adhesion of particles or particles to surfaces
DESCRIPTION
SLIME COATING AND COAGULATION. adhesion of particles or particles to surfaces. Slime coating. AFM-images of slime coatings on mineral surface. M.E. Holuszko et al., Minerals Engineering, 21, 2008, 958-966. Slime coating. Very important phenomenon. Can be useful and harmful. - PowerPoint PPT PresentationTRANSCRIPT
adhesion of particles or particles to surfaces
SLIME COATING AND COAGULATION
Slime coating
AFM-images of slime coatings on mineral surface
M.E. Holuszko et al., Minerals Engineering, 21, 2008, 958-966
Slime coating Very important phenomenon
Can be useful and harmful
Ferric oxide slime and flotation of quartz with 10-4 M dodecyl ammonium acetate
Chemistry of flotation , M.C. Fuerstenau, J.D. Miller, M.C. Kuhn, AIMM, 1985
Chemistry of flotation , M.C. Fuerstenau, J.D. Miller, M.C. Kuhn, AIMM, 1985
Alumina as slime on galena and flotation with xanthate
coagulation
homocoagulation heterocoagulation
main parameter: stability ratio W
Process delineation (thermodynamics)
+ =
Gk = Gh – G
Gk = Gk d + Gk el + Gk s + Gk inne
That is components: dispersion (d), electrical (el),
structural (s), a others
H
RAVGG A
ddk 12
132132,
Dispersion interactions
H – distance between particles, m R – diameter of particle, m A132 – Hamaker constant, J
+ =
phase 1 phase 2phase 3
Dispersion interaction
Interacting objects Formula Units
Two atoms 6H
CGd (C is a constant) J
Two spheres )(6
)(
21
21
RRH
RRAG xd
x J
Two flat parallel slabs 212 H
AG xd
x
J/m2
Sphere and slab H
RAG xd
x 6 J
Two perpendicular cylinders H
RRAG xd
x 621 J
Hamaker constantDispersion interaction .Hamaker constant A11 for selected materials
collected by Drzymala (1994) and other authors
Material A11
(×1020 J)
A11 (×1020 J)
Material A11
(×1020 J) n-pentane (C5H12) 3,8b mica 10,0b MoS2 (molibdenite) 13,3e, 9,1c
Teflon ([C2F4]n) 3,8b MgO (periclase) 10,5c S (sulfur) 23c Acetone (CH3COCH3) 4,1b CaCO3 (calcite) 10,1d Fe2O3 (hematite) 23,2a Ethanol (C2H5OH) 4,2b AsS (realgar) 12c C (graphite) 23,8a
Water (H2O) 4,38a FeS2 (pyrite) 12c SnO2 (cassiterite) 25,6a
n-octane (C8H18) 4,5b CaO (lime) 12,5c Si (silicon) 25,6a
n-dodecane C12H26 5,0b FeCr2O4 (chromite) 14c FeAsS (arsenopyrite) 27c n-tetradecane (C14H30) 5,0b ZnS (sphalerite) 14c As2S3 (auripigment) 28,4a 15c Benzene (C6H6) 5,0b CdS (greenockite) 15,3f C (diamond) 28,4a
n-heksadecane (C16H34) 5,1b Al2O3 (corundum) 15,5a Cu (copper) 28,4a Cyklohexane (C6H12) 5,2b AgI (iodirite) 15,8a Ge (germanium) 30,0a
KCl silvine 6,2a Sb2S3 (metastibnite) 16c TiO2 (rutyl) 31,0a CnH2n +2 (paraffin) 6,3–7,3a SiO2 (quatz) 16,4a PbS (galena) 33c
Polystyrene 6,5b BaSO4 (barite) 16,4a Ag (silver) 40,0a CaF2 (fluorite) 7,2 TiO2 (anatase) 19,7a Hg (mercury) 43,4a Bornite (Cu5FeS4) 7,4c Cu2S (chalcocite) 21c Au (gold) 45,5–50a
Poli(vinyl chloride) 7,5b Fe (iron) 21,2a CuS (covelline) 2,8c (?)
