Inorganic Ion Exchange Materials Editor Abraham Clearfield, Ph.D. Professor of Inorganic Chemistry Department of Chemistry Texas A & M University College Station, Texas Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business First published 1982 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 Reissued 2018 by CRC Press © 1982 by CRC Press, Inc. CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works 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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CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging in Publication Data Main entry under title: Inorganic ion exchange materials. Bibliography Includes index. 1. Ion exchange resins. I. Clearfield, Abraham. QD561.I55 541.3’723 81-6109 ISBN 0-8493-5930-9 AACR.2 A Library of Congress record exists under LC control number: 81006109 Publisher’s Note The publisher has gone to great lengths to ensure the quality of this reprint but points out that some imperfections in the original copies may be apparent. Disclaimer The publisher has made every effort to trace copyright holders and welcomes correspondence from those they have been unable to contact. ISBN 13: 978-1-315-89446-1 (hbk) ISBN 13: 978-1-351-07356-1 (ebk) Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Dedication To my beloved wife Ruth who, though schooled in the Liberal Arts, must suffer my affection for the sciences. CONTRIBUTORS Mitsuo Abe, Ph.D. Umberto Costantino, Ph.D. Professor Assistant and Professor of General and Department of Chemistry Inorganic Chemistry Faculty of Science Department of Chemistry Tokyo Institute of Technology University of Perugia Tokyo,Japan Perugia, Italy Giulio Albert!, Ph.D. Full Professor of General and Inorganic Arthur T. Howe, Ph.D. Chemistry Department of Inorganic and Structural Member of the Italian Chemical Society Chemistry University of Perugia University of Leeds Perugia, Italy Leeds, England Aleksandar Ruvarac, Ph.D. The Head of Chemical Dynamics Laboratory Institute for Nuclear Sciences "Boris Kidric" Institute Belgrade, Yugoslavia * Present Address Amoco Research Center Naperville, Illinois TABLE OF CONTENTS Chapter 1 Zirconium Phosphates 1 Abraham Clear!ield Chapter 2 Other Group (IV) Acid Salts 75 Guilio Alberti Chapter 3 Intercalation Behavior of Group IV Layered Phosphates Ill Umberto Costantino Chapter 4 Uranyl Phosphates 133 Arthur T. Howe Chapter 5 Group IV Hydrous Oxides — Synthetic Ion Exchangers 141 Aleksandar Ruvarac Chapter 6 Oxides and Hydrous Oxides of Multivalent Metals as Inorganic Ion Exchangers ... 161 Mitsuo Abe Index 275 Chapter 1 ZIRCONIUM PHOSPHATES Abraham Clearfield TABLE OF CONTENTS I. Introduction 2 II. Structural Studies on Zirconium Bis (Monohydrogen Orthophosphate) Monohydrate 3 A. Crystal Structure 3 B. Infrared Studies 5 III. Preparation and Characterization of Zirconium Phosphate 6 A. Preparation 6 B. Methods of Characterizing Zirconium Phosphate 8 1. Thermal Methods 9 2. Heat of Formation 11 3. X-Ray Methods 12 4. Particle Size Determination 12 5. Surface Titrations 13 6. Ion Exchange Characterization 14 IV. Ion Exchange Properties 16 A. Amorphous Zirconium Phosphate 16 1. Enthalpy and Entropy Changes 18 B. Crystalline a-Zirconium Phosphate 20 1. Exchange of Alkali Metal Cations 20 a. Thermodynamics of Exchange 20 b. Ion Exchange Mechanism 24 c. Multiple Ion Systems 28 2. Exchange of Alkaline Earth Cations 29 3. Exchange of First Row Transition Metal Ions 30 4. Ammonium Ion Exchange 30 5. Silver Ion Exchange 32 C. Ion Exchange Reactions on Expanded Layer Zirconium Phosphates . .33 1. Exchange with ZrNaH(PO ) • 5H O (NaH • 5H O) 33 4 2 2 2 a. Alkali Metal Ions 33 b. Sodium Ion Catalysed Exchange 34 c. Alkaline Earth Cations 35 d. Transition Metal Ions 35 e. Trivalent Cations 36 f. Exchange of Ammonium and Silver Ions 37 g. Exchange of Oxocations 37 2. Exchange with 0-ZrP 37 a. Alkali Metal Cations 38 b. Divalent Cations 38 3. Exchange with Amine Intercalates 38 2 Inorganic Ion Exchange Materials D. Exchange with Zr(MPO ) • nH O Phases 39 4 2 2 1. Exchange in Fused Salts 41 E. Semicrystalline a-Zirconium Phosphate 43 F. Surface Exchange 43 G. Kinetics 44 1. Rates of Exchange 44 2. Self-Diffusion Studies 46 3. Solid-Solid Ion Exchange 47 H. Zirconium-Titanium Phosphates 48 V. Dehydrated and High Temperature Phases of o-Zirconium Phosphate 48 VI. Electrochemical Properties of a-Zirconium Phosphate 50 A. Ionic Conductivity 50 B. Membranes 55 C. Conductivity of Salt Forms 56 VII. y-Zirconium Phosphate 57 A. Preparation 57 B. Structural Considerations 58 C. Thermal Behavior .58 D. Ion Exchange Properties 58 1. Alkali Metal Cations 58 2. Divalent Ions 59 E. Organic Derivatives 59 VIII. Applications 60 A. Renal Dialysis 60 B. Ion Exchange 61 C. Water Softening 61 D. Chromatography 61 E. Catalysis 62 1. Surface Acidity and Alcohol Dehydration 62 2. Synthesis of Methyl Isobutyl Ketone 63 