handbook of membrane separations chemical pharmaceutical food and biotechnological applications

Handbook ofMembraneSeparations

Chemical, Pharmaceutical, Food,and Biotechnological Applications

Pabby et al./Handbook of Membrane Separations 9549_C000 Final Proof page i 21.5.2008 7:54pm Compositor Name: BMani

Pabby et al./Handbook of Membrane Separations 9549_C000 Final Proof page ii 21.5.2008 7:54pm Compositor Name: BMani

Handbook ofMembraneSeparations

Chemical, Pharmaceutical, Food,and Biotechnological Applications

Edited by

Anil K. PabbySyed S. H. Rizvi

Ana Maria Sastre

CRC Press is an imprint of theTaylor & Francis Group, an informa business

Boca Raton London New York

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CRC PressTaylor & Francis Group6000 Broken Sound Parkway NW, Suite 300Boca Raton, FL 33487-2742

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Library of Congress Cataloging-in-Publication Data

Handbook of membrane separations : chemical, pharmaceutical, food, and biotechnological applications / editor(s), Anil Kumar Pabby, Syed S.H. Rizvi, and Ana Maria Sastre.

p. ; cm.Includes bibliographical references.ISBN-13: 978-0-8493-9549-9 (hardcover : alk. paper)ISBN-10: 0-8493-9549-6 (hardcover : alk. paper)1. Membrane separation--Handbooks, manuals, etc. I. Pabby, Anil Kumar. II. Rizvi, S. S. H., 1948- III. Sastre, Ana Maria. [DNLM: 1. Membranes, Artificial. 2. Biotechnology--methods. 3. Ultrafiltration. TP 159.M4 H236 2008]

TP248.25.M46H35 2008660.2842--dc22 2008009730

Visit the Taylor & Francis Web site athttp://www.taylorandfrancis.comand the CRC Press Web site athttp://www.crcpress.com

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ContentsForeword ..................................................................................................................................................................................... ixPreface......................................................................................................................................................................................... xiEditors ....................................................................................................................................................................................... xiiiContributors ............................................................................................................................................................................... xv

SECTION I Membrane Applications in Chemical and PharmaceuticalIndustries and in Conservation of Natural Resources

Chapter 1 Membrane Applications in Chemical and Pharmaceutical Industries and in Conservationof Natural Resources: Introduction....................................................................................................................... 3

Ana Maria Sastre, Anil Kumar Pabby, and Syed S.H. Rizvi

Chapter 2 Application of Membrane Contactors as Mass Transfer Devices........................................................................ 7

A. Sengupta and R.A. Pittman

Chapter 3 Membrane Chromatography............................................................................................................................... 25

M.E. Avramescu, Z. Borneman, and M. Wessling

Chapter 4 Membranes in Gas Separation............................................................................................................................ 65

May-Britt Hgg

Chapter 5 Pervaporation: Theory, Practice, and Applications in the Chemical and Allied Industries............................. 107

Vishwas G. Pangarkar and Sangita Pal

Chapter 6 Current Status and Prospects for Ceramic Membrane Applications................................................................ 139

Christian Guizard and Pierre Amblard

Chapter 7 Membrane Technologies and Supercritical Fluids: Recent Advances ............................................................. 181

D. Paolucci-Jeanjean, G.M. Rios, and S. Sarrade

Chapter 8 Techniques to Enhance Performance of Membrane Processes ........................................................................ 193

A.G. Fane and S. Chang

Chapter 9 Separation and Removal of Hydrocarbons Using Polymer Membranes ......................................................... 233

S.I. Semenova

Chapter 10 Zeolite Membranes: Synthesis, Characterization, Important Applications, and Recent Advances ................. 269

M. Arruebo, R. Mallada, and M.P. Pina

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Chapter 11 Membrane Fouling: Recent Strategies and Methodologies for Its Minimization............................................ 325

Mattheus F.A. Goosen, S.S. Sablani, and R. Roque-Malherbe

Chapter 12 Membrane Extraction in Preconcentration, Sampling, and Trace Analysis..................................................... 345

Jan ke Jnsson

Chapter 13 Hybrid Liquid Membrane Processes with Organic Water-Immiscible Carriers (OHLM):Application in Chemical and Biochemical Separations ................................................................................... 371

Vladimir S. Kislik

Chapter 14 Advancements in Membrane Processes for Pharmaceutical Applications....................................................... 409

Ralf Kuriyel, Masatake Fushijima, and Gary W. Jung

Chapter 15 Membranes in Drug Delivery........................................................................................................................... 427

Mario Grassi

Chapter 16 Bio-Responsive Hydrogel Membranes............................................................................................................. 473

John Hubble and Rongsheng Zhang

SECTION II Membrane Applications in Biotechnology,Food Processing, Life Sciences, and Energy Conversion

Chapter 17 Membrane Applications in Biotechnology, Food Processing, Life Sciences, and EnergyConversion: Introduction .................................................................................................................................. 495

Syed S.H. Rizvi

Chapter 18 Ultraltration-Based Protein Bioseparation...................................................................................................... 497

Raja Ghosh

Chapter 19 Membrane Distillation in Food Processing ...................................................................................................... 513

Sanjay Nene, Ganapathi Patil, and K.S.M.S. Raghavarao

Chapter 20 Applications of Membrane Separation in the Brewing Industry ..................................................................... 553

Carmen I. Moraru and Ernst Ulrich Schrader

Chapter 21 Developments of Bipolar Membrane Technology in Food and Bio-Industries............................................... 581

Gerald Pourcelly and Laurent Bazinet

Chapter 22 Applications of Membrane Technology in the Dairy Industry ........................................................................ 635

Philipina A. Marcelo and Syed S.H. Rizvi

Chapter 23 Microporous Membrane Blood Oxygenators ................................................................................................... 671

S.R. Wickramasinghe and B. Han

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Chapter 24 Transporting and Separating Molecules Using Tailored Nanotube Membranes ............................................. 693

Punit Kohli and Charles R. Martin

Chapter 25 Use of Emulsion Liquid Membrane Systems in Chemical and Biotechnological Separations ....................... 709

Jilska M. Perera and Geoff W. Stevens

Chapter 26 Membrane Electroporation and Emerging Biomedical Applications............................................................... 741

K.P. Mishra

Chapter 27 Proton-Conducting Membranes for Fuel Cells................................................................................................. 759

Vineet Rao, K. Andreas Friedrich, and Ulrich Stimming

SECTION III Membrane Applications in Industrial Waste Management(Including Nuclear), Environmental Engineering,and Future Trends in Membrane Science

Chapter 28 Membrane Applications in Industrial Waste Management (Including Nuclear), EnvironmentalEngineering, and Future Trends in Membrane Science: Introduction ............................................................. 823

Ana Maria Sastre and Anil Kumar Pabby

Chapter 29 Treatment of Radioactive Efuents: Introduction, Fundamentals, and Scope of DifferentMembrane Processes ........................................................................................................................................ 827

B.M. Misra and V. Ramachandhran

Chapter 30 Radioactive Waste Processing: Advancement in Pressure-Driven Processesand Current World Scenario............................................................................................................................. 843

Grazyna Zakrzewska-Trznadel

Chapter 31 Liquid Membrane-Based Separations of Actinides.......................................................................................... 883

P.K. Mohapatra and V.K. Manchanda

Chapter 32 Reverse Osmosis-Based Treatment of Radioactive Liquid Wastes Generated in Hospital Facilityand in Steel Industry: Case Studies.................................................................................................................. 919

M. Sancho, J.M. Arnal, G. Verd, and J. Lora

Chapter 33 Evaluation of Membrane-Based Processing of Radioactive Nuclear Plant Waste: Case Studies ................... 933

Anil Kumar Pabby, S.K. Gupta, S.R. Sawant, N.S. Rathore, P. Janardan,R.D. Changrani, and P.K. Dey

Chapter 34 Application of Donnan Membrane Process for Recovery of Coagulants from WaterTreatment Residuals ......................................................................................................................................... 945

Prakhar Prakash and Arup K. SenGupta

Chapter 35 Utilization of Membrane Processes in Treating Various Efuents Generatedin Pulp and Paper Industry ............................................................................................................................... 981

Mika Mnttri and Marianne Nystrm

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Chapter 36 Membrane Bioreactors for Wastewater Treatment......................................................................................... 1007

Eoin Casey

Chapter 37 Membrane-Assisted Solvent Extraction for the Recovery of Metallic Pollutants: ProcessModeling and Optimization............................................................................................................................ 1023

Inmaculada Ortiz and J. Angel Irabien

Chapter 38 Membrane Contactors for Gaseous Streams Treatments ............................................................................... 1041

