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FLOTATION
(Main feature - hydrophobicity)
Flotation
water
gas bubble
intergroth
hydrophobic particle
hydrophilic particle
płonna (hydrofilna)
gas bubble
water
particle
Contact angle
Contact angle of selected materials
( degree)
Table 12.2. Advancing contact angle ( in degree) mesured on polished plates
(after Adamson, 1967; data from other sources denoted as *)
Substance
Teflon
Paraffin
Polystyrene
Human skin
Naphthalene
Stearic acid
Advancing contact angle
112
110
103
90
88
80
Substance
sulfur
graphite
stibnite (Sb2S3)
iodyrite (AgI)
calcite (CaCO3)
glass
Advancing contact angle
86*
86
84
17
~0*
~0
Table 12.3. Methods of contact angle measirement
Smoothly polished
surfaces
Capture bubble
Adamson, 1967
heat of immersion
Sessile drop
Adamson, 1967
flotometry
Tilted plate in liquid
Hiemenz, 1986
Force of detachment
Hiemenz, 1986
Wetting of plate
Adamson, 1967
Drop on a tilted plate
Hiemenz, 1986
Drop shape
Drop size
Source*
Ralson
i Newcombe, 1992
Ralson
i Newcombe, 1992
Methods of measurement
Additional source: Neumann i Good (1979).
Particles
Source
Neumann and Good, 1979
Drzymała and Lekki, 1989a,b
Drzymała, 1995; 1999a,b,c
shape of border between
Aveyard and Clint, 1995
phases
levitation
Li and współ., 1993
Heertjes and Kossen, 1967,
pressed disc
He and Laskowski, 1992
rate of penetration of a
van Oss and współ., 1992
thin layer of particles
rate of penetration of a Washburn, 1921, Crowl
column of particles
and Wooldridge, 1967
captured bubble for
Hanning and Rutter, 1989
particles
Clint and Tylor, 1992;
Langmuir through
Aveyard and współ., 1944
Huethorst and Leenaars,
centrifuge
1990
capillary rise without
White, 1982
probe liquid
capillary rise in column
of particles with probe Bartell and Whitney, 1933
liquid
Table 1. Hydrophobicity of materials. Contact angle is in degrees and is based on
flotometric measurements
Strongly
hydrophobic
weakly hydrophobic
hydrophobic*
Material
Material
Material
1
2
3
4
5
6
Paraffin
90+ sulfides
44–0 fluorite, CaF2
10–13
CnH2n+2
silicon carbide
Teflon, C2F4
90+
27,6 arsenic, As2O3
9,3
SiC
26–0 perovskite, CaTiO3
ironsilicon
dolomite
CaMg(CO3)2
magnetite
Fe3O4
Sulfur, S
63,2 coal
Mercury, Hg
45,6 indium, In
Germanium,
Ge
39,7 iodyrite, AgI
23,5 diamond, C
7,9 halite, NaCl
Silicon, Si
35,4
cassiterite,
SnO2
35,2 silver, Ag
ilmenite, Fe
molybdenite,
MoS2
22– tin, Sn
7,5 brawn coal
Talc
25
14
14
scheelite, CaWO4
boric acid, H3BO3
graphite, C
5,9+ PbJ2
gold, Au
barite, BaSO4
corundum, Al2O3
HgO
HgJ2
copper, Cu
9
hydrophilic**
=0
Material
7
gypsum
CaSO4·2H2O
9
6,4 kaolinite
6,2+ hematite, Fe2O3
6
quartz, SiO2
5
calcite, CaCO3
anhydrite,
5
CaSO4
4 bones
3,3 tourmaline
3 vegetables
3 iron, Fe
amber
ice, D2O
* Flotometric method is able to measure contact angles smaller than 90 o.
** Other hydrophilic materials: chromite, malachite, smithsonite, azurite, rutile, zircon, mica
sg = sc+ cgcos
The Young equation
s - = sc+ cgcos
g
cg
vapor adsorption
liquid drop cieczy
scg
c
x x x x x x x x x x
sg
x x x x x
s s
Table 12.4. Contact angle determined directly from the Young equation
Contact angle in degrees (Drzymała, 1994)
Substance
Ice
Quartz
Paraffin
Mercury
s, mN/m
e, mN/m
sw, mN/m
cg, mN/m
calculated
measured*
90–120
120–135
50– 68
484
~0
~small
0
~75
22–33
46
51
415
72,8
72,8
72,8
72,8
0
~0
77– 91
95
0
0
110
43–110
Influence of pH (electrical properties) on flotation
100
uzysk flotacji, %
80
Ge
pHiep = 2,8
60
40
20
0
0
2
4
6
pH
8
10
12
Structure of electrical double layer
+ - + - + - +
charged surface
layer
+
-
+
+ - + -
+ - + - +
- - + - + particle
+
- + - +
+
- + - + +
+
- + - +
-
Galvani potential, 0
- + - +
potential
diffusive layer
surface potential 0
potential zeta,
cation concentration
eg. [H+] = [H+] r exp ( /RT)
anion concentration
eg. [OH-] = [OH-] r exp ( /RT)
