FLOTATION
OF MINERAL
MATERIALS
Class 2. Native metals and sulfides
A) Metals occurring in nature: iron, mercury, copper, gold,
platinum
B. Sulfides
lead (galena, PbS)
copper (chalcocite, covellite, chalcopyrite, bornite)
silver (argentite)
zinc (sphalerite)
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)
dithiophosphates as well as xanthate + mercaptobenzothiazole,
and dithiophosphate+ mercaptobenzothiazole mixtures can be
used for flotation
electrochemical character of adsorption of sulphydryl
collectors on the surface of metals
Me
-5
+
++
lo g (s o lu b ility p ro d u c t)
Me
-15
Cd
Ag
Zn
Cu
Ni
-25
Pb
Au
-35
Cu
Hg
-45
0
2
4
6
8
10
12
14
number of carbon atoms in xanthate
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)
Table 12.36. Collectors containing sulfur applied for flotation of sulfides (after Aplan i Chander, 1988)
Collector type
Mercaptan
Dithiocarbonate
(xanthate)
Collectors for
Formula
Chemical name
R–SH
R–O–(C=S)–SK
R–O–(C=S)–SNa
flotation of sulfides
potassium ethyl
sodium ethyl
potassium isopropyl
322
Z–9
sodium isopropyl
343
Z–11
potassium butyl
–
Z–7
sodium isobutyl
317
Z–14
–
Z–8
sodium sec-butyl
301
Z–12
potassium amyl
355
–
sodium amyl
350
Z–6
potassium sec-butyl
Trithiocarbonate
Xanthogen
formate
potassium sec-amyl
–
Z–5
potassium hexyl
–
Z–10
R–S–(C=S)–SNa
Philips (Orform
C0800)
R–O–(C=S)–S–(C=O)–OR´
Dow
R=ethyl, R´=ethyl
R=izopropyl, R´=ethyl
R=butyl, R´=ethyl
Xanthic ester
(R–O–)2(P=S)–ONa
Dithiophosphate
(R–O–)2(P=S)–SNa
Thiocarbamate
B
R=amyl, R´=allyl
3302
1750
R=heksyl, R´=allyl
3461
2023
Amcy 194, 3394
AmCy (Aerofloat)
Aerofloat 3477
sodium di-isoamyl
Aerofloat 3501
sodium di-iso-sec-butyl
Aerofloat 238
sodium di-methylamyl
Aerofloat 249
cresylic acid+P 2S5
Aerofloat 15
(R–)2(P=S)–S–Na
AmCy3418
R–(NH)–(C=S)–OR´
Mercaptobenzothiazole
(C6H5NH2)C=S
(thiocarbanilide)
Na Aerofloat
Aerofloat 211, 243
sodium di-izobutyl
Dow
Minerec
N-methyl-O-isopropyl
–
1703
N-methyl-O-butyl
–
1331
N-methyl-O-isobutyl
–
1846
N-ethyl-O-isopropyl
Z–200
1661
–
1669
N-ethyl-O-isobutyl
Thiourea
derivatives
2048
Minerec
sodium di-isopropyl
Dithiophosphinate
A
–
–
sodium diethyl
(R–O–)2(P=S)–SH
Minerec
Z–1
AmCy
R–O–(C=S)–S–R’
Monothiophosphat
e
Manufacturer and
designation
Pennwalt, Philips
AmCy
Dow
303
Z–3
325
Z–4
AmCy Aero. 130
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
0.5
Pb(OH)
2
+ S+ X
2
0.4
HPbO
2
+ S+ X
2
0.3
E h , mV
0.2
PbX
2
+S
HPbO
0.1
0
PbS + X
2
+ S+ X
-
-
-0.1
galena
-0.2
-0.3
6
8
10
12
14
pH
Eh–pH diagram for galena + ethyl xanthate. Total amount of xanthate
species was 10–4 M. Formation of S is assumed (after Woods, 1988)
100
-4
2x10 M KEtX
flo tatio n r eco ver y, %
80
60
-5
10 M KEtX
40
20
pyrite
0
0
2
4
6
8
pH
xanthate flotation of pyrite
10
12
r ecover y dur ing fir st minut of flotation, %
100
a
80
60
40
b
20
0
-0.5
galena
-0.3
-0.1
0.1
0.3
0.5
E Pt , m V
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
ZnS +Fe2+=FeS+Zn2+
ZnS +Pb2+=PbS+Zn2+
ZnS +Cu2+=CuS+Zn2+
ZnS +2Ag+=Ag2S+Zn2+
Fe2+
FeS
ZnS
PbS
CuS
Cu2S
Ag2S
Conclusion:
35.2
52.5
98.1
170.7
177.5
free enthalpy, DGr0 (kJ/mol)
35.2
–17.3
–62.9
–142.3
Free enthalpy of the activation reactions for
sulfides reacting with metal ions
Zn2+
Pb2+
Cu2+
–35.2
–52.5
–98.1
–17.3
–62.9
17.3
–45.6
62.9
45.6
136.1
118.2
142.3
125.0
79.4
Ag+
–177,5
–142,3
–125,0
–79,4
–6,8
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).