Alessandra Criscuoli and Enrico Drioli

Chapter 39 Strip Dispersion Technique: Application for Strategic and Precious Metal Separationand Treatment of Wastewater Streams........................................................................................................... 1057

Anil Kumar Pabby, S.C. Roy, J.V. Sonawane, F.J. Alguacil, and Ana Maria Sastre

Chapter 40 Electrically Enhanced Membrane Separations and Catalysis......................................................................... 1071

V.M. Linkov, B.J. Bladergroen, and A.M. Maluleke

Chapter 41 Membrane Processes for Treatment of Industrial Tannery Efuents: A Case Study .................................... 1087

A. Bdalo, E. Gmez, and A.M. Hidalgo

Chapter 42 New Developments in Nanoltration Technology: A Case Study on Recoveryof Impurity-Free Sodium Thiocyanate for Acrylic Fiber Industry................................................................. 1101

S. Sridhar and B. Smitha

Chapter 43 Future Progresses in Membrane Engineering................................................................................................. 1131

Enrico Drioli and Enrica Fontananova

Index...................................................................................................................................................................................... 1147

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ForewordDuring the middle of the last century, when the rst synthetic membrane with tailor-made separation properties becameavailable, a multitude of technically and commercially interesting applications were identied. Today, 50 years later,membranes and membrane processes have indeed become valuable tools for the separation of molecular mixtures. They arethe key components in articial organs and in devices for the controlled release of active agents, or in energy conversion andstorage systems. Seawater and brackish water desalination using reverse osmosis and electrodialysis are energy efcient andhighly economic processes for large-scale production of potable water. Micro- and ultraltration are used for the production ofhigh-quality industrial water and for the treatment of industrial efuents. Blood detoxication by hemodialysis and hemoltra-tion improves the quality of life for more than 1.3 million people suffering from acute and chronic renal failure. Membraneprocesses have found a multitude of applications in chemical and pharmaceutical industries as well as in food processing andbiotechnology. They are used on a large scale in gas separation and as tools in analytical laboratories. Todays membrane-basedindustry is serving a rapidly growing multibillion euro market with a large number of products and processes. The developmentof membranes with improved properties will most likely increase the importance of membranes and membrane processes in agrowing number of applications for the sustainable growth of modern industrial societies.

The term membrane refers not to a single item, but covers a large variety of structures and materials with very differentproperties. The same is true for membrane processes, which can be very different in the way they function. However, allmembranes and membrane processes have one feature in common, i.e., they can perform the separation of certain molecularmixtures effectively and economically at ambient temperature, and without any toxic or harmful reaction by-products.

In the early days of membrane science and technology, research was mainly concentrated on elucidating the membranemass transport mechanism and on developing membrane structures with specic mass transport properties. The fundamentalsof most membrane processes and membrane preparation procedures are described in great detail in a large number ofpublications in various scientic journals and in several excellent textbooks. However, the application of membranes andmembrane processes is much less comprehensively covered in todays literature. Only a relatively small number of applicationsof membrane processes such as reverse osmosis, micro- and ultraltration, and gas separation and pervaporation are treated intextbooks and reference books. A large number of interesting membrane applications in the food and drug industry, in chemicaland electrochemical synthesis, and in articial organs are often not adequately treated in the membrane-related literature, butare published in journals specic for certain industries, which are outside of the interest of many membrane scientists.Furthermore, application-oriented membrane studies that are often carried out in industrial enterprises are described only aspatents, or are not published at all. Therefore, it is difcult to obtain a reasonably complete overview of the very large andheterogeneous eld of membrane applications without reading a number of very different journals and patents where most ofthe publications are not really membrane related.

The aim ofHandbook of Membrane Separations: Chemical, Pharmaceutical, Food, and Biotechnological Applications is toll the gap in the presently available membrane literature by providing a comprehensive discussion of membrane applications inthe chemical, food, and pharmaceutical industries, in biotechnology, and in the treatment of toxic industrial efuents. Theapplications of membranes in different areas are described by scientists and engineers who not only are experts in membranescience and technology but also have extensive experience in the specic eld of membrane application. This book is notcompetitive, but rather complementary to other textbooks and handbooks on membrane science and technology presentlyavailable in the market. It provides enough background information on the various membrane components and processes toevaluate their potential applications without a detailed treatment of the fundamental aspects of membrane mass transport theoriesand membrane structure development. The book should, therefore, be of great value to scientists and engineers who are notnecessarily membrane experts but are interested in using membrane processes in solving specic separation and mass transportproblems. It is equally suited for the newcomers in the eld of membrane science as for engineers and scientists, who do havebasic knowledge inmembrane technology but are interested in obtainingmore information on specic present and potential futuremembrane applications. It also provides an excellent base for courses and lectures in postgraduate education.

Professor Heiner StrathmannUniversity of Stuttgart

Germany

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PrefaceDuring the past two decades, membrane technology has grown into an accepted unit operation for a wide variety of separationsin industrial processes and environmental applications. Tighter environmental legislation calls for equipment that is able to dealwith the removal of components across a wide range of concentration levels and that offers considerable exibility andefciency. Membrane technology rst became important during the 1960s and 1970s in water treatment and in processes suchas reverse osmosis, ultraltration, dialysis, electrodialysis, and microltration. During the 1980s, membrane technology beganto be applied on a large scale in the eld of gas purication. The successful introduction of membrane technology in these eldswas mainly the result of the development of reliable and selective polymeric membranes.

There are a number of reference publications in the eld of membrane technology, such as handbooks, monographs, andcompendia of conference and workshop proceedings. The relative abundance of such works begs the questions, Whyanother? and How will this one be different? These questions are probably best answered by considering what theHandbook of Membrane Separations: Chemical, Pharmaceutical, Food, and Biotechnological Applications has to offer. Thehandbook covers the full spectrum of membrane technology and discusses its advancement and applications in a series ofchapters written by experts, prominent researchers, and professionals from all over the world.

The handbook is divided into three main sections: The rst section deals with membrane applications in chemical andpharmaceutical industries, and in conservation of natural resources; the second section covers membrane applications inbiotechnology, food processing, life sciences, and energy conversion. Finally, the third section deals with membraneapplications in industrial waste management (including nuclear), environmental engineering, and future trends in membranescience. Each section is divided into chapters that deal with the subject matter in depth and focus on cutting-edge advancementsin the eld. Several authors were commissioned to write the chapters under the supervision of the editors, and each chapter waspeer-reviewed for content and style before it was accepted for publication. The aim was to maintain the perspective of apractical handbook rather than merely a collection of review chapters.

The editors would like to acknowledge the contributions of a number of authors and institutions that have played a majorrole in drafting the handbook from conception to publication. The handbook would not have been possible without their input.These contributors are leading experts in their elds and bring a great wealth of experience to this book. The editors would alsolike to acknowledge the efforts of the reviewers who devoted their valuable time to revising the chapters before the deadlinesand suggested improvements to maintain the high standard of the handbook. Finally, we would like to acknowledge the supportof our home institutions at every stage in the handbooks conception: the Bhabha Atomic Research Centre, Mumbai, India;Cornell University, Ithaca, New York; and the Universitat Politcnica de Catalunya, Barcelona, Spain.

Anil Kumar PabbySyed S.H. Rizvi

Ana Maria Sastre

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EditorsAnil Kumar Pabby is afliated with one of the pioneering research centers ofIndia, the Bhabha Atomic Research Centre (Department of Atomic Energy),Tarapur, Mumbai, Maharashtra. He received his PhD from the University ofMumbai and subsequently completed his postdoctoral research at the UniversitatPolitcnica de Catalunya, Barcelona, Spain. Dr. Pabby has more than 150publications to his credit including 4 book chapters and a patent on nondisper-sive membrane technology. He was invited to join the team of associate editorsat the Journal of Radioanalytical and Nuclear Chemistry during 20022005. Hehas also served as consultant to the International Atomic Energy Agency (IAEA)for developing a technical document on the application of membrane technolo-gies for liquid radioactive waste processing. Dr. Pabby has been a regularreviewer for several national and international journals and also serves on theeditorial board of various journals. His research interest includes pressure-drivenmembrane processes, nondispersive membrane techniques, extraction chromato-graphy, solvent extraction, and macrocyclic crown compounds. In 2003,

Dr. Pabby was elected fellow of the Maharashtra Academy of Sciences (FMASc) for his contribution to membrane scienceand technology. In 2005, he received the prestigious Tarun Datta Memorial Award (instituted by Indian Association for NuclearChemists and Allied Scientists) for his outstanding contribution to nuclear chemistry and radiochemistry.

