SEPARATION OF PYRITE FROM ARSENOPYRITE BY FLOTATION by AYHAN ALI SIRKECI, B.Sc ...

177 Pages·2013·3.81 MB·English

SEPARATION OF PYRITE FROM ARSENOPYRITE BY FLOTATION
by
AYHAN ALI SIRKECI, B.Sc.
A thesis submitted for the degree of Doctor of Philosophy of the
University of London
and for the
Diploma of Imperial College of Science, Technology and Medicine
Department of Mineral Resources Engineering
Royal School of Mines, Imperial College
University of London
December 1992
Abstract
This thesis reports investigations into the flotation separation of pyrite from
arsenopyrite using xanthates and the new collectors Fl, S7 and F2B developed by
Dow Chemical Company. The Dow surfactants were classified as chelating
collectors by the manufacturer. For this purpose Hallimond tube, bench and
column flotation tests were run in order to assess the flotation behaviour of these
minerals. In addition to these experiments other tests performed were adsorption
characteristics of Fl on pyrite and arsenopyrite, the effect of Fl on
electrophoretic mobility and surface tension of Fl solutions.
The effect of pH on the recovery of pyrite and arsenopyrite was studied for all
collectors with the Hallimond tube. pH values ranging from 2 to 12 were tested
at constant collector concentrations. At the optimum pH values further
experiments were carried out under varying collector concentrations. The results
obtained for five different collectors showed that selectivity was rather poor at all
conditions except for Fl. A successful separation was seen to be possible
employing Fl and by floating pyrite. This was proven by using a mixture of
equal amounts of pyrite and arsenopyrite and selectively floating pyrite.
Bench and column flotation tests were carried out in order to confirm the results
obtained with the Hallimond tube. A Denver flotation cell was used and a
column cell was constructed. In these tests Fl was used as a collector and in
some cases amyl xanthate was blended. The effect of collector concentration was
monitored and other parameters were adjusted for an optimum separation.
Observations showed that a selective flotation of pyrite from arsenopyrite could
be possible.
Adsorption characteristics of Fl on pyrite and arsenopyrite were studied as a
function of collector concentration, pH and time. Though there was not a direct
correlation between the amount of Fl adsorbed and the success of flotation, in
general pyrite was found to adsorb more Fl than arsenopyrite. Electrophoretic
mobility of pyrite and arsenopyrite against pH and collector concentration was
measured. It was observed that Fl did not have a substantial effect on the
electrophoretic mobility of these minerals. The measured pK value of Fl
indicated that most of the collector in solution was in molecular form above pH
9.2.
Acknowledgements
I would like to take this opportunity to thank;
My supervisors Dr. R.J. Gochin and Dr. A.J. Monhemius for their advice and
guidance, Prof. A.R. Burkin for his kind suggestions.
My thanks are also due to:
Past and present members of the hydrometallurgy group; Elia, Themis, Heidi,
Veronica, Luis, Peter, Mike Haddon, Roberto and Steve for their sincere
friendship, encourage, understanding and support throughout the years I shared
with them otherwise, I believe, would be unbearable. And also Timur Ustaomer
for his true and invaluable friendship.
Mr. J. Burgess, Mr. V. Harris and Mr. Colin Richardson for their technical
assistance and help.
The National Educational Ministry of Turkey for their financial support.
The Dow Chemical Company (Germany), and Mr. Simon Isherwood for
supplying the collectors Fl, S7 and F2B.
The Cyanamid Company (The Netherlands) for supplying the xanthates.
The Spectratech Company and especially Mr. Alan Strawn for conducting FTIR
analyses.
And last but certainly not the least my sister who always supported, encouraged
and loved me all my life with a care and affection of a mother; my gratitude can
not likely be expressed in any language in the world.
I can not possibly finish my words without stating my deep respect, love and
agony that I feel about my mother, who passed away almost a year ago. She
sacrificed herself for her beloved children just to see them happy, you will
always live in my heart. Rest in peace.
4
Dedication
To my mother, father and sister.