Galvanic effects
1/2O2
H2O
2OH-
Bakalarz, Ph.D. thesis
2012, Rao 2004
Zn2+
S0
FeS2
2e-
ZnS
two sulphides
sulfide mineral/cathode
2e- + 1/2O2 + H2O ↔ 2OH-aq
Fe2+
OHO2/H2O
e-
grinding media/anode
Fes → Fe(1-x)s + xFe2+aq + x2e-
Bakalarz, Ph.D. thesis 2012,
Greet et al., 2005
sulphide and Fe grinding medium
Rest potentials (SHE) for sulfides at pH=4 (Bakalarz 2012, Ph.D. thesis)
mineral
pyrite
marcasite
chalkopyrite
pyrrothite
sphalerite
covellite
bornite
pentlandite
galena
argentite
chalcocite
antymonite
molybdenite
heazlewoodite
formula
Fe S
2
(Zn, Fe)S
2
CuFeS
2
FeS
ZnS
CuS
Cu 5FeS 4
(Fe,Ni) 9S 8
PbS
Ag S
2
Cu S
2
Sb S
2 3
MoS 2
Ni S
3 2
– Dettre i Johnson, 1964, za Witika i Dobiasem, 1995
– Hiskey i Wadsworth, 1981
3 – Kocabag i Smith, 1985
4 – Bozkurt i in., 1994, za Rao, 2004
5 – Bozkurt i in., 1998
1
2
potential , mV
660 1, 630
630 1
560 1,3, 530
310 5
460 1,3
450 1, 420
400 3, 420
350 5
280 3, 400
280 1,3
440 2, 310
120 1,3
110 1,3
– 60 4
2
2
3
1
1
4
galena>bornite>shale>chalcocite
>covellite>chalcopyrite
chalcopyrite>bornite> covelline
>shale>chalcocite, galena
100
cumulative recovery of the remaining
components in the tailings, %
cumulative recovery of the remaining
components in the tailings, %
100
80
60
chalcocite
40
bornite
chalcopyrite
covellite
20
galena
shale
20
60
chalcocite
bornite
40
chalcopyrite
covellite
20
galena
organic carbon
0
0
0
80
40
60
80
100
cumulative recovery of sulfide mineral in the
concentrate, %
model sulfide (5%), dolomite (47.5%) and quartz
(47.5%) mixture, flotation with z n-dodecane 200
g/Mg
0
20
40
60
80
100
cumulative recovery of sulfide mineral in the
concentrate, %
copper ore, n-dodecane 600 g/Mg, 10 min flot.
(Bakalarz 2012, Ph.D. thesis
Conclusion: flotation of sulfides depends on system
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)
Class 3. Oxidized minerals of non-ferrous metals
Approaches:
1. Sulfidization
2. Flotation using either cationic or anionic
collectors (as in the case of oxide-type minerals)
Sulfidization reaction
-MO + S2- + 2H+ = -MS + H2O
100
1
80
re c o v e ry , %
2
60
malachite
40
20
3
0
0
10
20
dosage of amyl xanthate, mg/dm
30
40
3
Influence of conditions of flotation on recovery of malachite sulfidized with 960 mg/dm3 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).
T able 1 2 .3 8 . Influe nce of str uctu re of silic ates o n th eir flotatio n w ith
anio nic a n d cationic collectors (after M anse r, 1 9 75 )
C ollecto r
S ilicate g rou p
orth osilicates
py rox ene
a m p hibole
fra m e
A nio nic
g ood
w eek
no ne
no ne
C atio nic
satisfactory *
satisfactory *
g ood
very g oo d
* F lo tatio n d ep en d s o n p H
100
flotation r ecover y, %
80
varous minerals
60
40
albite
20
quartz
0
2
4
6
8
10
12
pH
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)
Comparison of pH ranges of oleate flotation of minerals as well as activated
quartz and pH of existence of metal monohydroxy complexes
Monohydroxy
complex
FeOH++
AlOH+
PbOH+
MnOH+
MgOH+
CaOH+
CuOH+
FeOH+
Range of pH
at concentration>
10–7 M
0–3.9
2.1–5.9
3.2–12.4
7.6–11.6
8.4–12.5
> 8.5
5.1–8.1
4.5–12.1
pH of
maximum
concentration
2.7
4.3
8.7
9.5
10.5
13.1
6.5
8.7
Flotation (after a)
mineral
pH of
maximum
flotation
augite
2.9
pirolusite
magnesite
Augite
9
10.4
11
chromite and
other iron
minerals
8.7, 8
pH of flotation b
activated quartz
2–8*
2–8
7–13
7–13
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.
