Advanced Chemical Methods for Soil and Clay Minerals Research NATO ADVANCED STUDY INSTITUTES SERIES Proceedings of the Advanced Study Institute Programme, which aims at the dissemination ofa dvanced knowledge and the formation of contacts among scientists from different countries The series is published by an international board of publishers in conjunction with NATO Scientific Affairs Division A Life Sciences Plenum Publishing Corporation B Physics London and New York C Mathematical and D. Reidel Publishing Company Physical Sciences Dordrecht, Boston and London D Behavioural and Sijthoff & Noordhoff International Social Sciences Publishers E Applied Sciences Alphen aan den Rijn and Germantown U.S.A. Series C - Mathematical and Physical Sciences Volume 63 - Advanced Chemical Methods for Soil and Clay Minerals Research Advanced Chemical Methods for Soil and Clay Minerals Research Proceedings of the NATO Advanced Study Institute held at the University ofI llinois, July 23 - August 4, 1979 edited by J. W. STUCKI and W. L. BANWART Univer$ity of1 1linoi$, Urbana, Rlinoi$, U.S.A. D. Reidel Publishing Company Dordrecht : Holland / Boston: U.S.A. / London: England Published in cooperation with NATO Scientific Affairs Division library of Congress Cataloging in Publication Data Main entry under title: Advanced chemical methods for soil and clay minerals research. (NATO advanced study institutes series: Series C, Mathematical and physical sciences; v. 63) "Published in cooperation with NATO Scientific Affairs Division." Includes index. 1. Soil mineralogy-Methodology-Congresses. 2. Clay minerals Research-Congresses. 3. Soils-Analysis-Congresses. 4. Clay-Analysis Congresses. I. Stucki, J. W. II. Banwart, Wayne L. III. Illinois. University at Urbana-Champaign. IV. North Atlantic Treaty Organization. Division of Scientific Affairs. V. Series. S592.55.A38 631.4'16 80-23081 ISBN-I3: 978-94-009-9096-8 e-ISBN-I3: 978-94-009-9094-4 DOl: 10.1007/978-94-009-9094-4 Published by D. Reidel Publishing Company P. O. Box 17, 3300 AA Dordrecht, Holland Sold and distributed in the U.S.A. and Canada by Kluwer Boston Inc., 190 Old Derby Street, Hingham, MA 02043, U.S.A. In all countries, sold and distributed by Kluwer Academic Publishers Group, P.O. Box 322,3300 AH Dordrecht, Holland D. Reidel Publishing Company is a member of the Kluwer Group All Rights Reserved Copyright © 1980 by D. Reidel Publishing Company, Dordrecht, Holland Softcover reprint of the hardcover 1st edition 1980 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any informational storage and retrieval system, without written permission from the copyright owner TABLE OF CONTENTS PREFACE ..................................................... )vii 1. MOSSBAUER SPECTROSCOPY - Bernard A. Goodman 1-1. I ntroduction to the Mossbauer Effect .... 1 1-2. Basic PrinCiples of Mossbauer Spectroscopy .. 7 1-3. Instrumentation and Experimental Procedures. 19 1-4. Application of Mossbauer Spectroscopy to the Study of Silicate Minerals .......... . 28 1-5. The Study of Mineral Alteration Reactions 45 1-6. Iron Oxides and their Characterization in Soils 65 1-7. Critical Assessment of the Potential of Mossbauer Spectroscopy, and its Application to Nuclei Other than I ron 80 References . . . . . . . . . . . . . . . . . . . . 90 2. NEUTRON SCATTERING METHODS OF INVESTIGATING CLAY SYSTEMS- D.K. Ross and P.L. Hall 93 2-1. Introduction . . . . . . . . . . . . . . . . . . . 93 2-2. Elementary Neutron Scattering Theory ..... 99 2-3. Neutron Scattering Instrumentation and Methods 130 2-4. Applications of Neutron Spectroscopy to Studies of Clay Minerals ............ . 138 Appendix 2-1. Macroscopic Cross Section for a Montmorillonite-Water System ...... . 160 Appendix 2-2. Calculation of Incoherent Scatt'ering Intensity Ratios for a Clay-Water System 162 References . . . . . . . . . . . . . . . . . . . . . 163 3. INTRODUCTION TO X-RAY PHOTOELECTRON SPECTROSCOPY- C. Defosse and P.G. Rouxhet 169 3-1. Introduction ..... 169 3-2. Trend of XPS Spectra 171 3-3. Instrumentation 175 3-4. Peak Position . 177 3-5. Explored Depth 182 3-6. Peak Intensity 185 3-7. Overview of Methods of Characterization of Solids Based on X-ray, Electron and Ion Beams 193 References . . . . . . . . . . . . . . . . . . . . . . . . 201 vi TABLE OF CONTENTS 4. APPLICATION OF X-RAY PHOTOELECTRON SPECTROSCOPY TO THE STUDY OF MINERAL SURFACE CHEMISTRY - M.H. Koppelman 205 4-1. Uniqueness of XPS for the Investigation of Mineral Surface Phenomena - Probing Depth .......... 