The stability of crude oil droplets formed by adding chemical dispersants can be considerably enhanced by the use of the biopolymer, hydrophobically modified chitosan. Turbidimetric analyses show that emulsions of crude oil in saline water prepared using a combination of the biopolymer and the well-studied chemical dispersant (Corexit 9500A) remain stable for extended periods in comparison to emulsions stabilized by the dispersant alone. We hypothesize that the hydrophobic residues from the polymer preferentially anchor in the oil droplets, thereby forming a layer of the polymer around the droplets. The enhanced stability of the droplets is due to the polymer layer providing an increase in electrostatic and steric repulsions and thereby a large barrier to droplet coalescence. Our results show that the addition of hydrophobically modified chitosan following the application of chemical dispersant to an oil spill can potentially reduce the use of chemical dispersants. Increasing the molecular weight of the biopolymer changes the rheological properties of the oil-in-water emulsion to that of a weak gel. The ability of the biopolymer to tether the oil droplets in a gel-like matrix has potential applications in the immobilization of surface oil spills for enhanced removal.

Spherical ironÀcarbon nanocomposites were synthesized through a facile aerosol-based process and a subsequent carbothermal reduction. The distribution and immobilization of iron particles throughout the carbon microspheres prevents nanoiron aggregation, allowing the maintenance of particle reactivity. The carbon microspheres allow adsorption of TCE, thus removing dissolved TCE rapidly and facilitating reaction by increasing the local concentration of TCE in the vicinity of iron particles. The strongly adsorptive property of the composites may prevent release of toxic chlorinated intermediate products. The nanoscale composite particle size is in the optimal range for effective transport through groundwater saturated sediments. It is also shown that carbothermal treatment of the composite material leads to highly porous carbon materials containing zerovalent iron species, a necessary reactive component in the reaction pathway. The mesoporous structure generated allows access to internal reactive sites.