.i `Amesparents úÊ ¯ ¿ ½( )Üß() 122i 122i 122i

356  Download (0)

Texte intégral

(1)

1

(2)

2

2

(3)

i

. ú æ . Ê

¯ É

¿ áÓ ½J.k

@ , àAÜß@ A K

A mes parents.`

(4)

ii Celui qui commande se d´eprave, celui qui ob´eit se rapetisse. La morale qui naˆıt de la hi´erarchie sociale est forc´ement corrompue.

Elis´´ ee Reclus.

Avoir honte de son immoralit´e : c’est un degr´e sur l’´echelle au bout de laquelle on a honte aussi de sa moralit´e.

Friedrich Nietzsche.

Plus la v´erit´e que tu veux enseigner est abstraite, plus il te faut y amener les sens.

Friedrich Nietzsche.

Ainsi as-tu fait au vase `a Soissons !

Clovis Ier.

ii

(5)

iii

Abstract

The goal of this research is to improve an extractive metallurgy process based on solvent extraction. This process should fit the exploitation of small local copper-rich deposits. In these conditions, the plant has to be as compact as possible in order to be easily transported from one location to a subsequent one. Improved extraction kinetics could ensure a high throughput of the plant despite its compactness. In addition, the extraction reagent should not be damaging for the environnement. On this basis, we propose to use ultrasound-assisted solvent extraction. The main idea is to increase the extraction kinetics by forming an emulsion in place of a dispersion thanks to the intense cavitation produced by ultrasound. The benefit of this method is to improve the copper extraction kinetics by increasing the interfacial surface area and decreasing the width of the diffusion layer. We studied the implementation of an highly branched decanoic acid (known as Versatic- 10®acid) as a copper extraction reagent dispersed in kerosene.

Emulsification is monitored through the Sauter diameter of the organic phase droplets in aqueous phase. This diameter is measured during pulsed and continuous ultrasound irradiation via a static light scattering technique.

The phenomenon of emulsification of our system by ultrasound is effective, and the emulsification process carried out in the pulsed ultrasound mode is at least as efficient as the emulsification obtained under continuous mode.

No improvement of emulsification is observed beyond a threshold time of the ultrasound impulse. This may be attributed to a competition between disruption and coalescence. The use of mechanical stirring combined with pulsed ultrasound allows to control the droplet size distribution.

In presence of ultrasound, the extraction kinetics of Versatic-10 acid is multiplied by a factor ten, and therefore reached a value similar to the ki- netics observed without ultrasound with an industrial extractant such as LIX-860I®(Cognis). Extraction kinetics measurements are carried out by monitoring the copper ion concentration in the aqueous phase with an elec- trochemical cell.

We conclude that ultrasound-assisted emulsification can be implemented under certain conditions. Emulsification is a first step, and the following destabilization step has to be studied. The device using ultrasound-assisted emulsification should be followed by an efficient settling-coalescing device. A possible solution would be to promote emulsion destabilization by increasing the ionic strength with an addition of M gSO4, a salt that is not extracted by the extraction reagent in the considered range of pH.

(6)

iv

Acknowledgements

I would like to thank the following persons (in a random order):

Imane

Marie-Paule Delplancke-Ogletree Jean-Luc Delplancke

Mes parents, Ann & Christian Ma famille, pour leur soutien Thibaut Wattiez (& Alexandra)

Vanessa Gutierrez Mor´an (& S´ebastien Ferez) aka. Pilar aka. Vaness.

On va boire un coup apr`es la d´efense publique ? Paraˆıt que c’est gra- tuit!

Nathalie Nayer & Fabrizio Buttafuoco Jean-S´ebastien Billet aka. JSB

Luc Segers

V´eronique Halloin Benoˆıt Haut Kristin Bartik

Stefan Van Vaerenbergh Frank Dubois

Olivier Monnom Antonio Pagliero

Samuel Fruchter aka. Sam Colin Aughet aka. Colin le Lapin Gilles Wallaert aka. Gillou

Val´erie Spaeth aka. ma blonde (celle de Vanessa, pour ˆetre pr´ecis).

Sha¨ın Ismail akaMaˆıtre-Chat

Aurore De Boom aka. Madame Boum-boum iv

(7)

v Enrico Tam aka. Il dottore

Nico Claessens

Eric Leeuwerck On se souviendra longtemps de l’escalade du portail du cimeti`ere d’Ixelles (de nuit, et ´em´ech´es) afin d’aller d’honorer la tombe d’Elis´ee Reclus...

Aim´ee, Anne, Elisabeth, Fikri, Gauthier, Georges, Jacques & Julien

Mimouna & Yves

ma p’tite soeur H´el`ene & Nico Eliane & Marie-Jeanne

Henri & Robert

Pascal Brochette Sa connaissance des ´emulsions n’a pas de prix.

Marion Sausse & Michel Pierobon Mes conseillers personnels en ce qui concerne LATEX.

Nicolas Bastin & sa DTR-X Curieusement, il a commenc´e par m’expliquer ce qu’il ne fallaitpas faire en moto..

Yamaha La s´ecu rembourse les anti-d´epresseurs, mais pas les motos. In- compr´ehensible...

Tiriana Segato aka. Titi Andr´e, Ren´e & Fabiano

In general The staff ofTIPS,BEAMS.

Le Kaf-kaf Sans quoi je me serai endormi...

Friedrich N. & Arthur S.

Benedictus XVI H´e h´e. Hem...

Les ´etudiants de la SBS-EM

le Fonds Van Buuren It is obvious that my PhD could not have been finished without the help of theFonds Van Buuren. I would like to express all my gratitude to this Fonds, and to Monsieur le Baron Jaumotte.

(8)

vi

vi

(9)

Contents

Abstract . . . iii

Acknowledgements . . . iv

Table of contents . . . vi

Nomenclature . . . xvi

List of tables . . . xxiii

List of figures . . . xxvii

Introduction xxxvii Background of this work . . . xxxvii

General purpose . . . xxxvii

Outline . . . xxxviii

Activities related to this work . . . xxxix

Chilean case study . . . xl Introduction . . . xl Flowsheet . . . xli Mixer-settler . . . xlvii Columns . . . xlviii I Solvent extraction 1 1 Principles 3 1.1 Chemical approach . . . 3

1.2 Extraction reagents . . . 4

1.2.1 Characteristics . . . 4

1.2.2 Extractant classes [1] . . . 5

1.2.3 Mechanisms and kinetics . . . 9

Mechanisms . . . 9

Note about kinetics . . . 10

LIX-860I® . . . 11

Versatic-10®acid . . . 13

1.3 Thermodynamics of extraction . . . 14

1.3.1 Literature . . . 14

1.3.2 Selectivity . . . 14

(10)

CONTENTS viii 1.3.3 Determination of the appropriate value of volumic phase

ratio . . . 16

1.4 Choice of extraction reagents . . . 16

1.5 Diluents . . . 17

Usefulness . . . 17

Usual diluents . . . 18

Choice of the diluent . . . 19

2 Experimental determinations 21 2.1 Equilibrium constant of an extraction system . . . 21

2.1.1 Experimental implementation . . . 22

2.1.2 Results and discussion . . . 23

2.1.3 Apparent value of equilibrium constant and extraction yield . . . 23

2.2 Respective solubilities of organic and aqueous phase . . . 26

2.2.1 Experimental implementation . . . 26

2.2.2 Results and discussion . . . 27

2.3 Conclusions . . . 27

II Emulsions 29 3 Properties of emulsions 31 3.1 Chemical and interfacial properties . . . 31

