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Geometalurgia
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Structural properties of clays and their effect on the recovery of copper sulphides by flotationLina Uribe1, Leopoldo Gutierrez1, Oscar Jerez 2
1 Departament of Metallurgical Engineering, Universidad de Concepción, Concepción, Chile2 Instituto de Geología Económica Aplicada (GEA), Universidad de Concepción, Concepción, Chile
Outline› Background› Objectives› Experimental methodology› Results› Conclusions
Background› The grades of the major copper deposits in Chile have decreased
which has caused that the treatment of more complicated ores containing high levels of complicated gangue is more common today. Clay minerals are the most typical.
› The presence of clay minerals affects several stages in the mineral processing chain, i.e., grinding, froth flotation, thickening, dewatering and final disposal.
Background
Background1. Slime coating on the mineral surfaces
Hydrophilic coating
Hydrophobic particle
Less hydrophobic
particle
Fine clays
Valuableparticle Bubble
Background2. Changes in pulp rheology, higher viscosity (h) and yield stress (to)
vp vb
h, t0
Slurry
Background3. Changes in froth stability
Zona de colección
Zona de limpieza
Burbuja
Particula valiosa hidrofóbica
Particula no valiosa (Ganga)
Froth
If the froth is unstable froth recovery decreases.
Background4. Non specific reagent consumption.
The lower the particle size, the higher the specific surface area. This could lead to higher non specific reagent consumptions.
1L Cube
1L Cube
10 cm
10 cm
10 cm
0.5 mm (500 microns)
8 x 106 particles
12 m2 surface area
10 cm
10 cm
10 cm
0.01 mm (10 microns)
1 x 1012 particles
600 m2 surface area
Bubble
Background5. Coating of air bubbles with fine clay particles
Hydrophobicbubble
Less hydrophobic
bubble
Fine clays
Hydrophilic coating
Bubble
Background
Although there is evidence that validates the aforementioned mechanisms, there is still a lack of understanding on the effect of clays on the process of flotation of copper sulphide minerals.
A better solution can be obtained
ObjectivesSpecific objectives
To study the effect of fine particles of kaolinite and montmorillonite on:
› Floatabilty of copper sulphide minerals
› Induction time
› Slime coating
› Reagent consumption
Experimental methodologySamples and reagents
Sample Quantitative XRD mineralogy(Chipera and Bish, 2001)
CECcmol/kg
BET(Kelm and
Helle, 2001)
kaolinite 96% kaolinite, 3% anatase, 1% other traces 0.7 180
Montmorillonite 75% montmorillonite, 16% feldspar, 8% quartz, 1% other traces 100 117
Chemical analysis Calculated mineralogical compositionCu % 23.6 Sb % 0.1 CuFeS2 % 68.1Fe % 30.1 As % 0.2 FeS2 % 20.2
Mo % 0.1 Bi % 0.0 MoS2 % 0.08Zn % 1.2 S % 36.1 Quartz % 11.61Ag % 0.0 Insols % 8.5Pb % 0.1
-Copper sulphide sample: copper concentrate sample
-Kaolinite and montmorillonite: Clay Minerals Society.
Experimental methodologyClay samples
Figure 1. Kaolinita. Figure 2. Esmectita. Kaolinite montmorillonite
Mean size, microns
Top size, microns
Kaolinite 4.4 21Montmorillonite 3.9 19
Copper concentrate 119 206
Experimental methodologyMicro-flotation tests
› 130 mL Patridge and Smith glass cell 20 mL/min N2, 2 minutes flotation. › The flotation feed was prepared mixing known amounts of the copper concentrate sample with fine clay
particles at different proportions (0, 300, 400, 500, and 1,000 ppm or mg of clay per litre of water). › PAX and MIBC were used at concentrations of 400 and 200 ppm respectively.
Experimental methodologyInduction time measurements
Bed of particles
(1)(2)
(3)
Solution
(a) (b)
Idea developed by Glembotsky (1953). › A bubble is contacted with a bed of particles for measured and controlled contact times. Then the bubble
is observed through a microscope to determine whether attachment occurred during the contact time or not.
