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

3

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

4

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 Dispersant1 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

1020304050607080

MESA 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

porti

on (%

)

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)

Aver

age

parti

cle

size

(μm

) Su

rfac

e ar

ea (m

2/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)

11

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(°)

Aver

ge p

artic

al si

ze (μ

m)

Surf

ace

area

(m2/

g) Contact angle (°)

Modified Kaolin #1Kaolin

Modified 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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