Syed S.H. Rizvi is an international professor of food process engineering and hasserved as director of graduate studies at the Cornell Institute of Food Science,Cornell University, Ithaca, New York. He has a PhD from Ohio State University,an MEng (chemical engineering) from the University of Toronto, and a BTechfrom Panjab University, India. Dr. Rizvi teaches courses devoted to engineeringand processing aspects of food science and related biomaterials. His laboratory isengaged in research on experimental and theoretical aspects of bioseparationprocesses using supercritical uids and membranes, high-pressure extrusion withsupercritical carbon dioxide, physical and engineering properties of biomaterials,and novel food processing technologies. An invention of Cornell researchers, andsubsequently patented, supercritical uid extrusion offers several advantages overthe conventional high-shear cooking extrusion and is being used to investigate thedynamics of the process and the mechanics of the microcellular extrudatesgenerated for both food and nonfood applications. A major long-term goal is to

develop new and improved unit operations for value-added processing of food and biomaterials. Derivative goals include newtechniques for measurement and control of processes and properties for industrial applications. Dr. Rizvi has published more than140 technical papers, coauthored=edited 6 books, served on the editorial board of several journals, and holds 7 patents.

Ana Maria Sastre is a professor of chemical engineering at the UniversitatPolitcnica de Catalunya (Barcelona, Spain), where she has been teachingchemistry for more than 28 years. She received her PhD from the AutonomousUniversity of Barcelona in 1982 and has been working for many years inthe eld of solvent extraction, solvent impregnated resins, and membranetechnology.

She was a visiting fellow at the Department of Inorganic Chemistry, theRoyal Institute of Technology, Sweden, during 19801981 and carried outpostdoctoral research from October 1986 to April 1987 at Laboratoire de ChimieMinerale, Ecole Europeenne des Hautes Etudes des Industries Chimiques deStrasbourg, France. Professor Sastre has more than 190 journal publications andmore than 80 papers in international conferences. Dr. Sastre also holds fourpatent applications, guided 11 PhD and 16 master thesis students, and is a

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reviewer of many international journals. In 2003, she was awarded the Narcis Monturiol medal for scientic and technologicalmerits, given by the Generalitat de Catalunya for her outstanding contribution to science and technology.

Professor Sastre was the head of the chemical engineering department from 1999 to 2005 and is presently vice rector (vicechancellor) for academic policy at the Universitat Politcnica de Catalunya.

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Contributors

F.J. AlguacilCentro Nacional de Investigaciones MetalrgicasConsejo Superior de Investigaciones CienticasCiudad UniversitariaMadrid, Spain

Pierre AmblardTechno-MembranesParc Scientique AgropolisMontpellier, France

J.M. ArnalChemical and Nuclear Engineering DepartmentPolytechnic University of ValenciaValencia, Spain

M. ArrueboDepartment of Chemical and EnvironmentalEngineering

University of ZaragozaZaragoza, Spain

M.E. AvramescuMembrane Technology GroupFaculty of Science and TechnologyUniversity of TwenteEnschede, the Netherlands

Laurent BazinetInstitute of Nutraceuticals and Functional FoodsDepartment of Food Sciences and NutritionLaval UniversityLaval, Qubec, Canada

B.J. BladergroenSouth African Institute for AdvancedMaterials Chemistry

University of the Western CapeBellville, South Africa

A. BdaloDepartamento de Ingeniera QumicaUniversidad de Murcia, Campus de EspinardoMurcia, Spain

Z. BornemanMembrane Technology GroupFaculty of Science and TechnologyUniversity of TwenteEnschede, the Netherlands

Eoin CaseySchool of Chemical and Bioprocess EngineeringUniversity College DublinDublin, Ireland

S. ChangGlobal Product Development, UF=MBR TechnologyGE Water & Process TechnologiesOakville, Ontario, Canada

R.D. ChangraniNuclear Recycle GroupBhabha Atomic Research CentreTarapur, Mumbai, Maharashtra, India

Alessandra CriscuoliResearch Institute on Membrane TechnologyUniversity of CalabriaRende, Cosenza, Italy

P.K. DeyNuclear Recycle GroupBhabha Atomic Research CentreTarapur, Mumbai, Maharashtra, India

Enrico DrioliResearch Institute on Membrane TechnologyUniversity of CalabriaRende, Cosenza, ItalyandDepartment of Chemical Engineering and MaterialsUniversity of CalabriaRende, Cosenza, Italy

A.G. FaneUNESCO Centre for Membrane Science and TechnologyUniversity of New South WalesSydney, New South Wales, AustraliaandSingapore Membrane Technology CentreNanyang Technological UniversitySingapore

Enrica FontananovaResearch Institute on Membrane TechnologyUniversity of CalabriaRende, Cosenza, ItalyandDepartment of Chemical Engineering and MaterialsUniversity of CalabriaRende, Cosenza, Italy

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K. Andreas FriedrichGerman Aerospace CenterElectrochemical Energy TechnologyStuttgart, Germany

Masatake FushijimaCrossow Technology, SLSPall CorporationPort Washington, New York

Raja GhoshDepartment of Chemical EngineeringMcMaster UniversityHamilton, Ontario, Canada

E. GmezDepartamento de Ingeniera QumicaUniversidad de MurciaCampus de EspinardoMurcia, Spain

Mattheus F.A. GoosenOfce of ResearchAlfaisal UniversityRiyadh, Saudi Arabia

Mario GrassiDepartment of Chemical, Environmental, and RawMaterials Engineering

University of TriesteTrieste, Italy

Christian GuizardLaboratoire de Synthse et Fonctionnalisation desCramiques

Saint Gobain CREECavaillon, France

S.K. GuptaNuclear Recycle GroupBhabha Atomic Research CentreTarapur, Mumbai, Maharashtra, India

May-Britt HggDepartment of Chemical EngineeringNorwegian University of Science and TechnologyTrondheim, Norway

B. HanDepartment of Chemical and Biological EngineeringColorado State UniversityFort Collins, Colorado

A.M. HidalgoDepartamento de Ingeniera QumicaUniversidad de MurciaCampus de EspinardoMurcia, Spain

John HubbleDepartment of Chemical EngineeringUniversity of BathBath, United Kingdom

J. Angel IrabienDepartamento de Ingeniera Qumica y Qumica InorgnicaUniversidad de CantabriaSantander, Spain

P. JanardanNuclear Recycle GroupBhabha Atomic Research CentreTarapur, Mumbai, Maharashtra, India

Jan ke JnssonAnalytical ChemistryLund UniversityLund, Sweden

Gary W. JungMembrane Technology ConsultantDaytona Beach, Florida

Vladimir S. KislikCasali Institute of Applied ChemistryThe Hebrew University of JerusalemJerusalem, Israel

Punit KohliDepartment of Chemistry and BiochemistrySouthern Illinois UniversityCarbondale, Illinois

Ralf KuriyelBiopharm Applications R&DPall Life SciencesPall CorporationNorthborough, Massachusetts

V.M. LinkovSouth African Institute for Advanced Materials ChemistryUniversity of the Western CapeBellville, South Africa

J. LoraChemical and Nuclear Engineering DepartmentPolytechnic University of ValenciaValencia, Spain

R. MalladaDepartment of Chemical and EnvironmentalEngineering


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A.M. MalulekeSouth African Institute for Advanced Materials ChemistryUniversity of the Western CapeBellville, South Africa

V.K. ManchandaRadiochemistry DivisionBhabha Atomic Research CentreTarapur, Mumbai, Maharashtra, India

Mika MnttriLaboratory of Membrane Technology and TechnicalPolymer Chemistry

Lappeenranta University of TechnologyLappeenranta, Finland

Philipina A. MarceloDepartment of Chemical EngineeringThe Research Center for the Natural SciencesUniversity of Santo TomasManila, Philippines

Charles R. MartinDepartment of ChemistryCenter for Research at the Bio=Nano InterfaceUniversity of FloridaGainesville, Florida

K.P. MishraRadiation Biology and Health Sciences DivisionBhabha Atomic Research CenterTarapur, Mumbai, Maharashtra, India

B.M. MisraNuclear Desalination UnitDivision of Nuclear PowerNuclear Power TechnologyDevelopment Section

Department of Nuclear EnergyVienna, Austria

P.K. MohapatraRadiochemistry DivisionBhabha Atomic Research CentreTarapur, Mumbai, Maharashtra, India

Carmen I. MoraruDepartment of Food ScienceCornell UniversityIthaca, New York

Sanjay NeneBiochemical Engineering GroupChemical Engineering and Process Development DivisionNational Chemical LaboratoryPune, Maharashtra, India

