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Ian Wark Research InstituteAustralian Research Council Special Research Centre
For Particle and Material Interfaces
21st Century Challenges in the Chemistry of
Minerals Processing
John Ralston
john.ralston@unisa.edu.au
DELPRAT LECTURE 2014
Under the umbrella of the Metallurgical Society of the AusIMM
1
ENGINEERING APPRENTICESHIP IN SCOTLAND
SCIENCE AND PHYSICS CLASSES AT NEWPORT
LEARNED DIFFERENTIAL AND INTEGRAL CALCULUS FROM HIS FATHER
LANGUAGES: ITALIAN FRENCH ENGLISH, GERMAN AND DUTCH
ACTED AS ASSISTANT TO J. VAN DER WAALS, PROFESSOR OF PHYSICS AT
THE UNIVERSITY OF AMSTERDAM.
VAN DER WAALS FORCES ARE A KEY FOUNDATION FORCE IN COLLOID
AND INTERFACE SCIENCE, THE HEART OF MINERAL PROCESSING
CHEMISTRY.
Guillaume Delprat:1856-1937A Dutchman by birth, inventor of the industrial froth flotation
process, with Potter, while GM at BHP Broken Hill
Guillaume Delprat
Linguist, scientist, industrialist and inventor
What are the imperatives driving the
minerals industry?
• Energy reduction
• Water minimisation
• Environment (including GHG emissions, REACH etc)
• Capital efficiency
• Process flexibility
Requiring INCREMENTAL, STEP CHANGE and TRANSFORMATIONAL
Research.
This research is often best when it is cross-disciplinary. One field
stimulates and informs another.
4
The Coming Copper Peak:2040? Assumptions Correct? Other Metals?
• SCIENCE
• Vol 343
• Feb 2014
Pages722-724
Based on work by Mohr, Giurco, Mudd, Weng
and Northey
LECTURE OVERVIEWModern solution and structural chemistry, interfacial physics and
surface chemistry, in combination with electrochemistry, advanced
mathematics and mineralogy have facilitated significant advances in
the science and practice of the chemistry of minerals processing.
Colloid and interface science lies at the heart.
The focus is on:
• Flotation of complex sulphide minerals, including the influence
of surface composition, grinding conditions, polymers and
water quality, coupled to a predictive model.
• Aggregation of tailings particles and efficient dewatering.
• Bayer Liquors.
which can be quantified in terms of benefit to industry. Some of this is
incremental, some step change research. We are now poised on the
verge of transformational breakthroughs in minerals processing
chemistry.
Let us commence with flotation
Tribute to Wark and Sutherland- great advances but studies limited
to relatively simple systems, flat surfaces.
Work immortalized in “Principles of Flotation” [ AusIMM 1955].
CSIRO stalwarts: Kelsall, Trahar, Woods, Buckley, Biegler, Rand,
Warren made great contributions.
The Australian School of Colloid and Interface Science [ initially
Alexander, then Healy, Hunter, Ninham] paved the way for a great
understanding of mineral processing problems. For example metal
ion adsorption: James Healy model; and Hunter’s work on clays
In North America, Gaudin is a legend. Fuerstenau; Hogg; the Finch
McGill team, Miller in Utah, Somasundaran in NY, Moudgil in Florida,
the UBC and U of A teams, the US Bureau of Mines in past days.
Elsewhere: U of Cape Town, European [ Germany , Russia,
Finland] , Japanese and indian centres have also contributed.
FOCUS IS ON MAJOR ADVANCES IN COLLOID AND
INTERFACE SCIENCE WITH AN AUSTRALIAN VANTAGE POINT
8
9
Do all particles require the same
contact angle/surface coverage
to float?
