ENHANCED METAL RECOVERY FROM A

MODIFIED CARON LEACH OF MIXED

NICKEL-COBALT HYDROXIDE.

Andrew Jones

B.Sc. (Applied Chemistry), Hons (Mineral Science)

This thesis is presented for the degree of Doctor of Philosophy of Murdoch

University

2013

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I declare that this thesis is my own account of my research and contains as

its main content work which has not previously been submitted for a degree

at any tertiary educational institution.

………………………

Andrew Jones

December 2013

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ABSTRACT

In the last 20 years nickel laterites have become a popular resource due to

the economic expansions of China and India, an improvement in processing

technologies and the large unexploited orebodies around the world. The

development of a split process, producing a metal hydroxide intermediate, is

becoming popular as it lowers technical risk and capital costs. Following on

from Cawse, BHP Billiton have been instrumental in developing this process,

and produced a mixed hydroxide precipitate for approximately a year (2008)

at Ravensthorpe in Western Australia, which was processed in an ammonia

solution at the existing Yabulu refinery in Townsville Queensland. This PhD

project focused on the ageing of the precipitate which would occur during

transportation, and the subsequent leaching in an ammonia-ammonium

carbonate solution with a sulphide (CoNiS) reductant.

Metal ion hydroxides were discovered to precipitate within the pores of

magnesium hydroxide (precipitant). This meant that the precipitate particle

size was relatively large, oxidation of cobalt and manganese occurred

throughout the particles and the dissolution rate followed a shrinking core

model. Although cobalt and manganese oxidation was envisaged to be a

problem, only ~8% of cobalt and ~52% of manganese oxidised in a

Ravensthorpe sample after 12 weeks and was leached in 45 minutes in the

presence of a reductant. All oxidation occurred during precipitation, filtration

and preparation of the precipitate.

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The formation of stable slow leaching nickel-magnesium hydroxide and

hydrotalcite-like structures did affect nickel and cobalt recoveries. Reducing

the incorporation of magnesium, increasing the manganese concentration

and drying the precipitate all reduced the effect of the nickel-magnesium

hydroxide. Drying the precipitate could result in a saving in transportation

costs, while increasing the manganese concentration would lower reagent

costs and energy consumption. Aluminium, chromium(III) and sulphate

concentrations needed to be minimised to reduce the effect of hydrotalcite-

like structures. Sulphate may need to be precipitated from solution prior to

metal hydroxide precipitation.

The reaction mechanism of the reduction of high valent metal ions by mixed

cobalt nickel sulphide reductant (CoNiS) produced on-site at Yabulu was

investigated. The extent of reduction was directly related to the Co:S ratio,

however the presence of NiS was crucial as it had a faster rate of dissolution

and introduced sulphur species into solution. The ideal ratio of cobalt to

nickel was between 2:1 and 3:1. The site survey of Yabulu revealed the

potential of the leach liquors needed to be monitored to ensure cobalt existed

in the trivalent state, which is more soluble. HPLC (High Performance Liquid

Chromatography) results showed that numerous cobalt ammine species

were present in solution. As unwanted cobalt precipitation is a major cause

of lower metal recoveries and the final product is influenced by solution

chemistry, the results will help improve cobalt recovery and product grade.

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ACKNOWLEDGEMENTS

This project was originally proposed and constructed by Dr. Nicholas

Welham (Murdoch University) and Peter Anderson (BHP Billiton Yabulu

Refinery). It was Nick who suggested I commence the PhD, and through his

supervision over the years is the main reason it has actually come together.

His trust and his relaxed, honest style of supervision made him a delight to

work with. Associate Professor Gamini Senanayake was adopted as the

primary supervisor in 2008 when Nick moved to Ballarat University. Although

extremely busy, he always had time for me and was incredibly patient. His

vast experience with PhD students meant his advice through the writing

process was very valuable.

John Fittock at the Yabulu Refinery was the industry supervisor. John has

been very helpful over the years, dedicating a large amount of time to spend

with me, to answer questions and organise site visits. A genuine person and

with over 25 years of experience at the Refinery he was very knowledgeable.

Kirsten Smith, Joy Morgan, Leslie Chegwidden, Chris Nethercott and Sandra

Bessel have all helped in some way on visits to the refinery, particularly

Kirsten and Joy who spent an awful amount of time with me.

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The network of the Mineral Science department, friends and family are

another major reason this project has come to completion. Advice from staff

and fellow students, and enthralling conversations over a cup of coffee or

lunch made it a joy to be at the university. My network of friends, always

interested in doing something, has made life outside of uni very enjoyable.

Finally, Greg, Kerry, Sarah and Amy your love and support is felt, and greatly

appreciated.

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RESEARCH PUBLICATIONS

Jones, A.N. and Welham, N.J.

Properties of aged mixed nickel-cobalt hydroxide intermediates produced

from acid leach solutions and subsequent metal recovery.

Hydrometallurgy 103(2010): 173-179.

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GLOSSARY Term Definition λmax wavelength of maximum absorption Area 340 Ore leaching and washing Area 345 MHP leaching and CoNiS precipitation Area 352 Stripping stills and gas recovery ASX ammoniacal solvent extraction

CCD Counter Current Decantation; a process for separating pregnant leach liquor from tailings in a series of thickeners

CoNiS cobalt-nickel sulphide ECoR Enhanced Cobalt Recovery EN European Nickel FLL fresh leach liquor

Free NH3 free NH3 = titrated NH3 – 6 x 17 / 58.7 x [Ni + Co] – 2 x 17 / 44 x [CO2]

Hexammine (hexa) hexamminecobalt(III), [CoIII(NH3)6]3+

HPLC high performance liquid chromatography Hydrotalcite Mg6Al2(OH)16CO3.4H2O ICP inductively coupled plasma Leached pulp mix of leached ore and leachate (leach discharge solution)

MES Report Online lab results submitted by the Quantitative Analysis Laboratory

Metsim Program used to model concentrations and flow rates for the refinery

MHP mixed hydroxide precipitate nm nanometer ORP oxidation-reduction potential

Oxidise to increase the oxidation state of an element or compound, remove electrons

Pentammine (penta) pentammine(carbonato)cobalt(III), [CoIII(NH3)5CO3]+

PL product liquor ppm parts per million

Preboil process step in which Product Liquor is steam stripped to lower the ammonia content from ~90 g/L to ~40 g/L

Preboil solids precipitate formed in the preboil process, comprising manganese, iron, nickel, cobalt and magnesium hydroxides and carbonates

Reduce to decrease the oxidation state of an element or compound, add electrons

RNO Ravensthorpe Nickel Operations RCPT reductive complexing predictor leach test RPT reductive predictor leach test RSPT reductive soak predictor leach test SAC synthetic ammonium carbonate SPL special product liquor

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SPT standard predictor leach test SSPT standard soak predictor leach test Sulfato pentammine(sulphato)cobalt(III), [CoIII(NH3)5SO4]+ Sulfito pentammine(sulphito)cobalt(III), [CoIII(NH3)5SO3]+ Tailings final residue from the leaching process Tetrammine (tetra) tetrammine(carbonato)cobalt(III), [CoIII(NH3)4CO3]+

Thiosulphato pentammine(thiosulphato)cobalt(III), [CoIII(NH3)5S2O3]+

Titratable NH3 ammonia content of a solution determined by direct acid titration

Total NH3 NH3 content of a solution determined by Kjeldahl analysis, includes NH4