› The final result of the test is a plot of percentages of successful contacts (N sc) versus the measured contact time (tc). In this work, the induction time was obtained by determining the contact time at which 50 % of the contacts were successful.
0 100 200 300 400Contact time, ms
0
10
20
30
40
50
60
70
80
90
100
Perc
enta
ge o
f suc
cess
ful c
onta
cts,
%
45.4 ms
Experimental methodologySlime coating
If slime coating occursthen T2<T1
Suspension Clay
Turbidity=T1
Suspension Clay+Chalcopyrite
Turbidity=T2
(a) (b)
ResultsMicro-flotation experiments
0 200 400 600 800 1000 1200Additions of kaolinite, ppm
70
75
80
85
90
95
100
Conc
entra
te y
ield
, %
K aolinitepH 9.5pH 10.5
200 400 600 800 1000 1200Additions of montmorillonite, ppm
MontmorillonitepH 9.5pH 10.5
ResultsInduction time
0 100 200 300 400Contact time, ms
0
102030405060708090
100
Perc
enta
ge of
succ
essf
ul co
ntac
ts, %
pH 9.5pH 9.5 (Equation 1)pH 10.5pH 10.5 (Equation 1)
45.4 ms
68.3 ms
0 200 400 600 800 1000Clay content, ppm
0
50
100
150
200
250
300
350
400
Indu
ctio
n tim
e, m
s
Kaolinite (pH 9.5)Kaolinite (pH 10.5)Montmorillonite (pH 9.5)Montmorillonite (pH 10.5)
Results
Bubble coated by clay particles. tc = 500 ms, PAX 40 ppm, pH=9.5.
Bubble coated by clay particles. tc = 1000 ms, PAX 40 ppm, pH=9.5.
Fine clays Copper concentrate
particles Fine clays
Copper concentrate
particles
Coating of air bubbles with fine clay particles.
These pictures were taken during the induction time measurements. They show that fine clay particles adsorb on the bubble surfaces.
ResultsSlime coating
0 200 400 600 800 1000 1200Additions of kaolinite, ppm
0
200
400
600
Turb
idity
, %
Kaolinite, pH 8.5Without CpyWith Cpy
0 200 400 600 800 1000 1200Additions of kaolinite, ppm
0
200
400
600
Turb
idity
, %
Kaolinite, pH 9.5Without CpyWith Cpy
0 200 400 600 800 1000 1200Additions of kaolinite, ppm
0
200
400
600
Turb
idity
, %
Montmorillonite, pH 8.5Without CpyWith Cpy
0 200 400 600 800 1000 1200Additions of kaolinite, ppm
0
200
400
600
Turb
idity
, %
Montmorillonite, pH 9.5Without CpyWith Cpy
If slime coating occursthen T2<T1
Suspension Clay
Turbidity=T1
Suspension Clay+Chalcopyrite
Turbidity=T2
(a) (b)
Conclusions› The presence of clay particles reduced the floatability of a
copper concentrate sample. These results agree with the induction time data.
› Among the mechanisms that explain this type of behavior are slime coating and coating of bubbles with fine clay particles.
› Its seems that the phenomenon of coating of valuable particles with fine clays becomes more relevant on the process of flotation only when the clay concentration is above 500 ppm.
› When sea water was used the general trends were similar but with some important deviations (montmorillonite).
Conclusions› Currently, the solutions used to treat minerals with high clay
contents relate to dilute the pulp, blending, mineral or simply discarding.
› The following lines of action are proposed to find solutions to the problem of altered minerals with high clay contents:× Process design including desliming or removal of fines (In development
Dimet-UdeC).
× Development of flotation reagents which avoid the negative effects of phyllosilicates (In development Dimet-UdeC).
ACKNOWLEDGEMENTS Professor Ursula Kelm of the GEA Institute of the
University of Concepcion. Water research center for agriculture and mining
(CHRIAM center UdeC-Fondap). Proyecto Fondecyt Iniciación N°11140184. The University of Concepcion, project VRID
N°214.095.089-1.0.
THANKS!