Marianne NystrmLaboratory of Membrane Technology and TechnicalPolymer Chemistry

Lappeenranta University of TechnologyLappeenranta, Finland

Inmaculada OrtizDepartamento de Ingeniera Qumica y QumicaInorgnica

Universidad de CantabriaSantander, Spain

Anil Kumar PabbyNuclear Recycle GroupBhabha Atomic Research CentreTarapur, Maharashtra, India

Sangita PalDepartment of Chemical EngineeringInstitute of Chemical TechnologyMumbai UniversityMumbai, Maharashtra, India

Vishwas G. PangarkarDepartment of Chemical EngineeringInstitute of Chemical TechnologyMumbai UniversityMumbai, Maharashtra, India

D. Paolucci-JeanjeanEuropean Membrane InstituteUniversit MontpellierMontpellier, France

Ganapathi PatilDepartment of Food EngineeringCentral Food Technological Research InstituteMysore, Karnataka, India

Jilska M. PereraDepartment of Chemical and BiomolecularEngineering

University of MelbourneParkville, Victoria, Australia

M.P. PinaDepartment of Chemical and EnvironmentalEngineering


R.A. PittmanMembrana-CharlotteCelgardCharlotte, North Carolina

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Gerald PourcellyEuropean Membrane InstituteUniversit Montpellier 2Montpellier, France

Prakhar PrakashChevron Energy Technology CompanyRichmond, California

K.S.M.S. RaghavaraoDepartment of Food EngineeringCentral Food Technological Research InstituteMysore, Karnataka, India

V. RamachandhranDesalination DivisionBhabha Atomic Research CentreTarapur, Mumbai, Maharashtra, India

Vineet RaoDepartment of PhysicsTechnische Universitt MnchenGarching, Germany

N.S. RathoreNuclear Recycle GroupBhabha Atomic Research CentreMumbai, Maharashtra, India

G.M. RiosEuropean Membrane InstituteUniversit MontpellierMontpellier, France

Syed S.H. RizviFood Process EngineeringInstitute of Food ScienceCornell UniversityIthaca, New York

R. Roque-MalherbeSchool of Science and TechnologyUniversity of TuraboGurabo, Puerto RicoandInstitute of Chemicaland Biological Technology

University of TuraboGurabo, Puerto Rico

S.C. RoyNuclear Recycle GroupBhabha Atomic Research CentreTarapur, Maharashtra, India

S.S. SablaniDepartment of Biological Systems EngineeringWashington State UniversityPullman, Washington

M. SanchoChemical and Nuclear Engineering DepartmentPolytechnic University of ValenciaValencia, Spain

S. SarradeWaste Management DivisionFrench Atomic Energy CommissionBagnols sur Ceze, France

Ana Maria SastreChemical Engineering DepartmentUniversitat Politcnica de CatalunyaBarcelona, Spain

S.R. SawantNuclear Recycle GroupBhabha Atomic Research CentreTarapur, Maharashtra, India

Ernst Ulrich SchraderBeverage Engineering Inc.Concord, Ontario, Canada

S.I. SemenovaVladimir State UniversityVladimir, Russia

A. SenguptaMembrana-CharlotteCelgardCharlotte, North Carolina

Arup K. SenGuptaDepartment of Civil and EnvironmentalEngineering

Fritz Engineering LaboratoryLehigh UniversityBethlehem, Pennsylvania

B. SmithaMembrane Separation GroupChemical Engineering DivisionIndian Institute of Chemical TechnologyHyderabad, Andhra Pradesh, India

J.V. SonawaneNuclear Recycle GroupBhabha Atomic Research CentreTarapur, Maharashtra, India

Pabby et al./Handbook of Membrane Separations 9549_C000 Final Proof page xviii 21.5.2008 7:54pm Compositor Name: BMani

xviii

S. SridharMembrane Separation GroupChemical Engineering DivisionIndian Institute of Chemical TechnologyHyderabad, Andhra Pradesh, India

Geoff W. StevensDepartment of Chemical and Biomolecular EngineeringUniversity of MelbourneMelbourne, Victoria, Australia

Ulrich StimmingDepartment of PhysicsTechnische Universitt MnchenGarching, GermanyandZAE Bayern, Division 1Garching, Germany

G. VerdChemical and Nuclear Engineering DepartmentPolytechnic University of ValenciaValencia, Spain

M. WesslingMembrane Technology GroupUniversity of TwenteEnschede, the Netherlands

S.R. WickramasingheDepartment of Chemical and Biological EngineeringColorado State UniversityFort Collins, Colorado

Grazyna Zakrzewska-TrznadelDepartment of Nuclear Methods in Process EngineeringInstitute of Nuclear Chemistry and TechnologyWarszawa, Dorodna, Poland

Rongsheng ZhangDepartment of Chemical EngineeringUniversity of BathBath, United Kingdom

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Pabby et al./Handbook of Membrane Separations 9549_C000 Final Proof page xx 21.5.2008 7:54pm Compositor Name: BMani

Section I

Membrane Applications in Chemicaland Pharmaceutical Industriesand in Conservation of Natural Resources

Pabby et al./Handbook of Membrane Separations 9549_C001 Final Proof page 1 13.5.2008 12:54pm Compositor Name: BMani

1 Membrane Applications in Chemicaland Pharmaceutical Industriesand in Conservation of NaturalResources: Introduction

Ana Maria Sastre, Anil Kumar Pabby, and Syed S.H. Rizvi

CONTENTS

References .................................................................................................................................................................................... 5

In the last 40 years, membranes have developed from a research topic to a mature industrial separation technology. Thisincrease in the use of membrane technology is driven by spectacular advances in membrane development, the wider acceptanceof the technology in preference to conventional separation processes, increased environmental awareness and, most import-antly, strict environmental regulations and legislation. Various membrane processes are currently applied in the chemical(including petrochemicals), pharmaceutical, and food and beverage industries. Particularly, strong development and growth ofmembrane technology can be observed in the purication of wastewater and the production of drinking water.

This statement summarizes the discussions at a conference on the Exploration of the potential of membrane technology forsustainable decentralized sanitation held in Italy (at Villa Serbelloni, Bellagio) on 2326 April 2003 [1].*

Due to plummeting costs and dramatically improving performance, water-treatment applications based on membranes are blossoming.In particular, membrane bioreactors (MBRs) are today robust, simple to operate, and ever more affordable. They take up little space,need modest technical support, and can remove many contaminants in one step. These advantages make it practical, for the rst time, toprotect public health and safely reuse water for non-potable uses. Membranes can also be a component of a multi-barrier approach tosupplement potable water resources. Finally, decentralization, which overcomes some of the sustainability limits of centralizedsystems, becomes more feasible with membrane treatment. Because membrane processes make sanitation, reuse, and decentralizationpossible, water sustainability can become an achievable goal for the developed and developing worlds.

A membrane can essentially be dened as a barrier that separates two phases and selectively restricts the transport ofvarious chemicals. It can be homogenous or heterogeneous, symmetric or asymmetric in structure, solid or liquid, and can carrya positive or negative charge, or be neutral or bipolar. Transport across a membrane can take place by convection or bydiffusion of individual molecules, or it can be induced by an electric eld or concentration, pressure or temperature gradient.The membrane thickness can vary from as little as 100 mm to several millimeters.

A membrane separation system separates an inuent stream into two efuent streams known as the permeate and theconcentrate. The permeate is the portion of the uid that has passed through the semipermeable membrane, whereasthe concentrate stream contains the constituents that have been rejected by the membrane.

The correct choice of membrane should be determined by the specic objective, such as the removal of particulates ordissolved solids, the reduction of hardness for the production of ultra pure water or the removal of specic gases=chemicals.The end use may also dictate the selection of membranes in industries such as potable water, efuent treatment, desalination, orwater supply for electronic or pharmaceutical manufacturing.

Membrane technology covers various chemical technology disciplines, such as material science and technology, masstransport and process design. By manipulating material properties, membranes can be tailor-made for particular separation tasks

* From Fane, A.G., Editorial, J. Membr. Sci., 233, 127, 2004. With permission.

3


to be performed under specic separation conditions. Membranes are manufactured as at sheets, capillaries, or in tubularshapes and are applied in various module congurations. The following membrane modules are commonly used for industrialapplications: (a) the plate and frame module; (b) the spiral wound module; (c) the tubular membrane module; (d) the capillarymembrane module; and (e) the hollow ber membrane module.