12
dp = 62 µm
0
20
40
60
80
100
0 10 20 30 40 50 60 70
contact angle (º)
rec
ov
ery
(%
)
crit. = 36º
dp = 368 µm
0
20
40
60
80
100
0 10 20 30 40 50 60 70
contact angle (º)
rec
ov
ery
(%
)
crit. = 45º
COLUMN FLOTATION
db = 0.8 0.7 mm
Gfr = 4.3 0.4 cm3 min-1
NO, there is a
critical contact angle/surface coverage
necessary for particle flotation
13
dmax,g
dmax,kinetic
column
O column
Rushton Turbine Cell
Crawford and Ralston 1988 Column
We can float big particles!
Need slow bubbles!
As Vb becomes smaller,
approach dmax,g limit!
Gontijo, Fornasiero and Ralston
Can J Chem Eng 85 739 2007
What happens to particle
surfaces during grinding?
GRINDING ELECTROCHEMISTRY
Optimising grinding chemistry (pH, Eh, grinding media,
aeration) for maximum Cu/Pyrite selectivity
Are particle surfaces pristine
or of mixed composition?
Interrogation of Mineral Surface Chemical Heterogeneity with
Advanced Surface Analysis Techniques
ADVANCED SURFACE ANALYSIS TECHNIQUES
Bulk
S Poly
S DiS Poly
S Di
BulkS Poly
Bulk
S Di
Synchrotron XPS
Chalcopyrite with Bornite S 2p
Fresh Fracture pH 9 oxidised pH 1 leached
What is the influence of mixed
surface composition or
roughness?
Roughness influenceOn contact line motion
roughness slows wetting! The molecular kinetic theory capture the experimental data trend for all
nanorough surfaces investigated.
Ramiasa, Ralston, Fetzer et alJ. Am. Chem. Soc. 2013, 135, 7159−7171
Do solution chemistry and
water quality influence
flotation?
Mining of ore (underground or
open-cut mining)
Processing of ore (crushing, grinding, flotation)
Process water (from desalination plants, lakes, boreholes, rivers or
other sources)
Waste rock
Mineral product
Tailings to tailings dam
Process Water Chemistry Influences –
Plant Flotation at ‘constant’ head grade
Flotation Performance in Different Waters at Mine
Site “A” [ ‘constant’ feed head grade]
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70 80 90
Sulphur Recovery (%)
Su
lph
ur
Gra
de
(%
)
Process Water
Tails Thickener O/F
Tails Dam Return Water
Ground Water 1
Ground Water 2
Surface Water 1
Surface Water 2
Metal Ion Hydrolysis and
Adsorption play a major role in
influencing flotation response
Hydrolysis and Adsorption of Metal Ions
and Their Activation of Quartz.
• Work of D W Fuerstenau and colleagues in 1960’s
Adsorption of Co[II] on to silica
The silica surface is negatively charged. A key step in understanding is
the role of the first hydrolysis product in the adsorption process. The
hydration energy of the adsorbing species is paramount; hydroxylation
reduces the charge and permits adsorption to occur.
[James Healy Model]
For Calcium [II] ions, the relevance to cement backfill is enormous!!
What role can polymers play in
modifying surfaces and
interactions?
Serpentine and pentlandite
interaction:
an Atomic Force microscopy
(AFM) study
++
+
+
serpentine pentlandite
electrical
attraction
(pH 9.5; [pentlandite] = 1.2 g/L; [PAX] = 6.5x10-5 M)
10864200
20
40
60
80
Flotation time
(min)
Pen
tlan
dit
e r
eco
very
(%
)
0
0.020.05
0.11
serpentine (g/L)
-0.06
-0.04
-0.02
0
0.02
0 20 40 60 80 100
Apparent separation, nm
F/R
, mN
/m
pH 5.3
pH 9.4
AFMrepulsion
attraction
pentlandite
AFM piezo
cantilever
serpentine
10-3 M KNO3
31
0
2
4
6
8
% N
i G
rad
e
80604020000
4
8
12
% Ni recovery
% M
gO
re
co
ve
ry100
100
200
200
300
300
500
500
700
700
900
900
CMC (g/t)
4
5
6
7
8
9
10
90807060504030201
2
3
4
5
6
% Ni recovery
% M
gO
re
co
ve
ry%
Ni G
rad
e
CMC (g/t)
200
400
800
0
0 200 400
800
ore 1 ore 2
Dispersion of MgO slimes Dispersion and depression of MgO slimes
pH 9
32
Can we predict flotation rate
constants?