3.1.1 Composition of the emulsion . . . 31

The nature of the emulsion . . . 32

3.1.2 The HLB concept . . . 32

3.1.3 The Bancroft rule . . . 33

3.1.4 Interfacial tensions . . . 33

3.1.5 Molecular interactions . . . 34

The intermolecular forces . . . 34

Aqueous phase . . . 35

Organic phase . . . 35

Discussion of the different ”water and oil” sys- tems . . . 35

3.1.6 Preferred curvature . . . 39

Preferred curvature[2, 3] . . . 39

3.1.7 Nature of the emulsion – an attempt of synthesis . . . 40

3.1.8 Experimental methods for determining superficial / interfacial tensions values . . . 41

Capillary rising method – Jurin’s law . . . 41

Horizontal Capillary method . . . 41

Falling drop / Stalagmometric method . . . 42

Pendant drop method: Drop Shape Analysis . . 42 viii

(11)

CONTENTS ix

Sessile drop method . . . 43

du No¨uy’s ring method . . . 44

Wilhelmy’s plate method . . . 44

Superficial waves measurement method . . . 44

Bubble pressure method . . . 46

Multiphasic equilibrium method . . . 46

How to determine interfacial tension when su- perficial tensions are known. . . 46

3.2 Electrical properties . . . 48

3.2.1 Conductivity . . . 48

Conductivity and nature of the emulsion . . . . 50

3.2.2 Electrical double layer . . . 51

3.2.3 Zeta potential of the droplets . . . 53

3.2.4 Electrokinetic effects . . . 54

Electrophoresis . . . 56

Electroosmosis . . . 56

Sedimentation potential . . . 56

Streaming potential . . . 58

Emulsions and Electrokinetic effects . . . 58

3.3 Optical properties . . . 59

3.3.1 Scattering and diffraction of a laser beam . . . 61

Scattering from a single particle . . . 61

The Mie theory . . . 63

Rayleigh scattering . . . 64

The Fraunhofer diffraction – forward scattering 65 The geometry optics . . . 66

Scattering from a population of particles . . . . 66

Comparison of the different scattering approx- imations . . . 67

The inverse scattering problem . . . 67

3.3.2 Turbidity . . . 68

Definition and theoretical background . . . 68

Drawbacks of the technique . . . 69

3.3.3 Color . . . 70

Relevance . . . 70

3.4 Experimental determinations . . . 73

3.4.1 Interfacial tensions measurements . . . 73

Experimental . . . 73

Results and discussion . . . 75

Conclusions . . . 80

3.4.2 Conductivity measurements . . . 80

Experimental . . . 80

Results . . . 80

(12)

CONTENTS x

4 Emulsification 83

4.1 Introduction . . . 83

4.2 Thermodynamics of emulsification . . . 83

4.2.1 Interfacial free energy . . . 83

4.2.2 Laplace pressure . . . 84

4.2.3 Viscous dissipation . . . 86

4.3 Kinetics of emulsification . . . 86

4.3.1 Description of mechanisms . . . 86

The formation of droplets . . . 86

Formation of a film . . . 86

Disruption of a liquid cylinder . . . 87

Disruption of a plane interface . . . 87

The disruption of droplets . . . 88

Laminar flow . . . 88

Turbulent flow . . . 88

4.3.2 Characteristic times . . . 89

4.4 Techniques of emulsification . . . 89

4.4.1 Introduction . . . 89

4.4.2 Mechanical stirrers . . . 90

Disperser . . . 90

Principle . . . 90

Implementation . . . 90

Range of droplet sizes . . . 91

Homogeneizer . . . 91

Principle . . . 91

Implementation . . . 91

Range of droplet sizes . . . 93

4.4.3 Static mixers . . . 93

Principle . . . 93

Implementation . . . 93

Range of droplet sizes . . . 93

4.4.4 Phase inversion methods . . . 94

Principle . . . 94

Transitional phase inversion . . . 94

Range of droplet sizes . . . 94

Catastrophic phase inversion . . . 94

Implementation . . . 95

4.4.5 Membrane emulsification . . . 95

Principle . . . 95

Implementation . . . 95

Range of droplet sizes . . . 95

4.4.6 High pressure homogeneizers . . . 95

Principle . . . 95

Implementation . . . 95 x

(13)

CONTENTS xi

Range of droplet sizes . . . 96

4.4.7 Ultrasound . . . 96

Principle . . . 96

Cavitation . . . 96

Definition . . . 96

Mechanism . . . 97

Relation between cavitation and emulsification 98 Types of cavitation . . . 98

Cavitation threshold . . . 99

Relevant parameters of cavitation . . . 100

Energetic criterion . . . 101

Implementation of cavitation . . . 103

Mechanical . . . 103

Electro-mechanical . . . 104

Time-relative parameters . . . 106

Energetic-relative parameters . . . 107

4.5 The interest of pulsed ultrasound . . . 108

4.6 Emulsion quality . . . 112

4.6.1 Introduction . . . 112

4.6.2 Droplets size distribution . . . 112

Review of different parameters characterizing the size distribution . . . 113

The choice of a parameter to monitor . . . 115

4.6.3 Experimental methods for determining droplet size distribution . . . 119

Optical methods . . . 119

Photography and shadowscopy . . . 120

Light scattering . . . 120

Light extinction . . . 121

Phase Doppler Particle Analysis . . . 121

Holography . . . 121

Dynamic methods . . . 122

Settling / Sedimentation . . . 122

Electric mobility analysis . . . 123

4.6.4 Choice of the method . . . 124

4.6.5 Physical stability . . . 124

5 Emulsification experiments 127 5.1 Experimental . . . 127

5.1.1 Measurements of irradiated power by calorimetry . . . 127

5.1.2 Studied system . . . 128

5.1.3 Experimental implementation . . . 129

Continuous mode . . . 129

Pulsed mode . . . 129

(14)

CONTENTS xii

5.2 Results and discussion . . . 132

5.2.1 Effect of time-relative parameters . . . 132

Results for LIX–860I . . . 132

Results for Versatic–10 acid . . . 133

Results for kerosene . . . 135

5.2.2 Effect of injected power . . . 136

5.2.3 Effect of additional mechanical stirring . . . 141

5.3 Conclusions . . . 141

6 Destabilization of emulsions 145 6.1 Processes of destabilization . . . 145

6.2 Emulsion stabilization modes . . . 149

Conclusion . . . 154

6.3 Effect of ionic strength . . . 154

6.3.1 Introduction . . . 154

6.3.2 Evolution of ionic strength during extraction . . . 155

6.3.3 Salt selection . . . 156

6.3.4 Availability of M gSO4 . . . 158

6.3.5 Ionic strength and activity coefficient of M gSO4 . . . 158

6.3.6 Experimental . . . 160

Studied system . . . 160

Measurement procedure . . . 160

Results . . . 161

Discussion . . . 162

Conclusions . . . 163

6.3.7 Conclusions . . . 163

III Combined effects of extraction and emulsification 165 7 Kinetics of extraction 167 7.1 Description of the problematics . . . 168

7.1.1 Extraction and diffusion with stirring . . . 168

System description . . . 168

Mass balance of the system . . . 169

Behavior of the system att= 0 . . . 171

Behavior of the system at time t . . . 171

Analytical solution . . . 172

7.1.2 Limit models . . . 173

Fast reaction . . . 173

Fast diffusion . . . 176

Limit model conclusions . . . 179

7.2 Classical quantification methods . . . 180

7.2.1 Sampling method . . . 180 xii

(15)