205 4-2. Sample Handling Techniques. . . . . . . . . . . . . . . 206 4-3. Analytical Applications ................. 211 4-4. Electron Take-Off (Grazing) Angle Analysis Applications 216 4-5. Qualitative Bonding Investigations 220 4-6. Summary 241 References . . . . . . . . . . . . . . . 242 5. THE APPLICATION OF NMR TO THE STUDY OF CLAY MINERALS - J.J. Fripiat ..... 245 5-1. Introduction: Fundamentals of NMR 245 5-2. The Bloch Equations ........ . 254 5-3. Line Shape . . . . . . . . . . . . . . 262 5-4. Relaxation Mechanisms ...... . 282 5-5. Review of Some Problems: Order and Disorder in Adsorbed Water Molecules 303 References . . . . . . . . . . . . . . . . . . . . . . 314 6. DISTRIBUTION OF IONS IN THE OCTAHEDRAL SHEET OF MICAS - W.E.E. Stone and J. Sanz 317 6-1. Introduction . . . . . . . 317 6-2. Influence of the Fe2+ Ions 318 6-3. H+ Spectra of Phlogopites 319 6-4. H+ Spectra of Biotites .. 321 6-5. F- Spectra . . . . . . . . 322 6-6. Correlation with I. R. Results . 324 References . . . . . . . . . . . . . 328 7. GENERAL THEORY AND EXPERIMENTAL ASPECTS OF ELECTRON SPIN RESONANCE - Jacques C. Vedrine 331 7-1. Introduction .... . 331 7-2. G-Factor Tensor ... . 340 7-3. Hyperfine Interaction . 353 7-4. Analysis of ESR Spectra 362 7-5. Fine Structure .... . 368 7-6. Summary ....... . 373 Appendix 7-1 375 Appendix 7-2 377 Appendix 7-3 381 References . . 386 TABLE OF CONTENTS vii 8. APPLICATIONS OF ESR SPECTROSCOPY TO INORGANIC-CLAY SYSTEMS - Thomas J. Pinnavaia 391 8-1. Introduction . . . . . . . . . . . 391 8-2. Surface-Bound Metal Ions .... 391 8-3. Framework Paramagnetic Centers 407 References . . . . . . . . . . . . . . . 419 9. APPLICATION OF SPIN PROBES TO ESR STUDIES OF ORGANIC-CLAY SYSTEMS - Murray B. McBride 423 9-1. Nitroxide Spin Probes - Origin of the ESR Spectrum . . . . ..... . 423 9-2. Nitroxides in Low-Viscosity Media - Rapid Isotropic Motion ...... . 427 9-3. Nitroxides in High-Viscosity Media 429 9-4. Nitroxides Adsorbed on Clay Surfaces 437 9-5. Experimental Considerations in Using Nitroxide Spin Probes 447 References . . . . . . . . . . . . . . . . . 449 10. APPLICATIONS OF PHOTOACOUSTIC SPECTROSCOPY TO THE STUDY OF SOILS AND CLAY MINERALS - Raymond L. Schmidt 451 10-1. Introduction. . 451 10-2. Instrumentation 454 10-3. Results 456 10-4. Conclusions 463 References . . . . 465 INDEX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 467 PREFACE During the past few years there has been a marked increase in the use of advanced chemical methods in studies of soil and clay mineral systems, but only a relatively small number of soil and clay scientists have become intimately associ ated and acquainted with these new techniques. Perhaps the most important obstacles to technology transfer in this area are: 1) many soil and clay chemists have had insufficient opportunities to explore in depth the working principles of more recent spectroscopic developments, and therefore are unable to exploit the vast wealth of information that is available through the application of such ad vanced technology to soil chemical research; and 2) the necessary equipment gen erally is unavailable unless collaborative projects are undertaken with chemists and physicists who already have the instruments. The objective of the NATO Advanced Study Institute held at the University of Illinois from July 23 to August 4, 1979, was to partially alleviate these obstacles. This volume, which is an extensively edited and reviewed version of the proceedings of that Advanced Study Institute, is an essential aspect of that purpose. Herein are summarized the theory and most current applications of six different spectroscopic methods to soil and/or clay mineral systems. The instrumental methods examined are Mossbauer, neutron scattering, x-ray photoelectron (XPS, ESCA), nuclear magnetic resonance (NMR), electron spin resonance (ESR, EPR), and photoacoustic spectroscopy. Contributing authors were also lecturers at the Advanced Study Institute, and are each well known and respected authorities in their respective disciplines. The importance and timeliness of using modern chemical methods in soil and clay research was emphasized recently by Dr. R.C. McKenzie in his plenary address at the Sixth International Clay Conference (Oxford, 1978), in which he referred to several of these methods as holding much promise for opening new horizons. This importance was also recognized in a symposium on "New Methods in Soil Min eralogical Investigations," sponsored by the Soil Science Society