Abstract:
The dataset shows neutron scattering data and cryo-SEM micrographs of the Lecithin/Tween80/DOSS surfactant gel microstructure and optical micrographs of emulsions stabilized by the surfactant components. This dataset supports the publication: Owoseni, O., Zhang, Y., Omarova, M., Li, X., Lal, J., McPherson, G.L., Raghavan, S.R., Bose, A., and John, V.T. (2018). Microstructural characteristics of surfactant assembly into a gel-like mesophase for application as an oil spill dispersant. Journal of Colloid and Interface Science, 524: 279-288 doi: 10.1016/j.jcis.2018.03.089
Data Parameters and Units:
Table 1: Sample compositions prepared at varying PC to DOSS ratio. The PC to DOSS molar ratio was first varied from 0 to 1 with the total surfactant concentration fixed at 1.26M in hexadecane. The appropriate mass of each surfactant used in preparing the samples are summarized in Table 1. Mass of Tween 80 in gel-like system (g), percentage weight fractions of Tween 80 (αTween 80), percentage weight fractions of PC (αPC), percentage weight fractions of DOSS(αDOSS) , percentage weight fractions of amphiphiles (αs), percentage weight fractions of water (aqueous phace, αw), percentage weight fractions of hexadecane (oil phase, ao) Figure 1. (a) Photograph of the starting surfactant solution (PC and DOSS) and (b) representative photograph of gel-like system on addition of water and Tween 80. Table 2. Composition of gel-like surfactant system. All systems were prepared with 2.39g of L-α-phosphatidylcholine (PC), 1.40g of dioctyl sulfosuccinate sodium salt (DOSS), 5 mL of hexadecane and 2.5ml of water. Mass of Tween 80 in gel-like system (g), Total Surfactant Mass Fraction (αs, %), water mass fraction (αw, %), hexadecane mass fraction (αo, %), Total Surfactant mass fraction (ϕo, %), water mass fraction (ϕw, %), hexadecane mass fraction (ϕo, %). Figure 2. (a) Stability of crude oil-in-saline water emulsions prepared with PC/DOSS/Tween 80 gel-like system with increasing Tween 80 content. Surfactant system to oil mass ratio is 1:20 and oil to saline water ratio is 1:100. The systems were prepared with equimolar amounts of PC and DOSS in hexadecane. The columns are for images taken after 1 minute, 10 minutes and 30 minutes respectively (from left to right). The rows are for emulsions prepared with surfactant gel systems of varying Tween 80 content. From top to bottom PC/DOSS only; PC/DOSS/Tween 80 (11 wt%) and PC/DOSS/Tween 80 (27 wt%). Figure 2. (b) Turbidity of crude oil-in-saline water emulsions as a function of time and dispersant to oil mass ratio (DOR). DOR is the mass ratio of the gel-like surfactant system (dispersant) to the oil phase. The DOSS/PC/Tween 80 system has a Tween 80 content of 27 wt%. (Time in minutes, Turbidity in percent transmittance for no dispersant, DOSS/PC DOR 1:100, DOSS/PC DOR 1:20, DOSS/PC/Tween 80 DOR 1:100, DOSS/PC/Tween 80 DOR 1:20) Figure 3. (a-d) Instability of the interfacial surfactant film to droplet coalescence for Oil/Water emulsions prepared using surfactant system containing PC and DOSS alone. Figure 3a-3d are optical microscopy images taken after 2 minutes, 4 minutes, 6 minutes and 10 minutes of emulsion preparation (magnification used for optical microscopy was 10x/0.30 on a Nikon Eclipse LV100 Microscope, Scale bars = 100 μm) Figure 3 (e-f) Influence of Tween 80 addition into surfactant system on the resistance of the surfactant film against droplet coalescence. Dispersant to oil mass ratio is 1:20 and oil to saline water ratio is 1:50. Optical microscopy images taken after 2 minutes and 10 minutes of emulsion preparation (magnification used for optical microscopy in figure 3e – 3f was 50x/0.30 on a Nikon Eclipse LV100 