FLOTATION

OF MINERAL

MATERIALS

Class 2. Native metals and sulfides

B. Sulfides

lead (galena, PbS)

copper (chalcocite, covellite, chalcopyrite, bornite)

silver (argentite)

zinc (sphalerite)

A) Metals occurring in nature: iron, mercury, copper, gold, platinum

Class 2. Native metals and sulfides

A) Metals occurring in nature: iron, mercury, copper, gold, platinum

flotation with sulphydryl collectors (5 or more CH2 groups)

electrochemical character of adsorption of sulphydryl collectors on the surface of metals

dithiophosphates as well as xanthate + mercaptobenzothiazole, and dithiophosphate+ mercaptobenzothiazole mixtures can be used for flotation

0 2 4 6 8 10 12 14number of carbon atoms in xanthate

-45

-35

-25

-15

-5

log

(so

lub

ility

pro

du

ct)

Ag

Cu

Au

Zn

Ni

Cd

Pb

Cu

Hg

Me++

Me +

Solubility products of metal xanthates (after Aplan and Chander, 1988)

Class 2. Native metals and sulfides

B. Sulfides

lead (galena, PbS)

copper (chalcocite, covellite, chalcopyrite, bornite)

silver (argentite)

zinc (sphalerite)

Collectors for

flotation of sulfides

Table 12.36. Collectors containing sulfur applied for flotation of sulfides (after Aplan i Chander, 1988)

Collector type Formula Chemical name Manufacturer and designation

Mercaptan R–SH Pennwalt, Philips Dithiocarbonate (xanthate)

R–O–(C=S)–SK R–O–(C=S)–SNa

potassium ethyl sodium ethyl

AmCy

303 325

Dow

Z–3 Z–4

potassium isopropyl

sodium isopropyl

potassium butyl

sodium isobutyl

potassium sec-butyl

sodium sec-butyl

potassium amyl

sodium amyl

potassium sec-amyl

potassium hexyl

322

343

–

317

–

301

355

350

–

–

Z–9

Z–11

Z–7

Z–14

Z–8

Z–12

–

Z–6

Z–5

Z–10

Trithiocarbonate R–S–(C=S)–SNa Philips (Orform C0800)

Xanthogen formate

R–O–(C=S)–S–(C=O)–OR´

R=ethyl, R´=ethyl

R=izopropyl, R´=ethyl

R=butyl, R´=ethyl

Dow

Z–1

–

–

Minerec

A

2048

B

Xanthic ester R–O–(C=S)–S–R’

R=amyl, R´=allyl

R=heksyl, R´=allyl

AmCy

3302

3461

Minerec

1750

2023

Monothiophosphate

(R–O–)2(P=S)–ONa Amcy 194, 3394

Dithiophosphate (R–O–)2(P=S)–SNa

(R–O–)2(P=S)–SH

sodium diethyl

sodium di-isopropyl

sodium di-izobutyl

sodium di-isoamyl

sodium di-iso-sec-butyl

sodium di-methylamyl

cresylic acid+P2S5

AmCy (Aerofloat)

Na Aerofloat

Aerofloat 211, 243

Aerofloat 3477

Aerofloat 3501

Aerofloat 238

Aerofloat 249

Aerofloat 15

Dithiophosphinate (R–)2(P=S)–S–Na AmCy3418

Thiocarbamate R–(NH)–(C=S)–OR´

N-methyl-O-isopropyl

N-methyl-O-butyl

N-methyl-O-isobutyl

N-ethyl-O-isopropyl

N-ethyl-O-isobutyl

Dow

–

–

–

Z–200

–

Minerec

1703

1331

1846

1661

1669

Thiourea derivatives

(C6H5NH2)C=S (thiocarbanilide)

AmCy Aero. 130

Mercaptobenzo-thiazole

Seria AmCy 400

sulphides hydrophobization mechanism is complex and not well understood because there are many reactions between sulphide and sulphydryl collectors

