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Hydrometallurgy

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Hydrometallurgy Principles and applications

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Tomás Havlík

Cambridge International Science Publishing Limited in association with Woodhead Publishing Limited CRC Press Boca Raton Boston New York Washington, DC

W OODHEAD

PUBLISHING LIMITED

Cambridge, England

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Published by Cambridge International Science Publishing Limited in association with Woodhead Publishing Limited Cambridge International Science Publishing Limited, 7 Meadow Walk, Great Abington, Cambridge CB21 6AZ, England www.cisp-publishing.com Woodhead Publishing Limited, Abington Hall, Granta Park, Great Abington, Cambridge CB21 6AH, England www.woodheadpublishing.com Published in North America by CRC Press LLC, 6000 Broken Sound Parkway, NW, Suite 300, Boca Raton, FL 33487, USA First published 2008, Cambridge International Science Publishing Ltd, Woodhead Publishing Limited and CRC Press LLC © 2008, Cambridge International Science Publishing Limited The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the authors and the publishers cannot assume responsibility for the validity of all materials. Neither the authors nor the publishers, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Cambridge International Science Publishing Limited and Woodhead Publishing Limited. The consent of Cambridge International Science Publishing Limited and Woodhead Publishing Limited does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from either Cambridge International Science Publishing Limited or Woodhead Publishing Limited for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress. Woodhead Publishing ISBN 978-1-84569-407-4 (book) Woodhead Publishing ISBN 978-1-84569-461-6 (e-book) CRC Press ISBN 978-1-4200-7044-6 CRC Press order number: WP7044 The publishers’ policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp which is processed using acidfree and elementary chlorine-free practices. Furthermore, the publishers ensure that the text paper and cover board used have met acceptable environmental accreditation standards. English translation by Cambridge International Science Publishing Ltd Typeset by Thymus Solutions Ltd, Mumbai, India Printed by TJ International Limited, Padstow, Cornwall, England

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Contents

Introduction ....................................................................................... xi 1.

Current situation in copper production ...................................1

1.1.

Copper hydrometallurgy ........................................................................ 11

2.

Ore minerals ........................................................................... 17

3.

Phase equilibrium of copper and iron sulphides .......................................................................... 29

3.1. 3.1.1. 3.1.1.1. 3.1.1.2. 3.2. 3.2.1. 3.2.2. 3.2.3.

4.

Equilibrium in aqueous solutions .......................................... 60

4.1. 4.1.1. 4.1.1.1. 4.1.1.2. 4.1.2. 4.1.2.1. 4.1.2.2. 4.1.2.3. 4.1.2.4. 4.2. 4.3. 4.3.1.

5. 5.1. 5.1.1. 5.1.2. 5.2. 5.2.1.

One-component systems ....................................................................... 29 Sulphur .................................................................................................... 29 Allotropic modifications of solid sulphur ............................................ 32 Phase diagram ......................................................................................... 37 Multi-component systems ..................................................................... 38 The copper–sulphur equilibrium phase system ................................... 38 The iron–sulphur equilibrium phase system ........................................ 43 The copper–iron–sulphur equilibrium phase system .......................... 48

Ionic activities ........................................................................................ 65 Debye–Hückel theory ............................................................................ 65 Extension to more concentrated solutions ........................................... 69 Extension to mixed electrolytes ............................................................. 71 Pitzer method .......................................................................................... 72 Calculation of φ for salts in mixed electrolytes ..................................... 76 Calculation of γ for salts in mixed electrolytes ..................................... 78 Calculation of γ for single ions ............................................................ 79 Studies of complex systems ................................................................... 80 Formation of metallic complexes and equilibrium constant ................ 81 Thermodynamics of equilibrium constants .......................................... 85 Selection of the values of equilibrium constants ................................. 91

Thermodynamic studies of heterogeneous systems in an aqueous medium ........................................................... 96 Theoretical principle of the E–pH diagrams ....................................... pH and its principle .............................................................................. Potential E and its principle ................................................................. Calculation and construction of E–pH diagrams ............................... E–pH diagrams at elevated temperatures ........................................... v

100 102 104 113 116

5.3. 5.3.1. 5.3.2. 5.3.3. 5.3.4. 5.3.5. 5.3.6. 5.3.7. 5.4.

Potential–pH diagrams in leaching of copper sulphides ................... S–H2O equilibrium system ................................................................... Cu–S–H2O equilibrium system ............................................................ Fe–S–H2O equilibrium system ............................................................. Cu–Fe–S–H2O equilibrium system ...................................................... Cu–S–Cl–H2O equilibrium system ....................................................... Fe–S–Cl–H2O equilibrium system ....................................................... Equilibrium diagram of the Cu–Fe–S–Cl–H2O system ....................... Species diagrams ..................................................................................

