Scientists have turned waste cooking oil into an oil spill fighting sponge
Scientists from Australia’s Flinders University have created a new tool to aid the clean-up of oil spills.
The team, headed by senior lecturer in synthetic chemistry Dr Justin Chalker, has developed a rubber polymer from recycled cooking oil and sulphur that can soak up oil. Salt is added to the mixture to make the substance porous before being washed out.
The sponge is able to absorb two to three times its own mass in oil or diesel. In a statement on the study Dr Chalker described the polymer “a new class of oil sorbent that is low-cost, scalable and enables the efficient removal and recovery of oil from water.”
“Our primary motivation at the outset of the project was to identify new ways to convert waste into useful polymers,” Dr Chalker told InnovOil. “It was only after we made the material that we asked how it might be useful. It turns out that this rubber (because it has a lot of sulphur – 50% by mass) binds to diverse forms of mercury pollution.”
The sponge-like chemical is hydrophobic but oleophilic, and when bound to oil creates a floating gel that can be simply scooped out of the water.
Dr Chalker explained that “the polymer can be added in powdered form directly to an oil spill. The oil absorbs upon contact and aggregates to form a gel.” The team hopes that this method could be a practical solution to combat small, local spills where it would be possible to recover the oil-polymer aggregate.
“In the open sea, this might be a challenge,” Chalker conceded. “So the second way to deploy the polymer is to pack it into a filter. The oil-water mixture is pumped through the filter; the oil binds to the polymer and is retained in the filter and the purified water passes through the filter and is discharged. The oil can be recovered by compressing the oil-polymer aggregate with a piston. The oil flows out and can be recovered and the filter can be re-used.”
It may also provide a home for other waste products, given that excess or waste sulphur is stockpiled around the globe and could easily be sourced as feedstock.
The sponge could be commercially available by the end of 2018. However, this is dependent on its success in field trials, as well as support from industry partners. Currently, the sponge is being used in Colombia to remove mercury from rivers contaminated during gold mining.
This substance is similar to Argonne National Laboratory’s Oleo Sponge, which won three R&D 100 awards in 2017, although there are some notable differences. Because Flinders’ polymer can be made from cheap and readily available waste cooking oil, it may be more easily produced by economies with less developed infrastructure. It also reduces the requirements for pricey ingredients, and the need for expensive or difficult to access equipment.
These areas are often the hardest hit by oil spills, where poor or ageing infrastructure, or weak and poorly enforced legislation, increases the chance of spills. This is made worse by difficulties in accessing the equipment needed to clean up the oil.
“The polymer is effective at absorbing various types of motor oils, diesel fuel and crude oils. Our lab testing has demonstrated the polymer is well-suited for cleaning up small spills and we are currently gearing up for larger-scale field testing in ports and coastal environments,” Dr Chalker said.
Furthermore, these oil spills are often smaller and more frequent, making cheap, easily and flexibly produced chemicals an ideal option for clean-up jobs. Since these places often have a high concentration of oil and gas production, it also means that sulphur, a key ingredient in creating the sponge, is readily available.
Dr Chalker told InnovOil “the process requires a skilled chemist or engineer to operate on a larger scale. The process also occurs at around 160-180 ºC, so it does require energy input.
“Over the next year, we are working with engineers to develop a continuous production method using an extruder. Additionally, we are also exploring gas injection to make the polymer foam, rather than rely on a porogen that has to be removed with a water wash.
“With these reactors in place, we anticipate that we will be able to make 10s or 100s of kg per hour, with the added benefit of economies of scale. And up-scaling is a priority for our team because tackling oil spill pollution is a large-scale problem that will require tonnes of our polymer,” he added.