Oil spills have become an environmental problem due to the growth of offshore oil exploration, production, and transportation. There are several methods that have been used to clean up oil spills such as chemical dispersants, water skimming, and using absorbent materials. Although skimming is the most common method for cleaning large spills, this method is time-consuming, expensive, and poorly separates oil and water. Chemical dispersants can be used to break up oil slicks into droplets that can be easily dissipated in water, but the mixture of oil and dispersants can be toxic and damage marine ecosystems. Thus, the use of oil sorbents can be an effective method to ease oil collection, and sorbents have a high capacity for removing oil from a targeted site.
The present invention provides a simple, cost-effective method to fabricate robust superhydrophobic sponges with excellent oil sorption capacity and exceptional recyclability. The fabrication method creates superhydrophobic sponges by chemically modifying the surface of sponge skeletons via a solution-immersion process. This process comprises the silanization of commercially available sponges, such as melamine, by reacting secondary amine groups on the surface of the sponge skeletons with alkylsilane compounds. This will inherently form monolayers that can self-assemble on the surface of sponge skeletons, resulting in the chemical modification of the surface properties of the sponges. The resulting modified sponge is stable, and its properties can be easily tuned from being hydrophilic to superhydrophobic. The chemical bonds between surface and sponge skeleton remain unaffected during oil absorption-squeezing, making them reusable for repetitive cycles.
The fabrication approach is fast, simple, inexpensive, widely applicable, and scalable in comparison to previous processes. The superhydrophobic sponge may have a sorption capacity greater than 160 times its own weight, and is recyclable with retention for more than 90% after 1,000 cycles. The coating is not easily detached from the sponge skeleton. Moreover, the invention can absorb a range of organic solvents and oils including acetone, butanol, toluene, THF, DMF, chloroform, diesel, motor oil, machine oil, biodiesel, and mineral oil.
Superhydrophobic sponges can be used for oil spill and organic solvent cleanup applications. Additionally, this approach can be applied to other kinds of sponges used for general cleaning, including melamine sponges and cellulose sponges.