Woods (1988) and others: hydrophobization of sulfides with sulphydryl collectors results from electrochemical reactions

electrons are transmitted from a collector to a sulfide mineral (anodic process), and then the electrons return to aqueous solution due to catodic reduction of oxygen

anodic oxidation, mechanism

a)chemisorbed xanthate Xad created from X- ion coming from

aqueous solution and a metal ion crystalline structure of sulfide:X– Xad + e

b) dixanthogene X2, as a result of X- ion oxidation

2X– X2 + 2e

c) metal xanthate MeX2, due to reaction of X- ion with metal sulfide

MS 2X– + MS MX2 + S + 2e

elemental sulfur S can next form thiosulfate, sulfate(IV) or sulfate(VI)2X– + MS + 4H2O MX2 + SO4

-2 + 8H++ 8e

catodic reduction of oxygen:O2 + 2H2O + 4e = 4OH-

other compounds xanthogenic acid HX, hydroxyxanthates, perxanthates, disulfide carbonates, etc. are possible

Hu at al., 2009

6 8 10 12 14pH

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

Eh,

mV

galena

PbS + X

HPbO2 + S + X2

Pb(OH)2 + S + X2

PbX2 + S

-

-

HPbO2 + S + X- -

Eh–pH diagram for galena + ethyl xanthate. Total amount of xanthate species was 10–4 M. Formation of S is assumed (after Woods, 1988)

0 2 4 6 8 10 12pH

0

20

40

60

80

100

flo

tati

on

re

co

ve

ry, %

pyrite

10 M KEtX

2x10 M KEtX

-5

-4

xanthate flotation of pyrite

-0.5 -0.3 -0.1 0.1 0.3 0.5EPt, mV

0

20

40

60

80

100

reco

very

du

rin

g f

irst

min

ut

of

flo

tati

on

, %

galena

a

b

Galena flotation with ethyl xanthate at pH = 8 as a function of applied potential to a platinum electrode in solution: a – galena kept in oxidizing environment before flotation, b – kept in reducing environment (Richardson, 1995; Guy and Trahar, 1985)

Complications

Activation Activation reaction of sphalerite with selected metal cations

and calculated free enthalpy of the reactions

Activation reaction free enthalpy, 0rG (kJ/mol)

ZnS +Fe2+=FeS+Zn2+ ZnS +Pb2+=PbS+Zn2+ ZnS +Cu2+=CuS+Zn2+ ZnS +2Ag+=Ag2S+Zn2+

35.2 –17.3 –62.9 – 142.3

Free enthalpy of the activation reactions for sulfides reacting with metal ions

Fe2+ Zn2+ Pb2+ Cu2+ Ag+ FeS –35.2 –52.5 –98.1 –177,5 ZnS 35.2 –17.3 –62.9 –142,3 PbS 52.5 17.3 –45.6 –125,0 CuS 98.1 62.9 45.6 –79,4 Cu2S 170.7 136.1 118.2 –6,8 Ag2S 177.5 142.3 125.0 79.4

Conclusion:

pyrrhotite (FeS) can be activated with all considered cations (∆Gr0 is negative), sphalerite with all cation except Fe3+, galena (PbS) only with Cu2+, and Ag+ ions. Both copper sulfides can be activated only with Ag+, while argentite (Ag2S) cannot be activated at all (∆G0f is positive).

FeS2ZnS

2e-

Zn2+

H2O1/2O2 2OH-

S0

two sulphides

Galvanic effects

sulphide and Fe grinding medium

e-

Fe2+

OH-

O2/H2O

sulfide mineral/cathode2e- + 1/2O2 + H2O ↔ 2OH-

aq

grinding media/anodeFes → Fe(1-x)s + xFe2+

aq + x2e-

Bakalarz, Ph.D. thesis 2012, Rao 2004

Bakalarz, Ph.D. thesis 2012, Greet et al., 2005

Rest potentials (SHE) for sulfides at pH=4 (Bakalarz 2012, Ph.D. thesis)