Membrane separation processes have numerous industrial applications and provide the following advantages: They offerappreciable energy savings; they are environmentally benign; the technology is clean and easy to operate; they replaceconventional processes like ltration, distillation, and ion exchange; they produce high-quality products; and they offer greaterexibility in system design. Pressure-driven processes such as ultraltration, nanoltration, and microltration are alreadyestablished and various applications have been commercialized in the elds of pharmaceutical and biotechnology. Recently,the development of a means of characterizing, controlling, and preventing membrane fouling has been proved vital. Thedevelopment of tailored membranes, fouling prevention, and optimization of chemical cleaning will ensure a high level ofmembrane process performance. In the last ve years, the development of new techniques for membrane characterization andthe improvement of existing techniques have increased our knowledge of the mechanisms involved in membrane fouling. Moreadvanced techniques, such as environmental scanning electron microscopy (ESEM), have been used to study membranefouling during the microltration of high metal content solutions with aluminum oxide membranes [2]. This will provide notonly useful insight into the fouling mechanism but also a better understanding of the factors that affect membrane fouling.

The combination of molecular separation with a chemical reaction, or membrane reactors, offers important new oppor-tunities for improving the production efciency in biotechnology and in the chemical industry. With regard to the future ofbiotechnology and pharmaceutical processes, the availability of new high-temperature-resistant membrane contactors offers animportant tool for the design of alternate production systems appropriate for sustainable growth.

Membrane technology has widespread applications in chemical and pharmaceutical industries and its use in various otherelds is increasing rapidly. It has established applications in areas such as hydrogen separation, the recovery of organic vaporsfrom process gas streams, and the selective transport of organic solvents, and it is creating new possibilities for catalyticconversion in membrane reactors. It provides a unique solution for industrial waste treatment and for the controlled productionof valuable chemicals. Since it deals with the smallest penetrants in the size spectrum, gas separation requires extremely precisediscrimination of size and shapeoften in the range of 0.20.3 between permeated and rejected species. Such demandstruly push the state of the art in materials science for these specic applications. In addition to polymeric media, ceramic,carbon, zeolite, and metal membranes are attractive options as they provide both precise separation and robustness. Vision andcommitment are required to make the most of the large energy savings (and CO2 emission reductions) offered by membraneswhen compared with traditional, thermally driven separations and energy conversion. The use of membranes for extraction inanalytical chemistry has increased recently. The main aim is to selectively extract and enrich the compounds to be determined(analytes) from samples of varying chemical complexity. In contrast to many technical uses of membranes, in analyticalapplications it is essential to recover the extracted analytes as efciently as possible so that they can be transferred to suitableanalytical instruments for the nal quantitative determination.

Similarly, membrane contactors have proved to be efcient contacting devices, due to their high area per unit volume thatresults in high mass transfer rates. They are not only compact but also eliminate several of the problems faced in conventionalprocesses such as ion exchange, solvent extraction, and precipitation. Membrane contactor processes, in which phasecontacting is performed or facilitated by the structure and shape of the porous membrane, provide new dimension to thegrowth of membrane science and technology and also satisfy the requirements for process intensication. In addition,membrane contactors represent a signicant step forward from the initial success of blood oxygenators. Their integrationwith other membrane systems, including membrane reactors, could lead to the redesign of membrane-based integratedproduction lines.

This introductory section outlines several established applications of membranes in the chemical and pharmaceuticalindustries, reviews the membranes and membrane processes available in this eld, and discusses the huge potential of thesetechnologies. In addition, other important topic dealing with conservation of natural resources (zeolite membranes) is alsopresented in this section. Each chapter has been written by a leading international expert with extensive industrial experience inthe eld.

Chapter 1 (the current chapter) presents an overview of different membrane processes and a description of all of thechapters presented in Section I. Chapter 2 explains the potential of hollow ber contactors in the eld of chemical technologyand how they have changed industrial preferences regarding contacting devices. This chapter gives an introduction tomembrane contact technology, its principles of operation, and the benets obtained from the use of membrane contactors.Important applications, new product development requirements, and future directions are also discussed. Chapter 3 deals withmembrane chromatography. This chapter discusses the latest developments in membrane-based stationary phases (afnitymembranes and mixed matrix membrane adsorbers) and monolithic separation media (organic and inorganic). It also providesinformation on new types of chromatographic support, focusing on membrane materials, properties, and preparation. Finally, itconsiders possible applications of chromatographic membranes in various process conditions. Chapter 4 focuses on theimportant aspects of membrane application in gas separation. It deals with the subject comprehensively, providing an

4 Handbook of Membrane Separations


introduction and discussing transport mechanisms, different membrane materials for gas separation, module design, current andpotential applications, and novel developments in this eld. Chapter 5 presents developments in pervaporation (PV). It rstgives a brief introduction to the theory of pervaporation and then discusses sorption thermodynamics in polymers, the solutiondiffusion model, the criteria for membrane polymer selection, and important applications of PV in different cases of aqueousand organic separation. Chapter 6 focuses on advances in the eld of ceramic membranes, covering interesting applications inthis area. Chapter 7 describes important developments in the elds of supercritical uids and membrane technology. Chapter 8presents the various methodologies or techniques for improving the membrane performance of microltration, ultraltration,nanoltration, and reverse osmosis. The aim is to present the techniques that attempt to minimize concentration polarization(and fouling) and allow the membrane to perform closer to its intrinsic capability. The methods range from the critical uxapproach to the suite of hydrodynamic techniques and other potential strategies. Chapter 9 records important developments inthe eld of polymeric membranes for the separation and removal of hydrocarbons. It provides an introduction to the subject,discusses the background and physicochemical regularities of hydrocarbon permeation in membrane-based glassy and rubberypolymers, and lists some important applications. Chapter 10 describes some of the main characteristics of the use of zeolitemembranes in separation applications. Zeolite membranes separate molecules based on the differences in their adsorption anddiffusion properties. They are therefore suitable for separating gas and liquid phase mixtures by gas separation and pervapora-tion, respectively. This chapter reviews the basic mechanisms of gas separation and pervaporation through zeolite membranesand presents examples of industrial applications. Chapter 11 focuses on membrane fouling and the strategies used to reduce itrelative to pressure-driven processes. This chapter highlights recent strategies for minimizing membrane fouling. In particular,it discusses the literature on fouling phenomena in reverse osmosis and ultraltration membrane systems, the analyticaltechniques employed to quantify fouling, preventive methods, and membrane cleaning strategies. Specic recommendationsare also made on how scientists, engineers, and technical staff can help to improve the performance of these systems byminimizing membrane fouling phenomena. Chapter 12 describes membrane extraction and its use in preconcentration,sampling, and trace analysis. Chapter 13 presents applications of aqueous hybrid liquid membranes (AHLM) and organichybrid liquid membranes (OHLM) in the separation of organic and metal species, respectively.

Chapter 14 provides an introduction to membrane applications in the pharmaceutical industry, its current status, and futurepotential in this very important area. Chapter 15 is devoted to membrane applications in the drug delivery eld with emphasison the mechanisms governing mass transport to modulate the release kinetics. Hydrogel membranes, as a derivative construct ofhydrogels, have become increasingly attractive for precisely controlling the drug delivery rate via chemical sensing andtriggering. Their current status, challenges, and opportunities are highlighted in Chapter 16.

REFERENCES

1. Fane, A.G., Editorial, J. Membr. Sci., 233, 127128, 2004.2. Skerlos, S.J., Rajagopalan, N., DeVor, R.E., Kapoor, S.G., and Angspatt, V.D., Microltration polyoxyalkylene metalworking uid

lubricant additives using aluminum oxide membranes, J. Man. Sci. Eng. Trans., 123, 692699, 2001.

Membrane Applications in Chemical and Pharmaceutical Industries 5


2 Application of Membrane Contactorsas Mass Transfer Devices

A. Sengupta and R.A. Pittman

CONTENTS

2.1 Introduction ...................................................................................................................................................................... 72.2 Scope of This Chapter...................................................................................................................................................... 72.3 Description of Membrane Contactor................................................................................................................................ 82.4 Principle of Operation ...................................................................................................................................................... 82.5 Benets of Membrane Contactor Technology............................................................................................................... 102.6 Mass Transfer Process in Membrane Contactor ............................................................................................................ 102.7 Literature Review on Membrane Contactor Applications ............................................................................................. 122.8 Use of GasLiquid or LiquidGasLiquid Contact....................................................................................................... 122.9 Use of LiquidLiquid Contact ....................................................................................................................................... 132.10 Review of Membrane Contactor Design Options.......................................................................................................... 142.11 Commercial or Precommercial Installations of Large-Scale Membrane Contactors..................................................... 15References .................................................................................................................................................................................. 20

2.1 INTRODUCTION

Membrane contactors as a type of membrane device have been known for quite a few years now [12]. They involve a uniqueclass of membrane-based mass transfer and separation technologies, which have grown beyond academic curiosity and foundcommercial applications across various industries and markets. It has been found to be a cost-effective technology and istherefore used to supplant or replace other technologies that might or might not be based on membranes. In some situations,membrane contacting has emerged as an enabling technology that is lling some previously unmet commercial needs.