CONTENTS xiii

Mechanical stirring . . . 181

Ultrasound stirring . . . 181

7.2.2 Results . . . 181

Mechanical stirring . . . 181

Ultrasound stirring . . . 182

7.2.3 Conclusions . . . 183

7.3 Electrochemical cell measurements . . . 183

7.3.1 Introduction . . . 183

Choice of electrodes . . . 185

7.3.2 Devices . . . 185

Classical cell withAgCl/Ag reference electrode 185 Measurements by concentration cell . . . 187

Liquid junction . . . 188

7.3.3 Experimental implementation . . . 190

7.3.4 Results . . . 194

Results from phase 1 . . . 194

Results from phase 2 . . . 197

7.4 Conclusions . . . 200

IV Comparisons between classical extraction and ultrasounds- assisted extraction 203 8 Classical flowsheet using LIX-860I® 205 8.1 Definition of the problematics and the procedure . . . 205

8.1.1 Foreword . . . 205

8.1.2 Assumptions . . . 205

8.1.3 Model . . . 207

Initial conditions . . . 207

Unknown parameters . . . 208

Resolution . . . 209

8.2 Model robustness . . . 210

8.3 Kinetics . . . 211

Extraction kinetics . . . 211

Settling kinetics . . . 213

8.4 Adaptation to a small plant . . . 213

8.5 Conclusions . . . 214

9 Comparison of proposed flowsheet using LIX-860I or Versatic- 10®acid 215 9.1 Flowsheet determination . . . 215

9.2 Equilibrium model results . . . 215

9.2.1 Initial conditions . . . 215

9.2.2 Results . . . 216

(16)

CONTENTS xiv

9.3 Kinetics . . . 216

Extraction kinetics . . . 216

Settling kinetics . . . 219

9.4 Conclusions . . . 219

V Conclusions 221 Conclusions . . . 223

Possible applications . . . 227

Appendices 228 A Table of extraction reagents 229 B Extraction equilibrium constant determination 233 C Measured values of the densities 235 D Signal analysis of the ultrasounds generator 237 Aim . . . 237

Frequency of the fundamental wave . . . 237

Link between the mean power injected and the irregularities of square wave . . . . 237

Link between duty cycle and ultrasounds horn resonance . . . 241

Repetition rate in pulsed mode . . . 245

E Description of experimental implementation 247 E.1 Analytical devices . . . 247

E.2 Equipment . . . 251

E.3 Emulsification device . . . 251

E.4 Procedure . . . 252

F Measurements of irradiated power by calorimetry 255 G Calculation of the average value and errors of measurements259 H Results of emulsification experiments 261 Results concerning Versatic–10 acid . . . 261

Results concerning kerosene . . . 261

Results concerning the power effect . . . 266 I Calculation of ionic strength and activity coefficients 273 J Results of emulsification and extraction kinetics experiments279

xiv

(17)

CONTENTS xv

K Electrochemistry complements 283

K.1 Polarizability of an electrode . . . 283 K.2 Liquid junction potential . . . 285 L Calculation procedure for the extraction model 287

M List of reagents used in this work 291

N Note about the choice of experimental techniques of analy-

sis 293

Bibliography 295

(18)

NOMENCLATURE xvi

Nomenclature

Roman letters

a capillary constant m

ak,bk functions -

ax activity of x -

a agglomeration/coalescence parameter - A,aq (subscript) refers to the aqueous phase - A alkyl group of a hydroxyoxime -

A constant in Szyszkowski expression mol.L−1

AH Hamaker constant V

b curvature radius m

B constant in Szyszkowski expression -

c speed of light in vacuum m.s−1

ci concentration of i-th species mol.L−1

cs speed of sound m.s−1

Cc correction factor -

Ci initial concentration mol.L−1

Csca scattering cross section m2

CQt constant -

d smaller diameter of the horn m

de,ds shape parameters m

da diameter of the stirrer m

d.c. duty cycle -

D partition coefficient -

D bigger diameter of the horn m

Dae aerodynamic diameter m

Di extraction factor of i-th species -

Di diffusion coefficient L.s−1.m−1

D(r) distribution function -

Dv percentile m

D[x,y] mean diameter of x-th and y-th order m

d[3,2] Sauter diameter m

e charge of the electron C

ebulk (hypothetical) width of bulk phase m

xvi

(19)

NOMENCLATURE xvii

Eb approach to equilibrium -

ECu extraction yield wt.% or mol.%

Eequ equilibrium extraction yield wt.% or mol.%

EG Gibbs elasticity J.m−2

EL liquid junction potential V

Ereal real extraction yield wt.% or mol.%

E0 standard potential V

∆E0 standard potential difference V

→E electric field V.m−1

|−E→0| maximum amplitude of the electric field V.m−1 E perpendicular component of the electric vector V.m−1 Ek parallel component of the electric vector V.m−1

f correction factor -

fj(ri) normalized distribution by number -

F force N

FF Faraday constant C.mol−1

Fn Fresnel number -

g gravity m.s−2

g gain -

ga asymmetry factor -

Gv velocity gradient s−1

∆Gf ormation Gibbs free energy of the formation J.mol−1 of an emulsion

∆Gi,h Gibbs free energy of interaction J.mol−1 of the droplets

h height or width m

H dimensional factor m

∆H enthalpy variation J.mol−1

i summation index -

[i] concentration of i-th species mol.L−1

I ionic strength mol.L−1

I0 initial ionic strength mol.L−1

Iac acoustic intensity W.m−2

Ii initial irradiance W.m−2

Is scattered irradiance W.m−2

Is,T total scattered irradiance W.m−2

It irradiance of transmitted light W.m−2

Ji(x, t) diffusive flux mol.s−1.m−2

(20)

NOMENCLATURE xviii

k emulsion conductivity S

kB Boltzmann constant J.K−1

kc coalescence rate s−1

kcont conductivity of continuous phase S kdisp conductivity of dispersed phase S

kex extraction kinetics constant depends on kinetics law kf agglomeration kinetics constant s−1

kn wave number m−1

kp dimensionless constant -

→k0 wave vector of incident light m−1

→ks wave vector of scattered light m−1 Kd partition equilibrium constant - Kex extraction equilibrium constant - KiH i-th proton dissociation equilibrium constant - Ks solubility equilibrium constant -

→K scattering vector m−1

L distance m

m mass kg

me slope on thelog-lin graph of mol.L−1.V−1 copper sulfate concentration as a function

of potential difference

mn relative complex refractive index - m number of distinct droplets in an aggregate -

M number of items in a sample -

n number of items in a sample -

na number of aggregates -

ne number of electrons implied in a redox - nt number of not agglomerated droplets -

n0 initial number of droplets -

N number of items in a sample -

NA Avogadro number mol−1

NP power number -

NQP pumping number -

Nω rotational speed s−1

O,org (subscript) refers to the organic phase -

xviii

(21)

NOMENCLATURE xix

p pressure Pa

p(b) pressure at the interface P a

pL Laplace pressure P a

p(∞) isotropic pressure in the bulk phase P a

P power W

PP peak power of ultrasound W

Qdisp dispersion flowrate m3.s−1

QEW aqueous electrowinning solution flowrate m3.s−1 QL aqueous leaching solution flowrate m3.s−1