Pirrothite (FeS) 8,4c Pb (lead) 21,4a [Fe, Ni]9S8) pentlandite 3,3c (?) Talc (Mg3[(OH)2Si4O10])
9,1c Sn (tin) 21,8a CuFeS2 (chalkopyrite) 3,3c (?)
a) Visser (1972), b) Israelachvili (1985), c) Lins i współ. (1995), d) Hunter (1987), e) Ebaadi (1981), f) Krupp et al., (1972). Symbol ? denotes uncertain data
221112 AAA
23311133311313131 2 AAAAAAA
33223311132 AAAAA
132131132 AAA
Dispersion interaction
Electrostatic interaction
,)2exp(1ln
)exp(1)exp(1
ln)(
2)(
)(22
21
21
21
22
21210
el
H
HH
RRRR
VG R
1 – particle electrostatic potential, V, 2 – the other particle electrostatic potential, V, R1
– particle radius, m, R2 – the other particle radius, m, – dielectric constant (usually water)0 – dielectric permeability in vacuum, 8,854187817·10–12 C2 N–1 m–2 1/ – Debye radius (thickness of ewp), m,
H – distance between interacting objects, m.
Electrostatic interaction
Approximate formulas for energy of electrostatic interactions Gel = VR between objects having different geometry in medium of a given dielectric constant
(Russel i et al., 1989)
Geometry limitation interaction energy VR
Two parallel slabs overlap )exp()25,0(tanh64 21 HkTne
Two spheres constant potential ])exp[1(ln2 22
0 HRze
kT
Two spheres constant charge ])[exp1(ln2 20
2
0 HRze
kT
Two spheres linear overlap )(exp2
4 222
0 HRH
R
ze
kT
Two spheres overlap )(exp)25,0(tanh32 22
0 HRze
kT
l
HE
l
HKlG SS expexp 0
l
HlRKGS exp*
For flat particles
For spherical particles
K , K* , Eso- constants
l - parameter correlating standing for thickness of oriented water molecules at the surface of particle
H - distance between particles
R - radius of particles
Structural interaction
Total interaction In
tera
ctio
n e
ner
gy, V
+
–
VR
VA
distance, H
VS, w
VS, h Vt = VR + VA + VS
DLVO
iner
acti
on e
ner
gy, V
t
+
–
Vmax
VI
VII
Vmax – energy barrier
VII– secondary minimum
VI – primary minimum
distance, H
Total interaction
Stability ratio W
R
t drkTV
rRW
22 exp
12
kTV
RW maxexp
21
ncoagulatio toleading collisions ofnumber particlesbetween collisionsofnumer W
iner
acti
on e
ner
gy, V
t
+
–
Vmax
VI
VII
Vmax – energy barier
VII– secondary minimum
VI – primary minimum
distance, H
Time of half-life t1/2 of hypothetical emulsion containing 1 m droplet and having energy barrier Vmax one radius apart from the
droplet surface (after Friberg, 1991)
Energy barrier Vmax /kT
(in kT units) t1/2
Stability ratio W = exp[0,92{(Vmax/kT) – 1}]
(for (Vmax/kT) 3)*
0 0.8 sec ~2
10 2.0 h 3.94·103 15 1.3 d 3.92·105
17.5 154 d 3.91·106
20 5.1 y 3.90·107
50 5.5·1013 y 3.78·1019
* Empirical equation of Prieve and Ruckenstein (1980).
Pstab
Vmax
W
VA,VR,VS
A, , , x, , H
ni, , ,cs,pH,
.....
Pa
Pz
xc / xj hd
V*max H, cs
Pk = PzPaPstab
Main parameter: stability ratio W
2 4 6 8 10 12
pH
50
70
90
110
130
150
turb
idit
y,
TiO2
2×10-3 NaCl
2×10-2 NaCl
2×10-1 NaCl
2 4 6 8 10 1240
60
80
100
stab
ilit
y, m
t = 5
min
/ mt =
0 m
inx1
00%
iep SiO2 iep Fe3O4 iep BaSO4
SiO2
BaSO4
Fe2O3
pH
selective coagulation
0 2 4 6 8 10 12
pH
-1
0
1
2
3
soli
ds
con
cen
trat
ion
, %
iep SiO2 iep Fe2O3
selective coagulation
0 2 4 6 8 10 12
pH
-1
0
1
2
3so
lid
s d
ensi
ty, %
Fe2O3 + SiO2
selective coagulation of hematite
heterocoagulation
stability
selective coagulation
2 4 6 8 10 12pH
0
20
40
60
80
100
coal
rec
over
y, %
0
3
6
9
12
15
ash con
tent, %
stability
recovery
ash
heterocoagulation
coal coagulation