bubble] a passingcylinder
oflength
processes ay essentiall m, of [units 1-min1-m of units
elementary termrbulenceprimary tu termmechanical
p.Ns.Ea.EcE
fV1 .
32
f
31
97
bd 9
4 0.33
r.V
bd
frG
2.39- dt
pdN
rate constant, k units of min-1
… 1
Essentially we have a “front end”, consisting of a mechanical term and a primary
turbulence term. These need to be determined from measured variables. We can then
turn to the calculation of Ec, Ea and Es in sequence.
See: Pyke,Fornasiero and Ralston,
Journal of Colloid and Interface Science 265 (2003) 141–151 [Theory]
And Ralston , Fornasiero, Grano, Duan andAkroyd
Int. J. Miner. Process. 84 (2007) 89–98 [ Practice in Plant]
We need to make a connection to the various engineering models that have
been, and are presently being used.
The superficial gas velocity, Jg, for a flotation column of diameter D is given by
and Sb, the superficial area rate of bubbles is
Either quantity can be introduced into the mechanical term in equation (1).
Gfr, db, Vr and derived quantities such as Jg and Sb can be determined with relative ease.
2D/2
frG
gJ
bd
g6J
bS
Pressure Probe to Measure Local
Turbulent Energy Dissipation which
Controls Coarse Particle Flotation
And Bubble-Particle Collision Rate
[ adapted from Cobra Probe, Turbulent Probe
instrumentation]
High Pulp Density Dampens
Turbulence
Pressure Probe at Local
Points in Cell
38
0
1
2
3
4
5
6
0 20 40 60 80 100
k (
min
)
-1
d ( 10 m)p-6
Comparison between the calculated (line) and experimental (circles) flotation rate constants as a function of quartz
particle diameter (Experimental parameters: dp=1.4x10-3 m; agitation=650 rpm; Gfr=3.5x10-3 m3 sec-1; advancing
water contact angle=80o; A=0.051 and B=0.6 (equation 26). Calculated parameters: Vfl=vb=0.18 m sec-1; dissipation
energy=38 m2 sec-3).
Quartz Flotation ( = 80°)
B.L. Pyke, D. Fornasiero and J. Ralston, “Bubble Particle Heterocoagulation Under Turbulent Conditions”, Journal
of Colloid and Interface Science, 265, 141-151 (2003).
39
- Application of the Wark Model to Plant Flotation Data
0
10
20
30
40
50
60
70
80
90
100
1 10 100 1000Particle Size (microns)
Cu
mu
lati
ve C
op
per
Su
lph
ide R
eco
very
(%
)
Cell 1
Cell 2
Cell 3
Cell 6
Cell 12
Model
This is the First
Known Application
of a Comprehensive
“Property Based”
Model to an
Operating Plant
The Simulation can
then be used to
Optimise Size and
Mineral Specific
Flotation
40
MODEL:
Pro: basic physics and chemistry accounted for,
as well as microprocesses.
Cons: needs to be widely applied; body forces can also
be accounted for, as well as particle rebound.
If bubble-mers are important, can readily be
accounted for (need population).
Further development involves measurement
of particle and bubble velocities, better attachment
model. Froth Efficiency, Ef can easily be included
if not unity[ shallow froth] -with a model or
measurement
How do we deal with tailings?
Focus on research conducted by David Boger, Tom Healy, George Franks, Peter Scales and teams at U Melb.
We do not want this!