QP flowrate m3.s−1

Qr reaction quotient -

Qs scattering efficiency -

QSX organic phase flowrate m3.s−1

rex extraction rate mol.L−1.s−1

r,ri radius or distance m

r0 radius of an emitting surface m

R gas constant J.mol−1.K−1

R0 radius of cavitation nucleus m

Rc threshold radius of cavitation nucleus m

R,R” curvature radius m

Re Reynolds number -

s salt solubility mol.L−1

sx experimental standard deviation unit ofxi sxm estimator of the standard deviation unit ofxi

S surface area m2

Sint interfacial surface area m2

Ssettler surface of the settler m2

→S Poynting vector W.m−2

|S(ψ, ϕ)| amplitude scattering matrix determinant -

∆Sconf iguration configurational entropy J.mol−1.K−1

∆Sint variation of interfacial surface area m2

t time s

ton,tof f time on and off of the ultrasound generator s

ttotal total time of irradiation s

tx transport number of species x -

T absolute temperature K

(22)

NOMENCLATURE xx u electrochemical mobility of an ion m.s−1.V−1

U mean velocity of a flow m.s−1

Usettling surfacic settling flowrate (velocity) m3.s−1.m−2

→v velocity of a charged particle / droplet m.s−1

vb bulk solution velocity m.s−1

v(Dae) terminal velocity of a particle with m.s−1 an aerodynamic diameterDae

vAk volumic fraction of water in the kerosene phase - vkk volumic fraction of kerosene in the kerosene phase -

V volume m3

VA volume of aqueous phase m3

Vint interfacial volume m3

Vmixer volume of the mixer m3

VO volume of organic phase m3

∆V sedimentation or streaming potential V

w stoechiometric coefficient -

w0 characteristic dimension of laser beam spot size m

W e,W ec Weber number -

W power W

Ws scattered power W

W(r) weighting function -

W1, W2 work J

xi result of i-th measurement -

xm arithmetic mean ofxi unit of xi

x horizontal coordinate m

y vertical coordinate m

z stoechiometric coefficient or valence -

zc cavitation limit ordinate m

zi charge of i-th species -

Z acoustic impedance of the medium kg.m−2.s−1

Zc electric mobility of a particle m2.s.V−1

Z impedance of voltmeter Ω

→1n normal vector -

xx

(23)

NOMENCLATURE xxi Greek letters

α value of t-student probability distribution - αi/j separation factor of i-th and j-th species -

αs dimensionless size parameter -

αd dampening coefficient of the medium m−1

α parameter mol.L−1

absorption coefficient m−1

βnH overall proton dissociation equilibrium constant -

β parameter mol.L−1

χ extinction coefficient m−1

δN width of the diffusive boundary layer m

ǫ permittivity F/m

ǫR relative permittivity -

ε,ε wetting / contact angle rad

ηiA mass proportion of i-th component -

in the phase containing water

ηik mass proportion of i-th component -

in the phase containing kerosene

ηvd dynamic viscosity Pa.s

φ,φ” contact angle rad

ϕ azimuthal angle rad

ϕ(x, t) overall diffusive flux mol.m−2

γ interfacial tension J.m−2

γx activity coefficient of species x -

γ0 interfacial tension without extraction reagent J.m−2 γ interfacial tension if aqueous phase has J.m−2

an infinite extent

Γ surface excess mol.L−1

Γ surface excess when interface is saturated mol.L−1

κ Debye-H¨uckel reciprocal length m−1

λ wavelength m

Λ turbidity m−1

µ0 vacuum permeability H.m−1

νrepetitionrep repetition rate s−1

νi stoechiometric coefficicient -

π mathematical constant pi -

π(h) disjoining pressure P a

πx disjoining pressure contribution due to x P a

ψ scattering angle rad

Ψ potential in the electrical double layer V

Ψ0 Nernst potential V

Ψδ Stern potential V

(24)

NOMENCLATURE xxii ρa relative density of the aqueous phase kg.m−3

ρa relative density of the aqueous phase kg.m−3 ρa relative density of the aqueous phase kg.m−3 ρk relative density of the kerosene phase kg.m−3 ρ0A relative density of deionized water kg.m−3 ρ0k relative density of kerosene kg.m−3 ρliquid relative density of liquid phase kg.m−3 ρvapor relative density of gaseous phase kg.m−3

∆ρ difference of relative densities kg.m−3

σ superficial tension J.m−2

τads characteristic adsorption time s τcol characteristic collision time s τdef characteristic deformation time s

τmixer residence time in the mixer s

τp characteristic pressure time s

τs characteristic interfacial tension time s

τv characteristic viscosity time s

τ1/2 half life of emulsion towards agglomeration s

θ volume phase ratio -

ξ (pseudo) extent of reaction mol.L−1

ξP angle rad

ζ zeta potential V

ω angular frequency rad.s−1

ωM Minneart frequency rad.s−1

xxii

(25)

List of Tables

1 Ores found in different mineralizations of copper deposits.

Notice that denominations of oxide andsulfide are only used for convenience, becausesilicates and carbonates are usually classified in oxide category. . . xliii 1.1 Required characteristics of extraction reagents. . . 5 1.2 Nature, IUPAC name and trade name of some of the second

generation oximes. . . 7 1.3 IUPAC name, trade name and solubilities of Versatic®acids. 10 1.4 Table of parameters related to fire hazards, human toxicity

and ecotoxicity for LIX-860I and Versatic-10 acid. . . 17 1.5 Table of commercially available diluents. . . 19 1.6 Composition of ORFOM SX-12 kerosene [4]. . . 20 2.1 Initial concentrations of species implied in extraction equilib-

rium. . . 22 3.1 Designation and continuous phase. . . 32 3.2 HLB values and desired applications. . . 33 3.3 Table of energies for different intermolecular/interionic forces,

reproduced from [5]. . . 34 3.4 Table showing the four conductivity expressions used, and

their limit when the dispersed phase conductivity tends to- wards zero. . . 50 3.5 Classification of electrokinetics effects according to the cause/effect

relation. Reproduced from [6]. . . 55 3.6 Value ofFn and type of diffraction. . . 65 3.7 Results of superficial tensions measurements on copper sulfate

solutions. . . 75 3.8 Results of superficial tensions measurements on Kerosene –

LIX systems. . . 75 3.9 Results of superficial tensions measurements on Kerosene –

Versatic–10 acid systems. . . 76

(26)

LIST OF TABLES xxiv 3.10 Results of superficial tensions measurements on aqueous phase

put in contact with Kerosene containing Versatic–10 acid or LIX–860I. . . 77 3.11 Results of interfacial tensions measurements on buffered aque-

ous solutions contacted with kerosene containing Versatic–10 acid or LIX–860I. . . 79 5.1 Value of the mean power injected in the medium as a func-

tion of the cursor position. Error on mean power injected is estimated at 2W according to the results of calorymetry experiments presented in Appendix F. . . 128 5.2 Duty cycles and corresponding irradiation times. . . 130 5.3 Experimental parameters and their values used in experi-

ments – LIX-860I. . . 130 5.4 Combination of values of d.c. and νrep used in experiments

for LIX-860I. A ’X’ shows a tested combination of values. . . 130 5.5 Experimental parameters and their values used in experi-

ments – Versatic–10 acid. . . 131 5.6 Combination of values ofd.c.andνrep used in experiments for

