High chloride in PLS and their impact on Copper solvent extractionCristobal del Río, Leonor Ardiles and Héctor Yañez, both BASF Chile S.A.

Agenda

• Introduction• Industrial SX experience with chloride in PLS• Experimental plan• Results and discussion• Conclusions and recommendations

Introduction• Due to water scarcity the use of seawater in Hydrometallurgical operations is

increasing• Also the lower copper grades and the complexity of coppers ores are pushing the

development of new leaching technologies. At present leach technologies usingchloride salt addition are increasing into the industry

• More process into the next future will have PLS with high Chloride• One of the challenges to the downstream process, solvent extraction and

electrowinning is related to the control of the chloride transfer from leachsolutions to electrowinning solutions (electrolyte)

• There are some experience into the industry about the control of the chloridetransfer to the electrolyte

• However the behavior of the solvent extraction chemical equilibrium has not beenintensively studied for mixed chloride and sulfate media.

• A laboratory study involving PLS with chloride and sulfate using BASF’s copperorganic extraction reagent was conducted and these results discussed

Copper OximesChemical behavior of Oximes in Sulphate Media (Source: Redbook BASF Mining Solutions)

Property Ketoxime Aldoxime Non-modified

blend Modified aldoxime

Extractive Strength Moderate Very strong Customized Customized

Stripping Very good Poor Customized Customized

Cu/Fe selectivity Excellent Excellent Excellent Excellent

Extraction kinetics Very good Very fast Fast Very fast

pH

Cu in

Org

anic

, gpl

Strong Moderate

Ald Ket/Ald Ket

RipiosAcido

Agua Evap Acido CátodosAgua Reposicion Agua Reposicion Aditivos

Mineral Purga Elec.

AditivosER Agua Lav W

PLS RF AguaRF E2 Acido

E-1 E-2 S-1 S-2 WOD S1 OC Lav

OC E1

Colescedores TK Org Carg

Purga Acuosoa circuito LX

Lixiviacion Electrobtencion

Process diagram with Chloride in PLS

Industrial SX with chloride in PLS

The use of wash stage, one or two, are the most common alternative to control of chloride transfer to the electrolyte

Operation [Cl-] PLS, g/L [Cl-] LE, ppm Configuration Coalescers, n° Wash stage, n° Reagent

A 80 20-50 SPT 1 1 LIX®9790N

B 80 20-50 SPT 1 1 LIX®9790N

C 10 50 Serie 0 0 LIX®984N

D 30 30-40 Serie 0 1 LIX®84I-C

E 50 10-30 Serie 0 2 LIX®9790N

F 90 20-45 Serie SX 1 /SP SX 2 0 2 LIX®84I-C / LIX®860N-C

G 30 20-30 Serie 0 1 LIX®84I-C

H 35-40 <20 Doble Serie // 0 2 LIX®984N

I 45-90 <25 Doble Serie // 0 2 LIX®84I-C / LIX®860N-C

J 5-7 30-40 Serie 0 1 LIX®84I-C / LIX®860N-C

Experimental planPregnant leach solutions (PLS) conditions

Solution PLS Cl- g/L SO42- g/L pH

PLS 1 A1 0 95 1,0 PLS 2 A2 0 95 1,5 PLS 3 B1 20 95 1,0 PLS 4 B2 20 95 1,5 PLS 5 C1 40 95 1,0 PLS 6 C2 40 95 1,5 PLS 7 D1 90 95 1,0 PLS 8 D2 90 95 1,5

PLS was prepared in the laboratory, with component concentrations (Al+3, Mg+2, Fe+3,Fe+2, Mn+2) adjusted to average conditions in Chilean operations (95 g SO4

-2/L).Chloride concentrations of 0, 20, 40 and 90 g/L were studied. Solutions were adjustedby NaCl addition. Other cations were added as sulfate salts. In addition, the pH wasadjusted to 1.5 and 1.0 by H2SO4 addition. Lean electrolyte: 35 g/L Cu and 180 g/L acidOrganic phase was prepared at 24% v/v with diluent and BASF extractants were basedon Ketoxime (LIX®84I) and Modified Aldoxime (LIX®684N-LV).