Rheological Behaviour
Rheological behaviour as tailings thicken
Yield Stress of red mud as a function of concentration from different alumina samples
Vane Device for Yield Stress Measurements
Cylindrical Slump Test
Dilute tails
Flocculant
Recycle water to process
Thickened pulp
to dam
Primary Dewatering
Secondary
Dewatering
Interfacial Chemistry and Water Minimizationin Tailings Treatment
Flocculation/
Aggregation
adsorbed polymer
electrostatic, hydrophobic
or chemical attraction
X
X
X X
X
X
49
.
Stimulant responsive flocculation
• Produce both fast dewatering, low cake moisture
• and low viscosity
• Turn the attraction on an off when needed using a stimulus
• Stimuli include pH and temperature
• Produces attraction only
• Aggregation
• Rapid sedimentation
• High moisture in sediments and cakes
• High viscosity
Conventional Flocculation
Smart Temp. Responsive Polymer Poly(N-Isopropylacrylamide) (PNIPAM) NB
structure can be altered to ‘tune effects’.
Water Soluble
Molecules
Poorly Soluble
Hydrophobic
Molecular Aggregates
N H
=O
N H
=O H
O H
H
O H
N H
=O
N H
=O H
O H
H
O H
Heating above
critical Temp.
Cooling below
critical Temp.
+ 4H
O H
Consolidation after 24 hours - 10 micron silica with 10 ppm PNIPAM or 10 ppm PAM
PAM = conventional poly acrylamide flocculant
Settling
Consolidation
Conventional flocculant
PAMPNIPAM
50oC 50oC
22oC 22oC
Sediment density:
47vol% solids
Settling rate:
20 m/hr
Sediment density:
31vol% solids
Settling rate:
18 m/hr
Sediment density:
16vol% solids
Sediment density:
16vol% solids
PNIPAM as Consolidation Aid
Adsorbed negatively charged polymers cause increased electrostatic repulsion and
repulsive steric forces, and reduced friction and adhesion
friction is
reduced
without
polymer
with
polymer
frictionis high
Control of the rheological and flow characteristics of
slurries with specific reference to
their transport through a pipeline
53
We can have our cake and sit on it too!
Research into Bayer Liquor Chemistry was conducted
by the Alumina industry, through AMIRA International and
a team of Australian universities [ Curtin, Murdoch, UniSA],
CSIRO and the AJ Parker Centre during the 1990s- P380
project. The objectives were to understand:
[a] the fundamental solution and surface mechanisms that
underpin the crystallization of gibbsite from concentrated
alkaline solutions;
and [b] the aggregation mechanisms in the presence of
seed crystals, with the intention to improve practice through
this knowledge.
•Gibbsite Dissolution:
g-Al(OH)3(s) + pNaOH(aq) NaAl(OH)4(aq) ) + (p-1)OH(aq)
b) Bayerite:
a-Al(OH)3(s) + pNaOH(aq) NaAl(OH)4(aq) + (p-1)OH(aq)
•Boehmite Dissolution :
AlOOH(s) + H2O + pNaOH(aq) NaAl(OH)4(aq) + (p-1)OH(aq)
4 < p < 6 with initial [Al]/[NaOH] ~ 0.72
Pregnant Bayer Liquors
Preparation:Leaching of hydrous alumina containing minerals (Gibbsite, Bayerite and Boehmite) present in bauxite in hot (150-240 oC), concentrated Caustic solution (4-6 M NaOH)
•The resulting Pregnant Bayer Liquors are seeded at 60 – 90 0C to crystallize gibbsite
Al(OH)4-
NaAl(OH)4o
Na+
AlO2(OH)62-
OH-
NaOHo
NaOHT, M
2 4 6 8
Species concentration, M
7
6
5
4
3
2
1
Speciation of supersaturated sodium aluminate solutions
Speciation as a function of caustic concentration, temperatures to 100 C.
