Floating cellulose gel cleans up oil spills

A NEW type of cellulose composite material which can turn spilled oil into a rigid floating gel that can be scooped out of the water has been developed by chemists in India.

Kana Suresan and Annamalai Prathap from the Indian Institute of Science, Education and Research (IISER) Thiruvananthapuram in Kerala sought to find an alternative to skimming or booming for oil spills in the sea. Such measures ore often ineffective due to how quickly oil can spread over a large area, or because of rapid emulsification of the oil in rougher waters. Recovering the oil in solid form would be much easier, and the researchers say that their new composite could provide a simple, cheap and environmentally benign solution.

The composite material Suresan and Prathap created is based on cellulose, which is cheap and readily available. They took cellulose pulp and impregnated it with an oleogelator derived from the sugar mannitol - 1,2:5,6-di-O-cyclohexylidene-mannitol. The oleogelator is phase selective, meaning that it can selectively congeal only the oil from a biphasic mixture of oil and water.

The researchers explain that the molecules of the oleogelator mask the hydroxyl groups of the cellulose through hydrogen bonding. This exposes only the hydrophobic parts of the cellulose fibres, making the material reject water and bind only to oil. When it comes into contact with the oil, the gelator molecules self-assemble into a three-dimensional fibre network throughout the material, trapping the oil which then becomes a rigid gel. Even when fully saturated with oil, the cellulose material floats on the surface of the water for easy removal.

The gelation process takes around two hours. Oil can be recovered from the material either through a physical squeezing process, or through distillation, allowing recycling of the material.

Angewandte Chemie doi.org/b9wc