127 129 145 153 154 157 159 163 167

6.

Software and databases for thermodynamic calculations 173

7.

Kinetics of heterogeneous reactions of leaching processes .............................................................................. 184

7.1. 7.2. 7.2.1. 7.2.1.1. 7.2.1.2.

8. 8.1.

9.

Effect of variables on the kinetics of a heterogeneous reaction ...... Elementary phenomena at the interface .............................................. Intrinsic kinetics of heterogeneous reactions on solid surfaces ...... Kinetics of processes of leaching a single particle ........................... Kinetics of leaching processes in multi-particle systems .................

190 211 216 216 228

Leaching in chloride media ................................................. 242 Main aspects of leaching chalcopyrite in a chloride medium ........... 243

Extracting metals from solutions ....................................... 255

9.1. 9.2. 9.3. 9.4. 9.5. 9.6. 9.7. 9.8. 9.8.1. 9.8.2.

Cementation .......................................................................................... Cementation of amalgams .................................................................... Reduction with gaseous hydrogen ..................................................... Liquid extraction ................................................................................... Ion exchange ......................................................................................... Precipitation of sparingly soluble compounds .................................. Crystallisation ...................................................................................... Electrolysis and electrolytic refining .................................................. Electrowinning of metals ...................................................................... Electrolytic refining ..............................................................................

10.

Effect of the electronic structure on leaching of sulphide semiconductors ..................................................... 294

10.1. 10.1.1.

11. 11.1.

255 259 261 264 268 270 274 276 278 289

Leaching kinetics and electrochemistry of sulphides ....................... 300 Leaching of chalcopyrite ..................................................................... 301

Experimental methods of investigating hydrometallurgical processes .............................................................................. 309 Experimental methods of examination of leaching processes ........... 315 vi

11.1.1. 11.1.2. 11.2.

12. 12.1. 12.1.1. 12.1.2. 12.1.3. 12.1.4. 12.1.5. 12.1.6. 12.1.7. 12.2. 12.3.

Leaching equipment ............................................................................. 318 Experimental procedure ........................................................................ 324 Changes of pH in relation to temperature .......................................... 334

Leaching of copper sulphides ............................................. 341 Copper sulphides of the CuxFeyS z type ............................................... 341 Leaching of chalcopyrite by ferric sulphate ...................................... 361 Leaching of chalcopyrite by ferric chloride ....................................... 364 Leaching of chalcopyrite by ferric chloride with the addition of carbon tetrachloride ............................................................................. 366 Leaching of chalcopyrite in sulphuric acid using ozone as the oxidation agent ..................................................................................... 368 Leaching of chalcopyrite in the high-frequency field ....................... 375 Leaching of chalcopyrite in the microwave field ............................... 378 Leaching of chalcopyrite in the presence of deep nodules as an oxidation agent ..................................................................................... 384 Copper sulphides of the CuxS type ..................................................... 388 Copper sulphides of the type CuxMe ySz ............................................................................... 398

13.

Morphology and behaviour of sulphur in the leaching of sulphides ........................................................................... 421

14.

Study of the fine structure ................................................... 444

14.1.

Examples of the application of X-ray diffractometry in hydrometallurgy ................................................................................... 446

15.

Mechanism of leaching of copper sulphides in an acid medium .................................................................................. 468

16.

The current state and prospects of hydrometallurgical processes .............................................................................. 479

16.1.

History of hydrometallurgical processes ............................................ 484

Index ............................................................................................... 535

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This book is devoted to the life and work of Univ. Prof. Dr.Ing. Dr. h.c. mult. Roland Kammel – a friend, to whom I am very grateful not only for his support in my professional field but especially for his human approach.

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Introduction The procedures used for processing minerals containing metallic elements to metals of the required purity for specific applications are generally referred to as extraction metallurgy. A large number of procedures have been developed for this purpose and, at first sight, it is quite difficult to determine the optimum method of extraction of metals. A suitable guide may be the concept in the first sentence, i.e., the purity of produced metals often depends on the procedures used for processing primary and secondary raw materials. Some of the processes can be used only for producing relatively contaminated metals, whereas others are quite efficient in producing metals of almost 100% purity. Each process can be used to produce metals with a wide range of purity. To understand how a specific process may lead to the extraction of metals with the required composition, it is necessary to take into account theoretical considerations regarding the principles controlling the rate and extent of chemical reactions taking place in the process. Thermodynamics defines the final, i.e., equilibrium state of these reactions and can be used to study how the final state can be changed by changing the given conditions, such as temperature, the pressure and composition of gaseous, liquid and solid components in the given system. On the other hand, the kinetics defines the rate at which the equilibrium state is established and this also indicates the reaction time required for the realisation and completion of the essential chemical reactions. The investment and production costs are a very important factor and determine the selection of the optimum process. Metals are traded on the open market and, consequently, from the commercial viewpoint it is not possible to determine the specific method of production of metals of the given composition with respect to the actual price of a specific production process. In addition, the prices are also controlled by other aspects, such as the cost of environmental protection, processing and marketing of secondary products, recycling, etc. These factors develop dynamically and in many cases it is difficult to forecast their contribution to the total xi

