Industrial Electrochemistry

668 Pages·1993·15.875 MB·English

by  Derek Pletcher, Frank C. Walsh (auth.)

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
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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.
Finally, it is a pleasure to thank the many who have helped us in the
preparation of this book. The most obvious are those who have kindly
persuaded their organizations to release the photographs which illustrate the
text. There are, however, many other industrialists and academics who have
provided source material. We also feel that we owe much gratitude to the many
who have stimulated our interest in applied electrochemistry. In the case of one
of us (D.P.) special mention should be made of Professor Martin Fleischmann
(University of Southampton) and Dr Gordon Lewis (associate and guide
during a survey of industrial electrochemistry carried out in 1979). The other
(F.C.W.) would wish to single out Dr Des Barker (Portsmouth Polytechnic),
x Preface
Dr David Gabe (University of Loughborough) and Professor Martin Fleisch
mann, as particularly strong influences in his training. We are both also aware
of our debt to several companies who have given us practical training in the most
acceptable way - they have paid us as consultants! Thanks are due to Susan
Neale and David Jackson of the Frewen Library, Portsmouth Polytechnic who
checked the lists of further reading at the end of each chapter. Our typists are also
remembered with many thanks. Lastly, we wish to acknowledge the debt to our
families, especially our wives who have suffered extra duties to allow the
completion of this book, but also our parents and children for their contributions
to our contented writing.
Derek Pletcher
Frank Walsh