mineral formula

potential , mV

pyrite Fe2S 660 1 , 6302

marcasite (Zn, Fe)S2 630 1 chalkopyrite CuFeS2 560 1,3 , 5302

pyrrothite FeS 310 5 sphalerite ZnS 460 1,3

covellite CuS 450 1 , 4203

bornite Cu5 FeS4 400 3 , 4201 pentlandite (Fe,Ni)9S8 350 5

galena PbS 280 3 , 4001 argentite Ag2S 280 1,3

chalcocite Cu2S 440 2 , 3104 antymonite Sb2S3 120 1,3 molybdenite MoS2 110 1,3

heazlewoodite Ni 3S2 – 60 4

1 – Dettre i Johnson, 1964, za Witika i Dobiasem, 19952 – Hiskey i Wadsworth, 19813 – Kocabag i Smith, 19854 – Bozkurt i in., 1994, za Rao, 20045 – Bozkurt i in., 1998

Conclusion: flotation of sulfides depends on system

0

20

40

60

80

100

0 20 40 60 80 100

cum

ula

tive

re

cove

ry o

f th

e r

em

ain

ing

co

mp

on

en

ts in

the

ta

ilin

gs,

%

cumulative recovery of sulfide mineral in the concentrate, %

chalcocite

bornite

chalcopyrite

covellite

galena

organic carbon

0

20

40

60

80

100

0 20 40 60 80 100

cum

ula

tive

re

cove

ry o

f th

e re

ma

inin

g

com

po

ne

nts

in th

e ta

ilin

gs,

%

cumulative recovery of sulfide mineral in the concentrate, %

chalcocite

bornite

chalcopyrite

covellite

galena

shale

chalcopyrite>bornite> covelline >shale>chalcocite, galena

galena>bornite>shale>chalcocite >covellite>chalcopyrite

copper ore, n-dodecane 600 g/Mg, 10 min flot.model sulfide (5%), dolomite (47.5%) and quartz (47.5%) mixture, flotation with z n-dodecane 200 g/Mg

(Bakalarz 2012, Ph.D. thesis

Class 3. Oxidized minerals of non-ferrous metals

cerussite (PbCO3)

vanadinite (Pb5[Cl(VO4)3])

anglesite (PbSO4)

malachite (CuCO3·Cu(OH)2

azurite (2CuCO3·Cu(OH)2)

chrysocolla (hydrated copper silicate)

tenorite (CuO)

cuprite (Cu2O)

smithsonite (ZnCO3)

1. Sulfidization

Approaches:

2. Flotation using either cationic or anionic collectors (as in the case of oxide-type minerals)

Class 3. Oxidized minerals of non-ferrous metals

-MO + S2- + 2H+ = -MS + H2O

Sulfidization reaction

0 10 20 30 40dosage of amyl xanthate, mg/dm 3

0

20

40

60

80

100

rec

ov

ery

, % malachite

1

2

3

Influence of conditions of flotation on recovery of malachite sulfidized with 960 mg/dm 3 of Na2S·9H2O in the presence of frother (amyl alcohol 60 mg/l): 1 – flotation when after sulfidization the solution is replaced with pure aqueous, 2 – flotation after 25 minutes of air bubbling through the solution containing sulfide ions, 3 – flotation directly after sulfidization in the presence of sulfide ions (after Soto and Laskowski, 1973)

also anionic and cationic collectors can be used (as for oxides and hydroxides

Class 4. Oxides and hydroxides

Consists of simple oxides (Fe2O3, SnO2), oxyhydroxides (AlOOH) as well as complex oxides and complex hydroxides (spinels, silicates, aluminosilicates).

Table 12.38. Influence of structure of silicates on their flotation with anionic and cationic collectors (after Manser, 1975)

Silicate groupCollector

orthosilicates pyroxene amphibole frame

Anionic good week none none

Cationic satisfactory* satisfactory * good very good

* Flotation depends on pH

2 4 6 8 10 12pH

0

20

40

60

80

100fl

ota

tio

n r

ec

ov

ery

, %

albite

quartz

varous minerals

Oleate flotation of oxide and silicates

Concentration - pH diagram for sodium oleate aqueous solutions showing predominance of various oleate species (Drzymala, 1990): c – activity of oleate species, mol/dm3, B (or ) – degree of binding oleate with sodium ions in associated species (number of sodium ions per one oleate ion in the associate)