price of metal, even for the near future. In any case, only the efficiently mastered theoretical fundamentals and applications of the most advanced achievements of science to the process of production of metals and also all other operations and the logistics of these processes lead to more efficient production enabling the producer to be successful in the market. Therefore, special attention is given to the search for and development of new, often unconventional methods of producing and processing metals, or combinations of these metals. An alternative method to the existing pyrometallurgical processes is the hydrometallurgical extraction of nonferrous metals. Some metals, such as uranium, zinc, gold or aluminium oxide, etc, are extracted completely or mostly by the hydrometallurgical method, whereas in other methods the application of this method is more difficult because of objective reasons. This is so in the case of copper, which is one of the most important nonferrous metals. Therefore, this book is concerned especially with the hydrometallurgical method of obtaining copper from its sulphide minerals, in particular, with one of its most important stages – leaching. The individual chapters deal in a logical manner with this method, in order to understand the entire range of the problems of leaching copper sulphide minerals. After initial introduction, subsequent chapters review the interesting sulphide minerals, present in the leaching process as the raw material, semifinished products, or the leaching product. This is followed by the description of the thermodynamics of leaching of copper sulphides from the general viewpoint and also with respect to practical application, using the potential–pH diagrams. Attention is then given to the leaching kinetics, again from the general viewpoint and with respect to specific applications in sulphide leaching. The applications and the current state of the problem of leaching copper sulphides are dealt with in subsequent sections of the book. Special attention is given to the behaviour of sulphur in the leaching process, as one of the most important and process-controlling factors. Final sections describe interesting technological procedures which were used or are being used on the pilot plant and production scale, and prospects for the future are also discussed. The book is based mainly on the fundamental and cited literature. Although basic knowledge of inorganic and physical chemistry is essential, together with the knowledge of the theory of metallurgical processes, the book also presents the main concepts to such an xii

extent that it can be used as a textbook for students of all stages of metallurgy and related disciplines. The book is intended not only for students but also for a wide range of experts, working in the hydrometallurgy of nonferrous metals. It is constructed in such a manner as to ensure that the general conclusions may also be applied to similar processes in metallurgy or applied chemistry. The author will be delighted if this is the case.

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Current situation in copper production

CHAPTER 1 CURRENT SITUATION IN COPPER PRODUCTION Copper has always played a significant role in the history of mankind and directed development so significantly that one entire era of the development of mankind is referred to as the Bronze Age. Figure 1.1 shows the history of application of copper and copper alloys BC. At the present time, the amount of copper produced annually is approximately 12 000 kt and continuously increases. Figure 1.2 summarises the trend in the increase of production of refined copper on the worldwide scale. However, this trend does not take into account the production of copper in the countries of the former Eastern Bloc [1]. The current production of copper is concentrated mainly in the processing of sulphide (mostly chalcopyrite or mixed) concentrates by the pyrometallurgical method. The method consists of two operations: melting, including the production of raw copper, and refining, ensuring the production of refined metal with the purity of at least 99.9% Cu. The pyrometallurgical production of copper (general flow chart is shown in Fig. 1.3) includes the following operations of production of pure copper from sulphide concentrates. Roasting. The sulphide concentrate is roasted at a strictly controlled temperature with limited access of air in order to remove part of sulphur by roasting. Subsequently, the resultant roasted product is melted. At present, the roasting process is no longer used in pyrometallurgical production of copper because of the introduction of advanced autogenous processes. Production of matte. In this operation, the roasted product is melted in a shaft furnace at a temperature of approximately 1200 °C, resulting in melting of the sulphides and the formation of the so-called copper matte. The molten tailings form a slag in the

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Hydrometallurgy British Isles Cu 2000 Cu-As Cu-Sn 1600 Cu-Sn-Pb 1000

