Monday, November 9, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
To reduce surfactant wastage and toxicity of oil spill dispersants, and increase dispersion effectiveness, halloysite clay nanotubes (HNTs) loaded with different combinations of surfactants were studied for possible application in crude oil spill remediation. Halloysite nanotubes were loaded with the surfactants Tween 80, dioctyl sodium sulfosuccinate (DOSS, D), Span 80 (S) and modified soybean lecithin phosphatidylinositol (Lecithin FPI, LFPI) by vacuum suction method. The HNT loaded with the surfactants were then characterized with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The release kinetics of nonionic and anionic surfactants from HNT were studied with the cobalt thiocyanate and methylene blue active substance tests, respectively. The dispersion effectiveness of the raw HNT and the surfactant-loaded HNT were examined using the U.S. EPA’s baffled flask test procedure. The release rate of DOSS from HNT was slower than that of Tween 80 due to the interaction of the anionic head group of DOSS with the positively charged lumen of the HNT. The dispersion effectiveness of the raw HNT was lower than the surfactant-loaded HNT, signifying the release of surfactants during the baffled flask test. For the dispersant formulated with a single surfactant loaded onto HNT, the highest and the lowest dispersion effectiveness were recorded by HNT loaded with Tween 80 (HNT-Tween 80) and HNT loaded with Span 80 (HNT-Span 80), respectively. Loading the HNT with binary surfactant mixtures improved the dispersion effectiveness. Notable among them was HNT loaded with DOSS and Tween 80 (HNT-DOSS-Tween 80) and HNT loaded with Lecithin FPI and Tween 80 (HNT-Lecithin FPI-Tween 80). The highest dispersion effectiveness values for all the dispersants formulated in this study were attained by HNT loaded with ternary surfactant mixtures. For example, a complete oil dispersion was obtained from HNT loaded with DOSS, Tween 80 and lecithin FPI (HNT-DOSS-Tween 80-Lecithin FPI), and HNT loaded with Span 80, Tween 80 and lecithin FPI (HNT-Span 80-Lecithin FPI). The blend of synthetic surfactant; DOSS, Span 80 and Tween 80 (HNT-DOSS-Tween 80-Span 80) recorded 96.2 vol.% dispersion effectiveness. An environmentally friendly oil spill dispersant was therefore formulated using naturally occurring HNT and FDA approved food grade surfactants (Span 80, Tween 80 and Lecithin FPI) with 99 vol.% dispersion effectiveness.