By the standard of business size, membrane contactor technology is currently a minor player compared to other muchbetter-known membrane separation technologies such as reverse osmosis (RO), membrane ltration, membrane gas separation,diffusion dialysis, and electrodialysis. By its very nature, the membrane contactor does not function or compete with the othermembrane devices, and the capability and functionality of contactors are signicantly different from the other devices.But membrane contactor technology seems to have the potential to be applicable over a much wider array of industries. Useof membrane contactor devices in various forms is growing continuously. In many applications the contactor is not even calleda contactor but is referred to by other names depending on the specic application it is deployed in. Examples include bloodoxygenator (the earliest use of membrane contactor), gas transfer membrane, membrane degasier, membrane deaerator,membrane distillation device, osmotic distillation device, membrane gas absorber, membrane extractor, and membranehumidier.

2.2 SCOPE OF THIS CHAPTER

Considering the wide applications of membrane contactors and the evolving nature of this technology, it is difcult to coverevery aspect in a monograph. The intent of this article is to rst explain the technology and the principles of operation, withsome remarks on the mass transfer process in membrane contactors. This is followed by description of various types ofcontacting possibilities and review of a wide sampling of literature on the technology to date. Design options of membrane

The authors references to the various patents mentioned in this article do not constitute a grant of a license to practice any of these technologies, nor do theyimply the authors acknowledgment of the validity of any of the referenced patents.

7


contactors are then reviewed. Finally, some current and emerging commercial applications at different stages of developmentare discussed in detail.

2.3 DESCRIPTION OF MEMBRANE CONTACTOR

From outward appearance membrane contactors look similar to other membrane devices. However, functionally the membranesused in contactors are very different. They are mostly nonselective and microporous. Membrane contactors can be madeout of at sheet membranes and there are some commercial applications. Most common commercial membrane contactorsare, however, made from small-diameter microporous hollow ber (or capillary) membranes with ne pores (illustrated inFigure 2.1) that span the hollow ber wall from the ber inside surface to the ber outside surface. The contactor shown asan example in Figure 2.1 resembles a tube-in-shell conguration with inlet=outlet ports for the shell side and tube side. Themembrane is typically made up of hydrophobic materials such as Polypropylene, Polyethylene, PTFE, PFA, and PVDF.

The membrane in a contactor acts as a passive barrier and as a means of bringing two immiscible uid phases (such as gasand liquid, or an aqueous liquid and an organic liquid, etc.) in contact with each other without dispersion. The phase interface isimmobilized at the membrane pore surface, with the pore volume occupied by one of the two uid phases that are in contact.Since it enables the phases to come in direct contact, the membrane contactor functions as a continuous-contact mass transferdevice, such as a packed tower. However, there is no need to physically disperse one phase into the other, or to separate thephases after separation is completed. Several conventional chemical engineering separation processes that are based on massexchange between phases (e.g., gas absorption, gas stripping, liquidliquid extraction, etc.) can therefore be carried out inmembrane contactors.

2.4 PRINCIPLE OF OPERATION

Principle of membrane contactor operation is based on the natural phenomenon of capillary force. When one side of ahydrophobic microporous membrane is brought in contact with water or an aqueous liquid, the membrane is not wettedby the liquid, i.e., the liquid is prevented from entering the pores, due to surface tension effect. The interface between a liquidand a solid substrate can be characterized by the parameter contact angle (Figure 2.2). The wettability of a solid surface by aliquid surface decreases as the contact angle increases. A contact angle of less than 908 implies that the liquid will tend to wetthe substrate (hydrophilic), whereas if contact angle is greater than 908 the liquid will not tend to wet the surface (hydrophobic).Table 2.1 lists the contact angle values for few different materials in water at ambient temperature.

If a dry microporous hydrophobic hollow ber membrane with air-lled pores was surrounded by water there would not beany penetration by water into the pores until the water pressure exceeds a certain critical breakthrough pressure. The magnitude

Lumen fluidoutlet

Lumen fluidinlet

Microporoushollow fibers

Shellfluid

outlet

Shell fluidinlet

Potting

Pores

FIGURE 2.1 Microporous hollow ber membrane in a membrane contactor.



of this critical breakthrough pressure differential (water pressure minus air pressure) DPC has been mathematically derived,and is expressed [3] by the following equation that is often referred to as the YoungLaplace equation:

DPC 4l cos ud (2:1)

wherel is the surface tension of wateru is the contact angle for the system airwatermembrane in degreesd is the effective diameter of the membrane pore, assuming pores are circular in shape

For a hydrophobic porous material with contact angle greater than 908, the DPC is >0 and depends on the liquid surfacetension and the membrane pore size. As an example, considering waterairpolypropylene system, one can calculate that for adry membrane with a pore size of 0.03 mm (30 nm) the critical entry pressure of water is more than 300 psi (>20 bar).

Since the liquid phase does not enter the pores, a stable gasliquid phase interface can be created and maintained(as illustrated in Figure 2.3) as long as the liquid phase pressure is higher than the gas phase pressure and the phase pressuredifferential DP is between 0 and DPC. The pores remain air lled at this condition. The liquid and the gas phases couldbe owing at different ow rates on either side of the membrane wall, but the phase interface remains stable all along themembrane. Thus, by proper control of pressures, the two immiscible phases come in constant contact without a need to disperseone into the other. This allows mass transfer or mass exchange between phases [45], such as gas absorption or gas stripping(desorption).

The same principle of operation as described above is applicable also to liquidliquid extraction where an aqueousliquid and an organic liquid contact each other inside the contactor for extraction of a solute selectively from one phase toanother [68]. The critical breakthrough pressure for liquidliquid system could be calculated by Equation 2.1, except that theterm l would now be the interfacial tension between the two liquids. Further variation of membrane contacting technology iscalled gas membrane or gasgap membrane where two different liquid phases ow on either side of the membrane, but themembrane pores remain gas lled [910]. In this situation two separate gasliquid contact interfaces are supported on each sideof a single membrane.

Liquiddroplet

Contactangle (q )Vapor

Solid surface

FIGURE 2.2 Representation of contact angle.

TABLE 2.1Contact Angle for Various Materials in Waterat Ambient Temperature

Substrate Contact Angle (In degrees)

Ordinary glass 20Platinum 40Anodized aluminum 60PMMA 74

Nylon 79Polyethylene 96Polypropylene 108

Teon 112


Application of Membrane Contactors as Mass Transfer Devices 9

2.5 BENEFITS OF MEMBRANE CONTACTOR TECHNOLOGY

Primary list of features and resulting benets for the technology are shown in Table 2.2.

2.6 MASS TRANSFER PROCESS IN MEMBRANE CONTACTOR

In gasliquid, liquidliquid, or liquidgasliquid contactors there is no convective ow of any phase across the membrane.Mass transfer occurs only by diffusion across the immobilized phase in the pores. The direction of mass transfer of anymolecular species depends on the concentration driving force maintained across the membrane for that species. The presence ofthe stationary phase in the membrane pore creates an extra diffusional mass transfer resistance. However, it can be shown that inmany cases the membrane resistance is negligible, and that in most cases the high active mass transfer area created inside amembrane contactor more than compensates for any additional mass transfer resistance [45].

Mass transfer resistance in a continuous-contact separation device is the inverse of the mass transfer coefcient. Inmembrane contactors, the total resistance could be expressed as three resistances in series. These include the individualresistances in each owing phase and the membrane resistance (Figure 2.4). For a liquidgas contact system Equation 2.2 couldbe written for each diffusing species:

1dOUTKTOTAL

1dOUTkSHELL

1HdAVGkM

1HdINkTUBE

(2:2)

whereK is the overall coefcientsk is the individual mass transfer coefcients

Gas flow

Pores on hollowfiber wall

A single hollowfiber wall

Gas phase flowing insidehollow fiber,

gas pressure PGAS

Two required conditions for stable phase interface,1. PLIQUID > PGAS, and2. 0 < (PLIQUIDPGAS) < PC

Liquid water phase flowingaround hollow fibers;

Liquid pressure PLIQUID

Liquid-gas phaseinterface at

stable condition

FIGURE 2.3 Liquidgas interface in a membrane contactor.

