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Biological Chemistry

Sugar Derivative Solidifies Oil

Materials Chemistry: Gelation process could turn spilled oil into skimmable fat for easy cleanup

by Elizabeth K. Wilson
July 26, 2010 | A version of this story appeared in Volume 88, Issue 30

Protected form of Man-8
Protected form of Man-8

A new sugar-based compound that selectively converts oils into a gel could serve as a new tool for cleaning up oil spills, its inventors say.

To mitigate oil spills such as the current one in the Gulf of Mexico, cleanup crews typically reach for dispersants—mixtures of chemicals that cause the oil to collect in tiny droplets. If successful, a gelling process would represent an entirely new strategy that could have advantages over the use of dispersants, which have raised toxicity concerns.

In a one-step process aided by enzymes, materials chemist George John of the City College of New York and chemical engineer Srini Raghavan of the University of Maryland and their colleagues have synthesized amphiphilic sugar molecules that bind with hydrocarbon oils and form a gel, even when the oil is mixed with water (Angew. Chem. Int. Ed., DOI:10.1002/anie.201002095).

The group tested the gelator in mixtures of water and diesel fuel. Within five minutes, the oil becomes a congealed mass that floats on top of the water and can be lifted out with a spoon.

The group synthesized several gelator variants, dialkanoate derivatives of mannitol and sorbitol, before settling on one mannitol-based molecule, dubbed "Man-8." In addition to being nontoxic, Man-8 is relatively cheap to produce and works at room temperature.

Credit: Courtesy of George John/City College of New York
This movie demonstrates how a gelator separates diesel fuel from water to form a gel.

Dean Scott, spokesman for BP, the oil company whose well has been leaking millions of gallons of oil into the Gulf of Mexico, declined to comment on the method.

Santanu Bhattacharya, an organic chemist at the Indian Institute of Science, in Bangalore, notes that Man-8 belongs to "a rather elusive class of molecules" known as phase-selective gelators, which were first discovered in his lab in 2001. Since then, he adds, fewer than 10 such gelators have been discovered. In addition, these gelators require many more steps to make than Man-8, and triggering their gelation requires heat or ultrasonic vibration.

John's group has already filed a patent application on their process. But scaling up the process from the gram-scale quantities they've synthesized in the laboratory to quantities that could be used in an oceanic setting will take some work, John notes. He says developers would need to devise ways to scale up the enzymatic process and would need to perform large-scale spraying tests.

Bhattacharya also notes that the recovery of the gelator, which is more valuable than the oil itself, will also need to be considered.

John's group is now at work on gelators with improved and more general properties.



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