      Flotation (after a) pH of flotation b Monohydroxy

complexRange of pH

at concentration> 10–7 M

pH of maximum

concentration

mineral pH of maximum flotation

activated quartz

FeOH++ 0–3.9 2.7 augite 2.9 2–8*AlOH+ 2.1–5.9 4.3     2–8PbOH+ 3.2–12.4 8.7      MnOH+ 7.6–11.6 9.5 pirolusite 9  MgOH+ 8.4–12.5 10.5 magnesite 10.4 7–13CaOH+ > 8.5 13.1 Augite 11 7–13CuOH+ 5.1–8.1 6.5      FeOH+ 4.5–12.1 8.7 chromite and

other iron minerals

8.7, 8  

a – Fuerstenau and Palmer (1976), b – Daellenbach and Tiemann (1964). * The participation of FeOH+ ions in widening the pH range of flotation of activated quartz activated with FeOH++ ions cannot be ruled out.

Comparison of pH ranges of oleate flotation of minerals as well as activated quartz and pH of existence of metal monohydroxy complexes

Fatty acids adsorption

a b c

oilparticle

x

Schematic illustration of modes of adhesion of a colloidal collector (here as an oil drop) to solid surface: a – contactless

(heterocoagulation), b – contact, c – semicontact adhesion

0 2 4 6 8 10 12initial concentration of sodium oleate, mol/dm 3(x104)

0

20

40

60

80

100

reco

very

, %

0

1

2

3

4

5

zircon

ad

so

rpti

on

de

ns

ity,

mo

l/cm

2 x

10

4

At high oleate species concentrations flotation decreases even though the oleate adsorption increases. It is assumed that it results from adsorption

of hydrophilic micelles (based on data of Dixit and Biswas, 1973)

Zr[SiO4]

0 2 4 6 8 10 12 14pH

0

20

40

60

80

100

reco

very

, %

iep 6.9 kyanite

oleic

linoleic

linoleniclauric

Kyanite flotation with 10–4 kmol/m3 of fatty acids (Choi and Oh, 1965). Applied acids: laurate (C11H23COOH), linoleic (C5H11–CH=CH–CH2–CH=CH–(CH2)7COOH), linolenic CH3–[CH2–

CH=CH]3(CH2)7COOH and oleic (C17H33COOH)

Al2[OSiO4]

According to Rao and Forssberg (1991), depending on the sign of surface potential and its value for calcium minerals, the following reactions, leading to the formation of mono- and double layers of compounds, take place:

 on electrically neutral sites:

–CaOH + –OOCR = –Ca+ –OOCR + OH–

–CaOH + Na+ –OOCR + OH– = –CaO Na OOCR– + H2O

–CaOH + Ca++ –OOCR + OH– = –CaO Ca OOCR– + H2O

 on positively charged sites:

–CaOH2+ + –OOCR + OH– = –Ca+ –OOCR + H2O

 on negatively charged sites:

–CaO– Na+ + –OOCR = –CaO Na OOCR, where < 1,

–CaO– Ca++ + –OOCR = –CaO Ca OOCR, where <or = 1.

Adosrption of oleates on calcium minerals

Primary amine Secondary amine Tertiary amine

AMINES

dissociation/adsorption

quaternary ammonium compoundspermanetly charged

R groups can be alkyl, aryl, the same or different

Reaction KR–NH2 (aq)+H2O R–NH3

+ (aq)+OH– 4.3·10–4

R–NH2 (s) R–NH2 (aq) 2.0·10–5

micellization CMC = 1.3·10–2 Miep pH = 11

Equilibrium constants of selected reactions, iep and CMC for dodecylamine in aqueous (after Laskowski, 1988)

5 7 9 11 13pH

-6

-5

-4

-3

-2

-1

log

(am

ine

con

cen

trat

ion

, km

ol/m

3)

micelle

colloidal suspension

aqueous solution

+ -

iep

R-NH2(aq)

R-NH3 (aq)+

R-NH2 (s)

stable

(R-NH3 (aq))n+

unstable

Diagram of predomination of various forms of dodecylamine as a function of pH of solution (data after Laskowski, 1988)

