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
(sol
ubili
ty p
rodu
ct)
AgCu
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 fromaqueous 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
6 8 10 12 14pH
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
E h, m
V
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
flota
tion
reco
very
, %
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
dur
ing
first
min
ut o
f flo
tatio
n, %
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)9S 8 350 5
galena PbS 280 3 , 4001 argentite Ag2S 280 1,3
chalcocite Cu2S 440 2 , 3104 antymonite Sb2S 3 120 1,3 molybdenite MoS2 110 1,3
heazlewoodite Ni 3S 2 – 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
ulat
ive
reco
very
of t
he r
emai
ning
co
mpo
nent
s in
the
taili
ngs,
%
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
ulat
ive
reco
very
of t
he r
emai
ning
co
mpo
nent
s in
the
taili
ngs,
%
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
reco
very
, % malachite
12
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).
Table 12.38. Influence of structure of silicates on their flotation with anionic and cationic collectors (after Manser, 1975)
Silicate groupCollector
orthosilicates pyroxene amphibole frameAnionic good week none noneCationic satisfactory* satisfactory * good very good
* Flotation depends on pH
2 4 6 8 10 12pH
0
20
40
60
80
100flo
tatio
n re
cove
ry, %
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
adso
rptio
n de
nsity
, mol
/cm
2 x
104
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
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
conc
entr
atio
n, k
mol
/m3 )
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
conc
entr
atio
n, k
mol
/m3 )
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 14pH
0
20
40
60
80
100re
cove
ry, %
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
50ad
sorp
tion
dens
ity, m
ol/m
2 x1
011
0
20
40
60
80
100
-100
-60
-20
20
60
100quartz-dodecylamine
zeta
pot
entia
l, m
V
cos
0.80
0.90
flota
tion
reco
very
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
100flo
tatio
n re
cove
ry, %
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 14pH
0
20
40
60
80
100re
cove
ry, %
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 14pH
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
reco
very
, %
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 < 8Streminal 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 3–12Rokanol 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 12pH
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
100flo
tatio
n re
cove
ry, %
KClK2SO4 Na2SO4×10H2O
Na2SO4 NaCl
Soluble salts
0 50 100 150 200 250dosage of depressor, g/Mg
0
20
40
60
80
100
reco
very
, %
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