Standard parameters of performanceThe standard parameters to be analyzed are Extraction and Strip isotherms, whichgive us the metallurgical performance approach and the Extraction kinetic tests tohave an approach to the industrial mixing efficiency expected. Isotherms andkinetics tests were determined for each PLS solution contacted with the organicsolution prepared at 24% v/v, LIX®84I or LIX®684N-LV. All tests were determinedaccording to the BASF standard procedures.

Chemical characterization of PLS

For samples containing the same acid content, higher chloride concentration leadsto a lower pH. The equilibrium of the sulfate/bisulfate/sulfuric acid is altered by theaddition of chloride.

Ion Unit Value

Cu2+ g/L 4.5

SO42- g/L 95

Cl- g/L 0; 20; 40; 90 Fe T g/L 2.0 Fe2+ g/L 0.4

Fe3+ g/L 1.6

Mn2+ g/L 2.0

Al3+ g/L 6.1

Mg2+ g/L 11.2

Ni+ g/L 0 – 58 pH 1.0; 1.5

Extraction Isotherms

Copper load in organic PLS pH 1.0 Copper load in organic PLS pH 1.5

LIX®84I LIX®684N-LV

LIX®84I LIX®684N-LV

90 g/L Cl- 9.5 11.4 90 g/L Cl- 11.2 13.2 0 g/L Cl- 7.1 9.5 0 g/L Cl- 10.6 12.6

Diff. 2.4 1.9 Diff. 0,6 0.6 % increase 34 20 % increase 6 5

Mechanism proposed

• Extraction

*More favorable with low pH (4)

• Extraction increase: Equilibrium changes, K1 Products consumption Secondary reactions

𝐶𝐶𝐶𝐶𝐶𝐶𝑙𝑙+ + 2𝐻𝐻𝐻𝐻 ↔ 𝐶𝐶𝐶𝐶𝐻𝐻2 + 2𝐻𝐻+ + 𝐶𝐶𝑙𝑙−∗ 𝐾𝐾1

(1) HSC Chemistry 6.0, ©Outokompu Research 1974 – 2006(4) Szymanowski, J. Journal of R. & N. C. 208 (1996) p 183-194

0 10 20 30 40 50 60 70 80 900

0.005

0.01

0.015

0.02

0.025

0.03

0.035

[Cl-] gL-1[H

Cl (a

)] mol

L-1

pH 1.00pH 1.50pH 2.00

𝐻𝐻+ + 𝐶𝐶𝑙𝑙− ↔ 𝐻𝐻𝐶𝐶𝑙𝑙(𝑎𝑎𝑎𝑎)

∆𝐺𝐺𝑅𝑅(25°𝐶𝐶) = 0.968 𝑘𝑘𝑘𝑘𝑘𝑘𝑙𝑙 (1)

𝐾𝐾𝑒𝑒𝑎𝑎(25°𝐶𝐶) = 1.952 × 10−1 (1)

PRODUCTS

Stripping isotherms (Cu: g/L)

O/A ratio

LIX84I LIX684N-LV aq org aq org

1/10 37 0,45 37 2,09 1/4 38 0,49 38 2,23 1/3 39 0,50 39 2,34 1/1 47 0,66 46 2,80 3/2 52 0,88 51 3,31 5/2 58 1,13 58 3,98

LE: Cu 35 g/L, acid 180 g/L

Stripping stage have the usual behaviorKetoximes allow lower cooper in unloaded organic than modified aldoxime

Extraction kinetics

ion kinetic tests were performed at pH 1.5 and 1.0, with PLS having 0 and 90 g/L ofchloride concentration. Isotherm Graphs are illustrated in Figure 3. PLS withoutChloride content resulted in good extractions kinetics, considering the mixing time isindustrial operations is 150-180 seconds. When the PLS has high chlorideconcentration (90 g/L) the resulting kinetics show a relevant improvement, with theresults similar for both reagents, Ketoxime or Modified Aldoxime.

