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Investigation of Oil-Mineral Aggregates Formation and the Effect of Minerals
Haiping Zhanga, Ying Zhenga*, Kenneth Leeb, Zhengkai Lib, Joseph V Mullinc
a Department of Chemical Engineering, University of New Brunswick
b Centre for Offshore Oil, Gas and Energy Research, Bedford Institute of Oceanography, Fisheries and Oceans
Canadac Minerals Management Service, US Department of
Interior June 7, 2010
Outline• Introduction• Experimental and results Factorial experimental design Significant factor investigation Mineral effect study
• Conclusions• Future work
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Introduction
Oil spills in the sea has caused serious problems to the marine lives and sea environment.
Impact of oil spills
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Oil-Mineral Aggregates (OMA)Oil in OMAs is easily transported into the
water column.
OMAs can accelerate biodegradation of oil
associated.
* Ajijolaiya, L.O., Hill, P.S., Islam, M.R., 2007. Energy Sources, Part A, 29, 499–509.
*
Our work
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Investigation on OMAs suspended in water column• Factors: • mineral type• mixing energy• dispersant
Mineral effect investigation
• Natural minerals• Modified minerals (Hydrophobicity)
Top part (~5ml), Flask & Funnel Washing
Middle part (~110ml)
Bottom part (~5ml)
Minerals &Saline waterShaking for 10min
Oil & Minerals & Saline waterShaking for 60min
Mixture Static for 60min
Flow chart of OMA experiments
Experimental
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Table 1: Experimental conditions for the laboratory examination of OMAs
No. of tests Factors
Mixing speed (rpm) Mineral Dispersant
1 150 kaolin 0
2 250 kaolin 1:25
3 150 diatomite 1:25
4 250 diatomite 0
Factorial experiment design
Crude Oils Specific gravity Kinematic viscosity (cSt)
MESA oil 0.8764 13.06
Alaska North Slope (ANS) oil 0.8746 10.82
Heidrun oil 0.9058 21.09
Table 2: Crude oils used in this study
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0:00 1:250
1020304050607080 MESA oil
ANS oilHeidrun oil
Dispersant-to-oil ratio (DOR)
Perc
enta
ge o
f cru
de o
il in
m
iddl
e po
rtion
(%)
a
150 2500
1020304050607080
MESA oilANS oilHeidrun oil
Mixing speed (rpm)
Perc
enta
ge o
f cru
de o
il in
m
iddl
e po
rtion
(%)
b
Kaolin Diatomite0
10
20
30
40
50
60
70
80MESA oilANS oilHeidrun oil
Perc
enta
ge o
f cru
de o
il in
m
iddl
e po
rtion
(%)
Fig.1 The effect of dispersant (a), mixing energy (b), and mineral type (c).
c
R-value: difference between two levelsDispersant 57.0-64.8%>Mixing speed 14.6-24.1% ≈Mineral 13.7-17.4%.
Dispersant is the most significant factor, following by the mixing speed and mineral types.
Factorial experimental results
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0:00 1:50 1:250
10
20
30
40
50
60
70
80
90
100Kaolin
Diatomite
dispersant only
Dispersant-to-oil ratio (DOR)
Perc
enta
ge o
f cru
de o
il in
mid
dle
por-
tion
(%)
0:00 1:250
20
40
60
80
100
Kaolin
Diatomite
Dispersant-to-oil ratio (DOR)
Perc
enta
ge o
f cru
de o
il in
m
iddl
e po
rtion
(%)
b
A significant increase in dispersed oil droplets can be seen in the middle portion with the application of dispersant, regardless mixing energy and mineral type.
Fig.2 The effect of dispersant for MESA oil.
b) at150rpm
a) at 250rpm
Significant factor-dispersant (MESA oil)a
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Natural minerals
Kaolin Diatomite Fly ash Graphite0
2
4
6
8
10
12Average particle size (μm)
Surface area (m2/g)
Ave
rage
par
ticle
siz
e (μ
m)
Surf
ace
area
(m2/
g)
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More hydrophilic minerals: Kaolin, Diatomite, Fly ash
More hydrophobic mineral: Graphite
Fig.3 Physical properties of natural minerals
Table 3 Contact angle of natural minerals
Blank Kaolin Diatomite Flyash Graphite02468
101214161820
Middle part
Bottom part
Prec
enta
ge o
f cru
de o
il (%
)
Natural minerals
Fig. 4 The effect of mineral type for MESA oil
Among the hydrophilic minerals, kaolin shows better performance, which has smaller particle size and larger surface area.