Models of electrical double layer
Helmholz
(flat condenser)
Gouy-Chapman
(diffuse layer)
o
o -o
H+
OH-
o
o d -----
H+
OH-
0 = 0 0
d
triple
layer
Stern
(rigid and diffuse layer )
quadruple
layer
Grahame
(binding sites)
o
i
o i
H+
OH-
d-----
o
i
o
i
d
d
o i d----
H+ K+
OH- A-
o
o
o i j d
H+ K+ K+H2O
OH- A- A-H2O
Flat condenser
2 kT 0
ze
sinh 0 0
ze
2kT
Diffuse condenser
Formation of electrical double layer
surface charge
negative
positive
metals
ęć
Me Me Me
Me
Me Me Me
Me
Me Me Me
Me
oxides
Me O Me O
O Me O
Me
Me O Me O
salts
H2O
H2O
Me X Me X H2O
X Me X
Me
Me X Me X
placeof particle
breakage
Me
Me
Me
Me
Me
Me
+ n Me+ or Me
Me
Me
Me
Me
O
O MeO
Me OH
+ n H+ or
O MeO
Me X
X
Me X
+ electrons
MeOH2+
Me OH
O
+ n OH-
MeOH2+
+n
Me+
particle /water interface
or
X
Me
Me+
X
Me
+n
X-
Formation of electrical double layer
lad
Me S Me
S Me S
Me S Me
S
H 2O
Me
S
S Me OH
Me SH
S Me OH
other
S Me OH 2
Me SH
+
S Me OH 2
+
+ n OH
-
S Me OH
Me S
S Me OH
+H
+
surface electrical charge, µC/cm 2
60
40
pzc
20
0
-20
0,001M NaCl
0,01M NaCl
-40
0,1M NaCl
-60
2
4
6
pH
8
10
60
zeta potential, mV
40
iep
20
0
-20
0,1M NaCl
0,01M NaCl
-40
0,001M NaCl
-60
2
4
6
pH
8
10
Table 12.11. Point of zero charge (pzc) and isoelectric point (iep)
for selected substances in aqueous solution. A collection of pzc and iep
for a great number of solids can be found in a work Parks (1965)
Substance
Quartz, SiO2
Oleic acid, C17H33COOH
Cassiterite, SnO2
Sulfur, S
Sulfides, MeS
Ice, D2O
Hydrocarbons, CnH2n+2
Air, O2+N2+CO2
Diamond, C
Bacteria (Nocardia)
Rutile, TiO2
Ilmenite, FeTiO3
Hematite, Fe2O3
Barite, BaSO4
Tenorite, CuO
Dolomite, (Ca,Mg)CO3
Magnesite, MgCO3
Corundum, Al2O3
Periclase, MgO
pHpzc
<5
<5,5
–
–
7,0 0,5
6,3
–
–
–
4,8–5,3
5,6
6,5–8,5
–
6,5–8,5
–
pHiep
1,54
2,0
2,0–5,5
2,1
2,1–7,0
3,0–3,5
3,3
3,5
3,5
3,5
4,8–8,7
6,0–8,1
6,0–7,6
7,5
7,5
9,1
12,0
collectors
non-polarne
ionic
chelat ing
simple
sulfur
compounds
hydrocarbons
and derivatives
alcohols
typu S-S
xanthates
cationic
typu O-O
fatty acids
typu N-N
diamines
typu S-N
carbamines
anionic
amphoteric
typu O-S
monothiocarbonates
typu O-N
oximes
amines
merkaptans
aminoalkylacids
hydrophobization
b
oil
a
-O-H -O
d
c
Me
S
Me
S
S
Structure of
collector
CH3CH2CH2CH2 CH2CH2CH2CH2
COO–
tail
(hydrophobic)
head
(hydrophilic)
100
contact angle, , degree
contact angle, degree
80
60
40
galena
20
80
pH = 7
pH = 9
60
pH = 10
40
pH = 10.5
20
hematite - NaOl
0
0
2
4
6
8
10
concentration of potassium ethyl xanthate, g/m3
0 -07
10
10
-06
10
-05
10
-04
-03
10
concentration of sodium oleate, kmol/m3
collector renders the
surface hydrophobic
gas
collector
particle
Influence of pH and iep on flotation for various collectors
100
100
goethite
80
kyanit
(collector: oleic acid)
60
recovery, %
recovery, %
80
40
iep 6.9
20
collector
RSO4Na
60
iep 6,7
40
20
0
0
0
2
4
6
8
10
12
2
14
4
6
100
8
10
12
pH
pH
100
coal
80
quartz
80
(collector: tridecane)
(collector: octylphenylpolyethoksyethanol)
recovery, %
recovery, %
collector
RNH3Cl
60
40
60
40
iep 2 3
20
iep 2 3
20
0
0
2
4
6
8
pH
10
12
2
4
6
8
pH
10
12
Table 12.15. Apolar collectors
Collector
Hydrocarbons and derivatives
Sulfur compounds
Alcohol and derivatives
Example
fuel oil, naphtha, heptane, benzene, halogen derivatives
of hydrocarbons
dixantogen (R–O–C(=S)–S–)2
formic xanthate R–O–C(=S)–S–C(=O)–O–R´, alkyl
disulfides R–S–S–R
alkylfenyl(polyethoxy) alcohols (Triton, Tergitol, Brij),
alkylphenols, higher alcohols
Collectors
ANIONIC
Alkyl mercaptan
R-S-H
Alkyl dithiocarbonate (xanthate)
R-O-CS-S-Na
Dialkyl disulide (dixanthogen)
R-O-CS-S-S-CS-O-R
Xanthgen formates
R-O-CS-S-CO-O-R’
Dialkyl dithiocarbamate
RR-N-CS-S-Na
Dialkyl dithiophosphate
RO(RO)-PS-S-Na
Carboxylate (fatty acids)
R-CO-O-H
Alkyl sulfate
R-O-SO3H
Alkyl sulfonate
R-SO3H
CATIONIC
Amine
R-NH2, RR-NH, RRR-N
Quaternary Amine
Cl- R+RRR-N