TABLE 2.2Benets of Membrane Contactor Technology

Features Benets

High concentration of active phase contact area Prole or footprint of membrane contactor systems are small; t into existing building; no additional

structure neededFlow rates of phases in contact can be controlledindependently

No physical limitations such as ooding or loading; contact area constant irrespective of phaseow rates; process more exible

Modular in nature Easier to add system capacity incrementally; can often be retrotted into existing systems;easier scale-up

Mass transfer does not depend on gravity Contactor can be mounted vertically or horizontally; will also work in microgravity; able to processtwo uid phases of same densities

No need to disperse or coalesce phases Eliminates extra steps; more efcient utilization of device volumeCan be operated with high uid outlet pressures Eliminates or reduces need for transfer pumps or booster pumps after contactor



Each term on right side of Equation 2.2 represents an individual resistance as depicted in Figure 2.4. Hollow ber diametersare dOUT and dIN. The term H is the Henry coefcient (liquidgas equilibrium constant) for the species in question. In the caseof liquidliquid contact, the term H in Equation 2.2 should be replaced by mD, the equilibrium distribution coefcient betweentube side liquid and shell side liquid.

The membrane transfer coefcient kM is a function of (1) the diffusion coefcient in the phase occupying membrane poresand (2) various membrane geometric parameters. Assuming pure Fickian diffusion in a symmetric microporous membrane, kMcan be shown as [5]

kM 2DMtM dOUT dIN (2:3)

whereD is diffusivity in the pore phaseM and tM are membrane porosity and tortuosity factors, functions of the membrane morphology

In case of complex membrane morphology such as asymmetric or composite membranes, or when Fickian diffusion is notvalid, evaluating kM will be more complex. Individual mass transfer coefcients in Equation 2.2 depend on multiple factorssuch as temperature, pressure, ow rates, and diffusion coefcients and could often be estimated from empirical correlationsavailable in literature [1,2,6].

The rate of mass transfer, R, for each species from shell side to tube side at any point inside the contactor is given as

R KTOTAL A CSHELL CTUBE (2:4)

whereA is the membrane transfer area based on outside diameter of the hollow berCSHELL and CTUBE are bulk concentrations of the species in shell side and tube side, respectively

Strictly speaking Equations 2.2 and 2.4 are valid only locally within the contactor. The concentrations in each phase couldchange continuously inside the contactor. It is also possible for one of the mass transfer coefcients to change within thecontactor. In such cases rate of mass transfer will be varying continually within the contactor, and the average overall masstransfer will be obtained by integrating over the entire contactor.

Total mass transfer resistance

Membraneresistance

Outer phase (shellside) resistance

CSHELL

For compositemembrane,

multipleresistances

possible

CTUBE

DIN/2

DOUT/2

Inner phase (tubeside) resistance

Hollow fiber wall(membrane)

FIGURE 2.4 Mass transfer resistances in membrane contactor.



Useful simplications are often made in Equation 2.2. We will use gasliquid contact as an example, and assume gas-lledhomogeneous membrane of high porosity, thin wall, and low tortuosity. Since diffusion in gas phase is generally of threeorders of magnitude faster than in liquid phase, one can show that kM and kG are quite high in this case compared to kL, and sothe controlling resistance to mass transfer is in the liquid phase. This means KTOTAL is essentially the same as kL. If kL isconstant within the contactor the total mass transfer rate in Equation 2.4 can be approximated for the entire contactor as

R kL ATOTAL DCLOG---MEAN (2:5)

DCLOGMEAN is the log mean of the concentration differential (CSHELLCTUBE) from one end of the contactor to the other.

2.7 LITERATURE REVIEW ON MEMBRANE CONTACTOR APPLICATIONS

Over the years many research and development groups, both academic and industrial, have investigated membrane contactortechnology and suggested or developed a wide range of possible applications. There is quite a spectrum of patent and publishedliterature on this subject. Markets and industries that benet from the development of this technology include medical,biotechnology, pharmaceutical, semiconductor and electronics, food and beverage, environmental, and other special processindustries that are nding new uses. It is impossible to mention all the work done to date.

2.8 USE OF GASLIQUID OR LIQUIDGASLIQUID CONTACT

As mentioned earlier, membrane blood oxygenators probably would qualify as the earliest form of membrane contactors.Reference [11] is a good illustration of a hollow ber device. However, most work on liquidgas membrane contactor over theyears has focused mainly on two categories: (1) separation, purication, and treatment of water or aqueous media and (2)absorption of gaseous species from air either for purication or for recovery, which will be discussed separately. Applicationsin multiple markets and industries have been investigated in each category.

An early example of a patent on membrane contactor for gas transfer is in Ref. [12]. Harvesting of oxygen dissolved inwater and discharging of CO2 to the water is presented in Ref. [13]. A membrane device to separate gas bubbles from infusionuids such as human-body uids is claimed in Ref. [14]. A hollow ber membrane device for removal of gas bubbles thatdissolve gasses from uids delivered into a patient during medical procedures is disclosed in Ref. [15]. Membrane contactorshave also found application in dissolved gas control in bioreactors discussed in Refs. [1617].

Application of membrane contactors for water degasication has been thoroughly investigated and reported in Refs. [1821].During the last few years this has been one of the most successful applications of membrane contactors on large commercialscale. Specically, oxygen removal and gas transfer from ultrapure water for semiconductor industry have been discussed inRefs. [2227]. Deaeration process for beverage water is discussed in Ref. [28]. Oxygen removal from boiler feed water assubstitute for steam deaerator or oxygen scavenger is presented in Ref. [29]. Membrane contactors have also been used tocarbonate water [30], to nitrogenate beer [31], to simultaneously nitrogenate and decarbonate beer, to control CO2 level in beer,and to control dissolved gas prole in beverages using mixed sweep gases of CO2 and N2 [3233].

Removal of dissolved volatile organic compounds (VOC) from water in membrane contactors has been the subject ofseveral investigations. VOC can be separated from water by applying a vacuum, the process is often termed vacuum membranedistillation [3436]. Alternately, air can be used as a sweep gas to strip VOCs from water across the membrane [37]. Airstripping of water in packed or spray columns is a widely accepted process for ground water or process water treatment. Ifmembrane contactors were used broadly for this purpose, the market potentials are certainly high. A variation of membrane airstripping process is discussed in Ref. [38] where the driving force for VOC stripping of water is established using methano-tropic bacteria. Total organic carbon (TOC) reduction from ultrapure water during membrane degassing has been reported inRef. [39]. Removal of tri-halo methane (THM) compounds, a chemical class of undesirable species, from ultrapure water hasbeen discussed in Ref. [40]. Use of microporous membranes in combination with RO to separate dissolved gases from water isdisclosed in Ref. [41]. Study on removal and recovery of volatile aroma compounds from water was presented in Ref. [42].

Adding oxygen or other benecial gas species to water without forming gas bubbles is another application of membranecontactors. This subject has been discussed in Refs. [4346]. Membranes in module form and hollow bers in unconned formhave been investigated. Use of membrane contactors for supplying oxygen to a biolm is claimed in Ref. [47]. A similarprocess where gaseous hydrogen is added to aqueous liquid without bubble formation is disclosed in Ref. [48]. The purpose forsuch a process would be to use dissolved hydrogen to biologically or catalytically remove oxygen, nitrite, or nitrate from water.Membrane contactors are also used to add trace quantity of CO2 into ultrapure water to control water resistivity and preventformation of static electricity [49]. A more recent and signicant application of membrane contactors is the addition of gaseousozone to water for the purpose of disinfection and removal of organic contamination, such a process is disclosed in Ref. [50].

A number of applications of the previously termed gas membrane have also been studied over the years to remove orrecover volatile species from water or other aqueous media. The primary drivers for these investigations are the intriguing and



creative possibilities of the gas membrane, which in effect combines two gasliquid contact processes (stripping andabsorption) within a single microporous membrane. Some of the early-published studies include recovery of bromine [51],cyanide [52], ammonia [5355], and ethanol [56]. Applications of this technology for commercial purposes are in variousstages of development [57].

Membrane processes termed as osmotic distillation or membrane distillation could be shown to be applications ofmembrane contactor technology also. Both of these processes are based on gas membranes. Osmotic distillation, sometimescalled osmotic evaporation, involves transfer of water vapor across a gas-lled membrane, the process is driven by a differencein water vapor pressure maintained across the membrane [5859] by separate aqueous liquids. Membrane distillation is aprocess where water vapor transfer is driven solely by a temperature difference across the gas-lled membrane [6061]. Waterevaporates from a hot aqueous phase and condenses on a cooler surface. This process may be useful in desalinating water orproducing pure water if a good natural source of warm water is available, such as in a geothermal process.