+ XRD X-ray diffraction YEP Yabulu Expansion Project

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TABLE OF CONTENTS 1 INTRODUCTION ................................................................................. 1-1

1.1 Nickel Ores .................................................................................. 1-1 1.2 Processing Laterite Ores ........................................................... 1-2

1.2.1 Major Routes ......................................................................... 1-2 1.2.2 Pressure Acid Leaching (PAL) Process ................................. 1-5 1.2.3 Ammoniacal Carbonate Leaching (Caron) Process .............. 1-8

1.3 Commercial PAL Processes .................................................... 1-10 1.3.1 Proposed and Piloted Processes ........................................ 1-11 1.3.2 Murrin Murrin, Bulong and Cawse ....................................... 1-12 1.3.3 Ravensthorpe Project and Yabulu Extension ...................... 1-13 1.3.4 Current/Future Projects ....................................................... 1-18

1.4 Project Aim................................................................................ 1-19

2 LITERATURE REVIEW ....................................................................... 2-1

2.1 Laboratory Synthesis of Metal Hydroxides .............................. 2-1 2.1.1 Nickel Hydroxide ................................................................... 2-1 2.1.2 Cobalt Hydroxide ................................................................... 2-8 2.1.3 Manganese Hydroxide ........................................................... 2-9 2.1.4 Magnesium Hydroxide ......................................................... 2-11 2.1.5 Mixed Metal Hydroxides ...................................................... 2-12 2.1.6 Comparison of Precipitating Agents .................................... 2-16

2.2 Commercial Production of Mixed Nickel-Cobalt Hydroxide . 2-16 2.2.1 Cawse – Original Flowsheet ................................................ 2-16 2.2.2 Ravensthorpe Process ........................................................ 2-17 2.2.3 Ramu Process ..................................................................... 2-19 2.2.4 European Nickel Process .................................................... 2-20 2.2.5 Niquel do Vermelho Process ............................................... 2-20 2.2.6 Comparison of Flowsheets .................................................. 2-21

2.3 ‘Ageing’ of MHP ........................................................................ 2-22 2.3.1 Formation of High-Valent oxides ......................................... 2-23 2.3.2 Formation of Insoluble or Slow-Leaching Compounds ........ 2-27 2.3.3 Other Possible Ageing Processes/Influences ...................... 2-30

2.4 Drying MHP ............................................................................... 2-31 2.5 Chemistry of Leaching of MHP in SAC Solutions .................. 2-32

2.5.1 Three Stage Leaching Process ........................................... 2-32 2.5.2 Metal Ammine Complexes ................................................... 2-33 2.5.3 Measured Metal Ion Solubility ............................................. 2-39 2.5.4 Leach Kinetics ..................................................................... 2-42 2.5.5 Impurities in MHP ................................................................ 2-43 2.5.6 Reductive Leaching of MHP ................................................ 2-45 2.5.7 Effect of Soaking ................................................................. 2-47

2.6 Metal Sulfides as Reducing Agents ........................................ 2-48 2.6.1 Precipitation Process ........................................................... 2-48 2.6.2 Precipitation Kinetics ........................................................... 2-50 2.6.3 Practical Difficulties ............................................................. 2-51 2.6.4 Reducing Properties ............................................................ 2-52

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3 MATERIALS AND METHODS .......................................................... 3-1 3.1 Reagents and Industry Samples ............................................... 3-1 3.2 Synthesis of Mn3O4 ..................................................................... 3-1 3.3 Synthesis of MnOOH .................................................................. 3-4 3.4 Precipitation of MHP .................................................................. 3-5

3.4.1 Precipitates for the Effect of Composition ............................. 3-5 3.4.2 Precipitates for the Effect of Drying ....................................... 3-8 3.4.3 Simple Metal Hydroxides ....................................................... 3-8 3.4.4 Nickel-Magnesium Hydroxide for Solubility Testing ............... 3-9 3.4.5 Transformation of MgO to Mg(OH)2 ...................................... 3-9 3.4.6 Influence of Magnesium Content ........................................... 3-9 3.4.7 Influence of Ageing of Mixed Nickel-Magnesium Hydroxide .. 3-9 3.4.8 Influence of Co, Mn, Al and Cr ............................................ 3-10 3.4.9 Influence of Cobalt(II) and Cobalt(III) Valency ..................... 3-11 3.4.10 Influence of Crystallinity ....................................................... 3-12 3.4.11 Precipitates for Oven Ageing ............................................... 3-12 3.4.12 Elevated Temperature Precipitation .................................... 3-14 3.4.13 Precipitation Mechanism ..................................................... 3-15

3.5 CoNiS Preparation .................................................................... 3-16 3.6 Leach Tests ............................................................................... 3-19

3.6.1 Synthetic Ammonium Carbonate (SAC) Leach Solution ...... 3-19 3.6.2 Predictor Leach Tests ......................................................... 3-20 3.6.3 Modified Predictor Leach Tests ........................................... 3-22 3.6.4 Reductive Leaching of Oxidised Mn and Co Hydroxides ..... 3-24 3.6.5 Batch Leach Tests ............................................................... 3-24 3.6.6 Kinetic Leach Tests ............................................................. 3-25 3.6.7 Effect of Anions on Ni(II) Solubility ...................................... 3-26

3.7 Analysis ..................................................................................... 3-27 3.7.1 Moisture Content ................................................................. 3-28 3.7.2 Determination of Extent of Oxidation ................................... 3-29 3.7.3 Atomic Absorption Spectrometry ......................................... 3-30 3.7.4 Inductively Coupled Plasma Mass Spectrometry ................ 3-30 3.7.5 X-Ray Diffraction ................................................................. 3-30 3.7.6 Neutron Diffraction .............................................................. 3-31 3.7.7 Scanning Electron Microscopy ............................................ 3-32 3.7.8 Optical Microscopy .............................................................. 3-33 3.7.9 Thermogravimetric Analysis ................................................ 3-33 3.7.10 Laser Size Analysis ............................................................. 3-33 3.7.11 BET Surface Area Tests ...................................................... 3-34 3.7.12 Infrared and Raman Spectroscopy ...................................... 3-34 3.7.13 High Performance Liquid Chromatography ......................... 3-35 3.7.14 X-Ray Photoelectron Spectroscopy ..................................... 3-35

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4 SYNTHESIS, CHARACTERISATION AND REDUCTIVE LEACHING OF OXIDISED MANGANESE AND COBALT HYDROXIDES ........... 4-1

4.1 Introduction and Experimental .................................................. 4-1 4.2 PrecipitationCharacterisation of a Single Phase MnOOH ....... 4-3 4.3 Reductive Leaching of MnOOH and Mn3O4 with NH2OH and

Co(II). ........................................................................................... 4-6 4.4 Reductive Leaching of Mn3O4 with Sulfite and Co(II). ........... 4-11 4.5 Reductive Leaching of Mixed Oxidised Mn-Co Hydroxide

with Sulphite and Co(II). .......................................................... 4-14 4.6 Summary ................................................................................... 4-18

5 CHARACTERISICS AND PROPERTIES OF MgO AND SYNTHETIC MIXED HYDROXIDE PRECIPITATES ............................................... 5-1

5.1 Introduction and Experimental .................................................. 5-1 5.2 Composition and Properties of MgO ........................................ 5-3

5.2.1 Chemical Analysis and Size Distribution ............................... 5-3 5.2.2 Dissolution of MgO and Reprecipitation Mg(OH)2 ................. 5-4 5.2.3 Rate of Hydration of MgO ...................................................... 5-7