China Cu 2500-2000 Cu-Sn 1500 Cu-Sn-Pb 1000 Cu-Zn 10 AC

Scandinavia Cu Cu-Sn

1500

Central Europe Cu 2200 Cu-As Cu-Sn 1700 Cu-Sn-Pb

Troy

Cu Cu-Sn Cu-Sn-Pb

3000 2500 1800

Cu Cu-Sn

2500 2000

Cu Cu-Sn Cu-Zn-Sn

1800 2000 1800

Crete

Caucasus Maikop-Kuban

Cu Cu-As Cu-Sn

Anatolia Turkey

Cu Cu-Sn

7000 ? 2500

Cyprus

Iberian peninsula Cu 2500 Cu-As-Sn 1700 Cu-Sn 1600

2500 2200 1800

Iran, Turkmenistan Sialk-Hissar-Anau

Cu ca.4000 Cu-As 2300 Cu-Sn 1300 Cu-Sn-Pb 1000

Palestine

Mesopotamia

Cu ca. 3800 Cu-Sn 2000 Cu-Sn-Zn 1400

Cu 4000 Cu-Sn 2800 Cu-Sn-Pb 1000

Al Ubaid etc

Egypt Cu Cu-Sn Cu-Sn-Pb Cu-As Cu-Zn

4000 2800 2300 1800 30

India Mokenjo-Daro Harappa

Cu Cu-As Cu-Sn

3000 2800-2300

Fig. 1.1. Historic review of the application of copper and copper alloys.

presence of slag-forming additions, enabling separation of undesirable impurities. Refining of the matte. The copper matte is in fact a melt of copper and iron sulphides. The iron is separated in processing in a converter by blowing air with oxygen, or pure oxygen, resulting in the oxidation of iron because of its higher affinity to oxygen and 2

Current situation in copper production 12000

Production in eastern Europe not included

Copper production [t × 103 ]

11000

Source: WBMS

10000

9000

8000

7000 1986

1988

1990

1992

1994

1996

1998

2000

Year Fig. 1.2. Development of production of refined copper worldwide.

subsequent transfer of the iron oxide into the slag in the presence of slag-forming additions. Convertering. In a converter, sulphide sulphur is removed by blowing air or oxygen into the melt, and sulphur reacts to form volatile oxides and copper is transferred into converter copper. Fire refining. The aim of this operation is to remove the residual sulphur in a rafination furnace in two stages: in the first stage, sulphide is oxidised into volatile oxides by air or enriched air, and the second stage is characterised by the removal of the oxygen bonded with a metal in the first period, using birch logs, or with gaseous hydrocarbons. This operation is referred to as pooling. Electrolytic refining. In this operation, all the residual impurities are removed from copper by electrolysis. Many of these impurities, trapped in the so-called anode sludge, are important components and, consequently, the anode sludge is further treated in order to recover them. Electrolytic refining results in the removal of impurities such as silver, gold, platinum metals, selenium, tellurium, nickel, arsenic, bismuth, lead, etc. 3

Hydrometallurgy

Although the general flow chart of pyrometallurgical production of copper, shown in Fig.1.3, is relatively simple and cheap and has been used for many years, it greatly differs from optimum requirements. The most important shortcomings include: Unsuitable thermal balance. Some of the processes, such as roasting, matte refining and converter treatment, are exothermic, whereas matter formation is endothermic. The heat, generated by exothermic processes, is not utilised in endothermic processes resulting in an unsuitable thermal balance. However, in modern practices, oxidising smelting in suspension or bath smelting reactors, roasting, matte formation and separation take place in the same unit and in connection with each other and the whole process is highly exothermic. Unsuitable design of the system. The flame furnaces are far less efficient than the shaft furnaces from the viewpoint of the transfer of heat and matter. They do not ensure efficient contact of the hot gases with the charge and produce excessive amounts of flue dust, carried away by the gases, because of the use of the dust charge. Ineffective manipulation with materials. The liquid converter slag is usually recycled in the flame furnace in order to remove copper from the slag. Since the slag contains a large amount of magnetite, the gradual buildup of the latter requires, after some time, shutting down the furnace and the removal of magnetite. Contamination of the environment. The copper melting plants produce large amounts of sulphur oxides emitted into the atmosphere. Whilst the sulphur dioxide, formed in roasting and converter treatment, is relatively concentrated and may be used for the production of sulphuric acid, the sulphur dioxide formed in the flame furnace is characterised by a low concentration (0.1–0.2%). The latter is processed either to produce sulphuric acid or is neutralised with limestone. The large volume of the gases, emitted into the atmosphere from this source, is a serious environmental problem. Copper losses. The copper losses into the slag in the flame furnace are proportional to the richness of the matte. Therefore, in order to minimise the losses, copper-rich matte is used only seldom. Processing and liquidation of waste. The metallurgical production of copper is characterised by the formation of very large amounts of slags with very large quantities of copper. However, the concentration of copper is low and this prevents efficient processing of the slags. In addition to the copper, the waste dumps 4

Current situation in copper production

Ore

Crushing Milling Flotation

Tailings

Roasting

SO 2

Air

SO 2 Matte production

Slag

Matte refining

SO 2

Air

Converting

SO 2

Air

Desulphurisation

SO 2

Deoxidation

CO 2

Quartz Air Slag

Reduction agent

Anode casting Electrolytic refining Impurities and noble metals

Copper

Fig. 1.3. General scheme of pyrometallurgical production of copper.

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