[Cl-] in PLS and TSF• O Continuity (pH 1.00; 23°C)

LIX® 84I 0 gL-1 Cl- LIX® 84I 90 gL-1 Cl-

TSF registered 10x

0 900

10

20

30

40

50

60

70

80

90

100

Cl- gL-1

Tiem

po, s

TSF C.O. LIX 84I pH 1.00 95 gL-1 SO42-

84

57

0 900

10

20

30

40

50

60

70

80

90

100

Cl- gL-1

Tiem

po, s

TSF C.O. LIX 684NLV pH 1.00 95 gL-1 SO42-

71

51

Iron transfer and washing stage• Organic iron behavior (20 gL-1 H2SO4)

OC OW1 OW20

1

2

3

4

5

6

7

8

9

10Variación FeT en orgánico sin Cl-

Etapa

FeT,

ppm

LIX 84ILIX 684NLV

OC OW1 OW20

1

2

3

4

5

6

7

8

9

10Variación FeT en orgánico con Cl-

Etapa

FeT,

ppm

LIX 84ILIX 684NLV

Chloride concentration in PLS: 0 gpl Chloride concentration in PLS: 90 gpl

Circuit evaluationPLS, g/L Conc. LE, g/L Conc. Stream Flow, m3/h SE, %

Cu+2 4.4 Cu+2 35 PLS 1000 E1 90

SO4-2 95 Acid 180 LE 230 E2 90

Cl- 0-90 Organic 1200 S 95 pH 1 O/A ratio 1.2

PLS: Pregnant leach solution, LE: Lean Electrolyte and SE: Stage Efficiency To evaluate the metallurgical performance, a 2E1S configuration was evaluated using the BASFISOCAL™ software to model the isothermsprepared previously. PLS with pH 1.0 having 0 or90 g/L of chloride concentration was modeled forKetoxime (LIX®84I) or Modified aldoxime(LIX®684N-LV) reagents. Principal parametersevaluated are; copper recovery, Max. copper load(ML), Cu in organic unloaded (UO) and Cu inorganic loaded (LO).

Copper behavior in organic circuit

Copper transfer increase when the chloride concentration in PLS is high

Copper extraction in 2E 1S circuit (%)Copper extraction in 2E 1S circuit (%)

Cl- g/L LIX®84I LIX®684N-LV

0 76.8 79.4 90 88.5 87.2

Diff. +11.7 +7.8

Conclusions and Recommendations(1/2)• For South America, hydrometallurgical operations are expected to increase

the use of seawater and/or the addition of chloride salts to the leachingprocess to improve the leaching performance of refractory and/orsecondary sulfides ores. Therefore, in South America, a 30% or 40% increaseof the hydrometallurgical operations in the next future will have highchloride concentration in their PLS (higher than 25 g/L).

• For these plants, PLS will have a low pH, with values between 1.0 to 1.5.This is a challenge to solvent extraction in terms of copper transfer. Whilethe higher chloride concentration in PLS means lower pH, it improves thechemical behavior of the oximes in extraction stages, having a positiveeffect on copper loaded in organic and in the extraction kinetics.

Conclusions and Recommendations (2/2)• Ketoximes (LIX®84I) have more improvement than Modified Aldoxime

(LIX®684N-LV). For a PLS with 4.4 g Cu/L and pH 1.0, the maximumcopper load increase is 34% for Ketoximes, while in the case of the ModifiedAldoxime the increase is 20%.

• Due to the better stripping performance of Ketoxime over ModifiedAldoxime in a conventional circuit with configuration 2E 1S with PLS at pH1.0, the Ketoxime (LIX®84I) performs slightly better than the ModifiedAldoxime (LIX®684N-LV) in terms of copper transfer.

• For a PLS having higher chloride concentration and low pH, the reagentsbased on Ketoxime are excellent alternatives in terms of copper transfer andphysical behavior. A positive physical behavior is reported in actualoperations due to the low viscosity of the reagent based on ketoximewithout equilibrium modifiers.

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