5.3 Synthetic MHP ............................................................................ 5-8 5.3.1 Mechanism of Precipitation ................................................... 5-8

5.4 Effect of pH and Initial Metal Solution Concentration on MHP Composition .................................................................... 5-14

5.4.1 Precipitation Diagrams ........................................................ 5-14 5.4.2 Effect of Initial Metal Ion Concentration ............................... 5-17 5.4.3 Effect of Cobalt and Manganese ......................................... 5-20 5.4.4 Discussion of Assay Results ............................................... 5-22 5.4.5 Effect of Cation Softness ..................................................... 5-26 5.4.6 Variation of Ni/Mg and Co/Mn Molar Ratio .......................... 5-29

5.5 Size Distribution of MHP .......................................................... 5-32 5.6 Moisture Content ...................................................................... 5-37 5.7 Extent of Oxidation During Ageing ......................................... 5-40 5.8 X-Ray Diffraction Patterns ....................................................... 5-47

5.8.1 Effect of Ageing of MHP ...................................................... 5-47 5.8.2 Effect of Ageing on Crystalline Ni-Mg Hydroxide ................. 5-58 5.8.3 Effect of Anions on Oven Ageing of Mixed Hydroxides ....... 5-60 5.8.4 Effect of Precipitation at Elevated Temperatures ................ 5-64

5.9 Scanning Electron Microscopy ............................................... 5-71 5.9.1 Synthetic MHP ..................................................................... 5-71

5.10 Summary ................................................................................... 5-75

6 LEACHING OF SYNTHETIC HYDROXIDE PRECIPITATES………6-1 6.1 Introduction and Experimental .................................................. 6-1 6.2 Effect of Ageing on Leaching .................................................... 6-3 6.3 Effect of metal Ion Composition on Leaching .......................... 6-5

6.3.1 General Comparison ............................................................. 6-5 6.3.2 Effect of Magnesium, Cobalt and Manganese on Leaching .. 6-8 6.3.3 Nickel-Cobalt Correlation ..................................................... 6-16 6.3.4 Effect of Al, Fe, Cr(VI), Zn, Cu & Si in the Absence of Mn.. 6-21

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6.4 X-Ray Diffraction of Leach Residues ...................................... 6-25 6.5 Effect of Drying, Ageing and Heating ..................................... 6-31

6.5.1 Effect of Moisture Content ................................................... 6-31 6.5.2 Effect of Ageing Dried Precipitates ...................................... 6-39 6.5.3 Effect of Heating Precipitates .............................................. 6-41

6.6 Leaching Kinetics of Synthetic MHP ...................................... 6-45 6.6.1 Mathematical Expressions for Kinetic Analysis ................... 6-45 6.6.2 Porosity of Starting Material ................................................ 6-47 6.6.3 Effect of Crystallinity ............................................................ 6-49 6.6.4 Effect of Particle Size .......................................................... 6-53 6.6.5 Effect of Magnesium Content .............................................. 6-54 6.6.6 Effect of Oxidation of Co(II) ................................................. 6-58 6.6.7 Effect of Other Metal Ions and Crystallinty .......................... 6-61

6.7 Summary and Conclusions ..................................................... 6-70

7 CHARACTERISATION AND LEACHING OF COMMERCIAL MIXED HYDROXIDE PRECIPITATES ........................................................... 7-1

7.1 Introduction and Experimental .................................................. 7-1 7.2 Composition and Characterisation ........................................... 7-3

7.2.1 Chemical Analysis ................................................................. 7-3 7.2.2 Collection and Size Analysis of RNO MHP ............................ 7-5 7.2.3 X-Ray and Neutron Diffraction Analysis of RNO MHP .......... 7-7 7.2.4 SEM and EDS of RNO MHP ............................................... 7-11

7.3 Oxidation States of Mn and Co in RNO MHP.......................... 7-16 7.4 Ageing and Drying of RNO-MHP ............................................. 7-20 7.5 Leaching Kinetics of RNO MHP ............................................... 7-22 7.6 Predictor Leach Test Results .................................................. 7-31

7.6.1 General Comparison of Different Commercial Precipitates . 7-31 7.6.2 Effect of composition on Standard Predictor Test Results .. 7-35 7.6.3 Predictor Leach Test Results - Preboil Solids Sample ........ 7-38 7.6.4 Predictor Leach Test Results – RNO Pilot Plant MHP ........ 7-39 7.6.5 Predictor Leach Test Results - Cawse MHP ....................... 7-42 7.6.6 Predictor Leach Test Results - European Nickel MHP ........ 7-44 7.6.7 Predictor Leach Test Results of RNO-June Sample ........... 7-48

7.7 Summary and Conclusions ..................................................... 7-52

8 REDUCTIVE LEACHING OF MIXED HYDROXIDE PRECIPITATE WITH COBALT-NICKEL-SULFIDES (CoNiS) ................................... 8-1

8.1 Introduction ................................................................................. 8-1 8.2 Precipitation and Characterisation of CoNiS .......................... 8-2

8.2.1 Precipitation Diagrams .......................................................... 8-2 8.2.2 Precipitation and Analysis ..................................................... 8-3 8.2.3 XRD and SEM of CoNiS ........................................................ 8-8

8.3 Redox Behaviour of Sulfides in SAC solutions ..................... 8-10 8.3.1 Redox Behaviour of Elemental Sulphur and Sulphide ions . 8-11 8.3.2 Redox/dissolution Behaviour of NiS and CoS ..................... 8-15 8.3.3 Redox/dissolution Behaviour of CoNiS ................................ 8-21 8.3.4 Relative Dissolution of Ni(II) and Co(II) from CoNiS ............ 8-24 8.3.5 ORP of NiS, CoS and CoNiS in SAC Solutions ................... 8-25

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8.4 Reductive Leaching of MnOOH by CoNiS in SAC Solution .. 8-27 8.5 Summary and Conclusions ..................................................... 8-34

9 YABULU REFINERY PLANT SURVEY .............................................. 9-1 9.1 Introduction and Experimental .................................................. 9-1 9.2 Yabulu Flowsheets ..................................................................... 9-3 9.3 Oxidation Reduction Potentials (ORP) ..................................... 9-7 9.4 XRD of Plant Solids .................................................................. 9-11 9.5 Cobalt Speciation in Plant Liquors ......................................... 9-18 9.6 Cobalt Speciation in Batch Leach Tests of MHP ................... 9-24 9.7 Secondary Leaching of MHP with CoNiS ............................... 9-33 9.8 Summary and Conclusions ..................................................... 9-35

10 SUMMARY, CONCLUSIONS AND FUTURE WORK ....................... 10-1 10.1 Precipitation Mechanism ......................................................... 10-1 10.2 Composition of Precipitates .................................................... 10-2 10.3 Oxidation During Precipitation ................................................ 10-2 10.4 Slow Leaching Compounds in MHP ....................................... 10-3 10.5 Remedies to Improve MHP Leaching ...................................... 10-4 10.6 Leaching Kinetics of MHP........................................................ 10-6 10.7 Precipitation of CoNiS .............................................................. 10-7 10.8 Yabulu Plant Survey ................................................................. 10-7 10.9 Future Work .............................................................................. 10-8

