolo-gies, IUVA, June 14–16 (2001), Washington, DC; photoreactor specifications andphotographs of UMEX reactors.

• VitaTec UV-Systeme GmbH (Freigericht, Germany), M. Trageser: photographs ofphotoreactors and treatment examples.

• WaCo Wassertechnik Consult GmbH (Hamburg, Germany), O. Debus: supple-mentary information regarding the AOX elimination with a contact-free batchphotoreactor.

The editorial assistance of Wiley-VCH is also acknowledged.In addition, I wish to thank the Willy-Hager-Stiftung (Stuttgart, Germany) for

their financial support. This foundation arranged contacts with E. Thomanetz atthe Institute for Sanitary Engineering, Water Quality and Waste Management,University of Stuttgart. We had close discussions on the internal project resultsconcerning the development of AOTs. The exchange of stimulating ideas and thenumerous scientific discussions with Prof. Thomanetz during the past few yearswere extremely fruitful and encouraging to the planning and realization of thecurrent book project. He made many practical suggestions, and fascinating in-sights into the technical applications and problems of advanced oxidation technol-ogies were opened up.

Finally, yet importantly, I wish to acknowledge the direct support of James R.Bolton. He read the entire manuscript and offered critical and constructive com-ments, and made detailed suggestions concerning mechanistic interpretations andtechnical applications. James Bolton, Professor Emeritus of Chemistry, Universityof Western Ontario, Department of Chemistry (London ON, Canada), is currentlythe Executive Director of the International Ultraviolet Association (IUVA), AdjunctProfessor at the Department of Civil & Environmental Engineering, University ofAlberta (Edmonton AB, Canada), and he is the President of Bolton PhotosciencesInc. (Ayr ON, Canada).

Introduction4

Students and experts who concentrate seriously on research and developmentstrategies that are related to the interdisciplinary topics of UV radiation/light, theenvironment and technology are increasingly confronted with an enormous floodof information that is spread throughout the scientific and technical literature.This is especially the case since the introduction of the Internet, which enableseasy access to journalistic, and primary and secondary scientific literature. Hence,Tab. 1-1 summarizes several introductory and sophisticated links to Internet pagesof special interest to these research areas. The link collection of Tab. 1-1 should fa-cilitate the entry of newcomers into the complex field of ultraviolet (UV) radiationor light-induced environmental technologies and photochemical or photophysicalresearch concepts. In addition, it should help the researcher and developer to spe-cify their interests.

In this connection, it is worth mentioning that often scientists and engineersdo not differentiate correctly between the terms light and ultraviolet radiation ineveryday usage. The term “light” strictly stands for the visible part (VIS) of theelectromagnetic spectrum and it covers only a short wavelength segment between380 nm ≤ � ≤ 780 nm. Nonetheless, the term “UV-light” is used in the common vo-cabulary of (photo)scientists and engineers, but for the sake of clarity, it should beavoided. In this book, the abbreviation UV/VIS is used to describe UV radiationand light. However, the term “radiation” has a negative public reaction (it means“high-energy radiation”, something strange and dangerous) and it should be usedcarefully in the public domain.

The cross sections of the subject areas UV radiation/light and technology, UVradiation/light and environment, and environment and technology (Fig. 1-1) areinterrelated and extraordinarily versatile with respect to their future developmentpotentials. Therefore, the use of light and UV radiation in diverse applicationsrepresents one of the advanced technologies of the 21st century. This is particular-ly the case for the utilization of solar energy and any research activities that arerelated to climate protection technologies.

This book concentrates on the basic principles, reaction mechanisms and engi-neering concepts of technologies that use UV radiation (or light) as a selective re-agent for the cleavage of chemical bonds and hence for the destruction of un-wanted chemicals or microorganisms. Accordingly, these methods include UV

5

1

AOPs and AOTs

1 AOPs and AOTs6

Tab. 1.1 Link collection of Internet pages comprising research, development, and general infor-mation in the field of UV radiation/light, environment and technology (all links have been testedregularly for their actual status)

Index Source/description Link

Air quality guidelines, drink-ing water quality, water re-sources

World Health Organization(WHO)

http://www.who.int/home-page

Bibliography on heteroge-neous photocatalysisa)

National Renewable EnergyLaboratory

http://www.ott.doe.gov/coolcar/pdfs/water_air2.pdf

Chemical nomenclature International Union of Pureand Applied Chemistry

http://www.iupac.org

Chemical structure database,structure viewing support byChemscape Chime

U.S. National Library of Medi-cine, National Institute ofHealth

http://sis.nlm.nih.gov/Chem/ChemMain.html

Chemical-physical data, litera-ture

Database catalog for chemists http://www.chemie-datenbanken.de

Data collections of organicand small inorganic com-pounds

National Institute of Stan-dards and Technology (NIST)

http://webbook.nist.gov

Drinking water standards ofthe U.S.

