Wood-based sponge hates water but loves oil
Removing oil spills from bodies of water is a difficult business, with various approaches having met with mixed results over the years. Scientists from the Chinese Academy of Forestry believe they may be onto something, however, in the form of a reusable "wooden" sponge that absorbs oil while leaving water behind.
Led by Xiaoqing Wang, the researchers started with ordinary balsa wood, then chemically treated it to remove the lignin and hemicellulose from its cell walls. This left a highly-porous cellulose skeleton behind, which was subsequently freeze-dried. A silylation process was then used to grow a coating of a hydrophobic (water-repelling) polymer known as polysiloxane within that skeleton.
The resulting tough-yet-compressible sponge proved to be very effective at absorbing oil from a water sample's surface, while not absorbing any of the water itself – depending on the type of oil being tested, the sponge could absorb 16 to 41 times its own weight. It could then be squeezed out and used to soak up more oil from the water, going for at least 10 such cycles before showing any loss in performance.
Additionally, once the sponge is no longer usable, it will biodegrade upon being discarded. According to the Academy, other groups' past efforts at oil-absorbing sponges have been made from non-degradable and nonrenewable materials, plus they've been difficult to manufacture, and haven't stood up well to repeated uses.
That being said, Switzerland's Empa research group has also successfully developed a sponge made from wood waste, that absorbs oil but not water.
A paper on the latest research was recently published in the journal ACS Nano.