Researchers have developed a sustainable and economical way to recover oil from ultra-cold industrial wastewater and oil spills.
Scientists from Imperial College London and the University of Toronto have designed a sponge that can remove hard-to-recover oil from Artic waters. Their research builds on previously developed sponge technology to target specific challenges with recovering oil from ultra-cold water.
The findings, published in Science Advances, present an economical and sustainable method of oil recovery which will benefit the environment whilst presenting a cost-effective solution to industry.
Oil contamination in the Arctic
Researchers have developed a special coating for commercially available sponges which can recover oil droplets from water as cold as 5 degrees celsius. Oil is more difficult to remove from ultra-cold water because it becomes viscous at low temperatures, reducing its flow and making it harder to collect.
Oil contamination in Arctic waters is a significant issue, with over one trillion liters of oil sands tailings, a waste by-product of oil extraction, marine and Arctic oil spills awaiting clean up.
Traditional technologies used to recover oil from such sites are either energy intensive, costly, or ineffective when faced with micrometer size oil droplets. Some can even risk causing further environmental damage, such as those that reheat the oil before collection, which can cause it to dissolve or evaporate.
The technology designed by Imperial and U of T addresses these challenges by harnessing the properties of cold-temperature oil to create a low-energy and cost-efficient solution. Not only will this benefit the environment and help to protect our natural resources, it offers an economically viable solution for industry which is vital to ensuring widespread uptake.
Mutual attraction
The team at Imperial engineered a special coating for commercially available sponges based on the behavior of oil droplets in cold water.
When oil is below 38 degree celsius, it begins to crystallize and becomes sticky at the edges. Lead author Dr. Pavani Cherukupally used this knowledge to design a paraffin-like sponge coating with the same chemical structure as oil that could create a mutual attraction between the two surfaces.
The sponge can be rinsed with a non-toxic solvent which displaces the sticky oil droplets and allows them to be collected, enabling both the sponge and the oil to be reused. The process is known as wax-wetting, where one fluid is used to displace another. In this case, the solvent, known as heptol, is used to displace the oil droplets.
Once the optimum wax-wetting characteristics had been established, a team of U of T Chemists synthesized the nanocoating which made it functional and ready to use on a larger scale.
Rigorous testing showed that the engineered sponge can adsorb oil droplets from water ranging between 5 and 40 degrees Celsius and remove 90-99% of contaminants within two and a half hours. The recovered oil can be used again by industry, providing an economic benefit to organizations, and the sponge can be reused ten times with consistent results.
Next steps
This method of oil recovery poses significant benefits to both industry and the environment. It has a high success rate for removing oil from ultra-cold water and requires no additional energy input as it uses the material properties of the sponge and oil to generate results.
Lead author Dr. Pavani Cherukapally, Imperial College London, explained: “We’ve developed an energy efficient way of reclaiming crude oil which has ecological benefits for the environment and is economically beneficial to industry.
“Our work is significant because it targets a specific issue, oil crystallization at low temperatures, and addresses it from a materials perspective.”
Principle Investigator Professor Daryl Williams added: “If we continue treating the environment as we have been for decades, clean water will become increasingly scarce. As such an important global resource, it is vital that society and industry has access to innovative, low-cost methods for water clean-up like those we report in our study.
“Our technology heralds a new approach for global remediation which we hope will be widely utilized before it is too late.”
Next the team will explore how the sponge can be used to collect and range of oils, which each have a different composition and will behave differently at low temperatures. They are confident that their sponge technology can be adapted to meet these different needs across many different environmental conditions.
Oil-catching sponge could soak up residue from offshore drilling
More information:
P. Cherukupally et al. Wax-wetting sponges for oil droplets recovery from frigid waters, Science Advances (2021). DOI: 10.1126/sciadv.abc7926
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Imperial College London
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Modified sponge could recover oil contaminants from Arctic waters (2021, March 11)
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