Versatic–10 acid. A ’X’ shows a tested combination of values. 131 5.7 d[3;2] obtained for experiments in the case of organic phase

containing kerosene and LIX–860I, stirring provided by the use of ultrasound only, and repetition rate equal to 1.67s−1. . 132 5.8 d[3;2] obtained for experiments in the case of organic phase

containing kerosene and LIX–860I, stirring provided by the use of ultrasound and mechanical means, and repetition rate equal to 1.67s−1. . . 132 5.9 d[3;2] obtained for experiments in the case of organic phase

containing kerosene and Versatic–10 acid (15 %vol), stirring provided by the use of ultrasounds only, and repetition rate equal to 0.17s−1. . . 134 5.10 d[3;2] obtained for experiments in the case of organic phase

containing kerosene only, stirring provided by the use of ul- trasounds only, and repetition rate equal to 0.17s−1. . . 136 5.11 Comparison of d[3;2] plateau values obtained for experiments

with organic phase containing either LIX–860I or Versatic–10 acid, or kerosene only, stirring provided by the use of ultra- sounds only. . . 137 5.12 Values of mean power averaged on time related to the values

of duty cycle & power peak. . . 137 5.13 d[3;2] obtained for experiments in the case of organic phase

containing Versatic–10 acid, stirring provided by the use of ultrasound only. . . 139 5.14 d[3;2] values obtained in plateau for experiments. . . 139

xxiv

(27)

LIST OF TABLES xxv 6.1 Initial concentrations of aqueous species in our extraction sys-

tem. . . 156 6.2 Table of common sulfate salts – Solubility is given in water

at 25‰. . . 157 6.3 Table of soluble magnesium mineral usually encountered [7, 8].159 6.4 Table of values ofM gSO4 concentrations used in the experi-

ments, and the related values of ionic strength. . . 161 6.5 Table of values of d[3; 2] (and error) obtained for different

values of ionic strength. . . 161 7.1 Reduction potential of the AgCl/Ag electrode for various

temperatures, for saturatedKCl and 3.5mol.L−1 KCl. Re- produced from [9]. . . 187 7.2 Values of concentrations of copper sulfate solutions we used

in our experiments. . . 190 7.3 Values of parameters used in emulsification experiments with

LIX-860I. . . 191 7.4 Values of parameters used in emulsification experiments with

Versatic-10 acid. . . 192 7.5 Potential difference measured between the electrodes of se-

tups 1, 2 and 3 as a function of copper ion concentration in measurement cell solution – comparison with values of Nernst’s related expression of potential – calculation led with the activities. . . 195 7.6 Potential difference measured between the electrodes of se-

tups 4 and 5 as a function of copper ion concentration in mea- surement cell solution - comparison with values of Nernst’s related expression of potential – calculation led with activities.197 7.7 Comparison of initial extraction rates obtained for LIX-860I

and Versatic-10 acid with mechanical or ultrasound stirring. . 199 8.1 Initial conditions of our model. . . 209 8.2 Comparison of values characteristic of Quebrada Blanca op-

eration and calculated values using model. . . 210 B.1 Results of extraction equilibrium constant determination. . . 233 D.1 Value of the correction for the mean power irradiated in the

system as a consequence of the rise and drop times of tension impulsion, as a function of impulsion times. . . 243 E.1 Copper emission spectral lines used in ICP-OES measure-

ments – in aqueous phase. . . 248 E.2 Copper emission spectral lines used in ICP-OES measure-

ments – in organic phase. . . 248

(28)

LIST OF TABLES xxvi E.3 Important parameters of the density meter. . . 249 E.4 Linear correlation between power and cursor position. . . 252 F.1 Value of the mean power injected in the medium as a function

of the cursor position. . . 257 G.1 Values of thet-distribution parameter as a function of sample

size nand confidence interval. . . 260 H.1 d[3;2] obtained for experiments in the case of organic phase

containing kerosene and Versatic–10 acid, stirring provided by the use of ultrasounds only, and repetition rate equal to 0.17s−1. . . 261 H.2 d[3;2] obtained for experiments in the case of organic phase

containing kerosene and Versatic–10 acid, stirring provided by the use of ultrasounds only, and repetition rate equal to 1.67s−1. . . 262 H.3 d[3;2] obtained for experiments in the case of organic phase

containing kerosene and Versatic–10 acid, stirring provided by the use of ultrasounds only, and repetition rate equal to 16.7s−1. . . 262 H.4 d[3;2] obtained for experiments in the case of organic phase

containing kerosene and Versatic–10 acid, stirring provided by the use of ultrasounds and mechanical means, and repetition rate equal to 0.17s−1. . . 262 H.5 d[3;2] obtained for experiments in the case of organic phase

containing kerosene and Versatic–10 acid, stirring provided by the use of ultrasounds and mechanical means, and repetition rate equal to 1.67s−1. . . 263 H.6 d[3;2] obtained for experiments in the case of organic phase

containing kerosene and Versatic–10 acid, stirring provided by the use of ultrasounds and mechanical means, and repetition rate equal to 16.7s−1. . . 263 H.7 d[3;2] obtained for experiments in the case of organic phase

containing kerosene only, stirring provided by the use of ul- trasounds only, and repetition rate equal to 0.17s−1. . . 263 H.8 d[3;2] obtained for experiments in the case of organic phase

containing kerosene only, stirring provided by the use of ul- trasounds only, and repetition rate equal to 1.67s−1. . . 264 H.9 d[3;2] obtained for experiments in the case of organic phase

containing kerosene only, stirring provided by the use of ul- trasounds only, and repetition rate equal to 16.7s−1. . . 264

xxvi

(29)

LIST OF TABLES xxvii H.10 d[3;2] obtained for experiments in the case of organic phase

containing kerosene only, stirring provided by the use of ul- trasounds and mechanical means, and repetition rate equal to 0.17s−1. . . 264 H.11 d[3;2] obtained for experiments in the case of organic phase

containing kerosene only, stirring provided by the use of ul- trasounds and mechanical means, and repetition rate equal to 1.67s−1. . . 265 H.12 d[3;2] obtained for experiments in the case of organic phase

containing kerosene only, stirring provided by the use of ul- trasounds and mechanical means, and repetition rate equal to 16.7s−1. . . 265 H.13 d[3;2] obtained for experiments in the case of organic phase

containing Versatic–10 acid, stirring provided by the use of ultrasounds only. . . 266 H.14 d[3;2] obtained for experiments in the case of organic phase

containing Versatic–10 acid, stirring provided by the use of ultrasounds and mechanical means. . . 267 H.15 d[3;2] obtained for experiments in the case of organic phase

containing kerosene only, stirring provided by the use of ul- trasounds only. . . 268 H.16 d[3;2] obtained for experiments in the case of organic phase

containing kerosene only, stirring provided by the use of ul- trasounds and mechanical means. . . 269 I.1 Ionic strength for different values of M gSO4 analytical con-

centration –Iestimatedis the ionic strength calculated without the effect of activities, andIcorrectedtakes into account the ef- fect of activities. . . 276 J.1 Extraction reagents used, stirring power used, measured cop-

per ion concentrations before and after sampling, and calcu- lated initial extraction rates. . . 280

(30)

LIST OF TABLES xxviii

xxviii

(31)

List of Figures

1 Flowsheet ofQuebrada Blanca hydrometallurgical plant. . . . xlii 2 Picture of a sample of dispersion of aqueous and organic

phases which was withdrawn from amixer/settler device from Quebrada Blanca plant. . . xliv 3 Picture of a row of copper cathodes being recovered from

electrolytic cell, in thecopper electrowinning hall of Quebrada Blanca plant. . . xlvi 4 Sketch of a mixer-settler device. Reproduced from [10]. . . xlvii 5 Sketch of packed and pulse columns. Reproduced from [1]. . . xlix 6 Sketch of rotating disks column. Reproduced from [1]. . . xlix 1.1 Extraction curve of copper ions by Versatic-10®acid and

other extractants [11]. . . 4 1.2 Chemical structure of the active compound of second gener-

ation hydroxyoxime reagents. . . 6 1.3 Chemical structure of the active compound of LIX-63®. . . . 7 1.4 Chemical structure of the active compound of LIX-6x®series. 8 1.5 Overview of hydroxyoximes classification. . . 8 1.6 Chemical structure of the active compound of Versatic-10®acid.

