03 manganeso en plantas sx-ew

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MANGANESE IN SX/EW PLANTSMANGANESE IN SX/EW PLANTS

1

G.ZARATEG.ZARATE

CYTEC SEMINAR, ANTOFAGASTA, OCTOBER 2010


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CONTENTSCONTENTS

** INTRODUCTIONINTRODUCTION

* REVIEW OF MANGANESE PROBLEMS* REVIEW OF MANGANESE PROBLEMS

* PROPOSED CONTROL MEASURES* PROPOSED CONTROL MEASURES

* CHEMICAL REACTIONS* CHEMICAL REACTIONS

* ACTUAL DATA* ACTUAL DATA

* CONCLUSIONS* CONCLUSIONS


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INTRODUCTIONINTRODUCTION

The occurrence of significant concentrations of Mn in PLS isThe occurrence of significant concentrations of Mn in PLS iscommon in Chile and other countries.common in Chile and other countries.

The literature of its effects on industrial plants is sparse andThe literature of its effects on industrial plants is sparse andsome recommendations has no back up.some recommendations has no back up.

Only five operations have been reported in the past as sufferingOnly five operations have been reported in the past as suffering

* Tyrone* Tyrone* Chino* Chino* Johnson Camp* Johnson Camp* Chuquicamata* Chuquicamata

* Girilambone* Girilambone

Of these, only Chuquicamata and Girilambone have publishedOf these, only Chuquicamata and Girilambone have publishedthe results of their experience.the results of their experience.


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REVIEW OF MANGANESE PROBLEMSREVIEW OF MANGANESE PROBLEMS

Mn+2 itself has no effect on SX operation. It is transferred byMn+2 itself has no effect on SX operation. It is transferred byaqueous entrainment to the electrolyte.aqueous entrainment to the electrolyte.

Once in the electrolyte, it can be oxidized to higher oxidationOnce in the electrolyte, it can be oxidized to higher oxidation

. .. .

Some of the problems that have been associated to the highSome of the problems that have been associated to the high

oxidation state of Mn (Mn+7 and/ore Mn+3) are:oxidation state of Mn (Mn+7 and/ore Mn+3) are:


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* Deposition of black MnO2 inside the cells* Deposition of black MnO2 inside the cells

* Purple colouration of cell electrolyte OF (MnO4* Purple colouration of cell electrolyte OF (MnO4--))

* Oxidation of SX reagent and accumulation of reaction* Oxidation of SX reagent and accumulation of reaction

products in the organic phaseproducts in the organic phase

* Increased corrosion of stainless steel components* Increased corrosion of stainless steel components


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The effect on anode corrosion is as follows( RSR information):The effect on anode corrosion is as follows( RSR information):

* Manganese attacks the PbO* Manganese attacks the PbO22 layer and causes MnOlayer and causes MnO22 to buildto build

up in the layer.up in the layer.

MnSOMnSO44 + PbO+ PbO22 PbSO PbSO44 + MnO+ MnO22

* The PbSO* The PbSO44 is converted back to PbOis converted back to PbO22, but it is now deposited, but it is now deposited

in loose layers.in loose layers.

* These layers are easily spalled off causing contamination of* These layers are easily spalled off causing contamination of

the copper cathode.the copper cathode.


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8

10

12

te(g/kAh)

2

4

6

0 50 100 150 200 250 300 350 400

Manganese concentration (ppm)

CorrosionR


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8

10

12

te(g/kAh)

2

4

6

0 2 4 6 8 10 12

Iron concentration (g/l)

CorrosionR


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PROPOSED CONTROL MEASURESPROPOSED CONTROL MEASURES

Reducing the PLS entrainment by:Reducing the PLS entrainment by:

* Using coalescers and/or wash stages* Using coalescers and/or wash stages

* Reducing crud generation* Reducing crud generation

Maintaining manganese as Mn+2 by using:Maintaining manganese as Mn+2 by using:

* A minimum ratio of 8:1 or 10:1 (Fe:Mn).* A minimum ratio of 8:1 or 10:1 (Fe:Mn).

* A minimum concentration of 1 g/l Fe.* A minimum concentration of 1 g/l Fe.

* A minimum Fe+2/Mn ratio of 6:1.* A minimum Fe+2/Mn ratio of 6:1.


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CHEMICAL REACTIONSCHEMICAL REACTIONS

The overall reaction for the electrochemical deposition of MnO2The overall reaction for the electrochemical deposition of MnO2

is:is:

MnMn+2+2 + 2 H+ 2 H22O MnOO MnO22 + 4 H+ 4 H++ + 2 e+ 2 e-- (1)(1)

It occurs in several steps and there are several differingIt occurs in several steps and there are several differing

* MnO4* MnO4-- involved in the initial precipitation of MnOinvolved in the initial precipitation of MnO22on the anode.on the anode.

* Through adsorbed species such as MnOOH and* Through adsorbed species such as MnOOH andalso by disproportionation of Mnalso by disproportionation of Mn+3+3

Manganese dioxide can also form directly in the electrolyte asManganese dioxide can also form directly in the electrolyte as

slimes.slimes.