REFERENCES APPENDIX

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LIST OF FIGURES Figure 1.1. Simplified flowsheet of Caron process. .................................... 1.9 Figure 1.2. Ravensthorpe flowsheet. ....................................................... 1.15 Figure 1.3. Flowsheet of the Yabulu refinery with MHP processing circuit .................................................................................................................. 1.16 Figure 2.1. A solubility diagram of metal hydroxides at 25°C .................... 2-12 Figure 2.2. Brucite and hydrotalcite structure. .......................................... 2-24 Figure 2.3. Eh-pH diagram of Co-H2O and Mn-H2O systems for 0.01 M Mn(II) and 0.1 M Co(II). ....................................................................................... 2-25 Figure 2.4. Hydrotalcite structure. ............................................................. 2-29 Figure 2.5. Potential-pH diagrams for Ni-NH3-H2O system at 25°C and 1 atm. 1. Ni(NH3)2+; 2. Ni(NH3)2

2+; 3. Ni(NH3)32+; 4. Ni(NH3)4

2+; 5. Ni(NH3)52+;

6. Ni(NH3)62+. a) activity of ionic species is unity, b) activity of ionic species is

10-2, c) activity of ionic species is 10-4. ...................................................... 2-36 Figure 2.6. Potential-pH diagrams for Co-NH3-H2O system at 25°C and 1 atm. 1. Co(NH3)2+; 2. Co(NH3)2

2+; 3. Co(NH3)32+; 4. Co(NH3)4

2+; 5. Co(NH3)5

2+; 6. Co(NH3)62+. a) activity of ionic species is unity, b) activity of

ionic species is 10-2, c) activity of ionic species is 10-4. ............................. 2-37 Figure 2.7. Eh-pH diagram of Ni-ammonia-carbonate system at 30°C. .... 2-38 Figure 2.8. Eh-pH diagram of Co-ammonia-carbonate system at 30°C .... 2-38 Figure 2.9. Eh-pH diagram of Mn-ammonia-carbonate system at 30°C ... 2-39 Figure 2.10. Nickel(II) carbonate solubility at 45°C depending on ammonia concentration and NH3:CO2 ratio .............................................................. 2-40 Figure 2.11. Cobalt(II) hydroxide solubility at 45°C depending on ammonia concentration and NH3:CO2 ratio .............................................................. 2-40 Figure 2.12. Manganese(II) chloride solubility at 45°C depending on ammonia concentration and NH3:CO2 ratio............................................... 2-41 Figure 2.13. Iron(II) chloride solubility at 45°C depending on ammonia concentration and NH3:CO2 ratio .............................................................. 2-41 Figure 2.14. Sulphide solubility diagram at 25°C ...................................... 2-49 Figure 3.1. Dropwise addition of NaOH to manganese solution. ................ 3-3

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Figure 3.2. Manganese hydroxide precipitate and solution after overnight air sparging ...................................................................................................... 3-3 Figure 3.3. Refluxing to produce MnOOH. .................................................. 3-4 Figure 3.4. Precipitation of mixed hydroxides. ............................................ 3-6 Figure 3.5. Precipitates stored in sample jars. ............................................ 3-7 Figure 3.6. Bottles used for oven ageing. ................................................. 3-13 Figure 3.7. Picture of elevated temperature precipitation.......................... 3-15 Figure 3.8. Effect of H2S:Co stoichiometry in thickener-2 overflow on Yabulu-CoNiS composition .................................................................................. 3-18 Figure 3.9. Reactors used for leach tests. ................................................ 3-21 Figure 3.10. Mill drive used for modified predictor tests. ........................... 3-23 Figure 3.11. Clips on mill drive holding centrifuge tubes. .......................... 3-24 Figure 3.12. Vessel in oven used for drying. ............................................. 3-28 Figure 3.13. Stubs prepared for SEM ....................................................... 3-32 Figure 3.14. Precipitates embedded in resin blocks for SEM and EDS analysis ..................................................................................................... 3-33 Figure 4.1. XRD scans of various products formed during manganite precipitation ................................................................................................ 4-5 Figure 4.2. XRD scans of Mn3O4, MnOOH and a mixture. .......................... 4-6 Figure 4.3. Extent of reduction of Mn3O4, a mixture and MnOOH in SAC solution, under reducing conditions using either cobalt(II) or hydroxylamine sulphate. ..................................................................................................... 4-7 Figure 4.4. Eh-pH diagram for Mn-Co-NH3-H2O system. (a) 10-6 Mn and 1 M NH3 at 250C (b) 10-6 Co and 1 M NH3 at 250C ............................................ 4-9 Figure 4.5. XRD scans of MnOOH/Mn3O4 mixed phase and leach residues using Co(II) and hydroxylamine sulphate as reductants ........................... 4-10 Figure 4.6. XRD scans of MnOOH and leach residues using Co(II) and hydroxylamine sulphate as reductants ...................................................... 4-11 Figure 4.7. XRD scan of original sample, and leach residues after reduction of Mn3O4 in SAC with sulphite, cobalt(II) or hydroxylamine sulphate ........ 4-12

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Figure 4.8. Extent of reduction of Mn3O4 using SO32- or Co2+ as reducing

agents in a SAC (carbonate) or sulphate solution ..................................... 4-12 Figure 4.9. Eh-pH Diagram of Mn-Co-O2-H2O system under standard conditions at 25oC ..................................................................................... 4-15 Figure 4.10. XRD scans of the mixed Mn, Co oxidised hydroxide before and after leaching. ........................................................................................... 4-16 Figure 4.11. Extent of reduction of a mixed Mn, Co oxidised hydroxide using SO3

2- or Co(II) in a SAC solution. .............................................................. 4-16 Figure 4.12. XRD scans of a mixed Mn3O4 and CoOOH precipitate before and after leaching. .................................................................................... 4-18 Figure 5.1. Size analysis of MgO. ............................................................... 5-4 Figure 5.2. SEM Image of MgO. ................................................................. 5-4 Figure 5.3. MgO dissolution at 25°C in SAC solution and water. ................ 5-6 Figure 5.4. XRD scans of 60% MgO/water mixture after 1, 2, 3 & 4 days .. 5-7 Figure 5.5. Change in size distribution of precipitates at 25°C over 240 minutes. ...................................................................................................... 5-9 Figure 5.6. SEM and EDS images of precipitate at 25°C after 5 minutes. 5-11 Figure 5.7. SEM and EDS images of precipitate at 25°C after 30 minutes. ..... .................................................................................................................. 5-11 Figure 5.8. SEM and EDS images of precipitate at 25°C after 240 minutes. ... .................................................................................................................. 5-12 Figure 5.9. HRTEM image of MgO-1-520N ............................................... 5-13 Figure 5.10. Cross section SEM image of MgO after 30 minutes in water at 25°C. ......................................................................................................... 5-13 Figure 5.11. Precipitation of metals with rising pH at 25°C. ...................... 5-15 Figure 5.12. A solubility diagram of metal hydroxides based on KSP at 25°C .................................................................................................................. 5-16 Figure 5.13. Ni/Mg or Co/Mn molar ratios in precipitates .......................... 5-21 Figure 5.14. Effect of Mn(II) in solution on Mn in synthetic MHP .............. 5-25 Figure 5.15. Effect of Mn(II) in solution on ratio of nickel and cobalt incorporation in synthetic MHP. ................................................................ 5-25

