Processing of Complex Ores. Proceedings of the International Symposium on Processing of Complex Ores, Halifax, August 20–24, 1989

569 Pages·1989·14.726 MB·English

by  G. S. Dobby and S. R. Rao (Eds.)

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ACTA METALLURGICA
CANADIAN METALLURGICAL QUARTERLY
MINERALS ENGINEERING
SCRIPTA METALLURGICA
PROCEEDINGS OF THE INTERNATIONAL SYMPOSIUM ON
PROCESSING OF COMPLEX ORES,
HALIFAX, AUGUST 20-24, 1989
Processing
of Complex Ores
Editors
G.S. Dobby
University of Toronto, Toronto, Ontario
S.R. Rao
McGill University, Montreal, Quebec
Symposium organized by the Mineral Sciences and Engineering Section of
The Metallurgical Society of CIM
28th ANNUAL CONFERENCE OF METALLURGISTS OF CIM
28e CONFΙRENCE ANNUELLE DES MΙTALLURGISTES DE L'ICM
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Copyright © 1989 by The Canadian Institute of Mining and Metallurgy
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Organizing and Editorial Committee
C. Bazin
Brunswick Mining and Smelting Corp.
Bathurst, New Brunswick
R.O. Burt
Tantalum Mining Corporation of Canada Ltd.
Lac du Bonnet, Manitoba
M. Collins
Falconbridge Limited
Falconbridge, Ontario
J.A. Meech
Queen's University
Kingston, Ontario
L.J. Surges
Brunswick Mining and Smelting Corp. Ltd.
Bathurst, New Bruswick
Preface
It has now become a tradition with the Metallurgical Society of The Canadian Institute of Min-
ing and Metallurgy (CIM) to organize several symposia each year as a part of the Annual Con-
ference of Metallurgists held in late August in different centres of Canada. The subject matters
chosen reflect some of the current major interests of mineral and metallurgical industries and
research. The symposia have become international gatherings providing a forum for personal
contacts and discussions between scientists and engineers from different parts of the world.
Two years ago the Minerals Science and Engineering Section of The Metallurgical Society of
CIM decided to hold an international symposium on the processing of complex ores as part of
the 28th annual Conference of Metallurgists in Halifax, Nova Scotia. It was strongly felt that
the subject matter is of world-wide practical concern to process engineers as well as research
scientists, complementing each other in the quest for developing new practical methods for the
processing of a wide variety of complex ores. With the growing demand for metals and materi-
als novel approaches and techniques of processing are constantly being sought for productively
harnessing the complex mineral resources.
Development of new technologies often depend upon the scientific understanding of the com-
plex ore system and the various interactions which the system undergoes. This should be integrated
with the current needs of the industry. Close collaboration between research scientist and engi-
neer is essential for the successful development of new technologies. The present symposium,
to a large extent, reflects this interest. The papers presented have originated from many groups
of research scientists as well as process engineers. The papers on basic research present novel
approaches to the understanding of complex systems of practical interest to the mineral indus-
try. The papers discussing some of the recent advances in the technology of complex ore processing
cover a wide range of techniques. Flotation (including column flotation) and hydrometallurgy
have attracted a good deal of interest. A section of papers is devoted to complex ores of niobium,
tantalum and tin: another describes expert systems which present specific examples of the appli-
cation of computer technology.
We are very pleased at the excellent response to our invitation to this symposium. As the readers
will note, we received papers from most regions of the world where the mineral industry makes
a significant contribution to the national economy and living standards. We hope the symposium
and the papers presented will help in promoting stronger contacts and exchange of ideas between
researchers and engineers in the coming years for the mutual benefit of all interested in the process-
ing of complex ores.
The contribution of the organizing and editorial committee has assured the success of this sym-
posium, and we are greatly indebted to the efforts of these people. We are particularly pleased
by the strong international input to the technical program. Many of the authors have English
as a second language and we appreciate their efforts toward producing well written manuscripts;
slight grammatical errors remain unedited. Finally, we wish to acknowledge the excellent produc-
tion assistance provided by Jeanne Gould (McGill University), Margaret Crook (University of
Toronto) and Perla Gantz and her staff at the CIM Secretariat.