As mentioned in Table 2.2, one unique feature of membrane contactors is the ability to operate without the aid of gravity.This, along with the advantage of smaller sizes for contactor systems, has led to the interest in possible use of this technologyin microgravity and conned spaces such as spacesuits, manned spacecrafts, and space station. Primary applications are(1) separating gas and liquid phases in microgravity and (2) removal of unwanted gas species from liquids [6264].

We now discuss the second category of applications that focus on treatment and conditioning of air or gas streams. Thisis done either (1) by capturing (absorbing) gaseous species from air or other gases into water or aqueous liquids or (2)by controlling the properties of air or gas phase by other means of heat and mass transfer across membrane in a contactor.The rst detailed investigation of absorption of a gas species (CO2) in a liquid using a membrane contactor was discussedin detail in Refs. [4,5]. The mass transfer analysis in these early papers has been most inuential for understanding thetechnology.

Absorption of various gases such as CO2, SO2, NH3, and carbon monoxide in water using membrane contactors wasstudied by many other research groups and reported in Refs. [6570]. Removal of CO2 as a greenhouse gas from air and bulkremoval of CO2 from air in contactors using conventional absorbents have been reported in Refs. [7173]. The topic ofscrubbing CO2 from air for self-contained breathing systems using microporous membrane is discussed in Ref. [74]. CapturingCO2 from atmosphere using membrane contactors, as part of a hydrogen storage process, was suggested in Ref. [75]. Use ofmembrane contactors for recovery of VOCs from air was reported in Ref. [76]. A hollow ber membrane bioreactor, for thepurpose of destroying toxic compounds from air, is shown in Ref. [77].

Controlling temperature and humidity of process air or ambient air is another unique application of membrane contactors.Membranes are used to humidify or dehumidify air by bringing air in contact with water or a hygroscopic liquid. Mass transferin such processes is very fast since mass transfer resistance in the liquid phase is negligible. Heat transfer and mass transfer aredirectly related to these processes, since latent heat of evaporation (or condensation) creates temperature proles inside thecontactor. Some of the references in Literature are shown in Refs. [7879]. Application of such processes has been proposed forconditioning air in aircraft cabins [80], in buildings or vehicles [81], or in containers to store perishable goods [82].

2.9 USE OF LIQUIDLIQUID CONTACT

A historical perspective on aqueousorganic extraction using membrane contactor technology is available in Refs. [1,6,83].The mechanism of phase interface immobilization was rst explored in Ref. [84], while application of membrane solventextraction for a commercial process was rst explored in Ref. [85]. Two aspects of liquidliquid contact in membranecontactors that are different from typical gasliquid contact are (1) the membrane used could be hydrophobic, hydrophilic,or a composite of both and (2) the membrane mass transfer resistance is not always negligible. Ensuring that the right uidoccupies the membrane pores vis--vis the afnity of the solute in the two phases can minimize membrane resistance. Theseaspects have been discussed in detail in Refs. [6,86,87].

Membrane contactor applications in the liquidliquid extraction eld fall in two categories: (1) removal of unwantedspecies from water and (2) removal and recovery of valuable species from water. Many investigations have been conductedover the year by academia as well as by industry. Below we are providing some samples from the wide range of applicationsreported in literature. The examples presented are divided roughly into three sections: (a) biotech and pharmaceutical products,(b) industrial chemicals and VOC, and (c) metals.

Processes for production of ethanol and acetonebutanolethanol mixture from fermentation products in membranecontactor devices were presented in Refs. [88,89]. Recovery of butanol from fermentation was reported in Ref. [90]. Use ofcomposite membrane in a membrane reactor to separate and recover valuable biotechnology products was discussed inRefs. [91,92]. A case study on using membrane contactor modules to extract small molecular weight compounds of interestto pharmaceutical industry was shown in Ref. [93]. Extraction of protein and separation of racemic protein mixtures werediscussed in Refs. [94,95]. Extractions of ethanol and lactic acid by membrane solvent extraction are reported in Refs. [96,97].A membrane-based solvent extraction and stripping process was discussed in Ref. [98] for recovery of Phenylalanine.Extraction of aroma compounds from aqueous feed solutions into sunower oil was investigated in Ref. [99].



Extraction of phenol from aqueous solution using hollow ber membrane contactor was rst investigated in Ref. [100].However, the membrane used was not completely microporous. Instead, it was a dialysis-type membrane. A commercial plantto separate phenol from hydrocarbon fraction using microporous membrane contactors was reported in Ref. [101]. Soda lye wasused to react with the phenol transferred from the feed phase to create and maintain the driving force for separation. Thisindustrial-scale application enabled the processing of hydrocarbon fraction to a full-value raw material for phenol and acetonesynthesis.

The rst known commercial membrane-based liquidliquid extraction system involved extraction of by-products from awastewater stream using an aromatic solvent [102]. Before the membrane system was installed, the entire wastewater streamhad to be incinerated leading to high costs for the gas red incinerator per year. The membrane system lowered the contaminantconcentration to adequate levels before the biological wastewater treatment plant, and saved signicant operating cost.

A process to separate naphthenes from parafns is claimed in Ref. [103]. It involves the use of a polar solvent for separationin a microporous membrane device. Use of membrane extraction to remove p-nitrophenol in wastewater from dye and pesticidesynthesis was investigated in Ref. [104]. Removal of nonvolatile pesticide components from water is presented in Ref. [105].Removal of several important organic pollutants such as phenol, chlorophenol, nitrobenzene, toluene, and acrylonitrile fromwastewater was investigated in Ref. [106].

Removal of VOC contaminants from water was discussed in Ref. [107]. This particular process used sunower oil toabsorb the VOC compounds transferred from water across a gas-lled microporous membrane. However, to prevent anypossibility of liquid breakthrough, a plasma-polymerized di-siloxane coating was applied on the oil side of the membrane.Report [108] presents results from a pilot trial where organic pollutants such as chlorinated organic compounds and aromaticorganic compounds were removed from plant wastewaters.

Various investigators have also explored removal or recovery of metals from aqueous process or waste streams. Liquidliquid extraction is particularly useful for metal removal since alternate technologies such as distillation are not feasible.A process to separate molybdenum from tungsten leachate using a microporous membrane was disclosed in Ref. [109]. Copperextraction in a membrane contactor using metal chelating agent was presented in Ref. [110]. Other applications suggested inliterature include extraction of gold from aqueous solutions [111], removal of copper from edible oil [112], separation ofyttrium from heavy rare-earth metals [113], removal of copper and chromium from wastewater [114], and extractionsof mercury, copper, and nickel from water [115].

2.10 REVIEW OF MEMBRANE CONTACTOR DESIGN OPTIONS

Although membrane is the heart of the membrane contactor technology, appropriate internal design of the contactor device ormodule is critical for any commercial advancement of the technology. Internal design dictates how the two phases ow insidethe contactor and how the hydrodynamics in each phase is managed. As shown in Equation 2.2, the rate of mass transfer isdirectly dependent on the mass transfer coefcients in each of the phases, which in turn is dependent on the internalhydrodynamics. As the devices become larger to serve large commercial-scale process capacities, dependence on internalow management becomes more critical. The device design is also important in developing the processes for large-scalemanufacturing of the contactors. In the following section, we are reviewing various design options investigated over the years.

Designs of membrane contactors with hollow ber membranes fall in one of the two categories: (1) the primary uid beingtreated ows through the inside (lumen) of the hollow bers and (2) the primary uid being treated ows on the outside (shell)of the hollow bers. Another consideration is the ow direction of the uid in each phase with respect to the axis of themembrane and with respect to each other. In most membrane contactors of early commercial designs, the contactor housing wasof cylindrical shape with tube-in-shell conguration (as in tubular heat exchangers) where the primary uid ows on the lumenside from one end of the ber to the other and the other uid ows on the shell side in parallel direction. This design is generallycalled the parallel-ow design and is illustrated schematically in Figure 2.5a. The contactors of such a design are relatively easyto manufacture. However, the main drawback of the parallel-ow design is the nonuniform spacing of hollow bers and theresulting poor ow distribution or ow channeling on the shell side, particularly as the contactor diameter increases.

A signicant improvement over this parallel-ow design is the transverse-ow design where the primary uid ows onoutside of the hollow ber membrane at a transverse direction to the ber axis, while the other uid ows on lumen side of thehollow bers. The relative merits of the two designs were rst analyzed comprehensively in Ref. [116]. It determined thattransverse ow on shell side signicantly improves the mass transfer coefcient compared to the parallel-ow design.However, it was still difcult to ensure that the transverse ow on shell side is completely uniform along the ber length.Most investigations on membrane contactors continued to focus on parallel-ow design, since

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