AMIRA: - Alumina Industry Project P380 Report 1999).and:Sipos, Journal of Molecular Liquids 146 (2009) 1–14
From Solution Chemistry Studies we find
Water activity has little impact on growth rate.
The sodium ion is of primary importance in
determining the kinetics
– The sodium ion is very important in the growth
mechanism
– Sodium probably acts via its strong surface adsorption
rather than a speciation effect.
Alkali ion mediated agglomeration
Larger
Agglomerates
in Na-based
than in K-
based
suspensions
A A’
B’B
C C’
Na
K
I A N W A R K R E S E A R C H I N S T I T U T E
ARC SPECIAL RESEARCH CENTRE for PARTICLE and MATERIAL INTERFACES
UNIVERSITY OF SOUTH AUSTRALIA
Alkali ion-mediated gibbsite interactions:
Colloid probe AFM studies
Na
Na
K
K
Interparticle Adhesion
Force greater in Na-based
than in K-based Bayer
liquors
Can we judge the valueof Research to Industry?
61
Remember:
Methodology: example for flotation related
research, equally applicable for other areas
A stage approach used to evaluate incremental and
step change research through RMDSTEM. Specific
AMIRA based P260 project series.
STAGE 1
Design
Questionnaire
STAGE 3
Send
transcripts
to respondents
for validation
STAGE 4
Perform
Analysis
STAGE 2
Conduct
Phone
Interviews
STAGE 5
Compile
Presentation
and Report
63
Delivered and Expected Value
Value of P260
0
50
100
150
200
250
300
350
400
450
500
Delivered Value NPV 318 $M Expected Value NPV 118 $M
NP
V $
M
Respondent 13
Respondent 12
Respondent 11
Respondent 10
Respondent 9
Respondent 8
Respondent 7
Respondent 6
Respondent 5
Respondent 4
Respondent 3
Respondent 2
Respondent 1
The total funding for the AMIRA Project P260 was 23.6 $M and the minerals industry provided
20.3 $M [ first phase of study].
The benefits (NPV) to cost ratio is 21.5:1 For industry Benefits are now over 1 Billion AU[
second phase of study]
Total Value Now
over 1B AUD
64
How did this happen for minerals processing
chemistry?
Very bright , committed researchers , carrying out first
class fundamental and applied research, worked in
parallel
with first class industrial engineers and
scientists, plus committed senior managers
who took a long term view.
Key Issue: researchers must FIRST ask
industry to explain their problems.
Cooperation starts from this
The tap cannot suddenly be switched on or
off- research engagement is like a marriage.
The BIG problem now is attracting first class
talent in universities and industry coupled to
visionary senior management. Serious
financial commitment is essential.
66
TRANSFORMATIONAL CHEMICAL
RESEARCH
Liquid-liquid solvent extraction (SX) is the transfer of a solute between immiscible liquids
SX is a key unit operation in mineral processing (e.g. recovery and concentration of copper, nickel, uranium , rare earths and precious metals)
67
1 SOLVENT EXTRACTION IN MICROFLUIDIC
DEVICES [ MICRO SX ]
Microfluidic Chip
Conventional SX
Solvent extraction is generally carried out in a mixer-settler in the
minerals industry.
The process involves several key elements:
1. Contacting the liquid phases to allow extraction (mixing)
2. Separating the liquid phases after extraction and isolating the valuable
species (phase disengagement/settling).
3. Recovery of the valuable species from the separated phase
Mixer residence
times 1.5 to 5 mins
Settler residence
times 2 to + 10
minutes
Extraction time typically
several minutes
68
This is how we do it:
Rate ComparisonInfluence of particles on performance?
No crud formation, flow is stableNo fouling (> 7 h continuous operation)
Extraction rate unchanged
Where are the particles?