EPA Office of Water http://www.epa.gov/safewater/

Economy, technology, profes-sion and other online services

German Machinery and PlantManufacturers Association(VDMA) b)

http://www.vdma.de

Environmental policy and re-ports

Federal Environment Ministry(BMU, Germany)

http://www.bmu.de/

Environmental products, tech-nology and services, global di-rectory

ECO Services International(Switzerland)

http://eco-web.com

European Union Law andother activities

European Union On-line http://europa.eu.int

Federal Legislation of Ger-many

Federal Law Gazette(Germany)

http://www.bundesgesetzblatt.de

Gas and water relevant topics,technical press releases ofbrbvc)

Federal Association of Gasand Water Companies/Asso-ciation of Pipework Construc-tors (Germany)

http://www.rbv-koeln.de/figawa/index.php4http://www.rbv-koeln.de

German Standards German Institute of Standar-dization (DIN)

http://www.din.de

Glossary of terms used inphotochemistry, full text inpdf format

Report of the IUPAC d) Photo-chemistry Commission (Ver-hoeven, 1996)

http://www.unibas.ch/epa/texts.html

1 AOPs and AOTs 7

Tab. 1.1 (continued)


Hydrogen peroxide: applica-tions to water, wastewater andhazardous waste treatment

US Peroxide http://www.h2o2.com

International chemical safetycards

National Institute for Occupa-tional Safety and Health

http://www.cdc.gov/niosh/ipcs/icstart.html

International conference Advanced Oxidation Technolo-gies for Water and Air Reme-diation (AOTs)

http://www.aotsconference.com

International conference Solar energy research and ap-plied photochemistrye)

http://photoenergy.org

International conference, re-search

Clausthaler Umwelttechnik-Institut GmbH

http://www.cutec.de

International standards andguidelines

International Organization forStandardization (ISO)

http://www.iso.ch/iso/en/ISOOnline.frontpage

Journal finder and journalsearch, journal service

Wiley Interscience http://www3.interscience.wiley.com

Journal tables of contents:regular email service

Elsevier http://www.elsevier.nl

Journals and books, subjectsearch and alerting service(email)

Wiley-VCH http://www.wiley-vch.de

Journals and publishers ChemPort http://www.chemport.org

Laser development and appli-cations, optics, photonics andimaging

The International Society forOptical Engineering (SPIE)

http://www.spie.org

Laws, regulations, informa-tion

Environmental ProtectionAgency (EPA)

http://www.epa.gov

Light and lighting, radiation International Commission onIllumination (CIE)f)

http://www.cie.co.at/ciecb

Light measurement hand-bookg)

International Light, Inc. http://www.intl-light.com/handbook

Literature search, general KVK-virtual catalog: books andjournals

http://www.ubka.uni-karls-ruhe.de/kvk.html

Literature search: photochem-istry and related fields

Photochemistry/photobiologydatabase, access to photo-chemistry literature (Grabnerand Kuti, 1997)

http://www.chemres.hu/pchem

Odor assessment, annoyanceand research

OdourNet http://odournet.com

1 AOPs and AOTs8



Organic photochemistry Home page of Turro’s h) re-search group

http://turmac13.chem.columbia.edu

Original publications of photo-science, full text of papers inpdf format, online journal

International Journal of Photoe-nergyi)

http://www.photoenergy.org/ijp

Ozone and its applications International Ozone Associa-tion (IOA)

http://www.int-ozone-assoc.org

Persistent organic pollutants(POPs)