The sum of the numbers of carbon atoms in Rand R equals eight. . . 9 1.7 Steps occuring during extraction in dispersion. . . 10 1.8 Extraction curves of metallic ions by salycilaldoxime. Repro-

duced from [12]. . . 15 2.1 Extraction isotherm of copper ion by LIX–860I – Initial pH

2.0 ; copper ion initial concentration 0.087mol.L−1 ; Extrac- tion reagent initial concentration 0.45mol.L−1 – Ultrasound power is set at 14.9W – Mechanical stirrer power is set at 12.2W. . . 24

(32)

LIST OF FIGURES xxx 2.2 Evolution of the extraction yieldECu as a function of θ. Ini-

tial pH 2.0 ; copper ion initial concentration 0.087mol.L−1 ; Extraction reagent initial concentration 0.45mol.L−1 – Ultra- sound power is set at 14.9W – Mechanical stirrer power is set at 12.2W andT = 293K . . . 25 3.1 Formula of LIX–860I® . . . 35 3.2 Formula of Versatic–10® acid . . . 35 3.3 Water/dodecane system. . . 36 3.4 Water/dodecane containing LIX–860I system. . . 37 3.5 Dodecane/air containing LIX–860I system. . . 38 3.6 Air/water containing aqueous emulsifier system. . . 39 3.7 Stronger interactions on the water side . . . 39 3.8 Equal interactions on both sides . . . 40 3.9 Stronger interactions on the oil side . . . 40 3.10 Principle of the horizontal capillary method, taken from [13] . 42 3.11 Profile of a pendant droplet, taken from [13] . . . 43 3.12 Profile of a sessile droplet on a plate, taken from [13] . . . 44 3.13 du No¨uy’s ring technique, taken from [13] . . . 45 3.14 Wilhelmy’s plate technique, taken from [13] . . . 45 3.15 Diagram of two liquids phases in contact with a solid phase . 47 3.16 Sessile drop measurements for kerosene . . . 47 3.17 Sessile drop measurements for water . . . 48 3.18 Calculated emulsion conductivity (in mS/cm) as a function

of volumic fraction θ when kdisp → 0, with different models.

A value of conductivity of water has been measured and used askcont = (6±1)×10−3 mS/cmfor establishing this curve. . 51 3.19 Sketch of an electrical double layer with counter-ion adsorption. 52 3.20 Sketch of potential behavior in the electrical double layer with

counter-ion adsorption. . . 53 3.21 Sketch of potential behavior in the electrical double layer with

counter-ion adsorption and charge reversal. . . 54 3.22 Sketch of an electronegative particle and its plane of shear in

an electrolyte solution. Water molecules are not depicted. . . 55 3.23 Principle of electrophoresis, with droplets negatively charged. 57 3.24 Principle of sedimentation potential, with droplets negatively

charged in the field of gravity. . . 57 3.25 Scattering geometry, taken from [14] . . . 63 3.26 Two-dimensional scattering intensity pattern for Mie scatter-

ing, taken from [15]. . . 64 3.27 Sketch of an online turbidimetry device, taken from [16]. . . . 70 3.28 Figure showing the evolution of the superficial tension of cop-

per sulphate solution as a function of copper sulphate concen- tration. . . 76

xxx

(33)

LIST OF FIGURES xxxi 3.29 Figure showing the evolution of the superficial tension of or-

ganic phase as a function of volumic percentage of extraction reagent. . . 77 3.30 Figure showing the evolution of the superficial tension of wa-

ter contacted with Kerosene containing Versatic–10 acid / LIX–860I. . . 78 3.31 Figure showing the evolution of the interfacial tension of buffered

aqueous solutions contacted with kerosene containing Versatic–

10 acid / LIX–860I. . . 79 3.32 Comparison between calculated and measured emulsion con-

ductivities (in mS/cm) as a function of volumic fraction θ when kdisp → 0, with different models. A value of con- ductivity of water has been measured and used as kcont = (6±1)×10−3 mS/cm to establish the theoretical curves. . . 82 4.1 General principle of emulsification process . . . 84 4.2 Small section of a curved surface displaced from equilibrium. 85 4.3 W ec as a function of ηηd

v for simple shearing case – Continuous curve corresponds to a static mixer, and dots to a colloidal mill [17]. . . 88 4.4 Principle of a rotor-stator device, reproduced from [18]. . . . 92 4.5 Principle of a colloidal mill, reproduced from [18]. . . 92 4.6 Principle of an homogeneizer batch tank, reproduced from [19]. 93 4.7 Principle of a transitional phase inversion method, taken from

[18]. . . 94 4.8 Depiction of boiling and cavitation on a schematic phase di-

agram (of water). . . 97 4.9 Hydrostatic pressure as a function of the bubble nucleus ra-

dius – Representation for two initial nucleus radii – Repro- duced from [20]. . . 99 4.10 Depiction of the cavitation threshold when applying acoustic

field to system. . . 101 4.11 Zone of the system where cavitation threshold is reached. . . 103 4.12 Whistle device principle. . . 104 4.13 Geometry and construction of our ultrasound horn. . . 105 4.14 Picture of widespread ultrasound horns, reproduced from [21]. 106 4.15 Power injected in the medium irradiated by pulsed ultrasound

as a function of time. . . 107 4.16 Schematic comparison of τrad and τdef, and related events. . . 110 4.17 Schematic comparison of τads and τcol, and related events. . . 111 4.18 Situation is favorable in pulsed mode. . . 111 4.19 Situation is unfavorable in continuous mode. . . 112 4.20 Example of simple volumic percentage distribution. . . 114 4.21 Number distribution barchart for two droplet populations. . . 116

(34)

LIST OF FIGURES xxxii 4.22 Comparison of the interfacial surface areas of the two popu-

lations . . . 117 4.23 Comparison of the volumic distribution of the two populations 118 4.24 Value of the different parameters for the two droplets popu-

lations. . . 118 4.25 Diagram of Light Scattering techniques implementation. . . . 120 4.26 Principle of the recording of an hologram . . . 122 4.27 Settling chamber with aerosol and air intake – depiction of

the particle sorting by settling. . . 123 5.1 d[3;2] as a function of ton. Organic phase is kerosene con-

taining LIX–860I (15%vol), and stirring is provided either by ultrasound only, or ultrasound and additional mechanical stirring. . . 133 5.2 d[3;2] as a function ofton. Organic phase is kerosene contain-

ing Versatic–10 acid (15 %vol), and stirring is provided by either ultrasounds or ultrasound and additional mechanical stirrer. Legend shows values (in %) of varying duty cycle – horizontal lines show d[3;2] for continuous ultrasound for each case. . . 135 5.3 d[3;2] as a function of ton. Organic phase is kerosene, and

stirring is provided by ultrasound only. Legend depicts the values of mean power related to duty cycle values. . . 138 5.4 d[3;2] as a function of duty cycle. Organic phase is kerosene,

and stirring is provided by ultrasound only. Only the data corresponding to the plateau values of Figure 5.3 have been considered. . . 140 5.5 d[3;2] value in plateau as a function of injected power. Or-

ganic phase is kerosene containing Versatic–10 acid or kerosene only, and stirring is provided by ultrasound only or ultrasound and mechanical stirrer. . . 141 5.6 Plateau value of d[3;2] as a function of injected power and the

stirring mode. Organic phase is kerosene containing Versatic–

10 acid (10%vol). . . 142 5.7 Synoptic overview of the effect of the parameters on the d[3,2]

evolution in our system. Mean PU S represents the mean power averaged on time, PU S represents the injected power, tonrepresents the time of the ultrasound impulsion,Versatic- 10 acid represents the presence of this extraction reagent, and Mech. stirring represents the presence of additional mechanical stirring. . . 143 6.1 Film of continuous phaseβ between droplets of phaseα. . . . 147

xxxii

(35)