70
Stream Flow (no dispersion)
Extraction time:
A – cross-section area of the channel
L – length of the channel
Q – volumetric flow rate
Key differences
No impeller or large-scale settler required
Interfacial area determined by channel geometry (not droplet size)
Phase disengagement via Y-junction (no coalescence required)
Closed system; no loss of material through evaporation
Microchip Design
contact
ALt
Q
71
Multiple Unit Operations (MUO) for
High Throughput Applications
FeatureProduction controlSimplification of systemProductivity improvementDeploy the risksProcess rationalization
72
Facilities: Fabrication
EVG 520 Hot Embosser
73
Is there a precedent for scaling up? Yes e.g
Australian Invention: Memjet
774 million drops per second , 1 A4 page per second at 1280 dpi
• EXTEND THIS TECHNOLOGY TO MICROFLUIDIC SOLVENT
EXTRACTION!!
……………
11 000 ejections per second
11 chips, 70,400 nozzles
6400 nozzles, 5 colours
1Summary1 chips per Summary Data
2.The Future of Chemistry in Minerals
Processing
Focus on disruptive technologies.
What will the resources and energy industries look
like in two decades from now?
Their footprint will need to be much smaller ;
Energy consumption a fraction of what it is
now;
Water will be expensive and scarce;
Emissions of any form will need to be 5% of
what they now are.
Future 2
A. Super sensitive identification: geophysical and sophisticated
sensor/surface techniques will revolutionize deposit identification,
processing and extraction. Much is underway now.
B. Big Data analysis will be routine and is already being selectively
used.
C. Pulsed blasting that generates micro and smaller fractures in
rocks will lead to in situ processing with reactive fluids [ aqueous
based and other] yielding pregnant solutions.
D. Valuable elements will then be selectively extracted using
ultrafast, small scale, highly efficient micro-solvent extraction
techniques followed by electrowinning and /or ‘electroless’
deposition of metals or their compounds.
A, C and D all involve clever chemistry!
ACKNOWLEDGEMENTS
David Beattie
Jonas Addai-Mensah
Magnus Nyden
Daniel Fornasiero
Stephen Grano
William Skinner
Roger Smart
Melanie Ramiasa
George Levay, Levay and Co Env S
David Boger, U Melbourne
George Franks, U Melbourne
Carlos Gontijo [ Vale]
Tom Healy, U Melbourne
Brendan Pyke [ BHP-B]
Rossen Sedev
Renate Fetzer
Craig Priest
Roger Horn
Marta Krasowska
Takehiko Kitamori U Tokyo
Kristen Bremmell
Paul Jenkins
Max Zanin
John Morgan, Pooled Energy
Chris Greet, Magotteaux Australia
Chris Vernon, CSIRO
Glen Hefter, Murdoch
Peter May, Murdoch
80
Some Wonderful
Contributors:
Magnificent Sponsors:
Australian Research Council, AMIRA International,
COST, UniSA, AREVA NC, Rio Tinto, BHP-Billiton, Xstrata, Orica,
Freeport McMoran, Anglo Platinum and over 20 other companies,
Swiss National Science Foundation.
Key Reference 1:
J.Ralston, D.Fornasiero and S. Grano, “Pulp and Solution
Chemistry”, p 227-258 in Froth Flotation: A Century of
Innovation, Edited by M.C. Fuerstenau, G. Jameson and R-H
Yoon, Society of Mining, Exploration and Petroleum Inc,
2007.
Key Reference 2:
David V. Boger , “Rheology and the resource industries”, Chemical Engineering
Science 64, p4525 -- 4536 ,2009.
Key Reference 3:
C.Priest, J.Zhou, R. Sedev, J Ralston,A. Aota. K. Mawatari,T Kitamori,
“Microfluidic extraction of copper from particle-laden solutions”,
International Journal of Mineral Processing, 98, p 168-173, 2011.
Key reference 4:
P.Sipos,” The structure of Al(III) in strongly alkaline aluminate solutions — A
review”, Journal of Molecular Liquids 146, p1–14,2009.
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