With the recent release of the biopic disaster film Deepwater Horizon the potential environmental risks of offshore drilling rigs have been thrown back into the limelight.
The film is a dramatisation of the events surrounding the April 2010 disaster in the Gulf of Mexico, when an offshore drilling rig, Deepwater Horizon, exploded and created the worst oil spill recorded in the petroleum industry’s history.
Following the explosion and sinking of the rig, oil continued to flow for 87 days until it was capped on July 15, 2010, with the US Government estimating the total discharge at 4.9 million barrels – around 206 million gallons.
Eleven people went missing and were never found. After several failed efforts to contain the flow, the well was declared sealed on September 19, 2010. Reports in early 2012 indicated the well site was still leaking.
While much work will have gone into preventing accidents like Deepwater Horizon from ever happening again, there is also a big research effort into developing technology to clean up oil spills more effectively.
A super slick solution
Engineers are constantly trying to develop better ways of cleaning up the environment if an oil spill occurs.
Researchers at the A*STAR Institute of Bioengineering and Nanotechnology (IBN) in Singapore, are using nanoscience to turn an oil spill into a floating mass of brown jelly within minutes, which can then be scooped up.
Normally, oil spills can be cleaned up by using fresh, thick grease that can be set ablaze or contained by floating barriers for skimmers to scoop out. The slick can also be hardened, absorbed, dispersed, or slowly consumed by oil-grazing bacteria. However, IBN says all of these are “deficient on a large scale”, especially in rough waters.
According to IBN, organic molecules with special gelling abilities offer a cheap, simple and environmentally friendly alternative for cleaning up the mess. Chemist Yugen Zhang at IBN, has developed several molecules that can turn crude oil into jelly.
To create his ‘supergelators’, Zeng designed the molecules to “associate with each other” without forming physical bonds. When sprayed on contaminated seawater, the molecules immediately bundle into long fibres between 40 and 800 nanometers wide. These threads create a web that traps the interspersed oil in a giant blob that floats on the water’s surface.
The gunk can then be swiftly sieved out of the ocean. Valuable crude oil can later be reclaimed using a common technique employed by petroleum refineries called fractional distillation.
Zeng tested the supergelators on four types of crude oil with different densities, viscosities and sulfur levels in a small round dish. “The supergelators solidified both freshly spilled crude oil and highly weathered crude oil 37 to 60 times their own weight,” says Zeng.
The materials used to produce these organic molecules are cheap and non toxic, which make them a commercially viable solution for managing accidents out at sea. Zeng hopes to work with industrial partners to test the nanomolecules on a much larger scale.
Sponge it up
Meanwhile, researchers at Purdue University in Indiana, USA, have developed a material that is easy to manufacture and commercially available, which they claim offers an affordable way to continuously remove oils and other pollutants from water.
The material is shown to be “superhydrophobic and superoleophilic”, meaning it rejects water while absorbing oils. It is made using melamine sponges, an ultra-low-weight, porous material found in various products including household cleaning pads and insulation materials.
The researchers modified the melamine sponge by dipping it into a solution containing a small amount of silicone rubber called PDMS and the solvent hexane, resulting in an extremely thin coating that repels water while allowing oil to be absorbed into the sponge.
According to Suresh V. Garimella, Purdue University's executive vice president for research and partnerships, the sponges can be made using an inexpensive, one-step process to coat the melamine sponges, and the material can be reused many times. "We believe this can be readily adopted for the cleanup of oil spills and industrial chemical leaks,” adds Garimella.
The sponge can be dragged over the surface of the water to absorb a contaminant or apply suction to continuously draw out oil and leave water behind.
Findings show the sponge material has an absorption capacity of 45-75 times its own weight, which is comparable to other more “exotic materials” under development that can be expensive and difficult to scale up, such as carbon nanotubes and graphene, says IBN.
"Oil spillage from industrial sources has caused severe damage to the environment," says postdoctoral research associate at Purdue, Xuemei Chen.
"The conventional methods used to clean up oils and organic pollutants are slow and energy-intensive. The development of absorbent materials with high selectivity for oils is of great ecological importance for removing pollutants from contaminated water sources."
The researchers have filed a provisional U.S. patent application for the technology.
Caught in a trap
Ohio State researchers have also been working on novel solutions in this field. One promising idea is a stainless steel mesh that water can pass through but oil cannot. This is thanks to a nearly invisible oil-repelling coating on its surface.
In tests, researchers mixed water with oil and poured the mixture onto the mesh. The water filtered through the mesh to land in a beaker below. The oil collected on top of the mesh, and rolled off easily into a separate beaker when the mesh was tilted.
The work was partly inspired by lotus leaves, whose bumpy surfaces naturally repel water but not oil. To create a coating that did the opposite, Bharat Bhushan, professor of mechanical engineering at Ohio Sate, and postdoctoral researcher Philip Brown chose to cover a bumpy surface with a polymer embedded with molecules of surfactant—the stuff that gives cleaning power to soap and detergent.
They sprayed a fine dusting of silica nanoparticles onto the stainless steel mesh to create a randomly bumpy surface and layered the polymer and surfactant on top.
“If you scale this up, you could potentially catch an oil spill with a net,” says Bhushan.
Let’s hope that these kind of promising technologies receive enough support and funding to reach commercialisation in the hope that, if a large-scale event like Horizon Deepwater was ever to happen again, that they can prevent as much environmental damage from oil spills as possible.