Recovering marine oil-spills may soon become simple, efficient and cost-effective thanks to a compound (gelator) developed by researchers at the Indian Institute of Science Education and Research (IISER) Thiruvananthapuram.
A team led by Dr. Kana M. Sureshan from the School of Chemistry used glucose as a starting material and through several chemical reactions produced compounds (gelators) that selectively congeals oil, including crude oil, from an oil-water mixture. Unlike other alternatives, the gelators, which are in a powder form, can be easily applied over oil-water mixture and does not cause any environmental damage. The results based on laboratory studies were published recently in the journal Angewandte Chemie.
Currently, oil spillage is either burnt or confined using booms so that with time the oil slowly disintegrates into tiny oil droplets and gets degraded by bacteria. “But our gelator can recover oil from oil-water mixture. Through simple distillation the oil can then be separated from the gelator and the gelator can be reused several times (refined oil),” says Dr. Sureshan. “But in the case of crude oil the gelator can’t be recycled as the gelator is a solid and cannot be separated from tar and other solid remains that form after distillation. So our aim is to make the gelator cheaper and more efficient.”
The gelator molecule is partly hydrophobic and partly hydrophilic. While the hydrophilic part helps in self-assembling to form gelator fibres, the hydrophobic part is responsible for its diffusion into the oil layer. The better the self-assembly (which is primarily through hydrogen bonding) the better the fibre strength and gelation.
“To achieve better diffusion of the molecule into the oil phase and enhance the oil recovery we increased the hydrophobicity. This was done by adding an aromatic/alkyl group at some part (anomeric position) of the molecule,” says Dr. Sureshan.
“Adding the aromatic/alkyl group also makes the self-assembly stronger. The compound where the aromatic group was introduced had a stronger self-assembly and better ability to congeal more crude oil even when lesser amount of the compound was used,” says Amol M. Vibhute from the School of Chemistry, IISER Thiruvananthapuram and the first author of the paper.
Since the outer part of the fibre is hydrophobic, oil tends to gets into the spongy network made of fibres. Once inside the fibre network, oil loses fluidity and becomes a gel. As the self-assembly is strong, the gel maintains its structure and rigidity even under pressure.
When the researchers applied the compound on a benzene-water mixture and diesel-water mixture, it was able to congeal all the benzene and diesel within a short span of time. “The gel was strong enough to be scooped with a spatula,” says Dr. Sureshan. In the case crude oil it took a longer time for the compound to form a gel that was strong enough to be scooped off. “The crude oil is a mixture of several low- and high-boiling and polar and non-polar fractions. So the efficiency to form a gel is less in the case of crude oil,” Dr. Sureshan explains.
“We are trying to improve the efficiency of the compound in terms of better absorption capacity and use in real marine oil-spill situations. We will be testing the compound’s ability to form oil gels applied on ocean surface by artificially creating a marine oil-spill,” Dr. Sureshan says.