AMINES

5 7 9 11 13pH

-6

-5

-4

-3

-2

-1

log

(am

ine

con

cen

trat

ion

, km

ol/m

3)

micelle

colloidal suspension

aqueous solution

+ -

iep

R-NH2(aq)

R-NH3 (aq)+

R-NH2 (s)

stable

(R-NH3 (aq))n+

unstable

6 8 10 12 14

pH

0

20

40

60

80

100re

co

very

, %

quartz

5×10-4 M C12H25-NH2×HCl

iep

R-NH2 precipitation

competition of OH-

Relationship between quartz flotation with amine and pH. Following good flotation in alkaline solutions there is a drop in flotation as a result of precipitation of coagulating amine. At high pH an increase of flotation is caused by stable of amine suspension (after Laskowski et al., 1988)

10-6

10-5

10-4

10-3

10-2

collector concentration, kmol/m3

0

10

20

30

40

50a

ds

orp

tio

n d

en

sit

y, m

ol/

m2 x

101

1

0

20

40

60

80

100

-100

-60

-20

20

60

100

quartz-dodecylamine

zeta

po

ten

tia

l, m

V

co

s

0.80

0.90

flo

tati

on

re

co

ve

ry

Flotation of particles increases with increasing concentration of collector in the system and is proportional to collector adsorption and hydrophobicity caused by the adsorption. Collector adsorption is manifested by the increase of zeta potential of particles (after Fuerstenau et al., 1964 and Fuerstenau and Urbina, 1988), pH = 6–7

10-08

10-07

10-06

10-05

10-04

10-03

10-02

10-01

1000

amine concentration, kmol/m 3

0

20

40

60

80

100fl

ota

tio

n r

eco

very

, %

18

QUARTZ

16 14 12 10 8 6 4

Amine flotation of quartz

Table 12.44. Solubility product (Kr) for selected compounds at 293 K (after Barycka and Skudlarski, 1993)

Compound Ir Compound Ir 1 2 3 4

Fluoride sulfite CaF2 4.0·10–11 BaSO4 9.8·10–11 SrF2 2.5·10–9 SrSO4 6.2·10–7 MgF2 6.5·10–9 CaSO4 9.1·10–6 Chloride sulfide AgCl 1.8·10–10 HgS 1.9·10–53

PbCl2 1,7·10–5 Ag2S 6.3·10–50 Bromide Cu2S 7.2·10–49 AgBr 4.6·10–13 CuS 4.0·10–36 PbBr2 2.8·10–5 PbS 6.8·10–29

Iodide ZnS 1.2·10–28 AgI 8,3·10–17 NiS 1.0·10–24 PbI2 7.1·10–9 CoS 3.1·10–23 Carbonate FeS 5.1·10–18 PbCO3 7.2·10–14 MnS 1.1·10–15 ZnCO3 1.7·10–11 cyanide

CaCO3 7.2·10–9 Hg2(CN)2 5.0·10–40 MgCO3 3.5·10–8 CuCN 3.2·10–20 Hydroxide chromate Fe(OH)3 4.5·10–37 PbCrO4 2.8·10–13 Zn(OH)2 3.3·10–17 BaCrO4 1.2·10–10 Mg(OH)2 1.2·10–11 CuCrO4 3.6·10–6

Class 5. Sparingly soluble salts

2 4 6 8 10 12 14

pH

0

20

40

60

80

100re

co

very

, %

fluorite

SDS

DDA

NaOl

NaOl - sodium oleate, DDA-dodecylamine, SDS,- sodium dedecyl sulfite

Flotation with potassium octylohydroxymate

Class 5. Sparingly soluble salts

0 2 4 6 8 10 12 14

pH

0

20

40

60

80

100

reco

very

, %

chrysocolla

bastnesite

calcite

barite

10-6

10-5

10-4

10-3

concentration of sodium oleate, mol/dm 3

0

20

40

60

80

100

reco

very

, %

calcite

fluorite

apatitebarite

ionic strength0.002 M NaClO4 pH = 9.5

10-6

10-5

10-4

10-3

sodium oleate concentration, mol/dm 3

0

20

40

60

80

100

rec

ov

ery

, %

calcitefluorite chloroapatite

Flotation of sparingly soluble minerals with oleic acid: a – after Finkelstein (1989), natural pH, b – after Parsonage et al., (1982)

