Creating Aerogel from Paper Waste

Aerogels are porous, lightweight materials traditionally made from silica gels. They are synthesized by replacing the liquid within the gel with gas. Silica aerogels are usually transparent with low densities and low thermal conductivities.

The new process for creating green cellulose aerogel begins by adding NaOH/Urea to the waste sample, which then undergoes sanitation. It is then frozen for a day and thawed at room temperature. After that, it is immersed in industrial ethanol and soaked in DI water for a second day. Finally, the product is freeze dried for another 24 hours.

Coated with an organosilicon compound Trimethoxy-methylsilane (MTMS)—a free flowing liquid with carbon-silicon bonds—the aerogel can absorb oil up to 90 times its dry weight while repelling water. The result is an oil sorbent up to four times more effective than what’s in use today.

"Our fabrication process uses 70 per cent less energy, produces fewer polluting emissions into the air and water, as well as uses less dioxins in the chlorine bleaching process. It is also faster: the entire process only takes three days," explained Duong Hai Minh, assistant professor in the department of mechanical engineering.

Cellulose Aerogel Applications

In addition to hydrophobic aerogels, the NUS team made hydrophilic aerogels uncoated with MTMS to absorb polar fluids like water and alcohol. These could be used to create biodegradable diapers and sanitary wipes. By infusing the cellulose aerogel with a solution of metallic nanoparticles the researchers were also able to create magnetic thin films with weight capacities of 30 tons per square meter.

Replacing conventional sorbent materials with green cellulose aerogels could make oil cleanups faster and more effective. The biodegradability and high absorbency of the material makes it all the more attractive for this purpose.

"Their water repellent property allows them to be adaptable to both dry and rainy weather and their structure remains stable for about six months in tropical climate. Being extremely strong, they increase building strength. In addition, these aerogels are lightweight and slim, resulting in slimmer walls, thus increasing building space," said Duong.

Additional applications include coating materials for drug delivery and uses in medicine to plug wounds. Injecting compressed versions of the aerogel into the wound cavity can stop hemorrhages in 20 seconds or less.

The researchers have filed a patent for their invention in the US, China, India and Southeast Asia under the name Bronxculture Pte Ltd. Presently, Bronxculture’s main focus is to manufacture the cellulose aerogels for insulation for packaging and winter garments, as well as oil-absorption materials.

For more information, visit the NUS website.