POPs related United NationsEnvironment Program

http://irptc.unep.ch/pops/

Photochemistry activities European Photochemistry As-sociation (EPA)

http://www.unibas.ch/epa

Photochemistry activities Inter-American PhotochemicalSociety (I-APS)

http://www.chemistry.mcmaster.ca/~iaps

Radiation chemistry data-bases: radical and excited stateprocesses, extensive data com-pilations

The Radiation Chemistry DataCenter at the Notre Dame Ra-diation Laboratory Database

http://www.rcdc.nd.edu/icabr/RCDC.html

Radical reactions and rate con-stants (Buxton et al., 1988):eaq

– , H•, •OH, O•–, 1O2

The Radiation Chemistry DataCenter at the Notre Dame Ra-diation Laboratory Database

http://www.rcdc.nd.edu/Solnkin2

Regulations and standards re-lated to environment and en-vironmental technology

Environmental legislation(Germany)

http://www.umwelt-online.de/regelwerk/index.htm

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Federal Ministry of Educationand Research (BMBF, Ger-many)

http://www.bmbf.de

Search engine: only web sitescontaining scientific informa-tion

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Security data of chemicals etc. Federal Institute for Health-Oriented Consumer Protec-tion and Vetenary Medicine inBerlin (Germany)

http://www.bgvv.de

Solar radiation, relevant glos-saries

Renewable Resource DataCenter (RReDC)

http://rredc.nrel.gov

Technical standards for indus-tries

American Society for Testingand Materials (ASTM)

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Technical standards, gas andwater treatment

German Association of Gasand Water Experts (DVGW)

http://www.dvgw.de

Toxicological profile informa-tion sheet

Agency for Toxic Substancesand Disease Registry

http://www.atsdr.cdc.gov/toxpro2.html

1 AOPs and AOTs 9



Toxicology, environmentalhealth, chemical information

Specialized Information Ser-vices, National Library of Med-icine

http://sis.nlm.nih.gov/index.html

Ultraviolet technologies, appli-cations, research

International Ultraviolet Asso-ciation (IUVA)

http://www.iuva.org

Ultraviolet technologies: exper-tise

Bolton Photosciences Inc. http://www.boltonuv.com

UNEP chemicals United Nations EnvironmentProgram (UNEP)

http://irptc.unep.ch

Water activities in Europe European Water Association(EWA)

http://www.ewaonline.de

Water activities in USA American Water Works Asso-ciationAWWA Research FoundationWater Environment Federa-tion

http://www.awwa.org

http://www.awwarf.comhttp://www.wef.org

Water activities, international,publications

International Water Associa-tion

http://www.iawq.org.uk

Water and wastewater indus-try news

U.S. Water News, Inc. http://www.uswaternews.com

Water management indus-tries, search engine

Dutch journal H2O http://www.h2o-scanner.com

Water programs EPA’s Office of Water http://www.epa.gov/ow

Water technology online National Trade PublicationsInc.

http://www.watertechonline.com

Water, marketplace for thewater industry

VerticalNet web site http://www.wateronline.com

Water, photochemistry, andchemistry in general

German Chemical Society anddivisions (GdCh)

http://www.gdch.de

Water, versatile information j) Water quality http://www.waterquality.de

Water, wastewater and wastetreatment

German Association forWater, Wastewater and Waste

http://www.atv.de

a) M Blake (1999) Bibliography of Work on the Heterogeneous Photocatalytic Removal of HazardousCompounds from Water and Air, update No. 3, January 1999: 154 pp, also available from the Na-tional Technical Information Service, Springfield, VA 22161.

b) VDMA: Verband Deutscher Maschinen- und Anlagenbau e. V.c) brbv: Berufsförderungswerk des Rohrleitungsbauverbandes.d) IUPAC: International Union of Pure and Applied Chemistry.e) Photoenergy Center, Ain Shams University, Cairo.f) CIE (French title): Commission Internationale de l’Eclairage.g) by A Ryer (1997), International Light, Inc.h) NJ Turro, Columbia University, New York.i) edited by MSA Abdel-Mottaleb (since 1999).j) collected by H Willmitzer.

techniques for the treatment of contaminated media water and air, mostly in thepresence of oxidative auxiliaries or photocatalysts, leading to their efficient detoxi-fication, purification or remediation, and disinfection, including odor abatementstrategies and surface treatment (Fig. 1-2). However, the most obvious goal ofthese photochemical technologies is to attain water and air quality standards thatfulfill government regulations according to emission ordinances.

