Investigation of Oil-Mineral Aggregates Formation and the Effect of Minerals

1. Investigation of Oil-Mineral Aggregates Formation and the Effect of Minerals HaipingZhanga, 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 Canada c Minerals Management Service, US Department of Interior June 7, 2010

2. Outline • Introduction • Experimental and results Factorial experimental design Significant factor investigation Mineral effect study • Conclusions • Future work 2

3. Introduction Oil-Mineral Aggregates (OMA) Impact of oil spills * Oil in OMAs is easily transported into the water column. OMAs can accelerate biodegradation of oil associated. Oil spills in the sea has caused serious problems to the marine lives and sea environment. * Ajijolaiya, L.O., Hill, P.S., Islam, M.R., 2007. Energy Sources, Part A, 29, 499–509. 3

4. Our work • Investigation on OMAs suspended in water column • Factors: • mineral type • mixing energy • dispersant • Mineral effect investigation • Natural minerals • Modified minerals (Hydrophobicity)

5. Experimental Flow chart of OMA experiments

6. Table 2: Crude oils used in this study Factorial experiment design Table 1: Experimental conditions for the laboratory examination of OMAs 6

7. Factorial experimental results Fig.1 The effect of dispersant (a), mixing energy (b), and mineral type (c). c R-value: difference between two levels Dispersant 57.0-64.8%>Mixing speed 14.6-24.1% ≈Mineral 13.7-17.4%. Dispersantis the most significant factor, following by the mixing speed and mineral types. 7

8. Significant factor-dispersant (MESA oil) a 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. a) at 250rpm b) at150rpm 8

9. Natural minerals Table 3 Contact angle of natural minerals More hydrophilic minerals: Kaolin, Diatomite, Fly ash More hydrophobic mineral: Graphite Fig.3 Physical properties of natural minerals 9

10. Natural minerals • 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 . Fig. 4 The effect of mineral type for MESA oil • 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

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

12. For both static methods, the oil-binding capacity of modified Kaolin #1 was shown dramatically enhanced. These results suggest that there was an optimal range of hydrophobicity of minerals, within which the interaction between oil and minerals could be enhanced. Modified kaolin #2 with high hydrophobic level, reversely, was less effective in binding oil. Static for a short time (modified kaolin #1) Static for 60 min b) Static for 60min, without dispersant 12 Fig. 7 Oil distribution for modified kaolin

13. OMA images by confocal microscopy c b a Mineral Oil 10μm 20μm 10μm e d f f 20μm 10μm 20μm 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. • 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. 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. 13

14. Particle size distribution a 100μm b 100μm Fig.10 Number droplet size distribution. Fig. 9 OMAs by uvepi-fluorescence microscope a) kaolin, 250rpm, after sedimentation of middle part; b) modified kaolin #1, 250rpm, after sedimentation. 14

15. 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

16. 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

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