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Other possible reactions:Other possible reactions:

MnMn+2+2 Mn Mn+3+3 + e+ e-- (2)(2)

MnMn+2+2 + 4 H+ 4 H22O MnOO MnO44-- + e+ e-- (3)(3)

MnOMnO44-- + 4 Mn+ 4 Mn+2+2 + 8 H+ 8 H++ 5 Mn 5 Mn+3+3 + 4 H+ 4 H22OO (4)(4)

2 Mn2 Mn+2+2 + PbO+ PbO22 + HSO+ HSO44-- + 3 H+ 3 H++ 2 Mn 2 Mn+3+3 + PbSO+ PbSO44 + 2 H+ 2 H22OO (5)(5)


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MnMn+3+3 is unstable, except in very concentrated acid solutionsis unstable, except in very concentrated acid solutions

and disproportionate by reactionand disproportionate by reaction

2 Mn2 Mn+3+3 + 2 H+ 2 H22O MnOO MnO22 + Mn+ Mn+2+2 + 4 H+ 4 H++ (6)(6)

MnOMnO44-- is metastable and could only be observed at lowis metastable and could only be observed at low

concentration of Mnconcentration of Mn+2+2 and high potentials.and high potentials.


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To maintain manganese as MnTo maintain manganese as Mn+2+2, the most used reaction is:, the most used reaction is:

MnOMnO44-- + 5 Fe+ 5 Fe+2+2 + 8 H+ 8 H++ Mn Mn+2+2 + 5 Fe+ 5 Fe+3+3 + 4 H+ 4 H22OO (7)(7)

It can also react with chloride:It can also react with chloride:

2 MnO2 MnO44-- + 8 H+ 8 H++ + 6 Cl+ 6 Cl-- 2 MnO 2 MnO22 + 4 H+ 4 H22O + 3 ClO + 3 Cl22 (8)(8)


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ACTUAL DATAACTUAL DATA

Mn in Electrolyte (Cu 2003)

Plant Mn (ppm)

El Abra 38

MV 40

Andacollo 60-100

Cananea 26

Nacozari 300

Toquepala 100

Cerro Verde 70

Tyrone


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500

600

700

800

900

)

Planta 1

Planta 2

0

100

200

300

400

Oct-06 Abr-07 Nov-07 Jun-08 Dic-08 Jul-09 Ene-10 Ago-10 Feb-11

Month

Mn(pp

Planta 3

Planta 4

Planta 5

Planta 6


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** Fe in electrolyteFe in electrolyte

5,0

6,0

7,0

8,0

Planta 1

0,0

1,0

2,0

3,0

4,0


Month

Fet(gpl)

an a

Planta 3

Planta 4

Planta 5

Planta 6

Planta 7


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* Cl* Cl-- in the electrolytein the electrolyte

50

60

70

80

Planta 1

0

10

20

30

40


Month

Cl-(pp

m)

Planta 2

Planta 3Planta 5

Planta 6

Planta 7


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* Redox (mV/SHE)* Redox (mV/SHE)

700

800

900

1000

0

100

200

300

400

500

600

0,0 5,0 10,0 15,0 20,0 25,0 30,0 35,0 40,0

Fe+2/Mn

Redox(mV/S

HE) Planta 1

Planta 2Planta 3

Planta 4

Planta 5

Planta 6


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600

700

800

900

1000

SHE)

0

100

200

300

400

500

0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0 9,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0 17,0 18,0

Fe++/Mn

Redox

(mV


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600

700

800

900

1000

E) Planta 1

Planta 2

0

100

200

300

400

500

0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0

Fet (gpl)

Redox(m

V/S

Planta 3

Planta 4Planta 5

Planta 6

Planta 7


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600

700

800

900

1000

HE) Planta 1

Planta 2

0

100

200

300

400

500

0 5 10 15 20 25 30 35 40 45 50

Cl- (ppm)

Redox(mV/ Planta 3

Planta 4Planta 5

Planta 6

Planta 7


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800

850

900

950

1.000

HE) Planta 1

500

550

600

650

700

750

0 100 200 300 400 500 600 700 800 900

Mn (ppm)

Redox(

mV/

Planta 3

Planta 4

Planta 5

Planta 6


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800

850

900

950

1.000

SHE) Planta 1

Planta 2

500

550

600

650

700

750

0 50 100 150 200 250 300

Mn (ppm)

Redox

(mV/

Planta 3

Planta 4Planta 5

Planta 6


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CONCLUSIONSCONCLUSIONS

The information of the effects of Mn on EW operation is sparseThe information of the effects of Mn on EW operation is sparse

and some of the recommendations has no back up.and some of the recommendations has no back up.

The recommendations of a minimum ratio of Fe/Mn = 8 or 10The recommendations of a minimum ratio of Fe/Mn = 8 or 10

and Fe+2/Mn = 6 are not applicable.and Fe+2/Mn = 6 are not applicable.

Redox potential is affected by Mn, Fe and ClRedox potential is affected by Mn, Fe and Cl-- concentration.concentration.


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The highest redox potentials are obtained when Mn is < 10 ppmThe highest redox potentials are obtained when Mn is < 10 ppm

combined with a Clcombined with a Cl-- concentration >30 ppm and Fe 30 ppm and Fe 20 ppm and as high< 30 ppm and Mn > 20 ppm and as high

as 2 gpl and more for Mn30 ppm.

03 manganeso en plantas sx-ew

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