(487d) Enhanced Effectiveness of Dispersants in Oil Spill Remediation Through the Use of Modified Polysaccharides

Dispersants are used in oil spill remediation to minimize harmful effects of floating oil on the environment. One of the key challenges in the treatment of oil spill with dispersant is to break oil slicks into stable small droplets which remain suspended in the water column and are biodegraded. COREXIT^® 9500, widely used dispersant in marine oil spills, typically reduces the oil-water interfacial tension by 2-3 orders of magnitude and is effective at creating small oil droplets with minimal energy. However, it does not provide an effective barrier against coalescence of the droplets. The objective of this research is to enhance effectiveness of dispersant through the application of environmentally benign biopolymers that greatly improve the colloidal stability and minimize the usage of the dispersant. We specifically focus on hydrophobically modified polysaccharides where alkyl groups are attached to the polymer backbone. We hypothesize that the hydrophobic side chains preferentially anchor themselves in the oil phase resulting in the formation of a protective polymer layer around the droplet. Cryogenic Scanning Electron Microscopy images of the colloidal dispersion of oil in saline water created by the use of dispersant and the biopolymer prove the presence of a polymer layer around oil droplets. The turbidimetric measurements of the dispersions confirm the significantly enhanced colloidal stability being consequent on a combination of biopolymer and a lower usage of the chemical dispersant. Interfacial tension measurements show that addition of hydrophobically modified biopolymers does not impact the reduction of oil-water interfacial tension. Measurement of zeta potential of the emulsions shows a reversal of charge on the oil droplet. The enhanced stability of the emulsion can be attributed to increased electrostatic repulsions as well as presence of polymer layer as a barrier to coalescence.

The molecular weight of the hydrophobically modified chitosan affects the viscosity of the emulsion significantly. We show that for high volume ratios of crude oil to water, high molecular weight modified chitosan was able to form an oil-in-water gel without the aid of the dispersant. Ability of the modified biopolymer to tether the oil droplets in a polymer gel matrix, as confirmed by cryo-SEM images, has a great potential in near shore oil spill remediation and under conditions of high volume ratios of oil to water.