Microscope, Scale bars = 10 μm) Figure 4a. Optical microscopy images of crude oil-in-saline water emulsions prepared with surfactant systems (dispersant) containing PC, DOSS and increasing amounts of Tween 80. Optical microscopy images were taken immediately after emulsion preparation. In Panel a, the Tween 80 content of the dispersants were 6 wt% (i), 11 wt% (ii), 20 wt% (iii) and 27 wt% (iv). Dispersant to oil mass ratio is 1:20 and oil to saline water ratio is 1:50. (Magnification used for optical microscopy was 10x/0.30 on a Nikon Eclipse LV100 Microscope). Figure 4b. Droplet size distributions obtained from optical microscopy images in Figure 4a. Droplet size in microns. Droplet size distribution for 6wt % Tween 80, 11wt % Tween 80, 20wt % Tween 80 and 27wt % Tween 80 systems. Figure 5. Crude oil–saline water interfacial tension measured by the pendant drop and spinning drop techniques. The surfactant system serves as the gel-like dispersant. Rows represent the interfacial tension (mN/m). Columns represent the dispersant to oil ratio (0, 0.01, 0.02, 0.05, 0.1, 0.2) of Increasing Tween 80 content (0 wt%, 6 wt%, 11 wt%, 27 wt%) of the dispersant system leads to a progressive decrease in crude oil-saline water interfacial tension at all the dispersant to oil ratios. Interfacial tension measurements were continuously taken until values were obtained to within 2 decimal places, thus some columns have more values than others. Figure 6. Surface oil dispersion using gel-like surfactant system. Gel-like system contains PC, DOSS and Tween 80. Tween 80 content is 27 wt%. (i) Oil is added to water surface (ii) Surfactant system (gel-like dispersant) is added to oil layer (iii) the system is mixed gently with a stirrer (iv) The oil is dispersed on input of sufficient mixing energy (v) Side-view of photograph in iii (vi) Side-view of photograph in iv. Figure 7. SANS data on a on a log-log scale for surfactant systems containing varying amounts of Tween 80 (Gel with 0 wt%, 6 wt%, 11 wt%, 20 wt%, 23 wt%, 27 wt% Tween 80) analyzed at 25 °C. To obtain quantitative structural information, the raw SANS data were fit by a sum of the power law and Teubner-Strey (TS) model functions using the sum model macro implemented in Igor Pro. Parameters for each fit are listed in Table 3. All systems were prepared with equimolar amounts of DOSS and PC in hexadecane. Power law q (1/Angstrom), Intensity (1/cm) and model fit for intensity (1/cm). SANS Research was done at Oak Ridge National Laboratory’s Spallation Neutron Source. Table 3. Fit parameters for the SANS data of the gel-like surfactant system (Tween 80 in gel [wt%], Low q Power Law Exponent [m], Low q Power Law Coefficient [Angstrom], Periodicity [d, Angstrom], Correlation Length [ξ, Angstrom], Amphiphilicity Factor [fa]) that were extracted from the modelling of raw SANS data in Figure 7. Figure 8. 31P NMR spectra of PC-DOSS-Tween 80 gel systems measured at 25 °C. The weight percent of Tween 80 in the gels are 0 wt%, 11wt% and 27 wt% respectively (y-axis is intensity in a.u, x axis is chemical shift in ppm). Figure 9. Representative cryo-scanning electron microscopy images of PC-DOSS gel system with increasing Tween 80 loadings of 0 wt% (9a - 9b), 11 wt% (9c - 9d) and 27 wt% (9e - 0h). All gels were prepared with equimolar amounts of DOSS and PC in hexadecane. Magnification in Figure 9a – 9h are; 9000x, 30000x, 15000x, 60000x, 4500x, 30000x, 6000x and 30000x respectively. Figure 10a. Angular frequency (rad/s), Storage moduli (Pa), Loss moduli (Pa), Complex viscosity (Pa.s) Figure 10b. Angular frequency (rad/s), Storage moduli (Pa), Loss moduli (Pa), Complex viscosity (Pa.s)
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