Table of Contents
Abstract 2
Acknowledgements 3
Dedication 4
Table of Contents 5
Table of Figures 8
Contents of Tables 12
CHAPTER 1 13
INTRODUCTION 13
Introduction 14
CHAPTER II 21
LITERATURE SURVEY 21
2.1. Review of Surface Characteristics of Sulphides 22
2.1.1. Introduction 22
2.1.2. Xanthate-Sulphide Mineral Interactions 28
2.1.3. Oxidation Reactions on the Surface of Pyrite 32
2.1.4. Oxidation Reactions on Arsenopyrite Surfaces 36
2.1.5. Effect of Semiconductivity on Surface Reactions 38
2.2. Review of Flotation Studies Carried Out on Pyrite and
Arsenopyrite 40
2.3. Collectors 46
2.3.1. Introduction 46
2.3.2. Behaviour of Xanthates in Different Solutions 48
2.3.3. Complexes and Chelating Collectors 49
2.3.4. New Collectors Used in This Study 52
2.4. Column Flotation 54
CHAPTER III 59
METHODS AND MATERIALS 59
3.1. Description of Research Techniques 60
3.1.1. Hallimond Tube Tests 60
3.1.2. Bench Flotation 61
3.1.3. Column Flotation 62
3.1.4. Adsorption Tests 64
3.1.5. Electrophoretic Mobility Measurements 64
3.2. Description of Materials Used and Preparation 65
3.3. Description of Analytical Techniques 67
3.4. FTIR Studies 68
3.5. Surface Tension Measurements 69
CHAPTER IV 75
PYRITE FLOTATION 75
4.1. Hallimond Tube Flotation Tests 76
4.1.1. Flotation with Xanthates 76
4.1.2. Flotation with S7 78
4.1.3. Flotation with F2B 80
4.1.4. Flotation with F1 81
4.2. Adsorption 84
4.2.1. The Effect of Time on Adsorption 84
4.2.2. Adsorption Isotherms 86
4.2.3. The Effect of pH on Adsorption 88
4.3. Desorption 89
4.4. Electrophoretic Mobility 90
4.4.1. Electrophoretic Mobility Against pH 91
4.4.2. Electrophoretic Mobility with Respect to pH at
Constant F1 Concentration 92
4.4.3. The Effect of Increasing F1 Concentration on
Electrophoretic Mobility at Constant pH 92
4.4.4. The Effect of Dodecylamine and F1 on the
Electrophoretic Mobility of Quartz at Constant pH 94
4.4.5. The Effect of Dodecylamine Concentration on the
Electrophoretic Mobility of Pyrite at Constant pH 96
CHAPTER V 97
ARSENOPYRITE FLOTATION 97
5.1. Hallimond Tube Flotation Tests 98
5.1.1. Flotation with Xanthates 98
5.1.2. Flotation with S7 and F2B 98
5.1.3. Flotation with F1 100
5.2. Adsorption 102
5.2.1. Time Dependency of F1 Adsorption 102
5.2.2. Adsorption Against F1 Concentration 102
5.2.3. The Effect of pH on the Adsorption 105
5.3. Desorption 105
5.4. Electrophoretic Mobility 106
5.4.1. Electrophoretic Mobility Against pH 107
5.4.2. The Effect of F1 Concentration on the Electrophoretic
Mobility 107
CHAPTER VI 109
SEPARATION TESTS 109
6.1. Introduction 110
6.2. Hallimond Tube Flotation 110
6.3. Bench Flotation 114
6.4. Column Flotation 120
6.4.1. Introduction 120
6.4.2. Experimental Results 121
CHAPTER VII 130
DISCUSSION, CONCLUSIONS AND FUTURE WORK 130
7.1. Discussion 131
7.1.1. Introduction 131
7.1.2. Pyrite 132
7.1.3. Arsenopyrite 144
7.1.4. Separation Tests 149
7.1.4.1. Hallimond Tube Flotation 149
7.1.4.2. Bench Flotation 150
7.1.4.3. Column Flotation 151
7.3. Conclusions 154
7.4. Future Work 156
Appendix 1 157
Appendix 11 160
REFERENCES 163
Table of Figures
Figure 1.1. The minerals formed in the Fe-As-S system 16
Figure 2.1. Distribution of charges across a solid surface and solution
according to Helmotz's model of double layer 24
Figure 2.2. The decay of surface potential with respect to distance from
the surface after Gouy and Chapman 25
Figure 2.3. The distribution of potential into the interior of solution
according to Stem's model 26
Figure 2.4. Potential distribution across the double layer after the
modification of the Stem layer 26
Figure 3.1. The schematic diagram of the Hallimond tube used in this
investigation 61
Figure 3.2. The schematic diagram of the column cell used in this study 63
Figure 3.3. The spectra of Fl, and pyrite powders conditioned in F1
solutions of different pH. (a) Fl, (b) pH 5, (c) pH 10, (d) pH
11 70
Figure 3.4. The surface tension of Fl at around pH 5.0-5.5 72
Figure 3.5. Surface tension of Fl and dodecylamine at pH 11 and 10.4
respectively 73
Figure 3.6. Surface tension of Fl and dodecylamine against pH 73
Figure 4.1. Flotation of pyrite with 6.94*10'^ mol/1 ethyl and 4.95*10"^
mol/1 amyl xanthates 77
Figure 4.2. Flotation of pyrite with ethyl and amyl xanthates at pH 4 and
3.5 respectively 77
Figure 4.3. Flotation of pyrite with S7 at 8.4*10"6 mol/1 collector
concentration 79
Figure 4.4. Flotation of pyrite recovery against S7 concentration at pH 3 79
Figure 4.5. Recovery of pyrite with 2 mg/1 F2B concentration 80
Figure 4.6. Recovery of pyrite and quartz using Fl at different pH 82
Figure 4.7. The effect of increasing Fl concentration on the recovery 82
Figure 4.8. The effect of conditioning on the flotation of pyrite at
increasing Fl concentrations 83
Figure 4.9. Adsorption of Fl onto pyrite against time around pH 11.
