Environmental Ion Exchange Principles and Design Anthony M. Wachinski, Ph.D., P.E. Director of Technology Transfer Thames Water Utilities The Woodlands, Texas James E. Etzel, Ph.D., P.E. Professor Emeritus Purdue University Lafayette, Indiana Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 1997 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works ISBN 13: 978-0-87371-956-8 (hbk) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. 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TD468.W22 1996 628.1'66-dc20 96-31353 CIP Library of Congress Card Number 96-31353 Cover design: Denise Craig DEDICATION Dr. Wachinski dedicates this book to his wife, Linda, for her sarcastic impatience and for betting her piggy-bank money of $82.45 that he would never get this done. PREFACE The purpose of this book is to concentrate as much ion exchange information as possible into one volume — the goal is for people to refer to the text as the “Ion Exchange Bible.” This book covers all ion exchange related design and application issues and includes tables, graphs, and conversion tables. We have also provided a review of the chemistry and hydraulics required for the design process. Through our work developing material for college-level ion exchange courses, we have found that a thorough knowledge of bar graphs and lime-soda softening is necessary and are including a chapter on these topics. We also provide engineering through extensive design examples, taking the reader through the entire design process. Each chapter is a stand-alone to allow the user rapid access to the topic of interest. Many chapters provide a reference section for further reading and research. Few books currently exist that cover ion exchange in such detail. Most ion exchange information is available either in a book chapter, in the commercial literature made available by resin manufacturing companies, or through articles and theses. During Dr. Etzel’s tenure as head of the environmental engineering area at Purdue University, he was noted as the leader in the practical application of ion exchange research and development. Dr. Etzel holds six patents dealing with ion exchange; Dr. Wachinski holds three. This book is intended as a text for undergraduate and graduate courses related to ion exchange, as a reference book on the topic, and for the engineer involved in providing cost-effective, innovative solutions to water/wastewater problems where ion exchange is an applicable alternative process for water/wastewater handling. Anthony M. Wachinski Table of Contents Preface Introduction and Historical Perspective....................................................................1 Chapter 1 Basic Concepts from General Chemistry and Fundamental Hydraulics.............3 Basic Chemistry Review............................................................................................3 Terminology.....................................................................................................3 Nomenclature...................................................................................................5 Grades of Chemicals.......................................................................................6 Dilutions ..........................................................................................................6 Lab Analysis.....................................................................................................6 pH......................................................................................................................7 Acidity...............................................................................................................8 Alkalinity..........................................................................................................8 Basic Hydraulics Review..........................................................................................9 Terminology.....................................................................................................9 Turbine.............................................................................................................10 Equations.........................................................................................................10 References.................................................................................................................13 Suggested Reading...................................................................................................13 Chapter 2 Cold Process Lime-Soda Softening........................................................................15 Hardness ...................................................................................................................15 Softening...................................................................................................................15 Basic Principles.........................................................................................................16 Bar Charts..................................................................................................................17 Example Problem and Solution..............................................................................18 Process Equations.....................................................................................................20 Example Problem and Solution..............................................................................22 References.................................................................................................................25 Chapter 3 Fundamental Principles and Concepts of Ion Exchange......................................27 Introduction...............................................................................................................27 Basics.........................................................................................................................27 Batch/Columnar Operation...........................................................................28 Basic Columnar Operation............................................................................28 Natural Ion Exchangers............................................................................................30 Synthetic Ion Exchangers........................................................................................31 Synthetic Cation Exchangers.......................................................................31 Synthetic Anion Exchangers.........................................................................36 Selectivity..................................................................................................................39 Order of Selectivity.......................................................................................39 Selectivity Determination..............................................................................43 Resin Structure.........................................................................................................43 Capacity.....................................................................................................................44 Particle Size...............................................................................................................46 Process Description..................................................................................................48 Backwash........................................................................................................48 Regeneration...................................................................................................48 Rinse................................................................................................................51 Service............................................................................................................51 Example Problems and Solutions...........................................................................52 References.................................................................................................................76 Chapter 4 Laboratory-Scale Testing of Ion Exchange...........................................................77 Introduction...............................................................................................................77 Columns ...................................................................................................................78 Reservoirs..................................................................................................................78 Column Operations..................................................................................................78 Flow Rates......................................................................................................79 Resin Conditioning........................................................................................81 Cautions..........................................................................................................83 Charging.........................................................................................................84 Backwashing...................................................................................................84 Regeneration...................................................................................................86 References.................................................................................................................88 Chapter 5 Ion Exchange Applications and Design.................................................................89 The Basic Flow Sheets.............................................................................................89 Demineralization......................................................................................................90 Flow Scheme Configurations.......................................................................90 Silica Removal...............................................................................................90 Degasification.................................................................................................90 Heavy Raw Water Composition...................................................................91 Plant Size........................................................................................................92 Cost of Regenerants......................................................................................92 Effluent Water Composition..........................................................................92 Flow Schemes...........................................................................................................92 Alkalinity Reduction Flow Schemes...........................................................98 Design........................................................................................................................99 Example Problem and Solution..............................................................................101 Industrial Flow Schemes........................................................................................108 Nickel Removal............................................................................................108 Chromium Removal.....................................................................................109 Ion Exchange as a Chemical Feeder....................................................................110 References...............................................................................................................110 Appendix: Tables and Conversion Factors.........................................................Ill Index .......................................................................................................................131 Introduction and Historical Perspective Ion exchange is probably one of the most widely used scientific phenomena in the world today, with applications in chemistry, biochemistry, manufacturing, soil-water interactions, medicine, and industrial and municipal water treatment, to name just a few. Specialized applications such as demineralization, deioniza­ tion, industrial water treatment, and chemical and water recovery are common. By following the historical development of ion exchange, one can learn about the natural and synthetic ion exchange materials used and developed through the years — many of these naturally occurring substances are now being evaluated as throw-away materials for ion exchange because of the problems associated with the handling and disposal of ion exchange regeneration wastewaters. Records indicate that the concept of ion exchange existed at least back to Aristotle’s time and possibly biblical times when Moses sweetened the waters of Marah. A recent interpretation of the miracle suggests that oxidized cellulose of the log that Moses cast into the waters had formed carboxyl groups that removed the “bitter” Epsom salt (magnesium sulfate) by an ion exchange reaction. Thus Moses succeeded in preparing drinking water, undoubtedly by an ion exchange technique he developed on an industrial scale (Exodus 15:23-25). Alchemists searched for a material (chemical) that would change seawater to drinking water long before Arrhenius proposed the existence of ions in water (circa 1887). Aristotle, circa 340 B.C., used 20 earthen vessels containing a material with ion exchange properties to produce fresh water. In 1850 the English agricultural chemist H. S. Thompson exchanged ammo­ nium ions for calcium ions by passing a solution of ammonium sulfate through a column of soil. When he added lime to the soil, the ammonium salt was released. In the same year, T. J. Way published an extensive report entitled “On the Power of Soils to Absorb Manure.” In 1854, some 33 years before Arrhenius published his concept of ionization, Way’s work was presented to the Royal Agricultural Society of London. We now know that the action of the soil’s double silicates, an important function in the regeneration of base exchange, makes the process practical. Subsequent investigations not only verified Way’s findings but devel­ oped new materials, in particular resinous compounds, which expanded even more the application of ion exchange. 1