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Industrial Electrochemistry to Pamela, Heather and Steven; Gill, Linda and Ian Industrial Electrochemistry

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Industrial Electrochemistry to Pamela, Heather and Steven; Gill, Linda and Ian Industrial Electrochemistry Industrial Electrochemistry To Pamela, Heather and Steven; Gill, Linda and Ian Industrial Electrochemistry SECOND EDITION Derek Pletcher Department of Chemistry, University of Southampton and Frank C. Walsh Department of Chemistry, Portsmouth Polytechnic First edition 1982 Paperback edition 1984 Second edition 1990 Paperback edition 1993 © 1982, 1984, 1990, 1993 Derek Pletcher and Frank C. Walsh Originally pub1ished by Blackie Academic & Professiona1 in 1993 Typeset in 1 0/12pt Times by Macmillan India Ltd, Bangalore 560 025 ISBN 978-0-7514-0148-6 ISBN 978-94-011-2154-5 (eBook) DOI 10.1007/978-94-011-2154-5 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the UK Copyright Designs and Patents Act, 1988, this publication may not be reproduced, stored, or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to the publishers at the Glasgow address printed on this page. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data available Contents Preface Vlll Symbols Xl 1 Fundamental concepts 1 1.1 Electron transfer 8 1.2 Mass transport 18 1.3 The interplay of electron transfer and mass transport control 30 1.4 Adsorption 32 1.5 Electrocatalysis 38 1.6 Phase formation in electrode reactions 48 1.7 Chemical reactions 50 1.8 The properties of electrolyte solutions 51 1.9 The assessment of cell voltage 54 1.10 Electrochemistry at surfaces on open circuit 55 Further reading 58 2 Electrochemical engineering 60 2.1 General considerations 60 2.2 Costing an electrolytic process 64 2.3 Performance and figures of merit 70 2.4 Electrolysis r.arameters 91 2.5 Principles of cell design 95 2.6 The additional technology of electrolytic processes 109 2.7 TypicaL-cell designs 141 2.8 Laboratory data and scale-up 166 Further reading 171 3 The chlor-alkali industry 173 3.1 General concepts of brine electrolysis 175 3.2 Modern technological developments 177 3.3 Chlorine cell technologies 184 VI Contents 3.4 The production of potassium hydroxide 208 Further reading 209 4 The extraction, refining and production of metal 210 4.1 Electrowinning 211 4.2 Cementation 228 4.3 Electrorefining 231 4.4 Electrodeposition of metal powders 245 Further reading 247 5 Other inorganic electrolytic processes 249 5.1 Fluorine 249 5.2 Water electrolysis 256 5.3 Sodium chlorate and sodium bromate 269 5.4 Peracids and their salts 274 5.5 Potassium permanganate 275 5.6 Potassium dichromate and chromic acid 278 5.7 Hydrogen peroxide 279 5.8 Ozone 282 5.9 Manganese dioxide 288 5.10 Cuprous oxide 290 5.11 Synthesis of metal salts via anodic dissolution 291 Further reading 292 6 Organic electrosynthesis 294 6.1 The hydrodimerization of acrylonitrile 298 6.2 Other commercial electro synthetic processes 311 6.3 Indirect electrosynthesis 326 6.4 The future of electro synthesis 329 Further reading 330 7 Water purification, effluent treatment and recycling of industrial process streams 331 7.1 Metal ion removal and metal recovery 333 7.2 Hypochlorite and low-tonnage chlorine electrolysers 353 7.3 Electrodialysis 358 7.4 The treatment of liquors containing dissolved chromium 364 7.5 Electrolytic methods of phase separation 374 7.6 Flue-gas desulphurization 379 7.7 Other electrochemical processes 382 Further reading 384 8 Metal finishing 385 8.1 Electroplating 386 8.2 Electroless plating 424 Contents VB 8.3 Conversion coatings 434 8.4 Electrophoretic painting 441 8.5 Other related surface-finishing techniques 447 Further reading 448 9 Metals and materials processing 451 9.1 Electroforming 451 9.2 Electrochemical machining 457 9.3 Electrochemical etching 468 Further reading 479 10 Corrosion and its control 481 10.1 Fundamentals of corrosion 483 10.2 The thermodynamics of corrosion 489 10.3 The kinetics of corrosion reactions 498 10.4 Corrosion problems in practice 509 10.5 Corrosion prevention and control 518 10.6 Corrosion problems in electrolytic processing 536 10.7 Corrosion measurement and monitoring 538 Further reading 541 11 Batteries and fuel cells 543 11.1 Battery characteristics 546 11.2 Battery specifications 551 11.3 Evaluation of battery performance 554 11.4 Battery components 555 11.5 Present battery systems 559 11.6 Batteries under development 584 11.7 Fuel cells 590 Further reading 595 12 Electrochemical sensors and monitoring techniques 596 12.1 Electrochemical procedures 596 12.2 Polarography to anodic stripping voltammetry 596 12.3 Ion-selective electrodes 603 12.4 Portable and on-line devices 609 12.5 Electrochemical biosensors 618 12.6 Electrochemical detector cells for