3. Miscellaneous Reactions 64 4. Metals Supported on Zirconium Phosphate 64 F. Membranes and Solid Electrolytes 65 References 66 I. INTRODUCTION It is now more than twenty years since reports of ion exchange behavior of zirconium phosphate gels first appeared in the chemical literature.1"3 Since that time, research into the nature of this and similar compounds has continued unabated. Part of the impetus for this effort resulted from the discovery that zirconium and titanium phos- phates could be prepared in crystalline form.4 5 In the interim many other layered group (IV) phosphates and arsenates have been crystallized and studied as well as doz- ens of exchanged forms.6 78 In addition, there are now quite a number of known phases of zirconium phosphate.9 Furthermore, the original one, zirconium bis(monohydrogen orthophosphate), can be obtained as a gel, as single crystals, and in all intermediate stages of crystallinity.10 For all of these products the ion exchange behavior differs, being a function of the crystallinity and structure. Thus, it is a mis- take to consider zirconium phosphates as a single compound. It is essential to an un- derstanding of the observed behavior that the exchanger be properly characterized. We shall attempt to do this as far as possible so that some reasonable correlation between structure and behavior may emerge. Several excellent reviews have already appeared.6 7911 However, in the recent past, exciting new developments in the areas of surface chemistry, catalysis, electrochemis- try, and fast ion conduction have taken place. These new findings need to be integrated with the already extensive knowledge of zirconium phosphates in a systematic way. It is hoped that the present treatment will achieve this objective. II. STRUCTURAL STUDIES ON ZIRCONIUM BIS(MONOHYDROGEN ORTHOPHOSPHATE) MONOHYDRATE A. Crystal Structure Addition of a soluble Zr(IV) salt to phosphoric acid results in the precipitation of a gelatinous, amorphous solid of variable composition and properties (see Section III.A). However, a stoichiometric crystalline compound, Zr(HPO ) 'H O, can be pre- 4 2 2 pared by refluxing these gels in strong phosphoric acid."9 The crystals so formed range in size between 0.1 and 10 /^m and are too small for single crystal studies. Larger crystals may be grown hydrothermally in quartz tubes or teflon-lined pressure vessels at 170 to 200°C.12 A novel way of growing large crystals was developed by Alberti and Torracca.13 It depends upon the fact that Zr(IV) forms soluble complexes with excess fluoride ions. To such a solution is added phosphoric acid, but not to the point of precipitation. On heating this mixture, the fluoride reacts with silicon from the glass container and is slowly removed as a volatile silicon fluoride. Thus, slow precipitation of zirconium phosphate occurs as the fluoride is depleted. The crystals prepared by either of the above methods will be referred to as o-ZrP. The crystal structure of a-ZrP was initially solved by X-ray film methods'2 and later using a data set obtained with an automated diffractometer.14 In the first case the space group was chosen as P2,/c and later it was more convenient to refine the struc- ture in P2,/n. Both sets of unit cell dimensions are given in Table 1, together with cell dimensions determined by others. The observed variation in unit cell dimensions will be discussed after a description of the structure is given. a-Zirconium phosphate has a layered structure.12 '4 The metal atoms lie very nearly in a plane (±0.25 A to the mean plane) and are bridged by phosphate groups. These are situated alternately above and below the metal atom plane. Three oxygen atoms of each phosphate group are bonded to three different zirconium atoms which form a distorted equilateral triangle. Each zirconium atom is thus octahedrally coordinated by oxygens. An idealized picture of a portion of the layer is shown in Figure 1. It is seen that if the metal atoms were located in the mean plane that a psuedohexagonal arrangement would result with a unit cell a* = 5.24 A, C = 22.6 X and D point A 3d symmetry. The actual interlayer distance is 7.55 A. The two phosphate groups are not equivalent, one of them being more tilted in relation to the mean plane of the layer than the other. Reference to Figure 1 shows that the alternating metal and phosphate arrangement forms twelve-membered rings in a crown arrangement. These rings consist of three phosphorus atoms, three metal atoms, and six oxygen atoms (heavy outline in Figure 1). If the phosphorus atoms are below the mean plane, then the ring is capped by a phosphate group above the plane and vice versa. The whole arrangement assumes an open cup-like form. Adjacent lay- ers are shifted relative to each other by 1/3 a , 2/3c . This places one twelve-membered h fc ring capped on the top over another capped on the bottom, the whole making a six-