Initial collector concentration is 5.06*10"^ mol/1 85
Figure 4.10. Adsorption of Fl onto pyrite against time around pH 11.
Initial collector concentration is 2.53*10"^ mol/1 85
Figure 4.11. Adsorption of F1 onto pyrite against time around pH 4.6.
Initial collector concentration 2.53*10"^ mol/1 86
Figure 4.12. Adsorption density on pyrite against final F1 concentration
at two different pH values 87
Figure 4.13. Variation of sulphate concentration in solution with F1 87
Figure 4.14. The effect of pH on the adsorption density of F1 on pyrite 88
Figure 4.15. Desorption ability of F1 off the pyrite surface 89
Figure 4.16. The effect of pH on the electrophoretic mobility of pyrite in
the presence and absence of F1 92
Figure 4.17. The effect of increasing F1 concentration on the
electrophoretic mobility of pyrite at two different pH values 93
Figure 4.18. The effect of swapping pH across the iep on the EM of
pyrite in the presence and absence of F1 94
Figure 4.19. The effect of dodecylamine concentration on the
electrophoretic mobility of quartz in acidic and alkaline
solutions 95
Figure 4.20. The effect of F1 concentration on the electrophoretic
mobility of quartz in acidic and alkaline solutions 95
Figure 4.21. The effect of dodecylamine on the electrophoretic mobility
of pyrite at pH 10 96
Figure 5.1. The flotation of arsenopyrite with 6.94*10"^ mol/1 NaEX and
4.95*10-5 mol/1 KAX 99
Figure 5.2. The effect of increasing NaEX and KAX concentration on
the flotation recovery of arsenopyrite at pH 3.2 and 3.5
respectively 99
Figure 5.3. Flotation recovery of arsenopyrite with 8.4*10"'^ mol/1 S7
and 2 mg/1 F2B 100
Figure 5.4. Flotation of arsenopyrite using 1.01*10-5 mol/1 F1 101
Figure 5.5. The effect of preconditioning and using Ca(0H)2 as pH
regulator on the recovery of arsenopyrite around pH 10 101
Figure 5.6. Time dependency of F1 adsorption onto arsenopyrite at pH
10 103
Figure 5.7, Time dependency of F1 adsorption onto arsenopyrite at pH
11 103
Figure 5.8. Adsorption density of F1 on arsenopyrite against final
concentration 104
Figure 5.9. The arsenic concentration in the solutions with respect to the
initial F1 concentration 104
10
Figure 5.10. The effect of pH on the adsorption density of F1 105
Figure 5.11. F1 desorption off the surface of arsenopyrite on diluting the
solution after adsorption 106
Figure 5.12. The electrophoretic mobility of arsenopyrite against pH 107
Figure 5.13. The effect of increasing F1 concentration on the E.M. of
arsenopyrite in acidic and alkaline solutions 108
Figure 6.1. The arsenopyrite content of the flotation products Ill
Figure 6.2. The arsenopyrite recovery of the flotation products Ill
Figure 6.3. The pyrite content of the flotation products 113
Figure 6.4. The pyrite recovery of the flotation products 113
Figure 6.5. The effect of collector concentration on the sulphide
selectivity 115
Figure 6.6. The effect of using distilled water and grinding pyrite and
arsenopyrite together on selectivity 115
Figure 6.7. The effect of applying a cleaning flotation on the selectivity
for two different samples 116
Figure 6.8. The recovery of pyrite and arsenopyrite against F1
concentration for the concentrate 117
Figure 6.9. The pyrite and arsenopyrite grades in the concentrate against
F1 concentration 118
Figure 6.10. The effect of different treatments on the recovery 118
Figure 6.11. The effect of treatments on the grade of pyrite and
arsenopyrite in the concentrate 119
Figure 6.12. The change in the recovery and grade of pyrite with the gas
and feed rate 121
Figure 6.13. The flotation response of quartz with 5.06*10'^ mol/1 F1 122
Figure 6.14. A typical progress of flotation in the column cell 123
Figure 6.15. The effect of using wash water on the recovery and grade of
pyrite and arsenopyrite 124
Figure 6.16. The effect of negative and positive bias on the grade and
recovery of pyrite and arsenopyrite 125
Figure 6.17. The effect of using arsenopyrite with a high copper content
on the flotation 125
Figure 6.18. The change in the recovery and grade with respect to F1
concentration 126
Figure 6.19. The effect of pH on the recovery of pyrite and arsenopyrite 127
Figure 6.20. The recovery ratio of pyrite and arsenopyrite under the
conditions as in Figure 6.19 127