Investigation of Oil-Mineral Aggregates Formation and the Effect of Minerals Haiping Zhang a, Ying Zheng a *, Kenneth Lee b, Zhengkai Li b, Joseph V Mullin c 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 Canada c 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 2

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., 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 water Shaking for 10min Oil & Minerals & Saline water Shaking for 60min Mixture Static for 60min Flow chart of OMA experiments Experimental 5

Table 1: Experimental conditions for the laboratory examination of OMAs No. of testsFactors Mixing speed (rpm)MineralDispersant 1150kaolin0 2250kaolin1: diatomite1: diatomite0 Factorial experiment design Crude OilsSpecific gravity Kinematic viscosity (cSt) MESA oil Alaska North Slope (ANS) oil Heidrun oil Table 2: Crude oils used in this study 6

Fig.1 The effect of dispersant (a), mixing energy (b), and mineral type (c). c R-value: difference between two levels Dispersant %>Mixing speed % ≈Mineral %. Dispersant is the most significant factor, following by the mixing speed and mineral types. Factorial experimental results 7

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 8

Natural minerals 9 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

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. 10

Modified Kaolin TDI: toluene 2, 4-diisocyanate (TDI) 11 Fig. 6 FTIR spectra of modified kaolin Fig.5 Properties of modified kaolin

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. 12 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 e f df 20μm 10μm 20μm 10μm 20μm 10μm 13  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 Particle size distribution Fig.10 Number droplet size distribution. Fig. 9 OMAs by uv epi-fluorescence microscope a) 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). 15

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. 16

Acknowledgements This work is financially and technically supported by Fisheries and Oceans (DFO) Canada and Natural Sciences and Engineering Research Council of Canada (NSERC). 17