a study of copper extraction kinetics with lix … study of copper extraction kinetics with lix 984n...
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A study of copper extraction kinetics with LIX
984N using a Lewis cell
Presented by
Wensheng Zhang
8 July 2011
by Wensheng Zhang, Fuping Hao, Yoko Pranolo, Chu Yong Cheng, and Dave Robinson
Content of presentation
1. Introduction
• SXT2 – an Industry Sponsored Project
• Review of techniques for kinetics study
• Development of an improved Lewis cell
2. A kinetic study on Cu solvent extraction
3. Conclusions
A study of copper extraction kinetics with LIX 984N using a Lewis cell
CSIRO SXT2 Project;
Improved Performance by Reduction of Entrainment
• Operational impact;
• Understanding of flow field, drop size and
entrainment loss
• Improved mixer design for optimum drop size
generation
• Improved settler design for improved
coalescence
• Physical modelling;
• Development of velocity and interface probes
• On-site measuring flow pattern and drop size
• CFD modelling;
• Drop size distribution, flow pattern and
residence time distributions
• Changes in mass transfer and kinetics
• Changes in design and operational parameters
• Mass transfer and entrainment;
• Developing measurement techniques
• Establishing rate equation and mechanism
• Incorporation in CFD models
A study of copper extraction kinetics with LIX 984N using a Lewis cell
CFD models for drop size and mass transfer in mixers
Solvent extraction kinetics principles
• Extraction regimes;
• Diffusion regime
• Kinetic regime
• Mixed regime
• Reaction locations;
• In the bulk phases - homogeneous
• At interface – heterogeneous
• Key parameters;
• Stirring speed
• Interfacial area
• Temperature
• Species concentrations
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Techniques 1 – Highly stirred tank
• Features;
• One phase dispersed in the other
• Similar to practical SX conditions
• Reactor readily available
• Easy to operate
• Disadvantages;
• Hydrodynamic complex
• Difficult to control interfacial area
• Uncertainty in the derived
extraction regimes
• Not suitable for fast kinetics
A study of copper extraction kinetics with LIX 984N using a Lewis cell
A/O O/A
A/O/A O/A/O
Techniques 2 – Moving drops
• Features;
• Good control of drop size
• Known interfacial area
• Simple set-up and operation
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Falling drop Rising drop
Techniques 2 – Moving drops
• Disadvantages;
• Complex and variable hydrodynamics
• Difficult to determine the degree of
turbulence
• Uncertainty in extraction regimes
• Not suitable for very fast or slow
kinetics
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Techniques 3 – Lewis cell
• Features;
• Constant interfacial area
• Hydrodynamics well controlled
• Hydrodynamic calibration feasible
• Disadvantages;
• Difficult to maintain stable
interface under turbulent flows
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Lewis cell by Lewis 1954
CSIRO Lewis cell features and performance
• Design features:• Curved horizontal baffles
• Centred vertical baffles
• Cylindrical grid
• Two shafts separate controls
• 45° pitched blade turbines
• Water jacket for temperature control
• Auto pH control
• Continuous on-line analysis
• Clear body for visual observations
• Determination of EX regimes;
• Maintaining constant interfacial area
in a wide range of turbulent flows
• Extraction locations;
• Able to vary interfacial areas
• Separate phase stirring speeds
A study of copper extraction kinetics with LIX 984N using a Lewis cell
CSIRO Lewis cell set-up for kinetic study
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Lewis Cell
Water bath
On-line
UV-Vis analyser
Experimental for Cu kinetic study
• Typical aqueous feed solution
• 2 g/L Cu as sulphate
• Typical organic solution
• 10% (v/v) LIX 984N (LIX 860 + LIX 84 at 1:1, supplied by BASF/Cognis)
• In Shellsol D70
• Typical test conditions
• 30°C
• pH 1.8
• 150 rpm in both phases
• Analysis
• Organic phase continuously measured by an on-line UV-Vis analyser
• ICP for off-line calibration
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Effect of stirring speed
0
50
100
150
200
250
300
0 5 10 15 20 25 30 35
Time (min)
Cu
extr
acti
on
(m
g/L
)
0 rpm
50 rpm
60 rpm
180 rpm
200 rpm
220 rpm
240 rpm
260 rpm
280 rpm
• Linear function of Cu
extraction with time
• Initial rate determined by
the slop values
A study of copper extraction kinetics with LIX 984N using a Lewis cell
At 20°C and pH 1.8 with 10% LIX 984N in Shellsol D70
Extraction regimes
• Lower speeds – Zone A
• Laminar or less turbulent
• Constant interfacial area
• Diffusion regime
• Higher speeds – Zone B
• Turbulent flow
• Constant interfacial area
• Kinetic regime
• Zone C - even higher speed
• Disturbance of interface
• Varying interfacial area
A study of copper extraction kinetics with LIX 984N using a Lewis cell