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Figure 5.16. Effect of covalent radii on cation softness ............................. 5-28 Figure 5.17. Effect of cation softness on pKSP of hydroxides of M(II) and M(III) ......................................................................................................... 5-28 Figure 5.18. Effect of cation softness on metal assays of dry precipitates of groups 1, 2 and 4 ...................................................................................... 5-29 Figure 5.19. Effect of different metal ion compositions on Ni/Mg molar ratio in dry precipitates in Groups 1, 2 and 4 ........................................................ 5-30 Figure 5.20. Effect of initial Mn(II) concentration on Ni/Mg molar ratio in dry precipitates in Group 3 .............................................................................. 5-31 Figure 5.21. Effect of initial Mn(II) concentration on Ni/Mg molar ratio in dry precipitates in Group 5 .............................................................................. 5-32 Figure 5.22. Size distribution of MgO. ....................................................... 5-33 Figure 5.23. Size distribution of MHP’s, A-H – 6 weeks – cumulative percent passing. .................................................................................................... 5-33 Figure 5.24. Size distribution of MHP’s, A, B, I-N – 6 weeks – cumulative percent passing. ....................................................................................... 5-33 Figure 5.25. Size distribution of MHP’s, A-H – 6 weeks – percent passing. ..... .................................................................................................................. 5-34 Figure 5.26. Size distribution of MHP’s, A, B, I-N – 6 weeks – percent passing. .................................................................................................... 5-34 Figure 5.27. Size distribution of precipitates O – AA over time. ................ 5-35 Figure 5.28. Photo of Ni, Co, Mn precipitate after 2 days (left) and a year (right), precipitate was in a sealed plastic jar. ........................................... 5-36 Figure 5.29. Percent passing, precipitates O - AA – week 1. .................... 5-37 Figure 5.30. Percent passing over time – precipitate O. ........................... 5-37 Figure 5.31. Percent solids of precipitates A – N over time. ..................... 5-39 Figure 5.32. Percent solids of precipitates O – AE over time. ................... 5-39 Figure 5.33. Extent of oxidation titration results (EO%) over time, precipitates A - N.......................................................................................................... 5-42 Figure 5.34. Unoxidised % of Co(II) over time in precipitates A - N. ......... 5-44

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Figure 5.35. Effect of sulphate ion concentration in initial solution on Unoxidised % of Co(II) over time in precipitates A - N. ............................. 5-44 Figure 5.36. Eh-pH Diagram of Co-Si-O2-H2O system under standard conditions at 25oC. .................................................................................... 5-45 Figure 5.37. Ni/Mg and Co/Mn molar ratio in dry precipitate. .................... 5-46 Figure 5.38. XRD scans of precipitate A (Ni, Co, Mg) over 9 weeks. ........ 5-48 Figure 5.39. XRD scans of precipitate B (Ni, Co, Mg, Mn) over 9 weeks. . 5-48 Figure 5.40. XRD scans of precipitate C (Ni, Co, Mg, Mn, Al) over 9 weeks. .................................................................................................................. 5-49 Figure 5.41. Percentage of MgO in precipitates (rough calculation: height of MgO peak at 43° divided by total height of MgO and metal hydroxide peaks at 43° and 38°, respectively). .................................................................... 5-50 Figure 5.42. Hydrotalcite structures (a) general formula and structure, (b) Mg6Al2(CO3)(OH)16.4H2O, and (c) other structures with trivalent cations similar to hydrotalcite. ............................................................................... 5-52 Figure 5.43. Ni/Mg hydroxide peaks at 38° of precipitate A at times 16, 25, 36, 63 and 84 days. .................................................................................. 5-54 Figure 5.44. Ni/Mg and Co/Mn molar ratio in dry precipitates-S and AB-AE .... .................................................................................................................. 5-55 Figure 5.45. Percentage of MgO in precipitates O – S (rough calculation based on peak heights). ............................................................................ 5-57 Figure 5.46. Percentage of MgO in precipitates AB – AE (rough calculation based on peak heights). ............................................................................ 5-57 Figure 5.47. XRD scans of a mixed Ni-Mg(OH)2 precipitate immediately after precipitation and after ageing for approximately a year. ........................... 5-59 Figure 5.48. XRD scans of a mixture of Ni(OH)2 and Mg(OH)2 after precipitation and after ageing for approximately a year. ........................... 5-59 Figure 5.49. XRD scans after oven ageing - batch 1, 12 weeks………….5-61 Figure 5.50. XRD scans after oven ageing, batch 2, introduction of anions (SO4

2-, CO32-, Cl-), 12 weeks ageing. ........................................................ 5-62

Figure 5.51. XRD scans after oven ageing, batch 3, 12 weeks ageing with 2 g/L SO4

2- (from metal sulphate) ............................................................. 5-62

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Figure 5.52. XRD scans after oven ageing, batch 3, 12 weeks of ageing with 5 g/L CaCO3. ............................................................................................ 5-63 Figure 5.53. XRD scans after oven ageing, batch 3, 12 weeks of ageing with 15 g/L NaCl. .............................................................................................. 5-63 Figure 5.54. XRD scans of 12 precipitates, batch 4. ................................. 5-65 Figure 5.55. XRD scan of Ni precipitate. ................................................... 5-66 Figure 5.56. XRD scans of Ni/Co and Ni/Mn precipitates. ........................ 5-67 Figure 5.57. XRD scans of Ni/Fe and Ni/Al precipitates. ........................... 5-68 Figure 5.58. XRD scans of Ni/Ca, Ni/Cr, Ni/Si and Ni/Zn precipitates....... 5-69 Figure 5.59. XRD scans of Ni/Cu precipitate. ........................................... 5-69 Figure 5.60. XRD scan of a Ni/Mn precipitate. .......................................... 5-71 Figure 5.61. Back scattered electron image of precipitate P – week 1. .... 5-73 Figure 5.62. Back scattered electron image of precipitate P – week 3. .... 5-74 Figure 5.63. Back scattered electron image of precipitate P – week 12. .. 5-74 Figure 5.64. Elemental mapping of precipitate P – week 1. ...................... 5-75 Figure 6.1. Nickel leaching results in Modified Standard Predictor Test in SAC over 12 weeks– precipitates A – D. .................................................... 6-3 Figure 6.2. Nickel leaching results in Modified Reductive Predictor Test in SAC with hydroxylamine sulphate over 12 weeks– precipitates A – D. ...... 6-4 Figure 6.3. Effect of Mg% on Ni/Mg molar ratio and Ni% in precipitate (data from Table 6.4) ........................................................................................... 6-9 Figure 6.4. Effect of Mg, Co and Mn content in precipitate on Ni leaching in SPT, RPT and RSPT ................................................................................ 6-10 Figure 6.5. Comparison of Ni and Co leach results (% and molar ratio) in SPT and RPT. ........................................................................................... 6-18 Figure 6.6. Ni-Co Correlations based on leaching results of precipitates A-AE in STT, RPT and RST ............................................................................... 6-20 Figure 6.7. Effect of metal ions in SPT of Group 4 precipitates on (a) Ni/Mg molar ratio, (b) nickel leaching, and (c) cobalt leaching. ........................... 6-22