the same minerals - different flotation response

Reagent Flotation of  barite fluorite

Collectors Alkyl sulfatePretopon floats well at pH 8–12 reduced flotation at pH 8Siarczanol N-2 floats well at pH 4–12 flotation at pH 6–10Sodium dodecyl sulfate (SLS) floats well at pH 4–12 cease of flotation at pH > 7

  Alkyl sulfonate

Oleic sulfosuccinate floats well at pH 5–12 gradual cease of flotation at pH < 8

Streminal ML floats well at pH 5–12 floats well at pH 5–12Sodium kerylbenzosulfonate floats well at pH 4–12 cease of flotation at pH > 7

  Fatty acidsSodium oleate floats well at pH 6.5–8.5 floats well at pH 4–10  Other collectorsKamisol OC, cationic collector floats well at pH 3–12 flotation at pH 3–12

Rokanol T-16, nonionic collector weak collecting power weak collecting power

Depressant TanninsQuebracho S(+ SLS)

no flotation in alkaline solutions

total cease of flotation in alkaline solutions

Quebracho S (+ Pretopon G) cease of flotation at pH > 6 cease of flotation at pH > 6

Tannin (+ SLS) cease of flotation in alkaline solutions

cease of flotation in alkaline solutions

Gallic acid (+ SLS)

cease of flotation in alkaline solutions

cease of flotation in alkaline solutions

Tannin D (+ SLS) cease of flotation in alkaline solutions

cease of flotation in alkaline solutions

Tannin M (+ SLS) cease of flotation in alkaline solutions

cease of flotation in alkaline solutions

  Other depressantsDextrin (+ sodium oleate)

no flotation in alkaline solutions flotation at pH 6–9

Glycerol (+ sodium oleate)

full flotation depression at pH 5–11

no flotation in acidic environment; no week flotation in alkaline solutions

Influence of different collectors and depressants on barite and fluorite flotation (table after Pradel, 2000 based on Sobieraj, 1985)

Influence of depressant (70 mg/dm3 Al2(SO4)3 and 70 mg/dm3 Na2SiO3) on flotation of fluorite and calcite mixture (dashed line) in the presence of sodium oleate (100 mg/dm3) (after Abeidu, 1973). Solid line indicates flotation in the absence of depressant

2 4 6 8 10 12

pH

0

20

40

60

80

100

reco

very

, %

calcite

calcite fluorite

fluorite

+ depressor

+ depressor

Class 6. Soluble salts Sign of surface charge for selected soluble salts

(after Miller et al., 1992)

Salt Surface charge sign Salt Surface charge sign measured predicted* measured predicted*

LiF + +– KBr – + NaF + + RbBr – +

KF + + CsBr + + RbF + + LiI – – CsF + + NaI – – LiCl – – KI + NaCl + – RbI – – KCl – + CsI + +– RbCl + + NaI·2H2O + CsCl + + K2SO4 –** LiBr – – Na2SO4·10H2

O –**

NaBr – – Na2SO4 –**

* Predicted from the ions hydration theory for inos in crystalline lattice (Miller et al., 1992). ** Hancer et al., 1997.

10-06

10-05

10-04

10-03

10-02

dodecylamine hydrochloride, kmol/m 3

0

20

40

60

80

100fl

ota

tio

n r

ec

ov

ery

, % KClK2SO4 Na2SO4×10H2O

Na2SO4 NaCl

Soluble salts

0 50 100 150 200 250dosage of depressor, g/Mg

0

20

40

60

80

100

rec

ov

ery

, %

KCl

fines

CMC

guarPAM

Application of depressants for removing fines of gangue minerals during amine flotation of KCl (after Alonso and Laskowski, 1999). CMC denotes carboxymethylcellulose PAM - polyacrylamide of low molecular weight, while guar is a natural polysaccharide

depressants are called blinders