LIST OF FIGURES xxxiii 6.2 Sketch of potential behavior in electrical double layer with

counter-ion adsorption. . . 151 6.3 Sketch of equilibrium position of a solid particle at the inter-

face between dispersed and continuous phases. . . 151 6.4 Sketch of different positions of a solid particle in a dispersed

system. . . 152 6.5 Geometry of a solid particle at the interface between dispersed

and continuous phases. . . 153 6.6 Evolution of ionic strength of M gSO4 solution as a function

of CM gSO4. . . 160 6.7 Evolution of ofd[3; 2] as a function of time and ionic strength

– ”IS” means ionic strength in the graph. . . 162 7.1 Depiction of the system whent= 0. . . 171 7.2 Depiction of the system for a timet. . . 172 7.3 Depiction of the system in fast reaction case for a time t. . . 174 7.4 Depiction of the system kinetics: concentration logarithm as

a function of time. . . 176 7.5 Depiction of the system in fast diffusion case for a time t. . . 177 7.6 Description of the evolution of the apparent extraction rate

∂[Cu2+]bulk

∂t as a function of the interfacial surface area. . . 180 7.7 Evolution of the apparent extraction rate ∂[Cu2+∂t]bulk as a func-

tion the stirring power. . . 182 7.8 Setup of a classical cell with AgCl/Ag reference electrode

measurement device. . . 186 7.9 Setup of a concentration cell measurement device. Copper

wire is usual electrical conductor. Liquid junction was car- ried out by using eitherKClorK2SO4 in gelified agar-agar.

Temperature was 293KandpH = 4.1. Copper ion concentra- tionsxwere made varying between 10−4and 8×10−2 mol.L−1 during test phase of the electrochemical cell. . . 189 7.10 Setup of a AgCl/Ag wire plunged in the measurement cell.

Copper wire is usual electrical conductor. Temperature was 293K and pH= 4.1. Copper ion concentrationsxwere made varying between 10−4 and 8×10−2mol.L−1 during test phase of the electrochemical cell. . . 193 7.11 Setup of a AgCl/Ag reference electrode with double liquid

junction. Copper wire is usual electrical conductor. Temper- ature was 293K and pH = 4.1. Copper ion concentrations x were made varying between 10−4 and 8×10−2 mol.L−1 during test phase of the electrochemical cell. . . 194

(36)

LIST OF FIGURES xxxiv 7.12 Potential difference measured between the electrodes in our

system as a function of copper ion concentration in the mea- surement cell solution - comparison with values of Nernst’s related expression of potential. . . 196 7.13 Potential difference measured between the electrodes in our

system as a function of copper ion concentration in measure- ment cell solution - comparison with values of Nernst’s related expression of potential. . . 198 7.14 Evolution of the copper ion concentration as a function of

time for LIX-860I emulsification and extraction kinetics ex- periments. Comparison of mechanical and ultrasound stirring. 199 7.15 Evolution of the copper ion concentration as a function of

time for Versatic-10 acid emulsification and extraction kinet- ics experiments. Comparison of mechanical and ultrasound stirring. . . 200 7.16 Evolution of the copper ion concentration as a function of

time for Versatic-10 acid emulsification and extraction kinet- ics experiments. Effect of extraction reagent volume percentage.201 8.1 Diagram of stagewise extraction atQuebrada Blancahydromet-

allurgical plant –θis the volume phase ratio in the considered extraction or stripping stage. . . 206 8.2 Diagram of single stage extraction using LIX-860I. . . 208 8.3 (a) Effect of varyingCRH onθ1. (b) Effect of varyingKex on

θ1. . . 212 9.1 Spreadsheet used to resolve the model in case of Versatic-10

acid. CR2H2 = 0.3mol.L−1 . . . 217 9.2 Spreadsheet used to resolve the model in case of Versatic-10

acid with an analytical concentration of 0.8mol.L−1. . . 218 9.3 Sketch of a possible ultrasound extraction reactor based on

existing cascade continuous stirred-tank reactors. . . 219 A.1 Overview of extraction reagents specific for copper. . . 230 A.2 Overview of extraction reagents specific for copper - continued.231 A.3 Overview of extraction reagents specific for copper - continued.232 C.1 Densities measured prior to interfacial tension measurements. 236 D.1 Graph of alternate tension supplied to to the ultrasounds horn

as a function of time, in continuous mode. . . 238 D.2 Fourier’s transform of the signal supplied to the horn in con-

tinuous mode. . . 238 D.3 Fourier’s transform of the signal supplied to the horn in pulsed

mode. . . 239 xxxiv

(37)

LIST OF FIGURES xxxv D.4 Square wave supplied by the generator to the ultrasounds

horn when the device use pulsed mode. Repetition rate is equal to 1.67Hz and duty cycle is equal to 50 %. . . 239 D.5 Square wave supplied by the generator linked to the ultra-

sounds horn when the device use pulsed mode. Repetition rate is equal to 1.67Hz and duty cycle is equal to 50 %. . . . 240 D.6 Square wave supplied by the generator without link to the ul-

trasounds horn when the device use pulsed mode. Repetition rate is equal to 1.67Hz and duty cycle is equal to 50 %. . . . 241 D.7 Behavior of the tension supplied to the ultrasounds horn when

triggered. . . 242 D.8 Behavior of the tension supplied to the ultrasounds horn when

triggered. . . 242 D.9 Square wave supplied by the generator to the ultrasounds

horn when the device use pulsed mode. Repetition rate is equal to 1.67Hz and duty cycle is equal to 16.7%. . . 243 D.10 Square wave supplied by the generator to the ultrasounds

horn when the device use pulsed mode. Repetition rate is equal to 1.67Hz and duty cycle is equal to 16.7%. Timescale redimensioned. . . 244 E.1 DSA15 device used for superficial and interfacial tension mea-

surements. . . 249 E.2 Sketch of setup used for interfacial tension measurement. . . . 250 E.3 Mastersizer – S Long bench from Malvern instruments. The

figure depicts: (1) the optical unit – (2) a sample preparation accessory – (3) the computer. . . 251 E.4 Geometry and construction of our ultrasound horn. . . 253 E.5 Overview of the full setup used in our experiments. . . 253 F.1 Evolution of the instantaneous power and mean power in-

jected by the ultrasounds generator as a function of time.