Fatty acids adsorption
particle
oil

x
a
b
c
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
5
80
4
60
3
40
2
zircon
20
1
0
0
0
2
4
6
8
10
initial concentration of sodium oleate, mol/dm
12
adsorption density, m ol/cm
re c o v e ry , %
2
100
x 10 4
Zr[SiO4]
3 (x10 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)
100
oleic
re c o v e ry , %
80
linoleic
60
linolenic
lauric
40
20
kyanit e
iep 6.9
0
0
2
4
6
8
10
12
14
Al2[OSiO4]
pH
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)
Adosrption of oleates on calcium minerals
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.
AMINES
Primary amine
Secondary amine
Tertiary amine
dissociation/adsorption
quaternary ammonium compounds
permanetly charged
R groups can be alkyl, aryl, the same or different
AMINES
Equilibrium constants of selected reactions, iep and CMC for dodecylamine in aqueous
(after Laskowski, 1988)
Reaction
R–NH2 (aq)+H2O  R–NH3+ (aq)+OH–
R–NH2 (s)  R–NH2 (aq)
micellization
iep
lo g (a m in e c o n c e n tra tio n , k m o l/m 3 )
-1
K
4.3·10–4
2.0·10–5
CMC = 1.3·10–2 M
pH = 11
iep
micelle
+
(R-NH 3 (aq) ) n
colloidal suspension
-2
unstable
-
+
-3
R-NH 2 (s)
aqueous
solution
-4
+
R-NH 3 (aq)
stable
-5
R-NH 2(aq)
-6
5
7
9
11
13
pH
Diagram of predomination of various forms of dodecylamine
as a function of pH of solution (data after Laskowski, 1988)
lo g (a m in e c o n c e n tra tio n , k m o l/m 3 )
-1
iep
micelle
+
(R-NH 3 (aq) ) n
colloidal suspension
-2
unstable
-
+
-3
R-NH 2 (s)
aqueous
solution
-4
+
R-NH 3 (aq)
stable
-5
R-NH 2(aq)
-6
5
7
9
11
13
pH
100
quartz
re c o v e ry , %
80
R-NH
2
precipitation
60
iep
40
5×10
-4
MC
12
H 25 -NH 2 ×HCl
20
competition of OH
-
0
6
8
10
12
14
pH
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)
100
100
80
60
60
20
40
-20
20
-60
0
-100
0.80
30
20
0.90
10
0 -6
10
10
-5
10
-4
10
collector concentration, kmol/m
-3
10
-2
z e ta p o te n tia l, m V
40
flo ta tio n re c o v e ry
quartz-dodecylamine
cos 
a d s o rp tio n d e n s ity , m o l/m 2 x 1 0 1 1
50
3
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
100
flotation recovery , %
80
QUARTZ
60
40
18
20
0
10
-0 8
10
16
-0 7
10
14
-0 6
12
10
-0 5
10
10
-0 4
8
10
-0 3
am ine concentr ation, km ol/m
Amine flotation of quartz
6
10
4
-0 2
10
3
-0 1
10
00
Class 5. Sparingly soluble salts
Table 12.44. Solubility product (Kr) for selected compounds at 293 K (after Barycka and Skudlarski, 1993)
Compound
1
Fluoride
CaF2
SrF2
MgF2
Chloride
AgCl
PbCl2
Bromide
AgBr
PbBr2
Iodide
AgI
PbI2
Carbonate
PbCO3
ZnCO3
CaCO3
MgCO3
Hydroxide
Fe(OH)3
Zn(OH)2
Mg(OH)2
Ir
2
4.0·10–11
2.5·10–9
6.5·10–9
1.8·10–10
1,7·10–5
4.6·10–13
2.8·10–5
8,3·10–17
7.1·10–9
7.2·10–14
1.7·10–11
7.2·10–9
3.5·10–8
4.5·10–37
3.3·10–17
1.2·10–11
Compound
3
sulfite
BaSO4
SrSO4
CaSO4
sulfide
HgS
Ag2S
Cu2S
CuS
PbS
ZnS
NiS
CoS
FeS
MnS
cyanide
Hg2(CN)2
CuCN
chromate
PbCrO4
BaCrO4
CuCrO4
Ir
4
9.8·10–11
6.2·10–7
9.1·10–6
1.9·10–53
6.3·10–50
7.2·10–49
4.0·10–36
6.8·10–29
1.2·10–28
1.0·10–24
3.1·10–23
5.1·10–18
1.1·10–15
5.0·10–40
3.2·10–20
2.8·10–13
1.2·10–10
3.6·10–6
100
SDS
re c ov e ry , %
80
DDA
60
fluor it e
40
NaOl
20
0
2
4
6
8
pH
10
12
14
NaOl - sodium oleate, DDA-dodecylamine,
SDS,- sodium dedecyl sulfite
Class 5. Sparingly soluble salts
100
chr ysocolla
re c ov e ry , %
80
calcite
60
40
bastne site
20
bar ite
0
0
2
4
6
8
10
12
pH