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Figure 6.8. Effect of metal ions in RPT of Group 4 precipitates on (a) nickel leaching, and (b) cobalt leaching. ............................................................. 6-23 Figure 6.9. Effect of metal ions in RSPT of Group 4 precipitates on (a) nickel leaching, and (b) cobalt leaching. ............................................................. 6-24 Figure 6.10. XRD scans of standard predictor test residues A – D after 6 and 12 weeks (37 and 85 days) ageing. .......................................................... 6-27 Figure 6.11. XRD scans of reductive predictor test residues A - D after 6 and 12 weeks ageing. ...................................................................................... 6-28 Figure 6.12. XRD scans of reductive predictor leach residues – 12 weeks – T, U, V, W. ................................................................................................ 6-28 Figure 6.13. XRD scans of reductive soak predictor test residues after 12 weeks ageing. ........................................................................................... 6-29 Figure 6.14. XRD scans of precipitates MHP1-MHP7............................... 6-29 Figure 6.15. XRD scans of standard predictor leach test residues of MHP1-MHP7. ....................................................................................................... 6-30 Figure 6.16. Standard predictor leach test results - effect of drying for 5 and 20 hours at 50°C, and % solids on nickel recovery. .................................. 6-32 Figure 6.17. Microscope picture of Ni/Mg precipitate. ............................... 6-33 Figure 6.18. XRD scans of Ni/Mg precipitate of 56% solids and 68% and 95% solids obtained after drying for 5 and 20 hours at 50°C. ................... 6-34 Figure 6.19. Analysis of XRD peak at 38° of Ni/Mg precipitate of different % solids. ........................................................................................................ 6-35 Figure 6.20. XRD scans of Ni/Co/Mg/Al precipitate of 45% solids 73% and 81% solids obtained after drying for 5 and 20 hours at 50°C. ................... 6-36 Figure 6.21. XRD scans of Ni/Co/Mg/Al leach residues. ........................... 6-36 Figure 6.22. XRD scans of Ni/Co/Mg/Fe precipitate of 42% solids and 52% and 97% solids obtained after drying for 5 and 20 hours at 50°C. ............ 6-38 Figure 6.23. XRD scans of Ni/Co/Mg/Fe leach residues ........................... 6-38 Figure 6.24. Standard predictor leach test results showing the effect of drying on nickel recovery from aged precipitates. ................................................ 6-39 Figure 6.25. Reductive predictor leach test results showing the effect of drying on nickel recovery from aged precipitates. ..................................... 6-41

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Figure 6.26. TGA plots for Ni/Mg, Ni/Mg/Co, Ni/Mg/Al and Ni/Mg/Fe precipitates after 6 weeks ageing. ............................................................ 6-42 Figure 6.27. XRD scans of Ni, Mg precipitate after heating at 200, 450 and 1000°C. ..................................................................................................... 6-42 Figure 6.28. Slope (Wt %/°C) of TGA plot for Ni/Mg, Ni/Mg/Co, Ni/Mg/Al and Ni/Mg/Fe precipitates. ............................................................................... 6-43 Figure 6.29. Nickel recovery from precipitates after drying at 200°C. ....... 6-44 Figure 6.30. XRD scans of precipitates dried at 200°C. ............................ 6-45 Figure 6.31. Ratio of BET surface area:laser sizer surface area vs. time of leaching. ................................................................................................... 6-49 Figure 6.32. XRD scans of nickel magnesium precipitates of varying crystallinity. ............................................................................................... 6-50 Figure 6.33. Nickel recovery from precipitates over a 20 minute period. .. 6-51 Figure 6.34. Leaching of Ni/Mg precipitates NiMg1-NiMg5: (a) effect of initial Ni(II) concentration on initial rates, (b) testing of a shrinking sphere model, (c) testing of a shrinking core model ......................................................... 6-52 Figure 6.35. Nickel leaching from precipitate – influence of particle size at 20 g/L solid/liquid ratio. ............................................................................. 6-53 Figure 6.36. Applicability of a shrinking core model for Ni leaching from Ni-Mg hydroxide precipitates of different particle sizes: (a) 25-38 μm, (b) 38-53 μm, (c) 53-75 μm, (d) plot of apparent rate constant as a function of 1/r2. ........................................................................................................... 6-54 Figure 6.37. Effect of Ni/Mg ratio on nickel recovery over time. ................ 6-55 Figure 6.38. Effect of Ni/Mg ratio in Ni-Mg-hydroxide precipitate on Ni leaching kinetics: (a) Log-Log plot of initial rates as a function of Ni/Mg ratio; (b) Shrinking sphere model; (c) Shrinking core kinetic model ................... 6-57 Figure 6.39. XRD scans of cobalt precipitates .......................................... 6-59 Figure 6.40. Cobalt leaching from unoxidised and oxidised cobalt hydroxide precipitates in a SAC solution. .................................................................. 6-60 Figure 6.41. Cobalt leaching from unoxidised and oxidised cobalt hydroxide precipitates in a SAC solution. .................................................................. 6-60 Figure 6.42. Applicability of shrinking core kinetic model for Co(II) and Ni(II) leaching in SAC solutions: (a) from precipitate of low Co(III), (b) from NiMg5. .................................................................................................................. 6-61

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Figure 6.43. Nickel leach results for elevated temperature precipitates at 20 g/L in a SAC solution. .......................................................................... 6-63 Figure 6.44. Effect of metal ions on initial rates and final Ni leaching after 60 minutes ..................................................................................................... 6-64 Figure 6.45. Testing the applicability of shrinking sphere or core kinetic models for nickel hydroxide precipitates containing Si or Cr. .................... 6-67 Figure 6.46. Testing the applicability of a shrinking core kinetic model for nickel hydroxide precipitates containing other metal ions. ........................ 6-69 Figure 6.47. Effect of metal ions on the apparent rate constants and nickel leaching in SAC solutions ......................................................................... 6-69 Figure 7.1. Size distribution of RNO MHP samples. ................................... 7-6 Figure 7.2. Size distribution of RNO MHP collected June 2008. ................. 7-6 Figure 7.3. XRD scans of MHP Samples .................................................... 7-8 Figure 7.4. XRD scan of RNO MHP collected June 2008 – 1 week. ........... 7-8 Figure 7.5. Neutron Diffraction pattern of RNO MHP – 1 week. ................ 7-10 Figure 7.6. XRD pattern of Preboil Solids ............................................... 7-11 Figure 7.7. Back scatter electron SEM image of precipitate 1A (MgO addition point). ........................................................................................................ 7-12 Figure 7.8. SEM and EDS images of precipitate 1A (MgO addition point) ....... ................................................................................................................. .7-13 Figure 7.9. SEM and EDS images of precipitate 2A (outside 1st Tank). .... 7-14 Figure 7.10. SEM and EDS images of precipitate 3A (2nd tank). ............... 7-14 Figure 7.11. SEM and EDS images of precipitate 4A (3rd tank). ............... 7-15 Figure 7.12. XPS scan of RNO MHP June 2008, Mg Kα1 source, Mn 2p doublet. ..................................................................................................... 7-16 Figure 7.13. XPS scan of RNO MHP June 2008, Mg Kα1 source, Co 2p doublet. ..................................................................................................... 7-17 Figure 7.14. Laser size analysis of Ni/Co/Mn/Mg precipitate. ................... 7-18 Figure 7.15. XPS scans of Ni/Co/Mn/Mg precipitate, Al Kα1 source, Co 2p doublet. ..................................................................................................... 7-19

