Effectiveness of oil spill dispersants containing lecithin/Tween 80 (L/T) blends in ethanol was measured as a function of L:T ratio, surfactant:solvent ratio, solvent composition, and dispersant:oil ratio (DOR) using baffled flask dispersion effectiveness tests. Optimal L:T ratios are between 60:40 and 80:20 (w/w); at higher L:T ratios, effectiveness is limited by high interfacial tension, while at lower L:T ratios, insufficient lecithin is present to form a well-packed monolayer at an oil-water interface. These optimal L:T ratios retain high effectiveness at low DOR: 80:20 (w/w) L:T dispersant is 89% effective at 1:25 DOR (v/v) and 77% effective at 1:100 DOR (v/v). Increasing surfactant:solvent ratio increases dispersant effectiveness even when DOR is proportionally reduced to keep total surfactant concentration dosed into the oil constant. Replacing some of the ethanol with octane or octanol also increases dispersant effectiveness, suggesting that ethanol's hydrophilicity lowers dispersant-oil miscibility, and that more hydrophobic solvents would increase effectiveness.
Bibliographical noteFunding Information:
The authors are grateful to undergraduate researchers Sarah Downey and Prakash Paul for assisting David Riehm by running dispersion effectiveness tests, to Dr. Edith Holder of the USEPA and Drs. Tim Nedwed and Tom Coolbaugh of ExxonMobil for helpful discussions, and to the Mkhoyan group for the use of their UV–Vis spectrophotometer. This work was supported in part by a grant from the Gulf of Mexico Research Initiative (GoMRI) (Consortium for Ocean Leadership Grant SA 12-05/GoMRI-002 ) to the Consortium for the Molecular Engineering of Dispersants (C-MEDS). A digital version of the dataset supporting this paper is available through the Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC) at https://data.gulfresearchinitiative.org/ .
© 2015 Elsevier Ltd.
- Crude oil
- Oil spill
- Tween 80