The accidental release of natural crude oil into our marine waters and its subsequent effect on the environment is one of the major problems that the environmental protection agencies and coast guards of most countries worldwide have to deal with. In this study, the effectiveness on oil dispersions of a composite particle made of paraffin wax and the surfactant dioctyl sodium sulfosuccinate (DOSS) was compared to that of the same DOSS dissolved in a liquid solvent using the U.S. EPA's baffled flask procedure. Solid dispersant composite particles were prepared by ultrasonically spray freezing paraffin wax and DOSS molten solution while varying the mass ratio. The amount of DOSS in the composite particle was determined by the methylene blue complexation procedure. Liquid delivery of DOSS was accomplished by dissolving the surfactant in propylene glycol (PG). The results from the study showed that the dispersion effectiveness of the DOSS-paraffin wax composite particles were dependent on particle size, the solubility of the matrix material (paraffin wax) in the crude oil, and the DOSS-to-oil ratio (DOR, mg/g). This is because the paraffin wax would have to dissolve in the crude oil to release DOSS, which is then used for the dispersion of the crude oil. At 23 mg/g DOR, which was the maximum DOR used in the study, the dispersion effectiveness of the dispersant composite particles was 60 vol % and 62.6 vol % in the heavy Texas crude (TC) and the light crude (LC) oils, respectively. The dispersion effectiveness of the solubilized DOSS on TC was significantly higher than that of the dispersant composite particles; however, at DOR of 23 mg/g, the effectiveness of the dispersant composite particles on LC was just 1.8 vol 96 below that of the solubilized DOSS. There was a significant increase in the dispersion effectiveness when the mixing energy was increased from 150 to 200 rpm (rpm); nevertheless, the effectiveness was almost the same at 200 and 250 rpm. Dispersion effectiveness was analyzed at different salinity environments, that is, in brackish water (1.6 and 2.8 wt 96 salt concentration) and saline water (3.5 wt % salt concentration). The dispersant composite particles performed better at low salinities; however, the dispersion effectiveness almost leveled off at 2.8 and 3.5 wt % salt concentrations. The results of this study show the potential of dispersant composite particles to replace solubilized dispersants in oil spill remediation in the near future and, as a result, eliminate the environmental complications associated with the use of solvents in formulating traditional liquid dispersants.