G.S. Dobby and S.R. Rao
June 1, 1989 Co-editors
3
A study of the natural and induced hydrophobicity of
some sulphide minerals by collectorless flotation
X. Wang and E. Forssberg
Division of Mineral Processing, Lulea University of Technology, S-951 87, Lulea, Sweden
ABSTRACT
The native and induced surface hydrophobicity of a number of natural sulfide
minerals were investigated by flotation tests in the absence and presence of
EDTA. The dissolution behaviour of the minerals in EDTA solutions was studied as
a function of pH and EDTA concentration. With the exception of sphalerite, thé
flotation and dissolution of the tested minerals in EDTA solutions depend
strongly on the pH values and EDTA concentration. In general, at a proper EDTA
concentration, low flotation and small amount of released metal species were
observed up to pH 5 and above 10. In the range of pH 6-10, both flotation
recovery and the dissolution of the minerals exhibited a plateau, and the amount
of released metal species increased with increasing EDTA concentration. The
floatability first increases with an increase in EDTA concentration, however, a
further increase in concentration (>10"3M) leads to a significant decrease in
flotation recovery. Zeta-potential measurements show that in the presence of
EDTA, the i.e.p of the sulfide minerals is shifted considerably to lower pH
values. These results are used to discuss the surface hydrophobicity of the
sulfide minerals.
KEYWORDS
Collectorless flotation, sulfides, hydrophobicity, EDTA, dissolution, oxidation.
4 PROCESSING OF COMPLEX ORES
INTRODUCTION
The question as to whether a sulfide mineral surface is naturally hydrophobic is
still open to debate. It was previously believed that apart from minerals like
molybdenite and realgar, pure and clean sulfide minerals are hydrophilic and
non-floatable [Rogers, 1962]. However, a number of recent investigations on the
collectorless flotation of sulfide minerals provoked renewed interest in this
issue. Finkelstein and co-workers [1975] showed that clean sulfides are neither
strongly hydrophobic nor hydrophilic. Trahar and colleagues [1979-1984]
performed a series of experimental studies on the collectorless flotation of
sulfide minerals and found that under only moderate oxidizing conditions, most
sulfide minerals are floatable in the absence of collectors. However, Fuerstenau
and Sabacky [1981] provided experimental evidence that the common base metal
sulfides are all naturally floatable in oxygen-free environments. The reasons
for these discrepancies are complex and are not yet fully understood. However,
one of the main reasons should be the differences in surface state, including
the degree of surface oxidation, surface roughness, surface defect etc. The
surface state of the sulfide minerals used by the various investigators must
have been very different. Note that the surface state of a mineral can be
changed not only by chemicals in flotation pulp, but also by the preparation
conditions (sometimes to a greater extent), as shown by Somasundaran and Lin
[1972]. The work of Oliver and co-workers [1980] and Harris and Richter [1985]
unequivocally demonstrated that surface roughness and surface defects strongly
affect the surface hydrophobicity of minerals. It is therefore critical that the
effect of grinding on the surface properties should also be eliminated if
definite conclusions on the natural hydrophobicity of sulfide surfaces are to be
established. This is, of course, a very formidable task.
In the present paper, the floatability, the surface dissolution behaviour and
zeta-potential of a number of sulfide minerals in EDTA solutions have been
investigated as a function of pH and EDTA concentration. The natural surface
hydrophobicity of the sulfide minerals is studied under conditions where
hydrophilic surface (hydr)oxide species and adsorption of EDTA complexes are
eliminated.
EXPERIMENTAL
Materials
PROCESSING OF COMPLEX ORES 5
High purity natural mineral samples were used in the present investigation.
Sphalerite, pyrite and galena samples were obtained from Wards Science
Establishment Inc., USA, while arsenopyrite and glaucodot were obtained from the
Division of Economic Geology of Lulea University of Technology. Their chemical
compositions are presented in table 1. The mineral samples were first crushed
and quartz particles were removed by hand. Grinding was carried out in a micro-
centrifugal ball mill where both mill and balls are made of zirconium oxide.
Fractions, Ί20-75μπι and 75-40 μπι, were used for flotation tests. Particles of
fraction -40 μιη were further ground using a mortar and pestle to -20 μπι and were
used for zeta-potential measurements.
NaCIO , HC10 , NaOH and disodium ethylenediamine tetraacetic acid (Na H EDTA)
were of analytical grade. Methylisobutylcarbinol (MIBC) having a purity of 99%
(Merck) was used as frother. All the experiments were performed in electrolyte
of 0.01 M NaCIO .
4
Table Ί Chemical compositions for the sulfide mineral samples.