high-performance liquid chromatography (HPLC) 624 12.7 Miscellaneous 634 Further reading 636 Index 639 Preface The objective of this second edition remains the discussion of the many diverse roles of electrochemical technology in industry. Throughout the book, the intention is to emphasize that the applications, though extremely diverse, all are based on the same principles of electrochemistry and electrochemical engineer­ ing. Those familiar with the first edition will note a significant increase in the number of pages. The most obvious addition is the separate chapter on electrochemical sensors but, in fact, all chapters have been reviewed thoroughly and many have been altered substantially. These changes to the book partly reflect the different view of a second author as well as comments from students and friends. Also, they arise inevitably from the vitality and strength of electrochemical technology; in addition to important improvements in tech­ nology, new electrolytic processes and electrochemical devices continue to be reported. In the preface to the first edition it was stated: ... the future for electrochemical technology is bright and there is a general expectation that new applications of electrochemistry will become economic as the world responds to the challenge of more expensive energy, of the need to develop new materials and to exploit different chemical feedstocks and of the necessity to protect the environment. The preparation of this second edition, seven years after these words were written, provided an occasion to review the progress of industrial electro­ chemistry. To our great pleasure, the conclusion is that despite the fact that energy has not become more expensive, the progress in terms of both improved technology and completely new processes and devices is very substantial. Improved membrane cell technology for the chlor-alkali industry, new processes for the manufacture of low-tonnage organic and inorganic chemicals, the appearance on the market of new lithium batteries and a variety of sensors, the coming of age of cathodic electropainting, many electrolytic processes for effluent treatment, the commercial availability of several families of electro­ chemical tells, etc. are all symptoms of a healthy technology. Preface IX Less satisfactory are the status of electrochemistry and electrochemical engineering as academic disciplines. They remain insufficiently taught at both undergraduate and postgraduate levels. Moreover, even when they appear within the syllabus, all too frequently one aspect of the subjects is covered to the exclusion of all others. It is a prime hope of both authors that this book will encourage many more teachers to take up the challenge of teaching an integrated applied electrochemistry course. Following the two introductory chapters, we have tried to use a similar approach for the discussion of the various groups of applications. We have sought to relate the technology to the underlying principles and to discuss current thinking and practice within the industries as well as to comment on likely future trends. We would wish to emphasize, however, that it is never our purpose to compare the technologies, cells or devices available from competing companies; the examples selected are based on our personal experiences and are in the text for illustration. We have also sought to describe only technology which has already reached industrial usage. Hence, we have always tried to avoid the temptation to outline the many other processes which have only been demonstrated in the laboratory or on a small pilot scale (otherwise the book would be in many volumes). We have attempted thereby, to produce a readable account of real industrial electrochemistry, useful to both students and those already engaged in the investigation of some aspect of the subject. In writing this book, many compromises had to be made. There have been many lively (but friendly) debates between the two authors and topics discussed have included the depth of treatment, the balance between fundamental and applied aspects and the choice of illustrative material. By far the most vexed topics were, however, those relating to signs, symbols and other conventions; throughout we were aware that the established practices of electrochemists, electroplaters, corrosion engineers, materials technologists and chemical en­ gineers were quite different and they also depended on the country of origin. In these very unfortunate circumstances, authors are bound to offend most readers. In some desperation we decided to follow a system which will be most readily acceptable to electrochemists since we expect them to be our largest group of readers. Most of all, we have endeavoured to achieve uniformity.
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