pH 1.8 with 10% LIX 984N in Shellsol D70
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 20 40 60 80 100 120 140 160 180 200 220 240
Cu
ex
tra
cti
on
ra
te (
mg
/L/m
in)
Stirring speed (rpm)
20°C
30°C
Zone ADiffusion regime
Zone B Kinetic regime
Re: 8,000-15,000
Effect of interfacial area
• Rate proportional to
interfacial area (A)
• Constant R/A ratio
• Interfacial reactions
A study of copper extraction kinetics with LIX 984N using a Lewis cell
30°C, pH 1.8 with 10% LIX 984N in Shellsol D70
0
0,1
0,2
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
0 20 40 60
Cu
ex
trac
tio
n r
ate
(m
g/L
/min
/cm
2)
Cu
ex
trac
tio
n r
ate
(m
g/L
/min
)
Interfacial area (cm2)
Effect of temperature and chemical species
y = -0,9169x - 1,2687R² = 0,9668
-1,5
-1,0
-0,5
0,0
0,5
1,0
-2,5 -2 -1,5 -1 -0,5 0
Lo
g (
rate
)
Log[H+]
pH 0.4 - 1.8
y = 1,095x - 0,4774R² = 0,9852
-2
-1,5
-1
-0,5
0
0,5
-1,50 -1,00 -0,50 0,00 0,50 1,00 1,50
Lo
g (
rate
)
Log[LIX 984N]
0.1 - 5% (v/v) LIX 984
-1,5
-1
-0,5
0
0,5
1
1,5
2
3,00 3,10 3,20 3,30 3,40 3,50 3,60
Ln
(ra
te)
103 K/T
30-50 C, Ea = 25 kJ/mol
15-25 C, Ea = 67 kJ/mol
Arrhenius type
plot
y = 0,9863x + 2,2663R² = 0,9823
-0,6
-0,4
-0,2
0
0,2
0,4
0,6
0,8
-3 -2,5 -2 -1,5 -1
Lo
g(r
ate
)
Log[Cu2+] (M)
0.1-0.5 g/L Cu
Empirical rate equation
• Empirical rate equation
• Condition range
• pH 0.4 - 1.8,
• [Cu2+]: 0.1 - 1 g/L,
• LIX 984N: 0.1 - 5% (v/v) (0.042 - 0.2 M)
• Temperature: 30°C
A study of copper extraction kinetics with LIX 984N using a Lewis cell
9.0
1.1
o
2
exp]H[
]HL][Cu[kR
Proposed reaction mechanism
Dimerisation
2HLo = HL2o (fast) (1)
Equilibrium
HLo = HLad = HLint-aq (fast) (2)
Complexation of 1st ligand at the interface
Cu2+ + (HL)ad (CuL+)ad + H+ (fast) (3)
Complexation of 2nd ligand at the interfacial Aq side
(CuL+)ad + (HL)int-aq (CuL2)ad + H+ (slow) (4)
Adsorption-desorption of interfacial complex
(CuL2)ad = (CuL2)o (fast) (5)
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Derived rate equations
• Derived rate equation
• Applying Langmuir isotherms for adsorption
Where and are Langmuir constants
A study of copper extraction kinetics with LIX 984N using a Lewis cell
]H[
]HL[]HL][Cu[kR ado
2
/]HL[1
/]HL[
o
o
[HL]ad =
Derived rate equations
• For saturation where 1 << Then [HL]ad = α
• Then the derived rate equation becomes
• In a good agreement with the empirical rate equation
A study of copper extraction kinetics with LIX 984N using a Lewis cell
][HL
]H[
]HL][Cu[kR o
2
2
9.0
1.1
o
2
exp]H[
]HL][Cu[kR
Conclusions
• Excellent performance of the Lewis cell
• Obtained constant interface area under turbulent flows
• Demonstrated by the study on Cu SX kinetics with LIX 984N
• Measurement of Cu SX kinetics using the Lewis cell
• Determined Cu extraction regimes
• Proposed Cu extraction mechanism and rate limiting step
• Established empirical and derived rate equations
• Good agreement between the empirical and the derived
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Lewis cell capability going forward
Industrial sponsors and reagent suppliers’ interest for employing the
Lewis cell for kinetic studies –
• Kinetic characterisation of new SX reagents
• Performance comparison with existing reagents
• Mechanistic studies
• Systematic kinetic studies on real SX operation systems
• Different extractants and their ratios
• Types of modifier
• Types of diluent
• Effect of degradation products
• Changes in aqueous feed (impurities etc)
A study of copper extraction kinetics with LIX 984N using a Lewis cell
CSIRO upgraded Lewis cell features
Features Original model Upgraded
model
Volume Larger smaller
Interfacial area Variable Variable
VOrg/Vaq ratio Fixed 1:1 Variable
Water jacket Ring seal Built-in
Motors Overlay on top Side
arrangements
Driven
mechanism
Direct
engagement
Belts
Operating Easy Easier
Locating Need for
adjustment
Auto locating
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Acknowledgement
• The financial support of sponsors are greatly appreciated
• Anglo American BHP Billiton
• FLSmidth Freeport McMoRan
• Minara Newmont
• QNI Umicore
• CSIRO MDU Research Flagship
• Funding from
• CSIRO Minerals Down Under National Flagship
• Parker CRC for Integrated Hydrometallurgy Solutions
• MERIWA
A study of copper extraction kinetics with LIX 984N using a Lewis cell
Thank you
National Research Flagship –
Minerals Down Under
Parker Centre/CSIRO Process
Science and Engineering
Dr Wensheng Zhang
Research Team Leader
Phone: +61 8 9334 8029
Email: [email protected]
Web: www.csiro.au/CPSE.html
National Research Flagship –
Minerals Down Under
Parker Centre/CSIRO Process
Science and Engineering
Dr Dave Robinson
Research Program Leader
Phone: +61 8 9334 8913
Email: [email protected]
Web: www.csiro.au/CPSE.html
Contact Us
Phone: 1300 363 400 or +61 3 9545 2176
Email: [email protected] Web: www.csiro.au
Thank you