Element (X) Fe S Zn As Pb Co Ni Sb Cu SiO
Pyrite 43.6 52.5 0.47 N 0.07 N 0.01 N 0.03 0.25
Arsenopyrite 32.2 18.7 0.10 44.4 0.74 0.22 0.24 0.64 0.07 0.55
Glaucodot 20.0 20.0 0.12 43.0 0.04 11.8 0.35 0.05 0.90 0.55
Sphalerite 0.63 32.3 65.2 N 0.11 N 0.05 N 0.05 0.45
Galena 0.17 13.1 0.21 N 85.3 N N N 0.01 0.15
N means below the detection limit.
Flotation Tests
The flotation tests were performed using a Labor-Flotation cell (Clausthal, West
Germany). Five grams of the prepared mineral samples were first conditioned in
150 ml solution for ten minutes. MIBC was then introduced at a concentration of
15 mg/1. Flotation was commenced immediately. Unless elsewhere stated, flotation
time was five minutes. The pH value of the pulp was adjusted during
conditioning. The pH value and potential (measured by a platinum electrode) of
the tailing are referred to flotation pH and pulp potential respectively.
Dissolution Tests
6 PROCESSING OF COMPLEX ORES
Five grams of the prepared sample 100
(75-40 μτη) was conditioned under pH not controlled . Co-ASPY (-120+75 \im)
Flotation :5 min.
nitrogen atmosphere for 15
^80
minutes and the suspension pH was
kept at constant by adding
NaOH/HCIO . The suspension was §Φ 60 Να2520, KMnO,
o
4
Φ
filtered through 0.2 μπι filter (Z
Λ0
.Ι
paper using a Milli-Pore
apparatus. 20 ml solution was σ
diluted to 100 ml by concentrated
Ü-20
HNO . The total metal
3
concentration was measured using
-8
atomic absorption spectrometry. 00 -11 0 100 200 300 400
Ept(mV)
Zeta-Potent i al Measurements
Fig. 1 Flotation recovery of glaucodot
0.10 grams of the prepared -20μιη
as a function of redox potential.
sample was added into a 100 ml
de- oxygenated solution and
conditioned under nitrogen
100,
atmosphere for 15 minutes. The Co-ASPY(-120 + 75um)N2
suspension was then left for five
minutes in order to allow the
coarse partciles to sediment. The
sample used for the zeta-
potential measurement was take
from the top of the suspension
using a syringe. The zeta-
potential was measured using a
Laser Zee zeta-meter (Model 501,
PenKem, Inc.).
RESULTS
Flotation Without EDTA and
Fig. 2 Flotation recovery of glaucodot
Xanthate
as a function of pH in the absence and
presence of 1.0*10'4M EDTA.
Of the minerals tested, only
PROCESSING OF COMPLEX ORES
glaucodot shows good native
100
floatability in the absence of
Galena, -75*40 p.m
EDTA and xanthates. Its
EDTA =0.5mM
floatability is not affected by
vo 80
conditioning gases: H , N or 0
up to pH 11. However/ the l_
CD
> 60
addition of either a strong O
u
reducing (Na S 0 ) or an 0)
cr
3 2 2 4
c ¿0
oxidizing agent (KMnO ) o
decreases considerably the O
floatability of glaucodot, as 2 20h
shown in Figs. 1 and 2.
Flotation with EDTA
The floatabilities of pyrite,
galena, arsenopyrite and 100
glaucodot in EDTA solution o -120 ♦ 75 μηη EDTA = 5x1(JAM
Δ -75*40μηη PYRITE
depend strongly on the pH value
'80
and EDTA concentration. The
flotation recovery of glaucodot
<D
as a function of pH in the > 60
o
presence of 1.0*10"4M EDTA is υa >
CU
shown in Fig. 2. The
|¿0
floatability of glaucodot is
a
almost unaffected in the pH
jo
range 6-10, however, it is Ü. 20
significantly reduced in acidic
solutions (pH<6). The
i i i I b
floatabilities of galena,
pyrite and arsenopyrite as a
function of pH are presented
Fig. 3 Flotation recovery of freshly ground
in Figs. 3 and 4, while no
galena (a) and pyrite (b) as a function of
flotation was observed for
pH in the presence of 5*10"4M EDTA.
these minerals in the absence
of EDTA. In the presence of
5*10"4M EDTA, all the minerals exhibit good flotation in the pH range 6-10
while flotation is low or absent up to pH 5 and above pH 11.