Having a similar size to diatomite, fly ash had a poorer performance than diatomite, due to the smaller surface area.
Particle size and surface area are playing an important role in OMA formation .
As a hydrophobic mineral, graphite has a poor performance on OMA formation. The high affinity of graphite and oil leads to high tendency to aggregate rather than stabilize oil as small droplets.
This result also indicated that affinity to oil and stabilization of small oil-mineral-aggregates are two important factors for minerals to form appropriate OMA.
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05001000150020002500300035004000
unmodified kaolin
Modified kaolin 1
Modified kaolin 2
2993
.028
77.3
1556
.3
NH
CH2
Modified Kaolin
TDI: toluene 2, 4-diisocyanate (TDI)
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0
3
6
9
12
15
0
10
20
30
40
50
60
70
80
90Average particle size (μm)Surface area (m2/g)Contact angle(°)
Ave
rge
parti
cal s
ize
(μm
)Su
rfac
e ar
ea (m
2/g) Contact angle (°)
Modified Kaolin #1
KaolinModified Kaolin #2
Fig. 6 FTIR spectra of modified kaolin
Fig.5 Properties of modified kaolin
Kaolin Modified kaolin#10
20
40
60
80
100Middle partBottom part
Perc
enta
ge o
f cru
de o
il (%
)
a) Static for a short time, without dispersant
Kaolin Modified kaolin#1
Modified kaolin#2
0
20
40
60
80
100
Perc
enta
ge o
f cru
de o
il (%
)
Fig. 7 Oil distribution for modified kaolin b) Static for 60min, without dispersant
Static for a short time (modified
kaolin #1)
Static for 60 min
For both static methods, the oil-binding capacity of modified Kaolin #1 was shown dramatically enhanced.
Modified kaolin #2 with high hydrophobic level, reversely, was less effective in binding oil.
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These results suggest that there was an optimal range of hydrophobicity of minerals, within which the interaction between oil and minerals could be enhanced.
Fig.8 a) droplet OMA with kaolin; b) multiple droplets OMA with kaolin; c) droplet OMA with diatomite; d) single OMA with modified kaolin #1; e) multiple OMAs with modified kaolin #1; and f) OMA with modified kaolin #2.
OMA images by confocal microscopy
The OMA sizes increased from a few µm (less than 20 µm) for original kaolin and diatomite to tens of µm (up to 100 µm) for modified kaolin.
Mineral Oil
a b c
ef
d f
20μm 10μm
20μm10μm20μm
10μm
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Fig. a-c show that spherical OMA were formed with hydrophilic minerals, and the minerals remained at the surface of oil droplets. When minerals were hydrophobic, the shape of OMA became irregular (Fig. d-f); the penetration of minerals into the oil phase was observed.
b
a
100μm
100μm
Particle size distribution
Fig.10 Number droplet size distribution. Fig. 9 OMAs by uv epi-fluorescence microscopea) kaolin, 250rpm, after sedimentation of middle part; b) modified kaolin #1, 250rpm, after sedimentation. 14
Conclusions Dispersant is the most significant factor in OMA formation. Particle size and surface area were important factors
influencing the OMA formation. Hydrophobicity of minerals plays an important role in mineral-
oil interaction and it can promote the affinity of minerals to oil and hence encourage the formation of OMA. A optimal range of hydrophobicity exists.
The OMAs formed with hydrophobic minerals (modified kaolin), with irregular shapes, are larger than hydrophilic minerals (kaolin and diatomite).
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Future work High sedimentation rate: Future study will be given to form suspended OMA:
adjusting the oil/mineral ratio to such that the density of OMA is closer to that of saline water, and investigating minerals that have lower densities and proper hydrophobic properties.
Optimal hydrophobic level Detailed work will be also given on the further
investigation of optimal range of hydrophobic level to maximize the oil-mineral interaction.
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Acknowledgements
• This work is financially and technically supported by Fisheries and Oceans (DFO) Canada and Natural Sciences and Engineering Research Council of Canada (NSERC).
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