Cursor position equals 9. . . 257 F.2 Evolution of the mean injected power as a function of time

for different positions of the cursor. . . 258 F.3 Mean injected power as a function of time and position of the

cursor – t = 1000 s. . . 258 H.1 d[3;2] as a function of ton. Organic phase is kerosene only,

and stirring is provided by ultrasounds only. Legend shows values (in %) of varying duty cycle. . . . 267 H.2 d[3;2] as a function ofton. Organic phase is kerosene only, and

stirring is provided by ultrasounds and additional mechanical stirrer. Legend shows values (in %) of varying duty cycle. . . 268

(38)

LIST OF FIGURES xxxvi H.3 d[3;2] as a function of of ton. Organic phase is kerosene, and

stirring is provided by ultrasound only. . . 269 H.4 d[3;2] as a function of of ton. Organic phase is kerosene, and

stirring is provided by ultrasound and additional mechanical stirrer. . . 270 H.5 d[3;2] as a function of of ton. Organic phase is kerosene con-

taining Versatic–10 acid, and stirring is provided by ultra- sound only. . . 270 H.6 d[3;2] as a function of of ton. Organic phase is kerosene con-

taining Versatic–10 acid, and stirring is provided by ultra- sound and additional mechanical stirrer. . . 271 I.1 Evolution of log(γM g2+) as a function of log(I). . . 275 I.2 Evolution of log(γSO2−

4 ) as a function of log(I). . . 275 I.3 Evolution of log(γM gSO4) as a function of log(I). . . 276 I.4 Evolution of ionic strength of M gSO4 solution as a function

ofCM gSO4. . . 277 J.1 Results obtained for LIX-860I emulsification and extraction

kinetics experiments. . . 280 J.2 Results obtained for Versatic-10 acid emulsification and ex-

traction kinetics experiments. . . 281 K.1 Evolution of the electrode potential as a function the net cur-

rent density for apolarizable electrode. . . 284 K.2 Evolution of the electrode potential as a function the net cur-

rent density for anon polarizable electrode. . . 284 L.1 Diagram of single stage extraction. . . 287

xxxvi

(39)

Introduction

Background of this work

T

his work takes part in a project led in collaboration with the chilean universities Universidad de Concepci´on (located in Concepci´on) and Universidad Arturo Prat (located in Iquique), and belgian universities Uni- versit´e de Li`ege and Universit´e Libre de Bruxelles. This project aims at developing and designing new extractive metallurgy processes, which would be suited to local exploitation of small copper ore deposits. In these con- ditions, the plant has to be as compact as possible in order to be easily transported from a deposit to a subsequent one.

In Chile, mostly large but less concentrated deposits are already ex- ploited by industrial installations. Few small copper ore deposits are mined, and the ore is sent with difficulty to the large industrial installations. These installations exhibit a conventional flowsheet which uses leaching (usually heap leaching), solvent extraction (usually multi-stage) and electrowinning.

The required infrastructure and the amount of metal immobilized may be large, in order to ensure high recovery yield and productivity. Massive in- stallations require high capital and operating costs, and are meaningful only if the deposit is large enough to be exploited according a suited paying off timespan. This excludes this kind of installations to exploit small deposits which give no guarantee of such paying off timespan. The exploitation of these small deposits would then require smaller installations and benefit by new technology, in order to limit residence time of the metal and maintain productivity. These installations should also exhibit modularity, in order to ease their transport and deployment on the field.

The present PhD concerns the determination of the relevance of a par- ticular solvent extraction technique, and its possible implementation in in- dustry.

Some of the objectives of the aforementioned project have already been realized thanks to collaborations between Universit´e de Li`ege, Universidad de Atacama (located in Copiap´o) and Universidad Arturo Prat (located in Iquique) on one hand, and collaborations between Universidad de Con- cepci´on (located in Concepci´on) and Universit´e Libre de Bruxelles, on the other hand.

(40)

CHAPTER 0. INTRODUCTION xxxviii

General purpose

The aim of this work is to apply ultrasound-assisted emulsification to solvent extraction process. The usefulness of solvent extraction is to concentrate and purify a flow of aqueous solution loaded in metallic cation. This aqueous solution usually comes from leaching process. The metal may then be extracted from aqueous solution by electrowinning or precipitation. This process of concentration and purification may be realized by the dispersion of an organic phase containing an appropriate extraction reagent in aqueous phase. This step is prior to transfer from aqueous phase to organic phase thanks to the complexing effect of extraction reagent.

The net flowrate of cation is influenced by transfer kinetics and by in- terfacial surface area existing between aqueous and organic phases. It is then profitable to increase the interfacial surface area in the perspective of increasing the productivity of the installation. This approach seems to be legitimate, because literature shows that copper ion is usually extracted at the interface rather than in the bulk [22]. This has to be verified in our particular case.

The increase of interfacial surface area may be realized by the use of an emulsion. It is then required to assess the effects of using an emulsion in place of an usual dispersion. We will therefore consider the theories related to emulsions and dispersions, and confront them with experimental study. On the other hand, we will study the use of ultrasound to realize the emulsions. The aim of this work is also to determine the opportunity of using ultrasound as an emulsification way.

We summarize this general purpose by four main questions. The method- ology developped in this work aims at answering to these questions:

1. Is it possible to implement Versatic-10 acid as an extraction reagent ? 2. Is it possible to perform effective emulsification by ultrasound ? 3. Does the implementation of Versatic-10 acid to ultrasound emulsifica-

tion ensures high extraction kinetics ?

4. Is it possible to consider the industrial implementation of a small ex- traction plant using Versatic-10 acid ?

Outline

This dissertation has been divided in five parts.

Part I – Solvent extractionThis part gives a literature review regarding solvent extraction state of the art, and useful experimental predeter- minations.

xxxviii

(41)

CHAPTER 0. INTRODUCTION xxxix Part II – Emulsions This part first gives a literature review regarding emulsions properties, mechanisms of emulsification and derived tech- niques of emulsification, and emulsion destabilization. Then the re- lated experimental work is described.

Part III – Combined effects of extraction and emulsification This part treats the problematics of extraction kinetics in emulsion, by es- tablishing a theoretical framework, and describing the related exper- imental work. Solutions for concentration measurement in emulsion are given.

Part IV – Comparisons between classical extraction and extrac- tion by ultrasound-assisted emulsificationThis part gives a com- parison of a classical flowsheet using LIX-860I and a proposed flow- sheet using Versatic-10 acid. For this purpose, we established a model which takes into consideration equilibrium and kinetics aspects.

Part V – Conclusions This part concerns the general conclusions to the problematics we treated.

Activities related to this work

This work gave us the chance to realize different activities and to discover new places. The following list presents the most relevant.

July-August 2004 Research stay in Republic of Chile, concerning extractive metallurgy of copper, in the framework of a bilateral co- operation agreement between the Republic of Chile and Belgium, re- searches. Financed by the C.G.R.I. (General Commissionership of International Relationships).

April 2006 Seminar in Per´u (given in Spanish) concerning copper solvent extraction, in the Pontificia Universidad Cat´olica del Per´u, and in the copper extraction plant operated by Southern Per´u (in Toquepala and ´Ilo).

October 2006 Attendance at Congr`es Mondial de l’´Emulsion 2006 (Lyon).

October 2006 Attendance attutorial courses on emulsions, organized by the ´Ecole Sup´erieure de Chimie Physique ´Electronique de Lyon.

May 2009 Participation to ALTA 2009 Copper conference in Perth, Australia. Presentation titled ’Copper solvent extraction by ultrasound- assisted emulsification’.

Figure

Updating...

Références

Updating...

Sujets connexes :