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Figure 7.16. XPS scans of Ni/Co/Mn/Mg precipitate, Al Kα1 source, Mn 2p doublet. ..................................................................................................... 7-19 Figure 7.17. XRD scans of RNO MHP over time – 57, 81 & 100% solids. 7-21 Figure 7.18. SEM and EDS images of RNO MHP after 4 days – particles embedded in resin. ................................................................................... 7-22 Figure 7.19. Effect of S/L ratio on nickel leaching from RNO-MHP in SAC solutions. ................................................................................................... 7-25 Figure 7.20. Effect of temperature on nickel leaching from RNO- MHP in SAC solutions ........................................................................................... 7-25 Figure 7.21. Effect of agitation on nickel leaching from RNO-MHP in SAC solutions .................................................................................................... 7-26 Figure 7.22. Effect of particle size on nickel leaching from RNO MHP, 10 g/L. .................................................................................................................. 7-26 Figure 7.23. XRD scans of RNO-MHP of different size fractions. ............. 7-27 Figure 7.24. Arrhenius plot for Ni(II) dissolution from RNO-MHP in SAC solution (500 rpm, 38-53 μm, 10 or 20 g/L solids) ..................................... 7-29 Figure 7.25. Effect of particle size on initial rates of Ni(II) dissolution from RNO-MHP and Ni,Mg(OH)2. ..................................................................... 7-30 Figure 7.26. Comparison of kinetic models for Ni(II) dissolution from (a) Ni,Mg(OH)2 , and (b) MHP-RNO in SAC solution at 25oC, 500 rpm, 20 g/L solids and particle size range of 38-53 μm. .............................................. 7-30 Figure 7.27. Comparison of metal leaching from different commercial MHP’s under different leach conditions ................................................................ 7-33 Figure 7.28. Effect of metal ion composition in Cawse, PS-44 and S-22 samples on Ni leaching in SAC solution under standard conditions. ........ 7-35 Figure 7.29. Effect of metal ion composition in Cawse, PS-44 and S-22 samples on Co leaching in SAC solution under standard conditions. ....... 7-36 Figure 7.30. Effect of metal composition in Yabulu-Preboil, RNO-Pilot and RNO-June samples on Ni leaching in SAC solution under standard conditions. ................................................................................................. 7-37 Figure 7.31. Effect of metal composition in Yabulu-Preboil, RNO-Pilot and RNO-June samples on Co leaching in SAC solution under standard conditions. ................................................................................................. 7-38 Figure 7.32. XRD scans of Preboil Solids and leach residues .................. 7-39

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Figure 7.33. XRD scans of RNO Pilot MHP and leach residue. ................ 7-41 Figure 7.34. XRD scans of Cawse MHP and leach residue ...................... 7-44 Figure 7.35. XRD scans of PS-44 leach residues ..................................... 7-47 Figure 7.36. XRD scans of SS-22 leach residues ..................................... 7-48 Figure 7.37. XRD scans of standard and reductive predictor leach test residues after 12 weeks (85 days) ageing. ............................................... 7-52 Figure 8.1. Sulfide solubility diagram at 25°C ............................................. 8-2 Figure 8.2. Sulfide solubility diagram at 45°C. ............................................ 8-3 Figure 8.3. XRD scans of CoNiS samples – effect of cobalt oxidation state at 25°C. ........................................................................................................... 8-9 Figure 8.4. SEM image of unseeded CoNiS produced at 25°C with a divalent oxidation state and sulphidation ratio of 2.2:1. .......................................... 8-10 Figure 8.5. ORP (vs. Ag/AgCl) of sodium sulphide with 1 L/min oxygen in 1 L of SAC at 25°C. ........................................................................................ 8-12 Figure 8.6. Potential-pH diagrams of Ni-NH3-S-H2O system..................... 8-14 Figure 8.7. CoS and NiS dissolution in SAC at 25°C with 1 L/min N2. ...... 8-16 Figure 8.8. Effect of pH on the speciation of (a) CO2 and SO2, (b) NH3 and S2-. ............................................................................................................ 8-16 Figure 8.9. Effect of anions on nickel(II) dissolution from Ni,Mg(OH)2 in 90 g/L ammonia with 1.47 mol/L of the anion solutions at 25°C. .............. 8-18 Figure 8.10. NiS dissolution in SAC at 25°C with 1 L/min N2 or air. .......... 8-20 Figure 8.11. CoS dissolution in SAC at 25°C with 1 L/min N2 or air, and sulphite with N2. ........................................................................................ 8-20 Figure 8.12. Ni and Co dissolution from 50-50 CoNiS in SAC solutions at 25°C with 1 L/Min N2. ................................................................................ 8-22 Figure 8.13. Fraction of Ni and Co dissolution in SAC at 25°C from different sulphides with 1 L/Min N2 and air .............................................................. 8-23 Figure 8.14. Cobalt dissolution from RNO-MHP in SAC solution in an open vessel, or with 500 mL/min N2 or air. ........................................................ 8-23

xxvi

Figure 8.15. (a) Co/Ni ratio in solution, and (b) Co/Ni ratio of fraction dissolved from CoNiS precipitates produced at 25°C with varying sulphiding ratios in SAC solution under N2, in the absence of MnOOH. .................... 8-25 Figure 8.16. Reductive leaching of MnOOH: effect of temperature, cobalt oxidation state and sulphidation ratio. ....................................................... 8-29 Figure 8.17. Reductive leaching of MnOOH: effect of Co/S ratio. ............. 8-30 Figure 8.18. Eh-pH diagrams for Ni(II) and Co(II)/(IIII) in ammonia solutions at 25oC and 6 M NH3, 0.1 M Ni(II) and 0.01 M Co(II)/(IIII) ......................... 8-33 Figure 8.19. Reductive leaching of MnOOH: effect of drying. ................... 8-34 Figure 9.1. Yabulu refinery YEP flowsheet ................................................. 9-4 Figure 9.2. MHP reslurry ............................................................................. 9-5 Figure 9.3. MHP primary leach ................................................................... 9-5 Figure 9.4. CoNiS precipitation and thickening ........................................... 9-6 Figure 9.5. MHP secondary leach and leach residue.................................. 9-6 Figure 9.6. Plant Survey – ORP. Conducted over 3 weeks, blue: week 1, red: week 2 and green: week 3. ......................................................................... 9-7 Figure 9.7. Eh-pH diagram for Co-ammonia-carbonate system at similar solution concentrations to YEP at 30°C. ..................................................... 9-8 Figure 9.8. XRD scans of MHP’s and preboil solids.................................. 9-12 Figure 9.9. Comparison of XRD scans of preboil solids collected in May 08 and June 06 .............................................................................................. 9-14 Figure 9.10. XRD scans of plant solid samples ........................................ 9-15 Figure 9.11. XRD scans of secondary leach slurries ................................ 9-16 Figure 9.12. XRD scan of CoNiS .............................................................. 9-17 Figure 9.13. XRD scans of thickener residues .......................................... 9-17 Figure 9.14. HPLC – secondary leach tank 3345-1913, sampled 19/5 ..... 9-19 Figure 9.15. HPLC – cobalt ammine species concentrations .................... 9-20 Figure 9.16. Cobalt(III) concentration determined by solvent extraction and ICP. Error bars represent difference in concentration determined by laboratory method and HPLC. .................................................................. 9-22

