New nanocellulose sponges are the newest weapon to combat oil pollution
Swiss Empa (Swiss Federal Laboratories for Materials Science & Technology, belonging to ETH, the Swiss Federal Institute of Technology) has developed a new, absorbable material in the form of a silylated nanocellulose sponge to absorb oil spills at large
It seems to be the most environmentally-friendly way of cleaning up nature after anoil spill accident by absorbing and recover the floating film of oil.
Empa researchers Tanja Zimmermann and Philippe Tingaut, in collaboration with Giles Sèbe from the University of Bordeau, have now succeeded in developing a highly absorbent material which separates the oil film from water and can then easily be recovered by the “silyated” nanocellulose sponge.
In laboratory tests the sponges absorbed up to 50 times their own weight of mineral or engine oil. They kept their shape to such an extent that they could we removed with pincers from the water. The next step is to fine tune the sponges so that they can be used not only on a laboratory scale, but also in real disasters. To this end, a partner from industry is currently is sought for and there is a row of interest created.
Nanofibrillated Cellulose (NFC), the basic material for the sponges, is extracted from cellulose-containing materials like wood pulp, agricultural by-products (such as straw) or waste materials (such as recycled paper) by adding water and pressing the aqueous pulp through several narrow nozzles at high pressure. This results in a suspension with gel-like properties containing long and interconnected cellulose nanofibres.
When the water from the gel is replaced with air by freeze-drying, a nanocellulose spong is formed which absorbs both water and oil. The pristine material sinks in water and is thus not useful for the envisaged purpose. The Empa researchers have succeeded in modifying the chemical propterties of the nanocellulose in just one process step and by mixing witha reactive alkoxysilane molecule in the gel before freeze-drying. The nanocellulose sponge loses its hydrophilic properties, and is no longer suffused with water and only binds with oily substances.
In the laboratory, the “silylated” nanocellulose sponge absorbed test substances, like engine oil, silicone oil, ethanol, acetone or chloroform within seconds. Nanofibrillated cellulose sponge, therefore, reconciles several desirable properties. It is absorbent, floats reliably on water, even when fully saturated and is biodegradable.