A study of copper extraction kinetics with LIX … study of copper extraction kinetics with LIX 984N using a Lewis cell Presented by Wensheng Zhang 8 July 2011 by Wensheng Zhang, Fuping

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

http://www.hydrocopper.cl/evento2011/index.php?lang=en

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


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



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/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


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



Techniques 3 – Lewis cell

• Features;

• Constant interfacial area

• Hydrodynamics well controlled

• Hydrodynamic calibration feasible

• Disadvantages;

• Difficult to maintain stable

interface under turbulent flows


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



CSIRO Lewis cell set-up for kinetic study


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




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


At 20°C and pH 1.8 with 10% LIX 984N in Shellsol D70


Extraction regimes

• Lower speeds – Zone A

• Laminar or less turbulent


• Diffusion regime

• Higher speeds – Zone B

• Turbulent flow


• Kinetic regime

• Zone C - even higher speed

• Disturbance of interface

• Varying interfacial area


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


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


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)




Derived rate equations

• Derived rate equation

• Applying Langmuir isotherms for adsorption

Where and are Langmuir constants


]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


][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




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)




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



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




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



Documents

A study of copper extraction kinetics with LIX … study of copper extraction kinetics with LIX 984N using a Lewis cell Presented by Wensheng Zhang 8 July 2011 by Wensheng Zhang, Fuping