Ultimately, if necessary the complete mineralization of the organic carbon con-tent of water or air can be achieved according to the general Eq. 1-1. In general,the process of photomineralization of organic contaminants describes the oxida-tion of organic carbon atoms to carbon dioxide or carbonate species (CO2, H2CO3,HCO3

–, CO32–) initiated by electromagnetic radiation. Simultaneously, hydrogen

atoms are converted into water and heteroatoms X of organic molecules are trans-

1 AOPs and AOTs10

Fig. 1.1 Some interdisciplinary research and development areas relatedto the terms UV radiation/light, environment and technology.

Fig. 1.2 Main objectives of photochemical technologies for the UV treatment of water and air.

formed into the corresponding mineral acids HX= HCl, HBr, HNO3, HNO2,H2SO4, etc.

CnHmXzh��O2� nCO2 � �m � z��2H2O � zHX (1-1)

For example, 2,4-dichlorophenol (C6H4Cl2O) mineralizes stoichiometrically accord-ing to Eq. 1-2 (Bolton and Cater, 1994). Even pollutants containing inorganic car-bon such as cyanide (CN–) can be oxidized to less toxic compounds by adequateirradiation methods.

All of these photochemical processes and related technologies are usually classi-fied as Advanced Oxidation Processes (AOPs) (Glaze et al., 1987) and AdvancedOxidation Technologies (AOTs) or sometimes as Enhanced Oxidation Processes(EOPs). The underlying oxidative reaction mechanisms are basically imitations ofnatural photo-initiated processes that take place in sunlit surface waters or in theEarth’s atmosphere. They rely mainly on the formation of reactive and short-livedoxygen containing intermediates such as hydroxyl radicals (•OH) and they exploitthe high reactivity of these species. The hydroxyl radical is a powerful oxidant anda short lived, highly reactive, and non-selective reagent that is easy to produce(Fig. 1-3). It has electrophilic properties and its reactions with appropriate sub-strate molecules are kinetically controlled usually exhibiting very high second or-der rate constants, which are often close to (or even above) the diffusion-con-

1 AOPs and AOTs 11

(1-2)

Fig. 1.3 Some characteris-tic features of the hydroxylradical.

trolled limit (von Sonntag, 1996). Kinetic reaction control refers to competing irre-versible reactions in which the product composition is determined by the relativerates of product formation. Furthermore, the •OH radical is a ubiquitous transientspecies in nature and it is a very important agent in numerous human diseasesor disorders and in the aging process (Knight, 1998).

The transfer of such natural processes into technical dimensions requires meth-ods for the efficient production of the so-called “free” hydroxyl radicals at suffi-cient concentrations from appropriate precursors. Besides photochemical and so-lar photocatalytic processes many other innovative technologies have been pro-posed for treating liquid or gaseous wastes around abandoned sites (Freeman andHarris, 1995) and are currently under intensive investigation (Fig. 1-4), for exam-ple catalytic processes (e.g. Hofmann et al., 2000), electrochemical oxidation of or-ganic water contaminants (Galla et al., 1999) and non-thermal plasma treatmentmethods for exhaust air processing. Further AOPs of special interest include sono-lysis (Ince et al., 2001, Hua and Hoffmann, 1997), X-ray irradiation and -radiolysis(Ferradini and Jay-Gerin, 1999), electron beam irradiation (Pikaev, 2000, Cooper etal., 1998, Getoff, 1993) of contaminated water, radiation chemistry in general (Jo-nah and Rao, 2001) and the SUWOX process (Schmieder and Abeln, 1999) thatuses super critical water conditions (Kritzer and Dinjus, 2001) for the oxidation oforganic water contaminants, and many other remediation technologies (Freemanand Harris, 1995).

Over several years of extensive research and development efforts in these fieldsa wide-ranging knowledge of environmental applications has accumulated, includ-ing analytical methodologies and process engineering of photochemical reactions,e.g. for the generation of •OH radicals. This fact manifests itself in the countlessscientific and technical publications in various journals that deal with environ-mental technologies and sustainable development.

1 AOPs and AOTs12

Fig. 1.4 The family of advanced oxidation technologies for water and air remediation.

photochemical purification of water and air · reaction kinetics. this idea is thought to be very...

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