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.