of America in 1977, in which two of these methods were discussed. The number of scientific publications using these methods to study soils and clays is increasing at a rapid rate, and the time is right to collect into one volume a detailed discussion of all of these methods. It is hoped that in doing this, a critical void in the scientific literature will be filled, and that the ability of earth scientists to take advantage of a greater variety of research instruments for solving difficult problems will thereby be increased. Special acknowledgement is made to the following publishers for their gener osity in permitting reproduction of figures: Academic Press, Inc.; Almquist and Wiksell International; American Chemical Society; American Institute of Physics; American Mineralogist; American Physical Society; American Society of Agron- ix J. It!. Stucki and W. L. Banwart reds.), Advanced Chemical Methods for Soil and Clay Minerals Research, ix-x. Copyright © 1980 by D. Reidel Publishing Company. x PREFACE omy; American Vacuum Society; Blackwell Scientific Publications, Ltd.; Cam bridge University Press; The Chemical Society; The Clay Minerals Society; Elevier Scientific Publishing Company; Gauthier-Villars; Harper and Row Publishers, Inc.; Institut Max von Laue-Paul Langevin; International Atomic Energy Agency; John Wiley and Sons, Inc.; The Macauley Institute for Soil Research; Macmillan (Jour nals) Ltd.; McGraw-Hili Book Company; Masson; The Mineralogical Society; Min eralogical Society of America; North-Holland Publishing Co.; Oxford University Press; Pergamon Press, Inc.; Plenum Publishing Corporation; Program for Scientific Translation; Societe Chimique de France; Springer-Verlag; United Kingdom Atomic Energy Authority; and Zeitschrift fur Kristallographie. The editors express deep and sincere gratitude to Judith Kutzko for type setting the camera-ready manuscript; and to Sandra Ripplinger who spent many hours proofreading and correcting the individual chapters. We acknowledge the support and magnificent assistance of Dr. Carol Holden and the Division of Con ferences and Institutes at the University of Illinois, without whom the Advanced Study Institute and this volume could never have become reality. We also express appreciation to Dr. R.W. Howell, Head of the Agronomy Department, and to other members of the Department who offered much encouragement during the many weeks of preparing this work. Finally, we again thank the authors who contributed so generously of their time and talents to make this work worthwhile. J.W. Stucki W. L. Banwart July, 1980 Chapter 1 MOSSBAUE R SPECTROSCOPY Bernard A. Goodman Department of Spectrochemistry The Macaulay Institute for Soil Research Aberdeen AB9 20J, United Kingdom 1-1. INTRODUCTION TO THE MOSSBAUER EFFECT The 'Y-radiation emitted by nuclei in excited states, formed as a result of radioactive decay of unstable parent nuclei, may subsequently be reabsorbed by other nuclei of the same type. If the emitting nucleus is assumed to be moving with a velocity, V, so that the linear momentum of the system is mY, where m is the mass of the nucleus, then, after emission of the 'Y-ray, the linear momentum of the system, which comprises the 'Y-ray plus de-excited nucleus, must still equal mV (conservation of momentum). Thus the momentum of the 'Y-ray, E/c, must be balanced by a change in the velocity of the nucleus so that, mV = E'Y/c + m(V+v) [ 1-11 and v is thus equal to --E'Y/mc and is independent of the initial velocity of the atom. Also considering the conservation of energy, the kinetic energy of the nu cleus before emission of the 'Y-ray is %mV2 and after emission is %m(V+v)2. Thus the difference in energy, /j E, between the nuclear transition energy and that of the emitted 'Y-ray is given by /j E = %mv2 + m Vv [1-21 %mv2 = E 2/2mc2 = E [1-31 'Y r where Er is the free atom recoil energy and is independent of the velocity of the nucleus. Recoil of the nucleus also occurs on absorption of radiation and resonant absorption can only occur if overlap exists between the energy profiles of the emitted and absorbed 'Y-rays. With free atoms the recoil energy, Er, is much greater than the widths of these absorption profiles (Fig. 1-11. If the nuclei are held in a lattice in which the characteristic energy of the lattice vibrations (the phonon energy) is greater than J. W. Stucki and W. L. Banwart (eds.), Advanced Chemical Methods for Soil and Clay Minerals Research, 1-92. Copyright © 1980 by D. Reidel Publishing Company.