Flotation with potassium octylohydroxymate
14
the same minerals - different flotation response
100
100
80
re c o v e ry , %
re c o v e ry , %
80
60
fluorit e
calcite
chloro
apatite
40
60
ionic strength
0.002 M NaClO
4
pH = 9.5
calcite
40
fluorite
20
20
apatit e
barit e
0
10
-6
10
-5
10
sodium oleate concentration, mol/dm
-4
10
3
-3
0
10
-6
10
-5
10
-4
concentration of sodium oleate, mol/dm
Flotation of sparingly soluble minerals with oleic acid: a – after Finkelstein (1989), natural pH, b –
after Parsonage et al., (1982)
10
3
-3
Influence of different collectors and depressants on barite and fluorite flotation
(table after Pradel, 2000 based on Sobieraj, 1985)
Reagent
Flotation of
barite
fluorite
Collectors
Alkyl sulfate
Pretopon
floats well at pH 8–12
reduced flotation at pH 8
Siarczanol N-2
floats well at pH 4–12
flotation at pH 6–10
Sodium dodecyl sulfate floats well at pH 4–12
cease of flotation at pH > 7
(SLS)
Alkyl sulfonate
gradual cease of flotation at
Oleic sulfosuccinate
floats well at pH 5–12
pH < 8
Streminal ML
floats well at pH 5–12
floats well at pH 5–12
Sodium
floats well at pH 4–12
cease of flotation at pH > 7
kerylbenzosulfonate
Fatty acids
Sodium oleate
floats well at pH 6.5–8.5
floats well at pH 4–10
Other collectors
Kamisol OC,
floats well at pH 3–12
flotation at pH 3–12
cationic collector
Rokanol T-16,
weak collecting power
weak collecting power
nonionic collector
Depressant
Tannins
Quebracho S
no flotation in alkaline
total cease of flotation in
(+ SLS)
solutions
alkaline solutions
Quebracho S
cease of flotation at pH > 6
cease of flotation at pH > 6
(+ Pretopon G)
cease of flotation in alkaline cease of flotation in alkaline
Tannin (+ SLS)
solutions
solutions
Gallic acid
cease of flotation in alkaline cease of flotation in alkaline
(+ SLS)
solutions
solutions
cease
of
flotation
in
alkaline
cease of flotation in alkaline
Tannin D (+ SLS)
solutions
solutions
cease
of
flotation
in
alkaline
cease of flotation in alkaline
Tannin M (+ SLS)
solutions
solutions
Other depressants
Dextrin
no flotation in alkaline
flotation at pH 6–9
(+ sodium oleate)
solutions
no flotation in acidic
Glycerol
full flotation depression at pH environment; no week
(+ sodium oleate)
5–11
flotation in alkaline
solutions
100
80
fluorit e
re c o v e ry , %
calcite
+
depressor
60
+ depressor
40
fluorite
20
calcite
0
2
4
8
6
10
12
pH
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
Class 6. Soluble salts
Sign of surface charge for selected soluble salts
(after Miller et al., 1992)
Salt
LiF
NaF
KF
RbF
CsF
LiCl
NaCl
KCl
RbCl
CsCl
LiBr
NaBr
Surface charge sign
measured
predicted*
+
+–
+
+
+
+
+
+
+
+
–
–
+
–
–
+
+
+
+
+
–
–
–
–
Salt
KBr
RbBr
CsBr
LiI
NaI
KI
RbI
CsI
NaI·2H2O
K2SO4
Na2SO4·10H2
O
Na2SO4
Surface charge sign
measured
predicted*
–
+
–
+
+
+
–
–
–
–
+
–
–
+
+–
+
–**
–**
–**
* Predicted from the ions hydration theory for inos in crystalline lattice (Miller et al., 1992).
** Hancer et al., 1997.
Soluble salts
100
flotation recove ry, %
80
Na 2 SO 4 ×10H 2 O
KCl
K 2 SO 4
60
40
20
0
10
NaCl
Na 2 SO 4
-0 6
10
-0 5
10
-0 4
10
dodecylam ine hydr ochlor ide, km ol/m
-0 3
10
3
-0 2
depressants are called blinders
100
KCl
re c o v e ry , %
80
60
CMC
PAM
guar
40
fines
20
0
0
50
100
150
200
250
dosage of depressor, g/Mg
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