AUXILIARY FLOTATION REAGENT
1. Activating reagents
2. Depressants
3. Others (they modify: pH, coagulation, redox, rheology,
etc.)
100
flotation recovery, %
80
60
Fe3+
Al3+
Pb 2+
M n2+
M g2+
Ca 2+
40
20
0
0
2
4
6
8
10
12
pH
Activating action of hydrolyzing cations. Flotation of quartz in the presence
of 10–4 M sulfonate (no flotation in the absence of those cations)
ber yl
f l ot at i on
100
no f l ot at i on
w i t h NaF
no f l ot at i on
10
1
dodecyl am i ne, m g/3dm
ol eat e, m g/ 3
dm
1000
1000
f l ot at i on ber yl
flot
atio
nw
ith
100
Na
F
10
no f l ot at i on
1
0
2
4
6
pH
8
10 12 14
0
2
4
6
8
10 12 14
pH
Fluoric ions may activate and depress flotation of silicates:
a – area of depressed flotation in presence of oleate
b) area of activation in the presence of dodecylamine as
collector (Manser, 1975)
Depressing reagents
Depressants acting through adsorption
Depressants acting through redox reactions
Depressants acting through reactions with flotation reagents
Depressors acting through adsorption
–MC + D = –MD + C
D
C
–MC
–MD
– depressant ion
– collector ion
– collector adsorbed or forming surface compound with mineral
– depressant adsorbed or forming surface compound with mineral
C  MD
KM 
D  MC
equilibrium const.
for bulk reactions
X 
OH 


y
 k,
C   MD K  const
D  MC M
Barski’s constant
(relation)
C
D y
 k.
 
X  exp  FRT
  S

K OH 
OH 
0

 2



 SMeOH
 F 0  2
exp 
  SH  SMeX  MCH 2 O
 RT 
equilibrium const.
for surface reactions
general form of Barski’ relation
Depressants acting through adsorption
X 
OH 


pH modifiers (acids and bases)
3
collector concentration, mg/dm
100
re c ov e ry , %
80
60
c h a lc o c ite
KButX 0. 0001M
40
20
0
2
4
6
8
10
12
pH
y
k
p y rite
0 .6
0 .5
g a le n a
0 .4
0 .3
c h a lc o p y rite
0 .2
0 .1
0
4
6
8
10
12
pH
too high and low pH depress flotation of minerals
based on attachment of partcles to bubble
Values of parameter y for selected mineral-collector system
(here pH regulator determines concentration of OH- ions
(after Chander, 1988)
Mineral – collector
y
pH range
Galena/KEX
0.65
9 – 12
Galena/KDEDTP
0.53
6–9
Sphalerite/DEDTC
0.56
6–8
Sphalerite/DBDTC
0.72
7.5 – 10
Sphalerite/DADTC
0.75
8 – 11
Chalcopyrite/NaDEDTP
0.71
8.5 – 11
Chalcopyrite/KEX
-
11 – 13
Pyrite/NaDEDTP
0.62
4–6
-
10 – 12
Pyrite/KEX
E - ethyl, D – di, T tio, A- amyl , B- butyl, X- xanthate , P - phosphate , C – carbonate, K- potassium, Na - sodium
In highly alkaline environment not working
X 
OH 


y
k
Redox depressants
Normal potential
Electrode reaction
Short notation
Eh0 (V)
S2 O82  + 2e = 2 SO 24 
S2 O82  / SO 24 
2.050
ClO– + 2H+ + 2e = Cl– + H2O
ClO–/Cl–
MnO 4 + 8H+ +5e = Mn2+ + 12H2O
MnO 4 /Mn2+
1.640
1.510
Cl2 +2e = 2Cl–
O2 + 4H+ + 4e = 2H2O
Fe3+ + e = Fe2+
O2 + 2e + 2H+ = H2O2
(CN)2 + 2H+ + 2e = 2HCN
Cl2/2Cl–
O2/O2–
Fe3+/Fe2+
O2/H2O2
(CN)2/HCN
Fe(CN)36 + e = Fe(CN)64 
Fe(CN)36 / Fe(CN)64 
Cu2+ + e = Cu+
2H+ + 2e = H2
Cu2+/Cu+
H+/H2
SO 24  + 2H+ + 2e = SO 32  + H2O
SO 24  / SO 32 
N2 + 4H+ + 4e = N2H4 (hydrazine)
S + 2e = S2–
Zn2+ + 2e = Zn
N2 /N2–
S/S2–
Zn2+/Zn
1.360
1.228
0.771
0.680
0.370
0.363
0.167
0.000
–0.103
–0.33
–0.10
–0.63
1
HCuO , CuO
22
2+
Cu
0 .8
CuO
-
0 .6
0
10
0 .4
2
potential Eh, V
1 0- 6
10
0
10
-4
10
-2
1 .2
1 0- 6
1 .4
0 .2
-2
-4
10
0
10
Cu 2O
-6
10
-0 .2
-0 .4
Cu
-0 .6
-0 .8
-1
0
2
4
6
8
pH
10
12
14
re c ov e ry , %
100
80
Cu2S
60
Cu5F e S4
Cu F e S
2
40
F e S2
20
0
-0 . 3 -0 . 2 -0 . 1
0
0 .1
0 .2
0 .3
0 .4
pote ntia l,
V
Relationship between flotation recovery of sulfides and potential applied to a
platinum wire immersed in aqueous suspension of a sulfide containing ethyl
xanthate at 1.44·10–5 kmol/m3. After Richardson and Walker, 1985
Depressants acting through reactions with flotation reagents
2C2H5OC(S)SK + 2K2SO3 + 2KHSO3 + 2O2  2C2H5OC(S)SOK 
2C2H5OH + 4K2S2O3 + 2CO2
Removal of xathates from sulfides
Depressants used in flotation
Inorganic depressant
Alum
Ammonia
Calgon
Sodium cyanide
Sodium dichromate
Phosphates
Sodium silicate
Fluoric acid
Sulfuric acid(IV)
Sulfuric acid(VI)
Hydrochloric acid
Sodium sulfate(IV)
Zinc sulfate(VI)
Caustic soda
Oxygen
Lime
Sodium carbonate
Sodium hydrosulfide
Formula
KAl(SO4)2
NH3
polyphosphates
NaCN
Na2Cr2O7
various
Na2SiO3
HF
H2SO3, SO2
H2SO4
HCl
Na2SO3
ZnSO4
NaOH
O2
Ca(OH)2
Na2CO3
NaHS
Organic depressant
starch
quebracho
tannin
lignin derivatives
synthetic polymers
acetic acid
dextrin
humic acid
cellulose derivatives
alginate
chitin derivatives
citric acid
hydrazine
thioglycolic acid
chelating compounds
electrons (redox substances)
t ur bi di t y,
Dispersion modifiers
Acids, bases, large organic ions
150
2 × 1 0- 3 Na Cl
130
2 × 1 0- 2 Na Cl
110
Ti O2
90
2 × 1 0- 1 Na Cl
70
iep
50
2
4
6
8
pH
10
12