Research ArticleCHEMICAL ENGINEERING

Sacrificial amphiphiles: Eco-friendly chemical herders as oil spill mitigation chemicals

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Science Advances  26 Jun 2015:
Vol. 1, no. 5, e1400265
DOI: 10.1126/sciadv.1400265
  • Fig. 1 Cartoon showing the herding process.

    (A) Top view shows the sequence of events starting from the spill of oil on water surface followed by the addition of 20 μl of herder delivering 2.34 mg of herder based on the standard dose of 150 mg/m2 with a micropipette, altering the interfacial forces at the edge of oil slick and thus retracting the oil slick. (B and C) Side view of the herding process in terms of spreading coefficient and interfacial tension. (B) A positive value of spreading coefficient (S) refers to the spreading of crude oil onto seawater surface. (C) Application of herder at the edge of oil slick lowers the air-seawater interface causing a retraction of the oil slick with S < 0.

  • Fig. 2 Chemical design of proposed green herders.

    (A) 1-Methyl-3-(2-oxo-2-((phytyl)oxy)ethyl)-1H-imidazol-3-ium bromide (PIm); (B) 1-(2-oxo-2-((phytyl)oxy)ethyl)pyridin-1-ium bromide (PPy). Red color indicates the phytol tail for optimum lipophilicity; green color indicates the ester bond next to allyl bond triggering quick hydrolysis to make it sacrificial; blue color shows the cationic head for a variety of interactions like electrostatic, π-π, and hydrogen bonding that help in locking the herder at the air-water interface.

  • Fig. 3 Pictorial presentation of the herding process of crude oil in the laboratory to mimic real oil spill conditions.

    (A) Real photographs of the herding process. (a) Water filled in a tray up to 2 cm deep representing oil-free water surface. (b) Macondo crude oil (2 ml) was added on the water surface to create an oil spill scene. (c) Instantaneous shrinking of oil slick after herder injection. (d) Further shrinking of oil slick until 10 min of herder injection. (B) Conversion of a digital photograph to a binary picture to determine the area of oil slick (total number of black pixels divided the by the number of pixels per unit area in the original image, using ImageJ).

  • Fig. 4 Evaluation of green herder’s effectiveness as a function of time, temperature, and water salinity.

    (A to C) Change in thickness for PIm and PPy in freshwater (FW) and saline water (SW) at 5°C (A) and 20°C (B) and only in freshwater under a warm condition (35°C) (C). (D) Change in thickness for Silsurf and PIm in saline water at 5°C mimicking cold water conditions.

  • Scheme 1 Preparation of green chemical herders from plant-derived phytol molecule using a simple two-step procedure.

    1, Synthesis of phytyl-2-bromoacetate (bromoacetic acid, 68°C, 22 hours); 2, quaternization of heterocyclic amine, that is, N-methyl imidazole or pyridine (CHCl3, 2 hours) resulting into phytol-based cationic amphiphiles (a) 1-methyl-3-(2-oxo-2-((phytyl)oxy)ethyl)-1H-imidazol-3-ium bromide (PIm) and (b) 1-(2-oxo-2-((phytyl)oxy)ethyl)pyridin-1-ium bromide (PPy).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/5/e1400265/DC1

    S1. Synthesis of saturated analog.

    S2. Herding efficiency in terms of herding dynamics.

    S3 to S5. Determination of surface tension and interfacial tension using the pendant drop method.

    S6. Hydrolysis proof from mass spectroscopy.

    S7. ImageJ computer program.

    Fig. S1. Reaction scheme of the synthesis of hexadecylpyridinium bromide.

    Fig. S2. Evaluation of the herding efficiency by fitting the area of oil slick obtained at 20°C in freshwater as a function of time.

    Fig. S3. Air-water surface tension for PIm using a pendant drop tensiometer.

    Fig. S4. Toluene-water interfacial tension for PIm using Pendant drop tensiometer.

    Fig. S5. In situ air-water surface tension of PIm using a Wilhelmy plate tensiometer.

    Fig. S6. ESI-HRMS of PPy at the beginning, after 8 days, and after 1 month.

    Fig. S7. Representative example of calculating the thickness of oil slick using ImageJ computer program.

    Table S1. Data obtained for different images of an oil slick spread over freshwater at 20°C in a plastic tray; PPy was used as a chemical herder to retract the oil slick.

    Movie S1. Oil herding experiment at the lab scale mimicking an oil spill scenario.

  • Supplementary Materials

    This PDF file includes:

    • S1. Synthesis of saturated analog.
    • S2. Herding efficiency in terms of herding dynamics.
    • S3 to S5. Determination of surface tension and interfacial tension using the pendant drop method.
    • S6. Hydrolysis proof from mass spectroscopy.
    • S7. ImageJ computer program.
    • Fig. S1. Reaction scheme of the synthesis of hexadecylpyridinium bromide.
    • Fig. S2. Evaluation of the herding efficiency by fitting the area of oil slick obtained at 20°C in freshwater as a function of time.
    • Fig. S3. Air-water surface tension for PIm using a pendant drop tensiometer.
    • Fig. S4. Toluene-water interfacial tension for PIm using Pendant drop tensiometer.
    • Fig. S5. In situ air-water surface tension of PIm using a Wilhelmy plate tensiometer.
    • Fig. S6. ESI-HRMS of PPy at the beginning, after 8 days, and after 1 month.
    • Fig. S7. Representative example of calculating the thickness of oil slick using ImageJ computer program.
    • Table S1. Data obtained for different images of an oil slick spread over freshwater at 20°C in a plastic tray; PPy was used as a chemical herder to retract the oil slick.

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