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Figure 9.17. Total cobalt(III) concentration determined by HPLC in batch test and SPT liquors ........................................................................................ 9-28 Figure 9.18. Cobalt(II)/cobalt(III) concentration ratio determined by SX and ICP of batch leach test liquors .................................................................. 9-28 Figure 9.19. Distribution of cobalt(III) speciation in batch leach liquors (after 1, 2,3 or 4 h) based on HPLC analysis ..................................................... 9-31 Figure 9.20. Distribution of cobalt(III) speciation in standard predictor leach test of MHP1-4 with batch leach liquors (after 0.75 h). ............................. 9-31

xxviii

LIST OF TABLES Table 2.1. Hydrotalcite-like structures ...................................................... 2-30 Table 2.2. Stability constants (Kn) of metal ammine complexes. ............. 2.34 Table 3.1. List of reagents. ......................................................................... 3-2 Table 3.2. List of industry samples ............................................................. 3-3 Table 3.3. Solution compositions prior to precipitation of MHP, g/L. .......... 3-7 Table 3.4. Solution composition for precipitation of samples similar to RNO-MHP, g/L. .................................................................................................... 3-8 Table 3.5. Solution compositions for precipitation of samples for drying, g/L. . .................................................................................................................... 3-8 Table 3.6. Solution compositions for varying cobalt content, g/L. ............ 3-10 Table 3.7. Solution composition for varying Co, Mn, Al and Cr contents, g/L. .................................................................................................................. 3-11 Table 3.8. Solution volume and nickel composition for varying crystallinity of Ni,Mg(OH)2 ............................................................................................... 3-12 Table 3.9. Solution compositions for precipitates produced for oven ageing tests in batch 1-2, g/L. .............................................................................. 3-13 Table 3.10. Solution compositions for precipitates for oven ageing tests in batch 2, g/L. .............................................................................................. 3-14 Table 3.11. Solution compositions for precipitation at elevated temperature (80°C), g/L. ............................................................................................... 3-15 Table 3.12. CoNiS precipitation conditions. ............................................. 3-17 Table 3.13. RNO kinetic leach test conditions. ........................................ 3-26 Table 3.14. AAS conditions for analysis. .................................................. 3-30 Table 4.1. Equilibrium constants for the reactions of manganese oxides...4-8 Table 5.1. Assay of Queensland Magnesia’s MgO (Emag 45). .................. 5-3 Table 5.2. Particle size (P80 ) of precipitates at 25 and 40°C over 4 hours . 5-9 Table 5.3. Composition of precipitates of Groups 1-5 (dry basis) ............. 5-19 Table 5.4. Composition of precipitates of Group 6 (dry basis). ................. 5-20

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Table 5.5. Assay results of cobalt and manganese rich precipitates. ....... 5-21 Table 5.6. Ratio of % metal in MHP over % metal in solution. .................. 5-24 Table 5.7. Atomic radii of selected metals, pm ......................................... 5-26 Table 5.8. Effect of Eh on Mn and Co species .......................................... 5-40 Table 5.9. Percentage of possible oxidised metals. .................................. 5-43 Table 5.10. Extent of Oxidation ................................................................. 5-47 Table 5.11. Assay results for precipitates O–R and AB-AE, %. ................ 5-55 Table 6.1. Summary of predictor leach test results – standard, reductive, soak ............................................................................................................ 6-6 Table 6.2. Confidence intervals of leach results. ........................................ 6-7 Table 6.3. Soak test – leach residue analysis. ............................................ 6-8 Table 6.4. Effect of manganese and cobalt on leach results from SPT, RPT and RST ...................................................................................................... 6-9 Table 6.5. Effect of Co in the absence or presence of Mn on Ni and Co leaching in MSPT and MRPT .................................................................... 6-11 Table 6.6. Modified standard and reductive predictor leach test results - 95 % confidence interval, %. .............................................................................. 6-12 Table 6.7. Effect of increasing Co, Mn, Al and Cr on composition of precipitates. .............................................................................................. 6-14 Table 6.8. Effect of increasing Co, Mn, Al and Cr on leaching of metals .. 6-14 Table 6.9. Mathematical expressions for heterogeneous kinetic models .. 6-46 Table 6.10. Effect of Ni/Mg ratio on initial rates of leaching. ..................... 6-50 Table 6.11. Chemical analysis of precipitates formed at elevated temperature, %. ........................................................................................ 6-62 Table 7.1. Age of Precipitate Samples. ....................................................... 7-2 Table 7.2. BHP Billiton Chemical Analysis of Aged MHP Samples ............. 7-4 Table 7.3. Assay of RNO MHP Collected in June 2008. ............................. 7-5 Table 7.4. P80 of Ravensthorpe MHP’s. ...................................................... 7-6

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Table 7.5. Effect of leach conditions on the initial leach rates of June 2008 RNO-MHP ................................................................................................. 7-23 Table 7.6. Assay results for size fractions of RNO-MHP, mass %. ........... 7-26 Table 7.7. Predictor leach test results of commercial precipitates. ........... 7-32 Table 7.8. Comparison of assays of different types of RNO samples and Yabulu Preboil sample .............................................................................. 7-37 Table 7.9. Predictor leach test results from Preboil Solids. ....................... 7-39 Table 7.10. Predictor leach test results from RNO-MHP over time. .......... 7-41 Table 7.11. Predictor leach test results from Cawse MHP over time. ...... 7-43 Table 7.12. Predictor leach test results for EN Pilot Plant MHP. ............... 7-46 Table 7.13. Standard predictor leach test results of RNO-MHP June 2008 - % leached and 95 % confidence interval. ................................................. 7-49 Table 7.14. Reductive predictor test results of RNO-MHP June 2008 – % leached and 95 % confidence interval. ................................................. 7-49 Table 7.15. Reductive soak predictor test results of RNO-MHP June 2008 – % leached and 95 % confidence interval. ................................................. 7-49 Table 7.16. Modified standard predictor test results of RNO-MHP June 2008 – % leached and 95 % confidence interval. .............................................. 7-50 Table 7.17. Modified reductive predictor test results of RNO-MHP June 2008 – % leached and 95 % confidence interval. .............................................. 7-51 Table 8.1. Ksp values at 45°C…………………………………………………..8-3 Table 8.2. Preparation conditions and composition of CoNiS ..................... 8-4 Table 8.3. Molar ratios and formula of CoNiS ............................................. 8-4 Table 8.4. Precipitation Reactions for Co-Ni-S ........................................... 8-5 Table 8.5. Possible reactions of sulphides with Mn(III) and Co(III) oxides 8-11 Table 8.6. Non-Oxidative or Oxidative dissolution of NiS and CoS. .......... 8-17 Table 8.7. Metal ion concentrations in SAC during leaching of sulphides . 8-22 Table 8.8. Oxidation half cell reactions of nickel sulphides ....................... 8-27

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Table 8.9. ORP and extent of leaching of MnOOH with CoNiS ................ 8-29 Table 8.10. Reduction reactions of Mn(III) and Co(III) oxides ................... 8-32 Table 9.1. Thiosulphate concentrations in plant liquors. ............................. 9-9 Table 9.2. Nickel and cobalt concentrations in plant liquors. .................... 9-11 Table 9.3. Ammonia and carbonate concentrations in plant liquors. ......... 9-11 Table 9.4. Composition of Preboil Solids from June 06 and May 08 ......... 9-13 Table 9.5. HPLC peaks in plant liquors. .................................................... 9-23 Table 9.6. Composition of MHP used in batch tests ................................. 9-25 Table 9.7. Percentage composition of Co(II) in batch leach liquors based on solvent extraction ...................................................................................... 9-25 Table 9.8. Composition of Co(III) in batch test leach Liquors based on HPLC .................................................................................................................. 9-27 Table 9.9. Speciation of Co(III) in Standard Predictor Leach Tests based on HPLC. ....................................................................................................... 9-27 Table 9.10. Peaks present in HPLC plots of plant liquors. ........................ 9-30 Table 9.11. Peaks present in HPLC plots of secondary leach liquors of MHP. .................................................................................................................. 9-35