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Phase-selective gelators were synthesized from sugar alcohols using biocatalysis. The gelators exhibited an unprecedented ability to phase-selectively gel only organic liquids including crude-oil fractions in the presence of water at room temperature. Oil can be recovered from the gelled phase by heating and distillation. Thus this class of materials may be useful in recovering oil from spills.
[Credit: Angewandte Chemie International Edition]
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All previously developed substances meant to selectively remove spilled oil from water and contain it have various disadvantages. These substances include dispersants that emulsify the oil, solid powders that adsorb the oil, and gelators that solidify the oil into a gel. In the past, polymers were primarily used, though they were difficult to mix with viscous types of oil and the retrieval of the bound oil was a very complex process. John and his colleagues propose a new class of gelators based on naturally occurring sugar alcohols. John lists the advantages, “They are inexpensive, easy to produce, nontoxic, and biodegradable.” Gelators are constructed so that their molecules aggregate through a self-organization process into a three-dimensional network of fibers. This network sucks up the oil molecules and swells into a gel with an enormous capacity. The researchers mixed different types of oil - ranging from crude oil to diesel, gasoline, and organic solvents - with water and added a few drops of the new gelator. This immediately formed a gel that separated from the water phase. The gel became so solid that it closed off the reaction flask like a cork. The flask could be inverted without any spillage of liquid. “In case of an oil spill, it would be relatively easy to collect the gel from the surface of the water,” says John. Simple distillation under vacuum is all that is needed to fully release oil from the gel. After separation, both the oil and the gelator are ready to be used again. “We are optimistic that our sugar-based gelators provide an approach for the development of new materials to combat oil slicks on water, says John.
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